Thermohydraulic performance evaluation of solar air heater with roughened absorber plate

Abstract

Solar air heaters, having artificially roughened absorber plate exhibit improved thermal and thermohydraulic performances. In an outdoor experimental investigation, thermal and thermohydraulic efficiencies of multiple v-rib roughened solar air heaters were evaluated for Reynolds number range of 3000 to 15100. It has been observed that use of multiple v-rib type of roughness on the underside of the absorber plate of a solar air heater resulted in 51 per cent improvement in thermal efficiency along with three fold increase in frictional losses as compared to conventional solar air heater having smooth absorber plate. Effective efficiency of the multiple v-rib roughened solar air heaters has been found to be about 1.5 times that of conventional solar air heaters. Effective efficiency of multiple v-rib roughened solar air heaters tested under outdoor and indoor conditions has been found to differ between 12 and 22.5 per cent