Thermo-hydraulic and exergetic performance of a cost-effective solar air heater: CFD and experimental study

An experimental and computational fluid dynamics (CFD) study is carried out to investigate the impact of secondary flow strengthening the thermo-hydraulic performance of discrete multiple inclined baffles in a flat plate solar air heater (SAH) with semi-cylindrical sidewalls. Initially, for a fixed relative baffle height (R-h = 0.1), the relative baffle pitch (R-p) for continuous baffles is varied in the range of 0.6-1 to obtain the optimum baffle pitch for 6000 < Re < 14000. The impact of gaps at leading, trailing, and both leading and trailing apices are studied as three different configurations with the optimum R-p. A maximum thermo-hydraulic performance of 2.69 is obtained for the gap at the trailing apex. The proposed design has a higher collector efficiency, 55-70%, compared to the ribbed rectangular SAH design exhibiting 30-55%.With lower exergy losses, the present SAH design has higher exergetic efficiency (1.5%-2.2%)than ribbed rectangular SAH (0.9%-1.7%) for the range of Restudied. Further, at low Re, the present SAH design has a higher coefficient of performance, indicating that it is cost-effective than ribbed rectangular SAH designs. (c) 2021 Elsevier Ltd. All rights reserved.