Distributed heaters to reduce temperature rise in freezing cabinet during defrost process and its overall energy effect for a frost-free refrigerator

In most frost-free refrigerators with a bottom defrost heater (BDH) for the evaporator, the mismatch between bottom-up dissipation of defrost heat and distributed coverage of frost extends defrost duration, which promotes defrost heat intrusion into freezing cabinets (FCs) and dominates temperature rise there. The objective of this article is to propose a method of reducing FC-temperature rise during defrost cycles for frost-free refrigerators. Based on the idea of better matching defrost heat dissipation and frost coverage, distributed defrost heaters (DDHs) were utilized by adding an extra heater (60 W) in the middle of the evaporator besides the original bottom one (180 W). Then, defrost performance was compared experimentally between BDH and DDHs cycles. Results show that DDHs resulted in 1.1 °C decline in FC-temperature rise with 3.3 min reduction in defrost duration. Moreover, the extra heater power hardly raised the overall energy consumption of the refrigerator, because the lower FC temperature after defrost reduced the energy consumption in the following recovery cycle, which compensated for the increase in the defrost cycle. Therefore, the utilization of DDHs is an efficient method in improving defrost performance and food storage quality.