Heat pump system

A heat pump system includes: a heat-source-side refrigerant circuit having a heat-source-side compressor, a first usage-side heat exchanger operable as a radiator of heat-source-side refrigerant, and a heat-source-side heat exchanger operable as an evaporator of heat-source-side refrigerant; and a usage-side refrigerant circuit having a usage-side compressor arranged to compress usage-side refrigerant with a pressure of the usage-side refrigerant corresponding to a saturated gas temperature of 65° C. that is 2.8 MPa or less at gauge pressure, a refrigerant-water heat exchanger operable as a radiator of usage-side refrigerant to heat an aqueous medium, and a first usage-side heat exchanger operable as an evaporator of usage-side refrigerant by the radiation of heat-source-side refrigerant. The weight of usage-side refrigerant enclosed in the usage-side refrigerant circuit is one to three times the weight of refrigeration machine oil enclosed to lubricate the usage-side compressor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. National stage application claims priority under 35 U.S.C. §119(a) to Japanese Patent Application No. 2009-041321, filed in Japan on Feb. 24, 2009, the entire contents of which are hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a heat pump system, and particularly relates to a heat pump system capable of heating an aqueous medium by utilizing a heat pump cycle.

BACKGROUND ART

Heat pump water heaters, such as the one described in Japanese Laid-open Patent Publication No. 60-164157, are known which are capable of utilizing a heat pump cycle to heat water. Such a heat pump water heater has primarily a compressor, a refrigerant/water heat exchanger, and a heat-source-side heat exchanger, and is configured so that water is heated by the radiation of refrigerant in the refrigerant/water heat exchanger, and the hot water thereby obtained is fed to a storage tank.

SUMMARY

With the conventional heat pump water heater described above, an auxiliary heater as well as a refrigerant/water heat exchanger must be used in combination to heat water, to increase the discharge pressure of the compressor, and to otherwise operate under conditions of poor operating efficiency in order to supply high-temperature hot water to a hot-water storage tank, and such a situation is not preferred.

An object of the present invention is to provide a high-temperature aqueous medium in a heat pump system capable of heating an aqueous medium using a heat pump cycle.

A heat pump system according to a first aspect comprises a heat-source-side refrigerant circuit and a usage-side refrigerant circuit. The heat-source-side refrigerant circuit has a heat-source-side compressor for compressing a heat-source-side refrigerant, a first usage-side heat exchanger capable of functioning as a radiator of the heat-source-side refrigerant, and a heat-source-side heat exchanger capable of functioning as an evaporator of the heat-source-side refrigerant. The usage-side refrigerant circuit has a usage-side compressor for compressing a usage-side refrigerant whose pressure corresponding to a saturated gas temperature of 65° C. is 2.8 MPa or less at gauge pressure, a refrigerant-water heat exchanger capable of functioning as a radiator of the usage-side refrigerant and heating an aqueous medium, and a first usage-side heat exchanger capable of functioning as an evaporator of the usage-side refrigerant by the radiation of the heat-source-side refrigerant. The usage-side compressor, the first usage-side heat exchanger, and the refrigerant-water heat exchanger constitute a first usage unit, the length of a refrigerant tube from the first usage-side heat exchanger functioning as an evaporator of the usage-side refrigerant to the usage-side compressor is 3 m or less, the usage-side refrigerant circuit is not provided with an oil separating mechanism for separating refrigeration machine oil contained in the usage-side refrigerant discharged from the usage-side compressor and returning the oil to the intake of the usage-side compressor, and the weight of the usage-side refrigerant enclosed in the usage-side refrigerant circuit is one to three times the weight of the refrigeration machine oil enclosed for lubricating the usage-side compressor.

In this heat pump system, in the first usage-side heat exchanger, the usage-side refrigerant circulating through the usage-side refrigerant circuit is heated by the radiated heat of the heat-source-side refrigerant circulating through the heat-source-side refrigerant circuit, and the usage-side refrigerant circuit can use the heat obtained from the heat-source-side refrigerant to achieve a refrigeration cycle of a higher temperature than the refrigeration cycle in the heat-source-side refrigerant circuit; therefore, a high-temperature aqueous medium can be obtained due to the heat radiation of the usage-side refrigerant in the refrigerant-water heat exchanger.

At this time, considering a circuit configuration such as that of this heat pump system wherein the usage-side refrigerant circuit is included in the first usage unit, and the refrigerant tube is short with a length of 3 m or less from the first usage-side heat exchanger functioning as an evaporator of the usage-side refrigerant to the usage-side compressor; since there is little chance of refrigeration machine oil getting backed up in portions of the usage-side refrigerant circuit other than the usage-side compressor, it is essentially believed that the amount of refrigeration machine oil enclosed with the usage-side refrigerant in the usage-side refrigerant circuit can be reduced.

For the sake of obtaining a high-temperature aqueous medium, the usage-side refrigerant is preferably a refrigerant with a high boiling point such as a refrigerant whose pressure corresponding to a saturation gas temperature of 65° C. is 2.8 MPa or less at gauge pressure (i.e., a refrigerant having low-pressure saturation characteristics), as is the case in this heat pump system, but when such a refrigerant having low-pressure saturation characteristics is used for the objective of obtaining a high-temperature aqueous medium, the gaseous usage-side refrigerant blended in with the refrigeration machine oil is increased by this use of refrigerant under high-temperature conditions. As a result, the coefficient of viscosity of the refrigeration machine oil decreases, a greater amount of refrigeration machine oil is discharged with the refrigerant from the usage-side compressor, and there is a risk of lubrication inside the usage-side compressor being insufficient; therefore, it is believed that the amount of refrigeration machine oil enclosed with the usage-side refrigerant in the usage-side refrigerant circuit must be increased.

When the temperature of the refrigeration machine oil in the usage-side compressor is lower than the condensation temperature of the usage-side refrigerant, there is a risk that the usage-side refrigerant will condense in the usage-side compressor and dilute the refrigeration machine oil, but particularly in a system for obtaining a high-temperature aqueous medium such as this heat pump system, the refrigeration machine oil is diluted quite readily because of the high condensation temperature of the usage-side refrigerant. As a result, there is a risk that the coefficient of viscosity of the refrigeration machine oil will decrease, the amount of refrigeration machine oil discharged with the refrigerant from the usage-side compressor will increase, and the lubrication inside the usage-side compressor will be insufficient; therefore, for this reason as well it is believed that the amount of refrigeration machine oil enclosed with the usage-side refrigerant in the usage-side refrigerant circuit must be increased.

Thus, when the amount of refrigeration machine oil is increased, an oil separation mechanism is preferably provided for separating the refrigeration machine oil discharged synchronously with the usage-side refrigerant discharged from the usage-side compressor and returning the oil to the intake of the usage-side compressor.

However, during use under high-temperature conditions such as those of this heat pump system, since the gaseous usage-side refrigerant blended in with the refrigeration machine oil increases and the refrigeration machine oil is readily diluted as described above, the amount of refrigeration machine oil discharged along with the usage-side refrigerant discharged from the usage-side compressor also increases. Therefore, when an oil separation mechanism is provided, a greater amount of usage-side refrigerant is returned to the intake of the usage-side compressor together with the refrigeration machine oil, and there is a risk of operating efficiency being reduced.

In view of this, in this heat pump system, considering the objective of obtaining a high-temperature aqueous medium (promoting dilution of the refrigeration machine oil due to a greater amount of gaseous usage-side refrigerant with a high condensation temperature being dissolved in the refrigeration machine oil, and due to condensation of the usage-side refrigerant) as well as the low risk of refrigeration machine oil backing up in portions of the usage-side refrigerant circuit other than the usage-side compressor (i.e., circuit structural characteristics, which are that the usage-side refrigerant circuit is included in the first usage unit, and the refrigerant tube has a short length of 3 m or less from the first usage-side heat exchanger functioning as an evaporator of the usage-side refrigerant to the usage-side compressor), the usage-side refrigerant circuit is not provided with an oil separation mechanism for separating refrigeration machine oil included in the usage-side refrigerant discharged from the usage-side compressor and returning the oil to the intake of the usage-side compressor, and the weight of usage-side refrigerant enclosed in the usage-side refrigerant circuit is one to three times the weight of the refrigeration machine oil enclosed for lubricating the usage-side compressor, unlike the conventional practice concerning the weight of refrigeration machine oil.

It is thereby possible in this heat pump system to obtain a high-temperature aqueous medium while allowing a greater amount of usage-side refrigerant to be returned with the refrigeration machine oil to the intake of the usage-side compressor and suppressing both the resulting decrease in operating efficiency and insufficient lubrication inside the usage-side compressor.

A heat pump system according to a second aspect is the heat pump system according to the first aspect, wherein the pressure of the usage-side refrigerant corresponding to a saturated gas temperature of 65° C. is 2.0 MPa (gauge pressure) or less.

In this heat pump system, since the refrigerant used as the usage-side refrigerant is a refrigerant whose pressure corresponding to a saturated gas temperature of 65° C. is 2.0 MPa or less at gauge pressure and which has low-pressure saturation characteristics, an even higher-temperature aqueous medium can be obtained, and the operational effects of the heat pump system according to the first aspect are more pronounced.

A heat pump system according to a third aspect is the heat pump system according to the first or second aspect, wherein the usage-side refrigerant circuit further has an accumulator capable of temporarily storing the usage-side refrigerant in the intake of the usage-side compressor, and a refrigerant-water heat-exchange-side flow rate adjustment valve capable of varying the flow rate of the usage-side refrigerant flowing through the refrigerant-water heat exchanger; and when a determination has been made that the refrigeration machine oil is insufficient in the usage-side compressor, an oil recovery operation is performed for returning the usage-side refrigerant containing the refrigeration machine oil in the refrigerant-water heat exchanger to the accumulator via the refrigerant-water heat-exchange-side flow rate adjustment valve and the first usage-side heat exchanger.

In the heat pump system according to the first or second aspect, since an oil separation mechanism is not provided, the refrigeration machine oil is readily led with the usage-side refrigerant into the refrigerant-water heat exchanger functioning as a radiator of the usage-side refrigerant, and under high-temperature conditions, biphasic separation of liquid usage-side refrigerant and refrigeration machine oil occurs readily inside the refrigerant-water heat exchanger. Therefore, the refrigeration machine oil likely backs up inside the refrigerant-water heat exchanger functioning as a radiator of the usage-side refrigerant.

In view of this, in this heat pump system, insufficiency of refrigeration machine oil in the usage-side compressor can be prevented by further providing the usage-side refrigerant circuit with a usage-side accumulator capable of temporarily storing the usage-side refrigerant in the intake of the usage-side compressor and a refrigerant-water heat-exchange-side flow rate adjustment valve capable of varying the flow rate of the usage-side refrigerant flowing through the refrigerant-water heat exchanger, and by performing an oil recovery operation when it has been determined that the refrigeration machine oil is insufficient in the usage-side compressor, whereby the usage-side refrigerant containing the refrigeration machine oil in the refrigerant-water heat exchanger is passed through the refrigerant-water heat-exchange-side flow rate adjustment valve and the first usage-side heat exchanger and returned to the usage-side accumulator under low-temperature conditions in which biphasic separation of liquid usage-side refrigerant and refrigeration machine oil does not occur readily. During this oil recovery operation, it is possible to continue the operation of making the refrigerant-water heat exchanger function as a radiator of the usage-side refrigerant and heating the aqueous medium.

A heat pump system according to a fourth aspect is the heat pump system according to the third aspect, wherein the determination of whether or not the refrigeration machine oil is insufficient in the usage-side compressor is performed based on the temperature of the usage-side refrigerant in the discharge of the usage-side compressor or the temperature of the aqueous medium in the outlet of the refrigerant-water heat exchanger.

In this heat pump system, since the determination of whether or not the refrigeration machine oil is insufficient in the usage-side compressor is performed based on the temperature of the usage-side refrigerant in the discharge of the usage-side compressor or the temperature of the aqueous medium in the outlet of the refrigerant-water heat exchanger, the determination of whether or not the refrigeration machine oil is insufficient in the usage-side compressor can be appropriately performed while taking into account the extent to which the usage-side refrigerant is blended in with the refrigeration machine oil in the usage-side compressor as well as the extent of biphasic separation of the usage-side refrigerant and the refrigeration machine oil in the refrigerant-water heat exchanger.

DESCRIPTION OF EMBODIMENTS

Embodiments of the heat pump system according to the present invention will be described based on the drawings.

FIG. 1is a view showing the general configuration of a heat pump system1according to a first embodiment of the present invention. The heat pump system1is an apparatus capable of operation for heating an aqueous medium, and other operation by utilizing a vapor compression heat pump cycle.

The heat pump system1mainly has a heat source unit2, a first usage unit4a, a liquid refrigerant communication tube13, a gas refrigerant communication tube14, a hot-water storage unit8a, a hot-water air-warming unit9a, an aqueous medium communication tube15a, and an aqueous medium communication tube16a. The heat source unit2and the first usage unit4aconstitute a heat-source-side refrigerant circuit20by being connected via the refrigerant communication tubes13,14. The first usage unit4aconstitutes a usage-side refrigerant circuit40a. The first usage unit4a, the hot-water storage unit8a, and the hot-water air-warming unit9aconstitute an aqueous medium circuit80aby being connected via the aqueous medium communication tubes15a,16a. HFC-410A, which is a type of HFC-based refrigerant, is enclosed inside the heat-source-side refrigerant circuit20as a heat-source-side refrigerant, and an ester-based or ether-based refrigeration machine oil having compatibility with respect to the HFC-based refrigerant is enclosed for lubrication of a heat-source-side compressor21(described later). Also, HFC-134a, which is a type of HFC-based refrigerant, is enclosed inside the usage-side refrigerant circuit40aas a usage-side refrigerant, and an ester-based or ether-based refrigeration machine oil having compatibility with respect to the HFC-based refrigerant is enclosed for lubrication of a usage-side compressor62a. The usage-side refrigerant is preferably one in which the pressure that corresponds to a saturated gas temperature of 65° C. is a maximum gauge pressure of 2.8 MPa or less, and is more preferably a refrigerant of 2.0 MPa or less from the viewpoint of using a refrigerant that is advantageous for a high-temperature refrigeration cycle. The weight of the usage-side refrigerant enclosed in the usage-side refrigerant circuit40ais one to three times the weight of the refrigeration machine oil enclosed in order to lubricate the usage-side compressor62a. HFC-134a is a type of refrigerant having such saturation pressure characteristics. Water is used as the aqueous medium in the aqueous medium circuit80a.

The heat source unit2is disposed outdoors, and is connected to the first usage unit4avia the refrigerant communication tubes13,14and constitutes a portion of the heat-source-side refrigerant circuit20.

The heat source unit2mainly has a heat-source-side compressor21, an oil separation mechanism22, a heat-source-side switching mechanism23, a heat-source-side heat exchanger24, a heat-source-side expansion valve25, an intake return tube26, a subcooler27, a heat-source-side accumulator28, a liquid-side shutoff valve29, and a gas-side shutoff valve30.

The heat-source-side compressor21is a mechanism for compressing the heat-source-side refrigerant. The heat-source-side compressor21used herein is an airtight compressor in which a rotary-type, scroll-type, or other positive-displacement compression element (not shown) housed in a casing (not shown) is driven by a heat-source-side compressor motor21awhich is also housed in the casing. A high-pressure space (not shown) filled by the heat-source-side refrigerant after compression in the compression element is formed inside the casing of the heat-source-side compressor21, and refrigeration machine oil is stored in the high-pressure space. The rotation speed (i.e., the operating frequency) of the heat-source-side compressor motor21acan be varied by an inverter apparatus (not shown), and the capacity of the heat-source-side compressor21can thereby be controlled.

The oil separation mechanism22is a mechanism for separating refrigeration machine oil included in the heat-source-side refrigerant that is discharged from the heat-source-side compressor21and returning the refrigeration machine oil to the intake of the heat-source-side compressor. The oil separation mechanism22has primarily an oil separator22aprovided to a heat-source-side discharge tube21bof the heat-source-side compressor21; and an oil return tube22bfor connecting the oil separator22aand a heat-source-side intake tube21cof the heat-source-side compressor21. The oil separator22ais a device for separating refrigeration machine oil included in the heat-source-side refrigerant that is discharged from the heat-source-side compressor21. The oil return tube22bhas a capillary tube, and is a refrigerant tube for returning the refrigeration machine oil separated from the heat-source-side refrigerant in the oil separator22ato the heat-source-side intake tube21cof the heat-source-side compressor21.

The heat-source-side switching mechanism23is a four-way switching valve capable of switching between a heat-source-side radiating operation state in which the heat-source-side heat exchanger24functions as a radiator of the heat-source-side refrigerant, and a heat-source-side evaporating operation state in which the heat-source-side heat exchanger24functions as a evaporator of the heat-source-side refrigerant. The heat-source-side switching mechanism23is connected to the heat-source-side discharge tube21b, the heat-source-side intake tube21c, a first heat-source-side gas refrigerant tube23aconnected to the gas side of the heat-source-side heat exchanger24, and a second heat-source-side gas refrigerant tube23bconnected to the gas-side shutoff valve30. The heat-source-side switching mechanism23is capable of switching for communicating the heat-source-side discharge tube21bwith the first heat-source-side gas refrigerant tube23a, and communicating the second heat-source-side gas refrigerant tube23bwith the heat-source-side intake tube21c(this switching corresponding to the heat-source-side radiating operation state, indicated by solid lines in the heat-source-side switching mechanism23inFIG. 1). The heat-source-side switching mechanism23is also capable of switching for communicating the heat-source-side discharge tube21bwith the second heat-source-side gas refrigerant tube23b, and communicating the first heat-source-side gas refrigerant tube23awith the heat-source-side intake tube21c(this switching corresponding to the heat-source-side evaporating operation state, indicated by dashed lines in the heat-source-side switching mechanism23inFIG. 1). The heat-source-side switching mechanism23is not limited to a four-way switching valve, and may configured so as to have a function for switching the same directions of heat-source-side refrigerant flow as those described above, through the use of a combination of a plurality of solenoid valves or the like, for example.

