Thermal performance and heat transfer analysis of arc shaped roughened solar air heater – An experimental study

Abstract

In the present study, thermal performance and heat transfer of arc shaped roughened solar air heater (SAH) with apex up and apex down air flow has been examined through experiments. To achieve this aim, experiments were conducted with mass flow rate from 0.007 to 0.022 kg/s, and variations of mass flow rate on the thermal efficiency and outlet temperature were examined. The arc shape roughness with relative roughness pitch, relative roughness height, rib roughness and arc angle were 10, 0.0395, 2.5 and 60° respectively have been taken. It has been observed that the thermal efficiency increases with increase in mass flow rate of air, for the same mass flow rate the average enhancement of apex upstream flow is 6.9% higher than the apex downstream flow. The maximum efficiency obtained for apex up and apex down air flow arc shaped roughened SAH are 73.2% and 69.4% respectively, at mass flow rate 0.022 kg/s. Also, it has been observed that the heat transfer of apex up arrangement performs 33.2% better as compared to apex down. The above result reveals that apex up air flow wire rib roughness absorber plate is more efficient than the apex down roughness solar air heater.