Experimental investigation on thermal efficiency augmentation of solar air heater using copper wire for discrete roughened absorber plate

Abstract

Solar air heaters are used to heat the air, however their thermal efficiency is low due to the weak thermal conductivity between the air and the absorber plate. The thermal efficiency of solar air heaters can be improved by artificially roughening the absorber plate, which elevates the temperature of the plate and results in maximum thermal losses to the atmosphere.The performance of solar air heaters (SAH).is improved by using the largest range of solar flux and discharging heat energy from the absorber plate through air working fluid. In the outdoor experiment described in this article, artificial rib elements were added to the surface of the absorber plate to increase the heat transfer coefficient. In a recent study and outdoor experimental laboratory work done in view of the investigation of heat transfer coefficient and thermal efficiency parameters, a novel discrete double arc reverse form artificial roughness has been developed on the underside of the absorber plate. The roughness range of parameters used in the outdoor work are channel aspect ratio (W/H) of 8, relative roughness pitch (p/e) of 6.67–8.33, relative roughness height (e/Dh) of 0.027, angle of arc (α) of 60° and Reynolds number (Re) of 3000–14000, The test was run from morning 11 am until afternoon 2 pm, and the solar heat flux (I) was between 850 and 890 W per square metre. Under comparable working conditions, the artificially roughened channel performs well in comparison to the smooth channel. Over the smooth channel, the maximum ranges of thermal efficiency and heat transfer coefficient were noted to be 288 % and 129 %, respectively.