Abstract:
Abstract: 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.