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Evaporation rate of water in hydrophobic confinement
Sharma, Sumit; Debenedetti, Pablo G.
The drying of hydrophobic cavities is believed to play an important role in biophysical phenomena such as the folding of globular proteins, the opening and closing of ligand-gated ion channels, and ligand binding to hydrophobic pockets. We use forward flux sampling, a molecular simulation technique, to compute the rate of capillary evaporation of water confined between two hydrophobic surfaces separated by nanoscopic gaps, as a function of gap, surface size, and temperature. Over the range of conditions investigated (gaps between 9 and 14Ā? and surface areas between 1 and 9Ānm2), the free energy barrier to evaporation scales linearly with the gap between hydrophobic surfaces, suggesting that line tension makes the predominant contribution to the free energy barrier. The exponential dependence of the evaporation rate on the gap between confining surfaces causes a 10 order-of-magnitude decrease in the rate when the gap increases from 9 to 14Ā?. The computed free energy barriers are of the order of 50kT and are predominantly enthalpic. Evaporation rates per unit area are found to be two orders of magnitude faster in confinement by the larger (9Ānm2) than by the smaller (1Ānm2) surfaces considered here, at otherwise identical conditions. We show that this rate enhancement is a consequence of the dependence of hydrophobic hydration on the size of solvated objects. For sufficiently large surfaces, the critical nucleus for the evaporation process is a gap-spanning vapor tube. PMID:22392972
Urban evaporation rates for water-permeable pavements.
Starke, P; G÷bel, P; Coldewey, W G
In urban areas the natural water balance is disturbed. Infiltration and evaporation are reduced, resulting in a high surface runoff and a typical city climate, which can lead to floods and damages. Water-permeable pavements have a high infiltration rate that reduces surface runoff by increasing the groundwater recharge. The high water retention capacity of the street body of up to 51 l/m(2) and its connection via pores to the surface lead to higher evaporation rates than impermeable surfaces. A comparison of these two kinds of pavements shows a 16% increase in evaporation levels of water-permeable pavements. Furthermore, the evaporation from impermeable pavements is linked directly to rain events due to fast-drying surfaces. Water-permeable pavements show a more evenly distributed evaporation after a rain event. Cooling effects by evaporative heat loss can improve the city climate even several days after rain events. On a large scale use, uncomfortable weather like sultriness or dry heat can be prevented and the urban water balance can be attenuated towards the natural. PMID:20818060
Rate of Water Evaporation in Texas.Ā
Karper, R. E. (Robert Earl)
. Av. rel. humidity Wind run, miles Winter Haven : 18 7 7 5 63 32 47 3629 3.346 i -94 76.8 52.8 64.8 80.4 4343 Evaporation, inches Precipitation, inches 5.520 1.11 80.1 57.2 68.7 75.6 5558 2.252 .82 2 1 1.824 11 1 1.16 4....560 7.341 8.897 8.152 9.196 8.725 8.469 6.825 7.965 5.280 7.241 5.468 7.435 4.221 5.526 5.011 5.991 4.454 5.797 6.044 5.671 6.167 5.684 '7.377 4.801 5.052 6.216 4.086 2.912 3.891 5.557 4.850 13.820 3.804 3.956 4.173 6...
WilsonBull., 105(4), 1993, pp. 645-656 METABOLIC RATE AND EVAPORATIVE WATER
to dissipate heat via evaporative cooling may partially explain its tendency to use habitats featuring coolWilsonBull., 105(4), 1993, pp. 645-656 METABOLIC RATE AND EVAPORATIVE WATER LOSS OF MEXICAN SPOTTED of oxygen consumption and evaporative water loss (EWL) of Mexican Spotted (Strix occidentalislucida
Effect of Thickness of a Water Repellent Soil Layer on Soil Evaporation Rate
NASA Astrophysics Data System (ADS)
Ahn, S.; Im, S.; Doerr, S.
A water repellent soil layer overlying wettable soil is known to affect soil evaporation. This effect can be beneficial for water conservation in areas where water is scarce. Little is known, however, about the effect of the thickness of the water repellent layer. The thickness of this layer can vary widely, and particularly after wildfire, with the soil temperature reached and the duration of the fire. This study was conducted to investigate the effect of thickness of a top layer of water repellent soil on soil evaporation rate. In order to isolate the thickness from other possible factors, fully wettable standard sand (300~600 microns) was used. Extreme water repellency (WDPT > 24 hours) was generated by 'baking' the sand mixed with oven-dried pine needles (fresh needles of Pinus densiflora) at the mass ratio of 1:13 (needle:soil) at 185░C for 18 hours. The thicknesses of water repellent layers were 1, 2, 3 and 7 cm on top of wettable soil. Fully wettable soil columns were prepared as a control. Soil columns (8 cm diameter, 10 cm height) were covered with nylon mesh. Tap water (50 ml, saturating 3 cm of a soil column) was injected with hypoderm syringes from three different directions at the bottom level. The injection holes were sealed with hot-melt adhesive immediately after injection. The rate of soil evaporation through the soil surface was measured by weight change under isothermal condition of 40░C. Five replications were made for each. A trend of negative correlation between the thickness of water repellent top layer and soil evaporation rate is discussed in this contribution.
AaSraAcr. -We measured rates of oxygen consumption and evaporative water loss (EWL) of Mexican Spotted (Strix occidentalis lucida) and Great Homed (Bubo virginianus) owls in Arizona. Basal metabolic rate averaged 0.84 ccO,gl .h-' for the Spotted Owl and 0.59 cc0, .g- I h- ' for the Great Homed Owl, with apparent thermoneutral zones extending from 17.0-25.2\\
Predictions of evaporative-loss rates of solutes in stagnant and turbulent waters in relation to rates of reference materials
Chiou, C.T.; Kohnert, R.L.; Freed, V.H.; Tonkyn, R.G.
A previously published kinetic model for evaporative rates of substances into air leads to the estimation of the dependence of solute-transfer coefficients on turbulence applied to the system. The ratios of the transfer coefficients of all solutes become insensitive to air turbulence and to water mixing either when they have comparable Henry's law constants or when their Henry's law constants are sufficiently low, but not otherwise. Confirming data are presented and methods for simplifying the estimation of transfer coefficients are discussed.
An experimental investigation on the effects of surface gravity waves on the water evaporation rate in different air flow regimes
NASA Astrophysics Data System (ADS)
Jodat, Amin; Moghiman, Mohammad; Shirkhani, Golshad
Estimating rate of evaporation from undisturbed water surfaces to moving and quiet air has been the topic a vast number of research activities. The obvious presence of various shapes of gravity waves on the water body surfaces was the motivation of this experimental investigation. In this investigation experimental measurements have been done to quantify evaporation rate from wavy water surfaces in free, mixed and forced convection regimes. The effects of a wide range of surface gravity waves from low steepness, round shaped crest with slow celerity, to steep and very slight spilling crest waves, on the water evaporation rate have been investigated. A wide range of was achieved by applying different air flow velocities on a large heated wave flume equipped with a wind tunnel. Results reveal that wave motion on the water surface increase the rate of evaporation for all air flow regimes. For free convection, due to the effect of wave motion for pumping rotational airflows at the wave troughs and the dominant effect of natural convection for the air flow advection, the maximum evaporation increment percentage from wavy water surface is about 70 %. For mixed and forced convection, water evaporation rate increment is more sensitive to the air flow velocity for the appearance of very slight spilling on the steep wave crests and the leeward air flow structures.
Evaporation Rate of Water as a Function of a Magnetic Field and Field Gradient
Guo, Yun-Zhu; Yin, Da-Chuan; Cao, Hui-Ling; Shi, Jian-Yu; Zhang, Chen-Yan; Liu, Yong-Ming; Huang, Huan-Huan; Liu, Yue; Wang, Yan; Guo, Wei-Hong; Qian, Ai-Rong; Shang, Peng
The effect of magnetic fields on water is still a highly controversial topic despite the vast amount of research devoted to this topic in past decades. Enhanced water evaporation in a magnetic field, however, is less disputed. The underlying mechanism for this phenomenon has been investigated in previous studies. In this paper, we present an investigation of the evaporation of water in a large gradient magnetic field. The evaporation of pure water at simulated gravity positions (0 gravity level (ab. g), 1 g, 1.56 g and 1.96 g) in a superconducting magnet was compared with that in the absence of the magnetic field. The results showed that the evaporation of water was indeed faster in the magnetic field than in the absence of the magnetic field. Furthermore, the amount of water evaporation differed depending on the position of the sample within the magnetic field. In particular, the evaporation at 0 g was clearly faster than that at other positions. The results are discussed from the point of view of the evaporation surface area of the water/air interface and the convection induced by the magnetization force due to the difference in the magnetic susceptibility of water vapor and the surrounding air. PMID:23443127
Differences in metabolic rate and evaporative water loss associated with sexual dimorphism in thynnine wasps.
Tomlinson, Sean; Phillips, Ryan D
Species with sexual dimorphism provide powerful study systems for understanding adaptation to different lifestyles as it removes the potentially confounding effects of phylogeny. Thynnine wasps have a stark sexual dimorphism where males fly patrols in search of the flightless, predominantly fossorial females with which to mate. Using flow-through respirometry, we tested the prediction that the highly active males of the thynnine wasp Zaspilothynnus nigripes would have high metabolic rates (VCO2) relative to females. Further, the females, which spend more time underground, were predicted to exhibit lower evaporative water loss (EWL) than males. Metabolic rate of both sexes increased exponentially between 12 and 28░C. As predicted, males had higher mass-corrected VCO2 at identical temperatures than females. Alternatively, there were no differences in the EWL at identical temperatures between sexes, suggesting that experiencing the same environmental conditions during mating may favour similar EWL. Interestingly, Z. nigripes were estimated to undergo a decrease in metabolism at approximately 30░C. It is proposed that Z. nigripes persist despite sensitivity to high temperatures using a combination of behavioural strategies and emergence during a period of relatively benign climate that ameliorates the impacts of high temperatures. PMID:25935839
A Wind Tunnel Investigation of the Rate of Evaporation of Small Water Drops Falling at Terminal Velocity in Air
K. V. Beard; H. R. Pruppacher
An experimental study of the effect of ventilation on the rate of evaporation of small water drops falling at terminal velocity in air has been carried out in a wind tunnel where water drops could he suspended freely in the tunnel airstream. For Reynolds numbers NRe2 it was found that the Sherwood number NSh was linearly related to NRe1\\/2NI, in
NASA Technical Reports Server (NTRS)
Ungar, Eugene K.; Almlie, Jay C.
A water membrane evaporator (WME) has been conceived and tested as an alternative to the contamination-sensitive and corrosion-prone evaporators currently used for dissipating heat from space vehicles. The WME consists mainly of the following components: An outer stainless-steel screen that provides structural support for the components mentioned next; Inside and in contact with the stainless-steel screen, a hydrophobic membrane that is permeable to water vapor; Inside and in contact with the hydrophobic membrane, a hydrophilic membrane that transports the liquid feedwater to the inner surface of the hydrophobic membrane; Inside and in contact with the hydrophilic membrane, an annular array of tubes through which flows the spacecraft coolant carrying the heat to be dissipated; and An inner exclusion tube that limits the volume of feedwater in the WME. In operation, a pressurized feedwater reservoir is connected to the volume between the exclusion tube and the coolant tubes. Feedwater fills the volume, saturates the hydrophilic membrane, and is retained by the hydrophobic membrane. The outside of the WME is exposed to space vacuum. Heat from the spacecraft coolant is conducted through the tube walls and the water-saturated hydrophilic membrane to the liquid/vapor interface at the hydrophobic membrane, causing water to evaporate to space. Makeup water flows into the hydrophilic membrane through gaps between the coolant tubes.
Characteristics of Evaporation Rate of Water in Superheated Steam and Air
NASA Astrophysics Data System (ADS)
Nomura, Tomihiro; Nishimura, Nobuya; Hyodo, Tsutomu; Kashiwagi, Takao
Superheated steam drying and highly humid air drying have been applied in many industrial drying fields, such as drying of by-products of food industry. The most significant reason for this wide range of applications of superheated steam is that more water evaporates in this steam or highly humid air than in dry air above the inversion point temperature. As compared with these wide practical applications, fundamental research for determining controlled operating conditions or optimum design conditions for a superheated steam drying system have not been sufficiently performed. From this viewpoint, in experimenting for drying water in the closed circuit dryer, by changing drying variables, such as the mass velocity of heat transfer of the steam,the existance of the inversion point temperature was confirmed and the locus of the temperature were found. The behavior of the locus enables one to specify the drying variables for a controlled drying system. The difference of the evaporation phenomenon between superheated steam drying and conventional air drying was examined from the heat convection standpoint. The reliability of the data obtained from the experiment was too checked by comparing the data with another reported data.
Biology of Myotis thysanodes and M. lucifugus (Chiroptera: Vespertilionidae)ŚIII. Metabolism, heart rate, breathing rate, evaporative water loss and general energetics
Oxygen consumption (OC), weight specific oxygen consumption (VO). heart rate (HR). breathing rate (RR) and evaporative water loss (EWL) differ in adult female Mrotis th.wrnodes and M. ~uc~~uficgus and are significantly related to thermoregulatory performance (regulating or conforming) and to reproductive condition but not to body composttion. spleen or adrenal weights or age class. 2. Multiple regression equation models of
Sheet Membrane Spacesuit Water Membrane Evaporator
NASA Technical Reports Server (NTRS)
Bue, Grant; Trevino, Luis; Zapata, Felipe; Dillion, Paul; Castillo, Juan; Vonau, Walter; Wilkes, Robert; Vogel, Matthew; Frodge, Curtis
A document describes a sheet membrane spacesuit water membrane evaporator (SWME), which allows for the use of one common water tank that can supply cooling water to the astronaut and to the evaporator. Test data showed that heat rejection performance dropped only 6 percent after being subjected to highly contaminated water. It also exhibited robustness with respect to freezing and Martian atmospheric simulation testing. Water was allowed to freeze in the water channels during testing that simulated a water loop failure and vapor backpressure valve failure. Upon closing the backpressure valve and energizing the pump, the ice eventually thawed and water began to flow with no apparent damage to the sheet membrane. The membrane evaporator also serves to de-gas the water loop from entrained gases, thereby eliminating the need for special degassing equipment such as is needed by the current spacesuit system. As water flows through the three annular water channels, water evaporates with the vapor flowing across the hydrophobic, porous sheet membrane to the vacuum side of the membrane. The rate at which water evaporates, and therefore, the rate at which the flowing water is cooled, is a function of the difference between the water saturation pressure on the water side of the membrane, and the pressure on the vacuum side of the membrane. The primary theory is that the hydrophobic sheet membrane retains water, but permits vapor pass-through when the vapor side pressure is less than the water saturation pressure. This results in evaporative cooling of the remaining water.
NSDL National Science Digital Library
James H. Kessler
This three-part activity consists of an activity that groups of learners develop themselves, a given procedure, and an optional demonstration. First, learners discuss examples of evaporation and then design and conduct their own test to find out whether heating water has an effect on the rate of evaporation. While waiting for their results, learners conduct another evaporation activity using single drops of water on 2 paper towels, one of which is heated. The optional demonstration compares the rate of evaporation of hot and cold water using a sensitive scale or balance. In each of these experiences with evaporation, learners will identify variables, consider how to best control them, and use their observations to conclude that heating water increases the rate of evaporation.
Rate of runaway evaporative cooling
Groep, J. van de; Straten, P. van der; Vogels, J. M. [Atom Optics and Ultrafast Dynamics, Utrecht University, P.O. Box 80, 000, NL-3508 TA Utrecht (Netherlands)
Evaporative cooling is a process that is essential in creating Bose-Einstein condensates in dilute atomic gasses. This process has often been simulated based on a model using a truncated Boltzmann distribution. This model assumes that the energy distribution up to the threshold energy can still be described by a Boltzmann distribution: it assumes detailed balance up to the threshold energy. However, the evolution of the distribution function in time is not taken into account. Here we solve the kinetic Boltzmann equation for a gas undergoing evaporative cooling in a harmonic and linear trap in order to determine the evolution of the energy distribution. The magnitude of the discrepancy with the truncated Boltzmannmodel is calculated by including a polynomial expansion of the distribution function. We find that up to 35% fewer particles are found in the high-energy tail of the distribution with respect to the truncated Boltzmann distribution and up to 15% more collisions are needed to reach quantum degeneracy. Supported by a detailed investigation of the particle loss rate at different energies, we conclude that the limited occupation of high-energy states during the evaporation process causes the lowering of the evaporation speed and efficiency.
Bennett, Albert F.
EVAPORATIVE WATER LOSS IN SCALELESS SNAKES ALBERTF. BENNETT*AND PAULLICHT Department of Zoology, University of California, Berkeley, CA 94720, U.S.A. (Received 19 June 1974) Abstract-1. Rates of water loss. Pulmocutaneous water loss of the scaleless animals was equal to or less than that of the controls at 20, 27
Computation of hypersonic flows with finite rate condensation and evaporation of water
NASA Technical Reports Server (NTRS)
Perrell, Eric R.; Candler, Graham V.; Erickson, Wayne D.; Wieting, Alan R.
A computer program for modelling 2D hypersonic flows of gases containing water vapor and liquid water droplets is presented. The effects of interphase mass, momentum and energy transfer are studied. Computations are compared with existing quasi-1D calculations on the nozzle of the NASA Langley Eight Foot High Temperature Tunnel, a hypersonic wind tunnel driven by combustion of natural gas in oxygen enriched air.
Water Evaporation Studies in Texas.Ā
Patterson, R. E. (Raleigh Elwood); Bloodgood, Dean W.; Smith, R. L.
Water Evaporation Studies In Texas Isogram showing the relationship and comparison of evapor- ation losses from free-water surfaces and rainfall in Texas. in cooperation with the TEXAS BOARD OF WATER ENGINEERS and the U. S. DEPARTMENT... Brewster 2,100 29' 05' 103' 25' Maravillus Brewster 1,760 29' 30' 102' 50' Presidio Presidio 2,594 29' 30' 104' 25' 11) In cooperation with Lower Colorado River Authority, Austin 12) In cooperation with Water Department, City of Wichita Falls. 13...
Evaporation over fresh and saline water surfaces
NASA Astrophysics Data System (ADS)
Abdelrady, Ahmed; Timmermans, Joris; Vekerdy, Zoltan
Evaporation over large water bodies has a crucial role in the global hydrological cycle. Evaporation occurs whenever there is a vapor pressure deficit between a water surface and the atmosphere, and the available energy is sufficient. Salinity affects the density and latent heat of vaporization of the water body, which reflects on the evaporation rate. Different models have been developed to estimate the evaporation process over water surfaces using earth observation data. Most of these models are concerned with the atmospheric parameters. However these models do not take into account the influence of salinity on the evaporation rate; they do not consider the difference in the energy needed for vaporization. For this purpose an energy balance model is required. Several energy balance models that calculate daily evapotranspiration exist, such as the surface energy balance system (SEBS). They estimate the heat fluxes by integration of satellite data and hydro-meteorological field data. SEBS has the advantage that it can be applied over a large scale because it incorporates the physical state of the surface and the aerodynamic resistances in the daily evapotranspiration estimation. Nevertheless this model has not used over water surfaces. The goal of this research is to adapt SEBS to estimate the daily evaporation over fresh and saline water bodies. In particular, 1) water heat flux and roughness of momentum and heat transfer estimation need to be updated, 2) upscaling to daily evaporation needs to be investigated and finally 3) integration of the salinity factor to estimate the evaporation over saline water needs to be performed. Eddy covariance measurements over the Ijsselmeer Lake (The Netherlands) were used to estimate the roughness of momentum and heat transfer at respectively 0.0002 and 0.0001 m. Application of these values over Tana Lake (freshwater), in Ethiopia showed latent heat to be in a good agreement with the measurements, with RMSE of 35.5 Wm-2and rRMSE of 4.7 %. Afterwards the validity of salinity adapted model was tested over different study areas using ECMWF data. It was found that for the original SEBS model and salinity-adapted model over Great Salt Lake, the RMSE were 0.62 and 0.24 mm respectively and the rRMSE 19% and 24%. The evaporation reduction of the Great Salt Lake and the oceans are 27% and 1 %, respectively. In conclusion, SEBS model is adapted to calculate the daily evaporation over fresh water and salt water by integration the salinity factor in the model.
Evaporation from the free water surface of a flooded forest
NASA Astrophysics Data System (ADS)
Newman, A.; Keim, R.; Hiscox, A.
Controls on evaporation rates from the free water surface of flooded forests have received little attention despite being an important component of the water balance in wetlands. In flooded forests, the tree canopy reduces solar radiation and turbulent exchange, so evaporation rates are lower than from an open water body. We measured evaporation from the free water surface in a flooded cypress/tupelo forest in southern Louisiana, USA, using both Bowen-ratio energy balance and eddy covariance methods. We compare results, which to our knowledge comprise the first experimental data set of evaporation rates in a flooded forest, to rates predicted by a simple empirical model.
Thermocapillary transport of energy during water evaporation.
Duan, Fei; Badam, V K; Durst, F; Ward, C A
When evaporation occurs at a spherical water-vapor interface maintained at the circular mouth of a small funnel, studies of the energy transport have indicated that thermal conduction alone does not provide enough energy to evaporate the liquid at the observed rate. If the Gibbs model of the interface is adopted and the "surface-thermal capacity" is assigned a value of 30.6+/-0.8 kJ/(m2 K), then for evaporation experiments with the interfacial temperature in the range -10 degrees C< or =TLV< or =3.5 degrees C and Marangoni number (Ma) in the range 100
The Role of Hysteresis in Reducing Evaporation from Soils in Contact with a Water Table
Richard A. Schleusener; A. T. Corey
Evaporation studies were conducted on three soil types in contact with a water table. For conditions of high evaporativity or increased depth to the water table, it was found that evaporation from the soils was not always in proportion to the rate of evaporation from a free-water surface. Under some conditions there was an inverse relation between evaporation from the
Analytical solution for soil water redistribution during evaporation process.
Teng, Jidong; Yasufuku, Noriyuki; Liu, Qiang; Liu, Shiyu
Simulating the dynamics of soil water content and modeling soil water evaporation are critical for many environmental and agricultural strategies. The present study aims to develop an analytical solution to simulate soil water redistribution during the evaporation process. This analytical solution was derived utilizing an exponential function to describe the relation of hydraulic conductivity and water content on pressure head. The solution was obtained based on the initial condition of saturation and an exponential function to model the change of surface water content. Also, the evaporation experiments were conducted under a climate control apparatus to validate the theoretical development. Comparisons between the proposed analytical solution and experimental result are presented from the aspects of soil water redistribution, evaporative rate and cumulative evaporation. Their good agreement indicates that this analytical solution provides a reliable way to investigate the interaction of evaporation and soil water profile. PMID:24355839
Thermoelectric integrated membrane evaporation water recovery technology
NASA Technical Reports Server (NTRS)
Roebelen, G. J., Jr.; Winkler, H. E.; Dehner, G. F.
The recently developed Thermoelectric Integrated Membrane Evaporation Subsystem (TIMES) offers a highly competitive approach to water recovery from waste fluids for future on-orbit stations such as the Space Operations Center. Low power, compactness and gravity insensitive operation are featured in this vacuum distillation subsystem that combines a hollow fiber membrane evaporator with a thermoelectric heat pump. The hollow fiber elements provide positive liquid/gas phase control with no moving parts other than pumps and an accumulator, thus solving problems inherent in other reclamation subsystem designs. In an extensive test program, over 850 hours of operation were accumulated during which time high quality product water was recovered from both urine and wash water at an average steady state production rate of 2.2 pounds per hour.
Vegetation Cover Decreases Evaporative Water Loss in a Wetland Ecosystem
NASA Astrophysics Data System (ADS)
Wang, X.; Sternberg, L. O.; Miralles-Wilhelm, F. R.
Analysis of oxygen and hydrogen isotope ratios of water is a useful tool for quantitative measurements of water evaporation. Water molecules with the lighter isotopes, H216O, evaporate faster than H218O and DH16O, leaving the residual water enriched in D and 18O. Therefore, the greater the evaporation, the higher the ?18O and ?D values in the remaining water body. Here we used stable isotope analyses to study evaporative processes in the a wetland water conservation area (WCA-1, South Florida Water Management District) where the primary purpose is to conserve regional water resources. Evaporation is one of the major paths of water loss in WCA-1. We collected water from 50 sampling stations located in the 145,920 acres of WCA-1 area for the months of August, September, and November 2006 and January 2007. Water samples were analyzed for oxygen and hydrogen isotope ratios. The results confirm that the water in this area is enriched by evaporation since a plot of water ?D versus ?18O lies off the meteoric water line. However, the enrichment of 18O and D within WCA-1 is not homogeneous, with differences in ?18O values between stations of up to 2ē. We GIS mapped the ?18O values of water for the entire area and found the isotopic enrichment pattern is consistent through time. This result suggests that water at different locations in WCA-1 has different evaporation rates. Possible factors that contribute to this evaporation pattern are: distance to the peripheral canal discharge station, water depth, and vegetation coverage. To find out which is (are) the determining factor(s) affecting water evaporation of the area, we mapped ?18O values of water with elevation and vegetation type of WCA-1 and calculated average elevation and percentage of vegetation coverage of a 100m2 area around each sampling station. A multiple linear regression between ?18O values of water and average distance from the discharge gates, elevation, and percentage coverage indicate that the observed evaporation pattern is not caused by water depth. Distance from the discharge gates and percentage vegetation coverage are both significantly correlated with ?18O values of water. The effect of distance is related to the water turnover rate, i.e. the further the location is to a discharge station the greater the time the water at that location has been exposed to evaporation. In contrast, the higher the vegetation coverage the lower the loss of water through evaporation. In the future, we will determine if the effect of vegetation coverage in diminishing water loss by evaporation is annulled by the loss through transpiration.
Evaporative cooling of speleothem drip water
Cuthbert, M. O.; Rau, G. C.; Andersen, M. S.; Roshan, H.; Rutlidge, H.; Marjo, C. E.; Markowska, M.; Jex, C. N.; Graham, P. W.; Mariethoz, G.; Acworth, R. I.; Baker, A.
This study describes the first use of concurrent high-precision temperature and drip rate monitoring to explore what controls the temperature of speleothem forming drip water. Two contrasting sites, one with fast transient and one with slow constant dripping, in a temperate semi-arid location (Wellington, NSW, Australia), exhibit drip water temperatures which deviate significantly from the cave air temperature. We confirm the hypothesis that evaporative cooling is the dominant, but so far unattributed, control causing significant disequilibrium between drip water and host rock/air temperatures. The amount of cooling is dependent on the drip rate, relative humidity and ventilation. Our results have implications for the interpretation of temperature-sensitive, speleothem climate proxies such as ?18O, cave microecology and the use of heat as a tracer in karst. Understanding the processes controlling the temperature of speleothem-forming cave drip waters is vital for assessing the reliability of such deposits as archives of climate change. PMID:24895139
Evaporative cooling of speleothem drip water.
Cuthbert, M O; Rau, G C; Andersen, M S; Roshan, H; Rutlidge, H; Marjo, C E; Markowska, M; Jex, C N; Graham, P W; Mariethoz, G; Acworth, R I; Baker, A
This study describes the first use of concurrent high-precision temperature and drip rate monitoring to explore what controls the temperature of speleothem forming drip water. Two contrasting sites, one with fast transient and one with slow constant dripping, in a temperate semi-arid location (Wellington, NSW, Australia), exhibit drip water temperatures which deviate significantly from the cave air temperature. We confirm the hypothesis that evaporative cooling is the dominant, but so far unattributed, control causing significant disequilibrium between drip water and host rock/air temperatures. The amount of cooling is dependent on the drip rate, relative humidity and ventilation. Our results have implications for the interpretation of temperature-sensitive, speleothem climate proxies such as ?(18)O, cave microecology and the use of heat as a tracer in karst. Understanding the processes controlling the temperature of speleothem-forming cave drip waters is vital for assessing the reliability of such deposits as archives of climate change. PMID:24895139
Spatially Resolved Evaporative Patterns from Water
Ienna, Federico; Pollack, Gerald H
Unexpectedly distinct patterns in evaporation were observed over heated water. Although the patterns had chaotic aspects, they often showed geometric patterns. These patterns bore strong resemblance to the infrared emission patterns observable with a mid-infrared camera focused on the water surface. This similarity puts constraints on the mechanism of evaporation, and leads to a general hypothesis as to the nature of the evaporative process.
Molecular Dynamics Simulations of Water Evaporation
NASA Astrophysics Data System (ADS)
Wen, Chengyuan; Grest, Gary; Cheng, Shengfeng
The evaporation of water from the liquid/vapor interface is studied via large-scale molecular dynamics simulations for systems of more than a million atoms at 550K and 600K. The TIP4P-2005 water model whose liquid/vapor surface tension is in excellent agreement with experiments is used. Evaporative cooling at the interface is observed from temperature profiles determined from both translational and rotational kinetic energy. During evaporation, the density of water is slightly enhanced near the liquid-vapor interface. The velocity distribution of water molecules in the vapor phase during evaporation at various distances relative to the interface fit a Maxwell-Boltzmann distribution. While our results indicate an imbalance between evaporating and condensing water molecules, local thermal equilibrium is found to hold in addition to mechanical equilibrium. Department of Physics, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Evaporation rate of emulsion and oil-base emulsion pheromones
Technology Transfer Automated Retrieval System (TEKTRAN)
Knowledge of pheromone evaporation rate is critical to distribute pheromone containers effectively in the forest, orchard and field. There are several factors influencing the pheromone evaporation rate that include wind speed, container size and porosity, release area, temperature, humidity, pherom...
Black hole evaporation rates without spacetime.
Braunstein, Samuel L; Patra, Manas K
Verlinde recently suggested that gravity, inertia, and even spacetime may be emergent properties of an underlying thermodynamic theory. This vision was motivated in part by Jacobson's 1995 surprise result that the Einstein equations of gravity follow from the thermodynamic properties of event horizons. Taking a first tentative step in such a program, we derive the evaporation rate (or radiation spectrum) from black hole event horizons in a spacetime-free manner. Our result relies on a Hilbert space description of black hole evaporation, symmetries therein which follow from the inherent high dimensionality of black holes, global conservation of the no-hair quantities, and the existence of Penrose processes. Our analysis is not wedded to standard general relativity and so should apply to extended gravity theories where we find that the black hole area must be replaced by some other property in any generalized area theorem. PMID:21902381
Raman Thermometry Measurements of Free Evaporation from LiquidWater Droplets
Smith, Jared D.; Cappa, Christopher D.; Drisdell, Walter S.; Cohen, Ron ald C.; Saykally, Richard J.
Recent theoretical and experimental studies of evaporation have suggested that on average, molecules in the higher-energy tail of the Boltzmann distribution are more readily transferred into the vapor during evaporation. To test these conclusions, the evaporative cooling rates of a droplet train of liquid water injected into vacuum have been studied via Raman thermometry. The resulting cooling rates are fit to an evaporative cooling model based on Knudsen's maximum rate of evaporation, in which we explicitly account for surface cooling. We have determined that the value of the evaporation coefficient ({gamma}{sub e}) of liquid water is 0.62 {+-} 0.09, confirming that a rate-limiting barrier impedes the evaporation rate. Such insight will facilitate the formulation of a microscopic mechanism for the evaporation of liquid water.
Water Management for Evaporatively Cooled Condensers
California at Davis, University of
Water Management for Evaporatively Cooled Condensers Theresa Pistochini May 23rd, 2012 ResearchAirCapacity,tons Gallons of Water Continuous Test - Outdoor Air 110-115 Deg F Cyclic Test - Outdoor Air 110-115 Deg F #12 AverageWaterHardness(ppm) Cooling Degree Days (60░F Reference) 20% Population 70% Population 10
On the Effect of the Atmosphere on the Evaporation of Sessile Droplets of Water
Mottram, Nigel
On the Effect of the Atmosphere on the Evaporation of Sessile Droplets of Water K. Sefiane1 , S. K into the effect of the atmosphere on the evaporation of pinned sessile droplets of water is described. The experimental work investigated the evaporation rates of sessile droplets in atmospheres of three different
Thermal effects of the substrate on water droplet evaporation.
Sobac, B; Brutin, D
We experimentally investigate the behavior of a pinned water droplet evaporating into air. The influence of the substrate temperature and substrate thermal properties on the evaporation process are studied in both hydrophilic and hydrophobic conditions. Our objective is to understand the effect of thermal mechanisms on the droplet evaporation process. The experimental results are compared with the quasisteady, diffusion-driven evaporation model, which is implemented under the influence of the temperature; the model assumes the isothermia of the droplet at the substrate temperature. The results highlight a favorable correlation between the model and the experimental data at ambient temperatures for most situations considered here. The model works to qualitatively describe the influence of the substrate temperature on the evaporation process. However, with an increase in the substrate temperature, the role of the thermal-linked mechanisms becomes increasingly important; this experiment highlights the need for more accurate models to account for the buoyant convection in vapor transport and the evaporative cooling and heat conduction between the droplet and the substrate. Finally, the experimental data reveal the modification of contact angle evolution as the temperature increases and the crucial role played by the nature of the substrate in the evaporation of a sessile droplet. The influence of the substrate thermal properties on the global evaporation rate is explained by the parallel thermal effusivity of the liquid and solid phases. PMID:23005772
Estimating soil water evaporation using radar measurements
NASA Technical Reports Server (NTRS)
Sadeghi, Ali M.; Scott, H. D.; Waite, W. P.; Asrar, G.
Field studies were conducted to evaluate the application of radar reflectivity as compared with the shortwave reflectivity (albedo) used in the Idso-Jackson equation for the estimation of daily evaporation under overcast sky and subhumid climatic conditions. Soil water content, water potential, shortwave and radar reflectivity, and soil and air temperatures were monitored during three soil drying cycles. The data from each cycle were used to calculate daily evaporation from the Idso-Jackson equation and from two other standard methods, the modified Penman and plane of zero-flux. All three methods resulted in similar estimates of evaporation under clear sky conditions; however, under overcast sky conditions, evaporation fluxes computed from the Idso-Jackson equation were consistently lower than the other two methods. The shortwave albedo values in the Idso-Jackson equation were then replaced with radar reflectivities and a new set of total daily evaporation fluxes were calculated. This resulted in a significant improvement in computed soil evaporation fluxes from the Idso-Jackson equation, and a better agreement between the three methods under overcast sky conditions.
{The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: implications for the lifetime of atmospheric ice particles
C. Delval; B. Fluckiger; M. J. Rossi
The rate of evaporation of H_2O, Rev, and its condensation, kcond, on a 1mum thick ice film has been studied in the temperature range 190 to 240K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H_2O on ice unchanged. The resulting Arrhenius expressions for pure ice are Rev=8.0\\\\cdot1029▒ 1\\\\cdot
Soil water evaporation and crop residues
Technology Transfer Automated Retrieval System (TEKTRAN)
Crop residues have value when left in the field and also when removed from the field and sold as a commodity. Reducing soil water evaporation (E) is one of the benefits of leaving crop residues in place. E was measured beneath a corn canopy at the soil suface with nearly full coverage by corn stover...
Biology 390 Problem: Evaporative Water Loss and Temp Reg. thanks to Dr. J.F. Anderson,
Prestwich, Ken
by evaporative cooling during one day by a 70 kg mammal whose rate of metabolism is 3,000 Kcal/day. Assume evaporative cooling is the only mode of heat exchange this mammal can use to regulate its body temperature, iBiology 390 Problem: Evaporative Water Loss and Temp Reg. thanks to Dr. J.F. Anderson, Dept Zoology
The technical conununity has only recently addressed the role of atmospheric temperature variations on rates of air-water vapor phase toxicant exchange. The technical literature has documented that: 1) day time rates of elemental mercury vapor phase air-water exchange can exceed ...
Physiological adjustments of sand gazelles (Gazella subgutturosa) to a boom-or-bust economy: standard fasting metabolic rate, total evaporative water loss, and changes in the sizes of organs during food and water restriction.
Ostrowski, Stephane; Mesochina, Pascal; Williams, Joseph B
To test the hypothesis that desert ungulates adjust their physiology in response to long-term food and water restriction, we established three groups of sand gazelles (Gazella subgutturosa): one that was provided food and water (n = 6; CTRL) ad lib. for 4 mo, one that received ad lib. food and water for the same period but was deprived of food and water for the last 4.5 d (n = 6; EXPT(1)), and one that was exposed to 4 mo of progressive food and water restriction, an experimental regime designed to mimic conditions in a natural desert setting (n = 6; EXPT(2)). At the end of the 4-mo experiment, we measured standard fasting metabolic rate (SFMR) and total evaporative water loss (TEWL) of all sand gazelles and determined lean dry mass of organs of gazelles in CTRL and EXPT(2). Gazelles in CTRL had a mean SFMR of 2,524 +/- 194 kJ d(-1), whereas gazelles in EXPT(1) and EXPT(2) had SFMRs of 2,101+/- 232 and 1,365 +/- 182 kJ d(-1), respectively, values that differed significantly when we controlled for differences in body mass. Gazelles had TEWLs of 151.1 +/- 18.2, 138.5 +/- 17.53, and 98.4 +/- 27.2 g H(2)O d(-1) in CTRL, EXPT(1), and EXPT(2), respectively. For the latter group, mass-independent TEWL was 27.1% of the value for CTRL. We found that normally hydrated sand gazelles had a low mass-adjusted TEWL compared with other arid-zone ungulates: 13.6 g H(2)O kg(-0.898) d(-1), only 17.1% of allometric predictions, the lowest ever measured in an arid-zone ungulate. After 4 mo of progressive food and water restriction, dry lean mass of liver, heart, and muscle of gazelles in EXPT(2) was significantly less than that of these same organs in CTRL, even when we controlled for body mass decrease. Decreases in the dry lean mass of liver explained 70.4% of the variance of SFMR in food- and water-restricted gazelles. As oxygen demands decreased because of reduced organ sizes, gazelles lost less evaporative water, probably because of a decreased respiratory water loss. PMID:16826507
Isotope Fractionation of Water During Evaporation WithoutCondensation
Cappa, Christopher D.; Drisdell, Walter S.; Smith, Jared D.; Saykally, Richard J.; Cohen, Ronald C.
The microscopic events engendering liquid water evaporation have received much attention over the last century, but remain incompletely understood. We present measurements of isotope fractionation occurring during free molecular evaporation from liquid microjets and show that the isotope ratios of evaporating molecules exhibit dramatic differences from equilibrium vapor values, strong variations with the solution deuterium mole fraction, and a clear temperature dependence. These results indicate the existence of an energetic barrier to evaporation and that the evaporation coefficient of water is less than unity. These new insights into water evaporation promise to advance our understanding of the processes that control the formation and lifetime of clouds in the atmosphere.
Isotope fractionation of water during evaporation without condensation.
Cappa, Christopher D; Drisdell, Walter S; Smith, Jared D; Saykally, Richard J; Cohen, Ronald C
The microscopic events engendering liquid water evaporation have received much attention over the last century, but remain incompletely understood. We present measurements of isotope fractionation occurring during free molecular evaporation from liquid microjets and show that the isotope ratios of evaporating molecules exhibit dramatic differences from equilibrium vapor values, strong variations with the solution deuterium mole fraction, and a clear temperature dependence. These results indicate the existence of an energetic barrier to evaporation and that the evaporation coefficient of water is less than unity. These new insights into water evaporation promise to advance our understanding of the processes that control the formation and lifetime of clouds in the atmosphere. PMID:16375440
Absolute evaporation rates of non-rotating neutral PAH clusters
Montillaud, Julien
Clusters of polycyclic aromatic hydrocarbons (PAHs) have been proposed as candidates for evaporating very small grains, which are thought to be precursors of free-flying PAHs. Evaporation rates have been calculated so far only for species containing up to a few 100 C atoms, whereas interstellar PAH clusters could contain up to ~1000 C atoms. We present a method that generalises the calculation of the statistical evaporation rate of large PAH clusters and provides rates for species containing up to ~1000 C-atoms. The evaporation of non-rotating neutral homo-molecular PAH clusters containing up to 12 molecules from a family of highly symmetric compact PAHs is studied. Statistical calculations were performed and completed with molecular dynamics simulations at high internal energies to provide absolute values for the evaporation rate and distributions of kinetic energy released. The calculations used explicit atom-atom Lennard-Jones potentials in the rigid molecule approximation. A new method is proposed to take...
Priority of the Mn Deposition Rate in Reactive Evaporation Conditions
Masaaki Isai; Hiroshi Ichikawa; Takeyoshi Shimada; Keiichiro Morimoto; Hiroshi Fujiyasu; Yasumitsu Ito
Manganese (Mn) oxide films used in lithium secondary batteries were prepared using the reactive evaporation method. One of the problems of using this method is that the manganese evaporant in the crucible suffers oxidation in an oxygen atmosphere. This deteriorates the Mn deposition rate with increasing the deposition run. A separator was introduced in the bottom of the Mn crucible.
Vegetation Cover Decreases Evaporative Water Loss in a Wetland Ecosystem
X. Wang; L. O. Sternberg; F. R. Miralles-Wilhelm
Analysis of oxygen and hydrogen isotope ratios of water is a useful tool for quantitative measurements of water evaporation. Water molecules with the lighter isotopes, H216O, evaporate faster than H218O and DH16O, leaving the residual water enriched in D and 18O. Therefore, the greater the evaporation, the higher the delta18O and deltaD values in the remaining water body. Here we
Hollow-Fiber Spacesuit Water Membrane Evaporator
NASA Technical Reports Server (NTRS)
Bue, Grant; Trevino, Luis; Tsioulos, Gus; Mitchell, Keith; Settles, Joseph
The hollow-fiber spacesuit water membrane evaporator (HoFi SWME) is being developed to perform the thermal control function for advanced spacesuits and spacecraft to take advantage of recent advances in micropore membrane technology in providing a robust, heat-rejection device that is less sensitive to contamination than is the sublimator. After recent contamination tests, a commercial-off-the-shelf (COTS) micro porous hollow-fiber membrane was selected for prototype development as the most suitable candidate among commercial hollow-fiber evaporator alternatives. An innovative design that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape, was developed into a full-scale prototype for the spacesuit application. Vacuum chamber testing has been performed to characterize heat rejection as a function of inlet water temperature and water vapor back-pressure, and to show contamination resistance to the constituents expected to be found in potable water produced by the wastewater reclamation distillation processes. Other tests showed tolerance to freezing and suitability to reject heat in a Mars pressure environment. In summary, HoFi SWME is a lightweight, compact evaporator for heat rejection in the spacesuit that is robust, contamination- insensitive, freeze-tolerant, and able to reject the required heat of spacewalks in microgravity, lunar, and Martian environments. The HoFi is packaged to reject 810 W of heat through 800 hours of use in a vacuum environment, and 370 W in a Mars environment. The device also eliminates free gas and dissolved gas from the coolant loop.
Understanding the role of monolayers in retarding evaporation from water storage bodies
NASA Astrophysics Data System (ADS)
Fellows, Christopher M.; Coop, Paul A.; Lamb, David W.; Bradbury, Ronald C.; Schiretz, Helmut F.; Woolley, Andrew J.
Retardation of evaporation by monomolecular films by a 'barrier model' does not explain the effect of air velocity on relative evaporation rates in the presence and absence of such films. An alternative mechanism for retardation of evaporation attributes reduced evaporation to a reduction of surface roughness, which in turn increases the effective vapour pressure of water above the surface. Evaporation suppression effectiveness under field conditions should be predictable from measurements of the surface dilational modulus of monolayers and research directed to optimising this mechanism should be more fruitful than research aimed at optimising a monolayer to provide an impermeable barrier.
The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: implications for the lifetime of atmospheric ice particles
NASA Astrophysics Data System (ADS)
Delval, C.; Fluckiger, B.; Rossi, M. J.
Using a multidiagnostic approach the rate Rev [ molec cm-3 s-1] or flux Jev [ molec cm-2 s-1] of evaporation of H2O and its corresponding rate constant for condensation, kcond [s-1 ], on a 1 Ąm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions for pure ice are Jev = 1.6 Ę 10 28 ▒ 1 Ę exp (- 10.3 ▒ 1.2/ RT) [ molec cm-2 s-1] , kcond = 1.7 Ę 10 - 2 ▒ 1 Ę exp (+ 1.6 ▒ 1.5/ RT ) [s -1], in the presence of a HCl mole fraction in the range 3.2 Ę 10 - 5 - 6.4 Ę 10 - 3 : Jev = 6.4 Ę 10 26 ▒ 1 Ę exp (- 9.7 ▒ 1.2/ RT) [ molec cm-2 s-1] , kcond = 2.8 Ę 10 - 2 ▒ 1 Ę exp ( + 1.5 ▒ 1.6 /RT) [s -1], and a HBr mole fraction smaller than 6.4 Ę 10 - 3 : Jev = 7.4 Ę 10 25 ▒ 1 Ę exp ( - 9.1 ▒ 1.2 /RT) [ molec cm-2 s-1] , kcond = 7.1 Ę 10 - 5 ▒ 1 Ę exp (+ 2.6 ▒ 1.5/ RT) [s -1]. The small negative activation energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl = Eev - Econd = 11.9 ▒ 2.7 kcal mol-1 , DHsubl = 11.2 ▒ 2.8 kcal mol-1, and DHsubl = 11.7 ▒ 2.8 kcal mol-1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol-1 . Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3-6 and 10-20, respectively, for submonolayer coverages of HX once the fraction of the ice not contaminated by HX has evaporated.
Evaporation rates of alkanes and alkanols from acoustically levitated drops
Rudolf Tuckermann; Sigurd Bauerecker; Bernd Neidhart
Evaporation constants of acoustically levitated drops from the homologue series of n-alkanes and 1-alkanols in ambient air have been evaluated by size and temperature measurements. The size of the pure liquid drops, within a diameter range of 0.1 to 2.5 mm, was monitored using a CCD camera, while temperature measurements were carried out by IR thermography. During drop evaporation, water
Turbulent transition of thermocapillary flow induced by water evaporation
NASA Astrophysics Data System (ADS)
Ward, C. A.; Duan, Fei
Water has been examined for thermocapillary convection while maintained just outside the mouth of a stainless-steel, conical funnel where it evaporated at different but steady rates. Evaporation at a series of controlled rates was produced by reducing the pressure in the vapor-phase to different but constant values while maintaining the temperature of the water a few millimeters below the interface at 3.56▒0.03 ░C in each case. Since water has its maximum density at 4 ░C , these conditions ensured there would be no buoyancy-driven convection. The measured temperature profile along the liquid-vapor interface was found to be approximately axisymmetric and parabolic with its minimum on the center line and maximum at the periphery. The thermocapillary flow rate was determined in two ways: (1) It was calculated from the interfacial temperature gradient measured along the interface. (2) The deflection of a 12.7-?m -diameter, cantilevered probe inserted into the flow was measured and the liquid velocity required to give that deflection determined. The values determined by the two methods agree reasonably. As the vapor-phase pressure was reduced, the thermocapillary flow rate increased until a limiting value was reached. When the pressure was reduced further, certain of the variable relations underwent a bifurcation and the power spectrum of the probe displacement indicated it was a periodic function with frequency locking. These results suggest that thermocapillary flow plays an important role in the energy transport near the interface of evaporating water. In particular, it appears that the subinterface, uniform-temperature layer, reported in earlier studies, results from the mixing produced by the thermocapillary flow. The Stefan boundary condition is often applied to determine the energy flux to an interface where phase change is occurring; however, when there is strong convective flow parallel to the interface, the normal Stefan condition does not give an adequate description of the energy transport.
Assessment of water droplet evaporation mechanisms on hydrophobic and superhydrophobic substrates.
Pan, Zhenhai; Dash, Susmita; Weibel, Justin A; Garimella, Suresh V
Evaporation rates are predicted and important transport mechanisms identified for evaporation of water droplets on hydrophobic (contact angle ~110░) and superhydrophobic (contact angle ~160░) substrates. Analytical models for droplet evaporation in the literature are usually simplified to include only vapor diffusion in the gas domain, and the system is assumed to be isothermal. In the comprehensive model developed in this study, evaporative cooling of the interface is accounted for, and vapor concentration is coupled to local temperature at the interface. Conjugate heat and mass transfer are solved in the solid substrate, liquid droplet, and surrounding gas. Buoyancy-driven convective flows in the droplet and vapor domains are also simulated. The influences of evaporative cooling and convection on the evaporation characteristics are determined quantitatively. The liquid-vapor interface temperature drop induced by evaporative cooling suppresses evaporation, while gas-phase natural convection acts to enhance evaporation. While the effects of these competing transport mechanisms are observed to counterbalance for evaporation on a hydrophobic surface, the stronger influence of evaporative cooling on a superhydrophobic surface accounts for an overprediction of experimental evaporation rates by ~20% with vapor diffusion-based models. The local evaporation fluxes along the liquid-vapor interface for both hydrophobic and superhydrophobic substrates are investigated. The highest local evaporation flux occurs at the three-phase contact line region due to proximity to the higher temperature substrate, rather than at the relatively colder droplet top; vapor diffusion-based models predict the opposite. The numerically calculated evaporation rates agree with experimental results to within 2% for superhydrophobic substrates and 3% for hydrophobic substrates. The large deviations between past analytical models and the experimental data are therefore reconciled with the comprehensive model developed here. PMID:24320680
Long Duration Testing of a Spacesuit Water Membrane Evaporator Prototype
NASA Technical Reports Server (NTRS)
Bue, Grant C.; Makinen, Janice; Cox, Marlon; Watts, Carly; Campbell, Colin; Vogel, Matthew; Colunga, Aaron
The Spacesuit Water Membrane Evaporator (SWME) is a heat-rejection device that is being developed to perform thermal control for advanced spacesuits. Cooling is achieved by circulating water from the liquid cooling garment (LCG) through hollow fibers (HoFi?s), which are small hydrophobic tubes. Liquid water remains within the hydrophobic tubes, but water vapor is exhausted to space, thereby removing heat. A SWME test article was tested over the course of a year, for a total of 1200 cumulative hours. In order to evaluate SWME tolerance to contamination due to constituents caused by distillation processes, these constituents were allowed to accumulate in the water as evaporation occurred. A test article was tested over the course of a year for a total of 1200 cumulative hours. The heat rejection performance of the SWME degraded significantly--below 700 W, attributable to the accumulation of rust in the circulating loop and biofilm growth. Bubble elimination capability, a feature that was previously proven with SWME, was compromised during the test, most likely due to loss of hydrophobic properties of the hollow fibers. The utilization of water for heat rejection was shown not to be dependent on test article, life cycle, heat rejection rate, or freezing of the membranes.
Long Duration Testing of a Spacesuit Water Membrane Evaporator Prototype
NASA Technical Reports Server (NTRS)
Bue, Grant C.; Makinen, Janice; Cox, Marlon; Watts, Carly; Campbell, Colin; Vogel, Matthew; Colunga, Aaron; Conger, Bruce
The Spacesuit Water Membrane Evaporator (SWME) is a heat-rejection device that is being developed to perform thermal control for advanced spacesuits. Cooling is achieved by circulating water from the liquid cooling garment (LCG) through hollow fibers (HoFi s), which are small hydrophobic tubes. Liquid water remains within the hydrophobic tubes, but water vapor is exhausted to space, thereby removing heat. A SWME test article was tested over the course of a year, for a total of 600 cumulative hours. In order to evaluate SWME tolerance to contamination due to constituents caused by distillation processes, these constituents were allowed to accumulate in the water as evaporation occurred. A test article was tested over the course of a year for a total of 600 cumulative hours. The heat rejection performance of the SWME degraded significantly--below 700 W, attributable to the accumulation of rust in the circulating loop and biofilm growth. Bubble elimination capability, a feature that was previously proven with SWME, was compromised during the test, most likely due to loss of hydrophobic properties of the hollow fibers. The utilization of water for heat rejection was shown not to be dependent on test article, life cycle, heat rejection rate, or freezing of the membranes.
The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: Implications for the lifetime of atmospheric ice particles
NASA Astrophysics Data System (ADS)
Delval, C.; Fluckiger, B.; Rossi, M. J.
Using a multidiagnostic approach the rate Rev or flux Jevof evaporation of H2O and its condensation, kcond, on a 1mm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions with RT in kcal mol-1 for pure ice are Jev=1.6ū1028+/-1Ęexp({-10.3+-1.2}/{RT}) [molec cm-2 s-1], kcond=1.7ū10-2+1ūexp({+1.6+-1.5}/{RT}) [s-1], in the presence of an HCl mole fraction in the range 3.2ū10-5-6.4ū10-3: Jev=6.4ū1026+/-1ūexp({-9.7+/-1.2}/{RT}) [molec cm-2 s-1], kcond=2.8ū10-2+/-1ūexp({+1.5+/-1.6}/{RT}) [s-1], and an HBr mole fraction smaller than 6.4ū10-3:Jev=7.4ū1025+/-1ūexp({-9.1+/-1.2}/{RT}) [molec cm-2 s-1], kcond=7.1ū10-5+-1ūexp({+2.6+/-1.5}/{RT}) [s-1]}. The small negative activation energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl=Eev-Econd=11.9+/-2.7 kcal mol-1, DHsubl=11.2+/-2.8 kcal mol-1, and DHsubl=11.7+/-2.8 kcal mol-1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol-1. Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3-6 and 10-20, respectively, for submonolayer coverages of HX.
Studies on the evaporation of crude oil and petroleum products: I. the relationship between evaporation rate and time
Merv F. Fingas
The time dependance of evaporation was studied for several crude oils and petroleum oil products. Evaporation was determined by weight loss measured on a balance and recorded constantly on a computer. Examination of the data shows that most oil and petroleum products evaporate at a logarithmic rate with respect to time. This is attributed to the overall logarithmic appearance of
Numerical modeling of water flow and salt transport in bare saline soil subjected to evaporation
NASA Astrophysics Data System (ADS)
Geng, Xiaolong; Boufadel, Michel C.
A numerical study, based on a density-dependent variably saturated groundwater flow model MARUN, was conducted to investigate subsurface flow and salt transport in bare saline aquifers subjected to evaporation, which was simulated using the bulk aerodynamic formulation. As evaporation was assumed to depend on the pore moisture, the evaporation flux evolved gradually causing a gradual increase in the pore salinity. This is in contrast to prior studies where the high salinity was imposed instantaneously on the ground surface. Key factors likely affecting subsurface hydrodynamics were investigated, including saturated hydraulic conductivity, capillary drive, relative humidity in the air, and surrounding groundwater replenishment. The simulations showed two temporal regimes where the first consists of rapid evaporation for a duration of hours followed by slow evaporation, until evaporation ceases. In the absence of surrounding groundwater replenishment, evaporation-induced density gradient generated an upward water flow initially, and then the flow decreased at which time a high density salt "finger" formed and propagated downwards. Capillary properties and atmospheric condition had significant impacts on subsurface moisture distribution and salt migration in response to the evaporation. The results also suggested that the presence of subsurface water replenishment to the evaporation zone tended to produce a steady evaporation rate at the ground surface.
Evaporation of forsterite in the primordial solar nebula; rates and accompanied isotopic fractionation
Akira Tsuchiyama; Shogo Tachibana; Toshio Takahashi
Evaporation rates of forsterite in the primordial solar nebula were modeled. There are 3 evaporation regimes expected: 1. free evaporation-dominated (FED) regime, where forsterite evaporates as free evaporation, 2. hydrogen reaction-dominated (HRD) regime, where the evaporation is affected by H2 gas, and 3. H2O\\/H2 buffer-dominated (HBD) regime, where the evaporation is controlled by redox states buffered by the H2O\\/H2 ratio
The continuous similarity model of bulk soil-water evaporation
NASA Technical Reports Server (NTRS)
Clapp, R. B.
The continuous similarity model of evaporation is described. In it, evaporation is conceptualized as a two stage process. For an initially moist soil, evaporation is first climate limited, but later it becomes soil limited. During the latter stage, the evaporation rate is termed evaporability, and mathematically it is inversely proportional to the evaporation deficit. A functional approximation of the moisture distribution within the soil column is also included in the model. The model was tested using data from four experiments conducted near Phoenix, Arizona; and there was excellent agreement between the simulated and observed evaporation. The model also predicted the time of transition to the soil limited stage reasonably well. For one of the experiments, a third stage of evaporation, when vapor diffusion predominates, was observed. The occurrence of this stage was related to the decrease in moisture at the surface of the soil. The continuous similarity model does not account for vapor flow. The results show that climate, through the potential evaporation rate, has a strong influence on the time of transition to the soil limited stage. After this transition, however, bulk evaporation is independent of climate until the effects of vapor flow within the soil predominate.
Evaporation estimates from the Dead Sea and their implications on its water balance
NASA Astrophysics Data System (ADS)
Oroud, Ibrahim M.
The Dead Sea (DS) is a terminal hypersaline water body situated in the deepest part of the Jordan Valley. There is a growing interest in linking the DS to the open seas due to severe water shortages in the area and the serious geological and environmental hazards to its vicinity caused by the rapid level drop of the DS. A key issue in linking the DS with the open seas would be an accurate determination of evaporation rates. There exist large uncertainties of evaporation estimates from the DS due to the complex feedback mechanisms between meteorological forcings and thermophysical properties of hypersaline solutions. Numerous methods have been used to estimate current and historical (pre-1960) evaporation rates, with estimates differing by ś100%. Evaporation from the DS is usually deduced indirectly using energy, water balance, or pan methods with uncertainty in many parameters. Accumulated errors resulting from these uncertainties are usually pooled into the estimates of evaporation rates. In this paper, a physically based method with minimum empirical parameters is used to evaluate historical and current evaporation estimates from the DS. The more likely figures for historical and current evaporation rates from the DS were 1,500-1,600 and 1,200-1,250 mm per annum, respectively. Results obtained are congruent with field observations and with more elaborate procedures.
Priority of the Mn Deposition Rate in Reactive Evaporation Conditions
NASA Astrophysics Data System (ADS)
Isai, Masaaki; Ichikawa, Hiroshi; Shimada, Takeyoshi; Morimoto, Keiichiro; Fujiyasu, Hiroshi; Ito, Yasumitsu
Manganese (Mn) oxide films used in lithium secondary batteries were prepared using the reactive evaporation method. One of the problems of using this method is that the manganese evaporant in the crucible suffers oxidation in an oxygen atmosphere. This deteriorates the Mn deposition rate with increasing the deposition run. A separator was introduced in the bottom of the Mn crucible. It could successfully isolate Mn evaporant from incoming oxygen atoms. The film properties depend on the oxygen flow rate, Mn deposition rate, and substrate temperature. These three parameters correlate closely with each other. The importance of Mn deposition rate compared to the rest of the parameters was recognized. The Mn deposition rate is governed by two parameters. One is the source temperature, and the other is the aperture size of the separator. The Mn3O4 films with a hausmannite structure can be prepared under the conditions of Mn deposition rate of 3-10 ┼/s, separator aperture size of 6 mm?, source temperature of 960░C, wall temperature of 900░C and oxygen flow rate of 5 sccm.
