Patent ID: 7185505

Claim:
A refrigerant circuit comprising: a compressor for compressing refrigerant; a first heat exchanger selectively functioning as any one of an evaporator and a condenser; an expansion valve for reducing the pressure of the refrigerant; a second heat exchanger selectively functioning as the other of the evaporator and the condenser, which are connected in series to one another to thereby circulate the refrigerant in the refrigerant circuit; and a third heat exchanger that heat exchanges the compressed refrigerant discharged from the compressor with heat-exchange fluid at all times and is equipped in the refrigerant circuit so as to be connected to the first heat exchanger in series in the refrigerant circuit, wherein the refrigerant circuit comprises a first refrigerant passage connecting the compressor, the third heat exchanger and the first heat exchanger in series, a second refrigerant passage that is connected to the third heat exchanger and bypasses the first heat exchanger, a third refrigerant passage connected to the second heat exchanger and the third heat exchanger, and a refrigerant passage switching unit for selecting at least one of flow of the refrigerant between the first refrigerant passage and the second refrigerant passage, flow of the refrigerant between the second refrigerant passage and the third refrigerant passage and flow of the refrigerant between the first refrigerant passage and the third refrigerant passage, wherein the refrigerant circuit further comprises a temperature detecting unit for comparing refrigerant temperature at a refrigerant outlet port of the third heat exchanger with the outside air temperature and a controller for controlling the switching operation of the switching unit on the basis of the comparison result.