Abstract
Five different selective surfaces coated with oxides of nickel, manganese, chromiUm, lead, am iron on galvanized iron substrate by electro-deposition or chemical method were studied for properties such as absorptivity, emissivity, temperature rise of the surface and stagnation air temperature. The properties of the surfaces which may change due to weather conditions were predicted by: subjecting the collector surfaces to accelerated tests. The best among them was found to be black nickel, followed by manganese, chromium, lead, and iron oxides. Black nickel and manganese surfaces were included in the solar drying system and their drying air temperatures recorded. With selective surfaces, a temperature rise between 250to 4sOC was observed depending on the surface (either manganese oxide or nickel oxide)., Hence high mo~sture content food crops can be dried in less than half the time using selective surface