Modeling of over Lake Wind Profile for Estimating Water Surface Evaporation Using Land-based meteorological Data
NASA Astrophysics Data System (ADS)
Abbasi, Ali; van de Giesen, Nick
Evaporation from reservoirs and small lakes plays an important role in water management. Estimating the evaporation from surface water resources such as small lakes and reservoirs requires extensive data. Evaporation is difficult and expensive to measure experimentally over the water surface. For operational purposes it would be attractive if evaporation from a lake could be estimated with acceptable accuracy from standard meteorological data taken at nearby land-based stations. Several techniques and models have been suggested and used to estimate evaporation from open water bodies. One of the most commonly used methods is the aerodynamic mass transfer method which gives reliable results for water bodies if suitable data are available. With the aerodynamic approach, evaporation rate is modeled as the product of a vapor pressure deficit between the water surface and upwind air and a wind function that depends on the wind profile over the water surface. As measuring wind speed, and other meteorological data, over a water surface is not easy, most literature uses land-based meteorological measurements. Using land-based meteorological stations data in estimating evaporation introduces significant errors in estimated values of evaporation. On the other hand, the aerodynamic method should account for the size or fetch of a desired water body as evaporation rate decreases with distance downwind from the land-water edge due to increased entrainment of water vapor. Neglecting the fetch effects in this method introduce errors in estimated evaporation values. In this paper, we use a CFD model (RANS Model) to simulate the wind profile over the water surface that utilizes land-based measurements. The modeled wind profile is used to estimate evaporation from water surface using the aerodynamic approach. This proposed model is tested for small lakes and reservoirs in arid and semi-arid regions. Results show a good agreement with the experimental measurements and can be used in water management plans to estimate evaporation from reservoirs and small water bodies.
Quantification of soil water evaporation using TDR-microlysimetry
Technology Transfer Automated Retrieval System (TEKTRAN)
Soil water evaporation is conventionally measured using microlysimeters by evaluating the daily change in mass. Daily removal is laborious and replacement immediately after irrigation events is impractical because of field wetness which leads to delays and an underestimation of evaporation. Irrigati...
Temperature dependence of the vapor pressure and evaporation coefficient of supercooled water
NASA Astrophysics Data System (ADS)
Davies, James F.; Miles, Rachael E. H.; Haddrell, Allen E.; Reid, Jonathan P.
We report measurements of the vapor pressure of water over the supercooled temperature range 248 to 273 K derived from evaporation kinetics measurements of single water droplets. Accurate measurements of the relative humidity of the surrounding gas phase are derived from comparative and sequential measurements of the evaporation kinetics of droplets containing sodium chloride. The temperature dependence of the vapor pressure of supercooled water is shown to conform closely to the parameterization provided by Murphy and Koop (2005) once the uncertainties in experimental and thermophysical parameters are accounted for by ensuring an accurate representation of evaporation rates at temperatures above 273 K. Further, from a sensitivity analysis of all of the data over the full temperature range from 248 to 293 K, we can conclude that the evaporation coefficient of water, and thus the mass accommodation coefficient, is greater than, or equal to, 0.5.
Spacesuit Water Membrane Evaporator; An Enhanced Evaporative Cooling Systems for the Advanced Extravehicular Mobility Unit Portable Life Support System
NASA Technical Reports Server (NTRS)
Bue, Grant C.; Makinen, Janice V.; Miller, Sean.; Campbell, Colin; Lynch, Bill; Vogel, Matt; Craft, Jesse; Petty, Brian
Spacesuit Water Membrane Evaporator - Baseline heat rejection technology for the Portable Life Support System of the Advanced EMU center dot Replaces sublimator in the current EMU center dot Contamination insensitive center dot Can work with Lithium Chloride Absorber Radiator in Spacesuit Evaporator Absorber Radiator (SEAR) to reject heat and reuse evaporated water The Spacesuit Water Membrane Evaporator (SWME) is being developed to replace the sublimator for future generation spacesuits. Water in LCVG absorbs body heat while circulating center dot Warm water pumped through SWME center dot SWME evaporates water vapor, while maintaining liquid water - Cools water center dot Cooled water is then recirculated through LCVG. center dot LCVG water lost due to evaporation (cooling) is replaced from feedwater The Independent TCV Manifold reduces design complexity and manufacturing difficulty of the SWME End Cap. center dot The offset motor for the new BPV reduces the volume profile of the SWME by laying the motor flat on the End Cap alongside the TCV.
Evaporation measurements by eddy covariance from an urban tropical water reservoir
NASA Astrophysics Data System (ADS)
Velasco, E.; Roth, M.
One of the major problems in the management of water reservoirs is the accurate estimation of water loss by evaporation. This is particularly true for countries where the water supply relies on imported and recycled water, seawater desalination, and rainfall collected in reservoirs, such as Singapore. Within this context, an eddy covariance system was deployed on the shore of an urban water body in Singapore (Bedok reservoir) with sufficient fetch to measure the upwind evaporation during a period of two weeks. This was likely the first such study for a small urban tropical water catchment. Evaporation was found to follow a clear diurnal pattern, ranging from 0.03 mm h-1 during nighttime to an early afternoon peak of 0.25 mm h-1. These values are similar to the summertime evaporation rates reported for larger lakes in subtropical or mid-latitude locations. The evaporation shows a strong correlation with atmospheric turbulence u* (friction velocity) which is related to wind speed. However, the heat stored in the water appears to be the main parameter driving the evaporation from the reservoir because of the relatively calm winds (< 2.5 m s-1) observed during most of the study. The surface water temperature was consistently (between 2 - 3.5 degC) warmer than air temperature throughout the diurnal course. Much of the net radiation received during daytime is channeled into heating the water which results in the higher water temperatures. The high humidity (> 65%) during the study appears, on the other hand, to work to reduce evaporation. These results are preliminary and a longer observation period is needed to be able to carry out a more thorough analysis. The results, however, are useful to test simple predictive evaporation models based on similarity theory and which require only basic meteorological input data.
Influence of Physical Factors on Trichloroethylene Evaporation from Surface Water
Prabhakar Pant; Marshall Allen; Yong Cai; Krishnaswamy Jayachandran; Yin Chen
Evaporation of trichloroethylene (TCE) is a viable option in the remediation of TCE contaminated water. In this study, laboratory\\u000a batch experiments were conducted to understand the evaporation kinetics of TCE in surface water, with further extension of\\u000a this knowledge to field application. Experiments were set up for 15, 30, 60, and 90Āmin time intervals in open glass containers\\u000a with initial
Developing a CFD-based Approach to Estimate Evaporation from Water Surfaces in (Semi-) Arid Regions
NASA Astrophysics Data System (ADS)
Abbasi, Ali; Annor, Frank; van de Giesen, Nick
In arid and semi-arid regions where evaporation highly exceeds rainfall, approximately one half of the stored water in shallow lakes may be lost due to evaporation. Precisely estimating this for very shallow lakes is however a daunting tasks due to the complexity of lake thermodynamics and the interactions between the water surface and air. Evaporation in water is largely uncoupled from land based evapotranspiration and most methods used are case-specific equations which are usually not applicable for other lakes. In this study a Computational Fluid Dynamics(CFD) Evaporation Model is established to adequately quantify the evaporation losses by simulating the air flow and heat transfer in the atmospheric boundary layer. Consideration of the air flow and heat transfer is required to simulate the fetch effect. This model will help to understand the complexities involved in open water evaporation and consequently will lead to more accurate estimates and better strategies for managing and controlling the evaporative loss of fresh water in arid and semi-arid regions. The proposed approach is used to drive a convective mass-transfer coefficient (wind function) required for estimating evaporation of water bodies with the mass-transfer method. The model was applied for a small shallow (with a surface area of 45 hectares and 3m deep on the average) artificial lake in Ghana called Binaba. The heat and mass transfer coefficient over the water surface and their distributions were extracted from the CFD analysis. The results showed that the CFD-derived wind functions were very similar to those empirically derived from the measurements over the lake using Eddy Covariance(EC) System. The evaporation rates calculated with the synthetic wind functions were in good agreement with hourly and daily evaporation measurements for the lake. The established CFD-model is generalizable and cost effective, since it needs low input data. Besides, the model is able to provide additional parameters such as the spatial distribution of the evaporation rate over the water surface. The application of CFD to estimate water bodies evaporation looks very promising.
Calculation of Reactive-evaporation Rates of Chromia
Holcomb, G.R.
A methodology is developed to calculate Cr-evaporation rates from Cr2O3 with a flat planar geometry. Variables include temperature, total pressure, gas velocity, and gas composition. The methodology was applied to solid-oxide, fuel cell conditions for metallic interconnects and to advanced-steam turbines conditions. The high velocities and pressures of the advanced steam turbine led to evaporation predictions as high as 5.18 9 10-8 kg/m2/s of CrO2(OH)2(g) at 760 ░C and 34.5 MPa. This is equivalent to 0.080 mm per year of solid Cr loss. Chromium evaporation is expected to be an important oxidation mechanism with the types of nickel-base alloys proposed for use above 650 ░C in advanced-steam boilers and turbines. It is shown that laboratory experiments, with much lower steam velocities and usually much lower total pressure than found in advanced steam turbines, would best reproduce chromium-evaporation behavior with atmospheres that approach either O2 + H2O or air + H2O with 57% H2O.
SUMMARY The rate of evaporative cooling was calculated from the rate of mass loss in starlings (Sturnus vulgaris) during 90 min flights in a wind-tunnel. Evapo- rative heat loss ranged from 5 % of the metabolic rate at Ś 5 ░C to 19% of the metabolic rate at 29 ░C. Radiation and convection accounted for the balance of the heat
Correlation of chemical evaporation rate with vapor pressure.
Mackay, Donald; van Wesenbeeck, Ian
A new one-parameter correlation is developed for the evaporation rate (ER) of chemicals as a function of molar mass (M) and vapor pressure (P) that is simpler than existing correlations. It applies only to liquid surfaces that are unaffected by the underlying solid substrate as occurs in the standard ASTM evaporation rate test and to quiescent liquid pools. The relationship has a sounder theoretical basis than previous correlations because ER is correctly correlated with PM rather than P alone. The inclusion of M increases the slope of previous log ER versus log P regressions to a value close to 1.0 and yields a simpler one-parameter correlation, namely, ER (?g m(-1) h(-1)) = 1464P (Pa) ū M (g mol(-1)). Applications are discussed for the screening level assessment and ranking of chemicals for evaporation rate, such as pesticides, fumigants, and hydrocarbon carrier fluids used in pesticide formulations, liquid consumer products used indoors, and accidental spills of liquids. The mechanistic significance of the single parameter as a mass-transfer coefficient or velocity is discussed. PMID:25105222
Evaporation rate from square capillaries limited by corner flow viscous losses
NASA Astrophysics Data System (ADS)
Hoogland, F.; Lehmann, P.; Yiotis, A.; Or, D.
High evaporation rates from soil surfaces are sustained by capillary flows drawing water from the receding drying front along liquid pathways in crevices of the pore space. With increasing depth of the drying front viscous losses add to growing gravitational head and at a certain depth overcome capillary drive and disrupt liquid pathways. Viscous losses are significant in fine textured media resulting in earlier capillary failure than predicted by gravity-capillary force balance. To reproduce limitations of viscous corner flow on evaporation rates from angular pores (capillaries) we imaged drying dynamics from a square shaped glass capillary using a high speed camera, to provide for detailed record on receding menisci and thickness of liquid corner films including detachment dynamics at the top of the capillary. Additionally, deposition patterns of dye delineated regions of high rates of phase change (evaporation) showing a decrease in drying rate with recession of menisci and films into the capillary due to increasing diffusive path and reduced gradients. Effects of viscous losses on evaporation dynamics were systematically evaluated by varying ratio of viscous, gravity and capillary forces using different liquids (water, ethanol and octane), capillary geometry (0.5 and 1.0 mm width), and flow rate and direction with respect to gravity (horizontal and vertical arrangement). Experimental results were compared with analytical solutions for corner flow considering viscous losses. Preliminary results indicate that the maximum (main) meniscus depth supporting corner flow is not only dependent on the effective conductivity behind the interfaces, but also on interfacial processes taking place at the very top of the capillary. The pore scale findings will be incorporated into macroscopic models for determining viscous losses from soils and for estimating elapsed times for transition from high capillary-sustained evaporation rates to diffusion limited rates.
New Compounds for the Control of Water Evaporation
A. V. Deo; N. R. Sanjana; S. B. Kulkarni; M. K. Gharpurey; A. B. Biswas
CONSIDERABLE attention has lately been directed towards effective suppression of water evaporation from lakes and reservoirs by spreading insoluble monomolecular films over the water surfaces1,2. In order to be effective, the film-forming compound should have several desirable properties3 such as : (i) low melting point (~ 50░ C.), which will enable it to spread rapidly on the water surface so
Using water stable isotopes to assess evaporation and water residence time of lakes in EPA's National Lakes Assessment
NASA Astrophysics Data System (ADS)
Brooks, J.; Gibson, J. J.; Birks, S. J.
Stable isotopes of water (?18O and ?2H) can be very useful in large-scale monitoring programs because water samples are easy to collect and water isotopes integrate information about basic hydrological processes such as evaporation as a percentage of inflow (E/I), water residence time and water yield from the watershed. Traditional techniques to acquire such information require significant time and effort beyond what is possible in a one-day assessment. Thus, measurements of these important hydrological processes are often excluded from spatially extensive monitoring programs such as EPA's National Aquatic Resource Surveys. We used the stable isotopes of water (?2H and ?18O) analyzed from water collected from 1000+ lakes across the country in EPA's 2007 National Lakes Assessment to derive information these hydrological variables. Water isotopes for precipitation inputs were estimated using the spatially explicit models found at Waterisotopes.org. Lake water isotopes ranged from 5 to -20 ē for ?18O and 20 to -135 ē for ?2H with d-excess values (an indicator of evaporation) ranging from 13 to -43 ē. Lakes were more enriched than the local precipitation with dual-isotope slope median of 5.1, indicating evaporation as the cause for the enrichment over precipitation. Using isotope evaporation theory, we estimated E/I, water residence time, water yield and the runoff ratio for lake watersheds across the USA. For 50 % of the lakes, evaporation was less than 20 % of the inflow, with values ranging from 135 % to no detectable evaporation. Strong spatial patterns in E/I were found across the USA with the West and mid-West being more evaporated than the East Coast. While climate patterns drove some of the spatial patterns of evaporation in lakes, variation in lake water residence time was also a driver. To assess the importance of these hydrological variables to lake biological condition, we rated lakes for high E/I by comparing them to reference lakes within the same ecoregion. Interestingly, we found that highly evaporated natural lakes were four times more likely to be in poor biological condition compared to less evaporated lakes, but evaporation was not correlated with biological condition in man-made lakes (i.e. reservoirs). We speculate that this link to lake condition comes from a strong correlation between E/I and lake total nitrogen concentration. Water samples for lake water isotopes were also collected during the 2012 National Lake Assessment so that temporal trends can begin to be assessed in the future.
The desorptivity model of bulk soil-water evaporation
NASA Technical Reports Server (NTRS)
Clapp, R. B.
Available models of bulk evaporation from a bare-surfaced soil are difficult to apply to field conditions where evaporation is complicated by two main factors: rate-limiting climatic conditions and redistribution of soil moisture following infiltration. Both factors are included in the "desorptivity model', wherein the evaporation rate during the second stage (the soil-limiting stage) of evaporation is related to the desorptivity parameter, A. Analytical approximations for A are presented. The approximations are independent of the surface soil moisture. However, calculations using the approximations indicate that both soil texture and soil moisture content at depth significantly affect A. Because the moisture content at depth decreases in time during redistribution, it follows that the A parameter also changes with time. Consequently, a method to calculate a representative value of A was developed. When applied to field data, the desorptivity model estimated cumulative evaporation well. The model is easy to calculate, but its usefulness is limited because it requires an independent estimate of the time of transition between the first and second stages of evaporation. The model shows that bulk evaporation after the transition to the second stage is largely independent of climatic conditions.
Evaporation of water from sodium chloride solutions under controlled climatic conditionsĀ
Moore, Jaroy
tubes and thermo- couples inserted 17 Close-up view of one container showing double walls and position of sampling depths 18 Diagram of water metering system 20 Reservoir jugs and burettes used to supply water to evaporation containers 22... the effect 1/ of specific gravity of solutions on the rate of evaporation. ? Methods employed were as follows: Two samples of water were used, one dis- tilled and one a brine from Owens Lake, California with a specific gravity of 1. 11. The samples were...
Gas scavenging of insoluble vapors: Condensation of methyl salicylate vapor onto evaporating drops of water
NASA Astrophysics Data System (ADS)
Seaver, Mark; Peele, J. R.; Rubel, Glenn O.
We have observed the evaporation of acoustically levitated water drops at 0 and 32% relative humidity in a moving gas stream which is nearly saturated with methyl salicylate vapor. The initial evaporation rate is characteristic of a pure water drop and gradually slows until the evaporation rate becomes that of pure methyl salicylate. The quantity of condensed methyl salicylate exceeds its Henry's law solubility in water by factors of more than 30-50. This apparent violation of Henry's law agrees with the concentration enhancements in the liquid phase found by glotfelty et al. (1987, Nature235, 602-605) during their field measurements of organophorus pesticides in fog water. Under our conditions, visual evidence demonstrates the presence of two liquid phases, thus invalidating the use of Henry's law. A continuum evaporation-condensation model for an immiscible two-component system which accounts for evaporative self-cooling of the drop correctly predicts the amount of methyl salicylate condensed onto the water drops.
Aerosol synthesis of lipid nanoparticles: Relating crystallinity to simulated evaporation rates
Manish Shetty; Amol A. Pawar; Anurag Mehra; Chandra Venkataraman
The degree of crystallinity of nanometre size lipid matrices governs drug loading and release rates. Recently, droplet-phase aerosol synthesis was used to prepare lipid nanoparticles of stearic acid and achieve control over their crystallinity using precursor solvents with differing vapour pressures. The present work aims at examining relationships between solvent evaporation rate and extent of evaporative cooling, during drop evaporation,
Atmospheric sugar alcohols: evaporation rates and saturation vapor pressures
NASA Astrophysics Data System (ADS)
Bilde, M.; Zardini, A. A.; Hong, J.; Tschiskale, M.; Emanuelsson, E.
The atmospheric partitioning between gas and condensed phase of organic molecules is poorly understood, and discrepancies exist between predicted and observed concentrations of secondary organic aerosols. A key problem is the lack of information about thermodynamic properties of semi- and low volatile organic molecules. Saturation vapor pressure and the associated temperature dependence (dH) are key parameters for improving predictive atmospheric models. In this work we combine experiments and thermodynamic modeling to investigate these parameters for a series of polyols, so-called sugar alcohols. These polyols are common in the water soluble fraction of atmospheric aerosols. In our experimental system sub-micron particles are generated by nebulization from aqueous solution, and a mono disperse fraction of the aerosol is selected using a differential mobility analyzer. The particles are allowed to evaporate in a laminar flow reactor, and changes in particle size as function of evaporation time are determined using a scanning mobility particle sizer system. In this work saturation vapor pressures of sugar alcohols at several temperatures have been inferred from such measurements using thermodynamic modeling. Results are presented and discussed in context of atmospheric gas to particle partitioning.
Convective heat and mass transfer from single evaporating water, methanol and ethanol droplets
Yearling, P.R.; Gould, R.D. [North Carolina State Univ., Raleigh, NC (United States). Dept. of Mechanical and Aerospace Engineering
The experimental measurements of convective heat and mass transfer rates from single evaporating water, methanol and ethanol droplets suspended in a turbulent air flow are considered. This study is a continuation of the work presented by Yearling and Gould (1993). Specifically, this paper considers the effects of Reynolds number, mass transfer number and turbulence intensity of the upstream air on the evaporation rate of liquid droplets. For a turbulence intensity of 5% these measurements show that the Nusselt number increases by up to 30% over that for a laminar flow at the same droplet Reynolds number. At 10% turbulence intensity the Nusselt number increases by up to 50%.
Dynamics of Water Absorption and Evaporation During Methanol Droplet Combustion in Microgravity
NASA Technical Reports Server (NTRS)
Hicks, Michael C.; Dietrich, Daniel L.; Nayagam, Vedha; Williams, Forman A.
The combustion of methanol droplets is profoundly influenced by the absorption and evaporation of water, generated in the gas phase as a part of the combustion products. Initially there is a water-absorption period of combustion during which the latent heat of condensation of water vapor, released into the droplet, enhances its burning rate, whereas later there is a water-evaporation period, during which the water vapor reduces the flame temperature suffciently to extinguish the flame. Recent methanol droplet-combustion experiments in ambient environments diluted with carbon dioxide, conducted in the Combustion Integrated Rack on the International Space Station (ISS), as a part of the FLEX project, provided a method to delineate the water-absorption period from the water-evaporation period using video images of flame intensity. These were obtained using an ultra-violet camera that captures the OH* radical emission at 310 nm wavelength and a color camera that captures visible flame emission. These results are compared with results of ground-based tests in the Zero Gravity Facility at the NASA Glenn Research Center which employed smaller droplets in argon-diluted environments. A simplified theoretical model developed earlier correlates the transition time at which water absorption ends and evaporation starts. The model results are shown to agree reasonably well with experiment.
A Mass Function Constraint on Extrasolar Giant Planet Evaporation Rates
W. B Hubbard; M. Hattori; A. Burrows; I. Hubeny
The observed mass function for all known extrasolar giant planets (EGPs) varies approximately as M^{-1} for mass M between 0.2 Jupiter masses (M_J) and 5 M_J. In order to study evaporation effects for highly-irradiated EGPs in this mass range, we have constructed an observational mass function for a subset of EGPs in the same mass range but with orbital radii mass function for such highly-irradiated EGPs agrees quantitatively with the M^{-1} law, implying that the mass function for EGPs is preserved despite migration to small orbital radii. Unless there is a remarkable compensation of mass-dependent orbital migration for mass-dependent evaporation, this result places a constraint on orbital migration models and rules out the most extreme mass loss rates in the literature. A theory that predicts more moderate mass loss gives a mass function that is closer to observed statistics but still disagrees for M < 1 M_J.
Interfacial conditions during evaporation or condensation of water
C. A. Ward; D. Stanga
Steady-state evaporation and condensation experiments have been conducted with water under conditions where buoyancy-driven convection is not present. The temperature profile in each phase has been measured. At the interface, independently of the direction of the phase change, a temperature discontinuity has been found to exist in which the interfacial vapor temperature is greater than that in the liquid. In
Macroscale estimation of evaporation from regional water balance
Annual evaporation (E) is often determined using the water balance approach, E = P - Q, because precipitation (P) and runoff (Q) are easily obtainable for most parts of the world. From a regional perspective, P and Q are point observations, containing information pertaining both to the regional trend and to the local environment. Trend surface analysis provides a simple
Cold-hardiness and evaporative water loss in hatchling turtles.
Costanzo, J P; Litzgus, J D; Iverson, J B; Lee, R E
North American turtles hatch in late summer and spend their first winter either on land or underwater. Adaptations for terrestrial overwintering of hatchlings in northern regions, where winter thermal and hydric regimes are harsh, have not been systematically investigated in many species. We measured intrinsic supercooling capacity, resistance to inoculative freezing, and desiccation resistance in hatchlings of terrestrial and aquatic turtles collected from northern (Terrapene ornata, Chrysemys picta bellii, Kinosternon flavescens, Chelydra serpentina) and southern (Chrysemys picta dorsalis, Trachemys scripta, Sternotherus odoratus, Sternotherus carinatus) locales. Supercooling capacity was estimated from the crystallization temperature of turtles cooled in the absence of external ice nuclei. Mean values ranged from -8.1 degrees to -15.5 degrees C and tended to be lower in terrestrial hibernators. Inoculation resistance was estimated from the crystallization temperature of turtles cooled in a matrix of frozen soil. These values (range of means: -0.8 degrees to -13.6 degrees C) also tended to be lower in the terrestrial hibernators, especially C. picta bellii. Mean rates of evaporative water loss varied markedly among the species (0.9-11.4 mg g(-1) d(-1)) and were lowest in the terrestrial hibernators. Most species tolerated the loss of a modest amount of body water, although half of the sample of S. carinatus died from desiccation. In general, turtles did not regain lost body water from wet soil, and immersion in free water was required for rehydration. Therefore, desiccation resistance may be an important adaptation to terrestrial hibernation. Resistances to inoculative freezing and desiccation were directly correlated, perhaps because they are governed by the same morphological characteristics. PMID:11436135
Benefits of evaporating FGD purge water
Shaw, W.A. [HPD, Plainfield, IL (United States)
In the US and the European Union, scrubbers are installed on all new coal-fired power plants because their technology is considered the best available for removing SO{sub 2}. A zero liquid discharge (ZLD) system is the best technology for treating wet scrubber wastewate. With the future promising stricter limits on power plants' water use, ZLD systems that concentrate scrubber purge streams are sure to become as common as ZLD cooling tower blowdonw systems. 7 figs.
Evaporating behaviors of water droplet on superhydrophobic surface
NASA Astrophysics Data System (ADS)
Hao, PengFei; Lv, CunJing; He, Feng
We investigated the dynamic evaporating behaviors of water droplet on superhydrophobic surfaces with micropillars. Our experimental data showed that receding contact angles of the water droplet increased with the decreasing of the scale of the micropillars during evaporation, even though the solid area fractions of the microstructured substrates remained constant. We also experimentally found that the critical contact diameters of the transition between the Cassie-Baxter and Wenzel states are affected not only by the geometrical parameters of the microstructures, but also by the initial volume of the water droplet. The measured critical pressure is consistent with the theoretical model, which validated the pressure-induced impalement mechanism for the wetting state transition.
Impact of groundwater levels on evaporation and water-vapor fluxes in highly saline soils
NASA Astrophysics Data System (ADS)
Munoz, J. F.; Hernßndez, M. F.; Braud, I.; Gironas, J. A.; Suarez, F. I.
In aquifers of arid and hyper-arid zones, such as those occurring in the Chilean Andes high plateau, it is important to determine both the quantity and location of water discharges at the temporal scales of interest to close the basin's water budget and thus, to manage the water resource properly. In zones where shallow aquifers are the main source of water, overexploitation of the water resource changes the dynamics of water, heat and solute transport in the vadose zone. As aquifers are exploited, fluctuations in depth to groundwater are exacerbated. These fluctuations modify both soil structure and evaporation from the ground, which is typically the most important discharge from the water budget and is very difficult to estimate. Therefore, a correct quantification of evaporation from these soils is essential to improve the accuracy of the water balance estimation. The objective of this study was to investigate the evaporation processes and water-vapor fluxes in a soil column filled with a saline soil from the Salar del Huasco basin, Chile. Water content, electrical conductivity and temperature at different depths in the soil profile were monitored to determine the liquid and vapor fluxes within the soil column. The results showed that evaporation is negligible when the groundwater table is deeper than 1 m. For shallower groundwater levels, evaporation increases in an exponential fashion reaching a value of 3 mm/day when the groundwater table is near the surface of the ground. These evaporation rates are on the same order of magnitude than the field measurements, but slightly lower due to the controlled conditions maintained in the laboratory. Isothermal fluid fluxes were predominant over the non-isothermal fluid and water vapor fluxes. The net flux for all the phreatic levels tested in the laboratory showed different behaviors, with ascending or descending flows as a consequence of changes in water content and temperature distribution within the soil. It was found that evaporation from bare soils occurs as a consequence of vapor transport due to the thermal gradients. This vapor transport was also influences by the salinity of the soil.
Analysis of the evaporation coefficient and the condensation coefficient of water
R. Marek; J. Straub
The evaporation and condensation coefficients of water are extensively analyzed considering also data hitherto not taken into account. From the performed evaluation, a decline of both coefficients with increasing temperature and pressure is derived. For water, the condensation coefficients is generally higher than the evaporation coefficient. Evaporation and condensation coefficients exceed 0.1 for dynamically renewing water surfaces, while the analysis
Influence of condensate evaporation on water vapor and its stable isotopes in a GCM
Influence of condensate evaporation on water vapor and its stable isotopes in a GCM Jonathon S May 2009; published 17 June 2009. [1] The direct effect of condensate evaporation on atmospheric water. S., A. H. Sobel, and G. A. Schmidt (2009), Influence of condensate evaporation on water vapor
Evaporative cooling of water in a natural draft cooling tower
S. P. Fisenko; A. I. Petruchik; A. D. Solodukhin
A mathematical model of the performance of a cooling tower is presented. The model consists of two interdependent boundary-value problems, a total of 9 ODE, and the algorithm of self-consistent solution. The first boundary-value problem describes evaporative cooling of water drops in the spray zone of a cooling tower; the second boundary-value problem describes film cooling in the pack. Simulation
The contribution of evapotranspiration and evaporation to the water budget of a treatment wetland in Phoenix, AZ, USA
Hall, Sharon J.
loss was much higher than open water evaporative losses measured with evaporation pans. EvaporationThe contribution of evapotranspiration and evaporation to the water budget of a treatment wetland important aspects of any wetland is the water budget. Quantifying how evaporation and evapotranspiration
Validation of the doubly labeled water method in growing precocial birds: the importance of assumptions concerning evaporative water loss.
Visser, G H; Schekkerman, H
The doubly labeled water (DLW) method was validated against respiration gas analysis in growing precocial chicks of the black-tailed godwit (Limosa limosa) and the northern lapwing (Vanellus vanellus). To calculate the rate of CO2 production from DLW measurements, Lifson and McClintock's equations (6) and (35) were employed, as well as Speakman's equation (7.17) (all single-pool models). The average errors obtained with the first two equations (+7.2% and -11.6%, respectively) differed significantly from zero but not the error obtained with Speakman's equation (average: -2.9%). The latter error could be reduced by taking a fractional evaporative water loss of 0.13, instead of the value of 0. 25 recommended by Speakman. Application of different two-pool models resulted in relative errors of the DLW method of -15.9% or more. After employing the single-pool model with a fractional evaporative water loss value of 0.13, it was found that there was no relationship between the relative growth rate of the chick and the relative error of the DLW method. Recalculation of previously published results on Arctic tern (Sterna paradisaea) chicks revealed that the fit of the validation experiment could be considerably improved by employing a single-pool model and assuming a fractional evaporative water loss of 0.20 instead of the value of 0.50 taken originally. After employing the value of 0.20, it was found that there was no relationship between the relative growth rate of the chick and the relative error of the DLW method. This suggests that isotope incorporation into new body substances does not cause a detectable error. Thus, the DLW method seems to be applicable in young birds growing as fast as 20% d-1, after making adjustments for the fractional evaporative water loss. We recommend Speakman's equation (7.17) for general use in growing birds when evaporation is unknown. PMID:10603338
A comparison of methods for estimating open-water evaporation in small wetlands
Masoner, Jason R.; Stannard, David I.
We compared evaporation measurements from a floating pan, land pan, chamber, and the Priestley-Taylor (PT) equation. Floating pan, land pan, and meteorological data were collected from June 6 to July 21, 2005, at a small wetland in the Canadian River alluvium in central Oklahoma, USA. Evaporation measured with the floating pan compared favorably to 12Āh chamber measurements. Differences between chamber and floating pan rates ranged from ?0.2 to 0.3Āmm, mean of 0.1Āmm. The difference between chamber and land pan rates ranged from 0.8 to 2.0Āmm, mean of 1.5Āmm. The mean chamber-to-floating pan ratio was 0.97 and the mean chamber-to-land pan ratio was 0.73. The chamber-to-floating pan ratio of 0.97 indicates the use of a floating pan to measure evaporation in small limited-fetch water bodies is an appropriate and accurate method for the site investigated. One-sided Paired t-Tests indicate daily floating pan rates were significantly less than land pan and PT rates. A two-sided Paired t-Test indicated there was no significant difference between land pan and PT values. The PT equation tends to overestimate evaporation during times when the air is of low drying power and tends to underestimate as drying power increases.
Evaporation of tiny water aggregation on solid surfaces of different wetting properties
Shen Wang; Yusong Tu; Rongzheng Wan; Haiping Fang
The evaporation of a tiny amount of water on the solid surface with different wettability has been studied by molecular dynamics simulations. We found that, as the surface changed from hydrophobicity to hydrophility, the evaporation speed did not show a monotonically decrease from intuition, but increased first, and then decreased after reached a maximum value. The competition between the number of the water molecules on the water-gas surface from where the water molecules can evaporate and the potential barrier to prevent those water molecules from evaporating results in the unexpected behavior of the evaporation. A theoretical model based on those two factors can fit the simulation data very well. This finding is helpful in understanding the evaporation on the biological surfaces, designing artificial surface of ultra fast water evaporating or preserving water in soil.
Water loss through evaporation from water surfaces of lakes and reservoirs in Turkey
Ferhat G÷kbulak; S³leyman ųzhan
The objective of this study2 was to estimate the amount of evaporative loss from fresh water lake and reservoir surfaces in Turkey and to compare it with supplied water in Turkey. In this study 129 lakes and 223 reservoirs were subjected to evaporation estimates. The total surface area was 3213.97 km2 and 4026.16 km2 for the lakes and the reservoirs,
Respiratory evaporative water loss during hovering and forward flight in hummingbirds.
Powers, Donald R; Getsinger, Philip W; Tobalske, Bret W; Wethington, Susan M; Powers, Sean D; Warrick, Douglas R
Hummingbirds represent an end point for small body size and water flux in vertebrates. We explored the role evaporative water loss (EWL) plays in management of their large water pool and its use in dissipating metabolic heat. We measured respiratory evaporative water loss (REWL) in hovering hummingbirds in the field (6 species) and over a range of speeds in a wind tunnel (1 species) using an open-circuit mask respirometry system. Hovering REWL during the active period was positively correlated with operative temperature (T(e)) likely due to some combination of an increase in the vapor-pressure deficit, increase in lung ventilation rate, and reduced importance of dry heat transfer at higher T(e). In rufous hummingbirds (Selasphorus rufus; 3.3g) REWL during forward flight at 6 and 10 m/s was less than half the value for hovering. The proportion of total dissipated heat (TDH) accounted for by REWL during hovering at T(e)> 40░C was <40% in most species. During forward flight in S. rufus the proportion of TDH accounted for by REWL was ~35% less than for hovering. REWL in hummingbirds is a relatively small component of the water budget compared with other bird species (<20%) so cutaneous evaporative water loss and dry heat transfer must contribute significantly to thermal balance in hummingbirds. PMID:22123217
Components of evaporative water loss in the desert tenebrionid beetles, Eleodes armata and Cryptoglossa verrucosa
Cooper, P.D.
Water loss in Eleodes armata and Cryptoglossa verrucosa increased with increasing temperature and decreasing vapor activity (a/sub v/). Rates of evaporative water loss were always about 4 times greater in E. armata than in C. verrucosa at the different temperatures and 0.0 a/sub v/, while as a/sub v/ increased the ratio of E. armata loss to C. verrucosa decreased from 4 at 0.0 a/sub v/ to about 2 at 0.94 a/sub v/. A method for determining mesothoracic spiracular, sub-elytral abdominal, and cuticular water loss rates was described and validated for living E. armata. Sub-elytral abdominal water loss through the caudal opening was 8.0 mg H/sub 2/O (g.d)/sup -1/, meso-thoracic spiracular water loss was approximately 7.9 mg H/sub 2/O (g.d)/sup -1/, and cuticular loss was 26.2 mg H/sub 2/O (g.d)/sup -1/ at 30 C and 0.0 a/sub v/. Evaporative water loss was shown to have two unidirectional components, efflux and influx, for both beetles with the use of tritiated water (H/sup 3/HO). Efflux was independent of a/sub v/, while influx increased linearly with a/sub v/, with both components having lower rates in C. verrucosa compared to E. armata.
Cumulative soil water evaporation as a function of depth and time
Technology Transfer Automated Retrieval System (TEKTRAN)
Soil water evaporation is an important component of the surface water balance and the surface energy balance. Accurate and dynamic measurements of soil water evaporation enhance the understanding of water and energy partitioning at the land-atmosphere interface. The objective of this study is to mea...
Absolute evaporation rates of non-rotating neutral polycyclic aromatic hydrocarbon clusters
NASA Astrophysics Data System (ADS)
Montillaud, J.; Joblin, C.
Context. Clusters of polycyclic aromatic hydrocarbons (PAHs) have been proposed as candidates for evaporating very small grains, which are thought to be precursors of free-flying PAHs. Evaporation rates have been calculated so far only for species containing up to a few 100-C atoms, whereas interstellar PAH clusters could contain up to ~1000 C atoms. Aims: We present a method that generalises the calculation of the statistical evaporation rate of large PAH clusters and provides rates for species containing up to ~1000 C-atoms. Methods: The evaporation of non-rotating neutral homo-molecular PAH clusters containing up to 12 molecules from a family of highly symmetric compact PAHs is studied. Statistical calculations were performed and completed with molecular dynamics simulations at high internal energies to provide absolute values for the evaporation rate and distributions of kinetic energy released. The calculations used explicit atom-atom Lennard-Jones potentials in the rigid molecule approximation. A new method is proposed to take both inter- and intra-molecular vibrations into account. Results: Without any parameter adjustment, the calculated evaporation rates agree well with available experimental data. We find that the non-rotation assumption has a limited impact on the evaporation rates. The photostability of PAH clusters increases dramatically with the size of molecules in the clusters, and to a lesser extent with the number of molecules in the clusters. For values of the UV radiation field that are typical of the regions where evaporating very small grains are observed, the smallest clusters in this study (~50 C-atoms) are found to be quickly photo-evaporated, whereas the largest clusters (~1000 C-atoms) are photostable. Conclusions: Our results support the idea that large PAH clusters are good candidates for evaporating very small grains.
KITANO M., HAMAKOGA M. and EGUCHI H. Physical evaluation of effective evaporative demand with reference to plant water relations. BIOTRONICS 19, 109-119, 1990. Evaporative demand on a transpiring leaf was evaluated by enŁ vironmental factors of radiation, ambient air temperature, humidity and wind velocity. Under different environmental conditions, a constant linear relationŁ ship was found between the evaluated evaporative demand
Effect of UV irradiation on the evaporation rate of alcohols droplets
NASA Astrophysics Data System (ADS)
Korobko, O. V.; Britan, A. V.; Verbinskaya, G. H.; Gavryushenko, D. A.
The effect of ultraviolet irradiation with a wavelength of 390 nm on the evaporation of droplets of the homologous series of alcohols ( n-propanol, n-butanol, n-pentanol, n-heptanol, n-octanol, and n-decanol) at 10, 30, 50, 100, and 200 mm Hg in an atmosphere of dry nitrogen is studied. The values of the evaporation rate of alcohols are calculated with and without irradiation. Starting from n-pentanol, the rate of evaporation grows strongly for droplets of higher alcohols under the effect of low-power irradiation not associated with the heating of the evaporating droplets of alcohols. The obtained results are analyzed by comparing them to experimental data on neutron scattering by alcohols. It is shown that free convection must be considered in order to describe the evaporation process. Expressions of different authors for describing this effect are analyzed.
Contrasting the Evaporation and Condensation of Water from Glassy and Amorphous Aerosol Particles
NASA Astrophysics Data System (ADS)
Reid, J. P.; Bones, D. L.; Power, R.; Lienhard, D.; Krieger, U. K.
The partitioning of water between the condensed and gas phases in atmospheric aerosol is usually assumed to occur instantaneously and to be regulated by solution thermodynamics. However, the persistence of high viscosity, glassy and amorphous aerosol to low relative humidity without crystallisation occurring is now widely recognised, suggesting that the timescale for water transport to or from the particle during condensation or evaporation may be significant. A kinetic limitation on water transport could have important implications for understanding hygroscopic growth measurements made on ambient particles, the ability of particles to act as ice nuclei or cloud condensation nuclei, the kinetics of chemical aging/heterogeneous chemistry, and the rate or condensation/evaporation of semi-volatile organic components. In this study we will report on measurements of the timescale of water transport to and from glassy aerosol and ultra-high viscosity solution droplets using aerosol optical tweezers to investigate the time-response of single particles to changes in relative humidity. As a benchmark system, mixed component aerosol particles containing sucrose and sodium chloride have been used; varying the mole fractions of the two solutes allows a wide range of solution viscosities to be studied. We will show that coarse particles can take many thousands of seconds to equilibrate in size and that the timescale correlates with the estimated bulk viscosity of the particle. We will also confirm that significant inhomogeneities in particle composition can be established during evaporation or condensation. Using the experimental data to benchmark a model for equilibration time, predictions can be made of the timescale for the equilibration of accumulation mode particles during water condensation or evaporation and these predictions will be described and their significance explored. Finally, the coalescence dynamics of highly viscous aerosol particles will be reported, reporting for the first time the timescale required for coalesced particles to relax to an equilibrium morphology and size.
Biology 390 Problem: Evaporative Water Loss and Temp Reg. thanks to Dr. J.F. Anderson,
Prestwich, Ken
by evaporative cooling during one day by a 70 kg mammal whose rate of metabolism is 3,000 Kcal/day. Assume evaporative cooling is the only mode of heat exchange this mammal can use to regulate its body temperature, i need rely less on evaporative cooling. Provided that they have an effective way to reduce respiratory
Theoretical investigation of the injection and evaporation of water in a hydrogen/oxygen steam generator
NASA Astrophysics Data System (ADS)
Beer, Stefan
Water is injected into the gas stream for the purpose of cooling the reaction products resulting from the stochiometric combustion of hydrogen with oxygen. The penetration of the jet decisively influences the temperature profile across the flow cross section in the water vapor. The penetration of the water jet into the stream is calculated using the jet shedding model and compared with the garden hose model. Models for the evaporation of water droplets in superheated steam are developed for calculating the evaporation paths. The parameters which influence the injection and evaporation process are subjected to variation and their effects in the evaporation paths are analyzed.
Role of transpiration suppression by evaporation of intercepted water in improving irrigation efficiency
J. A. Tolk; T. A. Howell; J. L. Steiner; D. R. Krieg; A. D. Schneider
Sprinkler irrigation efficiency declines when applied water intercepted by the crop foliage, or gross interception (Igross), as well as airborne droplets and ponded water at the soil surface evaporate before use by the crop. However, evaporation of applied water can also supply some of the atmospheric demands usually met by plant transpiration. Any suppression of crop transpiration from the irrigated
High Rate Preparation of aSi:H by Reactive Evaporation Method
Masanari Shindo; Shigeru Sato; Isao Myokan; Shigeru Mano; Takuji Shibata
A high rate deposition method of a-Si: H based on reactive evaporation is described. a-Si: H prepared at a deposition rate of 30 ┼\\/sec has much the same photoconductivity as films prepared by the glow discharge (GD) method. It is revealed that silicon oxidation due to residual oxygen gas is suppressed using a method of silicon evaporation to supply hydrogen
Evaporation of water from sodium chloride solutions under controlled climatic conditions
Moore, Jaroy
nations 21 IV EXPERIMENTAL RESULTS 23 A. Evaporation Investigations B. Physical Model for Evaporation l. Evaporation rates 2. Vapor pressure of the solution 3. Vapor pressure of the air 4. Constant for wind speed C. Statistical Model... for Evaporation 23 27 27 27 28 28 34 D. Relation Between the Statistical and Physical Models 37 E. Effects of the Variables Employed l. Air temperature'e 2. Relative humidity 3 ~ Wind speed 4. Salt concentration 38 39 40 41 Chapter F. Reduction...
Evaporation Loss of Light Elements as a Function of Cooling Rate: Logarithmic Law
NASA Technical Reports Server (NTRS)
Xiong, Yong-Liang; Hewins, Roger H.
Knowledge about the evaporation loss of light elements is important to our understanding of chondrule formation processes. The evaporative loss of light elements (such as B and Li) as a function of cooling rate is of special interest because recent investigations of the distribution of Li, Be and B in meteoritic chondrules have revealed that Li varies by 25 times, and B and Be varies by about 10 times. Therefore, if we can extrapolate and interpolate with confidence the evaporation loss of B and Li (and other light elements such as K, Na) at a wide range of cooling rates of interest based upon limited experimental data, we would be able to assess the full range of scenarios relating to chondrule formation processes. Here, we propose that evaporation loss of light elements as a function of cooling rate should obey the logarithmic law.
Milagro limits and HAWC sensitivity for the rate-density of evaporating primordial black holes
Abdo, A. A.; Abeysekara, A. U.; Alfaro, R.; Allen, B. T.; Alvarez, C.; ┴lvarez, J. D.; Arceo, R.; Arteaga-Velßzquez, J. C.; Aune, T.; Ayala Solares, H. A.; et al
Primordial Black Holes (PBHs) are gravitationally collapsed objects that may have been created by density fluctuations in the early universe and could have arbitrarily small masses down to the Planck scale. Hawking showed that due to quantum effects, a black hole has a temperature inversely proportional to its mass and will emit all species of fundamental particles thermally. PBHs with initial masses of ~ 5.0 ū 10╣? g should be expiring in the present epoch with bursts of high-energy particles, including gamma radiation in the GeV ¢ TeV energy range. The Milagro high energy observatory, which operated from 2000 tomoreĀ╗2008, is sensitive to the high end of the PBH evaporation gamma-ray spectrum. Due to its large field-of-view, more than 90% duty cycle and sensitivity up to 100 TeV gamma rays, the Milagro observatory is well suited to perform a search for PBH bursts. Based on a search on the Milagro data, we report new PBH burst rate density upper limits over a range of PBH observation times. In addition, we report the sensitivity of the Milagro successor, the High Altitude Water Cherenkov (HAWC) observatory, to PBH evaporation events.½Āless
Treatment of a waste oil-in-water emulsion from a copper-rolling process by ultrafiltration and vacuum evaporation.
Gutiķrrez, Gemma; Lobo, Alberto; Benito, Josķ M; Coca, Josķ; Pazos, Carmen
A process is proposed for the treatment of a waste oil-in-water (O/W) emulsion generated in an industrial copper-rolling operation. The use of demulsifier agents improves the subsequent treatment by techniques such as ultrafiltration (UF) or evaporation. The effluent COD is reduced up to 50% when the O/W emulsion is treated by UF using a flat 30 nm TiO(2) ceramic membrane (?P = 0.1 MPa) and up to 70% when it is treated by vacuum evaporation, after an emulsion destabilization pretreatment in both cases. Increases in the UF permeate flux and in the evaporation rate are observed when a chemical demulsifier is used in the pretreatment step. A combined process consisting of destabilization/settling, UF, and vacuum evaporation can yield a very high-quality aqueous effluent that could be used for process cooling or emulsion reformulation. PMID:21112152
Evaluation of the correlations for predicting evaporative loss from water body
Yilmaz, T.P.; Aybar, H.S.
Water evaporation (evaporation from here on) is a natural phenomenon that is important for system design and system safety in many engineering branches. Indeed, evaporative heat and mass loss are observed and calculated in very diverse situations, such as irrigation plants, water purification plants, cooling ponds, lakes, dams, swimming pools, health spas, management of liquid wastes as in evaporation pools, and spent fuel pools in nuclear power plants. There are a number of correlations obtained from experimental studies that predict the evaporative heat and mass loss from a water body. This study aims to summarize and to compare the existing evaporation correlations to determine the upper and lower bounding correlations for use in various thermal-hydraulic analyses of systems. Currently and widely used, six correlations found in the literature have been selected and tested using the major parameters of evaporation such as water temperature, air relative humidity, air velocity, and temperature. The comparison test cases show that ASHRAE (1991) and Ryan et al. (1974) equations result in the highest evaporative loss, while the Brady et al. (1969) equation provides the lowest evaporative loss in most conditions. Engineering designers may sometimes need the upper bound value of evaporative loss or sometimes the lower bound value for a conservative calculation. The authors conclude that using a single equation does not provide the conservative calculation for every situation and show which correlation gives the lower or upper bound for different conditions.
Influence of surface wettability on transport mechanisms governing water droplet evaporation.
Pan, Zhenhai; Weibel, Justin A; Garimella, Suresh V
Prediction and manipulation of the evaporation of small droplets is a fundamental problem with importance in a variety of microfluidic, microfabrication, and biomedical applications. A vapor-diffusion-based model has been widely employed to predict the interfacial evaporation rate; however, its scope of applicability is limited due to incorporation of a number of simplifying assumptions of the physical behavior. Two key transport mechanisms besides vapor diffusion-evaporative cooling and natural convection in the surrounding gas-are investigated here as a function of the substrate wettability using an augmented droplet evaporation model. Three regimes are distinguished by the instantaneous contact angle (CA). In Regime I (CA ? 60░), the flat droplet shape results in a small thermal resistance between the liquid-vapor interface and substrate, which mitigates the effect of evaporative cooling; upward gas-phase natural convection enhances evaporation. In Regime II (60 ? CA ? 90░), evaporative cooling at the interface suppresses evaporation with increasing contact angle and counterbalances the gas-phase convection enhancement. Because effects of the evaporative cooling and gas-phase convection mechanisms largely neutralize each other, the vapor-diffusion-based model can predict the overall evaporation rates in this regime. In Regime III (CA ? 90░), evaporative cooling suppresses the evaporation rate significantly and reverses entirely the direction of natural convection induced by vapor concentration gradients in the gas phase. Delineation of these counteracting mechanisms reconciles previous debate (founded on single-surface experiments or models that consider only a subset of the governing transport mechanisms) regarding the applicability of the classic vapor-diffusion model. The vapor diffusion-based model cannot predict the local evaporation flux along the interface for high contact angle (CA ? 90░) when evaporative cooling is strong and the temperature gradient along the interface determines the peak local evaporation flux. PMID:25105726
Sensible Heat Measurements Indicating Depth and Magnitude of Subsurface Soil Water Evaporation
Technology Transfer Automated Retrieval System (TEKTRAN)
Soil water evaporation is typically determined by techniques that assume the latent heat flux originates from the soil surface. Here, we describe a new technique for determining in situ soil water evaporation dynamics from fine-scale measurements of soil temperature and thermal properties with heat ...
Interfacial conditions during evaporation or condensation of water C. A. Ward* and D. Stanga
Ward, Charles A.
Interfacial conditions during evaporation or condensation of water C. A. Ward* and D. Stanga manuscript received 15 June 2001; published 29 October 2001 Steady-state evaporation and condensation experiments have been conducted with water under conditions where buoyancy-driven convection is not present
Performance of constructed evaporation ponds for disposal of smelter waste water
S. A Salzman; G Allinson; F Stagnitti; M Coates; R. J Hill
The construction of evaporative ponds and wetlands for the disposal of waste water high in ionic concentrations is a waste disposal strategy currently considered by many industries. However, the design, construction and management of these ponds and wetlands are not straightforward as complex chemical interactions result in both spatial and temporal changes in water quality. The effects of evaporation and
Scaling up nanoscale water-driven energy conversion into evaporation-driven engines and generators.
Chen, Xi; Goodnight, Davis; Gao, Zhenghan; Cavusoglu, Ahmet H; Sabharwal, Nina; DeLay, Michael; Driks, Adam; Sahin, Ozgur
Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth's climate. Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world. Here, we report evaporation-driven engines that can power common tasks like locomotion and electricity generation. These engines start and run autonomously when placed at air-water interfaces. They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations. Using these engines, we demonstrate an electricity generator that rests on water while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1?kg) that moves forward as the water in the car evaporates. Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment. PMID:26079632
Scaling up nanoscale water-driven energy conversion into evaporation-driven engines and generators
Chen, Xi; Goodnight, Davis; Gao, Zhenghan; Cavusoglu, Ahmet H.; Sabharwal, Nina; DeLay, Michael; Driks, Adam; Sahin, Ozgur
Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth's climate. Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world. Here, we report evaporation-driven engines that can power common tasks like locomotion and electricity generation. These engines start and run autonomously when placed at air¢water interfaces. They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations. Using these engines, we demonstrate an electricity generator that rests on water while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1?kg) that moves forward as the water in the car evaporates. Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment. PMID:26079632
Bioheat model evaluations of laser effects on tissues: role of water evaporation and diffusion
NASA Astrophysics Data System (ADS)
Nagulapally, Deepthi; Joshi, Ravi P.; Thomas, Robert J.
A two-dimensional, time-dependent bioheat model is applied to evaluate changes in temperature and water content in tissues subjected to laser irradiation. Our approach takes account of liquid-to-vapor phase changes and a simple diffusive flow of water within the biotissue. An energy balance equation considers blood perfusion, metabolic heat generation, laser absorption, and water evaporation. The model also accounts for the water dependence of tissue properties (both thermal and optical), and variations in blood perfusion rates based on local tissue injury. Our calculations show that water diffusion would reduce the local temperature increases and hot spots in comparison to simple models that ignore the role of water in the overall thermal and mass transport. Also, the reduced suppression of perfusion rates due to tissue heating and damage with water diffusion affect the necrotic depth. Two-dimensional results for the dynamic temperature, water content, and damage distributions will be presented for skin simulations. It is argued that reduction in temperature gradients due to water diffusion would mitigate local refractive index variations, and hence influence the phenomenon of thermal lensing. Finally, simple quantitative evaluations of pressure increases within the tissue due to laser absorption are presented.
Mathematical modeling of evaporative cooling of water films in water-cooling towers
A. I. Petruchik; S. P. Fisenko
A mathematical model of evaporative cooling of water films flowing down vertical guards in a chimney-type water-cooling tower\\u000a is developed. Results of a qualitative analysis of the nonlinear mathematical model are reported. Data obtained from a numerical\\u000a solution of a boundary-value problem for a system of ordinary differential equations are presented in the form of graphs.
High rate deposition of transparent conducting oxide thin films by vacuum arc plasma evaporation
Tadatsugu Minami; Satoshi Ida; Toshihiro Miyata
Transparent conducting oxide (TCO) thin films have been deposited at a high rate above 370 nm\\/min by vacuum arc plasma evaporation (VAPE) using sintered oxide fragments as the source material. It was found that the deposition rate of TCO films was strongly dependent on the deposition pressure, whereas the obtained electrical properties were relatively independent of the pressure. Resistivities of
Measurement of the evaporation mass flow rate in a horizontal liquid layer partly opened into flowing gas
NASA Astrophysics Data System (ADS)
Lyulin, Yu. V.; Kabov, O. A.
The dynamics of evaporation from a local surface of a horizontal liquid layer under a gas flow is studied experimentally. The average evaporation mass flow rate of a liquid layer (HFE-7100) induced by inert gas (nitrogen) is measured using two independent methods. The influence of the average gas flow rate, gas and liquid temperature, and the layer depth upon the evaporation rate and convection in the liquid layer is investigated. Correlation dependences of the evaporation rate vs. the inert gas flow rate and temperature are obtained. It is found that the average evaporation-rate curve has a local maximum with a growth of the liquid layer depth. With the growth of the gas and liquid temperature, the local maximum in an evaporation flow rate of the liquid layer is shifted to the larger value of the liquid depth.
Modeling Evaporation-Seepage Losses for Reservoir Water Balance in Semi-arid Regions
C. Sivapragasam; G. Vasudevan; J. Maran; C. Bose; S. Kaza; N. Ganesh
In the water balance of reservoir system, evaporation plays a crucial role particularly so for the reservoir systems of smaller\\u000a size located in the semi-arid or arid regions. Such regions are most often characterized by significant seepage losses from\\u000a reservoirs, besides evaporation losses. Usually, in the optimization of a reservoir system, it is a common practice to assume\\u000a evaporation loss
Changing Demands from Riparian Evapotranspiration and Free-Water Evaporation in the Lower Colorado River Basin Under Different Climate Scenarios
NASA Astrophysics Data System (ADS)
Bunk, D. A.; Piechota, T. C.
Observed and projected trends in riparian evapotranspiration (ET) and free-water evaporation are examined to improve water demand forecasting for use in modeling of lower Colorado River system reservoir operations. While most previous research has focused on the impacts of climate change and climate variability on water supply, the impacts on water demand under changing climate conditions have not been adequately addressed (NRC, 2007 and Reclamation, 2009). Increases in temperatures and changes in precipitation and wind patterns are expected to increase evaporative demands (Bates and others, 2008), potentially increasing free-water evaporation and ET from riparian vegetation; increasing infiltration rates; altering cropping patterns; and changing the temporal and spatial distribution of water deliveries. This study uses observations and projections under changing climate scenarios of hydroclimatic variables, such as temperature, wind, and precipitation, to analyze their impacts on riparian ET and free-water evaporation in the lower Colorado River mainstream downstream of Lake Mead and Hoover Dam. The projected changes in evaporative demands were assessed to determine their impacts on water supply and reservoir operations in the Colorado River basin under changing climate conditions. Based on analysis of observed and projected hydroclimatic data from the Variable Infiltration Capacity (VIC) hydrologic model, mean annual daily temperature in the lower Colorado River mainstream reach has increased by 0.8░ Celsius (C) from the 30-year period ending in 1980 to period ending in 2010 and is projected to increase by an additional 1.7░ C by 30-year period ending in 2060. Analysis of riparian ET derived from the ASCE Penman-Monteith method (Allen et al., 2005, from Monteith, 1965 and 1981) and Westenburg et al. (2006) and free-water evaporation derived from the Penman combination model in Dingman (2008) indicates that combined evaporative demand in the lower Colorado River mainstream increased by 14,800 acre-feet, or 1.8 percent, during the 30-year period ending in 2010, and may increase by an additional 16,600 acre-feet, or 2.0 percent, during the 30-year period ending in 2060, when compared to the period from 1951 to 1980. With this projected increase in evaporative demands, the combined storage of Lake Powell and Lake Mead are projected to decrease by a cumulative volume of 75,400 acre-feet, or 0.15 percent of total conservation capacity, based on 10-year running averages ending in years 2020 to 2060. In addition, average annual shortage volumes in the lower Colorado River basin are projected to increase by 40,000 acre-feet, or 0.30 percent, from 2013 to 2060.
Thermal and Hydrologic Signatures of Soil Controls on Evaporation: A Combined Energy and Water Balance Approach with Implications for Remote Sensing of Evaporation
NASA Technical Reports Server (NTRS)
Salvucci, Guido D.
The overall goal of this research is to examine the feasibility of applying a newly developed diagnostic model of soil water evaporation to large land areas using remotely sensed input parameters. The model estimates the rate of soil evaporation during periods when it is limited by the net transport resulting from competing effects of capillary rise and drainage. The critical soil hydraulic properties are implicitly estimated via the intensity and duration of the first stage (energy limited) evaporation, removing a major obstacle in the remote estimation of evaporation over large areas. This duration, or "time to drying" (t(sub d)), is revealed through three signatures detectable in time series of remote sensing variables. The first is a break in soil albedo that occurs as a small vapor transmission zone develops near the surface. The second is a break in either surface to air temperature differences or in the diurnal surface temperature range, both of which indicate increased sensible heat flux (and/or storage) required to balance the decrease in latent heat flux. The third is a break in the temporal pattern of near surface soil moisture. Soil moisture tends to decrease rapidly during stage 1 drying (as water is removed from storage), and then become more or less constant during soil limited, or "stage 2" drying (as water is merely transmitted from deeper soil storage). The research tasks address: (1) improvements in model structure, including extensions to transpiration and aggregation over spatially variable soil and topographic landscape attributes; and (2) applications of the model using remotely sensed input parameters.
