COLLECTION CHARACTERISTICS OF A SOLAR AIR HEATER WITH BUILT-IN NET

A solar ah heater with a built-in net was proposed and the collection characteristics were experimentally investigated. Eight kinds of metal lic nets, which had different transmissivity and opening fraction, wer e configured parallel in the space between the transparent cover plate and absorber. The temperature distribution within the air layer and p ressure drop were measured, and the effects of the net transmissivity and opening fraction on the temperature distribution, collection effic iency and pressure drop were examined. When the metallic net was inser ted in the solar air heater, the temperature distribution within the a ir layer was quite different and the collection efficiency became 16 t o 35 % higher than those of conventional solar air heaters and solar a ir heaters without a net. The collection efficiency had a maximum agai nst the net transmissivity. By changing the net setting position, the pattern of temperature distribution was much affected while the collec tion efficiency was hardly affected. The pressure drop in the present solar air heater was higher than those in the conventional solar air h eater and the solar air heater without a net, and had a maximum agains t the net transmissivity, i.e. the net opening fraction.