CLOSED GAS CIRCULATION TYPE REFRIGERATION SYSTEM AND OPERATION METHOD THEREOF

PROBLEM TO BE SOLVED: To provide a closed gas circulation type refrigeration device that can adjust refrigerant gas pressure in a compressor suction-side refrigerant gas path, and is simple and low-cost.SOLUTION: A closed gas circulation type refrigeration device 10A, after cooling refrigerant air of high temperature and high pressure compressed by a compressor 22 by a water-cooling type heat exchanger 16 and a heat recovering heat exchanger 18, expands the refrigerant air by an expanding machine 26 to generate refrigerant air of very low temperature and low pressure. The refrigerant air of very low temperature and low pressure is supplied to a brine cooler 20. A closed refrigerant air supply and discharge device 50 is provided which comprises an expansion tank 51, a compressor suction-side connection path 52, and a compressor discharge-side connection path 54, a pressure sensor 62 detects the refrigerant air pressure in a compressor suction-side air path 12a, and the refrigerant air is supplied and discharged between the expansion tank 51 and the compressor suction-side refrigerant air path 12a or compressor discharge-side refrigerant air path 12b so that the refrigerant air pressure may be within a set range.