Effects of water vapor density on cutaneous resistance to evaporative water loss and body temperature in green tree frogs (Hyla cinerea).
Wygoda, Mark L; Kersten, Constance A
Increased cutaneous resistance to evaporative water loss (Rc) in tree frogs results in decreased water loss rate and increased body temperature. We examined sensitivity of Rc to water vapor density (WVD) in Hyla cinerea by exposing individual frogs and agar models to four different WVD environments and measuring cutaneous evaporative water loss rate and body temperature simultaneously using a gravimetric wind tunnel measuring system. We found that water loss rate varied inversely and body temperature directly with WVD but that models were affected to a greater extent than were animals. Mean Rc was significantly different between the highest WVD environment and each of the three drier environments but did not differ among the drier environments, indicating that Rc initially increases and then reaches a plateau in response to decreasing WVD. Rc was equivalent when calculated using either WVD difference or WVD deficit as the driving force for evaporation. We also directly observed secretions from cutaneous glands while measuring body temperature and tested secretions and skin samples for the presence of lipids. We found that irregular transient body temperature depressions observed during wind tunnel trials occur due to evaporative cooling from intermittent skin secretions containing lipids, although we were unable to identify lipid-secreting glands. PMID:23995486
Floatable, Self-Cleaning, and Carbon-Black-Based Superhydrophobic Gauze for the Solar Evaporation Enhancement at the Air-Water Interface.
Liu, Yiming; Chen, Jingwei; Guo, Dawei; Cao, Moyuan; Jiang, Lei
Efficient solar evaporation plays an indispensable role in nature as well as the industry process. However, the traditional evaporation process depends on the total temperature increase of bulk water. Recently, localized heating at the air-water interface has been demonstrated as a potential strategy for the improvement of solar evaporation. Here, we show that the carbon-black-based superhydrophobic gauze was able to float on the surface of water and selectively heat the surface water under irradiation, resulting in an enhanced evaporation rate. The fabrication process of the superhydrophobic black gauze was low-cost, scalable, and easy-to-prepare. Control experiments were conducted under different light intensities, and the results proved that the floating black gauze achieved an evaporation rate 2-3 times higher than that of the traditional process. A higher temperature of the surface water was observed in the floating gauze group, revealing a main reason for the evaporation enhancement. Furthermore, the self-cleaning ability of the superhydrophobic black gauze enabled a convenient recycling and reusing process toward practical application. The present material may open a new avenue for application of the superhydrophobic substrate and meet extensive requirements in the fields related to solar evaporation. PMID:26027770
Single-droplet evaporation kinetics and particle formation in an acoustic levitator. Part 1: evaporation of water microdroplets assessed using boundary-layer and acoustic levitation theories.
Schiffter, Heiko; Lee, Geoffrey
The suitability of a single droplet drying acoustic levitator as a model for the spray drying of aqueous, pharmaceutically-relevant solutes used to produce protein-loaded particles has been examined. The acoustic levitator was initially evaluated by measuring the drying rates of droplets of pure water in dependence of drying-air temperature and flow rate. The measured drying rates were higher than those predicted by boundary layer theory because of the effects of primary acoustic streaming. Sherwood numbers of 2.6, 3.6, and 4.4 at drying-air temperatures of 25 degrees C, 40 degrees C, and 60 degrees C were determined, respectively. Acoustic levitation theory could predict the measured drying rates and Sherwood numbers only when a forced-convection drying-air stream was used to neuralize the retarding effect of secondary acoustic streaming on evaporation rate. At still higher drying-air flow rates, the Ranz-Marshall correlation accurately predicts Sherwood number, provided a stable droplet position in the standing acoustic wave is maintained. The measured Sherwood numbers and droplet Reynolds numbers show that experiments performed in the levitator in still air are taking place effectively under conditions of substantial forced convection. The similitude of these values to those occurring in spray dryers is fortuitous for the suitability of the acoustic levitator as a droplet evaporation model for spray drying. PMID:17582811
Evaporation rates of freely falling liquid nitrogen droplets in air
Awonorin, S.O.
The rates of heat transfer to individual droplets of liquid nitrogen falling freely in air were measured under different air temperatures similar to the conditions in a cryogenic freezing system. High-speed cinephotography was used to measure drop size and velocity. Experimental results of heat transfer rates to individual droplets were analyzed and the data were compared to those obtainable using other types of dimensionless correlations. Droplets of initial size range investigated (2.5-0.72 mm diameter) attained terminal velocities at distances of 4-6 cm freefall away from the drop generator tip. The velocity values used in the correlation of heat transfer data were averaged over the time traveled by individual droplet.
Influence of condensate evaporation on water vapor and its stable isotopes in a GCM
Jonathon S. Wright; Adam H. Sobel; Gavin A. Schmidt
The direct effect of condensate evaporation on atmo- spheric water vapor and its isotopic composition is assessed in a climate model. The model contains two parallel hy- drologic cycles, an active one which influences the model physics and dynamics and a passive one which does not. Two model simulations are performed, one in which passive cloud and precipitation can evaporate
Indirect evaporative cooling potential in air¢water systems in temperate climates
Ben Costelloe; Donal Finn
Recent developments have prompted a review of evaporative cooling technology as an effective means of cooling modern deep plan buildings. Prominent among these developments is the success of high temperature sensible cooling systems, particularly, chilled ceilings, which require a supply of cooling water at 14¢18░C. Crucial to the success of evaporative cooling technology, as a significant means of cooling in
Reduction of water evaporation in polymerase chain reaction microfluidic devices based on oscillating-flow
Polini, Alessandro; Mele, Elisa; Sciancalepore, Anna Giovanna; Girardo, Salvatore; Biasco, Adriana; Camposeo, Andrea; Cingolani, Roberto; Weitz, David A.; Pisignano, Dario
Producing polymeric or hybrid microfluidic devices operating at high temperatures with reduced or no water evaporation is a challenge for many on-chip applications including polymerase chain reaction (PCR). We study sample evaporation in polymeric and hybrid devices, realized by glass microchannels for avoiding water diffusion toward the elastomer used for chip fabrication. The method dramatically reduces water evaporation in PCR devices that are found to exhibit optimal stability and effective operation under oscillating-flow. This approach maintains the flexibility, ease of fabrication, and low cost of disposable chips, and can be extended to other high-temperature microfluidic biochemical reactors. PMID:20877657
Emergent relation between surface vapor conductance and relative humidity profiles yields evaporation rates from weather data.
Salvucci, Guido D; Gentine, Pierre
The ability to predict terrestrial evapotranspiration (E) is limited by the complexity of rate-limiting pathways as water moves through the soil, vegetation (roots, xylem, stomata), canopy air space, and the atmospheric boundary layer. The impossibility of specifying the numerous parameters required to model this process in full spatial detail has necessitated spatially upscaled models that depend on effective parameters such as the surface vapor conductance (C(surf)). C(surf) accounts for the biophysical and hydrological effects on diffusion through the soil and vegetation substrate. This approach, however, requires either site-specific calibration of C(surf) to measured E, or further parameterization based on metrics such as leaf area, senescence state, stomatal conductance, soil texture, soil moisture, and water table depth. Here, we show that this key, rate-limiting, parameter can be estimated from an emergent relationship between the diurnal cycle of the relative humidity profile and E. The relation is that the vertical variance of the relative humidity profile is less than would occur for increased or decreased evaporation rates, suggesting that land-atmosphere feedback processes minimize this variance. It is found to hold over a wide range of climate conditions (arid-humid) and limiting factors (soil moisture, leaf area, energy). With this relation, estimates of E and C(surf) can be obtained globally from widely available meteorological measurements, many of which have been archived since the early 1900s. In conjunction with precipitation and stream flow, long-term E estimates provide insights and empirical constraints on projected accelerations of the hydrologic cycle. PMID:23576717
Evaporation rate and composition monitoring of electron beam PVD processes
Anklam, T.M.; Berzins, L.V.; Braun, D.G.; Haynam, C.; Meier, T.; McClelland, M.A.
Lawrence Livermore National Laboratory (LLNL) is developing sensor and control technology to improve the quality and range of applicability of electron beam PVD. The approach being developed uses tunable lasers to measure, the density and composition of the vapor plume. This paper reviews the principles of operation of laser based sensors and discusses data from experiments in which titanium and niobium are co-vaporized. Laser data agreed well with deposited film compositions and spatial variations in deposited film cross sections. Laser based vapor monitoring appears to have broad applicability and has the potential to extend the use of high rate electron beam PVD.
Impacts of Evaporation from Saline Soils on Soil Hydraulic Properties and Water Fluxes
NASA Astrophysics Data System (ADS)
Fierro, V.; Hernandez, M. F.; Braud, I.; Cristi Matte, F.; Hausner, M. B.; Suarez, F. I.; Munoz, J.
Saline soils are common in arid zones, where evaporation from shallow groundwater is generally the major component of the water balance. Thus, accurate quantification of soil water evaporation is crucial to improve water resource management in these regions. Evaporation from saline soils is a complex process that couples the movement of salts, heat, liquid water and water vapor. Precipitation/dissolution reactions can alter the soil structure and modify flow paths. The impact of evaporation from shallow groundwater on soil properties and water fluxes poses a major hydrologic challenge that remains to be answered. As a preliminary approach to consider these effects, we used the SiSPAT model (Simple Soil Plant Atmospheric Transfer) to represent the movement of liquid water and water vapor in a saline soil column subjected to two groundwater levels under nonisothermal conditions. To parameterize the model, we determined the hydraulic properties of the soil before performing the soil column experiments. When the SiSPAT model was run using uniform and constant hydraulic properties, it was unable to predict the moisture and thermal profiles, or the cumulative evaporation. This inability to reproduce the observed data is most likely due to alterations of the soil structure as a result of precipitation/dissolution reactions. When the soil hydraulic properties were allowed to vary in space, the model reproduced the experimental data successfully, suggesting that the structure of the initially homogeneous soil column was modified. It is thus necessary to incorporate salt precipitation to correctly simulate evaporation in saline soils.
Use of Air2Air Technology to Recover Fresh-Water from the Normal Evaporative Cooling Loss at Coal-Based Thermoelectric Power Plants
Ken Mortensen
This program was undertaken to build and operate the first Air2Air{trademark} Water Conservation Cooling Tower at a power plant, giving a validated basis and capability for water conservation by this method. Air2Air{trademark} water conservation technology recovers a portion of the traditional cooling tower evaporate. The Condensing Module provides an air-to-air heat exchanger above the wet fill media, extracting the heat from the hot saturated moist air leaving in the cooling tower and condensing water. The rate of evaporate water recovery is typically 10%-25% annually, depending on the cooling tower location (climate).
Impact of Reservoir Evaporation and Evaporation Suppression on Water Supply CapabilitiesĀ
Ayala, Rolando A
Reservoir storage is essential for developing dependable water supplies and is a major component of the river system water budget. The storage contents of reservoirs fluctuate greatly with variations in water use and ...
Evaporation measurements by eddy covariance from an urban tropical water reservoir
E. Velasco; M. Roth
One of the major problems in the management of water reservoirs is the accurate estimation of water loss by evaporation. This is particularly true for countries where the water supply relies on imported and recycled water, seawater desalination, and rainfall collected in reservoirs, such as Singapore. Within this context, an eddy covariance system was deployed on the shore of an
NRMRL-CIN-0988 Smith*, R.L. Predicting Evaporation Rates and Times for Spills of Chemical Mixtures. The Annals of Occupational Hygiene (Ogden, T. (Ed.), Elsevier) 45 (6):437-445 (2001). EPA/600/J-00/125. 03/16/2000 Spreadsheet and short-cut methods have been developed for p...
Reservoir evaporation in Texas, USA
NASA Astrophysics Data System (ADS)
Wurbs, Ralph A.; Ayala, Rolando A.
The role of reservoir surface evaporation in river/reservoir water budgets and water management is explored using a modeling system that combines historical natural hydrology with current conditions of water resources development and management. The long-term mean evaporation from the 3415 reservoirs in the Texas water rights permit system is estimated to be 7.53 billion m3/year, which is equivalent to 61% of total agricultural or 126% of total municipal water use in the state during the year 2010. Evaporation varies with the hydrologic conditions governing reservoir surface areas and evaporation rates. Annual statewide total evaporation volumes associated with exceedance probabilities of 75%, 50%, and 25% are 7.07, 7.47, and 7.95 billion m3/year, respectively. Impacts of evaporation are greatest during extended severe droughts that govern water supply capabilities.
Spacesuit Water Membrane Evaporator; An Enhanced Evaporative Cooling System for the Advanced Extravehicular Mobility Unit Portable Life Support System
NASA Technical Reports Server (NTRS)
Bue, Grant C.; Makinen, Janice V.; Miller, Sean; Campbell, Colin; Lynch, Bill; Vogel, Matt; Craft, Jesse; Wilkes, Robert; Kuehnel, Eric
Development of the Advanced Extravehicular Mobility Unit (AEMU) portable life support subsystem (PLSS) is currently under way at NASA Johnson Space Center. The AEMU PLSS features a new evaporative cooling system, the Generation 4 Spacesuit Water Membrane Evaporator (Gen4 SWME). The SWME offers several advantages when compared with prior crewmember cooling technologies, including the ability to reject heat at increased atmospheric pressures, reduced loop infrastructure, and higher tolerance to fouling. Like its predecessors, Gen4 SWME provides nominal crew member and electronics cooling by flowing water through porous hollow fibers. Water vapor escapes through the hollow fiber pores, thereby cooling the liquid water that remains inside of the fibers. This cooled water is then recirculated to remove heat from the crew member and PLSS electronics. Test results from the backup cooling system which is based on a similar design and the subject of a companion paper, suggested that further volume reductions could be achieved through fiber density optimization. Testing was performed with four fiber bundle configurations ranging from 35,850 fibers to 41,180 fibers. The optimal configuration reduced the Gen4 SWME envelope volume by 15% from that of Gen3 while dramatically increasing the performance margin of the system. A rectangular block design was chosen over the Gen3 cylindrical design, for packaging configurations within the AEMU PLSS envelope. Several important innovations were made in the redesign of the backpressure valve which is used to control evaporation. A twin-port pivot concept was selected from among three low profile valve designs for superior robustness, control and packaging. The backpressure valve motor, the thermal control valve, delta pressure sensors and temperature sensors were incorporated into the manifold endcaps, also for packaging considerations. Flight-like materials including a titanium housing were used for all components. Performance testing of the Gen4 SWME is underway.
Comparison of techniques for estimating evaporation from an irrigation water storage
NASA Astrophysics Data System (ADS)
McJannet, D. L.; Cook, F. J.; Burn, S.
With the emergence of water supply and food security issues as a result of increasing population and climate change pressures, the need for efficient use of available water supplies is paramount. Management of available resources and improved efficiency require accurate specification of evaporation, which is a major water loss pathway, yet evaporation remains difficult to accurately quantify. This study uses scintillometry-derived measurements of evaporation to test the performance of water balance, pan coefficient, and combination modeling techniques, which might commonly be used by resource managers. Both pan coefficient and water balance techniques performed poorly, but the Penman-Monteith model with local site data and site-specific wind function produced estimates within 2% of those measured. Recognizing that such a model parameterization would rarely be a possibility in most environments, further testing involving the range of data sets that might be available for a location was undertaken. Modeling using over-water measurements and, generally, applicable wind functions from the literature produced estimates 26% greater than those measured. Estimates within 12% of those measured were made for the equivalent model setup using over-land meteorological data; however, when data from the nearest meteorological station was used, this difference increased to 27%. The different evaporation estimation techniques tested were shown to produce a range of estimates of water availability, which varied by nearly 30%. The large differences between measured and predicted evaporation highlight the uncertainty that still exists in evaporation estimation and the sensitivity of predictions to the source of input data.
Cold {sup 52}Cr elastic and inelastic collision-rate determination using evaporative cooling analysis
Nguyen, Scott V.; Carvalho, Robert de; Doyle, John M. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States)
Elastic and inelastic collision-rate constants of {sup 52}Cr in the temperature range of 20 mK to 1 K are inferred from the evaporative cooling of buffer gas loaded atomic chromium. Using a model that describes the dynamics of the trapped chromium cloud during evaporation, we find g{sub el}=2.15(+2.5,-1.2)x10{sup -10} cm{sup 3}/s and g{sub in}=1.36(+1.2,-0.7)x10{sup -12} cm{sup 3}/s, consistent with theory but in disagreement with previously reported measurements.
A Study of Mechanisms and Supression of Evaporation of Water from SoilsĀ
Wendt, C. W.
, polysaccharide-gum mixtures, oil-latex mixtures, fatty alcohols, and reflectance materials. Of these compounds, only crude oil and crude oil-cationic mixtures were effective in suppressing soil water evaporation significantly when applied to smooth Olton loam wet...
Insight into the molecular mechanism of water evaporation via the finite temperature string method
Musolino, Nicholas
The process of water's evaporation at its liquid/air interface has proven challenging to study experimentally and, because it constitutes a rare event on molecular time scales, presents a challenge for computer simulations ...
Rates of Water Loss and Estimates of Survival Time under Varying Humidity in Juvenile Snapping Turtles ( Chelydra serpentina )
Michael S. Finkler
Juvenile snapping turtles may be highly susceptible to dehydration during over- land movement because of their aquatic nature and large surface area to volume ratio. The present study examined the influence of body size and relative humidity on rates of evaporative water loss and estimates of survival time. Larger hatchlings had higher rates of evaporative water loss but longer survival
Potable water recovery for spacecraft application by electrolytic pretreatment/air evaporation
NASA Technical Reports Server (NTRS)
Wells, G. W.
A process for the recovery of potable water from urine using electrolytic pretreatment followed by distillation in a closed-cycle air evaporator has been developed and tested. Both the electrolytic pretreatment unit and the air evaporation unit are six-person, flight-concept prototype, automated units. Significantly extended wick lifetimes have been achieved in the air evaporation unit using electrolytically pretreated, as opposed to chemically pretreated, urine feed. Parametric test data are presented on product water quality, wick life, process power, maintenance requirements, and expendable requirements.
Quantifying the feedback of evaporation and transpiration rates to soil moisture dynamics and meteorological condition changes by a numerical model
NASA Astrophysics Data System (ADS)
Su, Ye; Shao, Wei; Vl?ek, LukßÜ; Langhammer, Jakub
Evapotranspiration drives the hydrological process through energy-driven water-phase changes between systems of soil-vegetation-atmosphere. Evapotranspiration performs a rather complex process attributable to the spatial and temporal variation of soil-vegetation-atmosphere system. For vegetation-covered land surfaces, the transpiration process is governed by the stomatal behavior and water uptake from the root zone, and evaporation is related with the interception of rainfall and radiation on the canopy and soil surface. This study is emphasized on describing the hydrological process and energy cycle in a basic hydrological response unit, a hillslope. The experimental hillslope is located in an experimental catchment of the Bohemian Forest Mountains' headwaters in the Czech Republic, where is mostly covered by dead Norway spruce forest (Picea abies) stands caused by balk beetle outbreak. High-frequency monitoring network of the hydro-climatic data, soil pore water pressure and soil temperature has been launched since 2012. To conceptualize the land-surface energy and water fluxes in a complex hillslope, a soil-vegetation-atmosphere transport (SVAT) model, coupled with a multi-phase soil physics process (i.e. the water, vapor and heat flow transport) is used. We selected an 8-week basis dataset from 2013 as a pilot for partitioning the evapotranspiration into three interactive components: transpiration (Et), canopy interception evaporation (Ei), and soil evaporation (Es), by using this numerical model. Within such model framework, the sensitive feedback of evapotranspiration rates to rainfall intensity, soil moisture, and solar radiation will be examined by conducting numerical experiments to better understand the mechanism of evapotranspiration process under various influencing factors. Such application study and followed numerical simulations provide a new path for quantifying the behaviors of the soil-vegetation-atmosphere system.
Combining the Penman-Monteith equation with measurements of surface temperature and reflectance to estimate evaporation rates of semiarid grassland
A. F. Rahman; J. C. Washburne; M. A. Weltz; W. P. Kustas
The Penman-Monteith equation is useful for computing evaporation rates of uniform surfaces, such as dense vegetation or bare soil. This equation becomes less useful for evaluation of evaporation rates at the regional scale, where surfaces are generally characterized by a patchy combination of vegetation and soil. This is particularly true in the arid and semi-arid regions of the world. The
Computerized engineering model for evaporative water cooling towers
J. E. Park; J. M. Vance; K. E. Cross; N. H. Van Wie
The evaporative cooling tower is often used to reject waste heat from industrial processes, especially power plants and chemical facilities. In particular, huge cooling towers are used for heat rejection from gaseous diffusion plants. The ability to analyze and\\/or predict the performance of these towers is an important process engineering function. A consistent physical model for crossflow and counterflow cooling
Hydroclimatology of Illinois: A comparison of monthly evaporation estimates based on atmospheric water balance and soil water balance
Pat Jen-Feng Yeh; Michelle Irizarry; Elfatih A. B. Eltahir
Here we describe the regional-scale hydrological cycle of Illinois, including both the land and atmospheric branches, using a data set on most of the hydrological variables, i.e., precipitation, streamflow, soil water content, snow depth, groundwater level, and atmospheric flux of water vapor. Since direct observations of evaporation are not available, two different approaches, soil water balance and atmospheric water balance,
Monitoring near surface soil water and associated dynamics of infiltration and evaporation fluxes
Technology Transfer Automated Retrieval System (TEKTRAN)
In-situ monitoring of soil water has the advantage of integrating the precipitation, evaporation history, and gradual changes in hydraulic properties on the aggregate response of the system, which is manifested as soil water storage. Near-surface soil water and temperature dynamics were monitored th...
Evaporative water losses of exercising sheep in neutral and hot climates
Paris-Sud XI, Universitķ de
Evaporative water losses of exercising sheep in neutral and hot climates T Othman KG Johnson, DW, Australia Hot climates require an accelerated water loss to allowed for thermoregulation (Rai et al, 1979, Trop Anim Hlth Prod, 11, 51-56). The water losses associated with locomotion should be greater
Influence of substrate heating on the evaporation dynamics of pinned water droplets.
Girard, Fabien; Antoni, Mickaļl
The dynamics of evaporating water droplets deposited on a heated substrate is investigated numerically. Droplets are pinned with a contact line radius of R = 1 mm. Evaporative mass flow and convection occurring inside the droplets are studied for different heating substrate sizes L S and heating temperatures T S. A simplified model neglecting hydrodynamics in air and evaporative cooling and assuming droplets to be spherical caps is simulated with a finite element method. A toruslike convective cell appears inside the droplets as evaporation takes place. For L S/ R > 1, the contact line is warmer than the apex of the droplets, and convection generates a downstream flow in the vicinity of the symmetry axis of the droplets. For L S/ R < 1, it is the apex that is warmer. Convection then generates an upstream flow. The overall evaporation time is described. It slows when L S/ R > 1. PMID:18823094
Performance of Water Recirculation Loop Maintenance Components for the Advanced Spacesuit Water Membrane Evaporator
NASA Technical Reports Server (NTRS)
Rector, Tony; Peyton, Barbara M.; Steele, John W.; Makinen, Janice; Bue, Grant C.; Campbell, Colin
Water loop maintenance components to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop have undergone a comparative performance evaluation with a recirculating control loop which had no water quality maintenance. Results show that periodic water maintenance can improve performance of the SWME. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage of this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing sublimator technology. The driver for the evaluation of water recirculation maintenance components was to enhance the robustness of the SWME through the leveraging of fluid loop management lessons learned from the International Space Station (ISS). A patented bed design that was developed for a United Technologies Aerospace System military application provided a low pressure drop means for water maintenance in the SWME recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance cycle included the use of a biocide delivery component developed for the ISS to introduce a biocide in a microgravity compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware.
Variation of Phreatic Evaporation of Bare Soil and Integration Application in Water Allocation in Shule Basin
NASA Astrophysics Data System (ADS)
Wang, Z.; Huang, P.; Gong, G.
Phreatic evaporation is a key element in regional water balance, but it is hardly measured directly. Recently the development of some new technologies brings new dawn to phreatic evaporation measurement, such as eddy covariance, remote sensing ET and so on. But the new technologies have no ability to connect to groundwater yet. Conventional groundwater balance equipment was set up in Shule basin in northwestern China, with located E97░01', N45░13' , altitude 1520m, annual average precipitation 61.8mm and annual evaporation 2600mm (pan 20cm). The experiment field contains 45 lysimeters (65cm diameter). 11 different water table depths are set in the lysimeters, which are 0.5m, 0.75m, 1.0m, 1.25m, 1.5m, 2.0m, 2.5m, 3.0m, 4.0m, 5.0m and 6.0m. The water table in the lysimeter is controlled by Marriott Bottle System. The evaporation and percolation is measured for three different soil types (silt sandy soil, loam soil and clay soil) in the 11 different water table depths. Based on the data from 2006 to 2010, the influences of atmosphere evaporation capacity, phreatic water depth and soil textures are analyzed. Empirical formulae for estimating phreatic evaporation are regressed. The fitting precision of the different formulae are evaluated. The results show that, fitting effect of common empirical formulae is good in Shule river basin. For the different soil types, fitting effect of silt soil is the best, while that of clay soil is relatively low. At last, formulae fitted in other areas and phreatic evaporation tests are summarized. The reasons of difference of fitted coefficients lie in three aspects: the range of depth of groundwater, choice of the value of water evaporation, method to optimize coefficients. Physical meaning of the coefficients in empirical formulae is analyzed. The features, fitting effect and notes in application of formulae are evaluated. The results are applied in water requirement calculation of ecological conservation Dunhuang Xihu Nature Reserve. Water sources, plant transpiration, and phreatic evaporation are simulated by the groundwater numerical model and the total ET of nature reserve is calculated. The supplementary water requirement is advanced. Key words: phreatic evaporation; empirical formulae; fitting precision; Shule river basin
Mechanical tuning of the evaporation rate of liquid on crossed fibers.
Boulogne, Franńois; Sauret, Alban; Soh, Beatrice; Dressaire, Emilie; Stone, Howard A
We investigate experimentally the drying of a small volume of perfectly wetting liquid on two crossed fibers. We characterize the drying dynamics for the three liquid morphologies that are encountered in this geometry: drop, column, and a mixed morphology, in which a drop and a column coexist. For each morphology, we rationalize our findings with theoretical models that capture the drying kinetics. We find that the evaporation rate significantly depends upon the liquid morphology and that the drying of the liquid column is faster than the evaporation of the drop and the mixed morphology for a given liquid volume. Finally, we illustrate that shearing a network of fibers reduces the angle between them, changes the morphology toward the column state, and therefore, enhances the drying rate of a volatile liquid deposited on it. PMID:25716158
Influence of organic films on the evaporation and condensation of water in aerosol
Davies, James F.; Miles, Rachael E. H.; Haddrell, Allen E.; Reid, Jonathan P.
Uncertainties in quantifying the kinetics of evaporation and condensation of water from atmospheric aerosol are a significant contributor to the uncertainty in predicting cloud droplet number and the indirect effect of aerosols on climate. The influence of aerosol particle surface composition, particularly the impact of surface active organic films, on the condensation and evaporation coefficients remains ambiguous. Here, we report measurements of the influence of organic films on the evaporation and condensation of water from aerosol particles. Significant reductions in the evaporation coefficient are shown to result when condensed films are formed by monolayers of long-chain alcohols [CnH(2n+1)OH], with the value decreasing from 2.4 ū 10?3 to 1.7 ū 10?5 as n increases from 12 to 17. Temperature-dependent measurements confirm that a condensed film of long-range order must be formed to suppress the evaporation coefficient below 0.05. The condensation of water on a droplet coated in a condensed film is shown to be fast, with strong coherence of the long-chain alcohol molecules leading to islanding as the water droplet grows, opening up broad areas of uncoated surface on which water can condense rapidly. We conclude that multicomponent composition of organic films on the surface of atmospheric aerosol particles is likely to preclude the formation of condensed films and that the kinetics of water condensation during the activation of aerosol to form cloud droplets is likely to remain rapid. PMID:23674675
Epiphyte Water Retention and Evaporation in Native and Invaded Tropical Montane Cloud Forests in Hawaii
NASA Astrophysics Data System (ADS)
Mudd, R. G.; Giambelluca, T. W.
Epiphyte water retention was quantified at two montane cloud forest sites in Hawai'i Volcanoes National Park, one native and the other invaded by an alien tree species. Water storage elements measured included all epiphytic mosses, leafy liverworts, and filmy ferns. Tree surface area was estimated and a careful survey was taken to account for all epiphytes in the sample area of the forest. Samples were collected and analyzed in the lab for epiphyte water retention capacity (WRC). Based on the volume of the different kinds of epiphytes and their corresponding WRC, forest stand water retention capacity for each survey area was estimated. Evaporation from the epiphyte mass was quantified using artificial reference samples attached to trees that were weighed at intervals to determine changes in stored water on days without significant rain or fog. In addition, a soil moisture sensor was wrapped in an epiphyte sample and left in the forest for a 6-day period. Epiphyte biomass at the Native Site and Invaded Site were estimated to be 2.89 t ha-1 and 1.05 t ha-1, respectively. Average WRC at the Native Site and Invaded Site were estimated at 1.45 mm and 0.68 mm, respectively. The difference is likely due to the presence of the invasive Psidium cattleianum at the Invaded Site because its smooth stem surface is unable to support a significant epiphytic layer. The evaporation rate from the epiphyte mass near WSC for the forest stand at the Native Site was measured at 0.38 mm day-1, which represented 10.6 % of the total ET from the forest canopy at the Native Site during the period. The above research has been recently complemented by a thorough investigation of the WSC of all water storage elements (tree stems, tree leaves, shrubs, grasses, litter, fallen branches, and epiphytes) at six forested sites at different elevations within, above, and below the zone of frequent cloud-cover. The goal of this study was to create an inexpensive and efficient methodology for acquiring estimates of above-ground water retention in different types of forests by means of minimally-destructive sampling and surveying. The results of this work serve as baseline data providing a range of possible values of the water retention of specific forest elements and the entire above-ground total where no values have been previously recorded.
Effect of contact angle hysteresis on water droplet evaporation from super-hydrophobic surfaces
S. A. Kulinich; M. Farzaneh
Small water drops demonstrate different evaporation modes on super-hydrophobic polymer surfaces with different hysteresis of contact angle. While on the high-hysteresis surface evaporation follows the constant-contact-diameter mode, the constant-contact-angle mode dominates on the low-hysteresis surface. These modes were previously reported for smooth hydrophilic and hydrophobic surfaces, respectively. The experimental data are compared to the previous models describing spherical cap drops
Estimation of evaporative loss based on the stable isotope composition of water using Hydrocalculator
NASA Astrophysics Data System (ADS)
Skrzypek, Grzegorz; Myd?owski, Adam; Dogramaci, Shawan; Hedley, Paul; Gibson, John J.; Grierson, Pauline F.
Accurate quantification of evaporative losses to the atmosphere from surface water bodies is essential for calibration and validation of hydrological models, particularly in remote arid and semi-arid regions, where intermittent rivers are generally minimally gauged. Analyses of the stable hydrogen and oxygen isotope composition of water can be used to estimate evaporative losses from individual pools in such regions in the absence of instrumental data but calculations can be complex, especially in highly variable systems. In this study, we reviewed and combined the most recent equations required for estimation of evaporative losses based on the revised Craig-Gordon model. The updated procedure is presented step-by-step, increasing ease of replication of all calculations. The main constraints and sources of uncertainties in the model were also evaluated. Based on this procedure we have designed a new software, Hydrocalculator, that allows quick and robust estimation of evaporative losses based on isotopic composition of water. The software was validated against measures of field pan evaporation under arid conditions in northwest Australia as well as published data from other regions. We found that the major factor contributing to the overall uncertainty in evaporative loss calculations using this method is uncertainty in estimation of the isotope composition of ambient air moisture.
Using water stable isotopes to assess evaporation and water residence time of lakes in EPAÆs National Lakes Assessment.
Stable isotopes of water (?18O and ?2H) can be very useful in large-scale monitoring programs because water samples are easy to collect and water isotopes integrate information about basic hydrological processes such as evaporation as a percentage of inflow (E/I), w...
Toxicity assessment of oil field produced water treated by evaporative processes to produce water to irrigation.
Andrade, V T; Andrade, B G; Costa, B R S; Pereira, O A; Dezotti, M
During the productive life of an oil well, a high quantity of produced water is extracted together with the oil, and it may achieve up to 99% in the end of the well's economical life. Desalination is one of mankind's earliest forms of saline water treatment, and nowadays, it is still a common process used throughout the world. A single-effect mechanical vapor compression (MVC) process was tested. This paper aims to assess the potential toxicity of produced water to be re-used in irrigation. Samples of both produced and distilled water were evaluated by 84 chemical parameters. The distilled produced water presented a reduction up to 97% for the majority of the analyzed parameters, including PAHs. Toxicity bioassays were performed with distilled produced water to evaluate the growth inhibition of Pseudokirchneriella subcapitata algae, the acute toxicity to Danio rerio fish, the germination inhibition of Lactuca sativa vegetable and the severity of toxicity, as well as behavior test with Lumbricid Earthworm Eisenia fetida. The ecotoxicological assays results showed no toxicity, indicating that the referred evaporative process can produce water to be reused in irrigation. PMID:20706017
Effects Of Evaporation Rate of Some Common Organic Contaminants on Hydraulic Conductivity of Aquifer Sand
NASA Astrophysics Data System (ADS)
Saud, Q. J.; Hasan, S. E.
As part of a larger study to investigate potential effects of hydrocarbons on the geotechnical properties of aquifer solids, a series of laboratory experiments were carried out to ascertain the influence of evaporation rate of some common and widespread organic contaminants on the hydraulic conductivity of aquifer sand. Gasoline and its constituent chemicals-benzene, toluene, ethylbenzene, xylene (BTEX), isooctane- and trichloroethylene (TCE) were used to contaminate sand samples collected from the aquifer and vadose zone, at varying concentrations for extended periods of time. The goal was to study any change in the chemical makeup of the contaminants and its control on hydraulic conductivity of the sand. It was found that: (a) gasoline breaks down into constituent compounds when subjected to evaporation, e.g. during oil spills and leaks; and (b) lighter compounds volatilize faster and in the following order: TCE> benzene > isooctane > toluene > gasoline> ethylbenzene > xylene. In addition, these contaminants also caused a decrease in hydraulic conductivity of sand by up to 60% as compared to the uncontaminated sand. The inherent differences in the chemical structure of contaminating chemicals influenced hydraulic conductivity such that the observed decrease was greater for aliphatic than aromatic and chlorinated hydrocarbons. The presentation includes details of the experimental set up; evaporation rate, and geotechnical tests; X-ray diffraction and scanning electron microscope studies; and data analyses and interpretation. Rate of evaporation test indicates that residual LNAPLs will occupy a certain portion of the pores in the soil either as liquid or vapor phase in the vadose zone, and will create a coating on the adjacent solid mineral grains in the aquifer. Replacement of air by the LNAPLs along with grain coatings and the intramolecular forces would impede groundwater movement, thus affecting overall permeability of contaminated aquifers. Keywords: aquifer sand, hydraulic conductivity, BTEX, gasoline, LNAPLs, isooctane
Performance of Water Recirculation Loop Maintentance Components for the Advanced Spacesuit Water Membrane Evaporator
NASA Technical Reports Server (NTRS)
Rector, Tony; Peyton, Barbara; Steele, John W.; Bue, Grant C.; Campbell, Colin; Makinen, Janice
Water loop maintenance components to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop have undergone a comparative performance evaluation with a second SWME water recirculation loop with no water quality maintenance. Results show the benefits of periodic water maintenance. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the evaluation of water recirculation maintenance components was to further enhance this advantage through the leveraging of fluid loop management lessonslearned from the International Space Station (ISS). A bed design that was developed for a UTAS military application, and considered for a potential ISS application with the Urine Processor Assembly, provided a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance cycle included the use of a biocide delivery component developed for ISS to introduce a biocide in a microgravity-compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware.
Performance of Water Recirculation Loop Maintenance Components for the Advanced Spacesuit Water Membrane Evaporator
NASA Technical Reports Server (NTRS)
Rector, Tony; Peyton, Barbara M.; Steele, John W.; Makinen, Janice; Bue, Grant C.; Campbell, Colin
Water loop maintenance components to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop have undergone a comparative performance evaluation with a second SWME water recirculation loop with no water quality maintenance. Results show the benefits of periodic water maintenance. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the evaluation of water recirculation maintenance components was to further enhance this advantage through the leveraging of fluid loop management lessons learned from the International Space Station (ISS). A bed design that was developed for a UTAS military application, and considered for a potential ISS application with the Urine Processor Assembly, provided a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance cycle included the use of a biocide delivery component developed for ISS to introduce a biocide in a microgravity compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware.
Poorly water-soluble drug nanoparticles via solvent evaporation in water-soluble porous polymers.
Roberts, Aled D; Zhang, Haifei
A generic method is described to form poorly water-soluble drug nanoparticles within water-soluble porous polymer by solvent evaporation. The simple dissolution of porous polymer with drug nanoparticles results in stable aqueous drug nanoparticle suspension under the optimized conditions. The porous polymers were prepared by freeze-drying aqueous solutions of polyvinyl alcohol, polyethylene glycol, and a surfactant. They were then used as scaffolds for the formation of nanoparticles by initially soaking them in an organic drug solution, followed with removing the solvent via evaporation under ambient conditions. This process was optimized for an antifungal drug griseofulvin, before being translated to anticonvulsant carbamazepine and antineoplastic paclitaxel via a similar procedure, with an aim to improve the loading of drug nanoparticles. By varying certain process parameters a degree of control over the particle size and surface charge could be attained, as well as the drug to stabilizer ratio (drug payload). Noticeably, aqueous paclitaxel nanoparticles (500 nm) were prepared which used the equivalent of 46% less stabilizer than the formulation Taxol. PMID:23499755
Evaporation from porous media in the presence of a water table
NASA Astrophysics Data System (ADS)
Shokri, N.; Salvucci, G.
Improved understanding of soil evaporation in presence of a water table is important in many hydrological processes such as analysis of water and energy balance at land surface, and soil salinization. During evaporation, liquid water is transported from water table toward the surface by capillary forces opposed by the downward gravity and viscous forces. In presence of a shallow water table, the capillary forces may be strong enough to maintain liquid continuity extending from water table to the surface where the liquid vaporization occurs. However, when the water table depth is deep, capillary forces may not be able to overcome the resistive forces resulting in interruption of the liquid continuity. In such cases, using hydraulic conductivity and RichardÆs equation across the entire soil profile to estimate the evaporative flux causes overlooking the physical mechanisms governing the process, though good agreements might be obtained by applying some fitting parameters in unsaturated hydraulic conductivity to match the prediction with the experimental data. The main objective of the present study is to enhance the awareness of limitation of rather automatic assumption of hydraulic continuity through unsaturated zone across large distances above the water table. We used the concept of evaporation characteristic lengths to predict the maximum height of liquid continuity above the water table. When the depth of water table exceeds this characteristic length deduced from the pore size distribution, the hydraulic connection with surface is interrupted resulting in considerable suppression of evaporation due to the evolution of vaporization plane from the surface to a level below the surface defined by the maximum height of the liquid continuity above the water table. To test this model, laboratory evaporation experiments were conducted using Plexiglas columns (600 mm in height and 70 mm in diameter) packed with sand initially saturated with water exposed to evaporation from top boundary. For water supply, Mariotte bottles mounted on digital balances were connected to the bottom of the columns. We used three types of sand differing in particle size distribution. To maintain constant levels of water table, Mariotte bottles were fixed at different depths below the sand surface. The mass loss from the columns and relative humidity and temperature above the columns were recorded digitally each five minutes for nearly 500 hours. Our results confirmed the critical role of liquid continuity above the water table on the evaporative water losses from porous media. The predicted maximum water table depths marking the transition from atmospheric-limited fluxes to the much lower fluxes limited by the transport properties of the porous medium were in good agreement with the experimental results. In addition to the detailed analysis of the relation between water table depths and evaporative water losses, our results provide new insights regarding solute transports and deposition patterns affected by the depth of water table during evaporation.
Variability in cold front activities modulating cool-season evaporation from a southern inland water in the USA
NASA Astrophysics Data System (ADS)
Liu, Heping; Blanken, Peter D.; Weidinger, Tamas; Nordbo, Annika; Vesala, Timo
Understanding seasonal variations in the evaporation of inland waters (e.g., lakes and reservoirs) is important for water resource management as well as the prediction of the hydrological cycles in response to climate change. We analyzed eddy covariance-based evaporation measurements from the Ross Barnett Reservoir (32░26'N, 90░02'W which is always ice-free) in central Mississippi during the cool months (i.e., September-March) of 2007 and 2008, and found that the variability in cold front activities (i.e., passages of cold fronts and cold/dry air masses behind cold fronts) played an important role in modulating the exchange of sensible (H) and latent (?E) heat fluxes. Our analysis showed that 2007's warmer cool season had smaller mean H and ?E than 2008's cooler cool season. This implies that the warmer cool season did not accelerate evaporation and heat exchange between the water surface and the atmosphere. Instead, more frequent cold fronts and longer periods of cold/dry air masses behind the cold fronts in 2008 resulted in overall larger H and ?E as compared with 2007, this primarily taking the form of sporadic short-term rapid 'pulses' of H and ?E losses from the water's surface. These results suggest that future climate-induced changes in frequency of cold fronts and the meteorological properties of the air masses behind cold fronts (e.g., wind speeds, temperature, and humidity), rather than other factors of climate change, would produce significant variations in the water surface's energy fluxes and subsequent evaporation rates.
Tracing Water Sources and Quantifying Evaporation in the Brazos River, Central Texas
NASA Astrophysics Data System (ADS)
VanPlantinga, A.; Hunt, L. E.; Winning, D.; Robertson, J.; Stockert, E.; Roark, E.; Grossman, E. L.
Situated in the subtropical dry zone, Central Texas is sensitive to the effects of climate change, notably drought; furthermore, developments over the last century in agriculture, urban infrastructure, and river engineering have altered the landscape extensively. This study models water source mixing and seasonal variation in evaporation in Brazos River waters in Central Texas. The Brazos River from Waco to College Station, Texas is generally characterized as having dissolved salt load derived mostly from Lake Whitney (a flood-control and hydroelectric storage reservoir) and groundwater baseflow from the adjacent shallow alluvial aquifer. Brazos River water ?18O, ?D, and conductivity were measured bi-weekly in Brazos County, Texas from January 2012 through August 2013. Conductivity, ?18O, and ?D vary seasonally and are positively correlated. The Brazos River ?18O-?D data from Brazos County fall along a local evaporation line (?D = 5.66 * ?18O - 2.47, r2 = 0.95) that intersects and surpasses values for Lake Whitney. In contrast, the ?18O-conductivity trend for the Brazos River does not intersect data for Lake Whitney. These observations suggest mixing with an evaporated water source of lower conductivity. The relative contribution of other Brazos River water sources is uncertain. Percent evaporation of original rain sampled as Brazos River water was estimated using a Rayleigh distillation model and the method of Gonfiantini (1986) while assuming 1) a closed system with an atmospheric exchange component, and 2) ?18O and ?D values of local rain are -5.33ē and -32.6ē, respectively. Modeled percent evaporation of original rain varies from winter (JFM; 1%-20%) to spring (AMJ; 9-25%) to summer (JAS; 16-33%), to fall (OND; 15-24%). Rayleigh distillation modeling estimates are consistently higher (~5%) than those estimated by Gonfiantini's method. A simple mass-balance model predicts that Brazos River water percent evaporation and ?18O enrichment are 2.8% and 0.40ē respectively for low flow in Brazos County (200 cubic feet per second or cfs) and 0.9% and 0.12ē respectively for high flow (1000 cfs). This implies that a small percentage of evaporation of original rain in the Brazos River could be attributed to the alluvial aquifer. Thus, we believe that the alluvial aquifer is not dominating the Brazos River water supply as much as previously thought, even in times of low flow. Other surface waters more evaporatively enriched in 18O, specifically those derived from the network of local reservoirs and tributaries, likely influence the Brazos River more than previously thought.
The design and evaluation of a water delivery system for evaporative cooling of a proton exchange membrane fuel cell
Al-Asad, Dawood Khaled Abdullah
An investigation was performed to demonstrate system design for the delivery of water required for evaporative cooling of a proton exchange membrane fuel cell (PEMFC). The water delivery system uses spray nozzles capable of injecting water directly...
Operation of a low temperature absorption chiller at rating point and at reduced evaporator temperature
NASA Astrophysics Data System (ADS)
Best, R.; Biermann, W.; Reimann, R. C.
The returned fifteen ton Solar Absorption Machine (SAM) 015 chiller was given a cursory visual inspection, some obvious problems were remedied, and then it was placed on a test stand to get a measure of dirty performance. It was then given a standard acid clean, the water side of the tubes was brushed clean, and then the machine was retested. The before and after cleaning data were compared to equivalent data taken before the machine was shipped. The second part of the work statement was to experimentally demonstrate the technical feasibility of operating the chiller at evaporator temperatures below 0(0)C (32(0)F) and identify any operational problems.
A phylogenetic analysis of basal metabolism, total evaporative water loss, and life-history among foxes from desert and mesic regions
J. B. Williams; A. Mu±oz-Garcia; S. Ostrowski; B. I. Tieleman
We measured basal metabolic rate (BMR) and total evaporative water loss (TEWL) of species of foxes that exist on the Arabian Peninsula, BlanfordÆs fox ( Vulpes cana) and two subspecies of Red fox ( Vulpes vulpes). Combining these data with that on other canids from the literature, we searched for specialization of physiological traits among desert foxes using both conventional
The isotopic composition of evaporating waters - review of the historical evolution leading up to the Craig-Gordon model.
Gat, Joel R
Attempts to explain the variations in the abundance of heavy isotopic species of water throughout the hydrologic cycle solely by means of the classical equilibrium-fractionation processes could not be reconciled with measured abundances of the isotopic species in residues of "evaporation systems". Focusing on the evaporation of surface waters, the paper follows the evolution of the concepts during the 1950-ties and early 1960-ties leading up to the formulation of the Craig-Gordan Evaporation Model in 1965. PMID:18320424
Novel in situ method for locating virtual source in high-rate electron-beam evaporation
NASA Astrophysics Data System (ADS)
Bhatia, M. S.
The concept of virtual source simplifies calculation of thickness distribution on extended substrates in high rate vacuum coating employing electron-beam heating. The height of the point (virtual source), from which vapor can be assumed to emanate in accordance with Knudsen's cosine law, to yield the experimentally obtained thickness distribution, is calculated and this establishes the position of virtual source. Such as post facto determination is cumbersome as it is valid for the prescribed material evaporating at a certain rate in a specified geometry. A change in any of these entails a fresh measurement. Experimenters who use a large number of materials and deposit at different rates therefore have to carry out a number of trials before they can locate the virtual source at the desired deposition parameters. An in situ method for obtaining virtual source position can go a long way in reducing the labor of these experiments. A novel in situ method is described to locate the virtual source.
Determination of mass and thermal accommodation coefficients from evolution of evaporating water droplet
Determination of mass and thermal accommodation coefficients from evolution of evaporating water trap placed in a small climatic chamber. The evolution of the droplet and the evolution dynamics this model to the experimental data, the mass and thermal accommodation coefficients were determined to be C
Monitoring near surface soil water and associated dynamics of infiltration and evaporation fluxes
Technology Transfer Automated Retrieval System (TEKTRAN)
In-situ monitoring of soil water has the advantage of integrating the precipitation and evaporation history and gradual changes in hydraulic properties on the aggregate response of the soil-plant-atmosphere system. A paired field study in Bushland, Texas, and Tribune, Kansas, evaluated infiltration ...
Transformation Of Arsenic In Agricultural Drainage Water Disposed Into An Evaporation Basin In California, USA.
Technology Transfer Automated Retrieval System (TEKTRAN)
Evaporation basins have been widely used for the disposal of agricultural drainage in areas requiring subsurface drainage in the San Joaquin Valley of California, a high agricultural production area in USA. The irrigation drainage water contains elevated concentrations of trace elements, including S...
Some Experiments on Evaporation of High-TDS Phreatic Water in an Arid Area
NASA Astrophysics Data System (ADS)
Li, X.; Jin, M.; Zhou, J.; Liu, Y.; Zhao, Y.
Most experiments that had been done on evaporation of phreatic water were limited to waters with fresh or low total dissolved solids (TDS, no more than 10g/L). The TDS of phreatic water is always dozens or even hundreds of grams per liter in extremely arid areas. Thus, experiments on phreatic water evaporation of different TDS (3g/L, 30g/L, 100g/L, 250g/L) were carried out in an arid plain of south Xinjiang, China. The results showed that there was significant linear positive correlation between TDS of phreatic water and cumulative salinity in soil profile. The variation of phreatic water evaporation was lag behind the change of surface water measured by E20 equipment, but both of them were more drastic at nighttime than the daytime. The research shows that the daytime evaporation capacity has significant effect on nighttime evaporation, and the soil water vapor condense at profile also is an important driving factor for the nighttime evaporation. Capillary rise is a significant contributor of soil salinity in extremely arid areas. Experiments about effects of different grains of sand soil and TDS of phreatic water (1, 30, 100, 250 g/L) on capillary rise showed that TDS had significant effects on capillary rise in later stage of experiments. For coarse sand, the higher TDS made the lower height of capillary rise. But for fine sand, the height of capillary rise of 1g/L was obviously larger than others. The sequence of height from larger to lower of capillary rise in silt was 30, 100, 250 and 1g/L. At the beginning of experiments on coarse sand, the higher TDS made the lower velocity of capillary rise, but other soil groups were not. Compared to high-TDS, the grain of sand soil was a more primary controlling factor of capillary rise. The research indicates that high-TDS not only changes the gravity of capillary water but also the pore size of soil during the processes of capillary rise in fine sand.
Experimental study of evaporation of horizontal films of water-salt solutions
NASA Astrophysics Data System (ADS)
Elistratov, S. L.; Morozov, V. S.
The present studies were carried out for the horizontal films (thin layers) of water and water solutions of NaCl, CaCl2, LiCl, and LiBr with different solubility characteristics, as well as with specific features of formation and decay of water hydrates. Required volume of solution Vo of given weight concentration ?o, preliminary heated to the working surface temperature, was put in one step on the horizontal bottom of the bowl, heated to working temperature tCT, by means of volume batchers Thermo Scientific. After evaporation completion, the final mass of solution and form of their residue were registered. At the final stage of evaporation formation of NaCl crystals and water hydrates of CaCl2 Ę 2H2O, LiCl Ę H2O, and LiBr Ę 2H2O occurred.
Effects of ambient water vapor pressure and temperature on evaporative water loss in Peromyscus maniculatus and Mus musculus
Richard M. Edwards; Howard Haines
SummaryĀĀThe effects of ambient water vapor pressure (VP) and temperature on evaporative water loss (EWL) from the head and trunk ofPeromyscus maniculatus andMus musculus were measured with dew point hygrometry. At a given ambient temperature both head and trunk EWL were directly proportional to the water vapor pressure deficit. Cutaneous EWL in both species was directly related to the difference
A comparison of two techniques for measuring the relative rates of moisture evaporation from limited areas of the skin of Holstein, Jersey and Jersey-Brahman cattleĀ
Motasem, Mohamed M
in psrtisl fulfilhasat of the reqoireaests for the deSree of hoSuat 1964 Eager Subject! Hairy Seiessa A ORFkllSW OF TNO TRC8NXQOES FOR NRASORIIO THE REtdXWE RATES OF lOISXORE EFAFORATTON ISO' LQCTEO AREAS OF TNE SHIN OF HOLSTEIN~ JENNET ANO JRRSET... Holstein cows, but that the resistance was not the result of an 1ncreased capacity to evaporate water. Bauer)ee and co~rkers (2) modified the technique of NcDowell et al. (17). They reported that sweating rate, rectal teaperature, respiration rate...
``Boiling'' in the water evaporating meniscus induced by Marangoni flow
NASA Astrophysics Data System (ADS)
Liu, Xiang; Guo, Dan; Xie, Guoxin; Liu, Shuhai; Luo, Jianbin
A counterintuitive phenomenon, "boiling," was directly observed near the contact line of the pure water meniscus formed in a ball and disk configuration, when the ball temperature was far lower than the saturation temperature of water. The number of the emerging bubbles due to "boiling" increased with ball temperature rising; each bubble would expanse initially and then collapse. When two surfaces were heated to the same temperature, "boiling" disappeared. It was proposed that the temperature gradient between the two surfaces initiated Marangoni flow, which hindered flow toward the film, resulting in the negative pressure and cavitation in the liquid film.
Insight into the molecular mechanism of water evaporation via the finite temperature string method
Musolino, Nicholas; Trout, Bernhardt L.
The process of water's evaporation at its liquid/air interface has proven challenging to study experimentally and, because it constitutes a rare event on molecular time scales, presents a challenge for computer simulations as well. In this work, we simulated water's evaporation using the classical extended simple point charge model water model, and identified a minimum free energy path for this process in terms of 10 descriptive order parameters. The measured free energy change was 7.4 kcal/mol at 298 K, in reasonable agreement with the experimental value of 6.3 kcal/mol, and the mean first-passage time was 1375 ns for a single molecule, corresponding to an evaporation coefficient of 0.25. In the observed minimum free energy process, the water molecule diffuses to the surface, and tends to rotate so that its dipole and one O¢H bond are oriented outward as it crosses the Gibbs dividing surface. As the water molecule moves further outward through the interfacial region, its local density is higher than the time-averaged density, indicating a local solvation shell that protrudes from the interface. The water molecule loses donor and acceptor hydrogen bonds, and then, with its dipole nearly normal to the interface, stops donating its remaining hydrogen bond. At that point, when the final, accepted hydrogen bond is broken, the water molecule is free. We also analyzed which order parameters are most important in the process and in reactive trajectories, and found that the relative orientation of water molecules near the evaporating molecule, and the number of accepted hydrogen bonds, were important variables in reactive trajectories and in kinetic descriptions of the process. PMID:23574252
Evaporative cooling of water in a mechanical draft cooling tower
S. P. Fisenko; A. A. Brin; A. I. Petruchik
A new mathematical model of a mechanical draft cooling tower performance has been developed. The model represents a boundary-value problem for a system of ordinary differential equations, describing a change in the droplets velocity, its radii and temperature, and also a change in the temperature and density of the water vapor in a mist air in a cooling tower. The
Study of environmental isotope distribution in the Aswan High Dam Lake (Egypt) for estimation of evaporation of lake water and its recharge to adjacent groundwater.
Aly, A I; Froehlich, K; Nada, A; Awad, M; Hamza, M; Salem, W M
Oxygen-18 ((18)0) and deuterium isotopes were used to estimate the evaporation from the Aswan High Dam Lake and to investigate the inter-relation between the lake water and adjacent groundwater.According to stable isotopic analysis of samples taken in 1988 and 1989, the lake can be divided into two sections. In the first section extending between Abu Simbel and a point between EI-Alaki and Krosko, a remarkable vertical gradient of (18)0 and deuterium isotopic composition was observed. The second northern sector extending to the High Dam is characterised by a lower vertical isotopic gradient. In this sector in general, higher values of (18)O and deuterium contents were found at the top and lower values at the bottom. Also a strong horizontal increase of the heavy isotope content was observed. Thus, in the northern section evaporation is of dominating influence on the isotopic composition of the lake water.With the help of an evaporation pan experiment it was possible to calibrate the evaporative isotope enrichment in the lake and to facilitate a preliminary estimate of evaporative losses of lake water. The evaporation from the lake was estimated to be about 19% of the input water flow rate.The groundwater around the lake was investigated and samples from production wells and piezometers were subjected to isotopic analysis. The results indicate that recent recharge to the groundwater aquifer is limited to wells near to the lake and up to a maximum distance of about 10 km. The contribution of recent Nile water to the groundwater in these wells was estimated to range between 23 and 70%. Beyond this distance, palaeowater was observed with highly depleted deuterium and (18)0 contents, which was also confirmed by 14c dating. The age of palaeo groundwater in this area can reach values of more than 26,000 years.Recommendations are given for efficient water management of the lake water. PMID:24198080
Evaporation and wetting dynamics of sessile water droplets on submicron-scale patterned silicon hydrophobic surfaces
Choi, Chang Kyoung [Michigan Technological University; Shin, Dong Hwan [Chung-Ang University; Lee, Seong Hyuk [Chung-Ang University; Retterer, Scott T [ORNL
The evaporation characteristics of 1 l sessile water droplets on hydrophobic surfaces are experimentally examined. The proposed hydrophobic surfaces are composed of submicron diameter and 4.2- m-height silicon post arrays. A digital image analysis algorithm was developed to obtain time-dependent contact angles, contact diameters, and center heights for both non-patterned polydimethylsiloxane (PDMS) surfaces and patterned post array surfaces, which have the same hydrophobic contact angles. While the contact angles exhibit three distinct stages during evaporation in the non-patterned surface case, those in the patterned silicon post array surface case decrease linearly. In the case of post array hydrophobic surfaces, the initial contact diameter remains unchanged until the portion of the droplet above the posts completely dries out. The edge shrinking velocity of the droplet shows nonlinear characteristics, and the velocity magnitude increases rapidly near the last stage of evaporation.
Effects of crop residue on soil and plant water evaporation in a dryland cotton system
NASA Astrophysics Data System (ADS)
Lascano, R. J.; Baumhardt, R. L.
Dryland agricultural cropping systems emphasize sustaining crop yields with limited use of fertilizer while conserving both rain water and the soil. Conservation of these resources may be achieved with management systems that retain residues at the soil surface simultaneously modifying both its energy and water balance. A conservation practice used with cotton grown on erodible soils of the Texas High Plains is to plant cotton into chemically terminated wheat residues. In this study, the partitioning of daily and seasonal evapotranspiration ( E t) into soil and plant water evaporation was compared for a conventional and a terminated-wheat cotton crop using the numerical model ENWATBAL. The model was configured to account for the effects of residue on the radiative fluxes and by introducing an additional resistance to latent and sensible heat fluxes derived from measurements of wind speed and vapor conductance from a soil covered with wheat-stubble. Our results showed that seasonal E t was similar in both systems and that cumulative soil water evaporation was 50% of E t in conventional cotton and 31% of E t in the wheat-stubble cotton. Calculated values of E t were in agreement with measured values. The main benefit of the wheat residues was to suppress soil water evaporation by intercepting irradiance early in the growing season when the crop leaf area index (LAI) was low. In semiarid regions LAI of dryland cotton seldom exceeds 2 and residues can improve water conservation. Measured soil temperatures showed that early in the season residues reduced temperature at 0.1 m depth by as much as 5░C and that differences between systems diminished with depth and over time. Residues increased lint yield per unit of E t while not modifying seasonal E t and reducing cumulative soil water evaporation.