The heat-source-side heat exchanger24is a heat exchanger for functioning as a radiator or evaporator of the heat-source-side refrigerant by exchanging heat between the heat-source-side refrigerant and outdoor air. A heat-source-side liquid refrigerant tube24ais connected to the liquid side of the heat-source-side heat exchanger24, and the first heat-source-side gas refrigerant tube23ais connected to the gas side thereof. The outdoor air for heat exchange with the heat-source-side refrigerant in the heat-source-side heat exchanger24is fed by a heat-source-side fan32which is driven by a heat-source-side fan motor32a.

The heat-source-side expansion valve25is an electrical expansion valve for performing such functions as depressurizing the heat-source-side refrigerant flowing through the heat-source-side heat exchanger24, and is provided to the heat-source-side liquid refrigerant tube24a.

The intake return tube26is a refrigerant tube for diverting a portion of the heat-source-side refrigerant flowing through the heat-source-side liquid refrigerant tube24aand returning the diverted refrigerant to the intake of the heat-source-side compressor21, and in the present embodiment, one end of the intake return tube26is connected to the heat-source-side liquid refrigerant tube24a, and the other end is connected to the heat-source-side intake tube21c. An intake return expansion valve26a, the opening degree of which can be controlled, is provided to the intake return tube26. The intake return expansion valve26ais composed of an electrical expansion valve.

The subcooler27is a heat exchanger for exchanging heat between the heat-source-side refrigerant flowing through the heat-source-side liquid refrigerant tube24aand the heat-source-side refrigerant flowing through the intake return tube26(more specifically, the heat-source-side refrigerant that has been depressurized by the intake return expansion valve26a).

The heat-source-side accumulator28is provided to the heat-source-side intake tube21c, and is a container for temporarily storing the heat-source-side refrigerant circulated through the heat-source-side refrigerant circuit20before the heat-source-side refrigerant is drawn into the heat-source-side compressor21from the heat-source-side intake tube21c.

The liquid-side shutoff valve29is a valve provided at the connection between the heat-source-side liquid refrigerant tube24aand the liquid refrigerant communication tube13. The gas-side shutoff valve30is a valve provided at the connection between the second heat-source-side gas refrigerant tube23band the gas refrigerant communication tube14.

Various types of sensors are provided to the heat source unit2. Specifically, the heat source unit2is provided with a heat-source-side intake pressure sensor33for detecting a heat-source-side intake pressure Ps1, which is the pressure of the heat-source-side refrigerant in the intake of the heat-source-side compressor21; a heat-source-side discharge pressure sensor34for detecting a heat-source-side discharge pressure Pd1, which is the pressure of the heat-source-side refrigerant in the discharge of the heat-source-side compressor21; a heat-source-side heat exchange temperature sensor35for detecting a heat-source-side heat exchanger temperature Thx, which is the temperature of the heat-source-side refrigerant in the liquid side of the heat-source-side heat exchanger24; and an outside-air temperature sensor36for detecting the outside air temperature To.

The liquid refrigerant communication tube13is connected to the heat-source-side liquid refrigerant tube24avia the liquid-side shutoff valve29, and the liquid refrigerant communication tube13is a refrigerant tube capable of directing the heat-source-side refrigerant to the outside of the heat source unit2from the outlet of the heat-source-side heat exchanger24which functions as a radiator of the heat-source-side refrigerant when the heat-source-side switching mechanism23is in the heat-source-side radiating operation state. The liquid refrigerant communication tube13is also a refrigerant tube capable of introducing the heat-source-side refrigerant from outside the heat source unit2into the inlet of the heat-source-side heat exchanger24which functions as an evaporator of the heat-source-side refrigerant when the heat-source-side switching mechanism23is in the heat-source-side evaporating operation state.

The gas refrigerant communication tube14is connected to the second heat-source-side gas refrigerant tube23bvia the gas-side shutoff valve30. The gas refrigerant communication tube14is a refrigerant tube capable of introducing the heat-source-side refrigerant into the intake of the heat-source-side compressor21from outside the heat source unit2when the heat-source-side switching mechanism23is in the heat-source-side radiating operation state. The gas refrigerant communication tube14is also a refrigerant tube capable of directing the heat-source-side refrigerant to the outside of the heat source unit2from the discharge of the heat-source-side compressor21when the heat-source-side switching mechanism23is in the heat-source-side evaporating operation state.

The first usage unit4ais disposed indoors, and is connected to the heat source unit2via the refrigerant communication tubes13,14. The first usage unit4aconstitutes a portion of the heat-source-side refrigerant circuit20. The first usage unit4aconstitutes the usage-side refrigerant circuit40a. The first usage unit4ais furthermore connected to the hot-water storage unit8aand the hot-water air-warming unit9avia the aqueous medium communication tubes15a,16a, and constitutes a portion of the aqueous medium circuit80a.

The first usage unit4amainly has a first usage-side heat exchanger41a, the first usage-side flow rate adjustment valve42a, the usage-side compressor62a, the refrigerant/water heat exchanger65a, a refrigerant/water heat exchange-side flow rate adjustment valve66a, a usage-side accumulator67a, and a circulation pump43a.

The first usage-side heat exchanger41ais a heat exchanger that functions as a radiator of the heat-source-side refrigerant by performing heat exchange between the heat-source-side refrigerant and the usage-side refrigerant. The first usage-side liquid refrigerant tube45ais connected to the liquid side of the channel through which the heat-source-side refrigerant flows. The first usage-side gas refrigerant tube54ais connected to the gas side of the channel through which the heat-source-side refrigerant flows. The cascade-side liquid-refrigerant tube68ais connected to the liquid side of the channel through which the usage-side refrigerant flows. The second cascade-side gas-refrigerant tube69ais connected to the gas side of the channel through which the usage-side refrigerant flows. The liquid refrigerant communication tube13is connected to the first usage-side liquid refrigerant tube45a. The gas-refrigerant communication tube14is connected to the first usage-side gas refrigerant tube54a. The refrigerant/water heat exchanger65ais connected to the cascade-side liquid-refrigerant tube68a. The usage-side compressor62ais connected to the second cascade-side gas-refrigerant tube69a.

The first usage-side flow fate adjustment valve42ais an electrical expansion valve that can vary the flow rate of the heat-source-side refrigerant that flows through the first usage-side heat exchanger41aby controlling the opening degree, and is provided to the first usage-side liquid refrigerant tube45a.

The usage-side compressor62ais a mechanism for compressing the usage-side refrigerant, and in this case, is a sealed compressor having rotary elements, scroll elements, or other type of positive displacement compression elements (not shown) accommodated in a casing (not shown), and is driven by a usage-side compression motor63aaccommodated in the same casing. A high-pressure space (not shown) which is filled with the usage-side refrigerant that has been compressed in the compression element is formed inside the casing of the usage-side compressor62a, and refrigeration machine oil is accumulated in this high-pressure space. The rotational speed (i.e., operational frequency) of the usage-side compression motor63acan be varied by using an inverter device (not shown), whereby the capacity of the usage-side compressor62acan be controlled. A cascade-side discharge tube70ais connected to the discharge of the usage-side compressor62a, and a cascade-side intake tube71ais connected to the intake of the usage-side compressor62a. The cascade-side gas-refrigerant tube71ais connected to the second cascade-side gas-refrigerant tube69a. The length of the refrigerant tube from the first usage-side heat exchanger41afunctioning as an evaporator of usage-side refrigerant to the usage-side compressor62a(more specifically, to the intake of the usage-side compressor62a) (i.e., the total combined length of the second cascade-side gas refrigerant tube69aand the cascade-side intake tube71a) is extremely short at 3 m or less.

The refrigerant/water heat exchanger65ais a heat exchanger that functions as a radiator of the usage-side refrigerant by heat exchange between the usage-side refrigerant and the aqueous medium. A cascade-side liquid-refrigerant tube68ais connected to the liquid side of the channel through which the usage-side refrigerant flows. A first cascade-side gas-refrigerant tube72ais connected to the gas side of the channel through which the usage-side refrigerant flows. A first usage-side water inlet tube47ais connected to the inlet side of the channel through which the aqueous medium flows. A first usage-side water outlet tube48ais connected to the outlet side of the channel through which the aqueous medium flows. The first cascade-side gas-refrigerant tube72ais connected to the cascade-side discharge tube70a. An aqueous medium communication tube15ais connected to the first usage-side water inlet tube47aand an aqueous medium communication tube16ais connected to the first usage-side water outlet tube48a.

The refrigerant/water heat exchange-side flow rate adjustment valve66ais an electrical expansion valve that can vary the flow rate of the usage-side refrigerant that flows through the refrigerant/water heat exchanger65aby controlling the opening degree, and is provided to the cascade-side liquid-refrigerant tube68a.

The usage-side accumulator67ais a container provided to the cascade-side intake tube71aand is used for temporarily accumulating the usage-side refrigerant circulating through the usage-side refrigerant circuit40abefore the usage-side refrigerant is taken from the cascade-side intake tube71ainto the usage-side compressor62a.

In this manner, the usage-side compressor62a, the refrigerant/water heat exchanger65a, the refrigerant/water heat exchange-side flow rate adjustment valve66a, and the first usage-side heat exchanger41aare connected via the refrigerant tubes71a,70a,72a,68a,69ato thereby constitute the usage-side refrigerant circuit40a. Unlike the heat-source-side refrigerant circuit20, the usage-side refrigerant circuit40ais not provided with an oil separation mechanism for separating the refrigeration machine oil contained in the usage-side refrigerant discharged from the usage-side compressor62aand returning the oil to the intake of the usage-side compressor62a.

The circulation pump43ais a mechanism for increasing the pressure of the aqueous medium, and in this configuration, is a pump in which a centrifugal and/or positive-displacement pump element (not shown) is driven by a circulation pump motor44a. The circulation pump43ais provided to the first usage-side water outlet tube48a. The rotational speed (i.e., operational frequency) of the circulation pump motor44acan be varied by using an inverter device (not shown), whereby the capacity of the circulation pump43acan be controlled.

The first usage unit4athereby causes the first usage-side heat exchanger41ato function as a radiator of the heat-source-side refrigerant introduced from the gas-refrigerant communication tube14, whereby hot-water supply operation is made possible in which the heat-source-side refrigerant having released heat in the first usage-side heat exchanger41ais directed out to the liquid refrigerant communication tube13, the usage-side refrigerant circulating through the usage-side refrigerant circuit40ais heated by the heat released by the heat-source-side refrigerant in the first usage-side heat exchanger41a, the usage-side refrigerant thus heated is compressed in the usage-side compressor62a, and the aqueous medium is thereafter heated by the heat released in the refrigerant/water heat exchanger65a.

Various types of sensors are provided to the first usage unit4a. Specifically provided to the first usage unit4aare a first usage-side heat exchange temperature sensor50afor detecting a first usage-side refrigerant temperature Tsc1, which is the temperature of the heat-source-side refrigerant in the liquid side of the first usage-side heat exchanger41a; a first refrigerant/water heat exchange temperature sensor73afor detecting a cascade-side refrigerant temperature Tsc2, which is the temperature of the usage-side refrigerant in the liquid side of the refrigerant/water heat exchanger65a; an aqueous medium inlet temperature sensor51afor detecting an aqueous medium inlet temperature Twr, which is the temperature of the aqueous medium in the inlet of the refrigerant/water heat exchanger65a; an aqueous medium outlet temperature sensor52afor detecting an aqueous medium outlet temperature Tw1, which is the temperature of the aqueous medium in the outlet of the refrigerant/water heat exchanger65a; a usage-side intake pressure sensor74afor detecting a usage-side intake pressure Ps2, which is the pressure of the usage-side refrigerant in the intake of the usage-side compressor62a; a usage-side discharge pressure sensor75afor detecting the usage-side discharge pressure Pd2, which is the pressure of the usage-side refrigerant in the discharge of the usage-side compressor62a; and a usage-side discharge temperature sensor76afor detecting the usage-side discharge temperature Td2, which is the temperature of the usage-side refrigerant in the discharge of the usage-side compressor62a.

The hot-water storage unit8ais installed indoors, is connected to the first usage unit4avia the aqueous medium communication tubes15a,16a, and constitutes a portion of the aqueous medium circuit80a.

The hot-water storage unit8ahas primarily a hot-water storage tank81aand a heat exchange coil82a.

The hot-water storage tank81ais a container for storing water as the aqueous medium for the hot water supply, a hot-water supply tube83afor sending the aqueous medium as hot water to a faucet, shower, or the like is connected to the top of the hot-water storage tank81a, and a water supply tube84afor replenishing the aqueous medium expended by the hot-water supply tube83ais connected to the bottom of the hot-water storage tank81a.

The heat exchange coil82ais provided inside the hot-water storage tank81a, and is a heat exchanger for functioning as a heater of the aqueous medium in the hot-water storage tank81aby exchanging heat between the aqueous medium circulating through the aqueous medium circuit80aand the aqueous medium inside the hot-water storage tank81a. The aqueous medium communication tube16ais connected to the inlet of the heat exchange coil82a, and the aqueous medium communication tube15ais connected to the outlet thereof.

The hot-water storage unit8ais thereby capable of heating the aqueous medium inside the hot-water storage tank81athrough the use of the aqueous medium circulating through the aqueous medium circuit80a, which has been heated in the first usage unit4a, and storing the heated aqueous medium as hot water. The type of hot-water storage unit8aused herein is a hot-water storage unit for storing, in a hot-water storage tank, the aqueous medium heated by heat exchange with the aqueous medium heated in the first usage unit4a, but a type of hot-water storage unit for storing an aqueous medium heated in the first usage unit4ain a hot-water storage tank may also be used.

Various sensors are also provided to the hot-water storage unit8a. Specifically, the hot-water storage unit8ais provided with a hot-water storage temperature sensor85afor detecting a hot-water storage temperature Twh, which is the temperature of the aqueous medium stored in the hot-water storage tank81a.

The hot-water air-warming unit9ais installed indoors, is connected to the first usage unit4avia the aqueous medium communication tubes15a,16a, and constitutes a portion of the aqueous medium circuit80a.

The hot-water air-warming unit9ahas primarily a heat exchange panel91a, and is composed of a radiator and/or a floor heating panel and other components.

The heat exchange panel91ais provided alongside a wall or elsewhere indoors when configured as a radiator, and is provided under the floor or elsewhere indoors when configured as a floor heating panel. The heat exchange panel91ais a heat exchanger for functioning as a radiator or heater of the aqueous medium circulated through the aqueous medium circuit80a, and the aqueous medium communication tube16ais connected to the inlet of the heat exchange panel91a, and the aqueous medium communication tube15ais connected to the outlet of the heat exchange panel91a.

The aqueous medium communication tube15ais connected to the outlet of the heat exchange coil82aof the hot-water storage unit8a, and the outlet of the heat exchange panel91aof the hot-water air-warming unit9a. The aqueous medium communication tube16ais connected to the inlet of the heat exchange coil82aof the hot-water storage unit8a, and the inlet of the heat exchange panel91aof the hot-water air-warming unit9a. The aqueous medium communication tube16ais provided with an aqueous-medium-side switching mechanism161acapable of switching between feeding the aqueous medium circulated through the aqueous medium circuit80ato both the hot-water storage unit8aand the hot-water air-warming unit9a, or to any one of the hot-water storage unit8aand the hot-water air-warming unit9a. The aqueous-medium-side switching mechanism161ais composed of a three-way valve.

A controller (not shown) for performing the following operations and/or various controls is provided to the heat pump system1.

The operation of the heat pump system1will be described next.

An operating mode of the heat pump system1is a hot-water supply operation mode for performing a hot-water supply operation (i.e., operation of the hot-water storage unit8aand the hot-water air-warming unit9a) of the first usage unit4a.

Operation in the hot-water supply operation mode of the heat pump system1is described below.

In the case that hot-water supply operation of the first usage unit4ais to be performed, the heat-source-side switching mechanism23is switched to a heat-source-side evaporating operation state (the state indicated by the broken line of the heat-source-side switching mechanism23ofFIG. 1) and the intake-return expansion valve26ais set in a closed state in the heat-source-side refrigerant circuit20. Also, in the aqueous medium circuit80a, the aqueous-medium-side switching mechanism161ais switched to a state in which the aqueous medium is fed to the hot-water storage unit8aand/or hot-water air-warming unit9a.

In the heat-source-side refrigerant circuit20in such a state, the low-pressure, heat-source-side refrigerant in the refrigeration cycle is taken into the heat-source-side compressor21via the heat-source-side intake tube21c, and is discharged to a heat-source-side discharge tube21bafter having been compressed to a high pressure in the refrigeration cycle. The high-pressure, heat-source-side refrigerant discharged to the heat-source-side discharge tube21bhas the refrigeration machine oil separated out in the oil separator22a. The refrigeration machine oil separated out from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cvia the oil return tube22b. The high-pressure, heat-source-side refrigerant from which the refrigeration machine oil has been separated out is sent from the heat source unit2to the gas-refrigerant communication tube14via the heat-source-side switching mechanism23, the second heat-source-side gas refrigerant tube23b, and the gas-side shutoff valve30.

The high-pressure, heat-source-side refrigerant sent to the gas-refrigerant communication tube14is sent to the first usage unit4a. The high-pressure, heat-source-side refrigerant sent to the first usage unit4ais sent to the first usage-side heat exchanger41avia the first usage-side gas refrigerant tube54a. The high-pressure, heat-source-side refrigerant sent to the first usage-side heat exchanger41aundergoes heat exchange with the low-pressure, usage-side refrigerant in the refrigeration cycle that is circulating through the usage-side refrigerant circuit40aand releases heat in the first usage-side heat exchanger41a. The high-pressure, heat-source-side refrigerant having released heat in the first usage-side heat exchanger41ais sent from the first usage unit4ato the liquid refrigerant communication tube13via the first usage-side flow rate adjustment valve42aand the first usage-side liquid refrigerant tube45a.

