Experimental study on a low-heat-capacity non-uniform power distribution defrost heater for frost-free refrigerators.

Refrigerators, among the most widely used refrigeration devices, face efficiency declines due to frost buildup on evaporators during repeated cooling cycles. Currently, steel tube defrost heaters (STDH) are employed to tackle this issue. However, the high heat capacity of the STDH results in slow heat transfer, leading to significant energy consumption for defrosting, which accounts for nearly 12.0 % of the total system energy consumption. To address this issue, this paper proposes a low-heat-capacity non-uniform power distribution defrost heater (LHNPDH). The LHNPDH features electric heating wires wound around the outer surface of the heater, enabling rapid transfer of defrosting heat. In addition, the power distribution of the heater can be adjusted across different regions by varying the winding density of the heating wire, thereby achieving on-demand defrosting. The experimental results demonstrate that, compared to STDH, LHNPDH can reduce the total defrosting cycle time by 25.1 %, decrease the temperature rise in the freezer compartment (FC) by 2.7 ◦C, lower the maximum FC temperature by 4.1 ◦C, and reduce defrosting energy consumption by 28.6 %. Therefore, the LHNPDH developed in this study can utilize and distribute defrost heat more rationally and efficiently, ultimately achieving an effective energy saving of 2.6 % for the refrigerator.