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Eulerian-Eulerian model for photothermal energy conversion in nanofluids

In this research photothermal energy conversion in nanofluids was numerically studied using a CFD model. A Direct Absorption Collector (DAC) of cylindrical shape with incident light on one of its surfaces was adopted for the simulations. The Eulerian two-phase transient model included the volumetric absorption of light, losses to the surroundings and the Brownian motion. The simulation results were validated with experimental data, demonstrating modest discrepancies. The model was studied parametrically, altering particle volume fraction, collector height and surface transparency. We found that: the efficiency drops by 43% when the absorber height is reduced from 7.5 to 1.0 cm for 2.5 ppm; the maximum efficiency was 67% at 50 ppm (1 cm absorber); the efficiency of the DAC with nanofluid is 20% greater than the efficiency for the surface absorber; natural convection in the collector improves the efficiency by 7%.