PURPOSE: To obviate a large capacity refrigerant circulation pump and enable a high c.o.p to be exerted with a low compression ratio operation by carrying out refrigerant circulation only with a first compressor during thermal storage operation, liquid excess cooling operation and general cooling operation and only with a second compressor during cold storage condensation operation.
CONSTITUTION: When a first compressor 1 is adapted to come to a stop during cold storage condensation cooling operation while a second compressor 15 and a thermal storage medium circulation pump 8 are operated, the evaporated gas refrigerant from an application side heat exchanger 4 is discharged in compression mode by a compres sor 15 and enters a thermal storage heat exchanger 9. Then, the gas is liquified by a low temperature thermal storage medium 7 fed by the pump 8, and fed into a first throttling device 3 where the liquefied gas is insulation-expanded. Further, the liquefied gas enters the application side heat exchanger 4 for cooling while it is gasified again and comes back to the compressor 15. During thermal storage operation the compressor is adapted to come to a stop while the compressor 1 and the pump 8 are operated. During liquid excess cooling operation, the compressor 15 is adapted to come to a halt while compressor 1 and the pump 8 are operated. During general cooling refrigera tion cycle operation, the compressor 15 and the pump 8 are brought to a halt while the compressor 1 is operated.