Measuring forest evaporation and transpiration rates with fibre optic temperature sensing
NASA Astrophysics Data System (ADS)
Coenders-Gerrits, Miriam; Luxemburg, Wim; Hessels, Tim; de Kloe, Arjan; Elbers, Jan
Evaporation is one of the most important fluxes of the water balance as it accounts for 55-80% of the precipitation. However, measuring evaporation remains difficult and requires sophisticated and expensive equipment. In this paper we propose a new measuring technique based on the existing Bowen ratio method. With a fibre optic cable a temperature and a vapour pressure profile can be measured by the principle of a psychrometer and combined with the net radiation (and ground heat flux) the latent heat can be calculated. Compared to the conventional Bowen ratio method the advantages of this method is that the profiles are measured with a single sensor (resulting in a smaller error), and contain more measuring points in the vertical and therefore give more insight into the developed profiles. The method also allows to measure through a forest canopy. Applying the Bowen ratio above and below the canopy an estimation of the transpiration flux can be obtained. As a first test, we compared in a pine forest in The Netherlands (Loobos) the transpiration estimates of the fibre optic cable with sapflow measurements, and eddy covariance measurements above and below the canopy. The experiment was carried out on three days in September 2013 and the preliminary results show reasonable correlation with the eddy covariance estimates, but not with the sapflow observations. To explain the differences further investigation is needed and a longer measuring period is required.
Enhanced Evaporation Strength through Fast Water Permeation in Graphene-Oxide Deposition.
Li Tong, Wei; Ong, Wee-Jun; Chai, Siang-Piao; Tan, Ming K; Mun Hung, Yew
The unique characteristic of fast water permeation in laminated graphene oxide (GO) sheets has facilitated the development of ultrathin and ultrafast nanofiltration membranes. Here we report the application of fast water permeation property of immersed GO deposition for enhancing the performance of a GO/water nanofluid charged two-phase closed thermosyphon (TPCT). By benchmarking its performance against a silver oxide/water nanofluid charged TPCT, the enhancement of evaporation strength is found to be essentially attributed to the fast water permeation property of GO deposition instead of the enhanced surface wettability of the deposited layer. The expansion of interlayer distance between the graphitic planes of GO deposited layer enables intercalation of bilayer water for fast water permeation. The capillary force attributed to the frictionless interaction between the atomically smooth, hydrophobic carbon structures and the well-ordered hydrogen bonds of water molecules is sufficiently strong to overcome the gravitational force. As a result, a thin water film is formed on the GO deposited layers, inducing filmwise evaporation which is more effective than its interfacial counterpart, appreciably enhanced the overall performance of TPCT. This study paves the way for a promising start of employing the fast water permeation property of GO in thermal applications. PMID:26100977
Enhanced Evaporation Strength through Fast Water Permeation in Graphene-Oxide Deposition
Li Tong, Wei; Ong, Wee-Jun; Chai, Siang-Piao; Tan, Ming K.; Mun Hung, Yew
The unique characteristic of fast water permeation in laminated graphene oxide (GO) sheets has facilitated the development of ultrathin and ultrafast nanofiltration membranes. Here we report the application of fast water permeation property of immersed GO deposition for enhancing the performance of a GO/water nanofluid charged two-phase closed thermosyphon (TPCT). By benchmarking its performance against a silver oxide/water nanofluid charged TPCT, the enhancement of evaporation strength is found to be essentially attributed to the fast water permeation property of GO deposition instead of the enhanced surface wettability of the deposited layer. The expansion of interlayer distance between the graphitic planes of GO deposited layer enables intercalation of bilayer water for fast water permeation. The capillary force attributed to the frictionless interaction between the atomically smooth, hydrophobic carbon structures and the well-ordered hydrogen bonds of water molecules is sufficiently strong to overcome the gravitational force. As a result, a thin water film is formed on the GO deposited layers, inducing filmwise evaporation which is more effective than its interfacial counterpart, appreciably enhanced the overall performance of TPCT. This study paves the way for a promising start of employing the fast water permeation property of GO in thermal applications. PMID:26100977
Soil water evaporation measurement of lysimeter based on fiber Bragg grating sensor
NASA Astrophysics Data System (ADS)
Yan, Kejun; Liu, Jun; Miao, Liping; Bai, Li; Zhong, Wenting
A lysimeter weighing system based on fiber Bragg grating (FBG) sensor for measuring the soil water evaporation was presented in this paper. By the use of three mechanical levers and balance weight, the weight loaded on the FBG sensor was reduced K times (here, K was the ratio of levers). So the amount of water change in the soil container of tons can be weighted. A two-hole cantilever was selected as the elastomer structure of FBG weighing sensor, and an optimum design was carried on using the finite element method to meet the small-scaled design requirements. Using the matching fiber Bragg grating demodulation method based on LabVIEW, the demodulation system was easy to be implemented. Then the FBG center wavelength drift was converted into a time interval, and the weight can be obtained automatically through measuring the interval by computer. Preliminary experiment showed that this weighing system has the ability of measuring soil water evaporation accurately.
Influence of the stellar mass function of the evaporation rate of tidally limited postcollapse globular clusters
NASA Astrophysics Data System (ADS)
Lee, Hyung Mok; Goodman, Jeremy
We study the rate of escape of stars (evaporation) from tidally limited postcollapse globular clusters having a power-law distribution of stellar masses. We use a multimass Fokker-Planck code and assume a steady tidal field. Stellar-dynamical processes cause the inner parts of the cluster to expand, which in turn causes stars to overflow the tidal boundary. Mass loss by stellar evolution is assumed to be unimportant in these later evolutionary stages. The fraction of the cluster mass lost per half-mass relaxation time trh is roughly constant, in agreement with simple homologous models with equal-mass stars. If trh is computed in the conventional way from the mean stellar mass, however, a broad stellar mass function can double the loss of mass per trh. We discuss implications of our results for the evolution of globular cluster systems in our own and other galaxies. In particular, the number of Galactic clusters destroyed by evaporation alone may be as large as or larger than the present population.
Tropical Ocean Evaporation/SST Sensitivity and It's Link to Water and Energy Budget Variations During ENSO
NASA Technical Reports Server (NTRS)
Robertson, Franklin R.; Marshall, Susan; Oglesby, Robert; Roads, John; Sohn, Byung-Ju; Arnold, James E. (Technical Monitor)
The continuing debate over feedback mechanisms governing tropical sea surface temperatures (SSTs) and tropical climate in general has highlighted the diversity of potential checks and balances within the climate system. Competing feedbacks due to changes in surface evaporation, water vapor, and cloud long- and shortwave radiative properties each may serve critical roles in stabilizing or destabilizing the climate system. It is also intriguing that even those climate variations having origins internal to the climate system - changes in ocean heat transport for example, apparently require complementary equilibrating effects by changes in atmospheric energy fluxes. Perhaps the best observational evidence of this is the relatively invariant nature of tropically averaged net radiation exiting the top-of-atmosphere (TOA) as measured by broadband satellite sensors over the past two decades. Thus, analyzing how these feedback mechanisms are operating within the context of current interannual variability may offer considerable insight for anticipating future climate change. In this paper we focus primarily on interannual variations of ocean evaporative fluxes and their significance for coupled water and energy cycles within the tropical climate system. In particular, we use both the da Silva estimates of surface fluxes (based on the Comprehensive Ocean Atmosphere Data Set, COADS) and numerical simulations from several global climate models to examine evaporation sensitivity to perturbations in SST associated with warm and cold ENSO events. The specific questions we address are as follows: (1) What recurring patterns of surface wind and humidity anomalies are present during ENSO and how do they combine to yield systematic evaporation anomalies?, (2) What is the resulting tropical ocean mean evaporation-SST sensitivity associated with this climate perturbation?, and (3) What role does this evaporation play in tropical heat and water balance over tropical oceanic regions? We use the da Silva ocean flux data to identify composite structure of departures of latent heat flux from climatology. We also show how these patterns arise out of associated wind and humidity anomaly distributions. Our preliminary work shows that evaporation sensitivity estimates from the da Silva / COADS data, computed for the tropical oceans (30 degrees N/S) are in the neighborhood of 5 to 6 W/square m K. Model estimates are also quite close to this figure. This rate is only slightly less than a rate corresponding to constant relative humidity; however, substantial regional departures from constant relative humidity are present. These patterns are robust and we relate the associated wind and humidity fluctuations noted in previous investigations to the derived evaporation anomalies. Finally, these results are interpreted with other data from the Earth radiation Budget Experiment (ERBE), Global Precipitation Climatology Project (GPCP) and NASA's Surface Radiation Budget (SRB) data set to characterize the tropical energetics of ENSO-related climate variability.
Adaptation of metabolism and evaporative water loss along an aridity gradient.
Tieleman, B Irene; Williams, Joseph B; Bloomer, Paulette
Broad-scale comparisons of birds indicate the possibility of adaptive modification of basal metabolic rate (BMR) and total evaporative water loss (TEWL) in species from desert environments, but these might be confounded by phylogeny or phenotypic plasticity. This study relates variation in avian BMR and TEWL to a continuously varying measure of environment, aridity. We test the hypotheses that BMR and TEWL are reduced along an aridity gradient within the lark family (Alaudidae), and investigate the role of phylogenetic inertia. For 12 species of lark, BMR and TEWL decreased along a gradient of increasing aridity, a finding consistent with our proposals. We constructed a phylogeny for 22 species of lark based on sequences of two mitochondrial genes, and investigated whether phylogenetic affinity played a part in the correlation of phenotype and environment. A test for serial independence of the data for mass-corrected TEWL and aridity showed no influence of phylogeny on our findings. However, we did discover a significant phylogenetic effect in mass-corrected data for BMR, a result attributable to common phylogenetic history or to common ecological factors. A test of the relationship between BMR and aridity using phylogenetic independent constrasts was consistent with our previous analysis: BMR decreased with increasing aridity. PMID:12590762
Seasonal changes in physical processes controlling evaporation over inland water
NASA Astrophysics Data System (ADS)
Zhang, Qianyu; Liu, Heping
While previous studies have shown the distinct characteristics of water surface energy fluxes in different seasons, much less analysis is conducted about how seasonal changes in physical processes and environmental variables in the atmospheric surface layer (ASL) cause variations in flux exchange. Here we analyzed and compared eddy covariance fluxes of sensible heat (H) and latent heat (LE) and other microclimate variables that were measured over a large inland water surface in the winter season (January, February, and March) and the summer season (June, July, and August) of 2008. Our analysis was primarily focused on LE using half-hour time series data on a short-term basis. Our results show that an increase in wind speeds (U) or vapor pressure difference in the ASL (?e) or ASL instability did not necessarily cause an increase in LE, and the opposite changes in LE with changes in these variables were observed. Relative regulations of LE by different environmental variables depended largely on ?e magnitudes. Under low ?e conditions, diurnal LE variations were not sensitive to changes in ?e and U but were controlled primarily by changes in the ASL stability. Under high ?e conditions, diurnal LE variations were mainly determined by changes in ?e, though alternate controls by U and ?e were observed, whereas ASL stability played minor roles in affecting LE variations. Whether these highly nonlinear responses of LE to environmental variables are adequately reflected in the bulk transfer relations requires further studies.
Improvement to Air2Air Technology to Reduce Fresh-Water Evaporative Cooling Loss at Coal-Based Thermoelectric Power Plants
Ken Mortensen
This program was undertaken to enhance the manufacturability, constructability, and cost of the Air2Air{TM} Water Conservation and Plume Abatement Cooling Tower, giving a validated cost basis and capability. Air2Air{TM} water conservation technology recovers a portion of the traditional cooling tower evaporate. The Condensing Module provides an air-to-air heat exchanger above the wet fill media, extracting the heat from the hot saturated moist air leaving in the cooling tower and condensing water. The rate of evaporate water recovery is typically 10% - 25% annually, depending on the cooling tower location (climate). This program improved the efficiency and cost of the Air2Air{TM} Water Conservation Cooling Tower capability, and led to the first commercial sale of the product, as described.
Global spaceborne assessment of the relationship between terrestrial water storage and evaporative demand
NASA Astrophysics Data System (ADS)
Levine, P. A.; De Linage, C.; Velicogna, I.; Randerson, J. T.
Feedbacks between terrestrial water storage (TWS) and the atmosphere can impact climatic extremes such as droughts and heat waves. High evaporative demand (high temperature and/or low humidity) removes more water by evapotranspiration, leading to lower TWS. At the same time, low TWS availability limits evapotranspiration, which increases evaporative demand by reducing the ratio of latent to sensible heat fluxes from the land surface. Studies using coupled land-atmosphere models have explored the strength of these relationships, and have been validated using local observational data, but global-scale observational studies are limited by data availability. We quantified these relationships globally using TWS data from the Gravity Recovery and Climate Experiment (GRACE), surface air temperature and relative humidity from the Atmospheric Infrared Sounder (AIRS), and precipitation from the Global Precipitation Climatology Project (GPCP). Our approach demonstrated a strong relationship between antecedent TWS and subsequent evaporative demand in certain key regions of the globe. These regions are consistent with the "hot spots" of land-atmosphere coupling found in modeling studies, and represent semi-arid transitional areas where TWS strongly limits evapotranspiration. We also found a strong relationship between antecedent evaporative demand and subsequent TWS throughout most of the global land surface. These observational relationships provide a benchmark for comparison with climate model simulations. We found good agreement between the satellite-derived relationships and the equivalent relationships calculated with output from the Community Land Model (CLM) version 4.5.
Absence of Marangoni convection at Marangoni numbers above 27,000 during water evaporation.
Thompson, Ian; Duan, Fei; Ward, C A
Two mechanisms by which Marangoni convection can be produced at the interface of water with its vapor are: (1) by imposing a temperature gradient parallel to the water-vapor interface, and (2) by imposing a temperature gradient perpendicular to the interface that results in the liquid becoming unstable. A series of evaporation experiments conducted with H2O and with D2O maintained at the mouth of a stainless-steel funnel indicated the presence of Marangoni convection, but the mechanism producing the convection was unclear. We have investigated the mechanism using a funnel constructed with a polymethyl methacrylate that has a small thermal conductivity relative to that of water and repeating the evaporation experiments. Marangoni convection was eliminated with this funnel even though the Marangoni number, Ma, was in the range 8277< or =Ma< or =27 847 . A comparison of the assumptions made in the theories available to predict the onset of Marangoni convection with the observations made in this study indicates some of the assumptions are invalid: although generally neglected, energy transport through the vapor to the interface of evaporating water is significant; there is an interfacial temperature discontinuity, but it is in the opposite direction of that assumed in the existing theories: the interfacial-vapor temperature is greater than that of the liquid during evaporation; and the prediction of the critical Marangoni number is based on an arbitrarily chosen value of the heat-transfer coefficient. When the temperature gradient is perpendicular to the water-vapor interface, these invalid assumptions indicate present theories do not apply to volatile liquids. PMID:20365074
FIELD TEST OF THE WATER-WHEEL IR (WIR) SPECTROMETER ON EVAPORATIVE SALT DEPOSITS AT TIBETAN PLATEAU. P. Sobron, J. J. Freeman, Alian Wang, Dept Earth and Planetary Sciences
FIELD TEST OF THE WATER-WHEEL IR (WIR) SPECTROMETER ON EVAPORATIVE SALT DEPOSITS AT TIBETAN PLATEAU experiment[1] is designed to detect directly water in different forms (liquid, ice, or clath- rates: The Water-Wheel IR instrument is a NIR (1-5 m) reflectance spectrometer using active sources. The WIR
Characterization of the LGFSTF wind tunnel in preparation for the DOE/EPA hazardous chemical evaporation rate experiments
Havens, J.; Walker, H.; Spicer, T.
The Environmental Protection Agency and the Department of Energy are conducting chemical evaporation rate experiments in the DOE`s Liquefied Gaseous Fuels Spill Test Facility (LGFSTF) wind tunnel to determine the effect on evaporation rate of pool temperature and wind speed. Evaporation rates measured in these tests will be used to verify mathematical models used to define the source (gas) rate inputs to dispersion models. In preparation for the experiments the LGFSTF tunnel has been modified to provide for the simulation of an atmospheric boundary layer flow on the tunnel floor. This report describes work performed by the DOE Modeling Support Center at the University of Arkansas to define (characterize) the turbulence properties in the boundary layer of the (modified) wind tunnel test section. Hot wire anemometry measurements were made to characterize the boundary layer flow over the evaporation test pan. Mean velocity and turbulence statistics were measured along a verticle line (extending from 0.5 cm to 60 cm above the tunnel floor) located on the tunnel centerline immediately upwind of the evaporation pan. The x-direction mean velocity data were analyzed to estimate the applicable values of the surface roughness and friction velocity for four tunnel (variable frequency controller) speed settings: 15 Hz, 30 Hz, 45 Hz, and 60 Hz.
Theoretical investigation of the injection and evaporation of water in a hydrogen/oxygen steam generator
NASA Astrophysics Data System (ADS)
Beer, Stefan
For the cooling of the reaction products resulting from a stoichiometric hydrogen/oxygen combustion, water is injected normal to the gas stream. The penetration of the jet strongly influences the temperature distribution across the streaming water vapor. The penetration of the jet is calculated by using the jet shedding model. The results are compared with the data of the garden hose model. To calculate the lifetime of a water droplet in super heated stream, several models are developed. The parameters of the injection and evaporation process are varied and analyzed.
Sensitivity of Hollow Fiber Spacesuit Water Membrane Evaporator Systems to Potable Water Constituents, Contaminants and Air Bubbles
NASA Technical Reports Server (NTRS)
Bue, Grant C.; Trevino, Luis A.; Fritts, Sharon; Tsioulos, Gus
The Spacesuit Water Membrane Evaporator (SWME) is the baseline heat rejection technology selected for development for the Constellation lunar suit. The first SWME prototype, designed, built, and tested at Johnson Space Center in 1999 used a Teflon hydrophobic porous membrane sheet shaped into an annulus to provide cooling to the coolant loop through water evaporation to the vacuum of space. This present study describes the test methodology and planning and compares the test performance of three commercially available hollow fiber materials as alternatives to the sheet membrane prototype for SWME, in particular, a porous hydrophobic polypropylene, and two variants that employ ion exchange through non-porous hydrophilic modified Nafion. Contamination tests will be performed to probe for sensitivities of the candidate SWME elements to ordinary constituents that are expected to be found in the potable water provided by the vehicle, the target feedwater source. Some of the impurities in potable water are volatile, such as the organics, while others, such as the metals and inorganic ions are nonvolatile. The non-volatile constituents will concentrate in the SWME as evaporated water from the loop is replaced by the feedwater. At some point in the SWME mission lifecycle as the concentrations of the non-volatiles increase, the solubility limits of one or more of the constituents may be reached. The resulting presence of precipitate in the coolant water may begin to plug pores and tube channels and affect the SWME performance. Sensitivity to macroparticles, lunar dust simulant, and air bubbles will also be investigated.
Rate Setting for Small Water SystemsĀ
Dozier, Monty; Theodori, Gene L.; Jensen, Ricard
Knowing how to set the proper rate for water service is a challenge for small water systems. They must generate enough revenue to remain solvent, but offer affordable service. This publication describes the various types of rates and explains...
Physiological regulation of evaporative water loss in endotherms: is the little red kaluta (Dasykaluta rosamondae) an exception or the rule?
Withers, Philip C.; Cooper, Christine E.
It is a central paradigm of comparative physiology that the effect of humidity on evaporative water loss (EWL) is determined for most mammals and birds, in and below thermoneutrality, essentially by physics and is not under physiological regulation. Fick's law predicts that EWL should be inversely proportional to ambient relative humidity (RH) and linearly proportional to the water vapour pressure deficit (?wvp) between animal and air. However, we show here for a small dasyurid marsupial, the little kaluta (Dasykaluta rosamondae), that EWL is essentially independent of RH (and ?wvp) at low RH (as are metabolic rate and thermal conductance). These results suggest regulation of a constant EWL independent of RH, a hitherto unappreciated capacity of endothermic vertebrates. Independence of EWL from RH conserves water and heat at low RH, and avoids physiological adjustments to changes in evaporative heat loss such as thermoregulation. Re-evaluation of previously published data for mammals and birds suggests that a lesser dependence of EWL on RH is observed more commonly than previously thought, suggesting that physiological independence of EWL of RH is not just an unusual capacity of a few species, such as the little kaluta, but a more general capability of many mammals and birds. PMID:24741015
Recycling nickel electroplating rinse waters by low temperature evaporation and reverse osmosis
Lindsey, T.C.; Randall, P.M.
Low temperature evaporation and reverse osmosis systems were each evaluated (on a pilot scale) on their respective ability to process rinse water collected from a nickel electroplating operation. Each system offered advantages under specific operating conditions. The low temperature evaporation system was best suited to processing solutions with relatively high (greater than 4,000 to 5,000 mg/L) nickel concentrations. The reverse osmosis system was best adapted to conditions where the feed solution had a relatively low (less than4,000 to 5,000 mg/L) nickel concentration. In electroplating operations where relatively dilute rinse water solutions must be concentrated to levels acceptable for replacement in the plating bath, a combination of the two technologies might provide the best process alternative.
Evaporation and condensation of steam-water in a vertical tube
G. Sun; G. F. Hewitt
Heat Transfer data have been obtained for water from single-phase flow to two-phase annular flow at 0.07¢0.09 MPa in a 9.5 mm vertical bore tube under conditions of evaporation and condensation in the same test section. The main aim of the experiments was to elucidate the mechanism of heat transfer in annular flow by distinguishing between the conventional explanation of
The Evaporation and Growth Kinetics of Nitric Acid-Water Droplets
H. Xue; D. Lamb
A laboratory study has been conducted to investigate the evaporation and growth kinetics of binary nitric acid-water solution droplets under 80-90 % relative humidities at room temperatures. The droplets initially consist of 4-30 wt% nitric acid and have radii of 20-30 microns. The experimental data show that the presence of nitric acid can prolong the lifetime of the droplets significantly
Burned and unburned peat water repellency: Implications for peatland evaporation following wildfire
NASA Astrophysics Data System (ADS)
Kettridge, N.; Humphrey, R. E.; Smith, J. E.; Lukenbach, M. C.; Devito, K. J.; Petrone, R. M.; Waddington, J. M.
Water repellency alters soil hydrology after periods of wildfire, potentially modifying the ecosystem recovery to such disturbance. Despite this potential importance, the extent and severity of water repellency within burned peatlands and its importance in regulating peatland recovery to wildfire disturbance remains poorly understood. We characterised the water repellency of peat in a burned (one year post-fire) and unburned peatland in the Western Boreal Plain utilising the water drop penetration time and ethanol droplet molarity tests. Burned Sphagnum moss and feather moss sites had a more severe degree of water repellency than unburned sites, with differences being more pronounced between burned and unburned feather moss sites. Burned feather moss exhibited the most extreme water repellency, followed by unburned feather moss, and burned Sphagnum. The severity of water repellency varied with depth through the near surface of the moss/peat profile. This was most evident within the burned feathermoss where more extreme water repellency was observed at the near-surface compared to the surface, with the most extreme water repellency found at 1 and 5 cm depths. Unburned Sphagnum was completely hydrophilic at all depths. We suggest that the extreme water repellency in near-surface feather moss peat acts as a barrier that impedes the supply of water to the surface that replaces that lost via evaporation. This leads to drying of the near-surface vadose zone within feather moss areas and a concomitantly large decrease in peatland evaporation within feather moss dominated peatlands. This negative feedback mechanism likely enhances the resilience of such peatland to wildfire disturbance, maintaining a high water table position, thereby limiting peat decomposition. In comparison, such a feedback is not observed strongly within Sphagnum, leaving Sphagnum dominated peatlands potentially vulnerable to low water table positions post disturbance.
Growth rates of atmospheric molecular clusters determined from cluster appearance times and collision-evaporation fluxes
NASA Astrophysics Data System (ADS)
Kontkanen, Jenni; Olenius, Tinja; Lehtipalo, Katrianne; Vehkamõki, Hanna; Kulmala, Markku
The probability of freshly formed particles to survive to climatically relevant sizes is determined by the competition between the coagulation loss rate and the particle growth rate. Therefore, various methods have been developed to deduce the growth rates from measured particle size distributions. Recently, the growth rates of sub-3nm clusters have been determined based on the appearance times of different cluster sizes. However, it is not clear to what extent these growth rates are consistent with the growth rates corresponding to molecular fluxes between clusters. In this work, we simulated the time evolution of a population of sub-3 nm molecular clusters and compared the growth rates determined (1) from the cluster appearance times and (2) from the collision-evaporation fluxes between different cluster sizes. We performed a number of simulations by varying the ambient conditions and the properties of the model substance. In the first simulation set, the Gibbs free energy of the formation of the clusters was assumed to have a single maximum and no minima, corresponding to a monotonically increasing stability as a function of cluster size. The saturation vapor pressure was selected so that the growth proceeded solely via monomer additions. The growth rates were determined separately for each cluster. However, to see the effect of finite size resolution, we also performed simulations where the clusters were grouped into size bins, for which we determined the growth rates. In the second simulation set, the saturation vapor pressure was lowered so that the collisions of small clusters significantly contributed to the growth. As the growth rate of a single cluster is ambiguous in this case, the growth rates were determined only for different size bins. We performed simulations using a similar free energy profile as in other simulations but we also used a free energy profile containing a local minimum, corresponding to small stable clusters. Our simulations show that there may be significant differences between the growth rates determined with the two approaches. The growth rates determined from the appearance times of clusters were generally higher than the flux-equivalent growth rates. The difference between the growth rates was largest for the smallest clusters but its magnitude varied depending on the properties of the model substance and on the ambient conditions, such as the external sink. The use of size bins increased the difference, especially if the width of the size bins was large. In the simulations where non-monomer collisions significantly contributed to the growth, the difference between the two growth rates was smallest in the conditions with high cluster concentrations. Furthermore, when the free energy profile had a minimum, the difference was generally smaller than in the simulations with no minima. While this work assesses the qualitative behavior of the size-dependent growth rates, and calls for caution in the interpretation of growth rates deduced from experiments, quantitative comparisons require information on the specific substance and conditions of interest.
Regional water balance trends and evaporation-transpiration partitioning from a stable isotope survey of lakes in northern Canada
J. J. Gibson; T. W. D. Edwards
Regional variations in evaporation losses and water budget are interpreted from systematic isotopic patterns in surface waters across a 275,000 km2 region of northern Canada. Differential heavy isotope enrichment in a set of >255 nonheadwater lakes sampled by floatplane during 1993 and 1994 is strongly correlated to varying hydroclimatic conditions across the region. Calculated catchment-weighted evaporation losses typically range from
Variability in cold front activities modulating cool-season evaporation from a southern inland water in the USA
Heping Liu; Peter D. Blanken; Tamas Weidinger; Annika Nordbo; Timo Vesala
Understanding seasonal variations in the evaporation of inland waters (e.g., lakes and reservoirs) is important for water resource management as well as the prediction of the hydrological cycles in response to climate change. We analyzed eddy covariance-based evaporation measurements from the Ross Barnett Reservoir (32░26'N, 90░02'W which is always ice-free) in central Mississippi during the cool months (i.e., September-March) of
Reduced energy consumption evaporator for use in desalting impaired waters. Technical completion report (Final)
Tleimat, B.W.; Tleimat, M.C.
The basic objective of this program is to demonstrate significant savings in energy consumption by the use of the wiped film rotating disk (WFRD) evaporator in a five-effect vapor compression distillation (MEVCD) system to recover the maximum amount of water from agricultural drainage water and other impaired waters. Tests were conducted using a 10,000 ppm aqueous solution of sodium sulfate and sodium chloride to simulate the composition of agricultural drainage water in the San Joaquin Valley, California. The feed was concentrated by a factor ranging from 15 to 20 resulting in a blowdown salinity of 150,000 to 200,000 ppm. The results showed the presence of dissolved salts has significant influence on energy consumption by the compressor of a commercial 60,000 gal/day VCD unit tested at Los Banos, California.
Relationship between a solar drying model of red pepper and the kinetics of pure water evaporation (1)
Passamai, V.; Saravia, L. [National Univ. of Salta (Argentina)
Drying of red pepper under solar radiation was investigated, and a simple model related to water evaporation was developed. Drying experiments at constant laboratory conditions were undertaken where solar radiation was simulated by a 1,000 W lamp. In this first part of the work, water evaporation under radiation is studied and laboratory experiments are presented with two objectives: to verify Penman`s model of evaporation under radiation, and to validate the laboratory experiments. Modifying Penman`s model of evaporation by introducing two drying conductances as a function of water content, allows the development of a drying model under solar radiation. In the second part of this paper, the model is validated by applying it to red pepper open air solar drying experiments.
Hollow Fiber Space Suit Water Membrane Evaporator Development for Lunar Missions
NASA Technical Reports Server (NTRS)
Bue, Grant C.; Trevino, Luis A.; Hanford, Anthony J.; Mitchell, Keith
The Space Suit Water Membrane Evaporator (SWME) is the baseline heat rejection technology selected for development for the Constellation lunar suit. The Hollow Fiber (HoFi) SWME is being considered for service in the Constellation Space Suit Element (CSSE) Portable Life Support Subsystem (PLSS) to provide cooling to the thermal loop through water evaporation to the vacuum of space. Previous work described the test methodology and planning to compare the test performance of three commercially available hollow fiber materials as alternatives to the sheet membrane prototype for SWME: 1) porous hydrophobic polypropylene, 2) porous hydrophobic polysulfone, and 3) ion exchange through nonporous hydrophilic modified Nafion. Contamination tests were performed to probe for sensitivities of the candidate SWME elements to organics and non-volative inorganics expected to be found in the target feedwater source, i.e., potable water provided by the vehicle. The resulting presence of precipitate in the coolant water could plug pores and tube channels and affect the SWME performance. From this prior work, a commercial porous hydrophobic hollow fiber was selected to satisfy both the sensitivity question and the need to provide 800 W of heat rejection. This paper describes the trade studies, the design methodology, and the hollow fiber test data used to design a full
Is the Evaporation Rate of Methane from Titan's Lakes Greatly Overestimated?
NASA Astrophysics Data System (ADS)
Rafkin, Scot C. R.
The only certain and known source of methane for the atmosphere of Titan on short timescales is the volatile organic lake reservoirs. In general, there will be a turbulent exchange of methane and sensible heat between the atmosphere and the surface of these lakes. The turbulent fluxes of methane and heat are controlled by a variety of factors that includes: the temperature of the lake and atmosphere, the molar fraction of methane in the lake, the methane vapor pressure of the air, the wind speed, the atmospheric stability, and the solar and infrared heat available to drive the system. In addition, the dynamics of both the lake and the atmosphere influence how the turbulent fluxes evolve over time. We present results from numerical simulations that explicitly calculate the turbulent fluxes of methane and energy at a lake surface under a variety of conditions. Results show that evaporative cooling of the lakes results in the production of a low level atmospheric inversion that drastically diminishes the magnitude of the fluxes by suppressing turbulent winds and lowering the bulk exchange coefficient. These results suggest that the rate at which lakes can supply methane to the atmosphere has been greatly overestimated. This work was supported by the NASA Planetary Atmospheres Program under Grant NNX10AB97G.
Water evaporation versus condensation in a hygroscopic soil A.L. Lozano, F. Cherblanc, J.-C. Benet
Paris-Sud XI, Universitķ de
Water evaporation versus condensation in a hygroscopic soil A.L. Lozano, F. Cherblanc, J.-C. B of water in soil is involved in many environmental geotech- nical processes. In the case of hygroscopic soils, the liquid water is strongly adsorbed on the solid phase and this particular thermodynamic state
Testing of Commercial Hollow Fiber Membranes for Space Suit Water Membrane Evaporator
NASA Technical Reports Server (NTRS)
Bue, Grant C.; Trevino, Luis; Tsioulos, Gus; Hanford, Anthony
Three commercial-off-the-shelf (COTS) hollow fiber (HoFi) membrane evaporators, modified for low pressure, were tested in a vacuum chamber at pressures below 33 pascals as potential space suit water membrane evaporator (SWME) heat rejection technologies. Water quality was controlled in a series of 25 tests, first simulating potable water reclaimed from waste water and then changing periodically to simulate the ever concentrating make-up of the circulating coolant over that is predicted over the course of 100 EVAs. Two of the systems, comprised of non-porous tubes with hydrophilic molecular channels as the water vapor transport mechanism, were severely impacted by the increasing concentrations of cations in the water. One of the systems, based on hydrophobic porous polypropylene tubes was not affected by the degrading water quality, or the presence of microbes. The polypropylene system, called SWME 1, was selected for further testing. An inverse flow configuration was also tested with SWME 1, with vacuum exposure on the inside of the tubes, provided only 20% of the performance of the standard configuration. SWME 1 was also modified to block 50% and 90% of the central tube layers, and tested to investigate performance efficiency. Performance curves were also developed in back-pressure regulation tests, and revealed important design considerations arising from the fully closed valve. SWME 1 was shown to be insensitive to air bubbles injected into the coolant loop. Development and testing of a full-scale prototype based on this technology and these test results is in progress.
Development of a preprototype thermoelectric integrated membrane evaporation subsystem for water recovery
NASA Technical Reports Server (NTRS)
Winkler, H. E.; Roebelen, G. J., Jr.
A three-man urine water recovery preprototype subsystem using a new concept to provide efficient potable water recovery from waste fluids on extended duration space flights has been designed, fabricated, and tested. Low power, compactness, and gravity insensitive operation are featured in this vacuum distillation subsystem that combines a hollow fiber polysulfone membrane evaporator with a thermoelectric heat pump. Application and integration of these key elements have solved problems inherent in previous reclamation subsystem designs. The hollow fiber elements provide positive liquid/gas phase control with no moving parts other than a waste liquid recirculation pump and a product water withdrawal pump. Tubular membranes provide structural integrity, improving on previous flat sheet membrane designs. A thermoelectric heat pump provides latent energy recovery.
Inhibiting ventilatory evaporation produces an adaptive increase in cutaneous evaporation in mourning doves Zenaida macroura.
Hoffman; Walsberg
We tested the hypothesis that birds can rapidly change the conductance of water vapor at the skin surface in response to a changing need for evaporative heat loss. Mourning doves (Zenaida macroura) were placed in a two-compartment chamber separating the head from the rest of the body. The rate of cutaneous evaporation was measured in response to dry ventilatory inflow at three ambient temperatures and in response to vapor-saturated ventilatory inflow at two ambient temperatures. At 35 degrees C, cutaneous evaporation increased by 72 % when evaporative water loss from the mouth was prevented, but no increase was observed at 45 degrees C. For both dry and vapor-saturated treatments, cutaneous evaporation increased significantly with increased ambient temperature. Changes in skin temperature made only a minor contribution to any observed increase in cutaneous evaporation. This indicates that Z. macroura can effect rapid adjustment of evaporative conductance at the skin in response to acute change in thermoregulatory demand. PMID:10518483
A New Approach to Quantify Evaporative Water Loss in Tropical Wetlands
NASA Astrophysics Data System (ADS)
Schwerdtfeger, J.; Weiler, M.; Johnson, M. S.; Couto, E. G.
Tropical wetlands are challenging research environments. Their high complexity and heterogeneity make the characterization of hydrological processes very difficult. In particular, large uncertainties complicate estimations of water loss by evapotranspiration (ET). ET influences the local and regional climate systems, and the quantification of ET is fundamental for the water balance of the continuous and intermittent water bodies. One of the largest freshwater wetlands in the world is the Pantanal located in central South America. Data availability is scarce and its remoteness makes direct measurements of ET even more challenging. Due to the variability and the complexity of this unique ecosystem, no adequate method for determining ET exists. In our study, we developed a process-based model to simulate ET that accounts for inundation dynamics, the type of water body, as well as vegetation cover for the dry and rainy seasons. A set of simple and complex empirical models were selected to calculate ensembles of potential evapotranspiration (PET) based on different assumptions and available datasets. We use high-resolution measurements of surface and groundwater levels of different types of water bodies to define the water availability. Stable water isotopes collected from these water bodies serve as qualitative information to describe the evaporation dynamics. Actual evapotranspiration (AET) was derived using the modeled PET with correction factors and the models were validated using local class A pan observations. Defining different types of water bodies on the basis of their differences in inundation time and dynamics, we apply the best-fitting model of our ensemble to each of the water body types. This finally allows us to quantify ET losses on a large spatial scale for dry and wet years. With this new spatially explicit approach we achieve an improvement in our understanding of the role of ET in the Pantanal wetland's water balance and quantify the actual water loss by ET.
Wetting mode transition of nanoliter scale water droplets during evaporation on superhydrophobic surfaces with random roughness structure
Tsutomu Furuta; Toshihiro Isobe; Munetoshi Sakai; Sachiko Matsushita; Akira Nakajima
During evaporation, shape changes of nanoliter-scale (80¢100nL) water droplets were evaluated on two superhydrophobic surfaces with different random roughness (nm-coating, ?m-coating). The square of the contact radius and the square of the droplet height decreased linearly with evaporation time. However, trend changes were observed at around 170s (nm-coating) and around 150s (?m-coating) suggesting a wetting mode transition. The calculated droplet
A New Approach to Measure Contact Angle and Evaporation Rate with Flow Visualization in a Sessile Drop
NASA Technical Reports Server (NTRS)
Zhang, Nengli; Chao, David F.
The contact angle and the spreading process of sessile droplet are very crucial in many technological processes, such as painting and coating, material processing, film-cooling applications, lubrication, and boiling. Additionally, as it is well known that the surface free energy of polymers cannot be directly, measured for their elastic and viscous restraints. The measurements of liquid contact angle on the polymer surfaces become extremely important to evaluate the surface free energy of polymers through indirect methods linked with the contact angle data. Due to the occurrence of liquid evaporation is inevitable, the effects of evaporation on the contact angle and the spreading become very important for more complete understanding of these processes. It is of interest to note that evaporation can induce Marangoni-Benard convection in sessile drops. However, the impacts of the inside convection on the wetting and spreading processes are not clear. The experimental methods used by previous investigators cannot simultaneously measure the spreading process and visualize the convection inside. Based on the laser shadowgraphic system used by the present author, a very simple optical procedure has been developed to measure the contact angle, the spreading speed, the evaporation rate, and to visualize inside convection of a sessile drop simultaneously. Two CCD cameras were used to synchronously record the real-time diameter of the sessile drop, which is essential for determination of both spreading speed and evaporation rate, and the shadowgraphic image magnified by the sessile drop acting as a thin plano-convex lens. From the shadowgraph, the inside convection of the drop can be observed if any and the image outer diameter, which linked to the drop profile, can be measured. Simple equations have been derived to calculate the drop profile, including the instantaneous contact angle, height, and volume of the sessile drop, as well as the evaporation rate. The influence of the inside convection on the wetting and spreading processes can be figured out through comparison of the drop profiles with and without inside convection when the sessile drop is placed at different evaporation conditions.
Water accounting and vulnerability evaluation (WAVE): considering atmospheric evaporation recycling and the risk of freshwater depletion in water footprinting.
Berger, Markus; van der Ent, Ruud; Eisner, Stephanie; Bach, Vanessa; Finkbeiner, Matthias
Aiming to enhance the analysis of water consumption and resulting consequences along the supply chain of products, the water accounting and vulnerability evaluation (WAVE) model is introduced. On the accounting level, atmospheric evaporation recycling within drainage basins is considered for the first time, which can reduce water consumption volumes by up to 32%. Rather than predicting impacts, WAVE analyzes the vulnerability of basins to freshwater depletion. Based on local blue water scarcity, the water depletion index (WDI) denotes the risk that water consumption can lead to depletion of freshwater resources. Water scarcity is determined by relating annual water consumption to availability in more than 11,000 basins. Additionally, WDI accounts for the presence of lakes and aquifers which have been neglected in water scarcity assessments so far. By setting WDI to the highest value in (semi)arid basins, absolute freshwater shortage is taken into account in addition to relative scarcity. This avoids mathematical artifacts of previous indicators which turn zero in deserts if consumption is zero. As illustrated in a case study of biofuels, WAVE can help to interpret volumetric water footprint figures and, thus, promotes a sustainable use of global freshwater resources. PMID:24660893
Analysis of Water Recovery Rate from the Heat Melt Compactor
NASA Technical Reports Server (NTRS)
Balasubramaniam, R.; Hegde, U.; Gokoglu, S.
Human space missions generate trash with a substantial amount of plastic (20% or greater by mass). The trash also contains water trapped in food residue and paper products and other trash items. The Heat Melt Compactor (HMC) under development by NASA Ames Research Center (ARC) compresses the waste, dries it to recover water and melts the plastic to encapsulate the compressed trash. The resulting waste disk or puck represents an approximately ten-fold reduction in the volume of the initial trash loaded into the HMC. In the current design concept being pursued, the trash is compressed by a piston after it is loaded into the trash chamber. The piston face, the side walls of the waste processing chamber and the end surface in contact with the waste can be heated to evaporate the water and to melt the plastic. Water is recovered by the HMC in two phases. The first is a pre-process compaction without heat or with the heaters initially turned on but before the waste heats up. Tests have shown that during this step some liquid water may be expelled from the chamber. This water is believed to be free water (i.e., not bound with or absorbed in other waste constituents) that is present in the trash. This phase is herein termed Phase A of the water recovery process. During HMC operations, it is desired that liquid water recovery in Phase A be eliminated or minimized so that water-vapor processing equipment (e.g., condensers) downstream of the HMC are not fouled by liquid water and its constituents (i.e., suspended or dissolved matter) exiting the HMC. The primary water recovery process takes place next where the trash is further compacted while the heated surfaces reach their set temperatures for this step. This step will be referred to herein as Phase B of the water recovery process. During this step the waste chamber may be exposed to different selected pressures such as ambient, low pressure (e.g., 0.2 atm), or vacuum. The objective for this step is to remove both bound and any remaining free water in the trash by evaporation. The temperature settings of the heated surfaces are usually kept above the saturation temperature of water but below the melting temperature of the plastic in the waste during this step to avoid any encapsulation of wet trash which would reduce the amount of recovered water by blocking the vapor escape. In this paper, we analyze the water recovery rate during Phase B where the trash is heated and water leaves the waste chamber as vapor, for operation of the HMC in reduced gravity. We pursue a quasi-one-dimensional model with and without sidewall heating to determine the water recovery rate and the trash drying time. The influences of the trash thermal properties, the amount of water loading, and the distribution of the water in the trash on the water recovery rates are determined.
Evaporative water loss in man in a gravity-free environment
NASA Technical Reports Server (NTRS)
Leach, C. S.; Leonard, J. I.; Rambaut, P. C.; Johnson, P. C.
Daily evaporative water losses (EWL) during the three Skylab missions were measured indirectly using mass and water-balance techniques. The mean daily values of EWL for the nine crew members who averaged 1 hr of daily exercise were: preflight 1,750 + or - 37 (SE) ml or 970 + or - 20 ml/sq m and inflight 1,560 + or - 26 ml or 860 + or - 14 ml/sq m. Although it was expected the EWL would increase in the hypobaric environment of Skylab, an average decrease from preflight sea-level conditions of 11% was measured. The results suggest that weightlessness decreased sweat losses during exercise and possibly reduced insensible skin losses. The weightlessness environment apparently promotes the formation of an observed sweat film on the skin surface during exercise by reducing convective flow and sweat drippage, resulting in high levels of skin wettedness that favor sweat suppression.
Determination of trace level bromate and perchlorate in drinking water by ion chromatography with an evaporative preconcentration technique
Yongjian Liu; Shifen Mou; Shawn Heberling
A simple sample preconcentration technique employing microwave-based evaporation for the determination of trace level bromate and perchlorate in drinking water with ion chromatography is presented. With a hydrophilic anion-exchange column and a sodium hydroxide eluent in linear gradient, bromate and perchlorate can be determined in one injection within 35 min. Prior to ion chromatographic analysis, the drinking water sample was
Heat and mass transfer characteristics of a new combined absorber-evaporator exchanger operating near the triple point of water
Y.-M. Chen; C.-Y. Sun
The present experimental study investigates the controlling mechanism involved in a new combined vertical film-type absorber-evaporator exchanger operating near the condition of the triple point of water. This peculiar exchanger plays the most important role in the VFVPE process that can be utilized in many industrial applications, water pollution prevention, desalination, and purification of chemicals, for example. The method of
Hollow Fiber Space Water Membrane Evaporator Flight Prototype Design and Testing
NASA Technical Reports Server (NTRS)
Bue, Grant C.; Makinen, Janice; Vogel, Mtthew; Honas, Matt; Dillon, Paul; Colunga, Aaron; Truong, Lily; Porwitz, Darwin; Tsioulos, Gus
The spacesuit water membrane evaporator (SWME) is being developed to perform thermal control for advanced spacesuits and to take advantage of recent advances in micropore membrane technology. This results in a robust heat-rejection device that is potentially less sensitive to contamination than is the sublimator. The current design was based on a previous design that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape. This was developed into a full-scale prototype consisting of 14,300 tube bundled into 30 stacks, each of which is formed into a chevron shape and separated by spacers and organized into three sectors of 10 nested stacks. The new design replaced metal components with plastic ones, eliminated the spacers, and has a custom built flight like backpressure valve mounted on the side of the SWME housing to reduce backpressure when fully open. A number of tests were performed in order to improve the strength of the polyurethane header that holds the fibers in place while the system is pressurized. Vacuum chamber testing showed similar heat rejection as a function of inlet water temperature and water vapor backpressure was similar to the previous design. Other tests pushed the limits of tolerance to freezing and showed suitability to reject heat in a Mars pressure environment with and without a sweep gas. Tolerance to contamination by constituents expected to be found in potable water produced by distillation processes was tested in a conventional way by allowing constituents to accumulate in the coolant as evaporation occurs. For this purpose, the SWME cartridge has endured an equivalent of 30 EVAs exposure and demonstrated acceptable performance decline.
Evaporative cooling in insects
Henry D. Prange
Insects commonly use behavior to avoid the heat stress and consequent water loss of hot environments. It has been assumed by many to be impossible or impractical for insects to employ evaporative cooling. Despite this assumption, there have been many instances, historically and recently where insects are reported to survive otherwise lethal temperatures by evaporating water. The site of evaporation
On the evaporation of ammonium sulfate solution
Drisdell, Walter S.; Saykally, Richard J.; Cohen, Ronald C.
Aqueous evaporation and condensation kinetics are poorly understood, and uncertainties in their rates affect predictions of cloud behavior and therefore climate. We measured the cooling rate of 3 M ammonium sulfate droplets undergoing free evaporation via Raman thermometry. Analysis of the measurements yields a value of 0.58 {+-} 0.05 for the evaporation coefficient, identical to that previously determined for pure water. These results imply that subsaturated aqueous ammonium sulfate, which is the most abundant inorganic component of atmospheric aerosol, does not affect the vapor-liquid exchange mechanism for cloud droplets, despite reducing the saturation vapor pressure of water significantly.
Performance of a Water Recirculation Loop Maintenance Device and Process for the Advanced Spacesuit Water Membrane Evaporator
NASA Technical Reports Server (NTRS)
Rector, Tony; Steele, John W.; Bue, Grant C.; Campbell, Colin; Makinen, Janice
A water loop maintenance device and process to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop has been undergoing a performance evaluation. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the water recirculation maintenance device and process is to further enhance this advantage through the leveraging of fluid loop management lessons-learned from the International Space Station (ISS). A bed design that was developed for a Hamilton Sundstrand military application, and considered for a potential ISS application with the Urine Processor Assembly, provides a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance process further leverages a sorbent developed for ISS that introduces a biocide in a microgravity-compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware. This
Measurements of Evaporation Kinetics of Aqueous Aerosols
NASA Astrophysics Data System (ADS)
Duffey, K.; Shih, O.; Liu, F.; Saykally, R.; Cohen, R. C.
The rates of water evaporation and condensation govern the growth, size distribution, and number concentration of cloud droplets, yet the details of these fundamental processes remain poorly understood. In this work, the effect of acetic acid on the evaporation rate of water is studied using a liquid microjet technique. A collimated train of micron-sized droplets containing 1M acetic acid is injected into a vacuum chamber, and their temperature is measured at various distances from the jet nozzle using Raman thermometry. The data are compared to an evaporative cooling model to determine the evaporation coefficient, ?. In previous studies, ? was determined for pure water, D2O, 3M ammonium sulfate, and 4M sodium perchlorate to be 0.62 ▒0.09, 0.57 ▒0.06, 0.58 ▒0.05, and 0.47 ▒0.02, respectively. It is hypothesized that more surface-active species have a greater effect on evaporation rates. Acetic acid has been shown to be surface-active and is therefore representative of the small, surfactant-like molecules often found in aerosols. Preliminary results show a slight reduction in the evaporation coefficient for acetic acid compared to pure water. These experimental findings are being compared with calculations from the Chandler group at UC Berkeley in order to better understand the molecular mechanism of water evaporation.
Magnetic resonance imaging of slow water flow during infiltration and evaporation by tracer motion
NASA Astrophysics Data System (ADS)
Pohlmeier, A.; Haber-Pohlmeier, S.; Bechtold, M.; Vanderborght, J.; Vereecken, H.
Water fluxes in soils control many processes in the environment like plant nutrition, solute and pollutant transport. In the last two decades non-invasive visualization methods have been adapted to monitor flux processes on the small scale. Magnetic resonance imaging (MRI), also well known from medical diagnostics, is one of the most versatile ones. It mostly probes directly the substance of interest: water, and it offers many opportunities to manipulate the observed signals for creating different contrasts and thus probing different properties of the porous medium and the embedded fluids. For example, one can make the signal sensitive to the total proton density, i. e. water content, to spatial distributions of relaxation times which reflect pore sizes, to spatial distributions of transport coefficients, and to concentration of contrast agents by using strongly T1 weighted MRI pulse sequences. In this presentation we use GdDTPA2- for monitoring flux processes in soil columns in an ultra-wide bore MRI scanner. It offers the opportunity for monitoring slow water fluxes mainly occurring in soil systems which are not monitorable with direct MRI flow imaging. This contrast agent is most convenient since it behaves conservatively, i.e. it does not sorb at different soil materials and it is chemically stable. Firstly, we show that its mode of action in natural porous media is identical to that known from medical applications as proved by the identical relaxivity parameters [1]. Secondly, the tracer is applied for the visualization of flux processes during evaporation-driven flow. Theoretical considerations by forward simulation predicted a lateral redistribution of solutes during evaporative upward fluxes from highly conductive fine material to neighbouring domains with low water content and conductivity. Here we could prove that such near-surface redistribution really takes place [2]. Thirdly, this tracer is applied for the investigation of water uptake by root systems. Depending on the transpiration conditions slow uptake in the dark is present, where the tracer moves directly into the xylem. When fully illuminated, the tracer uptake is limited by the Caspari band, and it is enriched strongly in the roots cortex. The results so far show that this tracer offers a new window for monitoring slow water fluxes in bare and grown soil columns. [1] Haber-Pohlmeier S, Bechtold M, Stapf, S, Pohlmeier, A. (2010) Vadose Zone Journal 9, 835-845 [2] Bechtold M, Haber-Pohlmeier S, Vanderborght J, Pohlmeier A, Ferrķ T, Vereecken H. (2011) Geophysical Research Letters 38, L17404
Design and Evaluation of a Water Recirculation Loop Maintenance Device for the Advanced Spacesuit Water Membrane Evaporator
NASA Technical Reports Server (NTRS)
Steele, John W.; Rector, Tony; Bue, Grant C.; Campbell, Colin; Makinen, Janice
A dual-bed device to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop has been designed and is undergoing testing. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the development of a water recirculation maintenance device is to further enhance this advantage through the leveraging of fluid loop management lessons-learned from the International Space Station (ISS). A bed design that was developed for a Hamilton Sundstrand military application, and considered for a potential ISS application with the Urine Processor Assembly, provides a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The bed design further leverages a sorbent developed for ISS that introduces a biocide in a microgravity-compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a clear demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware.
Hollow Fiber Spacesuit Water Membrane Evaporator Development and Testing for Advanced Spacesuits
NASA Technical Reports Server (NTRS)
Bue, Grant C.; Trevino, Luis A.; Tsioulos, Gus; Settles, Joseph; Colunga, Aaron; Vogel, Matthew; Vonau, Walt
The spacesuit water membrane evaporator (SWME) is being developed to perform the thermal control function for advanced spacesuits to take advantage of recent advances in micropore membrane technology in providing a robust heat-rejection device that is potentially less sensitive to contamination than is the sublimator. Principles of a sheet membrane SWME design were demonstrated using a prototypic test article that was tested in a vacuum chamber at JSC in July 1999. The Membrana Celgard X50-215 microporous hollow fiber (HoFi) membrane was selected after recent contamination tests as the most suitable candidate among commercial alternatives for HoFi SWME prototype development. A design that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape, was developed into a full-scale prototype consisting 14,300 tube bundled into 30 stacks, each of which are formed into a chevron shape and separated by spacers and organized into three sectors of ten nested stacks. Vacuum chamber testing has been performed characterize heat rejection as a function of inlet water temperature and water vapor backpressure and to show contamination resistance to the constituents expected to be found in potable water produced by the distillation processes. Other tests showed the tolerance to freezing and suitability to reject heat in a Mars pressure environment.
Determination of evaporation from a catchment water balance at a monthly time scale
NASA Astrophysics Data System (ADS)
Savenije, H. H. G.
A method is presented to determine total evaporation from the earth's surface at a spatial scale that is adequate for linkage with climate models. The method is based on the water balance of catchments, combined with a calibrated autoregressive rainfall-runoff model. The time scale used is in the order of decades (10 days) to months. The rainfall-runoff model makes a distinction between immediate processes (interception and short term storage) and the remaining longer-term processes. Besides the calibrated rainfall-runoff model and the time series of observed rainfall and runoff, the method requires a relation between transpiration and soil moisture storage. The method is applied to data of the Bani catchment in Mali, a sub-catchment of the Niger river basin.
Mathematical Modeling of Evaporative Cooling of Water in a Mechanical-Draft Tower
A. I. Petruchik; S. P. Fisenko
A mathematical model of the operation of a mechanical-draft tower is proposed. The model represents a boundary-value problem for five differential equations and for the first time takes into account the following parameters: temperature of inflowing water, its discharge, mean radius of water droplets, mean air velocity inside the water-cooling tower, rate of fall of a droplet, height from which
Two-dimensional LIF measurements of humidity and OH density resulting from evaporated water from a wet surface in plasma for medical use
NASA Astrophysics Data System (ADS)
Yagi, Ippei; Ono, Ryo; Oda, Tetsuji; Takaki, Koichi
In plasma medicine, plasma is applied to a wet surface and is often accompanied by dry-gas flow. The dry-gas flow affects water evaporation from the wet surface and influences production of reactive species derived from water vapor, such as OH radicals. In this study, the effect of the dry-gas flow on two-dimensional distributions of humidity and OH radical density are examined by measuring them using laser-induced fluorescence (LIF). First, humidity is measured when nitrogen flows from a quartz tube of 4 mm inner diameter onto distilled water and agar media from 5 mm distance. NO gas is added to the nitrogen as a tracer and humidity is obtained from the quenching rate of NO molecules measured using LIF. This measurement has a spatial resolution of 0.2 mm3 and a temporal resolution of less than 220 ns. The two-dimensional humidity distribution shows that the dry-gas flow pushes away water vapor evaporating from the wet surface. As a result, a low-humidity region is formed near the quartz tube nozzle and a high-humidity region is formed near the wet surface. The thickness of the low-humidity region reduces with increasing gas flow rate. It is 0.1¢0.5 mm for the flow rate of higher than 0.3 l min?1. Next, the OH density is measured when a nanosecond pulsed streamer discharge is applied to a distilled water surface with dry-air flow. The OH density decreases with increasing gas flow rate due to decreased humidity. When the flow rate is lower than 0.1 l min?1, the OH distribution is approximately uniform in the plasma region, while the humidity distribution shows a large gradient. The importance of the thin high-humidity region on the flux of reactive species onto the wet surface is discussed.
Evaporation determined by the energy-budget method for Mirror Lake, New Hampshire
Winter, T.C.; Buso, D.C.; Rosenberry, D.O.; Likens, G.E.; Sturrock, A.M., Jr.; Mau, D.P.
Evaporation was determined by the energy-budget method for Mirror Lake during the open water periods of 1982-1987. For all years, evaporation rates were low in spring and fall and highest during the summer. However, the times of highest evaporation rates varied during the 6 yr. Evaporation reached maximum rates in July for three of the years, in June for two of the years, and in August for one of the years. The highest evaporation rate during the 6-yr study was 0.46 cm d-1 during 27 May-4 June 1986 and 15-21 July 1987. Solar radiation and atmospheric radiation input to the lake and long-wave radiation emitted from the lake were by far the largest energy fluxes to and from the lake and had the greatest effect on evaporation rates. Energy advected to and from the lake by precipitation, surface water, and ground water had little effect on evaporation rates. In the energy-budget method, average evaporation rates are determined for energy-budget periods, which are bounded by the dates of thermal surveys of the lake. Our study compared evaporation rates calculated for short periods, usually ???1 week, with evaporation rates calculated for longer periods, usually ???2 weeks. The results indicated that the shorter periods showed more variability in evaporation rates, but seasonal patterns, with few exceptions, were similar.
Relationship between a solar drying model of red pepper and the kinetics of pure water evaporation (2)
Passamai, V.; Saravia, L. [National Univ. of Salta (Argentina)
In part one, a simple drying model of red pepper related to water evaporation was developed. In this second part the drying model is applied by means of related experiments. Both laboratory and open air drying experiments were carried out to validate the model and simulation results are presented.
Stable isotope estimates of evaporation: inflow and water residence time for lakes across the United States as a tool for national lake water quality assessments
Stable isotope ratios of water (delta18O and delta2H) can be very useful in large-scale monitoring programs because water samples are easy to collect and isotope ratios integrate information about basic hydrologic processes such as evaporation as a percentage of inflow (E/I) and ...
Passive cooling effect of RC roof covered with the ceramics having high water retention and evaporation capacity
NASA Astrophysics Data System (ADS)
Yamazaki, M.; Kanaya, M.; Shimazu, T.; Ohashi, T.; Kato, N.; Horikoshi, T.
