The effect of air absorption coefficient on the performance of flat plate solar collectors

Solar collectors compared to standard heating systems can provide significant savings in energy consumption. This paper concerns with analyzing the coupled radiative and natural convective heat transfer in solar flat-plate collectors, when the collector cavity is considered as a radiative participating media. First, an appropriate model for analysis of the thermal behavior of the collector is validated using reliable results in the literature. The discrete ordinates method is used for the radiative analysis and thermal analysis of a flat-plat solar collector, with real specifications and by considering water channel under the absorber, in summer solar conditions and for a wide range of air absorption coefficients are performed. According to the results, by increasing the absorption coefficient of the air, the temperature of absorber plate is decreased while the temperature of the air is increased. The effect of the absorption coefficient on the air temperature is higher than the temperature of the absorber plate. Also, by decrease in the absorber temperature, the outlet water temperature, that is approximately equal to the temperature of the absorber plate, is decreased.