PURPOSE:To perform a cold heat accumulation, a thermal accumulation at a desired time and to enable a cooling and both cooling and heating to be carried out without operating a compressor at any time by a method wherein a bypassing pipe communicating with a high pressure liquid pipe and a suction pipe of a reversed Carnot cycle is provided with a low pressure liquid acceptor filled with cold heat accumulation material, thermal medium is circulated through the low pressure liquid acceptor and then cold heat is accumulated and then the thermal medium in the low pressure liquid acceptor is circulated through an evaporator. CONSTITUTION:In a reversed Carnot cycle, a bypassing pipe 17 for communicating between a high pressure liquid pipe 12 and a suction pipe 16 is provided. A low pressure type liquid acceptor tank 21 is connected at a connecting intermediate part between a liquid pipe 18 branched from a high pressure liquid pipe 12 and a liquid pipe 18. Cold heat accumulation material 22 is stored in the liquid acceptor tank 21. A liquid pump 23 is connected to a circulation pipe 24 and a spray 25. A supplying pipe 26 connected to a liquid pump 23 is connected between an expansion valve 3 and one end of an evaporator 4. A return pipe 28 is connected to a three-way valve 14. Thermal medium from the compressor 1 is circulated through the low pressure liquid acceptor 21 to a suction side and then cold heat is accumulated. The thermal medium is circulated by a liquid pump 23 to the evaporator 4 to perform a cooling operation. The cold heat accumulation is performed at a desired time, the cold heat accumulated at any time is utilized and then a cooling operation is carried out.