MANUFACTURE OF HEAT ABSORPTION SURFACE FOR SOLAR HEAT COLLECTOR

PURPOSE:To contrive to simplify the manufacture and to reduce the production cost by a method wherein a thin layer of substance, which chemically changes by heating into a constituent member having a large rate of absorption of solar heat, is provided on a substrate with a small rate of thermal radiation and, after that, heated. CONSTITUTION:Firstly, for example, a stainless steel substrate is degreased and cleansed. Secondary, the surface of the substrate is sprayed with suspension of iron hydroxide slowly enough not to cause dripping off. The suspension is the aqueous mixed solution of ferrous hydroxide[Fe(OH)2O]and ferric hydroxide [Fe(OH)O], the ratio of content contents of which is prepared to be 1:2 by molar fraction, dispersed in water. The thickness of the thin film obtained by spraying is rendered to be not more than about 10mum. After being thoroughly dried, the thin layer is heated in air, for example, at 400 deg.C for 30min so as to chemically change the iron hydroxide thin layer into the triferric tetroxide (Fe3O4) layer, resulting in turning to be the absorption surface having a large rate of absorption of sunbeams.