DEFROSTING METHOD AND DEFROSTING DEVICE OF AIR REFRIGERANT TYPE FREEZING APPARATUS

PROBLEM TO BE SOLVED: To provide an air refrigerant type freezing apparatus that enables an efficient defrosting-energy-saving operation, shortens the defrosting process time, and improves its operability.SOLUTION: A defrosting device of the air refrigerant type freezing apparatus includes: a first bypass passage 38 that bypasses a compartment 32 to supply an air refrigerant on an outlet side of an expander to an inlet side of a frosting trap 34; a second bypass passage 36 that bypasses the compartment 32 to supply an air refrigerant on an outlet side of a primary cooler 22 to an inlet side of an expander 18; a pressure sensor 50 which detects an inlet pressure of a compressor 12; a temperature sensor 51 that detects a refrigerant temperature Ton an inlet side of the compressor; temperature sensors 52 and 53 that detect the air refrigerant temperature Tand air refrigerant passage wall temperature Tin an inlet area on a low temperature side of a heat recovery unit 30; and a temperature sensor 54 that detects a refrigerant temperature Ton an outlet side of the compressor. The defrosting process finishes when the air refrigerant passage wall temperature Treaches the melting completion temperature Tg of 2-7°C while maintaining the air refrigerant temperature Ton the inlet side of the compressor at the set value Tcs during the defrosting operation.