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An Innovative Thermal Analysis Model for Continuous Operation of a Solar Collector


 Heat pipe evacuated tube solar collectors (HPETCs) are a type of solar collectors widely used in solar water heating (SWH) technologies. In order to optimize the design of SWHs, understanding the heat transfer phenomena in HPETCs is of paramount importance. The complexity of the heat transfer processes involved in modelling a collector’s performance render direct numerical simulations (DNS) computationally cumbersome. In this work, a novel hybrid numerical method is employed in order to simulate the thermal behaviour of HPETCs, both during day and night time operation. This method is comprised of a previously developed resistance network based proper orthogonal decomposition (RNPOD) method for simulation during operation hours were solar irradiation values are greater than zero; after which, an in-house code based on Lattice Boltzmann method (LBM) has been utilized for simulation when irradiance is zero. This hybrid method is able to reduce simulation time and take into account the ambient working conditions of the collector and therefore, provide an accurate assessment of the temperature distribution inside the collector during the entirety of its operation during a full working cycle. The obtained results of this study are cross-validated with the previous experimental work of the authors, illustrating that the model is able to predict the peripheral temperature distribution with an average error of less than 10%.