Gas radiative effects on gas-filled flat plate solar collectors

Abstract

A standard thermal solar collector can be used for both hot water production and air heating purposes. Gas-filled solar collectors represent a new emerging design approach with enhanced characteristics. In this research, numerical modeling is utilized to study radiative effects of the participating gases on the performance of solar collectors. The coupled radiative–convective heat transfer in the solar collector is considered and the collector cavity is considered as a radiatively participating medium. The finite volume method has been adopted to solve the governing equations and discrete ordinates method is used for radiative transfer. After validating the model used in this study, it is used to obtain the heat transfer characteristics of a flat-plate solar collector with real solar conditions of the city of Kerman, Iran, in summer at a wide range of air absorption coefficients. According to the results, by increasing the absorption coefficient of the air, the temperature of the absorber plate is reduced and the air temperature is increased, but the increase of air temperature is much higher than the reduction of absorber temperature. Hence, it is concluded that it is possible to use participating gases in the solar air heaters to enhance the performance of the collector.