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The liquid refrigerant defrosting system (LRDS) has the advantages that the refrigeration process is continuous, the temperature fluctuation of the cold storage is small, and the cooling energy of the frost can be recovered effectively. However, the system is too complex to apply and promote in the modern cold storage. In order to solve the problem of operation difficulty, the control experiments were carried out, including the beginning of the defrosting (BD), the end of the defrosting (ED), the draining time (DT) and the time difference between the two air coolers start-up (TDTACS). The results showed that the LRDS started to defrost when the air pressure difference was higher than 0.5mbar. The outlet should be located at the middle part of the lower 1/3 part of the evaporation surface. The measuring pressure tube inserted the fin 20mm, and the nozzle was perpendicular to the evaporation pipe. The experimental ambient temperature was 30℃, and the frost mass was 3kg. The gas return temperature at the ED was 3.0℃, 4.0℃, 5.0℃, 6.4℃ and 7.4℃ respectively when the cold storage temperature was 0℃, 5℃, 10℃, 15℃ and 20℃ respectively. The DT was controlled between 140s and 180s, which could prevent the wet compression. In order to get the TDTACS, the manual control could be adopted for the first defrosting. Then the air pressure difference control could be used. The two air coolers could refrigerate and defrost alternately.

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