Hot gas bypass defrosting with auxiliary heat source in household refrigerators

Frost is inevitable in air-cooled household refrigerators. To maintain the performance of the refrigeration system and food storage quality, additional power input is required to melt the ice periodically. Hot gas bypass defrosting featured high defrosting efficiency, however, suffered insufficient defrosting power at low ambient temperatures, leading to rare application of this technology in household refrigerators. To mitigate this challenge, a novel cost-effective hot gas bypass defrosting system with an auxiliary heater wrapped along the hot gas bypass loop was proposed, and its performance was thoroughly investigated in this paper. Experimental results showed that the defrosting efficiency was 0.8 at an ambient temperature of 32 °C, which was much higher than that of baseline electric defrosting of 0.3. At 20 °C, the new defrosting system with 80 W additional power input in the auxiliary heater successfully melted all frost within 35 min, while the baseline hot gas bypass defrost system without additional heat input could not melt all frost even after 60 min. To further investigate the effects of ambient temperature, compressor speed, and auxiliary heating power, a mathematical model was established and validated by experimental data. The simulated results suggested that it was more efficient to supply more heat from the auxiliary heat source than from the compressor.