초록 ▼

In a hot-water supply system with a heat pump cycle, a control unit controls operation of an expansion valve based on a temperature difference between a refrigerant temperature at an outlet side of a refrigerant passage in a water heat exchanger and a water temperature at an inlet side of a water pa

In a hot-water supply system with a heat pump cycle, a control unit controls operation of an expansion valve based on a temperature difference between a refrigerant temperature at an outlet side of a refrigerant passage in a water heat exchanger and a water temperature at an inlet side of a water passage in the water heat exchanger. When the expansion valve is controlled in a direction increasing a valve opening degree, the control unit sets an upper limit opening degree of the expansion valve, for obtaining a refrigerant pressure corresponding to a target hot-water temperature, and controls the expansion valve in an opening degree range smaller than the upper limit opening degree.

대표청구항 ▼

1. A hot-water supply system comprising:a heat pump cycle including a refrigerant compressor for compressing refrigerant, a refrigerant passage in a fluid heat exchanger for performing a heat exchange with a fluid in a fluid passage, an expansion valve for decompressing refrigerant and an air heat e

1. A hot-water supply system comprising:a heat pump cycle including a refrigerant compressor for compressing refrigerant, a refrigerant passage in a fluid heat exchanger for performing a heat exchange with a fluid in a fluid passage, an expansion valve for decompressing refrigerant and an air heat exchanger for performing a heat exchange between refrigerant and air, which are connected to form a closed refrigerant circuit; a fluid circuit having therein a tank for storing the fluid for a supply, and a pump for flowing the fluid in the fluid circuit, the tank being connected to the fluid passage of the fluid heat exchanger; and a control unit for controlling a temperature of the fluid to be supplied to a target fluid temperature; wherein: the control unit controls the operation of the expansion valve in a first direction increasing an opening degree of the expansion valve, when a temperature difference, between a refrigerant temperature at an outlet side of the refrigerant passage in the fluid heat exchanger and a fluid temperature at an inlet side of the fluid passage in the fluid heat exchanger, is smaller than a target temperature difference; the control unit controls operation of the expansion valve in a second direction decreasing the opening degree of the expansion valve, when the temperature difference is larger than the target temperature difference; and when the temperature difference is smaller than the target temperature difference and the expansion valve is controlled in the first direction, the control unit maintains a high-pressure side refrigerant pressure before being decompressed in the heat pump cycle to be higher than a predetermined refrigerant pressure to achieve the target fluid temperature.