Performance evaluation of a novel parabolic trough solar collector with nanofluids and porous inserts

Abstract

In this study, the thermal performance enhancement of parabolic trough solar collector (PTSC) with porous strips and nanofluid is visited computationally. The research investigates the effect of variation of the geometry angle of the porous protrusion and nanoparticles on the thermal performance of PTSC system. The tests are performed by varying geometry angles from 5° to 15°, porosity from 0 to 0.7, solar radiation from 400-1000 W/m2, Reynolds number (Re) of 477–1906, and at a fixed height-to-diameter (h/D) ratio of 0.25. The study is also extended by considering copper oxide (CuO) and aluminum oxide (Al2O3) based nanofluids with a volume fraction of 3–7 %. Results indicate the presence of nanofluids increases the average Nusselt number ratios by up to 51.39 % compared to water. The research also emphasizes that adding porous obstacles results in a 9.86% enhancement in the average Nusselt number compared to a non-porous version. The thermal performance factor is found to be augmented by 5.32 % and 5.75 % with a change in geometry angle from 5° to 15° for Al2O3 and CuO nanofluids, respectively. Further, at a geometry angle of 15°, h/D=0.25, Re = 1428, and solar radiation of 800 W/m2, the highest thermal performance factor of 1.368 is obtained for CuO nanofluids. With the change in geometry angle from 5° to 15° with Al2O3 and CuO nanofluids, the thermal efficiency increases by 7.73 % and 8.59 %, respectively. At an h/D ratio of 0.25 and a geometry angle of 15°, the absorber tube provides maximum thermal efficiency of up to 59.75 % and 62.96 %, respectively, with a 7 % volume fraction of Al2O3 and CuO nanofluids.