CFD simulation of thermal performance of hybrid oil-Cu-Al2O3 nanofluid flowing through the porous receiver tube inside a finned parabolic trough solar collector

Abstract

In this study, we perform numerical simulations to investigate the thermal and flow characteristics of a parabolic trough solar collector equipped with a porous receiver tube and internal longitudinal fins. The heat transfer medium is a synthetic oil-Cu-Al2O3 hybrid nanofluid. We examine the thermal characteristics of the nanofluid in response to variations in several system parameters. We find that at Reynolds numbers between 5 × 103 and 5 × 105, increasing the volume fraction of Cu nanoparticles can increase the temperature gain at the exit of the receiver tube by 6.4%. Furthermore, the temperature gradient in the cross-section of the collector increases as the direct normal solar irradiance decreases. Increasing the volume fraction of Cu and Al2O3 nanoparticles by 0.02 at low Reynolds numbers is found to increase the thermal efficiency by 12.2% with 5.2% adverse effects on the friction factor; Cu nanoparticles are found to be three times more effective than Al2O3 nanoparticles. For Darcy numbers between 0.01 and 0.1, we find that higher permeability has only a minor adverse effect on the thermal efficiency, but can reduce the friction factor to a third of its original value. These findings can be used to improve the efficiency of solar collectors.