Solar air heaters are generally used for low to moderate thermal energy requirements. These systems are cheap and easy to maintain, but due to the disadvantage of low thermal efficiency and because of low convective heat transfer coefficient between the absorber plate and the energy extracting carrier fluid, air. Several methods have been proposed for the enhancement of heat transfer coefficient of such collectors. Use of porous packing material in the collector duct is one of the methods. It considerably enhances the energy collection rate by increasing heat transfer rate between a carrier...