Numerical study of parabolic trough solar collector’s thermo-hydraulic performance using CuO and Al2O3 nanofluids

Abstract

The current study aims to boost the thermal and hydraulic performance of a parabolic trough solar collector by modifying the absorber tube with a porous obstacle insertion. The research investigates how porous media and nanoparticles together influence the system's thermal performance, considering factors like outlet temperature, average Nusselt number, average friction factor, thermal performance factor, and thermal efficiency at different mass flow rates. To achieve better thermal performance, the base fluid, water, is substituted with Copper Oxide (CuO)-water and Aluminum Oxide (Al2O3)-water nanofluids at concentrations ranging from 3% to 7% by volume. The experiments are conducted at 800–1000 W.m-2 heat flux on the outside tube surface. The finite element method discretizes the governing equations for 3-D fluid flow simulations conducted in COMSOL Multiphysics 6.1 software. The simulation is carried out considering four altered rates of mass flow, ranging from 0.015 kg.s−1 to 0.060 kg.s−1. The findings show that at a Reynolds number of 1428 and a 7% volume concentration, the maximum thermal performance factor recorded is 1.97 and 1.99 for Al2O3 and CuO nanofluids, respectively. Additionally, the absorber tube achieves maximum thermal efficiency of up to 77.93% and 79.03%. Also, the augmentation in the average Nusselt number ratio is 26.27% and 36.74% when using Al2O3 and CuO nanofluids, respectively, with the tube height-to-diameter ratio (h/D) set at 0.42. The average friction factor ratio was reduced by 2.9% using CuO nanofluids compared to Al2O3 nanofluids. Thermal efficiency was enhanced by 7.2% using a porous obstacle insert in the parabolic trough solar collector system compared to a non-porous system.