The heat-source-side refrigerant sent to the liquid refrigerant communication tube13is sent to the heat source unit2. The heat-source-side refrigerant sent to the heat source unit2is sent to the subcooler27through the liquid-side shutoff valve29. Since the heat-source-side refrigerant does not flow in the intake return tube26, the heat-source-side refrigerant sent to the subcooler27is sent to the heat-source-side expansion valve25without exchanging heat. The heat-source-side refrigerant sent to the heat-source-side expansion valve25is depressurized in the heat-source-side expansion valve25to a low-pressure gas-liquid two-phase state, and sent to the heat-source-side heat exchanger24through the heat-source-side liquid refrigerant tube24a. The low-pressure refrigerant sent to the heat-source-side heat exchanger24is heat-exchanged with the outdoor air fed by the heat-source-side fan32and evaporated in the heat-source-side heat exchanger24. The low-pressure heat-source-side refrigerant evaporated in the heat-source-side heat exchanger24is sent to the heat-source-side accumulator28through the first heat-source-side gas refrigerant tube23aand the heat-source-side switching mechanism23. The low-pressure heat-source-side refrigerant sent to the heat-source-side accumulator28is again drawn into the heat-source-side compressor21through the heat-source-side intake tube21c.

In the usage-side refrigerant circuit40a, the low-pressure, usage-side refrigerant in the refrigeration cycle that is circulating through the usage-side refrigerant circuit40ais heated and evaporated by the radiation of the heat-source-side refrigerant in the first usage-side heat exchanger41a. The low-pressure, usage-side refrigerant evaporated in the first usage-side heat exchanger41ais sent to the usage-side accumulator67avia the second cascade-side gas-refrigerant tube69a. The low-pressure, usage-side refrigerant sent to the usage-side accumulator67ais taken into the usage-side compressor62avia the cascade-side intake tube71a, is compressed to high pressure in the refrigeration cycle, and is thereafter discharged to the cascade-side discharge tube70a. The high-pressure, usage-side refrigerant discharged to the cascade-side discharge tube70ais sent to the refrigerant/water heat exchanger65avia the first cascade-side gas-refrigerant tube72a. The high-pressure, usage-side refrigerant sent to the refrigerant/water heat exchanger65aundergoes heat exchange with the aqueous medium being circulated through the aqueous medium circuit80aby the circulation pump43aand releases heat in the refrigerant/water heat exchanger65a. The high-pressure, usage-side refrigerant having released heat in the refrigerant/water heat exchanger65ais depressurized in the refrigerant/water heat exchange-side flow rate adjustment valve66ato become a low-pressure gas-liquid two-phase state, and is then sent again to the first usage-side heat exchanger41aby way of the cascade-side liquid-refrigerant tube68a.

In the aqueous medium circuit80a, the aqueous medium circulating through the aqueous medium circuit80ais heated by the radiation of the usage-side refrigerant in the refrigerant/water heat exchanger65a. The aqueous medium heated in the refrigerant/water heat exchanger65ais taken into the circulation pump43aby way of the first usage-side water outlet tube48aand pressurized, and is then sent from the first usage unit4ato the aqueous medium communication tube16a. The aqueous medium sent to the aqueous medium communication tube16ais sent to the hot-water storage unit8aand/or the hot-water air-warming unit9aby way of the aqueous-medium-side switching mechanism161a. The aqueous medium sent to the hot-water storage unit8aundergoes heat exchange with the aqueous medium inside the hot-water storage tank81aand releases heat in the heat exchange coil82a, whereby the aqueous medium inside the hot-water storage tank81ais heated. The aqueous medium sent to the hot-water air-warming unit9areleases heat in the heat exchange panel91a, whereby indoor walls or the like are heated and indoor floors are heated.

Operation in the hot-water supply operation mode for performing only hot-water supply operation of the first usage unit4ais performed in this manner.

—Discharge Saturation Temperature Control of Each Refrigerant Circuit and Degree-of-Subcooling Control of Each Heat Exchanger Outlet—

Described next is the discharge saturation temperature control of the refrigerant circuits20,40aand the degree-of-subcooling control of the outlet of the heat exchangers41a,65ain the hot-water supply operation described above.

In the heat pump system1, the usage-side refrigerant circulating through the usage-side refrigerant circuit40ais heated by heat released by the heat-source-side refrigerant circulating through the heat-source-side refrigerant circuit20in the first usage-side heat exchanger41a, as described above, and the usage-side refrigerant circuit40acan achieve a higher temperature refrigeration cycle than the refrigeration cycle in the heat-source-side refrigerant circuit20by using the heat obtained from the heat-source-side refrigerant.

Therefore, a high-temperature aqueous medium can be obtained by heat released from the usage-side refrigerant in the refrigerant/water heat exchanger65a. At this time, it is preferred that control be performed so that the refrigeration cycle in the heat-source-side refrigerant circuit20and the refrigeration cycle in the usage-side refrigerant circuit40aboth become stable in order to stably obtain a high-temperature aqueous medium.

In view of the above, in the heat pump system1, the compressors21,62aof the two refrigerant circuits20,40aare both variable capacity compressors, and discharge saturation temperatures Tc1, Tc2become predetermined target discharge saturation temperatures Tc1s, Tc2susing saturation temperatures that correspond to the pressure of the refrigerant in the discharge of the compressors21,62a(i.e., the heat-source-side discharge saturation temperature Tc1and the usage-side discharge saturation temperature Tc2) as representative values of the pressure of the refrigerant of the refrigeration cycles.

Here, the heat-source-side discharge saturation temperature Tc1is a value obtained by converting the heat-source-side discharge pressure Pd1, which is the pressure of the heat-source-side refrigerant in the discharge of the heat-source-side compressor21, to a saturation temperature corresponding to this pressure value, and the usage-side discharge saturation temperature Tc2is a value obtained by converting the usage-side discharge pressure Pd2, which is the pressure of the usage-side refrigerant in the discharge of the usage-side compressor62a, to a saturation temperature that corresponds to this pressure value.

Control is performed in the heat-source-side refrigerant circuit20so that the rotational speed (i.e., the operational frequency) of the heat-source-side compressor21is increased to increase the operating capacity of the heat-source-side compressor21in the case that the heat-source-side discharge saturation temperature Tc1is less than the target heat-source-side discharge saturation temperature Tc1s; and the rotational speed (i.e., the operational frequency) of the heat-source-side compressor21is reduced to thereby decrease the operating capacity of the heat-source-side compressor21in the case that the heat-source-side discharge saturation temperature Tc1is greater than the target heat-source-side discharge saturation temperature Tc1s. Control is performed in the usage-side refrigerant circuit40aso that the rotational speed (i.e., the operational frequency) of the usage-side compressor62ais increased to increase the operating capacity of the usage-side compressor62ain the case that the usage-side discharge saturation temperature Tc2is less than the target usage-side discharge saturation temperature Tc2s; and the rotational speed (i.e., the operational frequency) of the usage-side compressor62ais reduced to thereby decrease the operating capacity of the usage-side compressor62ain the case that the usage-side discharge saturation temperature Tc2is greater than the target usage-side discharge saturation temperature Tc2s.

The pressure of the heat-source-side refrigerant flowing through the first usage-side heat exchanger41ain the heat-source-side refrigerant circuit20is thereby made stable and the pressure of the usage-side refrigerant flowing through the refrigerant/water heat exchanger65ain the usage-side refrigerant circuit40ais made stable. Therefore, the state of the refrigeration cycle in the two refrigerant circuits20,40acan be made stable and a high-temperature aqueous medium can be stably obtained.

At this point, it is preferred that the target discharge saturation temperatures Tc1s, Tc2sbe suitably set in order to obtain an aqueous medium with a desired temperature.

In view of the above, in this heat pump system1, a predetermined target aqueous medium outlet temperature Tw1s, which is the terget value of the temperature of the aqueous medium in the outlet of the refrigerant/water heat exchanger65a, is first set for the first usage-side heat exchanger41a, and the target usage-side discharge saturation temperature Tc2sis set as a value varied by the target aqueous medium outlet temperature Tw1s. In this situation, these temperatures are set by conversion into a function in a range of 30° C. to 85° C. so that the target aqueous medium outlet temperature Tw1sis set to a high temperature, and in accompaniment therewith, the target usage-side discharge saturation temperature Tc2salso becomes a high temperature and becomes a slightly higher temperature than the target aqueous medium outlet temperature Tw1s, for example, so that the target usage-side discharge saturation temperature Tc2sis set to 85° C. in the case that the target aqueous medium outlet temperature Tw1sis set to 80° C., and the target usage-side discharge saturation temperature Tc2sis set to 30° C. in the case that the target aqueous medium outlet temperature Tw1sis set to 25° C. and the like. The target usage-side discharge saturation temperature Tc2sis thereby suitably set in accordance with the target aqueous medium outlet temperature Tw1s. A desired target aqueous medium outlet temperature Tws is therefore readily obtained and control can be performed with good responsiveness even when the target aqueous medium outlet temperature Tws has been modified.

In relation to the heat-source-side refrigerant circuit20, the target heat-source-side discharge saturation temperature Tc1sis set as a value that can vary according to the target usage-side discharge saturation temperature Tc2sor the target aqueous medium outlet temperature Tws. Here, these temperatures are set by conversion into a function in a range of 10° C. to 40° C. so that the target usage-side discharge saturation temperature Tc2sor the target aqueous medium outlet temperature Tws is set to a high temperature, and in accompaniment therewith, the target heat-source-side discharge saturation temperature Tc1salso reaches a high temperature range and also reaches a lower temperature range than the target usage-side discharge saturation temperature Tc2sor the target aqueous medium outlet temperature Tws, for example, so that the target heat-source-side discharge saturation temperature Tc1sis set to a temperature range of 35° C. to 40° C. in the case that, e.g., the target usage-side discharge saturation temperature Tc2sor the target aqueous medium outlet temperature Tws is set to 75° C. or 80° C.; and the target heat-source-side discharge saturation temperature Tc1sis set to a temperature range of 10° C. to 15° C. in the case that the target usage-side discharge saturation temperature Tc2sor the target aqueous medium outlet temperature Tws is set to 30° C. or 25° C. The target usage-side discharge saturation temperature Tc2sis preferably set to a single temperature as described above for the purpose of accurately obtaining the target aqueous medium outlet temperature Tws. However, the target heat-source-side discharge saturation temperature Tc1sis not required to have an exact setting as does the target usage-side discharge saturation temperature Tc2, and is preferably provided with a certain temperature width allowance. The target heat-source-side discharge saturation temperature Tc1sis therefore preferably set in the temperature range as described above. Since the target heat-source-side discharge saturation temperature Tc1sis thereby suitably set in accordance with the target usage-side discharge saturation temperature Tc2sor the target aqueous medium outlet temperature Tws, the refrigeration cycle can be suitably controlled in the heat-source-side refrigerant circuit20in accordance with the state of the refrigeration cycle in the usage-side refrigerant circuit40a.

In this heat pump system1, the first usage-side flow rate adjustment valve42ais provided as a mechanism for main depressurization of the heat-source-side refrigerant flowing through the heat-source-side refrigerant circuit20, and the refrigerant/water heat-exchange-side flow rate adjustment valve66ais provided as a mechanism for main depressurization of the usage-side refrigerant flowing through the usage-side refrigerant circuit40a; and the opening degree of the first usage-side flow rate adjustment valve42ais performed in the heat-source-side refrigerant circuit20so that the heat-source-side refrigerant degree-of-subcooling SC1, which is the heat-source-side refrigerant degree-of-subcooling in the outlet of the first usage-side heat exchanger41a, becomes a target heat-source-side refrigerant degree-of-subcooling SC1s, and the opening degree of the refrigerant/water heat-exchange-side flow rate adjustment valve66ais performed in the usage-side refrigerant circuit40aso that the usage-side refrigerant degree-of-subcooling SC2, which is the usage-side refrigerant degree-of-subcooling in the outlet of the refrigerant/water heat exchanger65a, becomes a target usage-side refrigerant degree-of-subcooling SC2s.

Here, the heat-source-side refrigerant degree-of-subcooling SC1is a value obtained by subtracting the first usage-side refrigerant temperature Tsc1from the heat-source-side discharge saturation temperature Tc1, and the usage-side refrigerant degree-of-subcooling SC2is a value obtained by subtracting the cascade-side refrigerant temperature Tsc2from the usage-side discharge saturation temperature Tc2.

In the heat-source-side refrigerant circuit20, the flow rate of the heat-source-side refrigerant flowing through the first usage-side heat exchanger41ais reduced by reducing the opening degree of the first usage-side flow rate adjustment valve42ain the case that the heat-source-side refrigerant degree-of-subcooling SC1is less than the target heat-source-side refrigerant degree-of-subcooling SC1s, and the flow rate of the heat-source-side refrigerant flowing through the first usage-side heat exchanger41ais increased by increasing the opening degree of the first usage-side flow rate adjustment valve42ain the case that the heat-source-side refrigerant degree-of-subcooling SC1is greater than the target heat-source-side refrigerant degree-of-subcooling SC1s. In the usage-side refrigerant circuit40a, the flow rate of the usage-side refrigerant flowing through the refrigerant/water heat exchanger65ais reduced by reducing the opening degree of the refrigerant/water heat-exchange-side flow rate adjustment valve66ain the case that the usage-side refrigerant degree-of-subcooling SC2is less than the target usage-side refrigerant degree-of-subcooling SC2s; and the flow rate of the usage-side refrigerant flowing through the refrigerant/water heat exchanger65ais increased by increasing the opening degree of the refrigerant/water heat-exchange-side flow rate adjustment valve66ain the case that the usage-side refrigerant degree-of-subcooling SC2is greater than the target usage-side refrigerant degree-of-subcooling SC2s. The target refrigerant degrees-of-subcooling SC1s, SC2sare set with consideration given, inter alia, to the design conditions of the heat exchange capacity of the first usage-side heat exchanger41aand the refrigerant/water heat exchanger65a.

The flow rate of the heat-source-side refrigerant flowing through the first usage-side heat exchanger41ain the heat-source-side refrigerant circuit20is stabilized thereby, and the flow rate of the usage-side refrigerant flowing through the refrigerant/water heat exchanger65ain the usage-side refrigerant circuit40ais stabilized thereby. Therefore, operation can be performed in conditions suitable to the heat exchange capacity of the first usage-side heat exchanger41aand the refrigerant/water heat exchanger65a, thereby contributing to the stabilization of the state of the refrigeration cycle in the two refrigerant circuits20,40a.

In this manner, in the heat pump system1, the pressure and flow rate of the refrigerant in the refrigerant circuits20,40ais stabilized by controlling the discharge saturation temperature of the refrigerant circuits20,40aand by controlling the degree of subcooling in the outlet of the heat exchangers41a,65a, whereby the state of the refrigeration cycle in the two refrigerant circuits20,40acan be stabilized and a high-temperature aqueous medium can be stably obtained.

This heat pump system1has the following characteristics.

In the first usage-side heat exchanger41ain this heat pump system1, the usage-side refrigerant circulating through the usage-side refrigerant circuit40ais heated by the heat radiation of the heat-source-side refrigerant circulating through the heat-source-side refrigerant circuit20, and the usage-side refrigerant circuit40acan use the heat obtained from the heat-source-side refrigerant to achieve a refrigeration cycle higher in temperature than the refrigeration cycle in the heat-source-side refrigerant circuit20; therefore, a high-temperature aqueous medium can be obtained by the heat radiation of the usage-side refrigerant in the refrigerant-water heat exchanger65a.

At this time, considering a circuit configuration such as that of this heat pump system1wherein the usage-side refrigerant circuit40ais included in the first usage unit4a, and the refrigerant tube is short with a length of 3 m or less from the first usage-side heat exchanger41afunctioning as an evaporator of the usage-side refrigerant to the usage-side compressor62a(i.e., the total combined length of the second cascade-side gas refrigerant tube69aand the cascade-side intake tube71a); since there is little chance of refrigeration machine oil getting backed up in portions of the usage-side refrigerant circuit40aother than the usage-side compressor62a, it is essentially believed that the amount of refrigeration machine oil enclosed with the usage-side refrigerant in the usage-side refrigerant circuit40acan be reduced.

Considering that that the objective is to obtain a high-temperature aqueous medium, the usage-side refrigerant is preferably a refrigerant with a high boiling point such as a refrigerant whose pressure corresponding to a saturation gas temperature of 65° C. is 2.8 MPa or less, or preferably 2.0 MPa or less at gauge pressure (i.e., a refrigerant having low-pressure saturation characteristics; HFC-134a in this example), as is the case in this heat pump system1, but when such a refrigerant having low-pressure saturation characteristics is used for the objective of obtaining a high-temperature aqueous medium, the gaseous usage-side refrigerant blended in with the refrigeration machine oil is increased by this use of refrigerant under high-temperature conditions. As a result, the coefficient of viscosity of the refrigeration machine oil decreases, a greater amount of refrigeration machine oil is discharged with the refrigerant from the usage-side compressor62a, and there is a risk of lubrication inside the usage-side compressor62abeing insufficient; therefore, it is believed that the amount of refrigeration machine oil enclosed with the usage-side refrigerant in the usage-side refrigerant circuit40amust be increased.

When the temperature of the refrigeration machine oil in the usage-side compressor62ais lower than the condensation temperature of the usage-side refrigerant, there is a risk that the usage-side refrigerant will condense in the usage-side compressor62aand dilute the refrigeration machine oil, but particularly in a system for obtaining a high-temperature aqueous medium such as this heat pump system1, the refrigeration machine oil is diluted quite readily because of the high condensation temperature of the usage-side refrigerant. As a result, there is a risk that the coefficient of viscosity of the refrigeration machine oil will decrease, the amount of refrigeration machine oil discharged with the refrigerant from the usage-side compressor62awill increase, and the lubrication inside the usage-side compressor62awill be insufficient; therefore, for this reason as well it is believed that the amount of refrigeration machine oil enclosed with the usage-side refrigerant in the usage-side refrigerant circuit40amust be increased. The usage-side refrigerant condenses readily and the refrigeration machine oil is diluted readily particularly with a structure such as the usage-side compressor62ain this heat pump system1, wherein a high-pressure space (not shown) filled with heat-source-side refrigerant that has been compressed in a compression element is formed inside the casing of the usage-side compressor62a, and the refrigeration machine oil accumulates in this high-pressure space.

