Study on the performance liquid refrigerant defrosting system

The liquid refrigerant defrosting (LRD) is a defrosting method which makes the liquid refrigerant in the high pressure reservoir to the frost air cooler. The refrigeration process is continuous during the defrosting period; the temperature fluctuation of the cold storage is small; and there is no additional energy consumption. In order to investigate the running performance of the system in the defrosting process, many parameters were measured, including the compressor power, the temperature and pressure of the liquid supply and gas return of the reservoir, the temperature and pressure of the liquid supply and gas return of the duplex air cooler and the cold storage temperature. The results showed that the compressor power decreased from 2.0 kW to 0.8 kW, decreased by 60%, during the defrosting. The liquid refrigerant in the defrosting air cooler had almost no pressure drop, and the pressure drop of the compressor suction mainly caused by the pressure drop in the refrigeration air cooler. The temperature difference between the liquid supply and the gas return of the defrosting air cooler raised from 7.0 °C to 18.0 °C and the refrigeration air cooler raised from 11.0 °C to 13.0 °C. The sub-cooling and the gas return superheat increased at the same time, so that the flow rate decreased. After defrosting, the fan of the defrosting air cooler was opened suddenly, so that the fluctuation value of the cold storage temperature increased. According to the experiments, a series of improvement suggestions were put forward, which provided the important theoretical basis for the further optimization of the LRD system.