Reducing cabinet temperature rise during electric heater defrosting of frost-free refrigerators by using a special fan cover to block heat infiltration

Electric heater defrosting (EHD) is effective in removing frost on the evaporator and in recovering capacity/coefficient of performance (COP) for frost-free refrigerators. This study proposes a method of reducing the temperature rise in the freezing cabinet (FC) during the EHD process. Based on the idea of blocking the infiltration passage of the heater-generated warm air, a special cover was designed for the axial fan of the evaporator; the cover was kept open during cooling cycles to supply cold air into cabinets normally, but was forced closed during EHD cycles so that defrost heat was prevented from infiltrating into the FC. Results show that defrost duration was shortened by 3.4%, FC temperature rise within the defrost cycle declined by 1.6 °C, and the overall energy consumption for defrost and recovery cycles altogether was reduced by 1.9% with the fan cover. Further optimization could be made by adjusting the delay of the fan starting after defrosting.