Thus, when the amount of refrigeration machine oil is increased, an oil separation mechanism is preferably provided for separating the refrigeration machine oil discharged synchronously with the usage-side refrigerant discharged from the usage-side compressor62aand returning the oil to the intake of the usage-side compressor62a.

However, during use under high-temperature conditions such as those of this heat pump system1, since the gaseous usage-side refrigerant blended in with the refrigeration machine oil increases and the refrigeration machine oil is readily diluted as described above, the amount of refrigeration machine oil discharged along with the usage-side refrigerant discharged from the usage-side compressor62aalso increases. Therefore, when an oil separation mechanism is provided, a greater amount of usage-side refrigerant is returned to the intake of the usage-side compressor62atogether with the refrigeration machine oil, and there is a risk of operating efficiency being reduced.

In view of this, in this heat pump system1, considering the objective of obtaining a high-temperature aqueous medium (promoting dilution of the refrigeration machine oil due to a greater amount of gaseous usage-side refrigerant with a high condensation temperature being dissolved in the refrigeration machine oil, and due to condensation of the usage-side refrigerant) as well as the low risk of refrigeration machine oil backing up in portions of the usage-side refrigerant circuit40aother than the usage-side compressor62a(i.e., circuit structural characteristics, which are that the usage-side refrigerant circuit40ais included in the first usage unit4a, and the refrigerant tube has a short length of 3 m or less from the first usage-side heat exchanger41afunctioning as an evaporator of the usage-side refrigerant to the usage-side compressor62a), the usage-side refrigerant circuit40ais not provided with an oil separation mechanism for separating refrigeration machine oil included in the usage-side refrigerant discharged from the usage-side compressor62aand returning the oil to the intake of the usage-side compressor62a, and the weight of usage-side refrigerant enclosed in the usage-side refrigerant circuit40ais one to three times the weight of the refrigeration machine oil enclosed for lubricating the usage-side compressor, unlike the conventional practice concerning the weight of refrigeration machine oil.

It is thereby possible in this heat pump system1to obtain a high-temperature aqueous medium while allowing a greater amount of usage-side refrigerant to be returned with the refrigeration machine oil to the intake of the usage-side compressor62aand suppressing both the resulting decrease in operating efficiency and insufficient lubrication inside the usage-side compressor62a.

Particularly, in this heat pump system1, since HFC-134a is used as the usage-side refrigerant, an even higher-temperature aqueous medium can be obtained, and the operational effects described above are more pronounced.

In this heat pump system1, to stably obtain a high-temperature aqueous medium, the refrigeration cycle in the heat-source-side refrigerant circuit20and the refrigeration cycle in the usage-side refrigerant circuit40aare both preferably controlled so as to be stable, but in this heat pump system1, the compressors21,62aof the refrigerant circuits20,40aare both variable capacity compressors, the saturation temperatures corresponding to the refrigerant pressures in the discharges of the compressors21,62a(i.e. the heat-source-side discharge saturation temperature Tc1and the usage-side discharge saturation temperature Tc2) are used as values representing refrigerant pressures of the refrigeration cycles, and capacity control of the compressors21,62ais performed so that the discharge saturation temperatures Tc1, Tc2reach the target discharge saturation temperatures Tc1s, Tc2s; therefore, the refrigeration cycle states in the refrigerant circuits20,40acan be stabilized and a high-temperature aqueous medium can thereby be stably obtained. Moreover, in this heat pump system1, the first usage-side heat exchanger41ais a heat exchanger which directly transfers heat by heat exchange between the heat-source-side refrigerant and the usage-side refrigerant, and there is little heat loss during a transfer of heat from the heat-source-side refrigerant circuit20to the usage-side refrigerant circuit40a, which contributes to obtaining a high-temperature aqueous medium.

In the heat pump system1described above, since an oil separation mechanism is not provided to the discharge of the usage-side compressor62a, refrigeration machine oil is readily led with the usage-side refrigerant into the refrigerant-water heat exchanger65afunctioning as a radiator of the usage-side refrigerant, and under high-temperature conditions, biphasic separation of the liquid usage-side refrigerant and the refrigeration machine oil occurs readily in the refrigerant-water heat exchanger65a, and refrigeration machine oil therefore readily backs up within the refrigerant-water heat exchanger65afunctioning as a radiator of the usage-side refrigerant. As described above, when subcooling degree control of the outlet of the refrigerant-water heat exchanger65ais performed, the liquid usage-side refrigerant accumulates in the refrigerant-water heat exchanger65ain an amount corresponding to the usage-side refrigerant degree of subcooling SC2, therefore making biphasic separation of the liquid usage-side refrigerant and the refrigeration machine oil occur even more readily.

In view of this, in this heat pump system1, as shown inFIG. 2, when it has been determined that the refrigeration machine oil in the usage-side compressor62ais insufficient (step S1), an oil recovery operation is performed in which the usage-side refrigerant including refrigeration machine oil in the refrigerant-water heat exchanger65ais passed through the refrigerant-water heat-exchange-side flow rate adjustment valve66aand the first usage-side heat exchanger41a, and returned to the usage-side accumulator67awhich is in a low-temperature condition in which biphasic separation of the liquid usage-side refrigerant and refrigeration machine oil does not occur readily (step S2).

The determination of whether or not refrigeration machine oil is insufficient in the usage-side compressor62ais performed based on a usage-side discharge temperature Td2, which is the temperature of the usage-side refrigerant in the discharge of the usage-side compressor62a, or an aqueous medium outlet temperature Tw1, which is the temperature of the aqueous medium in the outlet of the refrigerant-water heat exchanger65a. More specifically, when the operation has continued for a predetermined oil insufficiency operation time to1or longer in a state in which the usage-side discharge temperature Td2is higher than a predetermined oil insufficiency discharge temperature Toc1and the operating frequency12of the usage-side compressor62ais higher than a predetermined oil insufficiency frequency foc1, or when the operation has continued for a predetermined oil insufficiency operation time to 2 or longer in a state in which the aqueous medium outlet temperature Tw1is higher than a predetermined oil insufficiency outlet temperature Toc2and the operating frequency12of the usage-side compressor62ais higher than a predetermined oil insufficiency frequency foc2, the refrigeration machine oil in the usage-side compressor62ais determined to be insufficient. Thereby, the determination of whether or not the refrigeration machine oil in the usage-side compressor62ais insufficient can be appropriately made while taking into account the extent to which the usage-side refrigerant is blended into the refrigeration machine oil in the usage-side compressor62aand the extent of biphasic separation of the usage-side refrigerant and refrigeration machine oil in the refrigerant-water heat exchanger65a.

In the oil recovery operation (step S2), the refrigerant-water heat-exchange-side flow rate adjustment valve66ais fully opened, and the operating frequency f2of the usage-side compressor62ais set to an oil recovery operation frequency foc, which is a lower frequency than the oil insufficiency frequencies foc1foc2. Thereby, the amount of refrigeration machine oil discharged with the usage-side refrigerant from the usage-side compressor62acan be reduced, and the refrigeration machine oil backed up in the refrigerant-water heat exchanger65acan be quickly expelled. Moreover, in this heat pump system1, since the refrigerant tube from the first usage-side heat exchanger41afunctioning as an evaporator of usage-side refrigerant to the usage-side compressor62ahas a short length of 3 m or less, the refrigeration machine oil expelled from the refrigerant-water heat exchanger65acan be quickly returned to the usage-side accumulator67awithout getting backed up in the refrigerant tube from the first usage-side heat exchanger41afunctioning as an evaporator of usage-side refrigerant to the usage-side compressor62a.

After a predetermined oil recovery operation time toc has elapsed (step S3), the first usage unit4ais returned to the operation state prior to the oil recovery operation (step S4).

It is thereby possible in this heat pump system1to ensure that there will be no insufficiency of refrigeration machine oil in the usage-side compressor62a. During the oil recovery operation, the operation of making the refrigerant-water heat exchanger65afunction as a radiator of usage-side refrigerant and heating the aqueous medium can be continued, and the adverse effect that the oil recovery operation has on the hot-water-supply operation can thereby be reduced as much as possible.

In the heat pump system1described above (seeFIG. 1), the usage-side refrigerant circuit40amay be further provided with a first usage-side switching mechanism64afor switching between a usage-side radiating operation state in which the refrigerant/water heat exchanger65ais made to function as a radiator of the usage-side refrigerant and the first usage-side heat exchanger41ais made to function as an evaporator of the usage-side refrigerant, and a usage-side evaporating operation state in which the refrigerant/water heat exchanger65ais made to function as an evaporator of the usage-side refrigerant and the first usage-side heat exchanger41ais made to function as a radiator of the usage-side refrigerant, as shown inFIG. 3.

Here, the first usage-side switching mechanism64ais a four-way switching valve, and is connected to the cascade-side discharge tube70a, the cascade-side intake tube71a, the first cascade-side gas-refrigerant tube72a, and the second cascade-side gas-refrigerant tube69a. The first usage-side switching mechanism64ais capable of switching between placing the cascade-side discharge tube70aand the first cascade-side gas-refrigerant tube72ain communication and the second cascade-side gas-refrigerant tube69aand the cascade-side intake tube71ain communication (corresponding to the usage-side radiating operation state; see the solid line of the first usage-side switching mechanism64ainFIG. 3), and placing the cascade-side discharge tube70aand the second cascade-side gas-refrigerant tube69ain communication and the first cascade-side gas-refrigerant tube72aand the cascade-side intake tube71ain communication (corresponding to the usage-side evaporating operation state; see the broken line of first usage-side switching mechanism64ainFIG. 3). The first usage-side switching mechanism64ais not limited to being a four-way switching valve, but may also be, e.g., a configuration in which a plurality of solenoid valves are used in combination to achieve a function similar to that described above for switching the direction of flow of the usage-side refrigerant.

With the heat pump system1having such a configuration, in the case that defrosting of the heat-source-side heat exchanger24has been determined to be required by operation of the hot-water supply operation mode, defrosting operation can be performed such that the heat-source-side switching mechanism23is set in the heat-source-side radiating operation state, whereby the heat-source-side heat exchanger24is made to function as a radiator of the heat-source-side refrigerant; and the first usage-side switching mechanism64ais set in the usage-side evaporating operation state, whereby the refrigerant/water heat exchanger65ais made to function as an evaporator of the usage-side refrigerant and the first usage-side heat exchanger41ais made to function as a radiator of the usage-side refrigerant.

Operation in the defrosting operation is described below with reference toFIG. 4.

It is first determined whether predetermined defrosting operation start conditions have been satisfied (i.e., whether defrosting of the heat-source-side heat exchanger24is required; step S21). Here, it is determined whether defrosting operation start conditions have been satisfied based on whether a defrosting time interval Δtdf (i.e., the cumulative operation time from the end of the previous defrosting operation) has reached a predetermined defrosting time interval setting value Δtdfs.

In the case that it has been determined that the defrosting operation start conditions have been satisfied, the following defrosting operation is started (step S12).

When the defrosting operation is started, the heat-source-side switching mechanism23is switched to the heat-source-side radiating operation state (the state indicated by the solid line of the heat-source-side switching mechanism23ofFIG. 3) in the heat-source-side refrigerant circuit20, and the first usage-side switching mechanism64ais switched to the usage-side evaporating operation state (the state indicated by the broken line of the first usage-side switching mechanism64aofFIG. 3) in the usage-side refrigerant circuit40a, and the intake return expansion valve26ais set in a closed state.

In the heat-source-side refrigerant circuit20in such a state, the low-pressure heat-source-side refrigerant in the refrigeration cycle is taken into the heat-source-side compressor21by way of the heat-source-side intake tube21c, compressed to high pressure in the refrigeration cycle, and thereafter discharged to the heat-source-side discharge tube21b. The high-pressure heat-source-side refrigerant discharged to the heat-source-side discharge tube21bhas the refrigeration machine oil separated out in the oil separator22a. The refrigeration machine oil separated out from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cby way of the oil return tube22b. The high-pressure, heat-source-side refrigerant from which the refrigeration machine oil has been separated out is sent to the heat-source-side heat exchanger24by way of the heat-source-side switching mechanism23and the first heat-source-side gas-refrigerant tube23a. The high-pressure, heat-source-side refrigerant sent to the heat-source-side heat exchanger24undergoes heat exchange with ice deposited in the heat-source-side heat exchanger24and heat is released in the heat-source-side heat exchanger24. The high-pressure, heat-source-side refrigerant having released heat in the heat-source-side heat exchanger is sent to the subcooler27by way of the heat-source-side expansion valve25. The heat-source-side refrigerant sent to the subcooler27is sent from the heat source unit2to the liquid refrigerant communication tube13by way of the heat-source-side liquid-refrigerant tube24aand the liquid-side shutoff valve29without undergoing heat exchange because the heat-source-side refrigerant does not flow in the intake return tube26.

The heat-source-side refrigerant sent to the liquid refrigerant communication tube13is sent to the first usage unit4a.

The heat-source-side refrigerant sent to the first usage unit4ais sent to the first usage-side flow rate adjustment valve42a. The heat-source-side refrigerant sent to the first usage-side flow rate adjustment valve42ais depressurized in the first usage-side flow rate adjustment valve42ato a low-pressure gas-liquid two-phase state, and sent to the first usage-side heat exchanger41athrough the first usage-side liquid refrigerant tube45a. The low-pressure heat-source-side refrigerant sent to the first usage-side heat exchanger41ais heat-exchanged with the high-pressure usage-side refrigerant in the refrigeration cycle that circulates through the usage-side refrigerant circuit40aand evaporated in the first usage-side heat exchanger41a. The low-pressure heat-source-side refrigerant evaporated in the first usage-side heat exchanger41ais sent from the first usage unit4ato the gas refrigerant communication tube14through the first usage-side gas refrigerant tube54a.

The heat-source-side refrigerant sent from the first usage unit4ato the gas refrigerant communication tube14is sent to the heat source unit2. The low-pressure heat-source-side refrigerant sent to the heat source unit2is sent to the heat-source-side accumulator28through the gas-side shutoff valve30, the second heat-source-side gas refrigerant tube23b, and the heat-source-side switching mechanism23. The low-pressure heat-source-side refrigerant sent to the heat-source-side accumulator28is again drawn into the heat-source-side compressor21through the heat-source-side intake tube21c.

The high-pressure, usage-side refrigerant in the refrigeration cycle that circulates through the usage-side refrigerant circuit40areleases heat in the usage-side refrigerant circuit40aby the evaporation of the heat-source-side refrigerant in the first usage-side heat exchanger41a. The high-pressure, usage-side refrigerant having released heat in the first usage-side heat exchanger41ais sent to the refrigerant/water heat exchange-side flow rate adjustment valve66a. The high-pressure, usage-side refrigerant sent to the refrigerant/water heat exchange-side flow rate adjustment valve66ais depressurized in the refrigerant/water heat exchange-side flow rate adjustment valve66ato become a low-pressure gas-liquid two-phase state, and is then sent to the refrigerant/water heat exchanger65aby way of the cascade-side liquid-refrigerant tube68a. The low-pressure, usage-side refrigerant sent to the refrigerant/water heat exchanger65aundergoes heat exchange with the aqueous medium circulated through the aqueous medium circuit80aby the circulation pump43aand evaporates in the refrigerant/water heat exchanger65a. The low-pressure, usage-side refrigerant thus evaporated in the refrigerant/water heat exchanger65ais sent to the usage-side accumulator67aby way of the first cascade-side gas-refrigerant tube72aand the second usage-side switching mechanism64a. The low-pressure, usage-side refrigerant sent to the usage-side accumulator67ais taken into the usage-side compressor62aby way of the cascade-side intake tube71a, compressed to high pressure in the refrigeration cycle, and thereafter discharged to the cascade-side discharge tube70a. The high-pressure, usage-side refrigerant discharged to the cascade-side discharge tube70ais again sent to the first usage-side heat exchanger41aby way of the second usage-side switching mechanism64aand the second cascade-side gas-refrigerant tube69a.

In this manner, the defrosting operation is started in which the heat-source-side switching mechanism23is set in the heat-source-side radiating operation state to thereby cause the heat-source-side heat exchanger24to function as a radiator of the heat-source-side refrigerant; and the first usage-side switching mechanism64ais set in the usage-side evaporating operation state to thereby cause the refrigerant/water heat exchanger65ato function as an evaporator of the usage-side refrigerant and cause the first usage-side heat exchanger41ato function as a radiator of the usage-side refrigerant (i.e., as an evaporator of the heat-source-side refrigerant).

It is determined whether predetermined defrosting operation end conditions have been satisfied (i.e., whether defrosting of the heat-source-side heat exchanger24has ended; step S13). Here, it is determined whether the defrosting operation end conditions have been satisfied depending on whether the heat-source-side heat exchanger temperature Thx has reached the predetermined defrosting completion temperature Thxs, or whether the defrosting operation time tdf, which is the time elapsed from the start of the defrosting operation, has reached a predetermined defrosting operation setting time tdfs.

In the case that it has been determined that the defrosting operation end conditions have been satisfied, the defrosting operation is ended and the process returns to the hot-water supply operation mode, the air-warming operation mode, and/or the hot-water supply/air-warming operation mode (step S14).

Thereby, when the heat-source-side heat exchanger24is defrosted in this heat pump system1, not only is the heat-source-side heat exchanger24made to function as a radiator of heat-source-side refrigerant by putting the heat-source-side switching mechanism23into the heat-source-side radiating operation state, but the refrigerant-water heat exchanger65ais made to function as an evaporator of usage-side refrigerant and the first usage-side heat exchanger41ais made to function as a radiator of usage-side refrigerant by putting the first usage-side switching mechanism64ainto the usage-side evaporating operation state; therefore, the heat-source-side refrigerant cooled by heat radiation in the heat-source-side heat exchanger24can be heated by the heat radiation of the usage-side refrigerant in the first usage-side heat exchanger41a, the usage-side refrigerant cooled by heat radiation in the first usage-side heat exchanger41acan be heated by being evaporated in the refrigerant-water heat exchanger65a, and the heat-source-side heat exchanger24can thereby be reliably defrosted.

