Heat pump device, two-stage compressor, and operation method of heat pump device

摘要

To improve the efficiency of a two-stage compressor and of a heat pump apparatus employing a two-stage compressor when a load is small. The heat pump apparatus includes a main refrigerant circuit formed by connecting a two-stage compressor 100, a first heat exchanger, a first expansion mechanism, and a second heat exchanger sequentially with piping. When a load is higher than a predetermined load, the two-stage compressor 100 discharges a refrigerant, which is compressed twice by a low-stage compressor portion 10 and a high-stage compressor portion 30, to the refrigerant circuit. When the load is lower than the predetermined load, the two-stage compressor 100 discharges the refrigerant compressed by the low-stage compressor portion 10 to the main refrigerant circuit while bypassing the high-stage compressor portion 30 so the refrigerant is not compressed by the high-stage compressor portion 30.