Heat pump system

A heat pump system, comprising:

• a refrigerant circuit having a compressor configured to compress a refrigerant, a heat source-side heat exchanger configured to function as an evaporator of the refrigerant, and a refrigerant-water heat exchanger configured to function as a heat radiator of the refrigerant and to heat an aqueous medium, the compressor being a variable-capacity-type compressor;
• an aqueous medium circuit having a circulation pump and the refrigerant-water heat exchanger, the aqueous medium exchanging heat with the refrigerant in the refrigerant-water heat exchanger and being circulated in the aqueous medium circuit, and the aqueous medium circuit being connected to aqueous medium devices configured to use the aqueous medium to perform an operation;
• an auxiliary heat source configured to further heat the aqueous medium circulating in the aqueous medium circuit, the auxiliary heat source being provided at an aqueous medium outlet side of the refrigerant-water heat exchanger in the aqueous medium circuit;
• a heating capability computation unit configured to compute a heating capability of the aqueous medium devices based on an operating state quantity of constituent devices or the refrigerant flowing through the refrigerant circuit;
• a circulation flow rate computation unit configured to compute a circulation flow rate of the aqueous medium in the aqueous medium circuit based on the heating capability and an outlet/inlet temperature difference between an inlet temperature and an outlet temperature of the aqueous medium in the refrigerant-water heat exchanger;
• a prediction unit configured to predict an outlet temperature of the aqueous medium in the auxiliary heat source when the auxiliary heat source has acted based on the circulation flow rate and heat source capability information indicative of a capacity of the auxiliary heat source;
• and
• a heat source operation controller configured to cause the auxiliary heat source to perform an operation when
• the capacity of the compressor is a predetermined capacity of higher, and
• an outlet-side temperature difference between a target outlet temperature and the outlet temperature of the aqueous medium in the refrigerant-water heat exchanger is a first predetermined temperature difference or higher.