Analysis on Optimal Thermohydraulic Performance of Solar Air Heater Having Multiple V-shaped Wire Rib Roughness on Absorber Plate

Abstract

The use of artificial roughness on the underside of the absorber plate is an effective and economic way to enhance the heat transfer from the collector to the air in a solar air heater duct. This paper presents the analysis on thermal and thermohydraulic efficiency also called “effective efficiency” of solar air heater having multiple v-shaped wire rib roughness underside of the absorber plate. The mathematical equations are analytically derived and solved by developing a computer program in MATLAB code in order to analyze the effect of various ambient, operating and  design parameters on the thermal efficiency and effective efficiency (based on the net gain after taking account of the pumping power) of such air heaters. The study shows substantial enhancement in thermal efficiency over solar air heater with plane ones. The thermal efficiency enhancement is also accompanied by a considerable increase in the pumping power requirement due the increase in the friction factor. The optimum design and operating conditions have been determined on the basis of thermohydraulic considerations. It has been found that, the systems operating in a specified range of Reynolds number shows better thermohydraulic performance depending upon the insolation. A relationship between system and operating parameters that combine to yield optimum performance has been developed.