Hot days in metropolitan cities have increased remarkably by the heat island phenomenon these days. Thus the authors tried to develop the porous ceramics with high water retention and evaporation capacity as a maintenance-free material to improve thermal environment. The developed ceramic pellets have high water retention of more than 60 % of water absorption and high water evaporation which is similar to water surface. In this study, three types of 5 meter squared large flat-roofed structural specimen simulated reinforced concrete (RC) slab were constructed on the outside. The variation of water content and temperature of the specimens and atmosphere temperature around the specimens were measured from summer in 2009. In the case of the ceramic pellets, the temperature under RC slab was around 15 degree C lower than that of the control. The results were probably contributed by passive cooling effect of evaporated rain water, and the effect was similar to in the case of the grasses. From the viewpoint of thermal environment improvement, substitution of a rooftop gardening by the porous ceramics could be a promising method.
Effects of heating method and conditions on the evaporation rate and quality attributes of black mulberry ( Morus nigra ) juice concentrate
Mahboubeh Fazaeli; Ghazale Hojjatpanah; Zahra Emam-Djomeh
Black mulberry juice was concentrated by different heating methods, including conventional heating and microwave heating,\\u000a at different operational pressures (7.3, 38.5 and 100ĀkPa). The effects of each method on evaporation rate, quality attributes\\u000a of concentrated juice were investigated. The final juice concentration of 42░ Brix was achieved in 140, 120, and 95Āmin at\\u000a 100, 38.5, and 7.3ĀkPa respectively by using
Water retention curves of loamy-sandy soils: Transient evaporation method versus steady-state tension and pressure techniques
NASA Astrophysics Data System (ADS)
Winkler, G.; Eberhard, E.; Fank, J.; Birk, S.
Water retention curves of loamy-sandy soils at the agricultural test site Wagna (Austria) were measured using both the simplified evaporation method according to Schindler (Arch. Acker- u. Pflanzenbau u. Bodenkd. Berlin 24, 1-7, 1980) and steady-state tension and pressure techniques. The soil was sampled with 250-ccm and 100-ccm steel pipes for the evaporation method and the steady-state technique, respectively. In the transient evaporation method two tensiometers with a measurement range between 0 and 850 hPa are installed at a depth of 1.25 cm and 3.75 cm in a sample of 5 cm in height; the mean values of the two tensiometers and the water contents measured by weighing are used to obtain the water retention curve. The steady-state method employs a tension table (sand box) at tensions below 100 hPa and a pressure extractor at tensions between 300 hPa and 15,000 hPa; the water content is measured by weighing after the sample has equilibrated at the tension value set on the table or plate. First results of both methods suggest that the soil samples release water over the entire tension range measured. In particular, the release of water at very low tension values may suggest the presence of macropores. Despite the generally good agreement between the two methods, the values appear to deviate systematically close to saturation. This is potentially caused by the large relative error of the tension measurement close to saturation. Alternatively, the different size of the samples used for the evaporation experiment (250 ccm) and the steady-state method (100 ccm) might play a role. Because of the limited measurement range of the tensiometers used for the evaporation method, the measured curve must be extrapolated between 850 hPa and 15,000 hPa to allow comparison with the steady-state method. To this end, it was attempted to match the Brooks-Corey, the Van-Genuchten, and a bimodal Van-Genuchten retention function to the data from the evaporation experiments. This involves a simultaneous fit of both water-retention and hydraulic-conductivity function. Only the bimodal Van-Genuchten model was found to be able to produce satisfactory fits to the data. The extrapolated water retention curves, however, do not match the data from the steady-state method. This suggests that alternative soil hydraulic functions are needed to provide an adequate representation of the water retention characteristics of the loamy-sandy soils considered in this investigation.
Concentrating solar collector system for the evaporation of low-level radioactive waste water
Diamond, S.C.; Cappiello, C.C.
The Los Alamos National Laboratory has recently been awarded a grant under the Solar Federal Buildings Program to design, construct, and operate a high-temperature solar energy system for the processing of low-level radioactive waste water. Conceptual design studies have been completed, and detailed design work is under way for a solar system to produce process heat to evaporate 38,000 gal (143,830 L) of waste water per month. The system will use approximately 11,000 ft/sup 2/ (1022 m/sup 2/) of concentrating parabolic trough collectors operating at about 500/sup 0/F (262/sup 0/C). Construction of the system is anticipated to begin in 1981. Performance optimization of collector array size and configuration, storage medium and capacity, system operation, and control schemes are done using the active solar system simulator in the DOE-2 building energy analysis computer program. Results of this optimization are reported. This project represents a unique application of solar energy to an increasingly significant problem area in the energy field.
Potential evaporation functions compared on US watersheds: Possible implications for global-scale water balance and terrestrial ecosystem modeling
C. J. V÷r÷smarty; C. A. Federer; A. L. Schloss
Estimates of potential evaporation Ep are commonly employed in terrestrial water balance and net primary productivity models. This study compared a set of 11 Ep methods in a global-scale water balance model (WBM) applied to 3265 0.5░ (lat. ū long.) grid cells representing the conterminous US. The Ep methods ranged from simple temperature-driven equations to physically-based combination approaches and include
Evaluation of the freeze-thaw\\/evaporation process for the treatment of produced waters. Final report, August 1992August 1996
J. E. Boysen; K. L. Walker; J. L. Mefford; J. R. Kirsch; J. A. Harju
The use of freeze-crystallization is becoming increasingly acknowledged as a low-cost, energy-efficient method for purifying contaminated water. The natural freezing process can be coupled with natural evaporative processes to treat oil and gas produced waters year round in regions where subfreezing temperatures seasonally occur. The climates typical of Colorado`s San Juan Basin and eastern slope, as well as the oil
Modelling evaporation from reservoirs
It is shown that a numerical model for predicting the depth time variation of water temperature in a fresh water lake or reservoir can be used also for prediction of water losses due to evaporation. The seasonal change in peak evaporation from summer (in small lakes) to winter (in large lakes) is satisfactorily simulated.
O of water vapour, evapotranspiration and the sites of leaf water evaporation in a soybean canopy
Lee, Xuhui
, but larger differences on indi- vidual days.We also found that vertical variability in relative humidity transpiration transfers a significant portion of water from the soil to the atmosphere with consequences for regional humidity and precipitation patterns. In the central USA, the relative humidity has increased by 0
deltaO of water vapour, evapotranspiration and the sites of leaf water evaporation in a soybean canopy.
Welp, Lisa R; Lee, Xuhui; Kim, Kyounghee; Griffis, Timothy J; Billmark, Kaycie A; Baker, John M
Stable isotopes in water have the potential to diagnose changes in the earth's hydrological budget in response to climate change and land use change. However, there have been few measurements in the vapour phase. Here, we present high-frequency measurements of oxygen isotopic compositions of water vapour (delta(v)) and evapotranspiration (delta(ET)) above a soybean canopy using the tunable diode laser (TDL) technique for the entire 2006 growing season in Minnesota, USA. We observed a large variability in surface delta(v) from the daily to the seasonal timescales, largely explained by Rayleigh processes, but also influenced by vertical atmospheric mixing, local evapotranspiration (ET) and dew formation. We used delta(ET) measurements to calculate the isotopic composition at the sites of evaporative enrichment in leaves (delta(L,e)) and compared that with the commonly used steady-state prediction (delta(L,s)). There was generally a good agreement averaged over the season, but larger differences on individual days. We also found that vertical variability in relative humidity and temperature associated with canopy structure must be addressed in canopy-scale leaf water models. Finally, we explored this data set for direct evidence of the Pķclet effect. PMID:18507810
Experimental and numerical performance of a multi-effect condensation¢evaporation solar water distillation system
Adel M. Abdel Dayem
The main objective of the work is to demonstrate experimentally and numerically the performance of a simple solar distillation unit that is based on the multiple condensation¢evaporation cycle. The pilot plant was designed, fabricated, tested and simulated at the solar energy laboratory, Mattarria Faculty of Engineering, Cairo, Egypt. The distillation chamber consists of a humidifier (evaporator) and a dehumidifier (condenser)
Characteristic lengths for evaporation suppression from patchy porous surfaces
NASA Astrophysics Data System (ADS)
Lehmann, Peter; Or, Dani
For non-uniformly wet porous surfaces, evaporation rates vary nonlinearly with mean surface water content and with the areal fraction of wet patches. The nonlinearity stems from the complex vapor field forming over individual pores and patches that could enhance vapor fluxes from pores surrounded by dry area (relative to fluxes from the same area of free water surface). The resulting evaporation rates from such a surface are similar to free water surface evaporation despite considerably lower evaporating area (low surface water content). Theoretically, such flux compensation could be suppressed by lumping isolated pores into clusters with equal mean water content. The resulting arrangement in wet patches ensures nearly 1D conditions within the patch and some flux enhancement at the periphery. The interplay between patch water content, patch size, and mean surface water content within a prescribed air flow boundary layer was modeled analytically using single pore diffusion as a building block. Results show existence of a characteristic cluster size that yields the largest evaporation suppression for a given boundary layer thickness and spacing between patches. For patches larger than this size, the relative evaporation rate from patchy surface (relative to free water surface evaporation) reaches a predictable rate equal to the fractional area of clusters. Model predictions for the relation between pore cluster size and evaporation suppression were evaluated numerically and in a series of wind tunnel experiments using porous surfaces with different pore clusters. The findings could be used for the design of optimal porous covers for suppressing evaporation losses from water reservoirs, or for controlling evaporative drying from engineered porous surfaces.
Combined Evaporation and Salt Precipitation in Porous Media
NASA Astrophysics Data System (ADS)
Weisbrod, N.; Dragila, M. I.; Nachshon, U.; Or, D.; Shaharani, E.; Grader, A.
The vadose zone pore water contains dissolved salts and minerals; therefore, evaporation results in high rates of salt accumulation that may change the physical and chemical properties of the porous media. Here, a series of experiments, together with a mathematical model, are presented to shed new light on these processes. Experiments included: (1) long-term column evaporation experiments to quantify changes in evaporation rates due to salt precipitation; (2) CT scans of evaporated porous media samples saturated with salt solutions, to observe salt precipitation from micro to macro scales; and (3) Infrared thermography analysis to quantify evaporation rates from porous media surfaces for homogeneous and heterogeneous conditions and constant water table, in the presence of salt precipitation. As expected, the majority of salt crystallization occurs in the upper parts of the matrix, near the evaporation front. For heterogeneous porous matrices, salt precipitation will occur mainly in the fine pore regions as preferential evaporation takes place in these locations. In addition, it was found that the precipitated NaCl salt crust diffusion coefficient for water vapor is one to two orders of magnitude lower than the vapor diffusion coefficient in free air, depending on environmental conditions and salt crystallization rates. Three new stages of evaporation were defined for saline solutions: SS1, SS2 and SS3. SS1 exhibits a low and gradual decrease in the evaporation rate due to osmotic pressure. During SS2, the evaporation rate falls progressively due to salt precipitation; SS3 is characterized by a constant low evaporation rate and determined by the diffusion rate of water vapor through the precipitated salt layer. Even though phenomenologically similar to the classical evaporation stages of pure water, these stages correspond to different mechanisms and the transition between stages can occur regardless the hydraulic conditions. As well, it was shown that matrix heterogeneity lessens the salt effect on evaporation as coarse pore regions are relatively free of salt crystals, facilitating vapor transport towards the atmosphere. This was verified by the thermography analysis that enabled independent quantification of evaporation rates from coarse and fine sections of the media during salt precipitation. This is in contrast to homogeneous conditions, where the salt is distributed homogeneously in the matrix's upper parts, resulting in an increase in matrix resistivity to vapor flow. This research sheds new light on the dynamics of the evaporation process of a saline solution and the importance of considering that natural pore solutions typically include electrolytes.
Effects of oxygen flow rate on microstructure and optical properties of aluminum oxide films deposited by electron beam evaporation technique
Namita Maiti; A. Biswas; R. B. Tokas; D. Bhattacharyya; S. N. Jha; U. P. Deshpande; U. D. Barve; M. S. Bhatia; A. K. Das
Reactive evaporation technique has been used to deposit thin films of alumina (Al2O3) on crystalline Si substrates at ambient temperatures in an electron beam (e-beam) evaporation system using alumina granules as evaporant material. The loss of oxygen due to dissociation of alumina has been compensated by bleeding high purity oxygen gas into the system during evaporation. A set of samples
[Effect of shifting sand burial on evaporation reduction and salt restraint under saline water irrigation in extremely arid region].
Zhang, Jian-Guo; Zhao, Ying; Xu, Xin-Wen; Lei, Jia-Qiang; Li, Sheng-Yu; Wang, Yong-Dong
The Taklimakan Desert Highway Shelterbelt is drip-irrigated with high saline groundwater (2.58-29.70 g x L(-1)), and shifting sand burial and water-salt stress are most common and serious problems in this region. So it is of great importance to study the effect of shifting sand burial on soil moisture evaporation, salt accumulation and their distribution for water saving, salinity restraint, and suitable utilization of local land and water resources. In this study, Micro-Lysimeters (MLS) were used to investigate dynamics of soil moisture and salt under different thicknesses of sand burial (1, 2, 3, 4, and 5 cm), and field control experiments of drip-irrigation were also carried out to investigate soil moisture and salt distribution under different thicknesses of shifting sand burial (5, 10, 15, 20, 25, 30, 35, and 40 cm). The soil daily and cumulative evaporation decreased with the increase of sand burial thickness in MLS, cumulative evaporation decreased by 2.5%-13.7% compared with control. And evaporative inhibiting efficiency increased with sand burial thickness, evaporative inhibiting efficiency of 1-5 cm sand burial was 16.7%-79.0%. Final soil moisture content beneath the interface of sand burial increased with sand burial thickness, and it increased by 2.5%-13.7% than control. The topsoil EC of shifting sand in MLS decreased by 1.19-6.00 mS x cm(-1) with the increasing sand burial thickness, whereas soil salt content beneath the interface in MLS increased and amplitude of the topsoil salt content was higher than that of the subsoil. Under drip-irrigation with saline groundwater, average soil moisture beneath the interface of shifting sand burial increased by 0.4% -2.0% compare with control, and the highest value of EC was 7.77 mS x cm(-1) when the sand burial thickness was 10 cm. The trend of salt accumulation content at shifting sand surface increased firstly, and then decreased with the increasing sand burial thickness. Soil salt contents beneath the interface of shifting sand burial were much lower than that of shifting sand surface. 35 cm was the critical sand burial thickness for water-saving and salt restraint. In summary, sand burial had obvious inhibition effects on soil evaporation and salt accumulation, so maybe it could be used to save water and reduce salt accumulation in arid shifting desert areas. PMID:25129944
Continuous, high-resolution spatial mapping of water isotopes: improving tools for quantifying local evaporation and residence times
NASA Astrophysics Data System (ADS)
Dennis, Kate J.; Carter, Jeffrey A.; Winkler, Renato; Downing, Brian; Kendall, Carol; Bergamaschi, Brian
Stable isotopes of water (d2H, d18O) are unique tracers of many hydrological processes including evaporation, precipitation, reservoir mixing and residence time. Historically, discrete water samples have been collected and analyzed via either Isotope Ratio Mass Spectrometry, or more recently laser-based spectroscopic methods, such as Cavity Ring-Down Spectroscopy (CRDS). However, the analysis of discrete samples precludes the ability to construct high resolution water isotope data sets through time and space. By coupling a recently developed front-end peripheral device (Continuous Water Sampler or CWS) to a CRDS analyzer (Picarro L2130-i), we continuously measured and spatially mapped water isotopes on a transect of the Sacramento River Delta following an extended period of drought. More than two-thousand five-second average d18O and d2H measurements were made aboard the R/V King (USGS) over a six-hour period. In addition to water isotopes, nitrate, chlorophyll, dissolved organic matter (DOM) fluorescence, and other water quality parameters were also measured continuously. As you travel northeast up the delta, surface waters become progressively more enriched in 18O and 2H, while nitrate decreased in concentration and chlorophyll and DOM increased. We utilize the spatially-mapped isotope data within a single transect to understand local evaporation and residence time by (i) utilizing the secondary parameter, d-excess, and (ii) using a simple mass balance model of water moving through the system (inflow, outflow and evaporation). Additional transects, to be conducted during the rainy season, should highlight how the Delta system evolves seasonally. In concert with other data previously collected from the Sacramento River Delta, we suggest the lower region represents a mixture of river waters derived from the Sierra Nevada Mountains and the more marine waters from the mouth of the San Francisco Bay. Moving NE up the Delta into shallow sloughs through flooded wetlands, evaporative enrichment increases as shown by the increasing deviation of the real-time isotope data below the local mixing line constructed using discrete water samples from the Bay, Delta and river.
Lake Evaporation: a Model Study
Jumah Ahmad Amayreh
Reliable evaporation data are an essential requirement in any water and\\/or energy budget studies. This includes operation and management of both urban and agricultural water resources. Evaporation from large, open water surfaces such as lakes and reservoirs may influence many agricultural and irrigation decisions. In this study evaporation from Bear Lake in the states of Idaho and Utah was measured
Coupling of evaporative fluxes from drying porous surfaces with air boundary layer: Characteristics of evaporation from discrete pores
NASA Astrophysics Data System (ADS)
Shahraeeni, Ebrahim; Lehmann, Peter; Or, Dani
Prediction of drying rates from porous media remains a challenge due to complex interactions between ambient conditions and porous medium properties. Evaporation from a gradually drying porous surface across air boundary layer exhibits nonlinear behavior due to enhanced diffusive fluxes from increasingly isolated active pores. These nonlinear interactions were quantified by modeling evaporation from surfaces composed of individual pores considering surface water content dynamics and internal transport within the medium. Wind tunnel experiments show that in contrast with nearly constant evaporation rates obtained at low atmospheric demand (typically <5 mm/d), evaporation fluxes under high atmospheric demand (high air velocities) exhibit a continuous decrease with surface drying even in the absence of internal capillary flow limitations. The isolated pore evaporation model captures surface drying dynamics for a range of atmospheric demands associated with air velocity and boundary layer thickness. As a surface dries under low atmospheric demand (low air speed, thick boundary layer), the remaining active pores become gradually isolated with a conforming vapor concentration field becoming increasingly three-dimensional thereby enhancing evaporative flux per pore. Such enhancement may fully compensate for reduced evaporative surface area leading to observed constant evaporation rate under low demand. For high evaporative demand, limitations to vapor field configuration within thin boundary layer limit flux compensation efficiency and leads to decreasing evaporative flux with surface drying irrespective of internal supply capacity. The model provides new insights into the intrinsic links between surface properties and atmospheric conditions in determining a range of evaporative dynamics for similar surface wetness conditions.
A Study of Mechanisms and Supression of Evaporation of Water from Soils
Wendt, C. W.
Extensive greenhouse experiments were conducted to evaluate chemicals not previously studied extensively for their potential as evaporation suppressants. Included in the studies were crude oil, anionics, cationics, nonionics, silicones...
Hydrogen capacity and absorption rate of the SAES St707 non-evaporable getter at various temperatures.
Hsu, Irving; Mills, Bernice E.
A prototype of a tritium thermoelectric generator (TTG) is currently being developed at Sandia. In the TTG, a vacuum jacket reduces the amount of heat lost from the high temperature source via convection. However, outgassing presents challenges to maintaining a vacuum for many years. Getters are chemically active substances that scavenge residual gases in a vacuum system. In order to maintain the vacuum jacket at approximately 1.0 x 10{sup -4} torr for decades, nonevaporable getters that can operate from -55 C to 60 C are going to be used. This paper focuses on the hydrogen capacity and absorption rate of the St707{trademark} non-evaporable getter by SAES. Using a getter testing manifold, we have carried out experiments to test these characteristics of the getter over the temperature range of -77 C to 60 C. The results from this study can be used to size the getter appropriately.
Improved rate control for electron-beam evaporation and evaluation of optical performance improvements.
Gevelber, Michael; Xu, Bing; Smith, Douglas
A new deposition-rate-control and electron-beam-gun (e-gun) strategy was developed that significantly reduces the growth-rate variations for e-beam-deposited SiO2 coatings. The resulting improvements in optical performance are evaluated for multilayer bandpass filters. The adverse effect of uneven silica-source depletion on coating spectral performances during long deposition runs is discussed. PMID:16539249
Evaporation, Condensation, and Precipitation
NSDL National Science Digital Library
Miss Brown
After completion of this project students should have an understanding of evaporation, condensation, and precipitation in the water cycle. Use the websites provided to answer the questions. Record your answers on the spreadsheet provided. Do you understand how the water cycle works? Begin by watching this short video about the water cycle.water cycle video Use the website to define condensation, precipitation, and evaporation?water cycle List the different types of precipitation from the site.types of precipitation Follow the directions to the experiment on this website to get a better understanding of how evaporation takes ...
NASA Technical Reports Server (NTRS)
Shen, Hayley H.
Liquid fuel combustion process is greatly affected by the rate of droplet evaporation. The heat and mass exchanges between gas and liquid couple the dynamics of both phases in all aspects: mass, momentum, and energy. Correct prediction of the evaporation rate is therefore a key issue in engineering design of liquid combustion devices. Current analytical tools for characterizing the behavior of these devices are based on results from a single isolated droplet. Numerous experimental studies have challenged the applicability of these results in a dense spray. To account for the droplets' interaction in a dense spray, a number of theories have been developed in the past decade. Herein, two tasks are examined. One was to study how to implement the existing theoretical results, and the other was to explore the possibility of experimental verifications. The current theoretical results of group evaporation are given for a monodispersed cluster subject to adiabatic conditions. The time evolution of the fluid mechanic and thermodynamic behavior in this cluster is derived. The results given are not in the form of a subscale model for CFD codes.
Isotope Fractionation of Water during Evaporation without Condensation Christopher D. Cappa,,, Walter S. Drisdell,, Jared D. Smith,, Richard J. Saykally,, and
Cohen, Ronald C.
Isotope Fractionation of Water during Evaporation without Condensation Christopher D. Cappa incompletely understood. We present measurements of isotope fractionation occurring during free molecular differences from equilibrium vapor values, strong variations with the solution deuterium mole fraction
Evaporative Control on Soil Water Isotope Ratios: Implications for Atmosphere-Land Surface Water Fluxes and Interpretation of Terrestrial Proxy Records
NASA Astrophysics Data System (ADS)
Kaushik, A.; Noone, D. C.; Berkelhammer, M. B.; O'Neill, M.
The moisture balance of the continental boundary layer plays an important role in regulating the exchange of water and energy between the land surface and atmosphere. Near-surface moisture balance is controlled by a number of factors including precipitation, infiltration and evapotranspiration. Measurements of stable isotope ratios in water can be exploited to better understand the mechanisms controlling atmosphere-land surface water fluxes. Understanding the processes that set sub-surface water isotope ratios can prove useful for refining paleoclimate interpretations of stable oxygen and hydrogen isotope-based proxies. We present in situ tower-based measurements of stable isotope ratios of water (?D and ?18O) in vapor, precipitation and soil from the Boulder Atmospheric Observatory, a semi-arid tall-tower site in Erie, Colorado, from July 2012 to September 2014. Near surface profiles from 0 to 10 m were measured approximately every ninety minutes. Soil profiles from 0 to 30 cm, the region of maximum variability, were sampled on a weekly basis and cryogenically extracted for stable water isotope measurement. Evaporation-proof bulk rain collectors provided precipitation samples at this site. Results show disequilibrium exists between surface vapor and soil water isotopes, with the top 10 cm of soil water approaching equilibrium with the surface vapor right after a rain event because of high infiltration and saturation at the surface. At this semi-arid site with little vegetation, evaporative exchange is the main driver for soil water fluxes as the soil dries, corroborated by soil Dexcess profiles showing progressive enrichment through evaporation. In addition, when nighttime surface temperatures are cooler than deep soil, as is the case in many arid and semi-arid environments, upward vapor diffusion from the soil leads to dew formation at the surface which then contributes to surface vapor values. We use these observations to constrain a Craig-Gordon evaporation model at the land surface to weight the contributions of rainfall, surface water vapor exchange and sub-surface vapor diffusion to soil water isotope values. This has implications both for modeling short-term gas exchange at the land surface as well as for estimating past evaporative conditions from proxies like cave deposits and tree cellulose.
Vapor compression evaporator concentrates, recovers alcohol
Miller, M.N. (Monsanto, Seattle); Robe, K.; Bacchetti, J.A.
This article focuses on presenting a solution to the high energy cost of operating a steam heated, single effect evaporator used by Monsanto Industrial Chemical Company at a plant in Seattle, Wash., to produce vanillin from pulp and paper mill sulfite. Use of the single effect flash evaporator resulted in high energy usage due not only to the ''single effect'' use of steam, but also because energy consumption was reduced only slightly at low operating rates. The solution to this problem was the replacement of the single effect evaporator with a vapor recompression evaporator. Operating for over 1 1/2 years, the vapor recompression evaporator system has had no significant maintenance problems. The system operates with only 1/60th the steam consumption and 15% of the total energy consumption of the previous evaporator and has had no tube fouling. Also, since the distillate is condensed within the evaporator, less cooling water is required, allowing two heat exchangers to be taken out of service. When operating at less than design capacity, the energy consumption drops almost linearly with the feed rate. At low feed rates, a by-pass valve unloads the compressor to reduce energy consumption. Total energy consumption, now 15% of the previous level, results in an estimated pay-back of less than three years.
Infrared thermography of evaporative fluxes and dynamics of salt deposition on heterogeneous porous surfaces
NASA Astrophysics Data System (ADS)
Nachshon, Uri; Shahraeeni, Ebrahim; Or, Dani; Dragila, Maria; Weisbrod, Noam
Evaporation of saline solutions from porous media, common in arid areas, involves complex interactions between mass transport, energy exchange and phase transitions. We quantified evaporation of saline solutions from heterogeneous sand columns under constant hydraulic boundary conditions to focus on effects of salt precipitation on evaporation dynamics. Mass loss measurements and infrared thermography were used to quantify evaporation rates. The latter method enables quantification of spatial and temporal variability of salt precipitation to identify its dynamic effects on evaporation. Evaporation from columns filled with texturally-contrasting sand using different salt solutions revealed preferential salt precipitation within the fine textured domains. Salt precipitation reduced evaporation rates from the fine textured regions by nearly an order of magnitude. In contrast, low evaporation rates from coarse-textured regions (due to low capillary drive) exhibited less salt precipitation and consequently less evaporation rate suppression. Experiments provided insights into two new phenomena: (1) a distinct increase in evaporation rate at the onset of evaporation; and (2) a vapor pumping mechanism related to the presence of a salt crust over semidry media. Both phenomena are related to local vapor pressure gradients established between pore water and the surface salt crust. Comparison of two salts: NaCl and NaI, which tend to precipitate above the matrix surface and within matrix pores, respectively, shows a much stronger influence of NaCl on evaporation rate suppression. This disparity reflects the limited effect of NaI precipitation on matrix resistivity for solution and vapor flows.
Evaporation from flowing channels
Fulford, J.M.; Sturm, T.W.
Stability-dependent and Dalton-type mass transfer formulas are determined from experimental evaporation data in ambient and heated channels and are shown to have similar performance in prediction of evaporation. The formulas developed are compared with those proposed by other investigators for lakes and flowing channels. The evaporation data were obtained from a heat-budget analysis of two large outdoor channels, one of which received ambient-temperature water from an adjacent reservoir while the other received an artificially-heated discharge. Daily evaporation was calculated from bihourly values of water temperature and hourly values of meteorological variables for a 63-day study period in the summer. The evaporation data were then used to derive mass transfer evaporation formulas for heated and ambient flowing channels.
The impact of humidity on evaporative cooling in small desert birds exposed to high air temperatures.
Gerson, Alexander R; Smith, Eric Krabbe; Smit, Ben; McKechnie, Andrew E; Wolf, Blair O
Environmental temperatures that exceed body temperature (Tb) force endothermic animals to rely solely on evaporative cooling to dissipate heat. However, evaporative heat dissipation can be drastically reduced by environmental humidity, imposing a thermoregulatory challenge. The goal of this study was to investigate the effects of humidity on the thermoregulation of desert birds and to compare the sensitivity of cutaneous and respiratory evaporation to reduced vapor density gradients. Rates of evaporative water loss, metabolic rate, and Tb were measured in birds exposed to humidities ranging from ?2 to 30 g H2O m(-3) (0%-100% relative humidity at 30░C) at air temperatures between 44░ and 56░C. In sociable weavers, a species that dissipates heat primarily through panting, rates of evaporative water loss were inhibited by as much as 36% by high humidity at 48░C, and these birds showed a high degree of hyperthermia. At lower temperatures (40░-44░C), evaporative water loss was largely unaffected by humidity in this species. In Namaqua doves, which primarily use cutaneous evaporation, increasing humidity reduced rates of evaporative water loss, but overall rates of water loss were lower than those observed in sociable weavers. Our data suggest that cutaneous evaporation is more efficient than panting, requiring less water to maintain Tb at a given temperature, but panting appears less sensitive to humidity over the air temperature range investigated here. PMID:25461643
Determination of Summertime VOC Emission Rates from Produced Water Ponds in the Uintah Basin
NASA Astrophysics Data System (ADS)
Martin, R. S.; Woods, C.; Lyman, S.
The observance of excess ozone concentrations in Utah's Uintah Basin over past several years has prompted several investigations into the extent and causes of the elevated ozone. Among these is the assessment of potential emissions of reactive VOCs. Evaporation ponds, used a remediation technique for treatment of contaminated production and other waters, are one potential source of significant VOC emissions and is estimated that there are around 160 such ponds within the Uintah Basin's oil and gas production areas. In June 2012 VOC emission rates for several reactive VOCs were derived for an evaporation facility consisting of a small inlet pond (?0.03 acres) and two larger, serial ponds (?4.3 acres each). The emission rates were determined over three sampling periods using an inverse modeling approach. Under this methodology, ambient VOC concentrations are determined at several downwind locations through whole-air collection into SUMMA canisters, followed by GC/MS quantification and compared with predicted concentrations using an EPA-approved dispersion model, AERMOD. The presumed emission rates used within the model were then adjusted until the modeled concentrations approach the observed concentrations. The derived emission rates for the individual VOCs were on the order of 10-3 g/s/m2 from the inlet pond and 10-6 g/s/m2 from the larger ponds. The emissions from the 1st pond in series after the inlet pond were about 3-4x the emissions from the 2nd pond. These combined emission rates are about an order of magnitude those reported for a single study in Colorado (Thoma, 2009). It should be noted, however, that the variability about each of the VOC emission rates was significant (often ū100% at the 95% confidence interval). Extrapolating these emission rates to the estimated total areas of all the evaporation ponds within Basin resulted in calculated Basin-wide VOC emissions 292,835 tons/yr. However, Bar-Ilan et al. (2009) estimated 2012 VOC oil and gas related emissions within the Uintah Basin to be 119,974 tons/yr. Given the large observed variabilities and the uncertainties with extrapolating the derived emission rates across varying pond types and differing climatic conditions, the comparisons are not unreasonable. If the lower, literature emission rates of Thoma (2009) are used the estimated Basin-wide evaporation emissions, the pond emissions would still be approximately 30% of the total emissions compiled by Bar-Ilan et al. (2009). Although the study described herein only represents a single facility and a single set of seasonal conditions, extrapolating these rates can give potential insight into the significance of VOC emissions into the Basin atmosphere from evaporation ponds.
Soil water content and evaporation determined by thermal parameters obtained from ground-based and remote measurements
NASA Technical Reports Server (NTRS)
Reginato, R. J.; Idso, S. B.; Jackson, R. D.; Vedder, J. F.; Blanchard, M. B.; Goettelman, R.
Soil water contents from both smooth and rough bare soil were estimated from remotely sensed surface soil and air temperatures. An inverse relationship between two thermal parameters and gravimetric soil water content was found for Avondale loam when its water content was between air-dry and field capacity. These parameters, daily maximum minus minimum surface soil temperature and daily maximum soil minus air temperature, appear to describe the relationship reasonably well. These two parameters also describe relative soil water evaporation (actual/potential). Surface soil temperatures showed good agreement among three measurement techniques: in situ thermocouples, a ground-based infrared radiation thermometer, and the thermal infrared band of an airborne multispectral scanner.
Evaporative Cooling Membrane Device
NASA Technical Reports Server (NTRS)
Lomax, Curtis (Inventor); Moskito, John (Inventor)
An evaporative cooling membrane device is disclosed having a flat or pleated plate housing with an enclosed bottom and an exposed top that is covered with at least one sheet of hydrophobic porous material having a thin thickness so as to serve as a membrane. The hydrophobic porous material has pores with predetermined dimensions so as to resist any fluid in its liquid state from passing therethrough but to allow passage of the fluid in its vapor state, thereby, causing the evaporation of the fluid and the cooling of the remaining fluid. The fluid has a predetermined flow rate. The evaporative cooling membrane device has a channel which is sized in cooperation with the predetermined flow rate of the fluid so as to produce laminar flow therein. The evaporative cooling membrane device provides for the convenient control of the evaporation rates of the circulating fluid by adjusting the flow rates of the laminar flowing fluid.
Salt stains from evaporating droplets
Shahidzadeh, Noushine; Schut, Marthe F. L.; Desarnaud, Julie; Prat, Marc; Bonn, Daniel
The study of the behavior of sessile droplets on solid substrates is not only associated with common everyday phenomena, such as the coffee stain effect, limescale deposits on our bathroom walls , but also very important in many applications such as purification of pharmaceuticals, de-icing of airplanes, inkjet printing and coating applications. In many of these processes, a phase change happens within the drop because of solvent evaporation, temperature changes or chemical reactions, which consequently lead to liquid to solid transitions in the droplets. Here we show that crystallization patterns of evaporating of water drops containing dissolved salts are different from the stains reported for evaporating colloidal suspensions. This happens because during the solvent evaporation, the salts crystallize and grow during the drying. Our results show that the patterns of the resulting salt crystal stains are mainly governed by wetting properties of the emerging crystal as well as the pathway of nucleation and growth, and are independent of the evaporation rate and thermal conductivity of the substrates. PMID:26012481
Salt stains from evaporating droplets.
Shahidzadeh, Noushine; Schut, Marthe F L; Desarnaud, Julie; Prat, Marc; Bonn, Daniel
The study of the behavior of sessile droplets on solid substrates is not only associated with common everyday phenomena, such as the coffee stain effect, limescale deposits on our bathroom walls , but also very important in many applications such as purification of pharmaceuticals, de-icing of airplanes, inkjet printing and coating applications. In many of these processes, a phase change happens within the drop because of solvent evaporation, temperature changes or chemical reactions, which consequently lead to liquid to solid transitions in the droplets. Here we show that crystallization patterns of evaporating of water drops containing dissolved salts are different from the stains reported for evaporating colloidal suspensions. This happens because during the solvent evaporation, the salts crystallize and grow during the drying. Our results show that the patterns of the resulting salt crystal stains are mainly governed by wetting properties of the emerging crystal as well as the pathway of nucleation and growth, and are independent of the evaporation rate and thermal conductivity of the substrates. PMID:26012481
Vakil, Himanshu B. (Schenectady, NY); Kosky, Philip G. (Ballston Lake, NY)
In the preparation of the gaseous reactant feed to undergo a chemical reaction requiring the presence of steam, the efficiency of overall power utilization is improved by premixing the gaseous reactant feed with water and then heating to evaporate the water in the presence of the gaseous reactant feed, the heating fluid utilized being at a temperature below the boiling point of water at the pressure in the volume where the evaporation occurs.
Laboratory prototype flash evaporator
NASA Technical Reports Server (NTRS)
Gaddis, J. L.
A laboratory prototype flash evaporator that is being developed as a candidate for the space shuttle environmental control system expendable heat sink is described. The single evaporator configuration uses water as an evaporant to accommodate reentry and on-orbit peak heat loads, and Freon 22 for terrestrial flight phases below 120,000 feet altitude. The design features, fabrication techniques used for the prototype unit, redundancy considerations, and the fluid temperature control arrangement are reported in detail. The results of an extensive test program to determine the evaporator operational characteristics under a wide variety of conditions are presented.
A simple breathing rate-sensing method exploiting a temporarily condensed water layer formed on an oxidized surface
NASA Astrophysics Data System (ADS)
Seo, Min-Ho; Yang, Hyun-Ho; Choi, Kwang-Wook; Lee, Jae-Shin; Yoon, Jun-Bo
We describe a very simple breathing rate-sensing method that detects a significant electric current change between two metal electrodes on an oxidized surface. The current change is caused by the formation of a water layer from exhaled breath. We discovered that breathing onto the oxidized surface causes instant water condensation, and it generates 20 times increased current than that measured in the inhalation period. The condensed water quickly evaporates, enabling us to detect dynamic human breathing in real time. We also investigated the breathing rate sensor by varying the relative humidity, temperature, and breathing frequency and confirmed its potential for practical applications.
New explicit equations for the accurate calculation of the growth and evaporation of hydrometeors by the diffusion of water vapor
NASA Technical Reports Server (NTRS)
Srivastava, R. C.; Coen, J. L.
The traditional explicit growth equation has been widely used to calculate the growth and evaporation of hydrometeors by the diffusion of water vapor. This paper reexamines the assumptions underlying the traditional equation and shows that large errors (10-30 percent in some cases) result if it is used carelessly. More accurate explicit equations are derived by approximating the saturation vapor-density difference as a quadratic rather than a linear function of the temperature difference between the particle and ambient air. These new equations, which reduce the error to less than a few percent, merit inclusion in a broad range of atmospheric models.
Statistical rate theory determination of water properties below the triple point.
Duan, Fei; Thompson, Ian; Ward, C A
We report a new method for determining the saturation vapor pressure, Ps(T), of water at conditions below its triple point. Ps(T) appears as a parameter in the statistical rate theory (SRT) expression for the net evaporation flux. We use measurements of the interfacial conditions during steady-state evaporation and condensation experiments and SRT to determine the values of Ps(T) from 50 different experiments over a range of interfacial conditions. From these values of Ps(T), we develop an analytical expression and from it calculate the liquid-vapor latent heat, Llv(T), and the constant pressure specific heat, cp(L)(T). The calculated values of these properties are compared with those obtained from independent measurements. This comparison indicates the SRT expressions for Llv(T) and cp(L)(T) are consistent with the measurements over a range of temperatures. PMID:18582005
Evaporation, transpiration, and ecosystem water use efficiency in a multi-annual sugarcane production system in Hawai'i, USA
NASA Astrophysics Data System (ADS)
Anderson, R. G.; Tirado-corbala, R.; Wang, D.; Ayars, J. E.
Food and biofuel production will require practices that increase water use efficiency in order to have future sustainability in a water-constrained environment. One possible practice is the use of food and energy crops with multi-annual growing periods, which could reduce bare soil evaporation. We integrated field water budgets, micrometeorology, and plant sampling to observe plant growth and evapotranspiration (ET) in two sugarcane (Saccharum officinarum L.) fields in Hawai'i, USA in contrasting environments with unusually long (18-24 month) growing periods. We partitioned observed ET into evaporation and transpiration using a flux partitioning model and calculated ecosystem water use efficiency (EWUE=Net Ecosystem Productivity/ET) and harvest WUE (HWUE=Aboveground Net Ecosystem Productivity/ET) to assess sugarcane water use efficiency. After the start of the mid-period, our higher elevation, less windy field ('Lee') had a slightly higher mean EWUE (31.5 kg C ha-1 mm-1) than our lower elevation, windier ('Windy') field (mean EWUE of 30.7 kg C ha-1 mm-1). HWUE was also very high (HWUE >27 kg C ha-1 mm-1) in both fields due to aboveground biomass composing >87% of total biomass. Transpiration, as a fraction of total ET, increased rapidly with canopy cover in both fields; during the mid-period, transpiration was an average of 84% of total ET in Windy and 80% in Lee, with Lee showing greater variation than Windy. As expected, daily EWUE increased with canopy cover during the initial growing stages; more significantly, EWUE showed no substantial decrease during the 2nd year with an aging crop. The results illustrate the potential for longer-rotation crop cycles for increasing water use efficiency, particularly in tropical regions.
Cooling enhancement in an air-cooled finned heat exchanger by thin water film evaporation
Chan Ho Song; Dae-Young Lee; Sung Tack Ro
A theoretical analysis on the cooling enhancement by applying evaporative cooling to an air-cooled finned heat exchanger is presented in this work. A two-dimensional model on the heat and mass transfer in a finned channel is developed adopting a porous medium approach. Based on this model, the characteristics of the heat and mass transfer are investigated in a plate-fin heat
A new method using evaporation for high-resolution measurements of soil thermal conductivity at changing water contents
NASA Astrophysics Data System (ADS)
Markert, A.; Trinks, S.; Facklam, M.; Wessolek, G.
The thermal conductivity of soils is a key parameter to know if their use as heat source or sink is planned. It is required to calculate the efficiency of ground-source heat pump systems in combination with soil heat exchangers. Apart from geothermal energy, soil thermal conductivity is essential to estimate the ampacity for buried power cables. The effective thermal conductivity of saturated and unsaturated soils, as a function of water transport, water vapour transport and heat conduction, mainly depends on the soil water content, its bulk density and texture. The major objectives of this study are (i) to describe the thermal conductivity of soil samples with a non-steady state measurement at changing water contents and for different bulk densities. Based on that it is (ii) tested if available soil thermal conductivity models are able to describe the measured data for the whole range of water contents. The new method allows a continuous measurement of thermal conductivity for soil from full water saturation to air-dryness. Thermal conductivity is measured with a thermal needle probe in predefined time intervals while the change of water content is controlled by evaporation. To relate the measured thermal conductivity to the current volumetric water content, the decrease in weight of the sample, due to evaporation, is logged with a lab scale. Soil texture of the 11 soil substrates tested in this study range between coarse sand and silty clay. To evaluate the impact of the bulk density on heat transport processes, thermal conductivity at 20░C was measured at 1.5g/cm3; 1.7g/cm3 and 1.9g/cm3 for each soil substrate. The results correspond well to literature values used to describe heat transport in soils. Due to the high-resolution and non-destructive measurements, the specific effects of the soil texture and bulk density on thermal conductivity could be proved. Decreasing water contents resulted in a non-linear decline of the thermal conductivity for all samples. Especially for coarse textured soils a rapid decrease of the thermal conductivity was observed, when the volumetric water content drops under a critical level. Higher bulk densities increased the heat transport parameters for soil samples with the same texture. This effect becomes significant at high water saturations. The method used in this study allows easy to use non-steady state measurements of the soil thermal conductivity with a high data resolution and for continuously decreasing water contents. In further studies these measured data will be used to enhance existing pedotransfer functions and models and improve the prediction of soil thermal properties for application-oriented requirements.
Involvement of root ABA and hydraulic conductivity in the control of water relations in wheat plants exposed to increased evaporative demand.
Kudoyarova, Guzel; Veselova, Svetlana; Hartung, Wolfram; Farhutdinov, Rashit; Veselov, Dmitry; Sharipova, Guzyal
We studied the possible involvement of ABA in the control of water relations under conditions of increased evaporative demand. Warming the air by 3░C increased stomatal conductance and raised transpiration rates of hydroponically grown Triticum durum plants while bringing about a temporary loss of relative water content (RWC) and immediate cessation of leaf extension. However, both RWC and extension growth recovered within 30Āmin although transpiration remained high. The restoration of leaf hydration and growth were enabled by increased root hydraulic conductivity after increasing the air temperature. The use of mercuric chloride (an inhibitor of water channels) to interfere with the rise on root hydraulic conductivity hindered the restoration of extension growth. Air warming increased ABA content in roots and decreased it in shoots. We propose this redistribution of ABA in favour of the roots which increased the root hydraulic conductivity sufficiently to permit rapid recovery of shoot hydration and leaf elongation rates without the involvement of stomatal closure. This proposal is based on known ability of ABA to increase hydraulic conductivity confirmed in these experiments by measuring the effect of exogenous ABA on osmotically driven flow of xylem sap from the roots. Accumulation of root ABA was mainly the outcome of increased export from the shoots. When phloem transport in air-warmed plants was inhibited by cooling the shoot base this prevented ABA enrichment of the roots and favoured an accumulation of ABA in the shoot. As a consequence, stomata closed. PMID:20924765
Estimation of Water Turnover Rate in Captive Dugongs ( Dugong dugon)
Janet M. Lanyon; Keith Newgrain; Teuku Sahir Syah Alli
Water turnover rate was measured for two cap- tive dugongs (Dugong dugon) using deuterated water. Body water content of 69.5% in a dugong was high compared to other marine mammals. A water turnover of 257.2 ml kg -1 day -1 measured in one dugong was almost twice as high as the highest rates measured in studies of captive West Indian
(10:1, 55 nm) and was deposited by the co-evaporation of magnesium and silver metals, with deposition rates of 5 and 0.5 s1
Wang, Zhong L.
of 3 s▒1 . The effective area of the emitting diode was 9.00 mm2 . Current, voltage, and light evaporating LiF (0.5 nm) at a deposition rate of 0.1 s▒1 and then evaporating aluminum (400 nm) at a rate
Seasonal and intraseasonal variations in evaporation and surface energy budget from eddy covariance measurements over an open water surface in Mississippi, U.S.A
H. Liu; Y. Zhang; Q. L. Williams; H. Jiang; L. Sheng
Understanding seasonal and intraseasonal variations in evaporation over lake\\/reservoir is important for water resource management as well as predicting variations in hydrology as a result of climate change. Since August of 2007, we have conducted a long-term eddy covariance measurement of evaporation and the surface energy budget over Ross Barnett Reservoir (32o26'N, 90o02'W) in Mississippi, USA. The fetch for eddy
Experimental investigations of water fluxes within the soil-vegetation-atmosphere system: Stable isotope mass-balance approach to partition evaporation and transpiration
NASA Astrophysics Data System (ADS)
Wenninger, Jochen; Beza, Desta Tadesse; Uhlenbrook, Stefan
Irrigated agriculture is the largest user of freshwater worldwide and the scale of irrigated agriculture can be so large that it can have dramatic effects on the water cycle and even alter regional climates. Therefore, it is vital to improve the water use efficiency of irrigated lands in order to address the sustainable use of water resources, the growing need for agricultural products, and the health of ecosystems. Environmental isotopes have unique attributes that make them particularly suitable for tracing hydrological pathways and quantifying hydrological fluxes within the soil-vegetation-atmosphere system. The stable isotopic composition of soil water is mainly controlled by precipitation or irrigation inputs and evaporative losses. Because transpiration does not fractionate soil water isotopes, it is possible to estimate the relative proportions of evaporation and transpiration using isotopic mass balance calculations. In this study experimental investigations, combining classical hydrometric measurements, tracer hydrological methods and a soil water model were applied to laboratory lysimeters to study the transpiration processes of Teff ( Eragrostis tea (Zucc.) Trotter). Teff is an annual bunch cereal and an important aliment in Ethiopia and Eritrea and it is also gaining popularity in other countries. To determine the soil water contents, sensors using a capacitance/frequency domain technology were installed at different depths and soil water samples for the isotope analysis were taken using pore water samplers. Water contents in different depths and water fluxes, such as percolation and evaporation were modeled using the HYDRUS-1D software package. By using an isotope mass balance model the total evaporation and the fractions between soil evaporation and transpiration could be determined. The water losses which were estimated using the isotope mass-balance approach are in good agreement with the measured values using classical hydrometric measurements. The proportion of water lost by transpiration (T/ET) during the study period was about 0.7 for the Teff covered laboratory set-up.
Atmospheric impacts of evaporative cooling systems
The report summarizes available information on the effects of various power plant cooling systems on the atmosphere. While evaporative cooling systems sharply reduce the biological impacts of thermal discharges in water bodies, they create (at least, for heat-release rates comparable to those of two-unit nuclear generating stations) atmospheric changes. For an isolated site such as required for a nuclear power
Evaporation and canopy characteristics of coniferous forests and grasslands
F. M. Kelliher; R. Leuning; E. D. Schulze
Canopy-scale evaporation rate (E) and derived surface and aerodynamic conductances for the transfer of water vapour (gs and ga, respectively) are reviewed for coniferous forests and grasslands. Despite the extremes of canopy structure, the two vegetation types have similar maximum hourly evaporation rates (Emax) and maximum surface conductances (gsmax) (medians = 0.46 mm h-1 and 22 mm s-1). However, on
Gaseous mercury exchange rate between air and water over Baihua reservir, Guizhou, China during cold season
NASA Astrophysics Data System (ADS)
Feng, X.; Shang, L.; Tang, S.; Yan, H.; Liu, C.
Field measurement campaigns over lake water surface at Baihua reservoir in Guiyang, Southwestern China were conducted to measure mercury flux using a dynamic flux chamber technique coupled with automatic mercury vapor-phase analyzer from October 30 to November 4, 2001. The dynamic flux chamber is made of quartz glass, and has low blanks. Water samples were collected, and dissolved gaseous mercury (DGM), reactive and total mercury concentrations in water were measured using gold trap pre-concentration and AFS detection method. Meanwhile meteorological parameters, such as wind speed, wind direction, intensity of solar radiation, air and water temperature, and relative humidity were monitored using a portable weather station. Water surface is a net atmospheric mercury emission source even at cold season (autumn), and the average mercury emission rate is 3.0 ng m^{-2} h^{-1}. We observed a strong correlation between wind speed and mercury emission rate, suggesting that strong wind facilitate mercury evaporation process from the water system during cold season. No significant correlations between Hg emission rate and solar radiation, water and air temperature were obtained.
KITANO M. and EGUCHI H. Dynamics of whole plant water balance and leaf growth in response to evaporative demand. II. Effect of change in wind velocity. BIOTRONICS 21, 51-60, 1992. Dynamics of whole plant water balance and leaf expansive growth were analyzed in cucumber plants (Cucumis sativus L.) exposed to step change in wind velocity (U). The effect of step
Long-term and high frequency non-destructive monitoring of water stable isotope profiles in an evaporating soil column
NASA Astrophysics Data System (ADS)
Rothfuss, Y.; Merz, S.; Vanderborght, J.; Hermes, N.; Weuthen, A.; Pohlmeier, A.; Vereecken, H.; Br³ggemann, N.
The stable isotope compositions of soil water (?2H and ?18O) carry important information about the prevailing soil hydrological conditions and for constraining ecosystem water budgets. However, they are highly dynamic, especially during and after precipitation events. The classical method of determining soil water ?2H and ?18O at different depths, i.e., soil sampling and cryogenic extraction of the soil water, followed by isotope-ratio mass spectrometer analysis is destructive and laborious with limited temporal resolution. In this study, we present a new non-destructive method based on gas-permeable tubing and isotope-specific infrared laser absorption spectroscopy. We conducted a laboratory experiment with an acrylic glass column filled with medium sand equipped with gas-permeable tubing at eight different soil depths. The soil column was initially saturated from the bottom, exposed to evaporation for a period of 290 days, and finally rewatered. Soil water vapor ?2H and ?18O were measured daily, sequentially for each depth. Soil liquid water ?2H and ?18O were inferred from the isotopic values of the vapor assuming thermodynamic equilibrium between liquid and vapor phases in the soil. The experimental setup allowed following the evolution of typical exponential-shaped soil water ?2H and ?18O profiles with unprecedentedly high temporal resolution. As the soil dried out, we could also show for the first time the increasing influence of the isotopically depleted ambient water vapor on the isotopically enriched liquid water close to the soil surface (i.e., atmospheric invasion). Rewatering at the end of the experiment led to instantaneous resetting of the stable isotope profiles, which could be closely followed with the new method.
Modelling of lake mixing induced by air-bubble plumes and the effects on evaporation
NASA Astrophysics Data System (ADS)
Helfer, Fernanda; Zhang, Hong; Lemckert, Charles
SummaryOne of the main concerns regarding water storage in Australia, and other semi-arid countries, is the high rate of evaporation that inevitably leads to significant water loss. In this paper, the use of air-bubble plume systems to reduce evaporation from large reservoirs is assessed. A destratification system was designed for a large dam based on its depth and stratification strength with the intention of destratifying the reservoir in a short time period. The model DYRESM was then used to simulate the water dynamics under destratification conditions. Different strategies for the operation of the aeration system were assessed, from 10-days operation periods at times of high evaporation rates to continuous operation over longer time spans. The modelled water column temperatures and evaporation rates were analysed and it was found that artificial destratification was only effective in reducing evaporation in spring. In summer, heat is added to the water at a rapid rate, and artificial destratification only helps reduce evaporation in the initial days of operation. The effect of artificial destratification in reducing evaporation in autumn depends on the operation of the system during summer. If operated in summer, the rates of evaporation in autumn will increase due to the additional heat added to the water during the summer. In winter, overturn takes place and artificial destratification has no influence on water temperatures and evaporation. It was concluded that aeration by air-bubble plumes would only be effective in reducing evaporation if the hypolimnetic water does not become warm when mixing takes place. This is an ideal situation, but is unlikely to happen in practice.
Efficiency of methods for Karl Fischer determination of water in oils based on oven evaporation and azeotropic distillation.
Larsson, William; Jalbert, Jocelyn; Gilbert, Roland; Cedergren, Anders
The efficiency of azeotropic distillation and oven evaporation techniques for trace determination of water in oils has recently been questioned by the National Institute of Standards and Technology (NIST), on the basis of measurements of the residual water found after the extraction step. The results were obtained by volumetric Karl Fischer (KF) titration in a medium containing a large excess of chloroform (> or = 65%), a proposed prerequisite to ensure complete release of water from the oil matrix. In this work, the extent of this residual water was studied by means of a direct zero-current potentiometric technique using a KF medium containing more than 80% chloroform, which is well above the concentration recommended by NIST. A procedure is described that makes it possible to correct the results for dilution errors as well as for chemical interference effects caused by the oil matrix. The corrected values were found to be in the range of 0.6-1.5 ppm, which should be compared with the 12-34 ppm (uncorrected values) reported by NIST for the same oils. From this, it is concluded that the volumetric KF method used by NIST gives results that are much too high. PMID:12659179
Pull, Push and Evaporate: The Role of Surfaces in Plant Water Transport
Anita Roth-Nebelsick
Water is of fundamental significance for plant life. One fundamental aspect is that water represents an important environmental\\u000a factor. Rain, fog and mist affect irradiation absorbed by a plant and the environmental temperature. Water is therefore a\\u000a climate-related parameter. It also acts as a factor which influences the immediate surroundings of a plant. For example, plants\\u000a which live in swamp
Simultaneous evaporation and advanced oxidation processes (AOP) for process water treatment
R. W. Tock; M. A. Rege; S. H. Bhojani
The commercial oxidation of hydrocarbons to produce oxygenated organics also generates byproduct water. This water ultimately appears as a waste distillation [open quotes]tower bottoms[close quotes] containing residual amounts of the oxygenated organics. Because such wastewater streams can be sizeable (> 8,000 gal\\/hr) and have little mineral content, they have been considered for recycle use as cooling tower water or boiler
Intensification of evaporation processes using surfactants
NASA Astrophysics Data System (ADS)
Sharifullin, V. N.; Sharifullin, A. V.
The effect of a group of low molecular surfactants on the evaporation rate during nucleate boiling of water is investigated. It is found that the vaporization rate and heat flux from the heater increase by 4-8% in an electric boiler with surfactants. The analysis of the process based on the model of the phase contact surface restoration made it possible to formulate the mechanism of the effect of considered surfactants.
Estimates of Evaporation From Terrestrial Surface Water Bodies Using the Global Lakes and Wetlands Database
V. Ortiz; G. Goteti; J. Famiglietti
Land surface modeling has led to significant advances in the understanding the role of the terrestrial hydrologic cycle in the Earth system. However, the representation of land surface of in these modeling approaches suffers from drawbacks such as lack of representation of terrestrial surface water bodies. These water bodies play an important role in the hydrological and biogeochemical cycles and
Evaluation of a two-stage evaporation approximation for contrasting vegetation cover
G. Boulet; A. Chehbouni; I. Braud; B. Duchemin; A. Lakhal
For a regional assessment of water needs and consumption in semiarid agricultural zones, one needs robust and simple tools that provide space-time estimates of evaporation losses. Most operational evaporation estimates rely on semiempirical relationships that are not generally applicable. Several authors have proposed physically based simple expressions to model the ōenergy-limitedö (stage-one) and the ōsupply-limitedö (stage-two) evaporation rates during a
Evaluation of a two-stage evaporation approximation for contrasting vegetation cover
G. Boulet; A. Chehbouni; I. Braud; B. Duchemin; A. Lakhal
For a regional assessment of water needs and consumption in semiarid agricultural zones, one needs robust and simple tools that provide space-time estimates of evaporation losses. Most operational evaporation estimates rely on semiempirical relationships that are not generally applicable. Several authors have proposed physically based simple expressions to model the ``energy-limited'' (stage-one) and the ``supply-limited'' (stage-two) evaporation rates during a
Representative shuttle evaporative heat sink
NASA Technical Reports Server (NTRS)
Hixon, C. W.
The design, fabrication, and testing of a representative shuttle evaporative heat sink (RSEHS) system which vaporizes an expendable fluid to provide cooling for the shuttle heat transport fluid loop is reported. The optimized RSEHS minimum weight design meets or exceeds the shuttle flash evaporator system requirements. A cold trap which cryo-pumps flash evaporator exhaust water from the CSD vacuum chamber test facility to prevent water contamination of the chamber pumping equipment is also described.
Evaporation-induced cavitation in nanofluidic channels
Duan, Chuanhua; Karnik, Rohit; Lu, Ming-Chang; Majumdar, Arun
Cavitation, known as the formation of vapor bubbles when liquids are under tension, is of great interest both in condensed matter science as well as in diverse applications such as botany, hydraulic engineering, and medicine. Although widely studied in bulk and microscale-confined liquids, cavitation in the nanoscale is generally believed to be energetically unfavorable and has never been experimentally demonstrated. Here we report evaporation-induced cavitation in water-filled hydrophilic nanochannels under enormous negative pressures up to -7ĀMPa. As opposed to receding menisci observed in microchannel evaporation, the menisci in nanochannels are pinned at the entrance while vapor bubbles form and expand inside. Evaporation in the channels is found to be aided by advective liquid transport, which leads to an evaporation rate that is an order of magnitude higher than that governed by Fickian vapor diffusion in macro- and microscale evaporation. The vapor bubbles also exhibit unusual motion as well as translational stability and symmetry, which occur because of a balance between two competing mass fluxes driven by thermocapillarity and evaporation. Our studies expand our understanding of cavitation and provide new insights for phase-change phenomena at the nanoscale. PMID:22343530
Solvated Ion Evaporation from Charged Water Nanodroplets Vasiliy Znamenskiy, Ioan Marginean, and Akos Vertes*
Vertes, Akos
functions for water and corresponding neutron diffraction data. The self- diffusion coefficients that electrified liquid interfaces under certain condi- tions assume a well-defined conical geometry.7 More
Physiological evaluation of the resistance to evaporative heat transfer by clothing
A new method has been developed to determine the æeffectiveÆ evaporative resistance of clothing in vivo. It is based on direct measurements of the water vapour pressure gradient between skin and ambient air and of the steady state rate of evaporative heat loss. Air is sampled by a system of tubes terminating at six different loci on the skin surface
Wind effects on leaf transpiration challenge the concept of "potential evaporation"
NASA Astrophysics Data System (ADS)
Schymanski, S. J.; Or, D.
