Defrost characteristics and performance improvement of electric heaters in R600a frost-free refrigerators

• Published in: Thermal science and engineering progress Vol. 58; p. 103219
• Main Authors: Zhang, Shuping, Yang, Zhao, Wang, Yiping, Zhao, Yanfeng, Shu, Yue, Zhao, Xing, Sun, Bin, Wang, Guoqing, Xie, Teng
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2025
• Subjects: Defrosting Efficiency; Defrosting Synchronization; Electric Heater; Temperature Uniformity; Defrosting Synchronization; Electric Heater; Defrosting Efficiency; Temperature Uniformity
• ISSN: 2451-9049
• DOI: 10.1016/j.tsep.2025.103219

•Defrosting on the evaporator is asynchronous from bottom to top.•The distributed heater improves defrosting by combining local and global heating.•Optimizing heater power distribution improves defrosting performance.•Defrosting is optimal with a 150 W global heater and a 50 W local heater. Defrosting remains a vital topic in refrigeration systems, with electric heater defrosting being widely adopted due to its simplistic design and ease of operation. However, the prevalent electric heater defrosting methods confront the issue of low energy utilization efficiency. This study uses a frost-free refrigerator charged with R600a as the research subject and employs an experimental approach to investigate the defrosting characteristics. To enhance the synchronicity of defrosting across different heights on the evaporator surface, the distributed electric heater defrosting (DHD) method is introduced. The distributed electric heater is composed of both local and global heaters. The impact of the installation height of the local heater on defrosting performance is also explored. The results show that installing the local heater at the upper section of the evaporator achieves higher defrosting efficiency and a more uniform temperature. Moreover, power allocation for the distributed electric heater is studied, and the optimal performance is achieved when the global heater is set at 150 W and the local heater at 50 W. This arrangement outperforms the original method, reducing the operational time of the electric heater by 15 min, decreasing energy consumption by 0.05 kW·h, enhancing the defrosting efficiency by 10.67 %, and reducing the evaporator surface’s maximum temperature by 16.1℃. This improvement enhances defrosting performance. Better temperature uniformity can effectively prevent local overheating, improve defrosting synchronization, and enhance both safety and energy efficiency. The research provides references for optimizing the defrosting performance of electric heaters in refrigeration equipment, ensuring efficient and stable operation.