In the heat pump system1having this type of configuration, when the oil recovery operation becomes necessary in the hot-water-supply operation mode, the oil recovery operation of Modification 1 of the first embodiment can be performed while the first usage-side switching mechanism64ais kept in the usage-side radiating operation state (i.e., is not switched).

With the heat pump system1described above (seeFIGS. 1 and 3), a single first usage unit4ais connected to the heat source unit2via the refrigerant communication tubes13,14, but a plurality of first usage units4a,4b(two, in this case) may be connected in parallel to each other via the refrigerant communication tubes13,14, as shown inFIG. 5(in this case, the hot-water/air-warming unit, the hot-water storage unit, the aqueous medium circuits80a,80b, and the like are not shown). The configuration of the first usage unit4bis the same as the configuration of the first usage unit4awith the subscript “b” used in place of the subscript “a” of the reference numerals indicating each part of the first usage unit4a, and a description of each part of the first usage unit4bis therefore omitted. With this heat pump system1, it is possible to accommodate a plurality of locations and/or applications that require heating of the aqueous medium.

In the heat pump system1in the first embodiment and modifications thereof described above (seeFIGS. 1,3, and5), it is preferred that hot-water supply operation as well as indoor air warming can be performed.

In view of the above, with a heat pump system200, a second usage-side heat exchanger101a, which is capable of heating an air medium by functioning as a radiator of the heat-source-side refrigerant in the configuration of the heat pump system1(seeFIG. 1) according to the first embodiment described above, is further provided to the heat-source-side refrigerant circuit20, as shown inFIG. 7. The configuration of the heat pump system200is described below.

FIG. 6is a view showing the general configuration of the heat pump system200according to a second embodiment of the present invention. The heat pump system200is an apparatus capable of performing operation for heating an aqueous medium and performing other operations using a vapor compression heat pump cycle.

The heat pump system200mainly has a heat source unit2, a first usage unit4a, a second usage unit10a, a liquid-refrigerant communication tube13, a gas-refrigerant communication tube14, a hot-water storage unit8a, a hot-water air-warming unit9a, an aqueous medium communication tube15a, and an aqueous medium communication tube16a. The heat source unit2, the first usage unit4a, and the second usage unit10aare connected via the refrigerant communication tubes13,14to thereby constitute a heat-source-side refrigerant circuit20. The first usage unit4aconstitutes a usage-side refrigerant circuit40a. The first usage unit4a, the hot-water storage unit8a, and the hot-water air-warming unit9aare connected via the aqueous medium communication tubes15a,16ato thereby constitute an aqueous medium circuit80a. HFC-410A, which is a type of HFC-based refrigerant, is enclosed inside the heat-source-side refrigerant circuit20as a heat-source-side refrigerant, and an ester-based or ether-based refrigeration machine oil having compatibility in relation to the HFC-based refrigerant is enclosed for lubrication of the heat-source-side compressor21. HFC-134a, which is a type of HFC-based refrigerant, is enclosed inside the usage-side refrigerant circuit40aas a usage-side refrigerant, and an ester-based or ether-based refrigeration machine oil having compatibility in relation to the HFC-based refrigerant is enclosed for lubrication of the usage-side compressor62a. The usage-side refrigerant is preferably one in which the pressure that corresponds to a saturated gas temperature of 65° C. is a maximum gauge pressure of 2.8 MPa or less, and more preferably 2.0 MPa or less from the viewpoint of using a refrigerant that is advantageous for a high-temperature refrigeration cycle. The weight of the usage-side refrigerant enclosed in the usage-side refrigerant circuit40ais one to three times the weight of the refrigeration machine oil enclosed in order to lubricate the usage-side compressor62a. HFC-134a is a type of refrigerant having such saturation pressure characteristics. Water constituting the aqueous medium circulates in the aqueous medium circuit80a.

In the description related to the configurations below, the same reference numerals will be used and a description omitted for the configuration of the heat source unit2, the first usage unit4a, the hot-water storage unit8a, the hot-water air-warming unit9a, the liquid refrigerant communication tube13, the gas-refrigerant communication tube14, and the aqueous medium communication tubes15a,16a, all of which have the same configuration as those of heat pump system1in the first embodiment (seeFIG. 1). Only the configuration of the second usage unit10awill be described.

The second usage unit10ais installed indoors, is connected to the heat source unit2via the refrigerant communication tubes13,14, and constitutes a portion of the heat-source-side refrigerant circuit20.

The second usage unit10ahas primarily a second usage-side heat exchanger101aand a second usage-side flow rate adjustment valve102a.

The second usage-side heat exchanger101ais a heat exchanger for functioning as a radiator or evaporator of the heat-source-side refrigerant by exchanging heat between the heat-source-side refrigerant and indoor air as the air medium, a second usage-side liquid refrigerant tube103ais connected to the liquid side of the second usage-side heat exchanger101a, and a second usage-side gas refrigerant tube104ais connected to the gas side of the second usage-side heat exchanger101a. The liquid refrigerant communication tube13is connected to the second usage-side liquid refrigerant tube103a, and the gas refrigerant communication tube14is connected to the second usage-side gas refrigerant tube104a.

The air medium for exchanging heat with the heat-source-side refrigerant in the second usage-side heat exchanger101ais fed by a usage-side fan105adriven by a usage-side fan motor106a.

The second usage-side flow rate adjustment valve102ais an electrical expansion valve whereby the flow rate of heat-source-side refrigerant flowing through the second usage-side heat exchanger101acan be varied by controlling the opening degree of the second usage-side flow rate adjustment valve102a, and the second usage-side flow rate adjustment valve102ais provided to the second usage-side liquid refrigerant tube103a.

The second usage unit10ais thereby configured so that an air-cooling operation can be performed in which the second usage-side heat exchanger101ais caused to function as an evaporator of the heat-source-side refrigerant introduced from the liquid refrigerant communication tube13in the heat-source-side radiating operation state of the heat-source-side switching mechanism23, whereby the heat-source-side refrigerant evaporated in the second usage-side heat exchanger101ais directed to the gas refrigerant communication tube14, and the air medium is cooled by evaporation of the heat-source-side refrigerant in the second usage-side heat exchanger101a. The second usage unit10ais also configured so that an air-warming operation can be performed in which the second usage-side heat exchanger101ais caused to function as a radiator of the heat-source-side refrigerant introduced from the gas refrigerant communication tube14in the heat-source-side evaporating operation state of the heat-source-side switching mechanism23, whereby the heat-source-side refrigerant radiated in the second usage-side heat exchanger101ais directed to the liquid refrigerant communication tube13, and the air medium is heated by radiation of the heat-source-side refrigerant in the second usage-side heat exchanger101a.

Various sensors are provided to the second usage unit10a. Specifically, the second usage unit10ais provided with an outdoor temperature sensor107afor detecting an outdoor temperature Tr.

A control unit (not shown) for performing the following operations and/or various controls is provided to the heat pump system200.

Next, the operation of the heat pump system200will be described.

The operation modes of the heat pump system200include a hot-water supply operation mode in which only the hot-water supply operation of the first usage unit4ais performed (i.e., operation of the hot-water storage unit8aand/or the hot-water air-warming unit9a), an air-cooling operation mode in which only air-cooling operation of the second usage unit10ais performed, an air-warming operation mode in which only air-warming operation of the second usage unit10ais performed, and a hot-water supply/air-warming operation mode in which hot-water supply operation of the first usage unit4ais performed together with the air-warming operation of the second usage unit10a.

Operation in the four operation modes of the heat pump system200is described below.

In the case that only hot-water supply operation of the first usage unit4ais to be performed, the heat-source-side switching mechanism23is switched to the heat-source-side evaporating operation state (the state of the heat-source-side switching mechanism23indicated by the broken line inFIG. 6) in the heat-source-side refrigerant circuit20, and an intake-return expansion valve26aand the second usage-side flow rate adjustment valve102aare set in a closed state. Also, in the aqueous medium circuit80a, the aqueous-medium-side switching mechanism161ais switched to a state in which the aqueous medium is fed to the hot-water storage unit8aand/or hot-water air-warming unit9a.

In the heat-source-side refrigerant circuit20in such a state, the low-pressure, heat-source-side refrigerant in the refrigeration cycle is taken into the heat-source-side compressor21via the heat-source-side intake tube21c, and is discharged to a heat-source-side discharge tube21bafter having been compressed to a high pressure in the refrigeration cycle. The high-pressure, heat-source-side refrigerant discharged to the heat-source-side discharge tube21bhas the refrigeration machine oil separated out in the oil separator22a. The refrigeration machine oil separated out from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cvia the oil return tube22b. The high-pressure, heat-source-side refrigerant from which the refrigeration machine oil has been separated out is sent from the heat source unit2to the gas-refrigerant communication tube14via the heat-source-side switching mechanism23, the second heat-source-side gas refrigerant tube23b, and the gas-side shutoff valve30.

The high-pressure, heat-source-side refrigerant sent to the gas-refrigerant communication tube14is sent to the first usage unit4a. The high-pressure, heat-source-side refrigerant sent to the first usage unit4ais sent to the first usage-side heat exchanger41avia the first usage-side gas refrigerant tube54a. The high-pressure, heat-source-side refrigerant sent to the first usage-side heat exchanger41aundergoes heat exchange with the low-pressure, usage-side refrigerant in the refrigeration cycle that is circulating through the usage-side refrigerant circuit40aand releases heat in the first usage-side heat exchanger41a.

The high-pressure, heat-source-side refrigerant having released heat in the first usage-side heat exchanger41ais sent from the first usage unit4ato the liquid refrigerant communication tube13via the first usage-side flow rate adjustment valve42aand the first usage-side liquid refrigerant tube45a.

The heat-source-side refrigerant sent to the liquid refrigerant communication tube13is sent to the heat source unit2. The heat-source-side refrigerant sent to the heat source unit2is sent to the subcooler27via a liquid-side shutoff valve29. The heat-source-side refrigerant sent to the subcooler27does not undergo heat exchange and is sent to the heat-source-side expansion valve25because the heat-source-side refrigerant does not flow in the intake return tube26. The heat-source-side refrigerant sent to the heat-source-side expansion valve25is depressurized in the heat-source-side expansion valve25to become a low-pressure gas-liquid two-phase state, and is then sent to the heat-source-side heat exchanger24via a heat-source-side liquid-refrigerant tube24a. The low-pressure refrigerant sent to the heat-source-side heat exchanger24undergoes heat exchange with outdoor air fed by the heat-source-side fan32and is evaporated in the heat-source-side heat exchanger24. The low-pressure, heat-source-side refrigerant evaporated in the heat-source-side heat exchanger24is sent to the heat-source-side accumulator28via the first heat-source-side gas-refrigerant tube23aand the heat-source-side switching mechanism23. The low-pressure, heat-source-side refrigerant sent to the heat-source-side accumulator28is again taken into the heat-source-side compressor21via the heat-source-side intake tube21c.

In the usage-side refrigerant circuit40a, the low-pressure, usage-side refrigerant in the refrigeration cycle that is circulating through the usage-side refrigerant circuit40ais heated and evaporated by the radiation of the heat-source-side refrigerant in the first usage-side heat exchanger41a. The low-pressure, usage-side refrigerant evaporated in the first usage-side heat exchanger41ais sent to the usage-side accumulator67avia the second cascade-side gas-refrigerant tube69a. The low-pressure, usage-side refrigerant sent to the usage-side accumulator67ais taken into the usage-side compressor62avia the cascade-side intake tube71a, is compressed to high pressure in the refrigeration cycle, and is thereafter discharged to the cascade-side discharge tube70a. The high-pressure, usage-side refrigerant discharged to the cascade-side discharge tube70ais sent to the refrigerant/water heat exchanger65avia the first cascade-side gas-refrigerant tube72a. The high-pressure, usage-side refrigerant sent to the refrigerant/water heat exchanger65aundergoes heat exchange with the aqueous medium being circulated through the aqueous medium circuit80aby the circulation pump43aand releases heat in the refrigerant/water heat exchanger65a. The high-pressure, usage-side refrigerant having released heat in the refrigerant/water heat exchanger65ais depressurized in the refrigerant/water heat-exchange-side flow rate adjustment valve66ato become a low-pressure gas-liquid two-phase state, and is then sent again to the first usage-side heat exchanger41avia the cascade-side liquid-refrigerant tube68a.

In the aqueous medium circuit80a, the aqueous medium circulating through the aqueous medium circuit80ais heated by the radiation of the usage-side refrigerant in the refrigerant/water heat exchanger65a. The aqueous medium heated in the refrigerant/water heat exchanger65ais taken into the circulation pump43avia the first usage-side water outlet tube48aand pressurized, and is then sent from the first usage unit4ato the aqueous medium communication tube16a. The aqueous medium sent to the aqueous medium communication tube16ais sent to the hot-water storage unit8aand/or the hot-water air-warming unit9avia the aqueous-medium-side switching mechanism161a. The aqueous medium sent to the hot-water storage unit8aundergoes heat exchange with the aqueous medium inside a hot-water storage tank81aand releases heat in the heat exchange coil82a, whereby the aqueous medium inside the hot-water storage tank81ais heated. The aqueous medium sent to the hot-water air-warming unit9areleases heat in the heat exchange panel91a, whereby indoor walls or the like are heated and indoor floors are heated.

Operation in the hot-water supply operation mode for performing only hot-water supply operation of the first usage unit4ais performed in this manner.

In the case that only air-cooling operation of the second usage unit10ais to be performed, the heat-source-side switching mechanism23is switched to the heat-source-side radiating operation state (the state of the heat-source-side switching mechanism23indicated by the solid line inFIG. 6) in the heat-source-side refrigerant circuit20, and the first usage-side flow rate adjustment valve42ais set in a shutoff state.

In the heat-source-side refrigerant circuit20in such a state, the heat-source-side refrigerant at the low pressure in the refrigeration cycle is drawn into the heat-source-side compressor21through the heat-source-side intake tube21cand compressed to the high pressure in the refrigeration cycle, and subsequently discharged to the heat-source-side discharge tube21b. In the oil separator22a, the refrigeration machine oil is separated from the high-pressure heat-source-side refrigerant discharged to the heat-source-side discharge tube21b. The refrigeration machine oil separated from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cthrough the oil return tube22b. The high-pressure heat-source-side refrigerant from which the refrigeration machine oil has been separated is sent to the heat-source-side heat exchanger24through the heat-source-side switching mechanism23and the first heat-source-side gas refrigerant tube23a. The high-pressure heat-source-side refrigerant sent to the heat-source-side heat exchanger24is heat-exchanged with the outdoor air fed by the heat-source-side fan32and radiated in the heat-source-side heat exchanger24. The high-pressure heat-source-side refrigerant radiated in the heat-source-side heat exchanger is sent to the subcooler27through the heat-source-side expansion valve25. The heat-source-side refrigerant sent to the subcooler27is heat-exchanged with the heat-source-side refrigerant diverted to the intake return tube26from the heat-source-side liquid refrigerant tube24a, and is cooled to a subcooled state. The heat-source-side refrigerant flowing through the intake return tube26is returned to the heat-source-side intake tube21c. The heat-source-side refrigerant cooled in the subcooler27is sent from the heat source unit2to the liquid refrigerant communication tube13through the heat-source-side liquid refrigerant tube24aand the liquid-side shutoff valve29.

The high-pressure heat-source-side refrigerant sent to the liquid refrigerant communication tube13is sent to the second usage unit10a. The high-pressure heat-source-side refrigerant sent to the second usage unit10ais sent to the second usage-side flow rate adjustment valve102a. The high-pressure heat-source-side refrigerant sent to the second usage-side flow rate adjustment valve102ais depressurized in the second usage-side flow rate adjustment valve102ato a low-pressure gas-liquid two-phase state, and sent to the second usage-side heat exchanger101athrough the second usage-side liquid refrigerant tube103a. The low-pressure heat-source-side refrigerant sent to the second usage-side heat exchanger101ais heat-exchanged with the air medium fed by the usage-side fan105aand evaporated in the second usage-side heat exchanger101a, and indoor air cooling is thereby performed. The low-pressure heat-source-side refrigerant evaporated in the second usage-side heat exchanger101ais sent from the second usage unit10ato the gas refrigerant communication tube14through the second usage-side gas refrigerant tube104a.

The low-pressure heat-source-side refrigerant sent to the gas refrigerant communication tube14is sent to the heat source unit2. The low-pressure heat-source-side refrigerant sent to the heat source unit2is sent to the heat-source-side accumulator28through the gas-side shutoff valve30, the second heat-source-side gas refrigerant tube23b, and the heat-source-side switching mechanism23. The low-pressure heat-source-side refrigerant sent to the heat-source-side accumulator28is again drawn into the heat-source-side compressor21through the heat-source-side intake tube21c.

The operations in the air-cooling operation mode for performing only the air-cooling operation of the second usage unit10aare thus performed.

In the case that only air-warming operation of the second usage unit10ais to be performed, the heat-source-side switching mechanism23is switched to the heat-source-side evaporating operation state (the state of the heat-source-side switching mechanism23indicated by the broken line inFIG. 6) in the heat-source-side refrigerant circuit20, and the intake-return expansion valve26aand the first usage-side flow rate adjustment valve42aare in a shutoff state.

In the heat-source-side refrigerant circuit20in such a state, the heat-source-side refrigerant at a low pressure in the refrigeration cycle is drawn into the heat-source-side compressor21through the heat-source-side intake tube21cand compressed to a high pressure in the refrigeration cycle, and subsequently discharged to the heat-source-side discharge tube21b. In the oil separator22a, the refrigeration machine oil is separated from the high-pressure heat-source-side refrigerant discharged to the heat-source-side discharge tube21b. The refrigeration machine oil separated from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cthrough the oil return tube22b. The high-pressure heat-source-side refrigerant from which the refrigeration machine oil has been separated is sent from the heat source unit2to the gas refrigerant communication tube14through the heat-source-side switching mechanism23, the second heat-source-side gas refrigerant tube23b, and the gas-side shutoff valve30.