Transpiration is commonly conceptualised as a fraction of some potential rate, driven by so-called "atmospheric evaporative demand". Therefore, atmospheric evaporative demand or "potential evaporation" is generally used alongside with precipitation and soil moisture to characterise the environmental conditions that affect plant water use. Consequently, an increase in potential evaporation (e.g. due to climate change) is believed to cause increased transpiration and/or vegetation water stress. In the present study, we investigated the question whether potential evaporation constitutes a meaningful reference for transpiration and compared sensitivity of potential evaporation and leaf transpiration to atmospheric forcing. A physically-based leaf energy balance model was used, considering the dependence of feedbacks between leaf temperature and exchange rates of radiative, sensible and latent heat on stomatal resistance. Based on modelling results and supporting experimental evidence, we conclude that stomatal resistance cannot be parameterised as a factor relating transpiration to potential evaporation, as the ratio between transpiration and potential evaporation not only varies with stomatal resistance, but also with wind speed, air temperature, irradiance and relative humidity. Furthermore, the effect of wind speed in particular implies increase in potential evaporation, which is commonly interpreted as increased "water stress", but at the same time can reduce leaf transpiration, implying a decrease in water demand at leaf scale.
Water budgets of Italian and Dutch gravel pit lakes: a study using a fen as a natural evaporation pan, stable isotopes and conservative tracer modeling.
NASA Astrophysics Data System (ADS)
Nella Mollema, Pauline; Antonellini, Marco
Gravel pits are excavated in aquifers to fulfill the need for construction materials. Flow-through lakes form where the gravel pits are below the water table and fill with groundwater. Their presence changes the drainage patterns, water- and hydrochemical budgets of a watershed. We have studied the water budget of two gravel pit lakes systems using stable H and O isotopes of water as well as conservative tracer (Cl) modeling. The Dutch gravel pit lakes are a fluvial fresh water system of 70 lakes along the Meuse River and the Italian gravel pit lakes are a brackish system along the Adriatic coast. Surface water evaporation from the gravel pit lakes is larger than the actual evapotranspiration of the grass land and forests that were replaced. The ratio of evaporation to total flow into the Dutch lakes was determined by using a Fen as a natural evaporation pan: the isotope content of the Tuspeel Fen, filled with rain water and sampled in a dry and warm summer period (August 2012), is representative for the limiting isotopic enrichment under local hydro meteorological conditions. The Local Evaporation line (LEL) was determined ?2 H = 4.20 ? 18O - 14.10 (R▓ = 0.99) and the ratio of total inflow to evaporation for three gravel pit lakes were calculated to be 22.6 for the De Lange Vlieter lake used for drinking water production, 11.3 for the Boschmolen Lake and 8.9 for the Anna's Beemd lake showing that groundwater flow is much larger than evaporation. The Italian gravel pit lakes are characterized by high salinity (TDS = 4.6-12.3 g L-1). Stable isotope data show that these latter gravel pit lakes are fed by groundwater, which is a mix between fresh Apennine River water and brackish (Holocene) Adriatic Sea water. The local evaporation line is determined: ?2H = 5.02 ?18O - 10.49. The ratio of total inflow to evaporation is 5. Conservative tracer modeling indicates that the chloride concentration in the Italian gravel pit lakes stabilizes after a short period of rapid increase, because water leaving the lake via groundwater flow, driven by the drainage system, removes part of the Cl that accumulates in the lake due to evapo-concentration. Under climate change, rising sea levels and continuing land subsidence as well as increasing precipitation would increase the need for drainage which would enhance groundwater flow through the lake. The resulting steady-state Cl concentration of the lakes could become less than the current Cl concentration. This effect would be larger than increasing evapo- concentration. Both gravel pit lake systems have a large flux of groundwater into and out of the lakes driven by evaporation and (artificial) drainage with important consequences for the water- and hydrochemical budgets of the whole watershed and in particular on freshwater quantity and groundwater salinity.
Determining the virtual surface in the thermal evaporation process of magnesium fluoride from a tungsten boat for different deposition rates, to be used in precision optical components
NASA Astrophysics Data System (ADS)
Tejada Esteves, A.; Gßlvez de la Puente, G.
Vacuum thermal evaporation has, for some time now, been the principal method for the deposition of thin films, given, among other aspects, its simplicity, flexibility, and relatively low cost. Therefore, the development of models attempting to predict the deposition patterns of given thin film materials in different locations of a vacuum evaporation chamber are arguably important. With this in mind, we have designed one of such models for the thermal evaporation process of magnesium fluoride (MgF2), a common material used in optical thin films, originating from a tungsten boat source. For this we took several deposition samples in glass slide substrates at different locations in the vacuum chamber, considering as independent variables the mean deposition rate, and the axial and vertical distances of the source to the substrate. After a careful analysis by matrix method from the spectral transmittance data of the samples, while providing as output data the spectral transmittance, as well as the physical thickness of the films, both as functions of the aforementioned variables, the virtual surface of the source was determined.
Modelling sub-daily evaporation from a small reservoir.
NASA Astrophysics Data System (ADS)
McGloin, Ryan; McGowan, Hamish; McJannet, David; Burn, Stewart
Accurate quantification of evaporation from small water storages is essential for water management and is also required as input in some regional hydrological and meteorological models. Global estimates of the number of small storages or lakes (< 0.1 kilometers) are estimated to be in the order of 300 million (Downing et al., 2006). However, direct evaporation measurements at small reservoirs using the eddy covariance or scintillometry techniques have been limited due to their expensive and complex nature. To correctly represent the effect that small water bodies have on the regional hydrometeorology, reliable estimates of sub-daily evaporation are necessary. However, evaporation modelling studies at small reservoirs have so far been limited to quantifying daily estimates. In order to ascertain suitable methods for accurately modelling hourly evaporation from a small reservoir, this study compares evaporation results measured by the eddy covariance method at a small reservoir in southeast Queensland, Australia, to results from several modelling approaches using both over-water and land-based meteorological measurements. Accurate predictions of hourly evaporation were obtained by a simple theoretical mass transfer model requiring only over-water measurements of wind speed, humidity and water surface temperature. An evaporation model that was recently developed for use in small reservoir environments by Granger and Hedstrom (2011), appeared to overestimate the impact stability had on evaporation. While evaporation predictions made by the 1-dimensional hydrodynamics model, DYRESM (Dynamic Reservoir Simulation Model) (Imberger and Patterson, 1981), showed reasonable agreement with measured values. DYRESM did not show any substantial improvement in evaporation prediction when inflows and out flows were included and only a slighter better correlation was shown when over-water meteorological measurements were used in place of land-based measurements. Downing, J. A., Y. T. Prairie, J. J. Cole, C. M. Duarte, L. J. Tranvik, R. G. Striegl, W. H. McDowell, P. Kortelainen, N. F. Caraco, J. M. Melack and J. J. Middelburg (2006), The global abundance and size distribution of lakes, ponds, and impoundments, Limnology and Oceanography, 51, 2388-2397. Granger, R.J. and N. Hedstrom (2011), Modelling hourly rates of evaporation from small lakes, Hydrological and Earth System Sciences, 15, doi:10.5194/hess-15-267-2011. Imberger, J. and J.C. Patterson (1981), Dynamic Reservoir Simulation Model - DYRESM: 5, In: Transport Models for Inland and Coastal Waters. H.B. Fischer (Ed.). Academic Press, New York, 310-361.
Evaporative Cooling for Energy ConservationĀ
Meyer, J. R.
be required. Description 1) Reciprocating Air-Cooled chiller supplying coil added to each existing fan. 2) City water coil added to each existing fan. 3) Evaporative cooler added to each existing fan. A. E!.>umate.d CoM B ? Ac..:tw:Le. Co!.>.t. C.... E!.>umate.d Adc:LULolw..t OjOeJta..ti.ng Co!.>.t due. .to ne.w e.qLUjOme.nt Assuming the original fans could be reused at the existing flow rate of 8000 CFM with an 80 F. discharge temperature, 86 tons of cooling would be required. Since budget...
Measured soil water evaporation as a function of the square root of time and reference ET
Technology Transfer Automated Retrieval System (TEKTRAN)
Sunflower (Helianthus annuus L.) is a drought-adapted crop with a short growing season that reduces irrigation requirements and makes it ideal for regions with limited irrigation water supplies. Our objectives were a) to evaluate the yield potential of sunflower under deficit irrigation and b) det...
Energy conservation in existing caustic evaporator house
Varshney, B.S.; Mathur, T.N.S.
Process industries consume a major portion of the total energy used in industrial sector. Amongst the many other process industries 'Caustic Soda Manufacture' is the one which is highly energy-intensive. As a matter of fact it consumes fuel worth many millions of rupees in a year. Over the years the mercury cells have been replaced by diaphragm cells. One of the important factors contributing to this has been the availability of power and steam at cheap rates. In the diaphragm cells, the caustic soda produced comes out mixed with unelectrolysed salt and water known as cell liquor. The cell liquor contains varying percentage of NaOH, NaCl and water. It has a large amount of water (about 75% of the cell liquor) which is subsequently evaporated by steam in the multiple effect evaporator system depending upon the end-product concentration. Due to the large quantities of the water to be evaporated the cost of steam required for evaporation becomes so large that it controls the cost of caustic soda manufacture. Owing to many-fold escalation in the cost of fuel, over the last decade, the contribution of steam cost on the total cost of the product has further enhanced. This calls for a fresh look on the existing evaporators in order to reduce the steam consumption per tonne of caustic soda. In this paper, the important factors contributing to reduce the steam consumption for the economic operation of caustic evaporator from cell liquor concentration to 50% NaOH concentration are analysed.
The development of a new evaporation formula for TexasĀ
Moe, R. D
computers are now used to deduce the best man- agement of the water in the reservoirs. An engineer must choose a dam site with the greatest care. Shallow lakes in an area with a high evaporation rate are uneconomical because ot the large surface area... pans than from lakes. The Young screen pan was first used by the Division of Irrigation in 1936. Evaporation from this pan occurs at about the same rate as from a reservoir [2] . The Texas Board of Water Engineers, in cooperation with the Texas...
Evaporation and Infiltration from Water Bodies in the Lerma-Chapala Basin, Mexico
C. A. Scott; F. F. Flores-Lopez
Reservoirs and ponds significantly influence the hydrology of the Lerma-Chapala river basin in Mexico and affect inflows to the receiving waters of Lake Chapala. This paper reports on remote sensing and GIS assessment of the 55,511 km2 basin, in which 81 lakes and reservoirs, and 28,895 ponds were identified from post-rainy season 1998 Thematic Mapper imagery. Digital terrain analysis coupled
Reuse rate of treated wastewater in water reuse system.
Fan, Yao-bo; Yang, Wen-bo; Li, Gang; Wu, Lin-lin; Wei, Yuan-song
A water quality model for water reuse was made by mathematics induction. The relationship among the reuse rate of treated wastewater (R), pollutant concentration of reused water (Cs), pollutant concentration of influent (C0), removal efficiency of pollutant in wastewater (E), and the standard of reuse water were discussed in this study. According to the experiment result of a toilet wastewater treatment and reuse with membrane bioreactors, R would be set at less than 40%, on which all the concemed parameters could meet with the reuse water standards. To raise R of reuse water in the toilet, an important way was to improve color removal of the wastewater. PMID:16313015
Breast meat quality and consumer sensory properties of broiler carcasses chilled by water, air, or evaporative air.
Jeong, J Y; Janardhanan, K K; Booren, A M; Harte, J B; Kang, I
Three poultry chilling methods, namely, water chilling (WC), air chilling (AC), and evaporative air chilling (EAC), were compared to evaluate their effects on broiler breast meat quality and consumer sensory characteristics. A total of 189 birds were processed with 1 of the 3 chilling methods. One-third of the birds were hard scalded (57.7░C, 120 s) and subjected to WC (an ice slurry immersion at 0░C). The remaining birds were soft scalded (50░C, 220 s) and randomly assigned to either AC (blowing air, 1.0 m/s) or EAC (blowing air plus each carcass sprayed with 0.5 L of 0.4░C water) in a chilling room (0.9 ▒ 0.4░C). Water chilling reduced the carcass temperature most efficiently (57 min), whereas AC and EAC were the least (125 min) and intermediate (93 min) in efficiency, respectively. No significant difference was found among the chilling methods in moisture content, cooking yield, and shear force of deskinned breast fillets stored overnight. However, the pH (5.6) of 24-h stored fillets was higher in WC fillets than in AC (5.5) and EAC (5.5) fillets. For the surface color of skinless breasts, WC carcasses showed a higher Commission Internationale de l'╔clairage (CIE) L* value than AC or EAC carcasses, whereas AC carcasses exhibited more redness (higher CIE a*) and yellowness (higher CIE b*) than the other 2 chilling methods. When raw breast meat was made into cooked gels, no significant difference was observed in cooking loss, moisture content, shear stress, and shear strain, regardless of the chilling method. In consumer sensory evaluations, AC breasts had a higher juiciness score than did WC and EAC breasts, but no significant difference was found for flavor, texture, and overall acceptability. PMID:21325244
Evaporation of pure liquid sessile and spherical suspended drops: a review.
Erbil, H Yildirim
A sessile drop is an isolated drop which has been deposited on a solid substrate where the wetted area is limited by a contact line and characterized by contact angle, contact radius and drop height. Diffusion-controlled evaporation of a sessile drop in an ambient gas is an important topic of interest because it plays a crucial role in many scientific applications such as controlling the deposition of particles on solid surfaces, in ink-jet printing, spraying of pesticides, micro/nano material fabrication, thin film coatings, biochemical assays, drop wise cooling, deposition of DNA/RNA micro-arrays, and manufacture of novel optical and electronic materials in the last decades. This paper presents a review of the published articles for a period of approximately 120 years related to the evaporation of both sessile drops and nearly spherical droplets suspended from thin fibers. After presenting a brief history of the subject, we discuss the basic theory comprising evaporation of micrometer and millimeter sized spherical drops, self cooling on the drop surface and evaporation rate of sessile drops on solids. The effects of drop cooling, resultant lateral evaporative flux and Marangoni flows on evaporation rate are also discussed. This review also has some special topics such as drop evaporation on superhydrophobic surfaces, determination of the receding contact angle from drop evaporation, substrate thermal conductivity effect on drop evaporation and the rate evaporation of water in liquid marbles. PMID:22277832
Quantifying thick liquid films and their role in evaporative drying of porous media
NASA Astrophysics Data System (ADS)
Lehmann, P.; Willson, C.; Shokri, N.; Stampanoni, M.; Or, D.
Evaporation rate from porous media is determined by a combination of driving forces and external conditions interacting with liquid and vapor within complex pore spaces. The evaporation rate during first stage of a drying process is controlled primarily by atmospheric demand and generally is not limited by medium transport properties. Liquid connections between the evaporation surface and the receding drying front sustain sufficient water supply to maintain a constant evaporation rate. When hydraulic connections are disrupted, water transport to the surface becomes limited to rates supported by vapor diffusion. To improve our understanding of the properties of stage-one supporting liquid connections, we delineated pore geometry and liquid configuration in sand samples imaged using synchrotron X-rays tomography. As air invades large pores, remaining liquid in crevices and grain contacts form a network of thick films. We compared evaporation rates with liquid phase configuration above the drying front in an attempt to relate the end of the first stage of drying with liquid films connectivity. The dependency of high evaporation rates on residual liquid continuity implies sensitivity to surface wettability properties. These effects were examined using different mixtures of hydrophobic and hydrophilic particles and their impact on drying rates and liquid phase distribution. Improved understanding of relationships between pore scale effects, liquid configuration and evaporation processes enhances predictability of drying rates and may enable alterations or design of porous media with prescribed drying behavior.
Pilot-scale constant-rate and declining-rate direct filtration systems were evaluated for treating a high quality surface water, using two flow rates and alum or cationic polymer as the primary coagulant. Turbidity, particle count, and total coliform count were used to compare fi...
A simple rain collector preventing water re-evaporation dedicated for ?18O and ?2H analysis of cumulative precipitation samples
NASA Astrophysics Data System (ADS)
Gr÷ning, M.; Lutz, H. O.; Roller-Lutz, Z.; Kralik, M.; Gourcy, L.; P÷ltenstein, L.
SummaryA simple rainwater collector has been developed that allows virtually evaporation-free rain sampling for subsequent water stable isotope analysis. It is designed for collecting composite monthly samples as required for global monitoring networks of the isotopic composition in precipitation. The new collector has the advantages to minimize necessary staff time for sampling by easy and fast changes of sample bottles, to avoid any need of oil for prevention of evaporation, to be cheap in construction, and to be easily installed and used in remote areas (unattended during 1 month). Tests performed at the IAEA have proven that water stored in the sampler for nearly 1 year did not suffer significantly from any evaporation effect. Further comparisons performed at sampling stations of the Global Network of Isotopes in Precipitation (GNIP) show excellent performance of the new collector with advantages over some conventional precipitation samplers. Slightly more negative delta-values observed in the new collector than in conventional sampler types could indicate lower evaporation effects.
Thermal design of lithium bromide-water solution vapor absorption cooling system for indirect evaporative cooling for IT pod
NASA Astrophysics Data System (ADS)
Sawant, Digvijay Ramkrishna
Nowadays with increase use of internet, mobile there is increase in heat which ultimately increases the efficient cooling system of server room or IT POD. Use of traditional ways of cooling system has ultimately increased CO2 emission and depletion of CFC's are serious environmental issues which led scientific people to improve cooling techniques and eliminate use of CFC's. To reduce dependency on fossil fuels and 4environmental friendly system needed to be design. For being utilizing low grade energy source such as solar collector and reducing dependency on fossil fuel vapour absorption cooling system has shown a great driving force in today's refrigeration systems. This LiBr-water aabsorption cooling consists of five heat exchanger namely: Evaporator, Absorber, Solution Heat Exchanger, Generator, Condenser. The thermal design was done for a load of 23 kW and the procedure was described in the thesis. There are 120 servers in the IT POD emitting 196 W of heat each on full load and some of the heat was generated by the computer placed inside the IT POD. A detailed procedure has been discussed. A excel spreadsheet was to prepared with varying tube sizes to see the effect on flows and ultimately overall heat transfer coefficient.
Closure of the energy balance equation over bare soil during the formation and evaporation of non-rainfall water inputs
NASA Astrophysics Data System (ADS)
Florentin, Anat; Agam, Nurit
The Negev desert is characterized by an arid climate (annual mean precipitation is 90 mm) with sea breeze carrying moisture from the Mediterranean Sea during the afternoon regularly. Non-rainfall water inputs (NRWIs) are thus of great importance to the hydrometeorology and the ecological functioning of the region. The small magnitude of NRWIs challenges attempts to quantify these processes. The aim of this research was to test commonly used micrometeorological methods to quantify the energy balance components during the deposition and evaporation of NRWIs. A fully equipped micrometeorological station was set up near the Blaustein Institutes for Desert Research of the Ben-Gurion University of the Negev (30o 51' 35.6" N; 34o 46' 24.8" E) during September-October 2014. Net-radiation was measured with a 4-way net radiometer, and soil heat flux was quantified by the calorimetric method in three replicates. Latent heat was measured using an eddy-covariance (EC) and compared to a micro-lysimeter (ML); sensible heat flux was measured with an EC and a surface layer scintillometer (SLS). Sensible heat fluxes measured by the EC and the SLS showed good agreement. EC latent heat fluxes were in good agreement with those derived by the ML. Nevertheless, derivation of latent heat flux from the SLS measurements through the energy balance equation showed a relatively large deviation from the directly measured latent heat flux. This deviation is likely attributed to measurement errors of the soil heat flux.
Droplet evaporation on heated hydrophobic and superhydrophobic surfaces
NASA Astrophysics Data System (ADS)
Dash, Susmita; Garimella, Suresh V.
The evaporation characteristics of sessile water droplets on smooth hydrophobic and structured superhydrophobic heated surfaces are experimentally investigated. Droplets placed on the hierarchical superhydrophobic surface subtend a very high contact angle (ś160░) and demonstrate low roll-off angle (ś1░), while the hydrophobic substrate supports corresponding values of 120░ and ś10░. The substrates are heated to different constant temperatures in the range of 40-60 ░C, which causes the droplet to evaporate much faster than in the case of natural evaporation without heating. The geometric parameters of the droplet, such as contact angle, contact radius, and volume evolution over time, are experimentally tracked. The droplets are observed to evaporate primarily in a constant-contact-angle mode where the contact line slides along the surface. The measurements are compared with predictions from a model based on diffusion of vapor into the ambient that assumes isothermal conditions. This vapor-diffusion-only model captures the qualitative evaporation characteristics on both test substrates, but reasonable quantitative agreement is achieved only for the hydrophobic surface. The superhydrophobic surface demonstrates significant deviation between the measured evaporation rate and that obtained using the vapor-diffusion-only model, with the difference being amplified as the substrate temperature is increased. A simple model considering thermal diffusion through the droplet is used to highlight the important role of evaporative cooling at the droplet interface in determining the droplet evaporation characteristics on superhydrophobic surfaces.
Droplet evaporation on heated hydrophobic and superhydrophobic surfaces.
Dash, Susmita; Garimella, Suresh V
The evaporation characteristics of sessile water droplets on smooth hydrophobic and structured superhydrophobic heated surfaces are experimentally investigated. Droplets placed on the hierarchical superhydrophobic surface subtend a very high contact angle (?160░) and demonstrate low roll-off angle (?1░), while the hydrophobic substrate supports corresponding values of 120░ and ?10░. The substrates are heated to different constant temperatures in the range of 40-60?░C, which causes the droplet to evaporate much faster than in the case of natural evaporation without heating. The geometric parameters of the droplet, such as contact angle, contact radius, and volume evolution over time, are experimentally tracked. The droplets are observed to evaporate primarily in a constant-contact-angle mode where the contact line slides along the surface. The measurements are compared with predictions from a model based on diffusion of vapor into the ambient that assumes isothermal conditions. This vapor-diffusion-only model captures the qualitative evaporation characteristics on both test substrates, but reasonable quantitative agreement is achieved only for the hydrophobic surface. The superhydrophobic surface demonstrates significant deviation between the measured evaporation rate and that obtained using the vapor-diffusion-only model, with the difference being amplified as the substrate temperature is increased. A simple model considering thermal diffusion through the droplet is used to highlight the important role of evaporative cooling at the droplet interface in determining the droplet evaporation characteristics on superhydrophobic surfaces. PMID:24827255
Evaporation from a small prairie wetland in the Cottonwood Lake Area, North Dakota - An energy-budget study
Parkhurst, R.S.; Winter, T.C.; Rosenberry, D.O.; Sturrock, A.M.
Evaporation from Wetland Pl in the Cottonwood Lake area of North Dakota, USA was determined by the energy-budget method for 1982-85 and 1987. Evaporation rates were as high as 0.672 cm day-1. Incoming solar radiation, incoming atmospheric radiation, and long-wave radiation emitted from the water body are the largest energy fluxes to and from the wetland. Because of the small heat storage of the water body, evaporation rates closely track solar radiation on short time scales. The effect of advected energy related to precipitation is small because the water quickly heats up by solar radiation following precipitation. Advected energy related to ground water is minimal because ground-water fluxes are small and groundwater temperature is only about 7 ??C. Energy flux related to sediment heating and thermal storage in the sediments, which might be expected to be large because the water is clear and shallow, affects evaporation rates by less than 5 percent.
Realistic Hot Water Draw Specification for Rating Solar Water Heaters: Preprint
Burch, J.
In the United States, annual performance ratings for solar water heaters are simulated, using TMY weather and specified water draw. A more-realistic ratings draw is proposed that eliminates most bias by improving mains inlet temperature and by specifying realistic hot water use. This paper outlines the current and the proposed draws and estimates typical ratings changes from draw specification changes for typical systems in four cities.
Effects of evaporative cooling on the regulation of body water and milk production in crossbred Holstein cattle in a tropical environment.
Chaiyabutr, N; Chanpongsang, S; Suadsong, S
The aim of this study was to determine how evaporative cooling modifies body function with respect to water metabolism and other variables relevant to milk synthesis in crossbred cattle. The study was conducted on two groups of 0.875HF:0.125RS crossbred Holstein cattle (87.5%) housed in an open-sided barn with a tiled roof (non-cooled animals) and in a close-sided barn under an evaporative cooling system (cooled animals). The maximum ambient temperature and relative humidity for the non-cooled group were 33 degrees C and 61%, with the corresponding values for the evaporatively cooled barn being 28 degrees C and 84%, respectively. The temperature humidity index (THI) of under non-cooled conditions was higher (P < 0.05) than that in the cooled barn. Rectal temperatures and respiration rates of non-cooled animals were higher (P < 0.05) than those of cooled animals. Daily dry matter intake (DMI) of cooled animals was higher while water intakes were lower (P < 0.05) than those of non-cooled animals. The mean absolute values of plasma volume, blood volume, and extracellular fluid (ECF) of cooled animals were significantly higher (P < 0.05) than those of non-cooled animals throughout all stages of lactation. Milk yields of cooled animals were higher by 42%, 36% and 79% on average than those of non-cooled animals during early-, mid- and late-lactation, respectively. The decline in milk yields as lactation advances was markedly apparent in late-lactating non-cooled animals, while no significant changes in milk composition at different stages of lactation were observed in either group. Mean arterial plasma concentrations, arteriovenous concentration differences (A-V differences) and the extraction ratio across the mammary gland for acetate, glucose and triglyceride of cooled animals were not significantly different compared with values for non-cooled animals. No differences were seen in plasma hormonal levels for triiodotyronine (T(3)) and insulin-like growth factor-1 (IGF-1), but plasma cortisol and thyroxine (T(4)) levels tended to be lower in non-cooled animals. This study suggests that low cooling temperature accompanied by high humidity influences a galactopoietic effect, in part through increases in ECF, blood volume and plasma volume in association with an increase in DMI, which partitions the distribution of nutrients to the mammary gland for milk synthesis. Cooled animals were unable to maintain high milk yield as lactation advances even though a high level of body fluids was maintained during long-term cooled exposure. The decline in milk yield, coinciding with a decrease in net energy for lactation as lactation advances, could be attributed to a local change within the mammary gland. PMID:18427839
Kinetic multi-layer model of gas-particle interactions in aerosols and clouds (KM-GAP): linking condensation, evaporation and chemical reactions of organics, oxidants and water
NASA Astrophysics Data System (ADS)
Shiraiwa, M.; Pfrang, C.; Koop, T.; P÷schl, U.
We present a novel kinetic multi-layer model for gas-particle interactions in aerosols and clouds (KM-GAP) that treats explicitly all steps of mass transport and chemical reaction of semi-volatile species partitioning between gas phase, particle surface and particle bulk. KM-GAP is based on the PRA model framework (P÷schl-Rudich-Ammann, 2007), and it includes gas phase diffusion, reversible adsorption, surface reactions, bulk diffusion and reaction, as well as condensation, evaporation and heat transfer. The size change of atmospheric particles and the temporal evolution and spatial profile of the concentration of individual chemical species can be modeled along with gas uptake and accommodation coefficients. Depending on the complexity of the investigated system and the computational constraints, unlimited numbers of semi-volatile species, chemical reactions, and physical processes can be treated, and the model shall help to bridge gaps in the understanding and quantification of multiphase chemistry and microphysics in atmospheric aerosols and clouds. In this study we demonstrate how KM-GAP can be used to analyze, interpret and design experimental investigations of changes in particle size and chemical composition in response to condensation, evaporation, and chemical reaction. For the condensational growth of water droplets, our kinetic model results provide a direct link between laboratory observations and molecular dynamic simulations, confirming that the accommodation coefficient of water at ~270 K is close to unity (Winkler et al., 2006). Literature data on the evaporation of dioctyl phthalate as a function of particle size and time can be reproduced, and the model results suggest that changes in the experimental conditions like aerosol particle concentration and chamber geometry may influence the evaporation kinetics and can be optimized for efficient probing of specific physical effects and parameters. With regard to oxidative aging of organic aerosol particles, we illustrate how the formation and evaporation of volatile reaction products like nonanal can cause a decrease in the size of oleic acid particles exposed to ozone.
Original article Irrigation, faecal water content and development rate
Paris-Sud XI, Universitķ de
Original article Irrigation, faecal water content and development rate of free-living stages of irrigation by flooding the pastures on the ability of the eggs of sheep Tri- chostrongyles to develop irrigation or submerged, at different times and durations. The rates of development of Teladorsagia
Technology Transfer Automated Retrieval System (TEKTRAN)
Surveys conducted recently revealed that a wide variety of nipple flow rates are being routinely used in broiler houses throughout the southern broiler producing states. A study was conducted to determine if the variety of nipple water flow rates found in industry has any effect on broiler performan...
Changes in wintertime evaporation and surface energy budget in 2007 and 2008 over an open water surface in Mississippi, U.S.A
H. Liu; Y. Zhang
Using data measured from an eddy covariance system during two winters in 2007 and 2008, we examined how synoptic weather events affect wintertime evaporation and surface energy budget over an open water surface. The measurements were conducted in the Ross Barnett reservoir (32o26'N, 90o02'W), Mississippi, U.S.A. The fetch for the eddy covariance system exceeded 2 km in all directions and
Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf
Simonin, Kevin A.; Burns, Emily; Choat, Brendan; Barbour, Margaret M.; Dawson, Todd E.; Franks, Peter J.
Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (??stem¢leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO2 concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO2 concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO2 on g s. The positive relationship between k leaf and E minimized variation in ??stem¢leaf. This enables leaves to minimize variation in ?leaf and maximize g s and CO2 assimilation rate over the diurnal course of evaporative demand. PMID:25547915
Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf.
Simonin, Kevin A; Burns, Emily; Choat, Brendan; Barbour, Margaret M; Dawson, Todd E; Franks, Peter J
Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (??stem-leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO? concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO? concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO? on g s. The positive relationship between k leaf and E minimized variation in ??stem-leaf. This enables leaves to minimize variation in ?leaf and maximize g s and CO? assimilation rate over the diurnal course of evaporative demand. PMID:25547915
Prevention against Oxidation of Mn Evaporant during Reactive Evaporation Process
Masaaki Isai; Hiroshi Fujiyasu
Manganese oxide films for lithium secondary batteries were prepared using a reactive evaporation method. The Mn metal in the crucible suffers severe oxidation during the reactive evaporation process, during which its deposition rate deteriorates with increasing deposition run. So it is difficult to maintain the stoichiometry of films from run to run. To prevent deteriorations, a quartz ampoule has been
Microdroplet evaporation with a forced pinned contact line.
Gleason, Kevin; Putnam, Shawn A
Experimental and numerical investigations of water microdroplet evaporation on heated, laser patterned polymer substrates are reported. The study is focused on both (i) controlling a droplet's contact line dynamics during evaporation to identifying how the contact line influences evaporative heat transfer and (ii) validating numerical simulations with experimental data. Droplets are formed on the polymer surface using a bottom-up methodology, where a computer-controlled syringe pump feeds water through a 200 ?m diameter fluid channel within the heated polymer substrate. This methodology facilitates precise control of the droplet's growth rate, size, and inlet temperature. In addition to this microchannel supply line, the substrate surfaces are laser patterned with a moatlike trench around the fluid-channel outlet, adding additional control of the droplet's contact line motion, area, and contact angle. In comparison to evaporation on a nonpatterned polymer surface, the laser patterned trench increases contact line pinning time by ?60% of the droplet's lifetime. Numerical simulations of diffusion controlled evaporation are compared the experimental data with a pinned contact line. These diffusion based simulations consistently over predict the droplet's evaporation rate. In efforts to improve this model, a temperature distribution along the droplet's liquid-vapor interface is imposed to account for the concentration distribution of saturated vapor along the interface, which yields improved predictions within 2-4% of the experimental data throughout the droplet's lifetime on heated substrates. PMID:25102248
The stable isotope composition of transpired water and the rate of change in leaf water enrichment in response to variable environments
NASA Astrophysics Data System (ADS)
Simonin, K. A.; Roddy, A. B.; Link, P.; Apodaca, R. L.; Tu, K. P.; Hu, J.; Dawson, T. E.; Barbour, M.
Previous research has shown that during daylight hours the isotope composition of leaf water is generally well approximated by steady-state leaf water isotope enrichment models. However, there is little direct confirmation of isotopic steady state (ISS) transpiration. Here we use a novel method to evaluate the frequency (or infrequency) of ISS transpiration and the rate of change in leaf water enrichment when leaves are exposed to a variable environment. Specifically, our study had three goals. First, we wanted to develop a new method to measure the isotope fluxes of transpiration that relies on isotope ratio infrared spectroscopy (IRIS) and highlight how an IRIS instrument can be coupled to plant gas exchange systems. In doing so, we also developed a method for controlling the absolute humidity entering the gas exchange cuvettes across a wide range of concentrations (approximately 4000 ppmv to 22000 ppmv) without changing the isotope composition of water vapour entering the cuvette. Second, we quantified variation in the isotope composition of transpired water vapor and the rate of change in leaf water enrichment that can occur as a result of changes in relative humidity, leaf surface conductance to water vapour, leaf temperature and the isotope composition of atmospheric water vapor. Third, we examine the differences between steady state and non-steady state model predictions of leaf water enrichment at the site of evaporation. In our measurements the isotopic compositions of transpired water were neither stable nor equal to source water until leaves had been maintained at physiological steady state for at least 40 minutes. Additionally when transpiration was not at ISS, the steady state model predictions of leaf water enrichment at the site of evaporation exceeded non steady-state model predictions by up to 8 per mil. Further, the rate of change in leaf water enrichment was highly sensitive to variation in leaf water content. Our results suggest that a variable environment is likely to preclude isotopic steady-state transpiration and that this effect would be exacerbated by lengthy leaf water turnover times.
Improving the conceptualization of the evaporation flux in conceptual rainfall-runoff models by using remotely sensed catchment scale evaporation estimates.
NASA Astrophysics Data System (ADS)
Aalbers, Emma; Coenders-Gerrits, Miriam; Savenije, Hubert
If we look at how evaporation is modelled in commonly used lumped conceptual rainfall-runoff models, the static nature of the conceptualization is striking. In this conceptualization the evaporation flux usually is linearly related to the relative soil moisture content until a certain threshold is reached, after which evaporation takes place at the potential rate. The potential evaporation is a function of meteorological parameters, sometimes it includes a surface resistance term or a scaling factor to account for different land use types in the catchment. Vegetation specific variables and the dynamics associated with the seasons (e.g. phenology, effects of soil temperature) are generally not explicitly taken into account. This means that the dynamic character of evaporation in these lumped rainfall-runoff models is only expressed by the dynamics in water availability - i.e. a function of precipitation (model input) and the partitioning of water - and a form of available energy for vaporization. Moreover, the modeled evaporation flux is the aggregated flux over the entire catchment. How can spatial variability in the temporal dynamics be expressed in these models? In other words, to what extent does the modeled evaporation flux represent the 'real' evaporation integrated over the entire catchment? Since temporally continuous evaporation observations are not available at the scale of the catchment this cannot be tested straightforwardly. What is available is a range of remote sensing techniques for upscaling point measurements of evaporation to the catchment scale or to estimate evaporation from thermal images. In this research catchment scale evaporation estimates from the SEBS algorithm combined with optical remote sensing data are explored. This provides snapshots of the spatial variability of evaporation throughout the year, which can be used to determine homogeneous functional areas within the catchment with comparable temporal dynamics in evaporation. With that information the switch to a semi-distributed model can be made, providing the possibility to capture more of the spatial and temporal character of evaporation by adjusting the conceptualization and/or parameterization of the evaporation flux per 'functional area'. We analyze the value of the ancillary remote sensing evaporation data and whether we can use this data to actually improve the conceptualization of the evaporation flux and therewith model performance.
Theoretical and testing performance of an innovative indirect evaporative chiller
Jiang, Yi; Xie, Xiaoyun [Department of Building Science and Technology, Tsinghua University, Beijing (China)
An indirect evaporative chiller is a device used to produce chilled water at a temperature between the wet bulb temperature and dew point of the outdoor air, which can be used in building HVAC systems. This article presents a theoretical analysis and practical performance of an innovative indirect evaporative chiller. First, the process of the indirect evaporative chiller is introduced; then, the matching characteristics of the process are presented and analyzed. It can be shown that the process that produces cold water by using dry air is a nearly-reversible process, so the ideal produced chilled water temperature of the indirect evaporative chiller can be set close to the dew point temperature of the chiller's inlet air. After the indirect evaporative chiller was designed, simulations were done to analyze the output water temperature, the cooling efficiency relative to the inlet dew point temperature, and the COP that the chiller can performance. The first installation of the indirect evaporative chiller of this kind has been run for 5 years in a building in the city of Shihezi. The tested output water temperature of the chiller is around 14-20 C, which is just in between of the outdoor wet bulb temperature and dew point. The tested COP{sub r,s} of the developed indirect evaporative chiller reaches 9.1. Compared with ordinary air conditioning systems, the indirect evaporative chiller can save more than 40% in energy consumption due to the fact that the only energy consumed is from pumps and fans. An added bonus is that the indirect evaporative chiller uses no CFCs that pollute to the aerosphere. The tested internal parameters, such as the water-air flow rate ratio and heat transfer area for each heat transfer process inside the chiller, were analyzed and compared with designed values. The tested indoor air conditions, with a room temperature of 23-27 C and relative humidity of 50-70%, proved that the developed practical indirect evaporative chiller successfully satisfy the indoor air conditioning load for the demo building. The indirect evaporative chiller has a potentially wide application in dry regions, especially for large scale commercial buildings. Finally, this paper presented the geographic regions suitable for the technology worldwide. (author)
Evaporation of sessile droplets affected by graphite nanoparticles and binary base fluids.
Zhong, Xin; Duan, Fei
The effects of ethanol component and nanoparticle concentration on evaporation dynamics of graphite-water nanofluid droplets have been studied experimentally. The results show that the formed deposition patterns vary greatly with an increase in ethanol concentration from 0 to 50 vol %. Nanoparticles have been observed to be carried to the droplet surface and form a large piece of aggregate. The volume evaporation rate on average increases as the ethanol concentration increases from 0 to 50 vol % in the binary mixture nanofluid droplets. The evaporation rate at the initial stage is more rapid than that at the late stage to dry, revealing a deviation from a linear fitting line, standing for a constant evaporation rate. The deviation is more intense with a higher ethanol concentration. The ethanol-induced smaller liquid-vapor surface tension leads to higher wettability of the nanofluid droplets. The graphite nanoparticles in ethanol-water droplets reinforce the pinning effect in the drying process, and the droplets with more ethanol demonstrate the depinning behavior only at the late stage. The addition of graphite nanoparticles in water enhances a droplet baseline spreading at the beginning of evaporation, a pinning effect during evaporation, and the evaporation rate. However, with a relatively high nanoparticle concentration, the enhancement is attenuated. PMID:25372453
Impact of ambient conditions on evaporation from porous media
NASA Astrophysics Data System (ADS)
Ben Neriah, Asaf; Assouline, Shmuel; Shavit, Uri; Weisbrod, Noam
The complexity of soil evaporation, depending on the atmospheric conditions, emphasizes the importance of its quantification under potential changes in ambient air temperature, Ta, and relative humidity, RH. Mass loss, soil matric tension, and meteorological measurements, carried out in a climate-controlled laboratory, were used to study the effect of ambient conditions on the drying rates of a porous medium. A set of evaporation experiments from initially saturated sand columns were carried out under constant Ta of 6, 15, 25, and 35░C and related RH (0.66, 0.83, 1.08, and 1.41 kPa, respectively). The results show that the expected increase of the stage 1 (S1) evaporation rate with Ta but also revealed an exponential-like reduction in the duration of S1, which decreased from 29 to 2.3 days (at Ta of 6 and 35░C, respectively). The evaporation rate, e(t), was equal to the potential evaporation, ep(t), under Ta = 6░C, while it was always smaller than ep(t) under higher Ta. The cumulative evaporation during S1 was higher under Ta = 6░C than under the higher temperatures. Evaporation rates during S2 were practically unaffected by ambient conditions. The results were analyzed using a mass transfer formulation linking e(t) with the vapor pressure deficit through a resistance coefficient r. It was shown that rS1 (the resistance during S1) is constant, indicating that the application of such an approach is straightforward during S1. However, for evaporation from a free water surface and S2, the resistances, rBL and rS2, were temperature-dependent, introducing some complexity for these cases.
Carrier Gas Dependent Evaporation Energy of GaN Estimated from Spiral Growth Rates in Selective-Area Metalorganic Vapor Phase Epitaxy
NASA Astrophysics Data System (ADS)
Akasaka, Tetsuya; Kobayashi, Yasuyuki; Kasu, Makoto; Yamamoto, Hideki
GaN was grown in spiral growth mode by metalorganic vapor phase epitaxy in selective areas having screw-type dislocations. Relationships between the growth rate and supersaturation provide a novel way to estimate the evaporation energy of GaN, which turns out to be carrier gas dependent: 4.3▒0.9 eV for N2 and 2.1▒0.4 eV for H2. The latter is significantly smaller, probably due to enhanced etching by H2. Suppression of excessive nucleation by etching in H2 may be responsible for the formation of step-free GaN surfaces at low temperatures in selective areas free from screw-type dislocations.
Characteristic lengths affecting evaporative drying of porous media.
Lehmann, Peter; Assouline, Shmuel; Or, Dani
Evaporation from porous media involves mass and energy transport including phase change, vapor diffusion, and liquid flow, resulting in complex displacement patterns affecting drying rates. Force balance considering media properties yields characteristic lengths affecting the transition in the evaporation rate from a liquid-flow-based first stage limited only by vapor exchange with air to a second stage controlled by vapor diffusion through the medium. The characteristic lengths determine the extent of the hydraulically connected region between the receding drying front and evaporating surface (film region) and the onset of flow rate limitations through this film region. Water is displaced from large pores at the receding drying front to supply evaporation from hydraulically connected finer pores at the surface. Liquid flow is driven by a capillary pressure gradient spanned by the width of the pore size distribution and is sustained as long as the capillary gradient remains larger than gravitational forces and viscous dissipation. The maximum extent of the film region sustaining liquid flow is determined by a characteristic length L_{C} combining the gravity characteristic length L_{G} and viscous dissipation characteristic length L_{V} . We used two sands with particle sizes 0.1-0.5 mm ("fine") and 0.3-0.9 mm ("coarse") to measure the evaporation from columns of different lengths under various atmospheric evaporative demands. The value of L_{G} determined from capillary pressure-saturation relationships was 90 mm for the coarse sand and 140 mm for the fine sand. A significant decrease in drying rate occurred when the drying front reached the predicted L_{G} value (viscous dissipation was negligibly small in sand and L_{C} approximately L_{G} ). The approach enables a prediction of the duration of first-stage evaporation with the highest water losses from soil to the atmosphere. PMID:18643163
Measurement of the rate of water translocation through carbon nanotubes.
Qin, Xingcai; Yuan, Quanzi; Zhao, Yapu; Xie, Shubao; Liu, Zhongfan
We present an approach for measuring the water flow rate through individual ultralong carbon nanotubes (CNTs) using field effect transistors array defined on individual tubes. Our work exhibits a rate enhancement of 882-51 and a slip length of 53-8 nm for CNTs with diameters of 0.81-1.59 nm. We also found that the enhancement factor does not increase monotonically with shrinking tube diameter and there exists a discontinuous region around 0.98-1.10 nm. We believe that these single-tube level results would help understand the intrinsic nanofluidics of water in CNTs. PMID:21462938
Synthesis on evaporation partitioning using stable isotopes
NASA Astrophysics Data System (ADS)
Coenders-Gerrits, Miriam; Bogaard, Thom; Wenninger, Jochen; Jonson Sutanto, Samuel
Partitioning of evaporation into productive (transpiration) and non-productive evaporation (interception, soil evaporation) is of highest importance for water management practices, irrigation scheme design, and climate modeling. Despite this urge, the magnitude of the ratio of transpiration over total evaporation is still under debate and poorly understood due to measuring difficulties. However, with the current development in isotope measuring devices, new opportunities arise to untangle the partitioning of evaporation. In this paper we synthesize the opportunities and limitations using stable water isotopes in evaporation partitioning. We will analyze a set of field as well as laboratory studies to demonstrate the different evaporation components for various climate and vegetation conditions using stable isotopes 18O/16O and 2H/1H. Experimental data on evaporation partitioning of crops, grass, shrubs and trees are presented and we will discuss the specific experimental set-ups and data collection methods. The paper will be a synthesis of these studies.
Recent studies are reviewed to provide a comprehensive volume on state-of-the-art formulations used in surface water quality modeling along with accepted values for rate constants and coefficients. Topics covered include system geometric representation (spatial and temporal), phy...
Computation of infrared cooling rates in the water vapor bands
NASA Technical Reports Server (NTRS)
Chou, M.-D.; Arking, A.
A fast and accurate method is developed for calculating the infrared radiative terms due to water vapor - specifically, the atmospheric cooling rates. The accuracy is achieved by avoiding the constraints of band models and working directly with the absorption coefficient, which is a function of temperature and pressure as well as wavenumber. The method is based on calculation of an equivalent water vapor amount between atmospheric pressure levels and a table look-up procedure. Compared to line-by-line calculations, the present method has errors up to 4% of the maximum cooling rate. The use of a scaling factor, based on the far-wing approximation, limits the applicability of the method to the troposphere and lower stratosphere, where the line wings are responsible for most of the radiative cooling associated with water vapor.
A fundamental cause of an enormous amount of evaporation during rainfall by canopy interception: Evaporative force proposed by Makarieva and Gorshkov
NASA Astrophysics Data System (ADS)
Murakami, Shigeki
An enormous amount of evaporation from forest canopy is observed during rainfall as canopy interception. The evaporation rate often exceeds well over 10 mm h-1 that requires latent heat of five times solar constant (6814 W m-2 at 20░C). On top of that, evaporation rate is proportional to the rainfall intensity. Namely, once the saturation of canopy is reached, the ratio of canopy interception to gross rainfall remains constant during the rainfall regardless of the intensity of the storm, e.g. approximately 20% of the rainfall in a Japanese cypress stand. This enigmatic phenomenon includes several cardinal problems to solve. As for the mechanism of a huge amount of evaporation, Murakami (2006, 2007; J. Hydrol.) proposed splash droplet evaporation, and is supported by Dunkerley (2009; J. Hydrol.). As the size and the number of raindrops increase with rainfall intensity (Marshall-Palmer distribution), so does the number of splash droplets produced by raindrops hitting the canopy. A host of small droplets with huge combined surface area highly boost evaporation, which means water evaporates from the splash droplets as well as the canopy. However, unless water vapor above canopy is removed and transported somewhere else, water vapor saturates and evaporation stops. Makarieva and Gorshkov (2007; HESS) advocated a new theory that can elucidate an enormous amount of evaporation and water vapor transport termed "evaporative force" or "the Biotic Pump Theory"(BPT). Though they do not deal with evaporation during rain events explicitly, it is applicable to the evaporation for the period of rainfall, i.e. canopy interception. Molecular weight of H2O, 18, is smaller than the average value of air 29 that works for water vapor as buoyancy. As a result, water vapor is removed since it goes up by itself and condenses at the bottom of cloud. In the cloud latent heat is released that will be transported down to the canopy being pulled down with raindrops or in exchange for water vapor ascending from the canopy. It is postulated that both latent heat and water circulate between the canopy and the cloud. Though Makarieva and Gorshkov (2007) claims that forest makes rain inland due to the strong evaporation from forest that "sucks in" water vapor from the ocean, they give canopy interception only a one-line mention. Canopy interception is a major component of evapotranspiration from forest that enables forest to evaporate larger amount of water than other surfaces on the earth, and the Biotic Pump does not function without canopy interception. Conversely, the mechanism of canopy interception is not explainable without evaporative force, and the fundamental cause of canopy interception is evaporative force. BPT is strongly supported by the observational facts of canopy interception and the splash droplet evaporation hypothesis. The study of canopy interception can be used as the tool to verify evaporative force that has the high potential of the development in the atmospheric boundary layer study.
Experimental Investigation of Microstructured Evaporators
NASA Astrophysics Data System (ADS)
Wibel, W.; Westermann, S.; Maikowske, S.; Brandner, J. J.
Microfluidic devices have become more and more popular over the last decades [1]. Cooling is a topic where microstructures offer significant advantages compared to conventional techniques due the much higher possible surface to volume ratios and short heat transfer lengths. By evaporating of a fluid in microchannels, compact, fast and powerful cooling devices become possible [2]. Experimental results for different designs of microstructured evaporators are presented here. They have been obtained either using water as evaporating coolant or the refrigerant R134a (Tetrafluoroethane). A new microstructured evaporator design consisting of bended microchannels instead of straight channels for a better performance is shown and compared to previous results [2] for the evaporation of R134a in straight microchannels.
Numerical study of evaporation-induced salt accumulation and precipitation in bare saline soils: Mechanism and feedback
NASA Astrophysics Data System (ADS)
Zhang, Chenming; Li, Ling; Lockington, David
Evaporation from bare saline soils in coastal wetlands causes salt precipitation in the form of efflorescence and subflorescence. However, it is not clear how much the precipitated salt in turn affects the water transport in the soil and hence the evaporation rate. We hypothesized that efflorescence exerts a mulching resistance to evaporation, while subflorescence reduces the pore space for water vapor to move through the soil. A numerical model is developed to simulate the transport of water, solute, and heat in the soil, and resulting evaporation and salt precipitation with the hypothesized feedback mechanism incorporated. The model was applied to simulate four evaporation experiments in soil columns with and without a fixed shallow water table, and was found to replicate well the experimental observations. The simulated results indicated that as long as the hydraulic connection between the near surface soil layer and the water source in the interior soil layer exists, vaporization occurs near the surface, and salt precipitates exclusively as efflorescence. When such hydraulic connection is absent, the vaporization plane develops downward and salt precipitates as subflorescence. Being more substantial in quantity, efflorescent affects more significantly evaporation than subflorescence during the soil-drying process. Different evaporation stages based on the location of the vaporization plane and the state of salt accumulation can be identified for characterizing the process of evaporation from bare saline soils with or without a fixed shallow water table.
Photoluminescence and anti-deliquesce of cesium iodide and its sodium-doped films deposited by thermal evaporation at high deposition rates
NASA Astrophysics Data System (ADS)
Hsu, Jin-Cherng; Chiang, Yueh-Sheng; Ma, Yu-Sheng
Cesium iodide (CsI) and sodium iodide (NaI) are good scintillators due to their high luminescence efficiency. These alkali halides can be excited by ultra-violet or by ionizing radiation. In this study, CsI and its Na-doped films about 8 ?m thick were deposited by thermal evaporation boat without heating substrates at high deposition rates of 30, 50, 70, 90, and 110 nm/sec, respectively. The as-deposited films were sequentially deposited a silicon dioxide film to protect from deliquesce. And, the films were also post-annealed in vacuum at 150, 200, 250, and 300 ░C, respectively. We calculated the packing densities of the samples according to the measurements of Fourier transform infrared spectroscopy (FTIR) and observed the luminescence properties by photoluminescence (PL) system. The surfaces and cross sections of the films were investigated by scanning electron microscope (SEM). From the above measurements we can find the optimal deposition rate of 90 nm/sec and post-annealing temperature of 250 ░C in vacuum for the asdeposited cesium iodide and its sodium-doped films.
Evaporation of forsterite in H 2 gas
Hiroko Nagahara; Kazuhito Ozawa
Kinetics of evaporation of forsterite in hydrogen gas was investigated by high temperature vacuum experiments in the pressure range plausible for the solar nebula. The evaporation rate at total pressure (Ptot) below 10?6 bar is nearly constant and is similar to that in vacuum, whereas the rate at 10?6 to 10?3 bar is dependent on Ptot. The evaporation rate, JexpFo,
Water vapor pressure versus environmental lapse rate near the tropopause
NASA Astrophysics Data System (ADS)
Ferreira, Antonio; Castanheira, Jose; Gimeno, Luis
The relationship between water vapor pressure and temperature lapse rate in the vicinity of the tropopause was investigated using in situ observations. The water vapor partial pressures and the lapse rates within a vertical distance of ▒1.5 km around the first thermal tropopause were calculated from the vertical soundings conducted by the NOAA/CMDL at several locations in the last few decades (GMD Data Archive). A positive non-linear relationship between the two quantities was found to hold across the studied tropopause region at mid-latitudes and polar latitudes. A similar analysis was performed on the 300 and 250 hPa pressure levels (which often intercept the tropopause region), by collecting temperature and humidity observations within 1979-2008 from the Integrated Global Radiosonde Archive (IGRA). A relationship having almost the same shape was detected for statically stable lapse rates at all latitude zones. Given the relevance of water vapor in the radiative transfer in the upper troposphere, the results are an indication of a local influence of water vapor on the thermal structure of the transition layer between the troposphere and stratosphere
Atmospheric emissions from the Deepwater Horizon spill constrain air-water partitioning, hydrocarbon fate, and leak rate
NASA Astrophysics Data System (ADS)
Ryerson, T. B.; Aikin, K. C.; Angevine, W. M.; Atlas, E. L.; Blake, D. R.; Brock, C. A.; Fehsenfeld, F. C.; Gao, R.-S.; de Gouw, J. A.; Fahey, D. W.; Holloway, J. S.; Lack, D. A.; Lueb, R. A.; Meinardi, S.; Middlebrook, A. M.; Murphy, D. M.; Neuman, J. A.; Nowak, J. B.; Parrish, D. D.; Peischl, J.; Perring, A. E.; Pollack, I. B.; Ravishankara, A. R.; Roberts, J. M.; Schwarz, J. P.; Spackman, J. R.; Stark, H.; Warneke, C.; Watts, L. A.
The fate of deepwater releases of gas and oil mixtures is initially determined by solubility and volatility of individual hydrocarbon species; these attributes determine partitioning between air and water. Quantifying this partitioning is necessary to constrain simulations of gas and oil transport, to predict marine bioavailability of different fractions of the gas-oil mixture, and to develop a comprehensive picture of the fate of leaked hydrocarbons in the marine environment. Analysis of airborne atmospheric data shows massive amounts (ś258,000 kg/day) of hydrocarbons evaporating promptly from the Deepwater Horizon spill; these data collected during two research flights constrain air-water partitioning, thus bioavailability and fate, of the leaked fluid. This analysis quantifies the fraction of surfacing hydrocarbons that dissolves in the water column (ś33% by mass), the fraction that does not dissolve, and the fraction that evaporates promptly after surfacing (ś14% by mass). We do not quantify the leaked fraction lacking a surface expression; therefore, calculation of atmospheric mass fluxes provides a lower limit to the total hydrocarbon leak rate of 32,600 to 47,700 barrels of fluid per day, depending on reservoir fluid composition information. This study demonstrates a new approach for rapid-response airborne assessment of future oil spills.
Phosphorus: A Rate Limiting Nutrient in Surface Waters
D. L. Correll
ABSTRACT Phosphorus,is an essential element,for all life forms. It is a mineral,nutrient. Orthophosphate,is the only form,of P that autotrophs,can assimilate. Extracel- lular enzymes,hydrolyze,organic,forms,of P to phos- phate. Eutrophication,is the over-enrichment,of surface waters,with mineral,nutrients. The results are excessive production of autotrophs, especially algae and cyanobacteria.,This high,productivity,leads,to,high bacterial populations and high respiration rates, leading to hypoxia,or anoxia in poorly,mixed,bottom,waters,and at night in
CONDENSATION As noted previously, heat energy imparted to water as it
Brody, James P.
CONDENSATION As noted previously, heat energy imparted to water as it evaporates is returned to liquid water as vapor condenses. During low tide, the rate of evaporation typically exceeds the rate is lowered. For example, water condenses on a glass of iced tea or a can of cold beer. Similarly
Power plant cooling system water consumption and nonwater impact reports. Executive summary August 1979-April 1981
Hu, M.C.; Pavlenco, G.F.; Englesson, G.A.
Water evaporation and consumption of power plant cooling systems were studied and six simple generic evaporation prediction models were evaluated, one for cooling towers and five for cooling ponds/lakes using field data provided by twelve utilities. Also evaluated in the study is a regional comparison of evaporation rates of cooling towers and cooling ponds/lakes with the objective of determining which of the two cooling system types is more water consumptive in terms of evaporation only.
Rate law analysis of water oxidation on a hematite surface.
Le Formal, Florian; Pastor, Ernest; Tilley, S David; Mesa, Camilo A; Pendlebury, Stephanie R; Grõtzel, Michael; Durrant, James R
Water oxidation is a key chemical reaction, central to both biological photosynthesis and artificial solar fuel synthesis strategies. Despite recent progress on the structure of the natural catalytic site, and on inorganic catalyst function, determining the mechanistic details of this multiredox reaction remains a significant challenge. We report herein a rate law analysis of the order of water oxidation as a function of surface hole density on a hematite photoanode employing photoinduced absorption spectroscopy. Our study reveals a transition from a slow, first order reaction at low accumulated hole density to a faster, third order mechanism once the surface hole density is sufficient to enable the oxidation of nearest neighbor metal atoms. This study thus provides direct evidence for the multihole catalysis of water oxidation by hematite, and demonstrates the hole accumulation level required to achieve this, leading to key insights both for reaction mechanism and strategies to enhance function. PMID:25936408
Rate Law Analysis of Water Oxidation on a Hematite Surface
Water oxidation is a key chemical reaction, central to both biological photosynthesis and artificial solar fuel synthesis strategies. Despite recent progress on the structure of the natural catalytic site, and on inorganic catalyst function, determining the mechanistic details of this multiredox reaction remains a significant challenge. We report herein a rate law analysis of the order of water oxidation as a function of surface hole density on a hematite photoanode employing photoinduced absorption spectroscopy. Our study reveals a transition from a slow, first order reaction at low accumulated hole density to a faster, third order mechanism once the surface hole density is sufficient to enable the oxidation of nearest neighbor metal atoms. This study thus provides direct evidence for the multihole catalysis of water oxidation by hematite, and demonstrates the hole accumulation level required to achieve this, leading to key insights both for reaction mechanism and strategies to enhance function. PMID:25936408
Evaporation Into the Atmosphere: Theory, History, and Applications
Harvey E. Jobson
Evaporation is a topic that crosses several disciplines, and comprehensive texts on the subject are rare. Evaporation Into the Atmosphere is, therefore, a welcome addition to the literature. The approach to the determination of evaporation varies significantly depending upon the constraints that control the system of interest. The oceanographer, for example, is concerned with evaporation from large bodies of water
A general mathematical model of evaporative cooling devices
Boris Halasz
In this paper a general nondimensional mathematical model for the description of all types of evaporative cooling devices in today's use (water cooling towers, evaporative condensers and evaporative fluid coolers, air washers, dehumidifying coils etc.) is presented. The system of differential equations describing nonadiabatic evaporation processes is transformed to a pure nondimensional form by the introduction of nondimensional coordinates and
Evaporative losses from soils covered by physical and different types of biological soil crusts
Chamizo, S.; Cant¾n, Y.; Domingo, F.; Belnap, J.
