defrost heater, evaporator, refrigerators, energy consumption
In a previous study an experimental testing apparatus was constructed and used to measure the defrosting efficiency of different heaters working under different control strategies. Based on the results obtained two defrosting heaters (one calrod and one distributed) and two control strategies (constant power and steps mode) were selected for this study. In the original mode the power was held at 160 W for 17.0 and 19.3 min for the distributed and the calrod heaters, respectively. In the steps mode the power was gradually reduced from 160 to 20 W, and the defrost length was set to 28.5 and 22.3 min, respectively, for the distributed and calrod heaters. Energy consumption tests were carried out following the ISO and AHAM standards, using the same top-mount frost-free refrigerator. Changes were implemented in the electronic board in order to vary the power and length of the steps. A glass window was installed in the rear wall of the refrigerator to visually monitor the defrosting process. A 4.3% drop in the energy consumptions obtained applying the two standards was achieved by replacing the calrod heater and the constant power mode with the distributed heater and the steps mode. Clogging tests were also carried out, using an automatic door-opening device to check the robustness of the different defrosting systems.