A Numerical Analysis Of The Effects Of Nanofluid And Porous Media Utilization On The Performance Of Parabolic Trough Solar Collectors

The use of porous receiver tubes and nanoparticle addition into the heat transfer fluid (HTF) are two effective strategies to improve the thermal performance of parabolic trough solar collectors (PTC). In the present study, a three-dimensional CFD method is used to model heat transfer behavior and flow characteristics of the HTF and investigate the effects of porous layer placement, its properties, and nanoparticle addition on the collector efficiency. The impacts of both operating conditions and geometry configurations including inlet velocity, receiver tube diameter, nanoparticle volume fraction, solar elevation angle, and porous zone properties such as permeability, on Nusselt number, friction factor (f), performance evaluation criteria (PEC), and thermal efficiency are discussed. It is shown that nanoparticle addition leads to thermal efficiency improvement such that by increasing the Cu nanoparticles volume fraction to 0.015, 12% increase in Nu and 1.2% increment in eta is observed for the case with Gr = 10(7). Furthermore, for collectors with half-porous receiver tubes, both Nu and f respectively become up to 10.6 and 5 times higher than their corresponding values for non-porous receiver tubes. Besides, for whole-porous receiver tubes, these ratios are approximately raised to 25 and 30, respectively. Hence, the utilization of porous receiver tubes significantly changes the performance of PTCs.