针对冷冻冷藏库传统除霜方法高能耗、冷库温湿度波动大等缺陷，通过设计系统除霜结构，完善控制策略，研发了一种智能除霜方法。复合加热循环除霜采用时间—压差联合智能控制策略界定最佳除霜点，配备排管辅助制冷技术，基于欧姆龙PLC高精度控制系统使各设备协同完成除霜过程。对复合加热循环除霜系统进行试验研究，对比分析不同除霜方法的工作性能及能耗情况。结果显示：相比于传统电加热除霜，复合加热循环除霜过程冷库温度波动减小3.8℃，相对湿度波动降低21.1百分点，除霜时间缩短14 min，系统除霜节能率达34.5%。%In recent years, mini cold storage house has developed rapidly. The evaporator is extremely easy to frost as a result of locating in the condition of low temperature and high humidity. However, defrosting energy consumption accounts for more than 10% of system’s total energy consumption. To overcome the defect about high energy consumption, temperature and humidity fluctuation of traditional defrosting technology in mini cold storage house, we investigated a new framework by changing the structure of the defrosting system and optimizing the control technology. Firstly, we developed a new defrosting system named as recombination heating circulation defrosting (RHCD) based on overhead coil auxiliary refrigeration. After that, the time-differential pressure (TDP) combining intelligent control method was used innovatively to determine the best defrosting point. Finally, OMRON programmable logic controller was applied to combine some devices to finish the defrosting. In the defrosting process, the electric-air valves installed on the incubator were closed timely to restrain heat and vapor into the cold storage house, and hot air flow was forced to circulate in the bypass channel under the working of blowers. Meanwhile overhead coil auxiliary refrigeration system was started to maintain stability of temperature and humidity. After defrosting, coil auxiliary refrigeration system was terminated and the electric-air valves were kept closed to finish cooling and dehumidification of incubator until temperature of incubator was reduced to be consistent with cold storage house. Accurate and complicated logic control of RHCD system, including TDP method and the working about some defrosting devices, was based on OMRON programmable logic controller. This paper made theoretical analysis and simulation about temperature and velocity field of the defrosting process by COMSOL. The results showed that RHCD has higher heat transfer coefficient between air and frost for the reason that incubator has higher air velocity (2 m/s) and steady-state temperature. Moreover, we also completed an experimental research to analyze the working performance and energy consumption of RHCD and other methods. The results showed that RHCD, compared with the traditional electric heating defrosting (EHD), reduced the fluctuation of temperature by 3.8 degrees and relative humidity by 21.1%. Defrosting time was shortened by 14 minutes. Energy consumption of electric heater was decreased by 50 percent and energy-saving rate could reach 34.5 percent in total defrosting process. The RHCD can not only improve performance of food preservation but also save energy efficiently.
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