Investigation of air cooler fan start-up delay in liquid refrigerant defrosting system

Highlights: • The liquid refrigerant defrosting system was introduced in detail. • The fluctuation value of the cold storage temperature was controlled. • The wet compression was prevented effectively. • The gas return temperature of 10 °C was selected as the trigger signal of defrosting. To prevent problems concerning rapid rise in cold-storage temperature and severe frosting of the compressor inlet in liquid refrigerant defrosting systems (LRDS), a shutter has been installed upstream of the air cooler as well as the motor damper installed downstream. It is also proposed that the air-cooler fan is switched into operation delay after defrosting. Experimental results demonstrate that the best time to switch the fan into operation post defrosting is when the enclosed-space temperature of the air cooler falls in line with the cold-storage temperature. Time delays for the fan were set as 8.6 min, 8.8 min, and 8.9 min corresponding to frost-mass values of 1 kg, 2 kg, and 3 kg, respectively. Through use of the proposed technique, the observed increase in cold-storage temperature was controlled within 5 °C. In addition, gas return temperature of the compressor was observed to be greater compared to that of the air cooler; the compressor, therefore, utilized the available superheat to prevent the occurrence of wet compression.