Transient Analysis for a Double-Pass Solar Collector With and Without Porous Media

The double-pass solar collector with porous media in the lower channel provides a higher outlet temperature compared to the conventional single-pass collector. Therefore, the thermal efficiency of the solar collector is increasing. The solar collector can be used for a wide variety of applications such as solar industrial process heat and solar drying of agricultural produce. A theoretical model has been developed for the double-pass solar collector. An experimental setup has been designed and constructed. Comparisons of the theoretical and the experimental results have been conducted. Such comparisons include the outlet temperatures and thermal efficiencies of the solar collector for various design and operating conditions. Close agreement has been obtained between the theoretical and experimental results. In addition, heat transfer and pressure drop relationships have been developed for air following through the porous media. The porous media has been arranged with difference porosities to increase heat transfer, area density and the total heat transfer rate. The heat transfer coefficient and friction factors are strong function of porosity.