Thermal analysis of the defrost cycle in a domestic freezer

This paper presents a thermal analysis of a defrost cycle in order to design more efficient defrosting mechanisms in household refrigerators and freezers. A simple heat transfer model has been developed to determine energy flows from a defrost heater across various components of a refrigerator/freezer. The study measures power consumption and temperatures of a single temperature vertical empty freezer (in normal operation with and without defrosts) to determine the heat distribution from the radiant type electric defrost heater and its effect on power consumption. The surface temperature of the defrost heater was measured to be 520 °C for minimal frost and 560 °C for heavy frost. The efficiency of a defrost heater was measured to be 30.3%, while power consumption of the freezer was found to increase by 17.7% due to automatic defrost.