Heat pump apparatus

摘要

In a heat pump apparatus, it is aimed to enhance efficiency of a defrost operation by reducing a loss of heat radiation during the defrost operation and reducing a compressor input during the defrost operation. The heat pump apparatus includes a main refrigerant circuit in which a compressor, a first heat exchanger, an expansion mechanism, and a second heat exchanger are connected sequentially, and also includes a bypass circuit including an on-off valve and providing a connection by bypassing the expansion mechanism. The main refrigerant circuit includes a four-way valve that switches between a heating operation and the defrost operation by switching an order in which the refrigerant circulates through the main refrigerant circuit. The main refrigerant circuit also includes a first temperature detection unit and a second temperature detection unit. Based on values detected by these temperature detection units, a degree of superheat of the first heat exchanger during the defrost operation is computed. When the heating operation is switched to the defrost operation, the heat pump apparatus increases a circulation amount of the refrigerant circulating through the refrigerant circuit by opening the on-off valve, and also controls an operation frequency of the compressor such that the degree of superheat is at a predetermined target value.

主权项

1. A heat pump apparatus comprising:
a refrigerant circuit in which a compressor, a first heat exchanger, a first expansion mechanism, a liquid accumulator, a second expansion mechanism, and a second heat exchanger are connected sequentially; a bypass circuit that includes an on-off valve, and connects a midpoint between the first heat exchanger and the first expansion mechanism with a midpoint between the second expansion mechanism and the second heat exchanger in the refrigerant circuit such that the first expansion mechanism, the liquid accumulator, and the second expansion mechanism are bypassed, a switching unit that switches a direction in which a refrigerant flows between a heating operation and a defrost operation, thereby switching between the heating operation and the defrost operation; a superheat detection unit that detects a degree of superheat of the refrigerant at the first heat exchanger during the defrost operation; and a control unit that, when the heating operation is switched to the defrost operation by the switching unit, closes the second expansion mechanism, and after a predetermined period of time has elapsed, closes the first expansion mechanism and opens the on-off valve included in the bypass circuit, thereby increasing a circulation amount of the refrigerant circulating through the refrigerant circuit, and controls an operating frequency of the compressor such that the degree of superheat detected by the superheat detection unit is at a target value which is predetermined.