The high-pressure heat-source-side refrigerant sent to the gas refrigerant communication tube14is sent to the second usage unit10a. The high-pressure heat-source-side refrigerant sent to the second usage unit10ais sent to the second usage-side heat exchanger101athrough the second usage-side gas refrigerant tube104a. The high-pressure heat-source-side refrigerant sent to the second usage-side heat exchanger101ais heat-exchanged with the air medium fed by the usage-side fan105aand radiated in the second usage-side heat exchanger101a, and indoor air warming is thereby performed. The high-pressure heat-source-side refrigerant radiated in the second usage-side heat exchanger101ais sent from the second usage unit10ato the liquid refrigerant communication tube13through the second usage-side flow rate adjustment valve102aand the second usage-side liquid refrigerant tube103a.

The heat-source-side refrigerant sent to the liquid refrigerant communication tube13is sent to the heat source unit2. The heat-source-side refrigerant sent to the heat source unit2is sent to the subcooler27through the liquid-side shutoff valve29. Since the heat-source-side refrigerant does not flow in the intake return tube26, the heat-source-side refrigerant sent to the subcooler27is sent to the heat-source-side expansion valve25without exchanging heat. The heat-source-side refrigerant sent to the heat-source-side expansion valve25is depressurized in the heat-source-side expansion valve25to a low-pressure gas-liquid two-phase state, and sent to the heat-source-side heat exchanger24through the heat-source-side liquid refrigerant tube24a. The low-pressure refrigerant sent to the heat-source-side heat exchanger24is heat-exchanged with the outdoor air fed by the heat-source-side fan32and evaporated in the heat-source-side heat exchanger24. The low-pressure heat-source-side refrigerant evaporated in the heat-source-side heat exchanger24is sent to the heat-source-side accumulator28through the first heat-source-side gas refrigerant tube23aand the heat-source-side switching mechanism23. The low-pressure heat-source-side refrigerant sent to the heat-source-side accumulator28is again drawn into the heat-source-side compressor21through the heat-source-side intake tube21c.

The operations in the air-warming operation mode for performing only the air-warming operation of the second usage unit10aare thus performed.

In the case that hot-water supply operation of the first usage unit4aand the air-warming operation of the second usage unit10aare to be performed together, the heat-source-side switching mechanism23is switched to the heat-source-side evaporating operation state (the state of the heat-source-side switching mechanism23indicated by the broken line inFIG. 6) in the heat-source-side refrigerant circuit20, and the intake-return expansion valve26ais in a shutoff state. Also, the aqueous-medium-side switching mechanism161ais switched in the aqueous medium circuit80ato a state in which the aqueous medium is fed to the hot-water storage unit8aand/or the hot-water air-warming unit9a.

In the heat-source-side refrigerant circuit20in such a state, the low-pressure, heat-source-side refrigerant in the refrigeration cycle is taken into the heat-source-side compressor21via the heat-source-side intake tube21c, is compressed to high pressure in the refrigeration cycle, and is thereafter discharged to the heat-source-side discharge tube21b. The high-pressure, heat-source-side refrigerant discharged to the heat-source-side discharge tube21bhas the refrigeration machine oil separated out in the oil separator22a. The refrigeration machine oil separated out from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cvia the oil return tube22b. The high-pressure, heat-source-side refrigerant from which the refrigeration machine oil has been separated out is sent from the heat source unit2to the gas-refrigerant communication tube14via the heat-source-side switching mechanism23, the second heat-source-side gas refrigerant tube23b, and the gas-side shutoff valve30.

The high-pressure, heat-source-side refrigerant sent to the gas-refrigerant communication tube14is sent to the first usage unit4aand the second usage unit10a.

The high-pressure heat-source-side refrigerant sent to the second usage unit10ais sent to the second usage-side heat exchanger101athrough the second usage-side gas refrigerant tube104a. The high-pressure heat-source-side refrigerant sent to the second usage-side heat exchanger101aundergoes heat exchange with the air medium fed by the usage-side fan105aand releases heat in the second usage-side heat exchanger101a, whereby indoor air warming is performed. The high-pressure heat-source-side refrigerant having released heat in the second usage-side heat exchanger101ais sent from the second usage unit10ato the liquid refrigerant communication tube13through the second usage-side flow rate adjustment valve102aand the second usage-side liquid refrigerant tube103a.

The high-pressure heat-source-side refrigerant sent to the first usage unit4ais sent to the first usage-side heat exchanger41athrough the first usage-side gas refrigerant tube54a. The high-pressure heat-source-side refrigerant sent to the first usage-side heat exchanger41aundergoes heat exchange with the low-pressure, usage-side refrigerant in the refrigeration cycle that is circulating through the usage-side refrigerant circuit40aand releases heat in the first usage-side heat exchanger41a. The high-pressure, heat-source-side refrigerant having released heat in the first usage-side heat exchanger41ais sent from the first usage unit4ato the liquid refrigerant communication tube13via the first usage-side flow rate adjustment valve42aand the first usage-side liquid refrigerant tube45a.

The heat-source-side refrigerant sent from the first usage unit4aand the second usage unit10ato the liquid refrigerant communication tube13merges in the liquid refrigerant communication tube13and is sent to the heat source unit2. The heat-source-side refrigerant sent to the heat source unit2is sent to the subcooler27through the liquid-side shutoff valve29. Since the heat-source-side refrigerant does not flow in the intake return tube26, the heat-source-side refrigerant sent to the subcooler27is sent to the heat-source-side expansion valve25without exchanging heat. The heat-source-side refrigerant sent to the heat-source-side expansion valve25is depressurized in the heat-source-side expansion valve25to a low-pressure gas-liquid two-phase state and sent to the heat-source-side heat exchanger24through the heat-source-side liquid refrigerant tube24a. The low-pressure refrigerant sent to the heat-source-side heat exchanger24is heat-exchanged with the outdoor air fed by the heat-source-side fan32and evaporated in the heat-source-side heat exchanger24. The low-pressure heat-source-side refrigerant evaporated in the heat-source-side heat exchanger24is sent to the heat-source-side accumulator28through the first heat-source-side gas refrigerant tube23aand the heat-source-side switching mechanism23. The low-pressure heat-source-side refrigerant sent to the heat-source-side accumulator28is again drawn into the heat-source-side compressor21through the heat-source-side intake tube21c.

In the usage-side refrigerant circuit40a, the low-pressure usage-side refrigerant in the refrigeration cycle that is circulated through the usage-side refrigerant circuit40ais heated and evaporated by the heat released by the heat-source-side refrigerant in the first usage-side heat exchanger41a. The low-pressure usage-side refrigerant evaporated in the first usage-side heat exchanger41ais sent to the usage-side accumulator67athrough the second cascade-side gas-refrigerant tube69a. The low-pressure usage-side refrigerant sent to the usage-side accumulator67ais drawn into the usage-side compressor62athrough the cascade-side intake tube71a, compressed to high pressure in the refrigeration cycle, and thereafter discharged to the cascade-side discharge tube70a. The high-pressure usage-side refrigerant discharged to the cascade-side discharge tube70ais sent to the refrigerant/water heat exchanger65athrough the first cascade-side gas-refrigerant tube72a. The high-pressure usage-side refrigerant sent to the refrigerant/water heat exchanger65aundergoes heat exchange with the aqueous medium being circulated through the aqueous medium circuit80aby the circulation pump43aand releases heat in the refrigerant/water heat exchanger65a. The high-pressure usage-side refrigerant having released heat in the refrigerant/water heat exchanger65ais depressurized in the refrigerant/water heat-exchange-side flow rate adjustment valve66ato a low-pressure gas-liquid two-phase state, and is again sent to the first usage-side heat exchanger41athrough the cascade-side liquid-refrigerant tube68a.

The aqueous medium circulating through the aqueous medium circuit80ais heated in the aqueous medium circuit80aby the heat released by the usage-side refrigerant in the refrigerant/water heat exchanger65a. The aqueous medium heated in the refrigerant/water heat exchanger65ais drawn into the circulation pump43athrough the first usage-side water outlet tube48a, pressurized, and subsequently sent from the first usage unit4ato the aqueous medium communication tube16a. The aqueous medium sent to the aqueous medium communication tube16ais sent to the hot-water storage unit8aand/or the hot-water air-warming unit9athrough the aqueous medium-side switching mechanism161a. The aqueous medium sent to the hot-water storage unit8aundergoes heat exchange with the aqueous medium inside the hot-water storage tank81aand releases heat in the heat exchange coil82a, whereby the aqueous medium in the hot-water storage tank81ais heated. The aqueous medium sent to the hot-water air-warming unit9ais radiated in the heat exchange panel91a, the walls and other indoor areas are thereby heated, and the indoor floor is heated.

The operations in the hot-water supply/air-warming operation mode for performing the hot-water supply operation of the first usage unit4aas well as the air-warming operation of the second usage unit10aare thus performed.

In the configuration of the heat pump system200in which the first usage unit4afor the hot-water-supply operation and the second usage unit10afor the air-cooling and air-warming operations are connected to the heat source unit2, discharge saturation temperature control of the refrigerant circuits20,40aand subcooling degree control of the outlets of the heat exchangers41a,65aare performed, similar to the heat pump system1(seeFIG. 1) in the first embodiment.

It is thereby possible with this heat pump system200to achieve the same operational effects as the heat pump system1in the first embodiment. Since the second usage unit10ahaving the second usage-side heat exchanger101ais provided and it is possible to perform the operation (the air-warming operation in this case) of heating the air medium by the heat radiation of the heat-source-side refrigerant in the second usage-side heat exchanger101aas well as the operation (the air-cooling operation in this case) of cooling the air medium by the evaporation of the heat-source-side refrigerant in the second usage-side heat exchanger101a, not only can the aqueous medium heated in the first usage-side heat exchanger41aand the usage-side refrigerant circuit40abe used to supply hot water, but the air medium heated in the second usage-side heat exchanger101acan be used for air-warming of the room interior as well.

Even in a configuration such as that of the above-described heat pump system200(seeFIG. 6) in which the first usage unit4afor the hot-water-supply operation and the second usage unit10afor the air-cooling and air-warming operations are connected to the heat source unit2, since an oil separation mechanism is not provided to the discharge of the usage-side compressor62asimilar to the heat pump system1(seeFIG. 1) in Modification 1 of the first embodiment, the refrigeration machine oil is readily led with the usage-side refrigerant into the refrigerant-water heat exchanger65afunctioning as a radiator of usage-side refrigerant, and under high-temperature conditions, biphasic separation of the liquid usage-side refrigerant and the refrigeration machine oil readily occurs in the refrigerant-water heat exchanger65a; therefore, refrigeration machine oil readily gets backed up in the refrigerant-water heat exchanger65afunctioning as a radiator of usage-side refrigerant. When subcooling degree control of the outlet of the refrigerant-water heat exchanger65ais being performed, liquid usage-side refrigerant in an amount corresponding to the usage-side refrigerant degree of subcooling SC2accumulates in the refrigerant-water heat exchanger65a, and biphasic separation of the liquid usage-side refrigerant and the refrigeration machine oil therefore occurs even more readily.

In view of this, the same oil recovery operation control (seeFIG. 2) as that of the heat pump system1(seeFIG. 1) of the first embodiment is performed in this heat pump system200as well.

It is thereby possible to ensure that there will be no insufficiency of refrigeration machine oil in the usage-side compressor62a. During the oil recovery operation, the operation of making the refrigerant-water heat exchanger65afunction as a radiator of usage-side refrigerant and heating the aqueous medium can be continued, and the adverse effect that the oil recovery operation has on the hot-water-supply operation and on the hot-water-supply/air-warming operation can thereby be reduced as much as possible.

In the heat pump system200described above (seeFIG. 6), the usage-side refrigerant circuit40amay be further provided with a first usage-side switching mechanism64acapable of switching between a usage-side radiating operation state in which the refrigerant/water heat exchanger65ais made to function as a radiator of the usage-side refrigerant and the first usage-side heat exchanger41ais made to function as an evaporator of the usage-side refrigerant, and a usage-side evaporating operation state in which the refrigerant/water heat exchanger65ais made to function as an evaporator of the usage-side refrigerant and the first usage-side heat exchanger41ais made to function as a radiator of the usage-side refrigerant, as shown inFIG. 7, in the same manner as the heat pump system1in Modification 2 of the first embodiment (seeFIG. 3), even in a configuration in which the first usage unit4afor hot-water supply operation and the second usage unit10afor air-warming and cooling operations are connected to the heat source unit2.

In the heat pump system200having such a configuration, in the case that defrosting of the heat-source-side heat exchanger24has been determined to be required by operation of the hot-water supply operation mode, the air-warming operation mode, and/or the hot-water supply/air-warming operation mode, defrosting operation can be performed in which the heat-source-side switching mechanism23is set in the heat-source-side radiating operation state, whereby the heat-source-side heat exchanger24is made to function as a radiator of the heat-source-side refrigerant, and the second usage-side heat exchanger101ais made to function as an evaporator of the heat-source-side refrigerant; and the first usage-side switching mechanism64ais set in the usage-side evaporating operation state, whereby the refrigerant/water heat exchanger65ais made to function as an evaporator of the usage-side refrigerant and the first usage-side heat exchanger41ais made to function as a radiator of the usage-side refrigerant.

Operation in the defrosting operation is described below with reference toFIG. 4.

It is first determined whether predetermined defrosting operation start conditions have been satisfied (i.e., whether defrosting of the heat-source-side heat exchanger24is required; step S11). Here, it is determined whether defrosting operation start conditions have been satisfied based on whether a defrosting time interval Δtdf (i.e., the cumulative operation time from the end of the previous defrosting operation) has reached a predetermined defrosting time interval setting value Δtdfs.

In the case that it has been determined that the defrosting operation start conditions have been satisfied, the following defrosting operation is started (step S12).

When the defrosting operation is started, the heat-source-side switching mechanism23is switched to the heat-source-side radiating operation state (the state indicated by the solid line of heat-source-side switching mechanism23ofFIG. 7) in the heat-source-side refrigerant circuit20, and the first usage-side switching mechanism64ais switched to the usage-side evaporating operation state (the state indicated by the broken line of the first usage-side switching mechanism64aofFIG. 8) in the usage-side refrigerant circuit40a, and the intake return expansion valve26ais set in a closed state.

In the heat-source-side refrigerant circuit20in such a state, the low-pressure heat-source-side refrigerant in the refrigeration cycle is taken into the heat-source-side compressor21by way of the heat-source-side intake tube21c, compressed to high pressure in the refrigeration cycle, and thereafter discharged to the heat-source-side discharge tube21b. The high-pressure heat-source-side refrigerant discharged to the heat-source-side discharge tube21bhas the refrigeration machine oil separated out in the oil separator22a. The refrigeration machine oil separated out from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cby way of the oil return tube22b. The high-pressure, heat-source-side refrigerant from which the refrigeration machine oil has been separated out is sent to the heat-source-side heat exchanger24by way of the heat-source-side switching mechanism23and the first heat-source-side gas-refrigerant tube23a. The high-pressure, heat-source-side refrigerant sent to the heat-source-side heat exchanger24undergoes heat exchange with ice deposited in the heat-source-side heat exchanger24and heat is released in the heat-source-side heat exchanger24. The high-pressure, heat-source-side refrigerant having released heat in the heat-source-side heat exchanger is sent to the subcooler27by way of the heat-source-side expansion valve25. The heat-source-side refrigerant sent to the subcooler27is sent from the heat source unit2to the liquid refrigerant communication tube13by way of the heat-source-side liquid-refrigerant tube24aand the liquid-side shutoff valve29without undergoing heat exchange because the heat-source-side refrigerant does not flow in the intake return tube26.

The heat-source-side refrigerant sent to the liquid refrigerant communication tube13branches in the liquid refrigerant communication tube13and is sent to the first usage unit4aand the second usage unit10a.

The heat-source-side refrigerant sent to the second usage unit10ais sent to the second usage-side flow rate adjustment valve102a. The heat-source-side refrigerant sent to the second usage-side flow rate adjustment valve102ais depressurized in the second usage-side flow rate adjustment valve102ato become a low-pressure gas-liquid two-phase state, and is then sent to the second usage-side heat exchanger101aby way of the second usage-side liquid refrigerant tube103a. The low-pressure, heat-source-side refrigerant sent to the second usage-side heat exchanger101aundergoes heat exchange with an air medium fed by the usage-side fan105aand evaporates in the second usage-side heat exchanger101a. The low-pressure, heat-source-side refrigerant thus evaporated in the second usage-side heat exchanger101ais sent from the second usage unit10ato the gas refrigerant communication tube14by way of the second usage-side gas refrigerant tube104a.

The heat-source-side refrigerant sent to the first usage unit4ais sent to the first usage-side flow rate adjustment valve42a. The heat-source-side refrigerant sent to the first usage-side flow rate adjustment valve42ais depressurized in the first usage-side flow rate adjustment valve42ato become a low-pressure gas-liquid two-phase state, and is then sent to the first usage-side heat exchanger41aby way of the first usage-side liquid refrigerant tube45a. The low-pressure, heat-source-side refrigerant sent to the first usage-side heat exchanger41aundergoes heat exchange with the high-pressure usage-side refrigerant in the refrigeration cycle that is circulated through the usage-side refrigerant circuit40aand evaporates in the first usage-side heat exchanger41a. The low-pressure, heat-source-side refrigerant thus evaporated in the first usage-side heat exchanger41ais sent from the first usage unit4ato the gas refrigerant communication tube14by way of the first usage-side gas refrigerant tube54aand the first usage-side gas on-off valve56aconstituting the first usage-side switching mechanism53a.

The heat-source-side refrigerant sent from the second usage unit10aand the first usage unit4ato the gas refrigerant communication tube14merges in the gas refrigerant communication tube14and is sent to the heat source unit2. The low-pressure, heat-source-side refrigerant sent to the heat source unit2is sent to the heat-source-side accumulator28by way of the gas-side shutoff valve30, the second heat-source-side gas refrigerant tube23b, and the heat-source-side switching mechanism23. The low-pressure, heat-source-side refrigerant sent to the heat-source-side accumulator28is again taken into the heat-source-side compressor21by way of the heat-source-side intake tube21c.

