Separation Phenomenon between a Frost Layer and a Cooling Surface Using Sublimation under Low Temperature Forced Convection

Abstract

Frost formation in heat exchangers is an important problem because frost lowers energy efficiencies of refrigeration and air conditioning systems. In this study, we investigated frost formation on a flat plate under forced convection with air temperatures of -45 to -5 ℃. After frost growth for 3 to 130 min, the cooling surface was heated stepwise below the melting point of frost and the occurrence of a separation phenomenon between the frost layer and the cooling surface was verified. It is conjectured that sublimation of the frost layer was caused by the heated plate and then mass transferred to the upper part of the frost which is cooled by low temperature air. This phenomenon is thought to reduce adhesion of frost, thereby causing separation. This paper introduces the separation phenomenon and the boundary conditions under which it occurs. It is expected that this phenomenon will become an effective defrost method for air coolers in cold storage rooms.