Evaporation of soil moisture is one of the most important processes affecting water availability in semiarid ecosystems. Biological soil crusts, which are widely distributed ground cover in these ecosystems, play a recognized role on water processes. Where they roughen surfaces, water residence time and thus infiltration can be greatly enhanced, whereas their ability to clog soil pores or cap the soil surface when wetted can greatly decrease infiltration rate, thus affecting evaporative losses. In this work, we compared evaporation in soils covered by physical crusts, biological crusts in different developmental stages and in the soils underlying the different biological crust types. Our results show that during the time of the highest evaporation (Day 1), there was no difference among any of the crust types or the soils underlying them. On Day 2, when soil moisture was moderately low (11%), evaporation was slightly higher in well-developed biological soil crusts than in physical or poorly developed biological soil crusts. However, crust removal did not cause significant changes in evaporation compared with the respective soil crust type. These results suggest that the small differences we observed in evaporation among crust types could be caused by differences in the properties of the soil underneath the biological crusts. At low soil moisture (<6%), there was no difference in evaporation among crust types or the underlying soils. Water loss for the complete evaporative cycle (from saturation to dry soil) was similar in both crusted and scraped soils. Therefore, we conclude that for the specific crust and soil types tested, the presence or the type of biological soil crust did not greatly modify evaporation with respect to physical crusts or scraped soils.
Simulations of water transport through carbon nanotubes: how different water models influence the conduction rate.
Liu, L; Patey, G N
The conduction rate of water through (8,8) and (9,9) carbon nanotubes at 300 K and a pressure difference of 220 MPa is investigated using molecular dynamics simulations. The TIP3P, SPC/E, and TIP4P/2005 water models are considered. The pressure-driven flow rate is found to be strongly model dependent for both nanotubes. The fastest model (TIP3P) has a flow rate that is approximately five times faster than the slowest (TIP4P/2005). It is shown that the flow rate is significantly influenced by the structure taken on by the water molecules confined in the nanotube channels. The slower models, TIP4P/2005 and SPC/E, tend to favor stacked ring arrangements, with the molecules of a ring moving together through the nanotube, in what we term a "cluster-by-cluster" conduction mode. Confined TIP3P water has a much weaker tendency to form ring structures, and those that do form are fragile and break apart under flow conditions. This creates a much faster "diffusive" conduction mode where the water molecules mainly move through the tube as individual particles, rather than as components of a larger cluster. Our results demonstrate that water models developed to describe the properties of bulk water can behave very differently in confined situations. PMID:25399183
Performance investigation of plain and finned tube evaporatively cooled heat exchangers
Ala Hasan; Kai Sirķn
The performance of two evaporatively cooled heat exchangers is investigated under similar operating conditions of air flow rates and inlet hot water temperatures. The heat exchangers are plain and plate-finned circular tube types which occupy the same volume. Spray water, which is circulated in a closed circuit, is injected onto the exposed surfaces of the tubes and fins. The contact
Influence of algae on photolysis rates of chemicals in water
Zepp, R.G.; Schlotzhauer, P.F.
Sunlight-induced algal transformations of 22 nonionic organic chemicals were studied in order to provide kinetic results and equations concerning the influence of algae on the behavior of pollutants in freshwater environments. Screening studies indicated that green and blue-green algae, at concentrations of 1-10 mg of chlorophyll a/L, accelerate photoreaction of certain polycylic aromatic hydrocarbons, organophosphorus compounds, and anilines in water. The rate of change in aniline concentration, (P), in the aniline-Chlamydomonas photoreaction can be described by the following expression: rate = A(1 + B/(P))-1. At low substrate concentrations, the reaction rate is first order with respect to both algae and substrate concentration. Methyl parathion and parathion photoreacted 390 times more rapidly when sorbed by algae than in distilled water, and aniline and m-toluidine reacted over 12000 times faster, indicating that light-induced algal transformations of certain pollutants may be significant. Other results indicated that reaction rates are unaffected by heat-killing the algae. 27 references
Isotopic composition of transpiration and rates of change in leaf water isotopologue storage in response to environmental variables.
Simonin, Kevin A; Roddy, Adam B; Link, Percy; Apodaca, Randy; Tu, Kevin P; Hu, Jia; Dawson, Todd E; Barbour, Margaret M
During daylight hours, the isotope composition of leaf water generally approximates steady-state leaf water isotope enrichment model predictions. However, until very recently there was little direct confirmation that isotopic steady-state (ISS) transpiration in fact exists. Using isotope ratio infrared spectroscopy (IRIS) and leaf gas exchange systems we evaluated the isotope composition of transpiration and the rate of change in leaf water isotopologue storage (isostorage) when leaves were exposed to variable environments. In doing so, we developed a method for controlling the absolute humidity entering the gas exchange cuvette for a wide range of concentrations without changing the isotope composition of water vapour. The measurement system allowed estimation of (18)O enrichment both at the evaporation site and for bulk leaf water, in the steady state and the non-steady state. We show that non-steady-state effects dominate the transpiration isoflux even when leaves are at physiological steady state. Our results suggest that a variable environment likely prevents ISS transpiration from being achieved and that this effect may be exacerbated by lengthy leaf water turnover times due to high leaf water contents. PMID:23647101
The influence of soil hydraulic properties on bare soil evaporation dynamics
NASA Astrophysics Data System (ADS)
Durner, Wolfgang; Iden, Sascha C.; Diamantopoulos, Efstathios
Evaporation from bare soil is an important component of the global water cycle and the energy balance of the earth's surface. Forecasting bare soil evaporation requires knowledge of physical soil properties like thermal and hydraulic conductivity, heat and water capacity, and the water-content dependency of the albedo. The focus of this contribution is to analyze the sensitivity of soil evaporation dynamics with respect to physical soil properties. A coupled numerical model of water, vapor, and heat flow in soil considering the surface energy balance and temperature effects on the transport coefficients is used for the analysis. Particular attention is devoted to the influence of soil hydraulic properties on the duration of stage-one evaporation and evaporation rates during stage-two. We illustrate the importance of an adequate parameterization of soil hydraulic properties which should account for water sorption in dry soil, water flow in completely and incompletely-filled pores, and vapor diffusion. A comparison with data from evaporation experiments in the laboratory under different atmospheric forcings provides the link between models and reality. This confrontation unveils that the use of classic parametrizations of soil hydraulic properties leads to a bias in the description of experimental data and model predictions.
A phylogenetic analysis of basal metabolism, total evaporative water loss, and life-history among foxes from desert and mesic regions.
Williams, J B; Mu±oz-Garcia, A; Ostrowski, S; Tieleman, B I
We measured basal metabolic rate (BMR) and total evaporative water loss (TEWL) of species of foxes that exist on the Arabian Peninsula, Blanford's fox (Vulpes cana) and two subspecies of Red fox (Vulpes vulpes). Combining these data with that on other canids from the literature, we searched for specialization of physiological traits among desert foxes using both conventional least squares regression and regressions based on phylogenetic independent contrasts. Further, we explored the consequences of reduced body size of foxes on life history parameters such as litter size and neonate mass. For Blanford's foxes, Red foxes from the central desert of Arabia, and Red foxes from the more mesic Asir mountains, body mass averaged 1,285 +/- 52 g, 1,967 +/- 289 g, and 3,060 +/- 482 g, respectively, whereas mean BMR, during summer, was 304.5 +/- 32.3 kJ/day, 418.0 +/- 32.4 kJ/day, and 724.1 +/- 120.2 kJ/day (+/- SD). An analysis of covariance with body mass as a covariate showed no statistical differences in BMR among foxes. Analysis of covariance indicated that Red fox from the Asir mountains had a higher TEWL than Red foxes from central Arabia or than Blanford's foxes also from the mountains. Comparisons of all species of desert and mesic foxes showed no significant differences in BMR, nor did desert foxes have a significantly lower BMR than other carnivores. TEWL of desert foxes was lower than other more mesic carnivores; deviations in TEWL ranged from -17.7% for the Fennec fox (Fennecus zerda) to -57.4% for the Kit fox (Vulpes velox). Although desert foxes have a BMR comparable to other more mesic species, it appears that desert foxes do have a smaller body mass, lowering overall energy requirements. We attribute this reduction in body size to the "resource limitation hypothesis" whereby natural selection favors smaller individuals in a resource-limited environment, especially during periods of severe food shortage. However, until common garden experiments are performed, developmental plasticity and acclimation cannot be ruled out as contributors to this pattern. PMID:14564467
Evaporation of a thin binary liquid film by forced convection into air and superheated steam
NASA Astrophysics Data System (ADS)
Nasr, Abdelaziz; Debbissi, Chokri; Nasrallah, Sassi Ben
This paper deals with a numerical analysis of the evaporation of a thin binary liquid film by forced convection inside a channel constituted by two plates. The first plate is externally insulated and wetted by a thin water ethylene glycol film while the second is dry and isothermal. The first part is concerned with the effects of inlet ambiance conditions and the liquid concentration of ethylene glycol on the distribution of the velocity, temperature, concentrations profiles and the axial variation of the evaporation rate. The second part is focused on the inversion temperature point of the evaporation of binary liquid film. Results show that the inversion temperature phenomenon for the evaporation of binary liquid mixture is observed for high liquid concentration of ethylene glycol. The present results show that in the inlet temperature range considered here, the inversion temperature does not exit for the evaporation of pure ethylene glycol.
Safety review of the DCS (Distributed Control System) controlled full scale SRAT/SME (Sludge Receipt Adjustment Tank/Slurry Mix Evaporator) for water runs
Hacker, B.A.
This memorandum addresses safety concerns of the Full Scale Sludge Receipt Adjustment Tank/Slurry Mix Evaporator (SRAT/SME) resulting from the installation of the new Distributed Control System (DCS). The present configuration of the SRAT/SME with DCS has been determined to be safe for operational testing with water. Another memorandum will be written after experience has been gained during water runs for actual operation. Previous safety evaluations and process hazard reviews for this facility have addressed normal industrial safety hazards and hazards associated with formic acid handling and operation with organics in the feed. Process operation with the new DCS controls will be very similar to the earlier operation controlled by the Modicon programmable logic controller (PLC). The interlocks for the SRAT/SME that were in the PLC have been programmed into the new DCS and will be reviewed here. 6 refs.
Dynamic analysis of evaporator characteristics
Jae-Dol Kim; Jung-In Yoon; Hag-Geun Ku
An analysis of the dynamic characteristics in an evaporator was numerically performed for control and design of the refrigeration\\u000a and air conditioning systems. The important factors, such as refrigerant flow rate, inlet enthalpy, inlet air velocity and\\u000a air temperature, are incorporated with this analysis. An evaporator is modeled for the dynamic characteristics analysis separated\\u000a into three regions which are the
Numerical investigation on the heat and mass transfer in a direct evaporative cooler
J. M. Wu; X. Huang; H. Zhang
A simplified mathematical model is developed to describe the heat and moisture transfer between water and air in a direct evaporative cooler. The mass of evaporated water is treated as a mass source of air flow, and the related latent heat of water evaporation is taken as a heat source in the energy equation. The momentum caused by water evaporation
Sensitivity of potential evaporation estimates to 100 years of climate variability
NASA Astrophysics Data System (ADS)
Bartholomeus, Ruud; Stagge, James; Tallaksen, Lena; Witte, Jan-Philip
Evaporation from the vegetated surface is the largest loss term in many, if not the most, water balance studies on earth. As a consequence, an accurate representation of evaporation fluxes is required for appropriate quantification of surface runoff, the soil moisture budget, transpiration, recharge and groundwater processes. However, despite being a key component of the water balance, evaporation figures are usually associated with large uncertainties, as this term is difficult to measure or estimate by modeling. Many modeling frameworks have used the concept of potential evaporation, often estimated for different vegetation classes by multiplying the evaporation from a reference surface ('reference evaporation') with crop specific scaling factors ('crop factors'). Though this two-step potential evaporation approach undoubtedly has practical advantages, the empirical nature of both reference evaporation methods and crop factors limits its usability in extrapolations under non-stationary climatic conditions. We quantified the sensitivity of potential evaporation estimates for different vegetation classes using the two-step approach when calibrated using a non-stationary climate. We used the past century's time series of observed climate, containing non-stationary signals of multi-decadal atmospheric oscillations, global warming, and global dimming/brightening, to evaluate the sensitivity of potential evaporation estimates to the choice and length of the calibration period. We show that using empirical coefficients outside their calibration range may lead to systematic differences between process-based and empirical reference evaporation methods, and systematic errors in estimated potential evaporation components. Our hydrological models are to varying extent regression models, which limits their general applicability, and the estimation of potential evaporation is closely linked to climate variability. With our analysis, we want to raise awareness and to provide a quantification of possible systematic errors that may be introduced in estimates of potential evaporation and in hydrological modeling studies due to straightforward application of i) the common two-step approach for potential evaporation specifically, and ii) fixed instead of time-variant model parameters in general. Quantification of errors provides a possibility to correct potential evaporation calculations and to rate them for their suitability to model climate conditions that differ significantly from the historical record, so-called no-analogue climate conditions.
Column densities resulting from shuttle sublimator/evaporator operation. [optical density of nozzle flow containing water vapor
NASA Technical Reports Server (NTRS)
Naumann, R. J.
The proposed disposal of H2O from the shuttle fuel cell operation by ejecting it in vapor form through a supersonic nozzle at the rate of 100 lb/day has been investigated from the point of view of the possible interference to astronomical experiments. If the nozzle is located at the tail and directed along the shuttle longitudinal axis, the resulting column density will be less than 10 to th 12th power molecules/sq cm at viewing angles larger than 48 deg above the longitudinal axis. The molecules in the trail will diffuse rapidly. The column density contribution from molecules expelled on the previous orbit is 1.3 x 10 to the 8th power molecules/sq cm. This contribution diminishes by the inverse square root of the number of orbits since the molecules were expelled. The molecular backscatter from atmospheric molecules is also calculated. If the plume is directed into the flight path, the column density along a perpendicular is found to be 1.5 x 10 to the 11th power molecules/sq cm. The return flux is estimated to be of the order of 10 to the 12th power molecules/sq cm/sec at the stagnation point. With reasonable care in design of experiments to protect them from the backscatter flux of water molecules, the expulsion of 100 lb/day does not appear to create an insurmountable difficulty for the shuttle experiments.
Conductive Thermal Interaction in Evaporative Cooling ProcessĀ
Kim, B. S.; Degelman, L. O.
between water and entering air for thermal comfort. This hybrid system outperforms the two-stage evaporative cooler without employing a complicated heat exchanger (indirect system), if the temperature of underground water is lower than the ambient wet...
Changes in wintertime evaporation and surface energy budget in 2007 and 2008 over an open water surface in Mississippi, U.S.A
NASA Astrophysics Data System (ADS)
Liu, H.; Zhang, Y.
Using data measured from an eddy covariance system during two winters in 2007 and 2008, we examined how synoptic weather events affect wintertime evaporation and surface energy budget over an open water surface. The measurements were conducted in the Ross Barnett reservoir (32o26ÆN, 90o02ÆW), Mississippi, U.S.A. The fetch for the eddy covariance system exceeded 2 km in all directions and the water depth is about 4 m around the flux tower. Synoptic weather events determine large-scale meteorological properties of air masses passing over water. Cold and dry air masses promote sensible and latent heat exchange between the water surface and the atmosphere. Warm and wet air masses suppress the vertical temperature and humidity gradients and dampen exchange of sensible and latent heat exchange. Therefore, day-to-day variations in sensible and latent heat fluxes are strongly influenced by synoptic weather patterns in wintertime. Analysis of meteorological data and synoptic charts indicates that there were more cold front activities in the 2007 wintertime than in the 2008 wintertime. Our results indicate that sensible and latent heat fluxes in the 2007 winter are about 27% and 36% higher than those in the 2008 wintertime, respectively. These results suggest that future potential changes in cold front activities (intensity, frequency, and duration) may lead to substantial shifts in regional energy budget and hydrological balance in the southern regions with an abundance of open water bodies (e.g., lakes, reservoirs, swamps etc).
Reaction rates and apparent toxicity of Houston Ship Channel waterĀ
Schneider, Peter William
was the Warburg Constant yolume Respirometer manometric method and the second technique was the conventional BOD dilution method using the standard BOD glass bottle. Tests were run on samples of water taken from the Houston Ship Channel. Tests showed... that the specific rate of reaction constant varies with both the depth and the location of the sample. Apparent toxic or inhibitory effects as defined in the thesis were also fo' nd to be present in many samples. The conditions prevailing , prior to the sampling...
Flexible microprocessor-based evaporation controller
F.-J. Meyer Zu Heringdorf; A. C. Belton
Electron beam evaporation sources require two power supplies, one each for the filament current and the electron acceleration. To obtain a stable deposition rate, the emission current between filament and target must remain constant. During film deposition, slight geometry changes in the evaporator cause significant rate variations, making constant readjustment of the emission current necessary. While in commercial solutions, analog
Standard test method for water in lint cotton by oven evaporation combined with volumetric Karl Fischer Titration
Technology Transfer Automated Retrieval System (TEKTRAN)
The referenced test method for total water content and water regain in lint cotton was developed by USDA scientists in New Orleans at the request of the cotton industry. The method covers the determination of the total water (free and bound) in raw and lint cotton at moisture equilibrium from con...
Soybean oil in water-borne coatings and latex film formation study by AC impedance
Nantana Jiratumnukul
Conventional coalescing agents such as butyl cellosolve, butyl carbitol, and TexanolRTM are widely use in the latex coatings industry to facilitate film formation at ambient temperature. Coalescent aids are composed of solvents with low evaporation rates. After water evaporates, coalescent aids would help soften polymer molecules and form continuous films, then gradually evaporates from the film. Coalescent aids, therefore, are
NASA Astrophysics Data System (ADS)
Sears, D. W. G.; Moore, S. R.
In order to try to quantify some of the factors determining the evaporation rate of water on Mars, we have been measuring evaporation rates under simulated martian conditions in a large planetary environmental chamber. All of our experiments have been performed at 5.25 Torr (7 mb) total pressure, but we have varied the temperature of the water surface, atmosphere and walls of the chamber (the walls we assume to be somewhat analogous to surrounding surfaces on Mars). We have also monitored the partial pressure of water vapor in the atmosphere to investigate its effect on evaporation rate. Most importantly, we have attempted to model the effect of advection - physical removal of the water vapor by wind or other forms of atmospheric motion - by (1) placing a bag of dry ice in the chamber and (2) by installing a copper cold finger with circulating methanol/dry ice slurry next to the sample and pumping as necessary to maintain 5.25 Torr. As might be expected, the situation is complicated and not readily described theoretically, but several conclusions seem to be emerging. Evaporation rates under nonadvective conditions are 1.2 mm/h and decrease only by about 30% as water vapor builds up in the atmosphere to as much as 40 vol %. Wall temperature and water surface temperature do not appear to affect evaporation rates significantly, but a 20 C increase in atmospheric temperature causes a 40% increase in evaporation rate. The evaporation rate increases by a factor of two in the presence of advection and under advective conditions is not affected significantly by changes in water, air, or wall temperature, or water vapor pressure. These results suggest that atmospheric motion may be the dominant factor in determining water evaporation on Mars.
An Automatic Sensor-Controlled Evaporation and Rainfall Measurement System
Turkay Onacak; Mehmet Tekin Yurur
For the efficient management of water, meteorological and hydrological services need to know how much water evaporates from natural lakes and reservoirs during particularly hot summer months. Following the technical requirements of the World Meteorological Organization on use of an evaporation pan for this purpose, we improved the use of the classical evaporation pan to measure at any time, with
Surface Geometry and Stomatal Conductance Effects on Evaporation From Aquatic Macrophytes
NASA Astrophysics Data System (ADS)
Anderson, Michael G.; Idso, Sherwood B.
Evaporative water loss rates of several floating and emergent aquatic macrophytes were studied over a 4-year period through comparison of daily evaporative water losses from similar-sized vegetated (E) and open water (E0) surfaces. Two species with planate floating leaves (water fern and water lily) yielded E/E0 values of 0.90 for one and four growing seasons, respectively, and displayed stomatal regulation of potential evaporation. Water hyacinths grown in ponds with different diameters exhibited E/E0 ratios which decreased with increasing pond diameter for both short (0.06-0.36 m) and tall (0.63-0.81 m) plants, producing high linear correlations with amount of peripheral vegetative surface area. The latter relationships suggested an E/E0 value less than unity for a relatively extensive canopy of short water hyacinths and a value of the order of 1.4 for a tall canopy possessing similar two-dimensional surface area characteristics. The latter results were also demonstrated in a separate study utilizing polyurethane foam to insulate the peripheral exposure of tall water hyacinth canopies from advective energy. Finally, simultaneous stomatal conductance and daily E/E0 measurements on cattail and water hyacinth canopies with identical tank diameters indicated that although the mean stomatal conductance of the peripheral exposure of the cattail canopy was 72% less than that of the water hyacinth canopy, its total evaporative water loss was nearly equivalent, due to its greater height. Reducing the surface area of the peripheral cattail exposure by the fractional amount suggested by the stomatal conductance measurements harmonized its surface geometry-evaporation relationship with that of the water hyacinth canopy and once again demonstrated the reality of stomatal control of potential evaporation.
Evaporation from a sphagnum moss surface
Nichols, D.S. and Brown, J.M., 1980. Evaporation from a sphagnum moss surface. J. Hydrol., 48: 289--302. Peat cores, 45cm in diameter, were collected from a sphagnum bog in northern Minnesota, and used to measure the effects of different temperatures and water levels on evaporation from a sphagnum moss surface in a growth chamber. Under all conditions, evaporation from the moss
Given that water is the sine qua non of life, it is intriguing that animals can live in deserts, environments with little
Williams, Jos. B.
mass-specific rates of metabolism, which drive respiratory water loss, further exacerbating problems that can minimize rates of evaporative water loss under normal circumstances. But when Ta values exceed selection to prevent excessive water loss, or to ensure sufficient evaporative losses to maintain body
Nanofluid Drop Evaporation: Experiment, Theory, and Modeling
NASA Astrophysics Data System (ADS)
Gerken, William James
Nanofluids, stable colloidal suspensions of nanoparticles in a base fluid, have potential applications in the heat transfer, combustion and propulsion, manufacturing, and medical fields. Experiments were conducted to determine the evaporation rate of room temperature, millimeter-sized pendant drops of ethanol laden with varying amounts (0-3% by weight) of 40-60 nm aluminum nanoparticles (nAl). Time-resolved high-resolution drop images were collected for the determination of early-time evaporation rate (D2/D 02 > 0.75), shown to exhibit D-square law behavior, and surface tension. Results show an asymptotic decrease in pendant drop evaporation rate with increasing nAl loading. The evaporation rate decreases by approximately 15% at around 1% to 3% nAl loading relative to the evaporation rate of pure ethanol. Surface tension was observed to be unaffected by nAl loading up to 3% by weight. A model was developed to describe the evaporation of the nanofluid pendant drops based on D-square law analysis for the gas domain and a description of the reduction in liquid fraction available for evaporation due to nanoparticle agglomerate packing near the evaporating drop surface. Model predictions are in relatively good agreement with experiment, within a few percent of measured nanofluid pendant drop evaporation rate. The evaporation of pinned nanofluid sessile drops was also considered via modeling. It was found that the same mechanism for nanofluid evaporation rate reduction used to explain pendant drops could be used for sessile drops. That mechanism is a reduction in evaporation rate due to a reduction in available ethanol for evaporation at the drop surface caused by the packing of nanoparticle agglomerates near the drop surface. Comparisons of the present modeling predictions with sessile drop evaporation rate measurements reported for nAl/ethanol nanofluids by Sefiane and Bennacer [11] are in fairly good agreement. Portions of this abstract previously appeared as: W. J. Gerken, A. V. Thomas, N. Koratkar and M. A. Oehlschlaeger, Int. J. Heat Mass Transfer, vol. 74, no. 1, pp. 263-268, July 2014. W. J. Gerken, M. A. Oehlschlaeger, "Nanofluid Pendant Droplet Evaporation", in Proceedings of the ASME 2013 Summer Heat Transfer Conference, Minneapolis, MN, 2013, pp. V001T03A018.
Experimental studies and numerical simulation of evaporative cooling of air with a water sprayŚI. Horizontal parallel flow
S. S. Kachhwaha; P. L. Dhar; S. R. Kale
Hollow cone water sprays are used in many humidifying, cooling and scrubbing applications. For predicting the heat and mass transfer in these spray-air flow systems a two-dimensional numerical model simulating the conservation of mass, momentum and energy of air, and water, were developed. Model inputs include drop size distribution and velocities at nozzle spray angle, inlet air DBT and humidity
The correlation between surface temperature and subsurface velocity during evaporative convection
Saylor, John R.
The correlation between surface temperature and subsurface velocity during evaporative convection J tempera- ture and subsurface velocity is presented for water un- dergoing evaporative convection of underwater objects via infrared imaging are discussed. 1 Introduction Evaporative convection is the natural
75 FR 82066 - Change in Discount Rate for Water Resources Planning
Federal Register 2010, 2011, 2012, 2013, 2014
...discount rate for Federal water resources planning for fiscal...CONTACT: Brooke Miller-Levy, Water and Environmental Resources Division, Denver, Colorado 80225; telephone: 303-445-2889...and evaluation of plans for water and related land...
75 FR 8106 - Change in Discount Rate for Water Resources Planning
Federal Register 2010, 2011, 2012, 2013, 2014
...discount rate for Federal water resources planning for fiscal...CONTACT: Brooke Miller-Levy, Water and Environmental Resources Office, Denver, Colorado 80225; telephone: 303...and evaluation of plans for water and related land...
78 FR 67393 - Change in Discount Rate for Water Resources Planning
Federal Register 2010, 2011, 2012, 2013, 2014
...discount rate for Federal water resources planning for fiscal...CONTACT: Michelle Kelly, Water and Environmental Resources Division, Denver, Colorado 80225; telephone: 303-445-2888...and evaluation of plans for water and related land...
78 FR 16706 - Change in Discount Rate for Water Resources Planning
Federal Register 2010, 2011, 2012, 2013, 2014
...discount rate for Federal water resources planning for fiscal...CONTACT: Michelle Kelly, Water and Environmental Resources Division, Denver, Colorado 80225; telephone: 303-445-2888...and evaluation of plans for water and related land...
Water and acrylamide monomer transfer rates from a settling basin to groundwaters
Boyer, Edmond
11356-014-3106-2 #12;2 Key word: Acrylamide; Water transfer rate; Clogged layer; Groundwater 11 Water and acrylamide monomer transfer rates from a settling basin to groundwaters Stķphane Binet that the water and the Acrylamide transfer rate are not controlled by the spreading of the clogged layer until
76 FR 73674 - Change in Discount Rate for Water Resources Planning
Federal Register 2010, 2011, 2012, 2013, 2014
The Water Resources Planning Act of 1965 and the Water Resources Development Act of 1974 require an annual determination of a discount rate for Federal water resources planning. The discount rate for Federal water resources planning for fiscal year 2012 is 4 percent. Discounting is to be used to convert future monetary values to present...
Mathematic models of water application for a variable rate irrigating hill-seeder
Technology Transfer Automated Retrieval System (TEKTRAN)
A variable rate irrigating hill-seeder can adjust water application automatically according to the difference in soil moisture content in the field to alleviate drought and save water. Two key problems to realize variable rate water application are how to determine the right amount of water for the ...
Drop evaporation on superhydrophobic PTFE surfaces driven by contact line dynamics.
Ramos, S M M; Dias, J F; Canut, B
In the present study, we experimentally study the evaporation modes and kinetics of sessile drops of water on highly hydrophobic surfaces (contact angle ?160░), heated to temperatures ranging between 40░ and 70 ░C. These surfaces were initially constructed by means of controlled tailoring of polytetrafluoroethylene (PTFE) substrates. The evaporation of droplets was observed to occur in three distinct phases, which were the same for the different substrate temperatures. The drops started to evaporate in the constant contact radius (CCR) mode, then switched to a more complex mode characterized by a set of stick-slip events accompanied by a decrease in contact angle, and finally shifted to a mixed mode in which the contact radius and contact angle decreased simultaneously until the drops had completely evaporated. It is shown that in the case of superhydrophobic surfaces, the energy barriers (per unit length) associated with the stick-slip motion of a drop ranges in the nJ m(-1) scale. Furthermore, analysis of the evaporation rates, determined from experimental data show that, even in the CCR mode, a linear relationship between V(2/3) and the evaporation time is verified. The values of the evaporation rate constants are found to be higher in the pinned contact line regime (the CCR mode) than in the moving contact line regime. This behavior is attributed to the drop's higher surface to volume ratio in the CCR mode. PMID:25460699
Odors from evaporation of acidified pig urine
H. C. Willers; P. J. Hobbs; N. W. M. Ogink
In the Dutch Hercules project feces and urine from pigs are collected separately underneath the slatted floor in a pig house and treated in two processes. Feces are composted and urine is concentrated by water evaporation in a packed bed. Exhaust air from the pig house is used for the evaporation in a packed bed scrubber. Before entering the scrubber,
DWPF Recycle Evaporator Shielded Cells Testing
T. L. Fellinger; D. T. Herman; M. E Stone
Testing was performed to determine the feasibility and processing characteristics of evaporation of actual Defense Waste Processing Facility (DWPF) recycle material. Samples of the Off Gas Condensate Tank (OGCT) and Slurry Mix Evaporator Condensate Tank (SMECT) were transferred from DWPF to the Savannah River National Lab (SRNL) Shielded Cells and blended with De-Ionized (DI) water and a small amount of
Membrane evaporator/sublimator investigation
NASA Technical Reports Server (NTRS)
Elam, J.; Ruder, J.; Strumpf, H.
Data are presented on a new evaporator/sublimator concept using a hollow fiber membrane unit with a high permeability to liquid water. The aim of the program was to obtain a more reliable, lightweight and simpler Extra Vehicular Life Support System (EVLSS) cooling concept than is currently being used.
Estimation of water turnover rates of captive West Indian manatees (Trichechus manatus) held in fresh and salt water
NASA Technical Reports Server (NTRS)
Ortiz, R. M.; Worthy, G. A.; Byers, F. M.
The ability of West Indian manatees (Trichechus manatus) to move between fresh and salt water raises the question of whether manatees drink salt water. Water turnover rates were estimated in captive West Indian manatees using the deuterium oxide dilution technique. Rates were quantified in animals using four experimental treatments: (1) held in fresh water and fed lettuce (N=4), (2) held in salt water and fed lettuce (N=2), (3) acutely exposed to salt water and fed lettuce (N=4), and (4) chronically exposed to salt water with limited access to fresh water and fed sea grass (N=5). Animals held in fresh water had the highest turnover rates (145+/-12 ml kg-1 day-1) (mean +/- s.e.m.). Animals acutely exposed to salt water decreased their turnover rate significantly when moved into salt water (from 124+/-15 to 65+/-15 ml kg-1 day-1) and subsequently increased their turnover rate upon re-entry to fresh water (146+/-19 ml kg-1 day-1). Manatees chronically exposed to salt water had significantly lower turnover rates (21+/-3 ml kg-1 day-1) compared with animals held in salt water and fed lettuce (45+/-3 ml kg-1 day-1). Manatees chronically exposed to salt water and fed sea grass had very low turnover rates compared with manatees held in salt water and fed lettuce, which is consistent with a lack of mariposia. Manatees in fresh water drank large volumes of water, which may make them susceptible to hyponatremia if access to a source of Na+ is not provided.
Seasonal and Interannual Variations of Evaporation and their Relations with Precipitation, Net Radiation, and Net Carbon Accumulation for the Gediz Basin Area
NASA Technical Reports Server (NTRS)
Choudhury, Bhaskar J.
A model combining the rate of carbon assimilation with water and energy balance equations has been run using satellite and ancillary data for a period of 60 months (January 1986 to December 1990). Calculations for the Gediz basin area give mean annual evaporation as 395 mm, which is composed of 45% transpiration, 42% soil evaporation and 13% interception. The coefficient of interannual variation of evaporation is found to be 6%, while that for precipitation and net radiation are, respectively, 16% and 2%, illustrating that net radiation has an important effect in modulating interannual variation of evaporation. The mean annual water use efficiency (i.e., the ratio of net carbon accumulation and total evaporation) is ca. 1 g/sq m/mm, and has a coefficient of interannual variation of 5%. A comparison of the mean water use efficiency with field observations suggests that evaporation over the area is utilized well for biomass production. The reference crop evaporation for irrigated areas has annual mean and coefficient of variation as, respectively, 1176 mm and 3%. The total evaporation during three summer months of peak evaporation (June-August) is estimated to be about 575 mm for irrigated crops like maize and cotton. Seasonal variations of the fluxes are presented.
Comment on "A model for soil surface evaporation based on Campbell's retention curve" by G. Zarei, M. Homaee, A.M. Liaghat, A.H. Hoorfar
NASA Astrophysics Data System (ADS)
Sadeghi, Morteza
Zarei et al. (2010) developed an analytical solution to soil evaporation under conditions of a falling (or fluctuating) water table (WT). They described the soil evaporation rate as a function of water table depth drawdown and soil physical properties (e.g. Campbell's retention model parameters). I want to demonstrate how the basic assumptions used in the derivation of this solution are not valid and thus the analytical model is in need of correction.
Effects of drinking water temperature on water consumption, respiration rates, and body temperatures of lactating Holstein cows in summerĀ
Lanham, Jeffrey Kent
EFFECTS OF DRINKING WATER TEMPERATURE ON WATER CONSUMPTION, RESPIRATION RATES, AND BODY TEMPERATURES OF LACTATING HOLSTEIN COWS IN SUMMER A Thesis by JEFFREY KENT LANHAM Submitted to the Graduate College of Texas A&M University in partial... fulfillment of the requirements for the degree of MASTER OF SCIENCE May 1985 Major Subject: Nutrition EFFECTS OF DRINKING WATER TEMPERATURE ON WATER CONSUMPTION, RESPIRATION RATES, AND BODY TEMPERATURES OF LACTATING HOLSTEIN COWS IN SUMMER A Thesis...
National and Regional Water and Wastewater Rates For Use inCost-Benefit Models and Evaluations of Water Efficiency Programs
Fisher, Diane C.; Whitehead, Camilla Dunham; Melody, Moya
Calculating the benefits and costs of water conservation orefficiency programs requires knowing the marginal cost of the water andwastewater saved by those programs. Developing an accurate picture of thepotential cost savings from water conservation requires knowing the costof the last few units of water consumed or wastewater released, becausethose are the units that would be saved by increased water efficiency.This report describes the data we obtained on water and wastewater ratesand costs, data gaps we identified, and other issues related to using thedata to estimate the cost savings that might accrue from waterconservation programs. We identified three water and wastewater ratesources. Of these, we recommend using Raftelis Financial Corporation(RFC) because it: a) has the most comprehensive national coverage; and b)provides greatest detail on rates to calculate marginal rates. The figurebelow shows the regional variation in water rates for a range ofconsumption blocks. Figure 1A Marginal Rates of Water Blocks by Regionfrom RFC 2004Water and wastewater rates are rising faster than the rateof inflation. For example, from 1996 to 2004 the average water rateincreased 39.5 percent, average wastewater rate increased 37.8 percent,the CPI (All Urban) increased 20.1 percent, and the CPI (Water andSewerage Maintenance) increased 31.1 percent. On average, annualincreases were 4.3 percent for water and 4.1 percent for wastewater,compared to 2.3 percent for the All Urban CPI and 3.7 percent for the CPIfor water and sewerage maintenance. If trends in rates for water andwastewater rates continue, water-efficient products will become morevaluable and more cost-effective.
Chemical evolution of multicomponent aerosol particles during evaporation
NASA Astrophysics Data System (ADS)
Zardini, Alessandro; Riipinen, Ilona; Pagels, Joakim; Eriksson, Axel; Worsnop, Douglas; Switieckli, Erik; Kulmala, Markku; Bilde, Merete
Atmospheric aerosol particles have an important but not well quantified effect on climate and human health. Despite the efforts made in the last decades, the formation and evolution of aerosol particles in the atmosphere is still not fully understood. The uncertainty is partly due to the complex chemical composition of the particles which comprise inorganic and organic compounds. Many organics (like dicarboxylic acids) can be present both in the gas and in the condensed phase due to their low vapor pressure. Clearly, an understanding of this partition is crucial to address any other issue in atmospheric physics and chemistry. Moreover, many organics are water soluble, and their influence on the properties of aqueous solution droplets is still poorly characterized. The solid and sub-cooled liquid state vapor pressures of some organic compounds have been previously determined by measuring the evaporation rate of single-compound crystals [1-3] or binary aqueous droplets [4-6]. In this work, we deploy the HTDMA technique (Hygroscopicity Tandem Differential Mobility Analyzer) coupled with a 3.5m laminar flow-tube and an Aerosol Mass Spectrometer (AMS) for determining the chemical evolution during evaporation of ternary droplets made of one dicarboxylic acid (succinic acid, commonly found in atmospheric samples) and one inorganic compound (sodium chloride or ammonium sulfate) in different mixing ratios, in equilibrium with water vapor at a fixed relative humidity. In addition, we investigate the evaporation of multicomponent droplets and crystals made of three organic species (dicarboxylic acids and sugars), of which one or two are semi-volatile. 1. Bilde M. and Pandis, S.N.: Evaporation Rates and Vapor Pressures of Individual Aerosol Species Formed in the Atmospheric Oxidation of alpha- and beta-Pinene. Environmental Science and Technology, 35, 2001. 2. Bilde M., et al.: Even-Odd Alternation of Evaporation Rates and Vapor Pressures of C3-C9 Dicarboxylic Acid Aerosols, Environmental. Science and Technology, 37, 2003. 5. Koponen I.K., et al.: Thermodynamic properties of malonic, succinic, and glutaric acids: Evaporation rates and saturation vapor pressures. Environmental Science and Technology, 41, 2007. 4. Zardini A.A., et al.: White light Mie resonance spectroscopy used to measure very low vapor pressures of substances in aqueous solution aerosol particles. Optics Express, 14, 2006. 3. Zardini A.A. and Krieger, U.K.: Evaporation kinetics of a non-spherical, levitated aerosol particle using optical resonance spectroscopy for precision sizing. Optics Express, 17, 2009. 6. Riipinen, I., et al.: Adipic and Malonic Acid Aqueous Solutions: Surface Tensions and Saturation Vapor Pressures, J. Phys. Chem., 111, 2007.
Evaporation of petroleum products from contaminated soils
Seon-Hong Kang; Charles S. Oulman
Bioremediation can remove petroleum products from soil that has been contaminated by leaking underground storage tanks, but abiotic processes such as evaporation can contribute significantly to the overall removal process. The mathematical model described in this paper was developed to predict the evaporation rate of volatile liquids from petroleum-contaminated sand. The model is based on simple concepts relating to molecular
The effect the pressure drop of regular packings has on the return water evaporation cooling efficiency in cooling towers
NASA Astrophysics Data System (ADS)
Pushnov, A. S.
Results obtained from a qualitative analysis aimed at determining the effect the pressure drop coefficient of regular film, droplet-film, and droplet-type packings has on the efficiency of the return water cooling process in cooling towers are presented.
Hot, dry, & windy: The impacts of strongly advective conditions on measurements of evaporative water loss from irrigated croplands
Technology Transfer Automated Retrieval System (TEKTRAN)
As the demand for water has grown in recent years, balancing the needs of urban, rural, and agricultural communities has become formidable task, particularly in the western United States where more than 70% of the freshwater supply is used for irrigated agriculture. To ensure there is sufficient wat...
Modeling and experimental validation of a greenhouse with evaporative cooling by moving water film over external shade cloth
M. K. Ghosal; G. N. Tiwari; N. S. L. Srivastava
A mathematical model through flowing water film on shade cloth, stretched over the roofs and south wall of an even span greenhouse has been developed to study the effectiveness of cooling in greenhouse. The model was validated experimentally for the climate of Delhi during summer period, out of the data collected in the experiments conducted under three conditions, i.e. shaded
Preciptation, Evaporation, and Transpiration Activity
NSDL National Science Digital Library
Amy Townsend-Small
The students must use crayons or colored pencils to create maps of global precipitation and evaporation rates. One worksheet is provided to each group of students. Then a representative from each group explains their map to the rest of the class, and the instructor shows a similar map from NOAA or NASA.
Performance investigation of plain circular and oval tube evaporatively cooled heat exchangers
Ala Hasan; Kai Sirķn
The performance of two evaporatively cooled heat exchangers is analysed, one has plain circular tubes while the other one has plain oval tubes. Both are investigated under similar operating conditions in relation to airflow rates and inlet hot water temperatures. The circular tube is 10 mm o.d., and the oval tube (axes ratio 3.085) is formed from an 18 mm
Contribution of impervious surfaces to urban evaporation
NASA Astrophysics Data System (ADS)
Ramamurthy, P.; Bou-Zeid, E.
Observational data and the Princeton urban canopy model, with its detailed representation of urban heterogeneity and hydrological processes, are combined to study evaporation and turbulent water vapor transport over urban areas. The analyses focus on periods before and after precipitation events, at two sites in the Northeastern United States. Our results indicate that while evaporation from concrete pavements, building rooftops, and asphalt surfaces is discontinuous and intermittent, overall these surfaces accounted for nearly 18% of total latent heat fluxes (LE) during a relatively wet 10 day period. More importantly, these evaporative fluxes have a significant impact on the urban surface energy balance, particularly during the 48 h following a rain event when impervious evaporation is the highest. Thus, their accurate representation in urban models is critical. Impervious evaporation after rainfall is also shown to correlate the sources of heat and water at the earth surface, resulting in a conditional scalar transport similarity over urban terrain following rain events.
Simultaneous ion and neutral evaporation in aqueous nanodrops: experiment, theory, and molecular dynamics simulations.
Higashi, Hidenori; Tokumi, Takuya; Hogan, Christopher J; Suda, Hiroshi; Seto, Takafumi; Otani, Yoshio
We use a combination of tandem ion mobility spectrometry (IMS-IMS, with differential mobility analyzers), molecular dynamics (MD) simulations, and analytical models to examine both neutral solvent (H2O) and ion (solvated Na(+)) evaporation from aqueous sodium chloride nanodrops. For experiments, nanodrops were produced via electrospray ionization (ESI) of an aqueous sodium chloride solution. Two nanodrops were examined in MD simulations: a 2500 water molecule nanodrop with 68 Na(+) and 60 Cl(-) ions (an initial net charge of z = +8), and (2) a 1000 water molecule nanodrop with 65 Na(+) and 60 Cl(-) ions (an initial net charge of z = +5). Specifically, we used MD simulations to examine the validity of a model for the neutral evaporation rate incorporating both the Kelvin (surface curvature) and Thomson (electrostatic) influences, while both MD simulations and experimental measurements were compared to predictions of the ion evaporation rate equation of Labowsky et al. [Anal. Chim. Acta, 2000, 406, 105-118]. Within a single fit parameter, we find excellent agreement between simulated and modeled neutral evaporation rates for nanodrops with solute volume fractions below 0.30. Similarly, MD simulation inferred ion evaporation rates are in excellent agreement with predictions based on the Labowsky et al. equation. Measurements of the sizes and charge states of ESI generated NaCl clusters suggest that the charge states of these clusters are governed by ion evaporation, however, ion evaporation appears to have occurred with lower activation energies in experiments than was anticipated based on analytical calculations as well as MD simulations. Several possible reasons for this discrepancy are discussed. PMID:26013735
Influence of Oil on Refrigerant Evaporator Performance
NASA Astrophysics Data System (ADS)
Jong-Soo, Kim; Nagata, Katsuya; Katsuta, Masafumi; Tomosugi, Hiroyuki; Kikuchi, Kouichiro; Horichi, Toshiaki
To explore the quantitative effect of the lubrication oil on the thermal and hydraulic evaporator performance, the detailed structure of two-phase refrigerant (R11) and lubrication oil (Suniso 5GS) flow has been investigated. Experiment has been performed using a transparent tube 20mm in inner diameter and 2600mm in total length as main test section, which was heated by surrounding hot water bath. This water bath also functioned as the visual observation section of the transition of two-phase flow pattern. Oil mass concentration was controlled initially, and circulated into the system. The void fraction at the main test section was measured by direct volume measurement using so-called "Quick Closing Valve" method. Since the effect of oil on the transition of two-phase flow pattern is emphasized at the low flow rate, operation was made at relatively low mass velocity, 50 and 100 kg/m2Ęs, five different oil concentrations were taken. Throughout the experiment, the evaporation pressure was kept at 105 kPa. In general, when contamination of the lubrication oil happened, the void fraction was decreasing due to the change of viscosity and surface tension and the occurence of the foaming. To correlate the void fraction as function of quality, Zivi's expression was modified to include the effect of oil concentration. The agreement between the data and this proposed correlation was favorable. Finally, to take into account the effect of lubrication oil, the new flow pattern diagram was proposed.
Application Research of Evaporative Cooling in the Waste Heat Recovery
Wu Zhijiang; Wang Nan; Zhu Gongsheng
Evaporative condenser is one kind of high-efficient and energy-water saving heat exchange equipment, which has been widely applied in many engineering fields. The theory and product characteristic of evaporative condenser is introduced in this paper. A new type of the application of evaporative condenser in waste heat recovery is presented. The effect of energy saving is obvious, wide application prospect
Evaporative climate changes at Bet Dagan, Israel, 1964¢1998
S. Cohen; A. Ianetz; G. Stanhill
Analysis of evaporation measurements made between 1964 and 1998 at Bet Dagan in IsraelÆs central coastal plain shows a small but statistically significant increase in screened Class A pan evaporation, mainly in the dry, summer half of the year. No changes were found in the total open water evaporation or reference crop evapotranspiraton estimated with PenmanÆs combined heat balance and
Wilmarth, W.R.
Operation of the 242-16H High Level Waste Evaporator proves crucial to liquid waste management in the H-Area Tank Farm. Recent operational history of the Evaporator showed significant solid formation in secondary lines and in the evaporator pot. Additional samples remain necessary to ensure material identity in the evaporator pot. Analysis of these future samples will provide actinide partitioning information and dissolution characteristics of the solid material from the pot to ensure safe chemical cleaning.
SOIL WATER SENSING - FOCUS on VARIABLE RATE IRRIGATION
Technology Transfer Automated Retrieval System (TEKTRAN)
Irrigation scheduling using soil water sensors is an exercise in maintaining the water content of the crop root zone soil above a lower limit defined by the management allowed depletion (MAD) for that soil and crop, but not so wet that too much water is lost to deep percolation. The management allow...
Experimental investigation of the stability and evaporation of sulfate and chloride brines on Mars
NASA Astrophysics Data System (ADS)
Altheide, Travis; Chevrier, Vincent; Nicholson, Christine; Denson, Jackie
We have investigated the evaporation of concentrated magnesium and ferrous sulfate, and magnesium and ferric chloride brines as possible sources for liquid water on the surface of Mars, with special emphasis on the effect of freezing and crystallization of solutions. Experimental evaporation rates range from 0.04 mm h - 1 for 25 wt.% MgSO 4 at 271.9 K, to 0.19 mm h - 1 for 18 wt.% FeSO 4 at 270.5 K. For chloride solutions, evaporation rates range from 0.09 mm h - 1 for 40 wt.% FeCl 3 at 261.34 K, to 0.43 mm h - 1 for 20 wt.% MgCl 2 at 267.2 K. These evaporation rates are significantly lower than for pure water, i.e. 1.35 mm h - 1 at 273 K. Using the Pitzer ion interaction model, we show that the decrease in evaporation rate is due to lower water activity in concentrated solutions, down to 0.91 for saturated MgSO 4 and 0.97 for saturated FeSO 4, at their eutectic temperatures. For saturated MgCl 2 and FeCl 3, the calculated water activities are 0.57 and 0.60 at their respective eutectic temperatures. In addition, we show that the water activity drops significantly when salts are crystallizing, down to 0.17 and 0.21 for MgSO 4 and FeSO 4, respectively. Our experiments and calculations show that the water activity and evaporation rate are dependent on the hydration state of the precipitating salt, which is in turn controlled by the temperature and the relative humidity. Low-hydration state salts precipitate at lower humidity, with lower evaporation rates. Our study suggests that martian brines could remain stable for longer periods of time, at low temperatures and low humidity, than previously thought. Brines formed from these salts would be a more stable source of water on Mars, thus beneficial for any putative martian life, past and/or present.
The importance of respiratory patterns and the physical properties of cuticular lipids to insect water balance were investigated in natural populations of the grasshopper Melanoplus sanguinipes. I specifically test the hypotheses that patterns of discontinuous ventilation affect water loss and that increased amounts and melting points of cuticular lipid reduce water loss. Using flow-through respirometry, rates of water loss and
Author's personal copy How large is the subducted water flux? New constraints on mantle regassing rates
Mukhopadhyay, Sujoy
cycling and the return flux of water to the deep Earth. Estimates of magma production rates and water Earth water cycle. The simulation is con- strained by reconstructions of Phanerozoic sea level change (Fig. 1). A quantitative assessment of the long-term water cycle is critical to our understanding
Isotopic Compositions of Evaporative Fluxes
NASA Astrophysics Data System (ADS)
Feng, X.; Lauder, A. M.; Kopec, B. G.; Dade, W. B.; Virginia, R. A.; Posmentier, E. S.
The isotopic fluxes of evaporation from a water surface are typically computed using a one-dimensional model, originally conceptualized by Craig and Gordon (1965) and further developed and adapted to different natural settings (such as transpiration, open surface evaporation, etc.) by various investigators. These models have two distinguishing characteristics. First, there exists a laminar layer where molecular diffusion away from the water-air interface causes kinetic isotopic fractionation. The magnitude of this fractionation is controlled by the diffusion/transport coefficient of each vapor isotopologue in air and their concentration gradients, the latter being controlled by relative humidity, isotopic ratios of ambient air, and turbulent conditions (such as wind and surface roughness). Second, the horizontal variations are ignored. In particular, the effect of horizontal advection on isotopic variations in the ambient air is not considered. The research reported here addresses the effects of relinquishing the simplifying assumptions in both of these areas. We developed a model, in which the simplification of a purely laminar layer is dropped. Instead, we express the vertical transport coefficient as the sum of the molecular diffusivity, that differs for each water isotopologue, and the turbulent diffusivity that increases linearly with height but does not vary among water isotopologues. With this model, the kinetic isotopic effect reduces with height in the vicinity of the water surface, and the net isotopic fractionation through the boundary layer can be integrated. The advantage of this conceptualization is that the magnitude of kinetic isotopic fractionation can be assessed directly with changing environmental conditions, such as humidity and wind speed, rather than approximated by discontinuous empirical functions of the environmental conditions, as in the conventional models mentioned above. To address the effect of lateral heterogeneity, we expanded the model to 2-D and incorporated horizontal advection. The effect of advection was tested and modeled with data collected at several lakes located near Kangerlussuaq, Greenland. As predicted by the model, we observed both vertical as well as horizontal gradients as relatively dry and isotopically depleted air advects over a lake surface. Compared to the standard 1-D model, the 2-D model produced more realistic but significantly depleted isotopic fluxes of evaporation within 500 meters from the upwind shore. This is because of the time and/or distance needed for the dry air to equilibrate with vapor evaporated from the lake. The results suggest that the 1-D model is not adequate for simulating evaporation when the fetch over the water surface is small. This result is important for lake hydrological studies and for understanding and modeling isotopic fluxes of evaporation from sea ice leads that are of limited fetch.
Factors Controlling Water Volumes and Release Rates in Martian Outflow Channels
NASA Technical Reports Server (NTRS)
Wilson, L.; Head, J. W.; Leask, H. J.; Ghatan, G.; Mitchell, K. L.
We discuss estimates of water fluxes on Mars and suggest that many are overestimates. Even so, we can only explain very high martian outflow rates by either unusually permeable aquifer systems or sudden release of shallow concentrations of water.
Assessment of the Multi-Fluid Evaporator Technology
NASA Astrophysics Data System (ADS)
Quinn, Gregory; O'Connor, Edward
Hamilton Sundstrand has developed a scalable evaporative heat rejection system called the Multi-Fluid Evaporator (MFE). It was designed to support the Orion Crew Module and to support future Constellation missions. The MFE would be used as a heat sink from Earth sea level conditions to the vacuum of space. The current shuttle configuration utilizes an ammonia boiler and water based flash evaporator system to achieve cooling at all altitudes. This system combines both functions into a single compact package with improved freeze-up protection. The heat exchanger core is designed so that radial flow of the evaporant provides increasing surface area to keep the back pressure low. The multiple layer construction of the core allows for efficient scale up to the desired heat rejection rate. A full-scale system uses multiple core sections that, combined with a novel control scheme, manage the risk of freezing the heat exchanger cores. A single-core MFE engineering development unit (EDU) was built in 2006, followed by a full scale, four-core prototype in 2007. The EDU underwent extensive thermal testing while the prototype was being built. Lessons learned from the EDU were incorporated into the prototype and proven out in check-out testing. The EDU and prototype testing proved out the MFE's ability to passively control back-pressure, avoid unwanted icing, tolerate icing if it should occur, provide a three-to-one turn down ratio in heat load and scale up efficiently. Some issues with these first designs of the MFE have limited its ability to reject heat without liquid evaporant carry-over. However, they are due to the implementation of the design rather than the fundamentals of the technology. This paper discusses the background, development and present state of the Multi-Fluid Evaporator technology and concludes with efforts underway to advance the state-of-the-art.
Pan Evaporation, Relative Humidity and Daily Minimum/Maximum Temperatures
NSDL National Science Digital Library
This activity will show students how to determine rate of evaporation and the atmospheric factors that can affect this rate. Laboratory equipment needed for this investigation includes: a digital balance or triple beam balance, metric ruler in millimeter graduations, level, 2 metal pans, barograph (or barometer), hydrograph (or hygrometer), thermograph (or thermometer), anemometer, rain gauges and quart jar. Teacher background information, assessment suggestions, and a scoring rubric are included. This is Activity 1, in the learning module, Water: Here, There and Everywhere, part of the lesson series, The Potential Consequences of Climate Variability and Change.
Evaporator film coefficients of grooved heat pipes
NASA Technical Reports Server (NTRS)
Kamotani, Y.
The heat transfer rate in the meniscus attachment region of a grooved heat pipe evaporator is studied theoretically. The analysis shows that the evaporation takes place mainly in the region where the liquid changes its shape sharply. However, comparisons with available heat transfer data indicate that the heat transfer rate in the meniscus varying region is substantially reduced probably due to groove wall surface roughness.
Crop growth and soil water spatial variability under a variable rate center pivot
Technology Transfer Automated Retrieval System (TEKTRAN)
Precision agriculture has mostly emphasized variable-rate nutrients, seeding, and pesticide applications. More recently, variable-rate irrigation equipment has been developed to explore the potential for managing irrigation spatially. Managing irrigation spatially can enhance water conservation and ...
Evaluation of a two-stage evaporation approximation for contrasting vegetation cover
NASA Astrophysics Data System (ADS)
Boulet, G.; Chehbouni, A.; Braud, I.; Duchemin, B.; Lakhal, A.
For a regional assessment of water needs and consumption in semiarid agricultural zones, one needs robust and simple tools that provide space-time estimates of evaporation losses. Most operational evaporation estimates rely on semiempirical relationships that are not generally applicable. Several authors have proposed physically based simple expressions to model the "energy-limited" (stage-one) and the "supply-limited" (stage-two) evaporation rates during a dry down. They use the time compression approximation (TCA) to relate stage-one and stage-two drying. Two asymptotic approximations of the TCA corresponding to the diffusion-dominated and the drainage-dominated flows have been proposed in the literature. In this study a full analytical solution of the TCA is presented. The derived "supply-limited" evaporation rate is evaluated for a wide range of soil conditions and vegetation cover against a physically based complex soil-vegetation-atmosphere transfer model, the Simple Soil-Plant-Atmosphere Transfer scheme (SiSPAT). SiSPAT solves the differential equations of water flow in a vertical soil column and computes estimates of soil evaporation and transpiration. SiSPAT is used to evaluate the performance of the full solution as well as the two existing asymptotic approximations for the case of sparse to dense vegetation in a semiarid environment. The full analytical solution gives accurate predictions of first- to second-stage evaporation time series for the bare soil and vegetated cover conditions with a leaf area index of 3 or higher. The results of the full solution are closer to the evaporation rate time series simulated by SISPAT than the asymptotic approximations.
Does Water Content or Flow Rate Control Colloid Transport in Unsaturated Porous Media?
Thorsten Knappenberger; Markus Flury; Earl D. Mattson; James B. Harsh
Mobile colloids can play an important role in contaminant transport in soils: many contaminants exist in colloidal form, and colloids can facilitate transport of otherwise immobile contaminants. In unsaturated soils, colloid transport is, among other factors, affected by water content and flow rate. Our objective was to determine whether water content or flow rate is more important for colloid transport. We passed negatively charged polystyrene colloids (220 nm diameter) through unsaturated sand-filled columns under steady-state flow at different water contents (effective water saturations Se ranging from 0.1 to 1.0, with Se = (? ¢ ?r)/(?s ¢ ?r)) and flow rates (pore water velocities v of 5 and 10 cm/min). Water content was the dominant factor in our experiments. Colloid transport decreased with decreasing water content, and below a critical water content (Se < 0.1), colloid transport was inhibited, and colloids were strained in water films. Pendular ring and water film thickness calculations indicated that colloids can move only when pendular rings are interconnected. The flow rate affected retention of colloids in the secondary energy minimum, with less colloids being trapped when the flow rate increased. These results confirm the importance of both water content and flow rate for colloid transport in unsaturated porous media and highlight the dominant role of water content.
The effects of ozone and water exchange rates on water quality and rainbow trout Oncorhynchus mykiss performance in replicated water recirculating systems
John Davidson; Christopher Good; Carla Welsh; Steven Summerfelt
Rainbow trout Oncorhynchus mykiss performance and water quality were evaluated and compared within six replicated 9.5m3 water recirculating aquaculture systems (WRAS) operated with and without ozone at various water exchange rates. Three separate studies were conducted: (1) low water exchange (0.26% of the total recycle flow) with and without ozone; (2) low water exchange with ozone versus high water exchange
Water flow over subtidal rock walls: relation to distributions and growth rates of sessile suspension feeders in the Gulf of Maine Water flow and growth rates
James J. Leichter; Jon D. Witman
Moving water delivers food resources to sessile suspension feeding invertebrates and the interaction between water motion and substrate topography may dramatically influence the ecology of these animals. Growth rates of two species of sessile suspension feeders were compared between positions within individual 1.5-m high rock walls at an offshore site at 30-m depth in the Gulf of Maine, USA. The
Evaporative spray cooling of plain and microporous coated surfaces.