The high-pressure, usage-side refrigerant in the refrigeration cycle that circulates through the usage-side refrigerant circuit40areleases heat in the usage-side refrigerant circuit40aby the evaporation of the heat-source-side refrigerant in the first usage-side heat exchanger41a. The high-pressure, usage-side refrigerant having released heat in the first usage-side heat exchanger41ais sent to the refrigerant/water heat exchange-side flow rate adjustment valve66a. The high-pressure, usage-side refrigerant sent to the refrigerant/water heat exchange-side flow rate adjustment valve66ais depressurized in the refrigerant/water heat exchange-side flow rate adjustment valve66ato become a low-pressure gas-liquid two-phase state, and is then sent to the refrigerant/water heat exchanger65aby way of the cascade-side liquid-refrigerant tube68a. The low-pressure, usage-side refrigerant sent to the refrigerant/water heat exchanger65aundergoes heat exchange with the aqueous medium circulated through the aqueous medium circuit80aby the circulation pump43aand evaporates in the refrigerant/water heat exchanger65a. The low-pressure, usage-side refrigerant thus evaporated in the refrigerant/water heat exchanger65ais sent to the usage-side accumulator67aby way of the first cascade-side gas-refrigerant tube72aand the second usage-side switching mechanism64a. The low-pressure, usage-side refrigerant sent to the usage-side accumulator67ais taken into the usage-side compressor62aby way of the cascade-side intake tube71a, compressed to high pressure in the refrigeration cycle, and thereafter discharged to the cascade-side discharge tube70a. The high-pressure, usage-side refrigerant discharged to the cascade-side discharge tube70ais again sent to the first usage-side heat exchanger41aby way of the second usage-side switching mechanism64aand the second cascade-side gas-refrigerant tube69a.

In this manner, the defrosting operation is started in which the heat-source-side heat exchanger24is made to function as a radiator of the heat-source-side refrigerant by setting the heat-source-side switching mechanism23in the heat-source-side heat-release operation state; the second usage-side heat exchanger101ais made to function as an evaporator of the heat-source-side refrigerant and the refrigerant/water heat exchanger65ais made to function as an evaporator of the usage-side refrigerant by setting the second usage-side switching mechanism64ain a usage-side evaporating operation state; and the first usage-side heat exchanger41ais made to function as a radiator of the usage-side refrigerant (i.e., as an evaporator of the heat-source-side refrigerant).

It is determined whether predetermined defrosting operation end conditions have been satisfied (i.e., whether defrosting of the heat-source-side heat exchanger24has ended; step S13). Here, it is determined whether the defrosting operation end conditions have been satisfied depending on whether the heat-source-side heat exchanger temperature Thx has reached the predetermined defrosting completion temperature Thxs, or whether the defrosting operation time tdf, which is the time elapsed from the start of the defrosting operation, has reached a predetermined defrosting operation setting time tdfs.

In the case that it has been determined that the defrosting operation end conditions have been satisfied, the defrosting operation is ended and the process returns to the hot-water supply operation mode, the air-warming operation mode, and/or the hot-water supply/air-warming operation mode (step S14).

With the heat pump system200, when the heat-source-side heat exchanger24is to be defrosted, not only is the heat-source-side heat exchanger24made to function as a radiator of the heat-source-side refrigerant by setting the heat-source-side switching mechanism23in the heat-source-side heat-release operation state, but also the refrigerant/water heat exchanger65ais made to function as an evaporator of the usage-side refrigerant by setting the second usage-side switching mechanism64ain the usage-side evaporating operation state because the first usage-side heat exchanger41ais made to function as a radiator of the usage-side refrigerant, the heat-source-side refrigerant cooled by heat release in the heat-source-side heat exchanger24is heated by the radiation of the usage-side refrigerant in the first usage-side heat exchanger41a, and the usage-side refrigerant cooled by heat release in the first usage-side heat exchanger41acan be heated by evaporation in the refrigerant/water heat exchanger65a. The defrosting of the heat-source-side heat exchanger24can thereby be reliably performed. The defrosting operation time tdf can be shortened, and it is possible to prevent the air medium cooled in the second usage unit10afrom reaching a low temperature because the second usage-side heat exchanger101ais also made to function as an evaporator of the heat-source-side refrigerant.

In the heat pump system200having such a configuration, when the oil recovery operation becomes necessary in the hot-water-supply operation mode or the hot-water-supply/air-warming operation mode, the oil recovery operation of Modification 1 of the first embodiment can be performed while the first usage-side switching mechanism64ais kept in the usage-side radiating operation state (i.e., is not switched).

In the heat pump systems200described above (seeFIGS. 6 and 7), a single first usage unit4aand a single second usage unit10aare connected to the heat source unit2via the refrigerant communication tubes13,14, but a plurality of first usage units4a,4b(two, in this case) may be connected in parallel to each other via the refrigerant communication tubes13,14, and/or a plurality of second usage units10a,10b(two, in this case) may be connected in parallel to each other via the refrigerant communication tubes13,14, as shown inFIGS. 8 to 10(in this case, the hot-water/air-warming unit, the hot-water storage unit, the aqueous medium circuits80a,80b, and the like are not shown). The configuration of the first usage unit4bis the same as the configuration of the first usage unit4awith the subscript “b” used in place of the subscript “a” of the reference numerals indicating each part of the first usage unit4a, and a description of each part of the first usage unit4bis therefore omitted. Also, the configuration of the second usage unit10bis the same as the configuration of the second usage unit10awith the subscript “b” used in place of the subscript “a” of the reference numerals indicating each part of the second usage unit10b, and a description of each part is therefore omitted.

In these heat pump systems200, it is possible to accommodate a plurality of locations and/or applications that require heating of the aqueous medium, and it is possible to accommodate a plurality of locations and/or applications that require cooling of the air medium.

In the heat pump systems200described above (seeFIGS. 6 to 10), the second usage-side flow rate adjustment valves102a,102bare provided inside the second usage units10a,10b, but it is possible to omit the second usage-side flow rate adjustment valves102a,102bfrom the second usage units10a,10band to provide an expansion valve unit17having the second usage-side flow rate adjustment valves102a,102b, as shown inFIG. 11(in this case, the hot-water/air-warming unit, the hot-water storage unit, the aqueous medium circuit80a, and the like are not shown).

In the heat pump systems200in the second embodiment and modifications thereof described above (seeFIGS. 6 to 11), the air-cooling operation of the second usage unit10acannot be performed together with the hot-water supply operation of the first usage unit4a. It is therefore preferred that such hot-water supply/air-cooling operation be possible because hot-water supply operation can be performed in an operation state in which the air-cooling operation is being performed during the summer season or the like.

In view of the above, with a heat pump system300, it is possible to perform hot-water supply and air-cooling operation in which the second usage-side heat exchanger101ais made to function as an evaporator of the heat-source-side refrigerant to thereby cool an air medium, and the first usage-side heat exchanger41ais made to function as a radiator of the heat-source-side refrigerant to thereby heat an aqueous medium, as shown inFIG. 12, in the configuration of the heat pump system200of the second embodiment described above (seeFIG. 6). The configuration of the heat pump system300is described below.

FIG. 12is a view showing the general configuration of the heat pump system300according to a third embodiment of the present invention. The heat pump system300is an apparatus capable of performing operation for heating an aqueous medium and performing other operations using a vapor compression heat pump cycle.

The heat pump system300mainly has a heat source unit2, a first usage unit4a, a second usage unit10a, a discharge refrigerant communication tube12, a liquid-refrigerant communication tube13, a gas-refrigerant communication tube14, a hot-water storage unit8a, a hot-water air-warming unit9a, an aqueous medium communication tube15a, and an aqueous medium communication tube16a. The heat source unit2, the first usage unit4a, and the second usage unit10aare connected via the refrigerant communication tubes12,13,14to thereby constitute a heat-source-side refrigerant circuit20. The first usage unit4aconstitutes a usage-side refrigerant circuit40a. The first usage unit4a, the hot-water storage unit8a, and the hot-water air-warming unit9aare connected via the aqueous medium communication tubes15a,16ato thereby constitute an aqueous medium circuit80a. HFC-410A, which is a type of HFC-based refrigerant, is enclosed inside the heat-source-side refrigerant circuit20as a heat-source-side refrigerant, and an ester-based or ether-based refrigeration machine oil having compatibility in relation to the HFC-based refrigerant is enclosed for lubrication of the heat-source-side compressor21. HFC-134a, which is a type of HFC-based refrigerant, is enclosed inside the usage-side refrigerant circuit40aas a usage-side refrigerant, and an ester-based or ether-based refrigeration machine oil having compatibility in relation to the HFC-based refrigerant is enclosed for lubrication of the usage-side compressor62a. The usage-side refrigerant is preferably one in which the pressure that corresponds to a saturated gas temperature of 65° C. is a maximum gauge pressure of 2.8 MPa or less, and more preferably 2.0 MPa or less from the viewpoint of using a refrigerant that is advantageous for a high-temperature refrigeration cycle. The weight of the usage-side refrigerant enclosed in the usage-side refrigerant circuit40ais one to three times the weight of the refrigeration machine oil enclosed in order to lubricate the usage-side compressor62a. HFC-134a is a type of refrigerant having such saturation pressure characteristics. Water constituting the aqueous medium circulates in the aqueous medium circuit80a.

In the description related to the configurations below, the same reference numerals will be used and a description omitted for the configuration of the second usage unit10a, the hot-water storage unit8a, the hot-water air-warming unit9a, the liquid refrigerant communication tube13, the gas-refrigerant communication tube14, and the aqueous medium communication tubes15a,16a, all of which have the same configuration as those of heat pump system200in the second embodiment (seeFIG. 6). Only the configuration of the heat source unit2, the discharge refrigerant communication tube12, and the first usage unit4awill be described.

The heat source unit2is disposed outdoors, and is connected to the usage units4a,10avia the refrigerant communication tubes12,13,14and constitutes a portion of the heat-source-side refrigerant circuit20.

The heat source unit2has primarily a heat-source-side compressor21, an oil separation mechanism22, a heat-source-side switching mechanism23, a heat-source-side heat exchanger24, a heat-source-side expansion valve25, an intake return tube26, a subcooler27, a heat-source-side accumulator28, a liquid-side shutoff valve29, a gas-side shutoff valve30, and a discharge-side shutoff valve31.

The discharge-side shutoff valve31is a valve provided at the connection between the discharge refrigerant communication tube12and a heat-source-side discharge branch tube21dwhich is diverted from the heat-source-side discharge tube21b, which connects the heat-source-side switching mechanism23and the discharge of the heat-source-side compressor21.

The heat source unit2is the same as in the heat pump system200in the second embodiment (seeFIG. 6), except for the configuration related to the discharge-side shutoff valve31and the heat-source-side discharge branching tube21d, and the same reference numerals will be used and a description omitted.

The discharge refrigerant communication tube12is connected to the heat-source-side discharge branch tube21dvia the discharge-side shutoff valve31, and is a refrigerant tube capable of directing the heat-source-side refrigerant to the outside of the heat source unit2from the discharge of the heat-source-side compressor21in any of the heat-source-side radiating operation state and the heat-source-side evaporating operation state of the heat-source-side switching mechanism23.

The first usage unit4ais arranged indoors, is connected to the heat source unit2and the second usage unit10avia the refrigerant communication tubes12,13, and constitutes a portion of the heat-source-side refrigerant circuit20. The first usage unit4aconstitutes the usage-side refrigerant circuit40a. The first usage unit4ais connected to the hot-water storage unit8aand the hot-water air-warming unit9avia the aqueous medium communication tubes15a,16aand constitutes a portion of aqueous medium circuit80a.

The first usage unit4amainly has the first usage-side heat exchanger41a, the first usage-side flow rate adjustment valve42a, the usage-side compressor62a, the refrigerant/water heat exchanger65a, a refrigerant/water heat exchange-side flow rate adjustment valve66a, a usage-side accumulator67a, and a circulation pump43a.

A first usage-side discharge refrigerant tube46a, to which the discharge refrigerant communication tube12is connected, is connected to the first usage-side heat exchanger41aon the gas side of the channel through which the heat-source-side refrigerant flows in lieu of the first usage-side gas refrigerant tube54aconnected to the gas-refrigerant communication tube14as in the heat pump system200(seeFIG. 6) in the second embodiment. The first usage-side discharge refrigerant tube46ais provided with a first usage-side discharge non-return valve49afor allowing the heat-source-side refrigerant to flow toward the first usage-side heat exchanger41afrom the discharge refrigerant communication tube12and preventing the heat-source-side refrigerant from flowing toward the discharge refrigerant communication tube12from the first usage-side heat exchanger41a.

The usage unit4ais the same as in the heat pump system200(FIG. 6) in the second embodiment, except for the configuration related to the first usage-side discharge refrigerant tube46aconnected in place of the first usage-side gas refrigerant tube54a, and the same reference numerals will be used and a description omitted.

The heat pump system300is provided with a controller (not shown) for performing the operations and/or various types of control described below.

Next, the operation of the heat pump system300will be described.

The operation modes of the heat pump system300include a hot-water supply operation mode in which only the hot-water supply operation of the first usage unit4ais performed (i.e., operation of the hot-water storage unit8aand/or the hot-water air-warming unit9a), an air-cooling operation mode in which only air-cooling operation of the second usage unit10ais performed, an air-warming operation mode in which only air-warming operation of the second usage unit10ais performed, a hot-water supply/air-warming operation mode in which hot-water supply operation of the first usage unit4ais performed together with the air-warming operation of the second usage unit10a, and a hot-water supply/air-cooling operation mode for performing the hot-water supply operation of the first usage unit4aas well as the air-cooling operation of the second usage unit10a.

The operation in the five operating modes of the heat pump system300will next be described.

In the case of performing only the hot-water supply operation of the first usage unit4a, the heat-source-side switching mechanism23is switched to the heat-source-side evaporating operation state (indicated by broken line in the heat-source-side switching mechanism23inFIG. 12), and the intake return expansion valve26aand the second usage-side flow rate adjustment valve102aare closed in the heat-source-side refrigerant circuit20. In the aqueous medium circuit80a, the aqueous-medium-side switching mechanism161ais switched to the state of feeding the aqueous medium to the hot-water storage unit8aand/or the hot-water air-warming unit9a.

In the heat-source-side refrigerant circuit20in such a state, the low-pressure, heat-source-side refrigerant in the refrigeration cycle is taken into the heat-source-side compressor21by way of the heat-source-side intake tube21c, and is discharged to a heat-source-side discharge tube21bafter having been compressed to a high pressure in the refrigeration cycle. The high-pressure, heat-source-side refrigerant discharged to the heat-source-side discharge tube21bhas the refrigeration machine oil separated out in the oil separator22a. The refrigeration machine oil separated out from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cby way of the oil return tube22b. The high-pressure, heat-source-side refrigerant from which the refrigeration machine oil has been separated out is sent from the heat source unit2to the discharge refrigerant communication tube12by way of the heat-source-side discharge branching tube21dand a discharge-side shutoff valve31.

The high-pressure, heat-source-side refrigerant sent to the discharge refrigerant communication tube12is sent to the first usage unit4a. The high-pressure, heat-source-side refrigerant sent to the first usage unit4ais sent to the first usage-side heat exchanger41avia the first usage-side discharge refrigerant tube46aand the first usage-side discharge non-return valve49a. The high-pressure, heat-source-side refrigerant sent to the first usage-side heat exchanger41aundergoes heat exchange with the low-pressure, usage-side refrigerant in the refrigeration cycle that is circulating through the usage-side refrigerant circuit40aand releases heat in the first usage-side heat exchanger41a. The high-pressure, heat-source-side refrigerant having released heat in the first usage-side heat exchanger41ais sent from the first usage unit4ato the liquid refrigerant communication tube13via the first usage-side flow rate adjustment valve42aand the first usage-side liquid refrigerant tube45a.

The heat-source-side refrigerant sent to the liquid refrigerant communication tube13is sent to the heat source unit2. The heat-source-side refrigerant sent to the heat source unit2is sent to the subcooler27via a liquid-side shutoff valve29. The heat-source-side refrigerant sent to the subcooler27does not undergo heat exchange and is sent to the heat-source-side expansion valve25because the heat-source-side refrigerant does not flow in the intake return tube26. The heat-source-side refrigerant sent to the heat-source-side expansion valve25is depressurized in the heat-source-side expansion valve25to become a low-pressure gas-liquid two-phase state, and is then sent to the heat-source-side heat exchanger24by way of a heat-source-side liquid-refrigerant tube24a. The low-pressure refrigerant sent to the heat-source-side heat exchanger24undergoes heat exchange with outdoor air fed by the heat-source-side fan32and is evaporated in the heat-source-side heat exchanger24. The low-pressure, heat-source-side refrigerant evaporated in the heat-source-side heat exchanger24is sent to the heat-source-side accumulator28via the first heat-source-side gas-refrigerant tube23aand the heat-source-side switching mechanism23. The low-pressure, heat-source-side refrigerant sent to the heat-source-side accumulator28is again taken into the heat-source-side compressor21via the heat-source-side intake tube21c.

In the usage-side refrigerant circuit40a, the low-pressure, usage-side refrigerant in the refrigeration cycle that is circulating through the usage-side refrigerant circuit40ais heated and evaporated by the radiation of the heat-source-side refrigerant in the first usage-side heat exchanger41a. The low-pressure, usage-side refrigerant evaporated in the first usage-side heat exchanger41ais sent to the usage-side accumulator67avia the second cascade-side gas-refrigerant tube69a. The low-pressure, usage-side refrigerant sent to the usage-side accumulator67ais taken into the usage-side compressor62avia the cascade-side intake tube71a, is compressed to high pressure in the refrigeration cycle, and is thereafter discharged to the cascade-side discharge tube70a. The high-pressure, usage-side refrigerant discharged to the cascade-side discharge tube70ais sent to the refrigerant/water heat exchanger65avia the first cascade-side gas-refrigerant tube72a. The high-pressure, usage-side refrigerant sent to the refrigerant/water heat exchanger65aundergoes heat exchange with the aqueous medium being circulated through the aqueous medium circuit80aby the circulation pump43aand releases heat in the refrigerant/water heat exchanger65a. The high-pressure, usage-side refrigerant having released heat in the refrigerant/water heat exchanger65ais depressurized in the refrigerant/water heat exchange-side flow rate adjustment valve66ato become a low-pressure gas-liquid two-phase state, and is then sent again to the first usage-side heat exchanger41aby way of the cascade-side liquid-refrigerant tube68a.

