Theoretical and Experimental Comparison of Box Solar Cookers with and without Internal Reflector

Abstract

Box solar cookers are commonly built with internal sheet metal painted black as an absorber. In order to increase the performance, a design which incorporates internal reflection is proposed in this paper. The aim of this paper is to report comparisons made between box solar cookers with and without internal reflector. Theoretical modelling of the two types of cookers has been made by considering the radiation, convection and conduction heat transfer employing the thermal network method. The theoretical analysis made was based on steady state heat transfer analysis of the cookers. Experimental comparisons were also made on two cookers having the same aperture area and made from the same type of materials except the internal absorber. The tests were made as per the American Society of Agricultural Engineers (ASAE) procedure.The result of the theoretical analysis predicts that the performance will be higher in the cooker with internal reflector than the same cooker without reflector. The steady state analysis shows that for the cooker with reflection the temperature of the bottom absorber plate is higher than the cooker without reflector. Similarly, results of dry test and water boiling test show better performance by the cooker with reflector. The standard stagnation temperature and the cooking power were higher in the cooker with reflector as compared to the cooker without reflector. In conclusion, the performance of box solar cookers can be enhanced by making appropriate angle side walls of the absorber and providing internal reflection.