Patent ID: 7716934

Claim:
An air conditioning device comprising: a waste heat utilization circuit which circulates a fluid through a heat source and a heat exchanger for heating and in which waste heat of the heat source is utilized in heating a room to be conditioned in the heat exchanger for heating; a refrigerant circuit in which carbon dioxide is used as a refrigerant and which has a supercritical pressure on a high pressure side; and a cascade heat exchanger which performs heat exchange between the fluid flowing from the heat source to the heat exchanger for heating in the waste heat utilization circuit and the refrigerant of the refrigerant circuit, the refrigerant circuit including a compressor, the cascade heat exchanger, a flow divider, an auxiliary pressure reduction unit, an internal heat exchanger, a main pressure reduction unit and a heat absorber disposed externally from the room to be conditioned, the refrigerant discharged from the compressor being passed through the cascade heat exchanger, the refrigerant discharged from the cascade heat exchanger being divided by the flow divider, one divided refrigerant being passed from the auxiliary pressure reduction unit to the internal heat exchanger to perform heat exchange between the refrigerant and the refrigerant discharged from the cascade heat exchanger and being then sucked into an intermediate pressure section of the compressor, the other divided refrigerant being passed from the main pressure reduction unit to the heat absorber and being then sucked into a low pressure section of the compressor, wherein: the air conditioning device further comprises a temperature detection unit for detecting a temperature of the refrigerant of the intermediate pressure section of the compressor, and the air conditioning device is configured to control an open degree of the auxiliary pressure reduction unit so that the temperature detected by the temperature detection unit indicates the maximum value.