Solar air heaters for low and moderate temperature applications

Abstract Solar air heaters can be used for many purposes, including crop drying, space heating, and for regenerating dehumidfying agents. Because of their inherent simplicity, they also offer the possibility of providing cheap, low-grade heat, at temperatures up to 100 deg F above ambient. There are many possible designs for solar air heaters, from the point of view of both materials and configurations. These in turn lead to a variety of costs and collection efficiencies. A design study has been made of three basic construction types, to which various modifications are made. These modifications include various heat-transfer coeficients between the absorber plate and the air stream, selective and non-selective surfaces on the absorber plate, and natural convection barriers between the plate and ambient air. Collection efficiencies have been computed for the various designs for a range of operating temperatures. The calculations show that these heaters can be built to provide air at 100 deg F above ambient, at collection efficiencies of 50 percent or more.