Experimental analysis of heat transfer in the flow channel duct of solar air heaters (SAHs)

Abstract

This paper presents an experimental comparative study on the thermal performance and heat exchange of two single pass solar air heaters models (SAHs); we have proceeded to reversing the flow direction in the solar air heater. Initially, to determine the best performing model and to improve the efficiency factor of the SAH. Secondly, to evaluate the convective heat transfer coefficient of both models, named: N-1 and N-2. The indices (1) and (2) indicate, respectively, that the air was blown up or blown down in the channel duct of the SAH. Therefore, we have compared between the efficiencies, the convective heat transfer coefficient, Nusselt number curves and the distribution of air temperatures in the channel ducts of both solar air heaters. Both collectors were designed, constructed and tested in the University of Biskra (Algeria) in a stand facing south at an inclination angle equal to the local latitude. The results show that N-2 model (air blown down) is more efficient than N-1 model (air blown up), and the improvements in the heat exchange due to this technological solution are about 10-20%.