A note on frosting of heat pump evaporator surfaces

Abstract

This paper is concerned with frosting of cryogenic surfaces with particular reference to the effects on heat transfer to the evaporator coil of an air-to-air heat pump. The analysis of a frosted fin model shows the insulation resistance of frost in such a geometry is negligible. The loss of heat transfer performance is attributed to changes in the air-side coefficient as a result of geometrical blockage by the frost layer. These findings underline the importance of frost thickness rather than its density and thermal conductivity, and the fin system geometry in relation to the evaporator fan characteristics.