A Basic Study of Defrosting of Heat Exchanger.

Abstract

This paper is concerned with the experimental study of defrosting of a row heat exchangers with fins. It mainly is investigated the effect of fin pitches on the frosting amount, residual amount of melt water in fins, defrosting thermal efficiency and nonsteady defrosting mean Nusselt number. Frosting time is about three hours in this experiment at which air does not flow in fins due to the choking of fins with frost. Dimensionless frosting amount increases with increasing fin pitch. This also means that frosting easily chokes the heat exchanger with small fin pitch. Dimensionless residual amount of melt water is comparatively small when the fin pitch is larger than 3mm. Defrosting thermal efficiency, η, increases with increasing fin pitch. Time averaged nonsteady defrosting mean Nusselt number, Nu, during defrosting is not largely affected by fin pitches, but is about 1.5 times larger than the results of heat transfer in the pipe with a constant wall temperature and laminar steady state by Hausen.