Kim, J. H.; You, S. M.; Choi, S. U.-S.; Energy Technology; Univ. of Texas at Arlington
Experiments were performed on air and evaporative spray cooling of plain and microporous coated surfaces on flat and cylindrical heaters. Micron-size aluminum particles were used to build the microporous structures on the heated surfaces. To analyze the evaporative cooling, heat transfer curves were obtained in the form of the wall temperature difference versus heat flux. The heat transfer coefficients were also determined as a function of heat flux. Three water flow rates (1.25, 1.75 and 2.40 ml/min) were tested for the flat heater and one rate (3.0 ml/min) for the cylindrical heater, maintaining the air pressure of 7 psig (48 kPa) at the inlet of the nozzle. The effect of different particle sizes in the coating was also tested to optimize the microporous coating technique. Spraying water droplets on the microporous coating surface enhanced the heat removal due to the capillary pumping phenomenon through the microporous cavities connecting each other. The evaporative spray cooling increased the heat transfer coefficient by up to 400% relative to that of the uncoated surface cooled by dry air, and this enhancement was maintained at high heat fluxes by using microporous surfaces.
Investigation of Electrohydrodynamically-Enhanced Convective Heat and Mass Transfer from Water Surface
Babak Kamkari; Ali Akbar Alemrajabi
Enhancement of forced flow evaporation rate by applying electric field (corona wind) has been experimentally evaluated in this study. Corona wind produced by a fine wire electrode which was charged with positive high DC voltage impinges to water surface and leads to evaporation enhancement by disturbing the saturated air layer over the water surface. The study was focused on the
Phytoplankton sinking rates in oligotrophic waters off Hawaii, USA
P. K. Bienfang
The sinking rates in two size fractions of natural phytoplankton were measured over much of the photic zone in a subtropical environment. At 24, 40 and 71 m, sinking rates (▒ SD) of the 3 to 20 Ąm fractions were 0.72▒0.05, 0.83▒0.05, and 0.34▒0.04 m Ę d-1, respectively, and rates for the 20 to 102 Ąm fraction were 1.50▒0.21, 1.65▒0.14,
Commentary on ``Figuring Physics/Rapid Evaporation''
NASA Astrophysics Data System (ADS)
Bohren, Craig
The Figuring Physics that appeared in our April 2007 issue has drawn a number of responses. The question posed by Paul Hewitt in that piece had to do with evaporative cooling: "Consider four grams of boiling water poured onto a cold surface. Suppose one gram rapidly evaporates by absorbing 540 calories from the remaining three grams of water, ideally with no other heat transfer occurring. The remaining three grams will become (a) water at a temperature above 0░C, (b) water at 0░C, or (c) ice at 0░C." Hewitt's answer (c) drew protests from readers who argued that this would violate the second law of thermodynamics.
A New Technique Keeping off the Mn Evaporant from Oxygen Atmosphere during Reactive Evaporation Process
Masaaki Isai; Takeyoshi Shimada; Takaaki Matsui; Hiroshi Fujiyasu
Manganese oxide films for lithium secondary batteries were prepared using a reactive evaporation method. The Mn metal in the crucible suffers severe oxidation during the reactive evaporation process, which deteriorates it's deposition rate with increasing deposition run. It is also difficult to maintain the stoichiometry of films from run to run. This paper shows a new technique which keeps off
An Experimental Study of Transient Heat Transfer Characteristics of an Evaporator Using an Internally Grooved Tube
NASA Astrophysics Data System (ADS)
Koyama, Shigeru; Inoue, Norihiro; Fujii, Tetsu
Transient characteristics of an evaporator installed in a vapor compression heat pump system using R 22 as a working fluid have been experimentally investigated in the case of step change in the inlet refrigerant flow rate. The test evaporator is a double-tube heat exchanger in which the refrigerant flows inside the inner tube and the heating water flows counter currently in the surrounding annulus. The inner tube is an internally grooved copper tube of a 9.52 mm o.d. and an 8.72 mm mean i.d. The refrigerant flow rate was regulated by the expansion valve. The results are: (1) The transient change of local refrigerant flow pattern was observed and graphically demonstrated. (2) The changes of inlet refrigerant flow rate, local vapor pressure, local wall temperature and local heating water temperature were measured. (3) The local values of heat exchange rate, coefficient of evaporation heat transfer, vapor quality, void fraction, mean density and refrigerant flow rate were evaluated by solving unsteady energy equation of heating water and unsteady continuity and energy equations of refrigerant using the measured values mentioned above. (4) The local hold up of refrigerant changes corresponding to the change of refrigerant flow rate. (5) In the case of step decrease, the appearance of maximum values of mean density in the evaporation region corresponds to the minimum values of heat exchange rate, vapor quality and void fraction in 10 to 20 sec. after step change. (6) In the case of step increase, the earlier changes in wall temperature, heating water temperature and heat exchange rate at the more upper stream correspond to the shift of the dry out point from the upper to lower stream. (7) Dynamic stability time in the case of the step increase is longer than in the case of the step decrease.
Effects of cattle manure on erosion rates and runoff water pollution by faecal coliforms
Quinton, John
Effects of cattle manure on erosion rates and runoff water pollution by faecal coliforms M that are produced annually in many areas in which cattle are raised could be an important source of organic matter. In this paper, the effects of cattle manure application on soil erosion rates and runoff and on surface water
Gas exchange characteristics, metabolic rate and water loss of the Heelwalker, Karoophasma biedouwensis (Mantophasmatodea: Austrophasmatidae).
Chown, S L; Marais, E; Picker, M D; Terblanche, J S
This study presents the first physiological information for a member of the wingless Mantophasmatodea, or Heelwalkers. This species shows cyclic gas exchange with no evidence of a Flutter period (more typical of discontinuous gas exchange in insects) and no indication that the spiracles are fully occluded during quiescent metabolism. Standard metabolic rate at 20 degrees C was 21.32+/-2.73 microl CO(2)h(-1) (mean+/-S.E.), with a Q(10) (10-25 degrees C) of 1.7. Increases in V()CO(2) associated with variation in mass and with trial temperature were modulated by an increase in burst period volume and a decline in cycle frequency. Total water loss rate, determined by infrared gas analysis, was 0.876+/-0.08 mg H(2)Oh(-1) (range 0.602-1.577, n=11) whilst cuticular water loss rate, estimated by linear regression of total water loss rate and metabolic rate, was 0.618+/-0.09 mg H(2)Oh(-1) (range 0.341-1.363, n=11). Respiratory water loss rate was therefore no more than 29% of the total rate of water loss. Both total water loss rate and estimated cuticular water loss rate were significantly repeatable, with intraclass correlation coefficients of 0.745 and 0.553, respectively. PMID:16466738
Related Rates Introduction: Consider water draining from the bottom of a circular cylin-
Tavener, Simon
above b), slide the graduated beaker under the outlet pipe and start the stop- watch. When the waterRelated Rates Introduction: Consider water draining from the bottom of a circular cylin- der. The volume of water remaining in the cylinder is given by v = r2 h, where r is constant and h is the depth
Conservation Using a Rate of Return Decision Rule: Some Examples from California Municipal Water Departments
NASA Astrophysics Data System (ADS)
Mercer, Lloyd J.; Morgan, W. Douglas
A significant alternative to physical rationing of water to achieve conservation is provided by the price system. To act like profit maximizing firms, municipal water utilities (MWD's) should price their water so as to earn the opportunity cost of capital (the market rate of return) on the assets. The actual internal rate of return is calculated for a sample of 30 California MWD's for a 12-year period. For the 26 MWD's with a rate of return less than 10%, iterative simulations are run with increases in the MWD's average price to achieve the target rate of return. The magnitude of water conservation using the rate of return rule is reported for three alternative price elasticities of demand. The new implicit prices necessary to achieve the target rate of return are shown to be less than the cost of the cheapest new surface supply.
Feasibility Study ¢ Using a Solar Evaporator to Reduce the Metalworking Fluid (MWF) Waste Stream
Lazarus, Lloyd
A solar evaporator was designed, built, and operated to reduce the water-based metalworking fluid waste stream. The evaporator was setup in Waste ManagementÆs barrel lot inside one of the confinement areas. The unit processed three batches of waste fluid during the prototype testing. Initial tests removed 13% of the fluid waste stream. Subsequent modifications to the collector improved the rate to almost 20% per week. Evaluation of the risk during operation showed that even a small spill when associated with precipitation, and the unit placement within a confinement area, gave it the potential to contaminate more fluid that what it could save.
Evaporative cooling of air in impinging streams
B. Yao; Y. Berman; A. Tamir
An experimental study was conducted on evaporative cooling of air in an impinging-stream reactor, in which two droplet gas streams flow in opposite directions and meet in the impingement zone. The air was cooled by evaporation of water droplets. Volumetric heat-transfer coefficients h{sub v} determined enabled the authors to evaluate the performance of the cooler. Maximum values of h{sub v}
Water Evaporation Studies in Texas.
Patterson, R. E. (Raleigh Elwood); Bloodgood, Dean W.; Smith, R. L.
JUN '8.04 8.15 8.18 9.62 3.32 91 70 75 5,515 2,929 8.75 7.97 10.44 1.91 93 69 2,685 9.10 3.36 2.96 93 5,425 6.65 3.17 3.15 92 70 79 2,602 9.40 2.73 87 58 52 4,213 7.02 3.11 91 69 68 4,960 7.46 3.44 3.16 93....76 70 45 2,860 5.14 1.38 1.32 68 39 59 6,570 3.87 2.91 3.00 72 50 80 4,199 - .66 59 fl - 5,617 4.03 2.40 69 43 68 6,780 4.00 1.74 2.05 70 41 59 5,103 from APR 5.72 5.29 5.75 7':06 4.03 78 55 72 6,465 4...
Measuring sub-canopy evaporation in a forested wetland using an ensemble of methods
NASA Astrophysics Data System (ADS)
Allen, S. T.; Edwards, B.; Reba, M. L.; Keim, R.
Evaporation from the sub-canopy water surface is an integral but understudied component of the water balance in forested wetlands. Previous studies have used eddy covariance, energy balance approaches, and water-table fluctuations to assess whole-system evapotranspiration. However, partitioning evaporation from transpiration is necessary for modeling the system because of different controls over each process. Sub-canopy evaporation is a physically controlled process driven by relatively small gradients in residual energy transmitted through the canopy. The low-energy sub-canopy environment is characterized by a spatiotemporally varying light environment due to sunflecks, small and often inverse temperature and vapor gradients, and a high capacity for heat storage in flood water, which each present challenges to common evapotranspiration measurement techniques. Previous studies have examined wetland surface evaporation rates with small lysimeter experiments, but this approach does not encapsulate micrometeorological processes occurring at the scale of natural wetlands. In this study, we examine a one year time series of in situ sub-canopy flux measurements from a seasonally flooded cypress-tupelo swamp in southeast Louisiana. Our objective is to apply these data towards modeling sub-canopy energy flux responses to intra-annual hydrologic, phenologic, and climatic cycles. To assess and mitigate potential errors due to the inherent measurement challenges of this environment, we utilized multiple measurement approaches including eddy covariance, Bowen ratio energy balance (with both air to air gradients and water surface to air gradients) and direct measurement using a floating evaporation pan. Preliminary results show that Bowen ratio energy balance measurements are useful for constraining evaporation measurements when low wind speed conditions create a non-ideal setting for eddy covariance. However, Bowen ratios were often highly erratic due to the weak temperature and humidity gradients. This suggests the need to use combined methods during periods with problematic boundary layer conditions.
Validation of the doubly labeled water method under low and high humidity to estimate metabolic rate and water flux
Williams, Jos. B.
Validation of the doubly labeled water method under low and high humidity to estimate metabolic and high humidity to estimate metabolic rate and water flux in a tropical snake (Boiga irregularis). J Appl uses in- direct calorimetry to assess the effects of humidity on the accuracy of the doubly labeled
Predicted impact of core flow rate on the corrosion mitigation effectiveness of hydrogen water chemistry for Kuosheng boiling water reactor
Mei-Ya Wang; Tsung-Kuang Yeh; Charles F. Chu; Ching Chang
It is currently a common practice that a boiling water reactor (BWR) adopts hydrogen water chemistry (HWC) for mitigating corrosion in structural components in its primary coolant circuit. When the core flow rate (CFR) in a BWR is changed, the coolant residence time in the primary coolant circuit would be different. The concentrations of major redox species (i.e. hydrogen, oxygen,
Contaminated water can lead to volatilization of chemicals to residential indoor air. Previous research has focused on only one source (shower stalls) and has been limited to chemicals in which gas-phase resistance to mass transfer is of marginal significance. As a result, attemp...
Methoxychlor (2,2-bis(methoxyphenyl)-1,1,1-trichloroethane) and DDT (2,2-bis(chlorophenyl)-1,1,1-trichloroethane) undergo different hydrolytic degradation pathways in water at pH's common to the aquatic environment. For methoxychlor at common aquatic pH's, the reaction is pH inde...
Helicity transfer in rotary evaporator flow
NASA Astrophysics Data System (ADS)
Hamba, Fujihiro; Niimura, Kazuhiro; Kitagawa, Yuichi; Ishii, Kazuyuki
Mechanical rotation of a magnetic stirrer or a rotary evaporator can induce an enantiomeric excess of supramolecular species. In this study, we investigate the effect of fluid motion in a rotary evaporator on chiral supramolecular species. It is shown theoretically that the twisting effect of fluid motion on cylindrical particles is expressed in terms of helicity dissipation rate. Helicity dissipation can be interpreted as the helicity transfer from helical fluid motion to chiral supramolecular structures. A numerical simulation of flow in a rotary evaporator was carried out to evaluate the helicity and its dissipation rate. The volume integral of the helicity dissipation in the computational domain showed a positive value; its sign agrees with experiment in which the right-handed helical structures of J-aggregates were induced by the counter-clockwise rotation of a rotary evaporator. Furthermore, terms in the transport equation for the helicity were evaluated for investigating the helicity behavior.
Water, salt, and energy balances of the Dead Sea
N. G. Lensky; Y. Dvorkin; V. Lyakhovsky; I. Gertman; I. Gavrieli
The Dead Sea is a hypersaline terminal lake experiencing a water level drop of about 1 m\\/yr over the last decade. The existing estimations for the water balance of the lake are widely variable, reflecting the unknown subsurface water inflow, the rate of evaporation, and the rate of salt accumulation at the lake bottom. To estimate these we calculate the
Irrigation - How Best to Water Your Desert Trees
John Eisenhower
It might be helpful to start by discussing how plants process water and how this process protects plants from the sun's intense heat. When temperatures are high and humidity is low, the transpiration rate for plants is high. Transpiration rate describes how fast water vapor is lost to the atmosphere through evaporation, primarily from a plant's leaves. This water loss
Infectivity and antigenicity reduction rates of human rotavirus strain Wa in fresh waters.
Pancorbo, O C; Evanshen, B G; Campbell, W F; Lambert, S; Curtis, S K; Woolley, T W
The rates of inactivation of human rotavirus type 2 (strain Wa) (HRV-Wa) and poliovirus type 1 (strain CHAT) were compared in polluted waters (creek water and secondary effluent before chlorination) and nonpolluted waters (lake water, groundwater, and chlorinated tap water). Viral infectivity titers were determined by plaque assays, while HRV-Wa antigenicity also was monitored by an enzyme-linked immunosorbent assay. Both viruses persisted longest in lake water and shortest in tap water. The actual inactivation times (i.e., times required for two-log10 reductions of initial viral titers) for the two viruses were significantly different in all waters except tap water. With the exception of the groundwater and secondary effluent results, the HRV-Wa inactivation times in the fresh waters tested were significantly different. Owing perhaps to aggregation, HRV-Wa appeared less susceptible to the effects of chlorine than previously reported for this virus and for the simian rotavirus SA11. HRV-Wa displayed prolonged survival in lake water and groundwater exceeding that previously reported for the SA11 virus. The HRV-Wa infectivity reduction rate (ki) was significantly correlated with the water pH (i.e., as pH increased, ki increased). The water pH may have influenced viral aggregation and thereby HRV-Wa susceptibility to other virucidal factors in the water. Enzyme-linked immunosorbent assay results showed similar inactivation patterns with the most significant reduction in HRV-Wa antigenicity occurring in polluted waters and tap water. In all waters, particularly tap water, infectivity declined at a faster rate than antigenicity. It is proposed that HRV-Wa can be used as a model for future studies of rotaviral persistence in the aquatic environment. Images PMID:2821902
Effects of dissolved air flotation hydraulic loading rate on water treatment performance
Tobiason, J.E.; Edzwald, J.K.; Amato, T.; Maggi, L.J.
The performance of dissolved air flotation (DAF) followed by granular media filtration for water treatment was evaluated via pilot-scale studies for two water sources. The study focused on short flocculation times (5--8 minutes), high DAF hydraulic loading rates (17--44 m/hr (7--18 gpm/ft{sup 2})) and rapid rate filtration (10--20 m/hr (4--8 gpm/ft{sup 2})). Excellent treatment performance was achieved in terms of DAF clarified water turbidity, filtered water turbidity, organic matter removal and filtered water production. Bubble carryover from the DAF tank was mitigated by employing either internal or external air removal strategies. Overall, the results demonstrate the effectiveness of an integrated, high rate flocculation/DAF/filtration water treatment strategy.
Evaporation, Boiling and Bubbles
ERIC Educational Resources Information Center
Goodwin, Alan
Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. Theģ
Chemical and biological processes of evaporation ponds
Technology Transfer Automated Retrieval System (TEKTRAN)
Agricultural evaporation ponds are designed to impound and dissipate saline agricultural drainage water in areas with no opportunities for offsite disposal in the San Joaquin Valley of California. This paper reviews and summarizes research findings on the pond chemistry. Drainage waters in these pon...
Delineation of recharge rate from a hybrid water table fluctuation method
NASA Astrophysics Data System (ADS)
Park, Eungyu
The concept of the hybrid water table fluctuation (WTF) method for recharge rate estimation was revisited. To estimate the recharge rate, a physically based WTF equation was established. The concept of transient fillable porosity was proposed and computed with unsaturated hydraulics models. The developed model is tested by applying to the water table fluctuation data from Hongcheon, Korea. In the applications, the recharge and fillable porosity estimates were found to be most sensitive to nonlinearity in the unsaturated water content profile and permeability. Also, the water table level drift, which does not originate from precipitation, serves as a major source of estimation error.
Evaporatively driven morphological instability Robert W. Style1
Wettlaufer, John S.
.70. w, 81.30.Mh I. INTRODUCTION AND MOTIVATION Evaporation of water is an important phase transformation when used with hard water 7 . Du and Stone 5 observed the evolution of ramified crys- tal structures
Evaporative Cooling of Trapped Atoms
Wolfgang Ketterle; N. J. Van Druten
This report discusses the following topics on evaporative cooling of trapped atoms: Theoretical models for evaporative cooling; the role of collisions for real atoms; experimental techniques and summary of evaporative cooling experiments. 166 refs., 6 figs., 3 tabs.
Structural transformation in supercooled water controls the crystallization rate of ice.
Moore, Emily B; Molinero, Valeria
One of water's unsolved puzzles is the question of what determines the lowest temperature to which it can be cooled before freezing to ice. The supercooled liquid has been probed experimentally to near the homogeneous nucleation temperature, T(H) ? 232 K, yet the mechanism of ice crystallization-including the size and structure of critical nuclei-has not yet been resolved. The heat capacity and compressibility of liquid water anomalously increase on moving into the supercooled region, according to power laws that would diverge (that is, approach infinity) at ~225 K (refs 1, 2), so there may be a link between water's thermodynamic anomalies and the crystallization rate of ice. But probing this link is challenging because fast crystallization prevents experimental studies of the liquid below T(H). And although atomistic studies have captured water crystallization, high computational costs have so far prevented an assessment of the rates and mechanism involved. Here we report coarse-grained molecular simulations with the mW water model in the supercooled regime around T(H) which reveal that a sharp increase in the fraction of four-coordinated molecules in supercooled liquid water explains its anomalous thermodynamics and also controls the rate and mechanisms of ice formation. The results of the simulations and classical nucleation theory using experimental data suggest that the crystallization rate of water reaches a maximum around 225 K, below which ice nuclei form faster than liquid water can equilibrate. This implies a lower limit of metastability of liquid water just below T(H) and well above its glass transition temperature, 136 K. By establishing a relationship between the structural transformation in liquid water and its anomalous thermodynamics and crystallization rate, our findings also provide mechanistic insight into the observed dependence of homogeneous ice nucleation rates on the thermodynamics of water. PMID:22113691
Evaporation in different liquids: secondary students' conceptions
NASA Astrophysics Data System (ADS)
Co?tu, Bayram; Ayas, Alipa?a
This study explores secondary school studentsÆ understanding of evaporation and investigates whether students associate the concept of evaporation with only water as a liquid. An open-ended written test was developed using three different words (water, liquid or alcohol) to state the question phrases. The test was implemented on a sample of 313 students at different levels of schooling. Clinical interviews, in which ethyl alcohol was used as an example of liquids, were also undertaken with 12 students, either individually or as a group. From the collected data, it was found that most of the students at different levels lack understanding of the concept and have several misconceptions. Various misconceptions of the evaporation concept that differ from those cited in the related literature were determined. The most important result was that studentsÆ written responses showed some specific misconceptions when they were presented with the questions using three different words; liquid, water and alcohol.
Estimating Exchange Rates of Water in Embayments using Simple Budget Equations.
NSDL National Science Digital Library
Keith Sverdrup
Simple budgets may be used to estimate the exchange of water in embayments that capitalize on the concept of steady state and conservation principals. This is especially true for bays that experience a significant exchange of freshwater. This exchange of freshwater may reduce the average salt concentration in the bay compared to seawater if it involves addition of freshwater from rivers, R, and/or precipitation, P. Alternatively, it may increase the average salt concentration in the bay compared to seawater if there is relatively little river input and high evaporation, E. Since freshwater input changes the salt concentration in the bay, and salt is a conservative material, it is possible to combine two steady state budgets for a bay, one for salt and one for water, to solve for the magnitude of the water flows that enter and exit the bay mouth. Students will make actual calculations for the inflow and outflow of water to Puget Sound, Washington and the Mediterranean Sea and compare them to actual measured values.
The Importance of Water Exchange Rates in the Design of Responsive Agents for MRI
Sherry, A. Dean; Wu, Yunkou
The rate of water exchange in lanthanide complexes is often overlooked as an important parameter in the design of responsive MR imaging agents. Most often, the number of inner-sphere water coordination sites or the rotational mobility of the complex are considered as the central theme while water exchange is either assumed to be ōfast enoughö or entirely ignored. On the other hand, relaxation and shift theories predict that water exchange rates may indeed be the key parameter one should consider in any new molecular design. In this short review, the impact of water exchange rates on three classes of lanthanide-based MRI contrast agents, T1-based relaxation agents, T2 exchange line-broadening agents and chemical exchange saturation transfer (CEST) agents, is illustrated and discussed. PMID:23333571
Visualization of an evaporating thin layer during the evaporation of a nanofluid droplet.
Shin, Dong Hwan; Allen, Jeffrey S; Choi, Chang Kyoung; Lee, Seong Hyuk
During the evaporation of a droplet, there exists an evaporating thin layer that is difficult to visualize because of optical restrictions. The present study visualized this thin layer by using a reflective-mode, confocal microscope that can provide improved signal-to-noise focal plane imaging over traditional optical microscopy while simultaneously serving as an interferometer when imaging thin liquid films. The spatial distribution of the evaporating thin layer thickness was determined from interferometric fringe analysis. Three distinct fringe patterns, or regions, were observed depending on the nanoparticle concentration. These regions are referred to as uniform, slow extension, and rapid extension. The formation of the three regions is closely associated with the variation of the evaporating thin layer thickness of a nanofluid droplet. The nanoparticle bank formed near the contact line region substantially affects the rate of change in the evaporating thin layer thickness that increases with the nanoparticle concentration. PMID:25586137
A novel silicon bi-textured micropillar array to provide fully evaporated steam for a micro-Rankine cycle application
NASA Astrophysics Data System (ADS)
Azarkish, H.; Behzadmehr, A.; Fanaei Sheikholeslami, T.; Sarvari, S. M. H.; Frķchette, L. G.
In the present work, a novel silicon micropillar array with rough and smooth sections is introduced as a microstructured evaporator to provide a stable flow of fully evaporated steam without any pulsations or liquid droplets. Two mechanisms are proposed to increase the performance of a micro-evaporator. The first one consists of increasing the water spreading over the evaporator area by creating rough surfaces at the base of the micropillars, which also tends to increase the surface for thin film evaporation. The second mechanism is to prevent the formation of water droplets over the micropillar array with a higher surface energy barrier created by a smooth portion at the top of the pillars. The rough¢smooth micropillar arrays were fabricated using deep reactive ion etching over a 1?cm2 membrane with through holes to continuously provide the liquid. Experimental measurements and observations show that the maximum rate of fully evaporated steam is increased by 52% to 122%, for a surface temperature range of 95 to 125?░C, by using the proposed rough¢smooth microstructures instead of only smooth silicon microstructures.
Effects of flow and water chemistry on lead release rates from pipe scales.
Xie, Yanjiao; Giammar, Daniel E
Lead release from pipe scales was investigated under different water compositions, stagnation times, and flow regimes. Pipe scales containing PbO(2) and hydrocerussite (Pb(3)(OH)(2)(CO(3))(2)) were developed on lead pipes by conditioning the pipes with water containing free chlorine for eight months. Water chemistry and the composition of the pipe scales are two key factors affecting lead release from pipe scales. The water rarely reached equilibrium with pipe scales within one day, which makes solid-water contact time and corrosion product dissolution rates the controlling factors of lead concentrations for the conditions tested. Among five water compositions studied, a solution with orthophosphate had the lowest dissolved lead release rate and highest particulate lead release rate. Free chlorine also decreased the dissolved lead release rate at stagnant conditions. Water flow increased rates of release of both dissolved and particulate lead by accelerating the mass transfer of lead out of the porous pipe scales and by physically destabilizing pipe scales. Dissolved lead comprised the majority of the lead released at both stagnant and laminar flow conditions. PMID:22018527
Effect of channel catfish stocking rate on yield and water quality in an intensive production system
Technology Transfer Automated Retrieval System (TEKTRAN)
The effect of stocking rate on production of NWAC 103 strain channel catfish (Ictalurus punctatus) and water quality was investigated using a completely randomized design in an intensively managed biofloc raceway system. Each of the 9 HDPE-lined raceways (4.6 m x 9.2 m with a 0.9-m water depth; 42.2...
Influence of white plastic and water replacement rates on pomegranate orchard phenology, fruit yield and quality
Technology Transfer Automated Retrieval System (TEKTRAN)
Currently, 98% of domestic commercial pomegranate fruit (Punica granatum L.) are produced in California on over 13,000 ha. In 2013, a pomegranate orchard, established in 2010 with a density of 558 trees/ha, was irrigated at water replacement rates of 35, 50 and 100% based on rainfall, tree water r...
Compensating inherent linear move water application errors using a variable rate irrigation system
Technology Transfer Automated Retrieval System (TEKTRAN)
Continuous move irrigation systems such as linear move and center pivot irrigate unevenly when applying conventional uniform water rates due to the towers/motors stop/advance pattern. The effect of the cart movement pattern on linear move water application is larger on the first two spans which intr...
Hale, Barbara N.
CALCULATION OF SCALED NUCLEATION RATES FOR WATER USING MONTE CARLO GENERATED CLUSTER FREE ENERGY inconsistent with the experimental properties of water. Summation of the scaled TIP4P free energy differencesMattio All Rights Reserved #12;iii ABSTRACT Helmholtz free energy differences, -dFn , are calculated
The Adjustment of Avian Metabolic Rates and Water Fluxes to Desert Environments
B. Irene Tieleman; Joseph B. Williams
We tested the hypothesis that birds in arid environments, where primary productivity is low and surface water is scarce, have reduced energy expenditure and water loss compared with their mesic counterparts. Using both conventional least squares re- gression and regression based on phylogenetically independent contrasts, we showed that birds from desert habitats have re- duced basal and field metabolic rates
Soil Water and Thermal Gradients in the Vadose Zone: Assessing Evapotranspiration, Recharge Rates and Shifts in Phreatophytic Water Source
NASA Astrophysics Data System (ADS)
Koonce, J.; Young, M.; Devitt, D.; Yu, Z.; Wagner, A.; Fenstermaker, L.
Soil water and temperature are important variables in energy and water balance studies, particularly to processes involved in evapotranspiration (ET), which provides a direct link between the balances and is crucial for closing the water budget. With a large uncertainty in precipitation rates from interannual variability and increased demand for water resources, understanding these processes is critical when assessing the movement of mass and energy through the vadose zone. Stress on the long-term water supply could lead to a potential shift of water source by phreatophytes. We seek answers to the following questions: Can we use soil temperature to estimate ET and downward water fluxes? Do changes in temperature signals follow shifts in water sources for plants? Although ET and recharge rates are primarily driven by atmospheric demand and water availability, to what extent does soil temperature change these rates? Data were analyzed from an array of soil water and temperature instruments, including TDR and heat dissipation sensors at multiple points from 30 to 500 cm, and fiber optic distributed temperature sensing at depth increments of 1.14 cm. ET data were obtained from an eddy covariance (EC) system and groundwater depth was measured using a pressure transducer in a well. Instruments were installed in Spring Valley, NV, a site dominated by Big Sage and Greasewood. ET dominates water loss at the site from March through September. We hypothesize that groundwater recharge did not occur within the valley floor during 2010-2011. Data indicate that snowmelt and precipitation percolates to ~300 cm depth (water contents increasing from 0.06 in Oct-2010 to 0.10 in May-2011). Gradual water content increases at 400 and 500 cm were measured; however, groundwater levels rose sharply from early October 2010 to approximately mid-June 2011, suggesting a high capillary fringe. Diurnal variation of soil temperatures are observed to ~50 cm depth and seasonal variation observed to ~500 cm. Sensors recorded multiple cold wetting fronts in March through April 2011. Using groundwater depth, changes in ET, precipitation, and soil moisture, we will correlate changes in temperature with infiltration and changes in source water. Furthermore, inverse parameter estimation of water content in a numerical model (HYDRUS 1D) will be simulated and compared to the results.
Stable isotope approach for estimating phreatic evaporation in irrigated lands of Ferghana Valley (Uzbekistan)
NASA Astrophysics Data System (ADS)
Umirzakov, G.; Barthold, F.-K.; Forkutsa, I.; Breuer, L.; Frede, H.-G.
Agriculture in Uzbekistan is the main consumer of water resources. However, due to low efficiency of the irrigation network and management, unproductive water losses are high and as a consequence, the groundwater level is elevated. Evaporation from the shallow groundwater increases the inefficient water losses in the irrigated lands. In our study we aim to estimate phreatic evaporation (EP) losses in intensively irrigated areas of the Ferghana Valley with the use of stable isotopes (Deuterium, 2H and Oxygen, 18O). Soil samples were collected during two vegetation periods at sites that differed in soil type and groundwater level. The soil samples were taken from the surface down to the groundwater level in 5-20 cm intervals. We used a cryogenic extraction method to extract the water from the soil. Isotope signatures (?2H and ? 18O) of the extracted water were then determined using a DLT-100 laser spectroscope. Then EP rate was calculated by fitting an exponential function to the experimental isotope soil profile. Results of our study revealed that the EP rate is higher on sites characterized by clayey loam texture in comparison to loamy and sandy sites; and EP rates increase with the rise of the groundwater (R2=0.85-0.94). The maximum EP rates of 349 mm a-1, 245 mm a-1 and 154 mm a-1 in clayey loam, loam and sand, respectively, are observed at shallow (>1m) groundwater levels. Results of the study indicate that Ep contributes considerably to overall evaporation, with annual rates of 80 to 349 mm (6- 35% of total water losses in the water balance). Spatial patterns are yet to be investigated in order to provide recommendations for improving irrigation management in the irrigated lands of Ferghana Valley.
New measurements of the ion content of evaporation-humidified air
Hugh R. Carlon
New measurements by electrical conductivity of the ion content of untreated room air humidified by evaporating liquid water in a closed container are presented. Large populations of the singly charged hydrated ions can be maintained in the container for an hour or more after the liquid water evaporation source is removed. The new results suggest that evaporation produces large populations
A Discrete\\/Continuous Choice Approach to Residential Water Demand under Block Rate Pricing
Julie A. Hewitt; W. Michael Hanemann
A discrete\\/continuous choice model of the residential demand for water under block rate pricing is presented, estimated, and compared to results of regression models. The empirical analysis uses a dataset from a previously published study, Nieswiadomy and Molina (1989), of household level panel data from Denton, Texas, for summer months from 1981 to 1985 with an increasing block rate in
Oxygen transfer rate estimation in oxidation ditches from clean water measurements
A. A. A. Abusam; K. J. Keesman; K. Meinema; G. van Straten
Standard methods for the determination of oxygen transfer rate are based on assumptions that are not valid for oxidation ditches. This paper presents a realistic and simple new method to be used in the estimation of oxygen transfer rate in oxidation ditches from clean water measurements. The new method uses a loop-of-CSTRs model, which can be easily incorporated within control
Volumetric flow rate comparisons for water and product on pasteurization systems.
Schlesser, J E; Stroup, W H; McKinstry, J A
A flow calibration tube system was assembled to determine the volumetric flow rates for water and various dairy products through a holding tube, using three different flow promotion methods. With the homogenizer, the volumetric flow rates of water and reconstituted skim milk were within 1.5% of each other. With the positive displacement pump, the flow rate for reconstituted skim milk increased compared with that for water as the pressure increased or temperature decreased. The largest increase in flow rate was at 310-kPa gauge and 20 degrees C. On a magnetic flow meter system, the volumetric flow rates of water and reconstituted skim milk were within .5% of the flow rate measured from the volume collected in a calibrated tank. The flow rate of whole milk was similar to that of skim milk on the three flow promoters evaluated. Ice milk mix increased the flow rate of the positive displacement pump, but not the homogenizer and magnetic flow meter system. PMID:8201053
Evaporation of germanium nitride
╔. A. Ryklis; A. S. Bolgar; M. D. Lyutaya; V. V. Fesenko
1.A study was made, using Knudsen's effusion method, of the evaporation of germanium nitride over the temperature range 923¢963░K. It is shown that, on evaporation, this compound dissociates into solid germanium and nitrogen.2.The vapor pressure above germanium nitride depends on test duration and on the surface area of the effusion orifice.3.The equilibrium values of vapor pressure above Ge3N4 and the
G. Riddle
Both resistive and insulating cermets were obtained from experiments on co-evaporated materials. Stable resistivities in the 1000 micro-ohm-centimeter range were obtained from mixtures of germanium and chromium, and from a reaction product of aluminum and alumina. Glassy dielectric films were obtained from reaction products of aluminum and alumina, and from aluminum and silicon monoxide. The factors that control these co-evaporation
No effect of water on oxygen self-diffusion rate in forsterite
NASA Astrophysics Data System (ADS)
Fei, Hongzhan; Wiedenbeck, Michael; Yamazaki, Daisuke; Katsura, Tomoo
We systematically measured oxygen self-diffusion coefficients (DO) in forsterite along b crystallographic axis at a pressure of 8 GPa and temperatures of 1600-1800 K, over a wide range of water content (CH2O) from <1 up to ~800 weight ppm. The experimental results suggest that DO ? (CH2O)0.05▒0.06 ? (CH2O)0. Thus, water has no significant effect on oxygen self-diffusion rate in forsterite. Since the CH2O dependence of silicon self-diffusion rate is also very small, the effect of water on olivine rheology is not significant by assuming the diffusion controlled creep mechanism.
Nonlinear effects of salt concentrations on evaporation from porous media
NASA Astrophysics Data System (ADS)
Norouzi Rad, Mansoureh; Shokri, Nima
Evaporation from porous media saturated with salt solution is influenced by the interactions among the transport properties of porous media, thermodynamics of the evaporating solution and environmental conditions. To study the effects of salt concentrations on the evaporation dynamics, we conducted a series of evaporation experiments under constant atmospheric conditions using columns packed with sand particles saturated with various NaCl solutions differing in concentrations. Results show that the evaporation rate decreases as NaCl concentration increases only up to a certain level. When exceeding this level, any further increase of NaCl concentration results in higher evaporation rates which is described theoretically using the thermodynamics of the solution. Results also reveal a nonlinear relation between NaCl concentrations and onset of efflorescence which is described by the numerical solution of the classical convection-diffusion equation. Moreover, we found a strong correlation between the growth dynamics of precipitated salt at the surface and the evaporation rate such that the maximum rate of surface coverage by salt coincide with the end of stage-1 evaporation. This potentially offers a new method to nondestructively study the evaporation process from saline porous media.
Synthesis of novel core-shell structured dual-mesoporous silica nanospheres and their application for enhancing the dissolution rate of poorly water-soluble drugs.
Wu, Chao; Sun, Xiaohu; Zhao, Zongzhe; Zhao, Ying; Hao, Yanna; Liu, Ying; Gao, Yu
Novel core-shell dual-mesoporous silica nanospheres (DMSS) with a tunable pore size were synthesized successfully using a styrene monomer as a channel template for the core and cetyltrimethyl ammonium bromide (CTAB) as a channel template for the shell in order to improve the dissolution rate of poorly water-soluble drugs. Simvastatin was used as a model drug and loaded into DMSS and the mesoporous core without the shell (MSC) by the solvent evaporation method. The drug loading efficiency of DMSS and MSC were determined by thermogravimetric analysis (TGA) and ultraviolet spectroscopy (UV). Characterization, using scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR) showed that simvastatin adsorbed in DMSS and MSC was in an amorphous state, and in vitro release test results demonstrated that both DMSS and MSC increased the water solubility and dissolution rate of simvastatin. The shell structure of DMSS was able to regulate the release of simvastatin compared with MSC. It is worth noting that DMSS has significant potential as a carrier for improving the dissolution of poorly water-soluble drugs and reducing the rapid release. PMID:25280705
Acoustic Signature of Evaporation from Porous Media
NASA Astrophysics Data System (ADS)
Grapsas, N. K.; Shokri, N.
During evaporation from saturated porous media, rapid interfacial jumps at the pore scale, known as Haines jumps, occur as air invades the pore network and displaces the evaporating fluid. This process produces crackling noises that can be detected using an acoustic emission (AE) machine. In this study, we investigated the acoustic signature of evaporation from porous media using Hele-Shaw cells packed with seven types of sand and glass beads differing in particle size distribution and surface roughness. Each sample was saturated with dyed water, left to evaporate under constant atmospheric conditions on a digital balance in an environmental chamber, and digitally imaged every 20 minutes to quantify phase distribution. An AE sensor was fixed to each column to record the features of observed AE events (hits) such as amplitude, absolute energy, and duration. Results indicate that the cumulative number of hits is strongly related to evaporative mass loss through time in all configurations. Additionally, the cumulative number of hits shares an inverse relationship with particle size and roughness. Finally, image analysis of the liquid phase distribution during evaporation reveals a strong correlation between the area invaded by air and the cumulative AE hits detected in each column. This confirms that AEs are generated by receding liquid menisci and the propagation of drying fronts in porous media. These results suggest that AE techniques may potentially be used to non-invasively analyze the drying of porous media.
Shale-oil-wastewater treatment by evaporation
Wakamiya, W.
Experimental studies were performed to assess the feasibility of using evaporation to treat oil shale retort water. Retort wastewaters from an in situ shale oil site near Vernal, Utah, were used in this study. This wastewater has a chemical oxygen demand (COD) of 7000 mg/L, total organic carbon (TOC) of 2000 mg/L, and ammonia concentrations of 1600 mg/L. Data for this study were collected from a bench-model evaporator with a 95 L/day capacity. Preliminary results show that reductions of 90% in COD, 89% in TOC, and 97% in ammonia were possible. Preliminary tests indicated that a concentration factor of 20 is optimum for operating at a desirable boiling point rise and suspended solids level in the evaporator sump. At a concentration factor of 20, the concentrated volume requiring disposal would be only 5% of the original water volume, so disposal costs would decrease proportionally.
Improvement of growth rate of plants by bubble discharge in water
NASA Astrophysics Data System (ADS)
Takahata, Junichiro; Takaki, Koichi; Satta, Naoya; Takahashi, Katsuyuki; Fujio, Takuya; Sasaki, Yuji
The effect of bubble discharge in water on the growth rate of plants was investigated experimentally for application to plant cultivation systems. Spinach (Spinacia oleracea), radish (Raphanus sativus var. sativus), and strawberry (Fragaria ū ananassa) were used as specimens to clarify the effect of the discharge treatment on edible parts of the plants. The specimens were cultivated in pots filled with artificial soil, which included chicken manure charcoal. Distilled water was sprayed on the artificial soil and drained through a hole in the pots to a water storage tank. The water was circulated from the water storage tank to the cultivation pots after 15 or 30 min discharge treatment on alternate days. A magnetic compression-type pulsed power generator was used to produce the bubble discharge with a repetition rate of 250 pps. The plant height in the growth phase and the dry weight of the harvested plants were improved markedly by the discharge treatment in water. The soil and plant analyzer development (SPAD) value of the plants also improved in the growth phase of the plants. The concentration of nitrate nitrogen, which mainly contributed to the improvement of the growth rate, in the water increased with the discharge treatment. The Brix value of edible parts of Fragaria ū ananassa increased with the discharge treatment. The inactivation of bacteria in the water was also confirmed with the discharge treatment.
Simultaneous heat and mass transfer inside a vertical channel in evaporating a heated falling glycols liquid film
NASA Astrophysics Data System (ADS)
Nait Alla, Abderrahman; Feddaoui, M'barek; Meftah, Hicham
The interactive effects of heat and mass transfer in the evaporation of ethylene and propylene glycol flowing as falling films on vertical channel was investigated. The liquid film falls along a left plate which is externally subjected to a uniform heat flux while the right plate is the dry wall and is kept thermally insulated. The model solves the coupled governing equations in both phases together with the boundary and interfacial conditions. The systems of equations obtained by using an implicit finite difference method are solved by Tridiagonal Matrix Algorithm. The influence of the inlet liquid flow, Reynolds number in the gas flow and the wall heat flux on the intensity of heat and mass transfers are examined. A comparison between the results obtained for studied glycols and water in the same conditions is made. The results indicate that water evaporates in more intense way in comparison to glycols and the increase of gas flow rate tends to improve slightly the evaporation.
Adu-Wusu, K.
Tank 26F supernate sample was sent by Savannah River Remediation to Savannah River National Laboratory for evaporation test to help understand the underlying cause of the recent gravity drain line (GDL) pluggage during operation of the 2F Evaporator system. The supernate sample was characterized prior to the evaporation test. The evaporation test involved boiling the supernate in an open beaker until the density of the concentrate (evaporation product) was between 1.4 to 1.5 g/mL. It was followed by filtering and washing of the precipitated solids with deionized water. The concentrate supernate (or concentrate filtrate), the damp unwashed precipitated solids, and the wash filtrates were characterized. All the precipitated solids dissolved during water washing. A semi-quantitative X-ray diffraction (XRD) analysis on the unwashed precipitated solids revealed their composition. All the compounds with the exception of silica (silicon oxide) are known to be readily soluble in water. Hence, their dissolution during water washing is not unexpected. Even though silica is a sparingly water-soluble compound, its dissolution is also not surprising. This stems from its small fraction in the solids as a whole and also its relative freshness. Assuming similar supernate characteristics, flushing the GDL with water (preferably warm) should facilitate dissolution and removal of future pluggage events as long as build up/aging of the sparingly soluble constituent (silica) is limited. On the other hand, since the amount of silica formed is relatively small, it is quite possible dissolution of the more soluble larger fraction will cause disintegration or fragmentation of the sparingly soluble smaller fraction (that may be embedded in the larger soluble solid mass) and allow its removal via suspension in the flushing water.
Methods of rating unsaturated zone and watershed characteristics of public water supplies in North Carolina
Eimers, Jo Leslie; Weaver, J.C.; Terziotti, Silvia; Midgette, R.W.
Overlay and index methods were derived for rating the unsaturated zone and watershed characteristics for use by the State of North Carolina in assessing more than 11,000 public water-supply wells and approximately 245 public surface-water intakes. The rating of the unsaturated zone and watershed characteristics represents a practical and effective means of assessing part of the inherent vulnerability of water supplies to potential contamination. Factors that influence the inherent vulnerability of the drinking water supply to potential contamination were selected and assigned ratings (on a scale of 1 to 10) to cover the possible range of values in North Carolina. These factors were assigned weights of 1, 2, or 3 to reflect their relative influence on the inherent vulnerability of the drinking water supply. The factor values were obtained from Geographic Information System data layers, and were transformed into grids having 60-meter by 60-meter cells, with each cell being assigned a value. Identification of factors, the development of ratings for each, and assignment of weights were based on (1) a literature search, which included examination of potential factors and their effects on the drinking water; and (2) consultation with experts in the science and engineering of hydrology, geology, forestry, agriculture, and water management. Factors selected for rating the inherent vulnerability of the unsaturated zone are vertical hydraulic conductance, land-surface slope, land cover, and land use. Vertical hydraulic conductance is a measure of the capacity of unsaturated material to transmit water. Land-surface slope influences whether precipitation runs off land surfaces or infiltrates into the subsurface. Land cover, the physical overlay of the land surface, influences the amount of precipitation that becomes overland flow or infiltrates into the subsurface. Land use describes activities that occur on the land surface and influence the potential generation of nonpoint-source contamination. Factors selected for rating the watershed characteristics upstream from surface-water intakes are average annual precipitation, land-surface slope, land cover, land use, and ground-water contribution. The average annual precipitation represents the mass of water that becomes available for transport in a watershed. Land-surface slope, land cover, and land use have similar influences in watersheds as those identified for the unsaturated zone. Ground-water contribution represents the part of streamflow that is derived from ground-water discharge.
Studies on the evaporation of crude oil and petroleum products II. Boundary layer regulation
Merv F. Fingas
Experiments were conducted to determine if oil and petroleum evaporation is regulated by the saturation of the air boundary layer. Experiments included the examination of the evaporation rate with and without wind. It was found that evaporation rates were similar for all wind conditions, but lower for the no-wind conditions. Experiments where the area and mass varied showed that boundary
Cross-sectional tracking of particle motion in evaporating drops: flow fields and interfacial accumulation.
Trantum, Joshua R; Eagleton, Zachary E; Patil, Chetan A; Tucker-Schwartz, Jason M; Baglia, Mark L; Skala, Melissa C; Haselton, Frederick R
The lack of an effective technique for three-dimensional flow visualization has limited experimental exploration of the "coffee ring effect" to the two-dimensional, top-down viewpoint. In this report, high-speed, cross-sectional imaging of the flow fields was obtained using optical coherence tomography to track particle motion in an evaporating colloidal water drop. This approach enables z-dimensional mapping of primary and secondary flow fields and changes in these fields over time. These sectional images show that 1 ?m diameter polystyrene particles have a highly nonuniform vertical distribution with particles accumulating at both the air-water interface and the water-glass interface during drop evaporation. Particle density and relative humidity are shown to influence interfacial entrapment, which suggests that both sedimentation rate and evaporation rate affect the dynamic changes in the cross-sectional distribution of particles. Furthermore, entrapment at the air-water interface delays the time at which particles reach the ring structure. These results suggest that the organization of the ring structure can be controlled based on the ratio of different density particles in a colloidal solution. PMID:23611508
Cooperation between bound waters and hydroxyls in controlling isotope-exchange rates
NASA Astrophysics Data System (ADS)
Panasci, Adele F.; McAlpin, J. Gregory; Ohlin, C. Andrķ; Christensen, Shauna; Fettinger, James C.; Britt, R. David; Rustad, James R.; Casey, William H.
Mineral oxides differ from aqueous ions in that the bound water molecules are usually attached to different metal centers, or vicinal, and thus separated from one another. In contrast, for most monomeric ions used to establish kinetic reactivity trends, such as octahedral aquo ions (e.g., Al(H 2O) 63+), the bound waters are closely packed, or geminal. Because of this structural difference, the existing literature about ligand substitution in monomer ions may be a poor guide to the reactions of geochemical interest. To understand how coordination of the reactive functional groups might affect the rates of simple water-exchange reactions, we synthesized two structurally similar Rh(III) complexes, [Rh(phen) 2(H 2O) 2] 3+ [ 1] and [Rh(phen) 2(H 2O)Cl] 2+ [ 2] where (phen) = 1,10-phenanthroline. Complex [ 1] has two adjacent, geminal, bound waters in the inner-coordination sphere and [ 2] has a single bound water adjacent to a bound chloride ion. We employed Rh(III) as a trivalent metal rather than a more geochemically relevant metal like Fe(III) or Al(III) to slow the rate of reaction, which makes possible measurement of the rates of isotopic substitution by simple mass spectrometry. We prepared isotopically pure versions of the molecules, dissolved them into isotopically dissimilar water, and measured the rates of exchange from the extents of 18O and 16O exchange at the bound waters. The pH dependency of rates differ enormously between the two complexes. Pseudo-first-order rate coefficients at 298 K for water exchanges from the fully protonated molecules are close: k0298 = 5 ū 10 -8(▒0.5 ū 10 -8) s -1 for [ 1] and k0298 = 2.5 ū 10 -9(▒1 ū 10 -9) for [ 2]. Enthalpy and entropy activation parameters (? Hć and ? Sć) were measured to be 119(▒3) kJ mol -1, and 14(▒1) J mol -1 K -1, respectively for [ 1]. The corresponding parameters for the mono-aquo complex, [ 2], are 132(▒3) kJ mol -1 and 41.5(▒2) J mol -1 K -1. Rates increase by many orders of magnitude upon deprotonation of one of the bound waters in complex [ 1] because of the close proximity of a transferable proton that can convert the bound hydroxyl to a bound water. This interconversion allows the oxygen to exchange as a bound water, rather than as a bound hydroxyl, which is slow at near-neutral pH conditions.
Rates of nitrification and ammonium dynamics in northeastern Chukchi Sea shelf waters
NASA Astrophysics Data System (ADS)
Souza, Afonso C.; Gardner, Wayne S.; Dunton, Kenneth H.
Nutrient concentrations are often depleted in surface waters during the late summer open-water period in the northern Chukchi Sea. Yet the rate of re-supply of nutrients to the pelagic environment controls phytoplankton community abundance and productivity, which in turn influences the benthic components of this relatively shallow ecosystem. We measured nitrogen cycling rates at four experimental stations on the northeastern Chukchi Sea shelf in the western arctic. At each station, rates for net NH4+ regeneration, actual NH4+ uptake, and nitrification were measured using 15N isotope enrichment methods with 24-h bottle incubations under both light and dark conditions. Net NH4+ regeneration rates throughout the water column ranged between -0.25 and 0.23 ?mol N L-1 h-1, with highest net positive regeneration occurring under light exposure in surface waters. Actual uptake rates ranged between -0.41 and -0.01 ?mol N L-1 h-1. Nitrification rates (measured at two stations) were generally highest in the sediment overlying waters, ranging between 0.14 and 0.67 ?mol N L-1 h-1, and appear to account for most NH4+ uptake. Calculations of turnover time indicate that N is recycled within one day throughout the water column under natural conditions in the northern Chukchi Sea. Our findings confirm the results of previous studies that suggest a significant portion of surface nutrients on the Chukchi Shelf are products of horizontal advection through the Anadyr Current but also highlight the role of sediment regenerated N in supporting water-column primary production.
Ice-Water Immersion and Cold-Water Immersion Provide Similar Cooling Rates in Runners With Exercise-Induced Hyperthermia
Clements, Julie M.; Casa, Douglas J.; Knight, J. Chad; McClung, Joseph M.; Blake, Alan S.; Meenen, Paula M.; Gilmer, Allison M.; Caldwell, Kellie A.
Objective: To assess whether ice-water immersion or cold-water immersion is the more effective treatment for rapidly cooling hyperthermic runners. Design and Setting: 17 heat-acclimated highly trained distance runners (age = 28 ▒ 2 years, height = 180 ▒ 2 cm, weight = 68.5 ▒ 2.1 kg, body fat = 11.2 ▒ 1.3%, training volume = 89 ▒ 10 km/wk) completed a hilly trail run (approximately 19 km and 86 minutes) in the heat (wet-bulb globe temperature = 27 ▒ 1░C) at an individually selected ōcomfortableö pace on 3 occasions 1 week apart. The random, crossover design included (1) distance run, then 12 minutes of ice-water immersion (5.15 ▒ 0.20░C), (2) distance run, then 12 minutes of cold-water immersion (14.03 ▒ 0.28░C), or (3) distance run, then 12 minutes of mock immersion (no water, air temperature = 28.88 ▒ 0.76░C). Measurements: Each subject was immersed from the shoulders to the hip joints for 12 minutes in a tub. Three minutes elapsed between the distance run and the start of immersion. Rectal temperature was recorded at the start of immersion, at each minute of immersion, and 3, 6, 10, and 15 minutes postimmersion. No rehydration occurred during any trial. Results: Length of distance run, time to complete distance run, rectal temperature, and percentage of dehydration after distance run were similar (P > .05) among all trials, as was the wet-bulb globe temperature. No differences (P > .05) for cooling rates were found when comparing ice-water immersion, cold-water immersion, and mock immersion at the start of immersion to 4 minutes, 4 to 8 minutes, and the start of immersion to 8 minutes. Ice-water immersion and cold-water immersion cooling rates were similar (P > .05) to each other and greater (P < .05) than mock immersion at 8 to 12 minutes, the start of immersion to 10 minutes, and the start of immersion to every other time point thereafter. Rectal temperatures were similar (P > .05) between ice-water immersion and cold-water immersion at the completion of immersion and 15 minutes postimmersion, but ice-water immersion rectal temperatures were less (P < .05) than cold-water immersion at 6 and 10 minutes postimmersion. Conclusions: Cooling rates were nearly identical between ice-water immersion and cold-water immersion, while both were 38% more effective in cooling after 12 minutes of immersion than the mock-immersion trial. Given the similarities in cooling rates and rectal temperatures between ice-water immersion and cold-water immersion, either mode of cooling is recommended for treating the hyperthermic individual. PMID:12937427
Performance of porous ceramic evaporators for building cooling application
Elfatih Ibrahim; Li Shao; Saffa B Riffat
An experimental investigation of porous ceramic evaporators for building cooling has been carried out. Prototypes, classified as low, medium and high porosity prototypes in direct evaporative cooling mode were placed in an experimental duct within an environmental chamber. Performance was measured under different conditions of dry bulb temperature (DBT), relative humidity (RH), supply water pressure, and layout within the duct.
Structuring of polymer solutions upon solvent evaporation
NASA Astrophysics Data System (ADS)
Schaefer, C.; van der Schoot, P.; Michels, J. J.
The morphology of solution-cast, phase-separated polymers becomes finer with increasing solvent evaporation rate. We address this observation theoretically for a model polymer where demixing is induced by steady solvent evaporation. In contrast to what is the case for a classical, thermal quench involving immiscible blends, the spinodal instability initially develops slowly and the associated length scale is not time invariant but decreases with time as t-1 /2. After a time lag, phase separation accelerates. Time lag and characteristic length exhibit power-law behavior as a function of the evaporation rate with exponents of -2 /3 and -1 /6 . Interestingly, at later stages the spinodal structure disappears completely while a second length scale develops. The associated structure coarsens but does not follow the usual Lifshitz-Slyozov-Wagner kinetics.
Measurements of Flow Rate and Trajectory of Aircraft Tire-Generated Water Spray
NASA Technical Reports Server (NTRS)
Daugherty, Robert H.; Stubbs, Sandy M.
An experimental investigation was conducted at the NASA Langley Research Center to measure the flow rate and trajectory of water spray generated by an aircraft tire operating on a flooded runway. Tests were conducted in the Hydrodynamics Research Facility and made use of a partial airframe and a nose tire from a general aviation aircraft. Nose tires from a commercial transport aircraft were also used. The effects of forward speed, tire load, and water depth on water spray patterns were evaluated by measuring the amount and location of water captured by an array of tubes mounted behind the test tire. Water ejected from the side of the tire footprint had the most significant potential for ingestion into engine inlets. A lateral wake created on the water surface by the rolling tire can dominate the shape of the spray pattern as the distance aft of the tire is increased. Forward speed increased flow rates and moved the spray pattern inboard. Increased tire load caused the spray to become less dense. Near the tire, increased water depths caused flow rates to increase. Tests using a fuselage and partial wing along with the nose gear showed that for certain configurations, wing aerodynamics can cause a concentration of spray above the wing.
Simulating evaporation from short-rotation forest: variations within and between seasons
NASA Astrophysics Data System (ADS)
Persson, Gunn; Lindroth, Anders
A physically based soil water model was applied to a fertilized and irrigated short-rotation willow stand on a clay soil. The model is based on an extension of Richards' equation, and the water retention curve and saturated conductivity are determined by analyses of soil cores. The Penman-Monteith combination equation is used to calculate potential daily transpiration, soil evaporation and potential interception evaporation. Daily meteorological data are used as driving variables. Evaporation, estimated by the energy balance/Bowen ratio method, and soil-water tension measurements made over several years, were used to verify the model. Measured evaporation of water intercepted by the vegetation over 1 year was also compared with simulated monthly values. Good agreement was found between simulated evaporation and evaporation determined from Bowen ratio measurements. The cumulative seasonal evaporation exceeded the Penman open water evaporation by up to 31% in 3 years out of 4; it ranged between 416 and 584 mm for the period from May through October. On a mean seasonal basis, transpiration was 66%, soil evaporation 23% and interception evaporation 11% of total evaporation. The monthly interception evaporation comprised 5-23% of precipitation. The study period showed interannual variations attributable to variation in climate (including irrigation) as well as to stand age and development. This indicates that the model is quite general in many respects; it is tentatively suggested that it be used for accurate simulation of water balance components of short-rotation forest on a clay soil in this type of climate.
Measurements of the rate of the uranium-water vapour reaction
NASA Astrophysics Data System (ADS)
Ritchie, A. G.; Greenwood, R. C.; Randles, S. J.; Netherton, D. R.; Whitehorn, Miss J. P.
The rate of the uranium-water vapour reaction has been measured between 30 and 80░C. The measured reaction rate obeys the rate equation: k = 3.0 ū 10 9r {1}/{2} exp(-15.5 kcal/RT) mg U/cm 2 h = 4.0 ū 10 8r {1}/{2} exp(-15.5 kcal/RT) mg weight gain/cm 2 h, where r is the fractional relative humidity. This rate equation agrees remarkably well with the literature equation which was derived from much more limited experimental evidence and so the present equation is preferred.
NSDL National Science Digital Library
WGBH Educational Foundation
In this outdoor water activity, learners explore evaporation by painting with water and tracing puddles. Learners will discover that wet things become dry as the water evaporates. This activity is part of the curriculum Explore Water, related to Peep and the Big Wide World, a preschool science series on public television. The activity starts on page 36 of the PDF.