Energy Saving in Domestic Refrigerators by an Adaptive Defrost Method

Frost free domestic refrigerators include a refrigeration defrost system, in which an electromechanical timer is used to energize a defrost heater after a pre-determined compressor ON time to melt frost built on the evaporator coils. In domestic refrigerators, defrosted water evaporation can be a fundamental problem especially in tropical countries with hot and humid ambient conditions. A new adaptive method for defrosting an evaporator in a domestic refrigerator system is presented in this paper. In this method, parameters namely open door time and compressor ON time have been considered effective on defrost operation. The refrigeration cycle includes pull down time, cooling operation, prechill mode, defrost hold OFF, post prechill mode, defrost mode, Dwell mode, and post Dwell mode.In this case study top mounted freezer (TMF) domestic refrigerator, for each 6 hours compressor ON time, defrost is performed for a fixed pre-determined 20 minutes. The results showed that if this method is used in domestic refrigerators, it can reduce energy consumption about 13% in comparison to fixed defrost cycles.