In the aqueous medium circuit80a, the aqueous medium circulating through the aqueous medium circuit80ais heated by the radiation of the usage-side refrigerant in the refrigerant/water heat exchanger65a. The aqueous medium heated in the refrigerant/water heat exchanger65ais taken into the circulation pump43aby way of the first usage-side water outlet tube48aand pressurized, and is then sent from the first usage unit4ato the aqueous medium communication tube16a. The aqueous medium sent to the aqueous medium communication tube16ais sent to the hot-water storage unit8aand/or the hot-water air-warming unit9aby way of the aqueous-medium-side switching mechanism161a. The aqueous medium sent to the hot-water storage unit8aundergoes heat exchange with the aqueous medium inside the hot-water storage tank81aand releases heat in the heat exchange coil82a, whereby the aqueous medium inside the hot-water storage tank81ais heated. The aqueous medium sent to the hot-water air-warming unit9areleases heat in the heat exchange panel91a, whereby indoor walls or the like are heated and indoor floors are heated.

Operation in the hot-water supply operation mode for performing only hot-water supply operation of the first usage unit4ais performed in this manner.

In the case of performing only the air-cooling operation of the second usage unit10a, the heat-source-side switching mechanism23is switched to the heat-source-side radiating operation state (indicated by solid lines in the heat-source-side switching mechanism23inFIG. 12), and the first usage-side flow rate adjustment valve42ais closed in the heat-source-side refrigerant circuit20.

In the heat-source-side refrigerant circuit20in such a state, the low-pressure, heat-source-side refrigerant in the refrigeration cycle is taken into the heat-source-side compressor21via the heat-source-side intake tube21c, and is discharged to the heat-source-side discharge tube21bafter having been compressed to high pressure in the refrigeration cycle. The high-pressure, heat-source-side refrigerant discharged to the heat-source-side discharge tube21bhas the refrigeration machine oil separated out in the oil separator22a. The refrigeration machine oil separated out from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cby way of the oil return tube22b. The high-pressure, heat-source-side refrigerant from which the refrigeration machine oil has been separated out is sent to the heat-source-side heat exchanger24by way of the heat-source-side switching mechanism23and a first heat-source-side gas-refrigerant tube23a. The high-pressure, heat-source-side refrigerant sent to the heat-source-side heat exchanger24undergoes heat exchange with outdoor air fed by a heat-source-side fan32and releases heat in the heat-source-side heat exchanger24. The high-pressure, heat-source-side refrigerant having released heat in the heat-source-side heat exchanger is sent to the subcooler27via the heat-source-side expansion valve25. The heat-source-side refrigerant sent to the subcooler27undergoes heat exchange with the heat-source-side refrigerant branched from the heat-source-side liquid-refrigerant tube24ato the intake return tube26and is cooled to a subcooled state. The heat-source-side refrigerant that flows through the intake return tube26is returned to the heat-source-side intake tube21c. The heat-source-side refrigerant cooled in the subcooler27is sent from the heat source unit2to the liquid refrigerant communication tube13by way of the heat-source-side liquid-refrigerant tube24aand the liquid-side shutoff valve29.

The high-pressure, heat-source-side refrigerant sent to the liquid refrigerant communication tube13is sent to the second usage unit10a. The high-pressure, heat-source-side refrigerant sent to the second usage unit10ais sent to the second usage-side flow rate adjustment valve102a. The high-pressure, heat-source-side refrigerant sent to the second usage-side flow rate adjustment valve102ais depressurized in the second usage-side flow rate adjustment valve102ato become a low-pressure gas-liquid two-phase state, and is then sent to the second usage-side heat exchanger101aby way of the second usage-side liquid refrigerant tube103a. The low-pressure, heat-source-side refrigerant sent to the second usage-side heat exchanger101aundergoes heat exchange with an air medium fed by the usage-side fan105aand evaporates in the second usage-side heat exchanger101ato thereby perform indoor air cooling. The low-pressure, heat-source-side refrigerant thus evaporated in the second usage-side heat exchanger101ais sent from the second usage unit10ato the gas refrigerant communication tube14by way of the second usage-side gas refrigerant tube104a.

The low-pressure, heat-source-side refrigerant sent to the gas-refrigerant communication tube14is sent to the heat source unit2. The low-pressure, heat-source-side refrigerant sent to the heat source unit2is sent to the heat-source-side accumulator28by way of the gas-side shutoff valve30, the second heat-source-side gas refrigerant tube23b, and the heat-source-side switching mechanism23. The low-pressure, heat-source-side refrigerant sent to the heat-source-side accumulator28is again taken into the heat-source-side compressor21by way of the heat-source-side intake tube21c.

Operation in the air-cooling operation mode for performing only air-cooling operation of the second usage unit10ais performed in this manner.

In the case of performing only the air-warming operation of the second usage unit10a, the heat-source-side switching mechanism23is switched to the heat-source-side radiating operation state (indicated by broken lines in the heat-source-side switching mechanism23inFIG. 12), and the intake return expansion valve26aand the first usage-side flow rate adjustment valve42aare closed in the heat-source-side refrigerant circuit20.

In the heat-source-side refrigerant circuit20in such a state, low-pressure, heat-source-side refrigerant in the refrigeration cycle is taken into the heat-source-side compressor21via the heat-source-side intake tube21c, is compressed to a high pressure in the refrigeration cycle, and is thereafter discharged to the heat-source-side discharge tube21b.

The refrigeration machine oil of the high-pressure, heat-source-side refrigerant discharged to the heat-source-side discharge tube21bis separated out in the oil separator22a. The refrigeration machine oil separated out from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cby way of the oil return tube22b. The high-pressure, heat-source-side refrigerant from which the refrigeration machine oil has been separated out is sent from the heat source unit2to the gas-refrigerant communication tube14by way of the heat-source-side switching mechanism23, the second heat-source-side gas refrigerant tube23b, and the gas-side shutoff valve30.

The high-pressure, heat-source-side refrigerant sent to the gas-refrigerant communication tube14is sent to the second usage unit10a. The high-pressure, heat-source-side refrigerant sent to the second usage unit10ais sent to the second usage-side heat exchanger101aby way of the second usage-side gas refrigerant tube104a. The high-pressure, heat-source-side refrigerant sent to the second usage-side heat exchanger101aundergoes heat exchange with an air medium fed by the usage-side fan105aand releases heat in the second usage-side heat exchanger101ato thereby perform indoor air warming. The high-pressure, heat-source-side refrigerant thus having released heat in the second usage-side heat exchanger101ais sent from the second usage unit10ato the liquid refrigerant communication tube13by way of the second usage-side flow rate adjustment valve102aand the second usage-side liquid refrigerant tube103a.

The heat-source-side refrigerant sent to the liquid-refrigerant communication tube13is sent to the heat source unit2. The heat-source-side refrigerant sent to the heat source unit2is sent to the subcooler27by way of the liquid-side shutoff valve29. The heat-source-side refrigerant sent to the subcooler27is sent to the heat-source-side expansion valve25without undergoing heat exchange because the heat-source-side refrigerant does not flow in the intake return tube26. The heat-source-side refrigerant sent to the heat-source-side expansion valve25is depressurized in the heat-source-side expansion valve25to form a low-pressure, gas-liquid two-phase state, and is then sent to the heat-source-side heat exchanger24by way of the heat-source-side liquid-refrigerant tube24a. The low-pressure, heat-source-side refrigerant sent to the heat-source-side heat exchanger24undergoes heat exchange with outdoor air fed by the heat-source-side fan32and is evaporated in the heat-source-side heat exchanger24. The low-pressure, heat-source-side refrigerant evaporated in the heat-source-side heat exchanger24is sent to the heat-source-side accumulator28by way of the first heat-source-side gas-refrigerant tube23aand the heat-source-side switching mechanism23. The low-pressure, heat-source-side refrigerant sent to the heat-source-side accumulator28is again taken into the heat-source-side compressor21by way of the heat-source-side intake tube21c.

Operation in the air-warming operation mode for performing only air-warming operation of the second usage unit10ais performed in this manner.

In the case of performing the hot-water supply operation of the first usage unit4aas well as the air-warming operation of the second usage unit10a, the heat-source-side switching mechanism23is switched to the heat-source-side evaporating operation state (indicated by broken lines in the heat-source-side switching mechanism23inFIG. 12), and the intake return expansion valve26ais closed in the heat-source-side refrigerant circuit20. In the aqueous medium circuit80a, the aqueous-medium-side switching mechanism161ais switched to a state in which the aqueous medium is fed to the hot-water storage unit8aand/or the hot-water air-warming unit9a.

In the heat-source-side refrigerant circuit20in such a state, the low-pressure, heat-source-side refrigerant in the refrigeration cycle is taken into the heat-source-side compressor21by way of the heat-source-side intake tube21c, is compressed to high pressure in the refrigeration cycle, and is thereafter discharged to the heat-source-side discharge tube21b. The high-pressure, heat-source-side refrigerant discharged to the heat-source-side discharge tube21bhas the refrigeration machine oil separated out in the oil separator22a. The refrigeration machine oil separated out from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cby way of the oil return tube22b. A portion of the high-pressure, heat-source-side refrigerant from which the refrigeration machine oil has been separated out is sent from the heat source unit2to the discharge refrigerant communication tube12by way of the heat-source-side discharge branching tube21dand a discharge-side shutoff valve31, and the remainder is sent from the heat source unit2to the gas-refrigerant communication tube14by way of the heat-source-side switching mechanism23, the second heat-source-side gas refrigerant tube23band the gas-side shutoff valve30.

The high-pressure, heat-source-side refrigerant sent to the gas-refrigerant communication tube14is sent to the second usage unit10a. The high-pressure, heat-source-side refrigerant sent to the second usage unit10ais sent to the second usage-side heat exchanger101aby way of the second usage-side gas refrigerant tube104a. The high-pressure, heat-source-side refrigerant sent to the second usage-side heat exchanger101aundergoes heat exchange with the air medium fed by the usage-side fan105ato release heat in the second usage-side heat exchanger101aand thereby perform indoor air warming. The high-pressure, heat-source-side refrigerant having released heat in the second usage-side heat exchanger101ais sent from the second usage unit10ato the liquid refrigerant communication tube13by way of the second usage-side flow rate adjustment valve102aand the second usage-side liquid refrigerant tube103a.

The high-pressure, heat-source-side refrigerant sent to the discharge refrigerant communication tube12is sent to the first usage unit4a. The high-pressure, heat-source-side refrigerant sent to the first usage unit4ais sent to the first usage-side heat exchanger41aby way of the first usage-side discharge refrigerant tube46aand the first usage-side discharge non-return valve49a. The high-pressure, heat-source-side refrigerant sent to the first usage-side heat exchanger41aundergoes heat exchange with the low-pressure, usage-side refrigerant in the refrigeration cycle that is circulating through the usage-side refrigerant circuit40aand releases heat in the first usage-side heat exchanger41a. The high-pressure, heat-source-side refrigerant having released heat in the first usage-side heat exchanger41ais sent from the first usage unit4ato the liquid refrigerant communication tube13by way of the first usage-side flow rate adjustment valve42aand the first usage-side liquid refrigerant tube45a.

The heat-source-side refrigerant sent from the second usage unit10aand the first usage unit4ato the liquid refrigerant communication tube13merges in the liquid refrigerant communication tube13and is sent to the heat source unit2. The heat-source-side refrigerant sent to the heat source unit2is sent to the subcooler27by way of the liquid-side shutoff valve29. The heat-source-side refrigerant sent to the subcooler27is sent to the heat-source-side expansion valve25without undergoing heat exchange because the heat-source-side refrigerant does not flow in the intake return tube26. The heat-source-side refrigerant sent to the heat-source-side expansion valve25is depressurized in the heat-source-side expansion valve25to become a low-pressure gas-liquid two-phase state, and is then sent to the heat-source-side heat exchanger24by way of the heat-source-side liquid-refrigerant tube24a. The low-pressure refrigerant sent to the heat-source-side heat exchanger24undergoes heat exchange with outdoor air fed by the heat-source-side fan32and evaporates in the heat-source-side heat exchanger24. The low-pressure, heat-source-side refrigerant evaporated in the heat-source-side heat exchanger24is sent to the heat-source-side accumulator28by way of the first heat-source-side gas-refrigerant tube23aand the heat-source-side switching mechanism23. The low-pressure, heat-source-side refrigerant sent to the heat-source-side accumulator28is again taken into the heat-source-side compressor21by way of the heat-source-side intake tube21c.

In the usage-side refrigerant circuit40a, the low-pressure, usage-side refrigerant in the refrigeration cycle that is circulating through the usage-side refrigerant circuit40ais heated and evaporated by the radiation of the heat-source-side refrigerant in the first usage-side heat exchanger41a. The low-pressure, usage-side refrigerant evaporated in the first usage-side heat exchanger41ais sent to the usage-side accumulator67avia the second cascade-side gas-refrigerant tube69a. The low-pressure, usage-side refrigerant sent to the usage-side accumulator67ais taken into the usage-side compressor62aby way of the cascade-side intake tube71a, is compressed to high pressure in the refrigeration cycle, and is thereafter discharged to the cascade-side discharge tube70a. The high-pressure, usage-side refrigerant discharged to the cascade-side discharge tube70ais sent to the refrigerant/water heat exchanger65aby way of the first cascade-side gas-refrigerant tube72a. The high-pressure, usage-side refrigerant sent to the refrigerant/water heat exchanger65aundergoes heat exchange with the aqueous medium being circulated through the aqueous medium circuit80aby the circulation pump43aand releases heat in the refrigerant/water heat exchanger65a. The high-pressure, usage-side refrigerant having released heat in the refrigerant/water heat exchanger65ais depressurized in the refrigerant/water heat exchange-side flow rate adjustment valve66ato become a low-pressure gas-liquid two-phase state, and is then sent again to the first usage-side heat exchanger41aby way of the cascade-side liquid-refrigerant tube68a.

In the aqueous medium circuit80a, the aqueous medium circulating through the aqueous medium circuit80ais heated by the radiation of the usage-side refrigerant in the refrigerant/water heat exchanger65a. The aqueous medium heated in the refrigerant/water heat exchanger65ais taken into the circulation pump43aby way of the first usage-side water outlet tube48aand pressurized, and is then sent from the first usage unit4ato the aqueous medium communication tube16a. The aqueous medium sent to the aqueous medium communication tube16ais sent to the hot-water storage unit8aand/or the hot-water air-warming unit9aby way of the aqueous-medium-side switching mechanism161a. The aqueous medium sent to the hot-water storage unit8aundergoes heat exchange with the aqueous medium inside the hot-water storage tank81aand releases heat in the heat exchange coil82a, whereby the aqueous medium inside the hot-water storage tank81ais heated. The aqueous medium sent to the hot-water air-warming unit9areleases heat in the heat exchange panel91a, whereby indoor walls or the like are heated and indoor floors are heated.

Operation in the hot-water supply/air-warming operation mode for performing hot-water supply operation of the first usage unit4aand air-warming operation of the second usage unit10aare performed in this manner.

In the case of performing the hot-water supply operation of the first usage unit4aas well as the air-cooling operation of the second usage unit10a, the heat-source-side switching mechanism23is switched to the heat-source-side radiating operation state (indicated by solid lines in the heat-source-side switching mechanism23inFIG. 12) in the heat-source-side refrigerant circuit20. In the aqueous medium circuit80a, the aqueous-medium-side switching mechanism161ais switched to a state in which the aqueous medium is fed to the hot-water storage unit8a.

In the heat-source-side refrigerant circuit20in such a state, the low-pressure, heat-source-side refrigerant in the refrigeration cycle is taken into the heat-source-side compressor21by way of the heat-source-side intake tube21c, is compressed to high pressure in the refrigeration cycle, and is thereafter discharged to the heat-source-side discharge tube21b. The high-pressure, heat-source-side refrigerant discharged to the heat-source-side discharge tube21bhas the refrigeration machine oil separated out in the oil separator22a. The refrigeration machine oil separated out from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cby way of the oil return tube22b. A portion of the high-pressure, heat-source-side refrigerant from which the refrigeration machine oil has been separated out is sent from the heat source unit2to the discharge refrigerant communication tube12by way of the heat-source-side discharge branching tube21dand a discharge-side shutoff valve31, and the remainder is sent to the heat-source-side heat exchanger24by way of the heat-source-side switching mechanism23and the first heat-source-side gas-refrigerant tube23a. The high-pressure, heat-source-side refrigerant sent to the heat-source-side heat exchanger24undergoes heat exchange with outdoor air fed by the heat-source-side fan32and releases heat in the heat-source-side heat exchanger24. The high-pressure, heat-source-side refrigerant having released heat in the heat-source-side heat exchanger is sent to the subcooler27by way of the heat-source-side expansion valve25. The heat-source-side refrigerant sent to the subcooler27undergoes heat exchange with the heat-source-side refrigerant branched from the heat-source-side liquid-refrigerant tube24ato the intake return tube26and is cooled to a subcooled state. The heat-source-side refrigerant that flows through the intake return tube26is returned to the heat-source-side intake tube21c. The heat-source-side refrigerant cooled in the subcooler27is sent from the heat source unit2to the liquid refrigerant communication tube13by way of the heat-source-side liquid-refrigerant tube24aand the liquid-side shutoff valve29.

The high-pressure, heat-source-side refrigerant sent to the discharge refrigerant communication tube12is sent to the first usage unit4a. The high-pressure, heat-source-side refrigerant sent to the first usage unit4ais sent to the first usage-side heat exchanger41aby way of the first usage-side discharge refrigerant tube46aand the first usage-side discharge non-return valve49a. The high-pressure, heat-source-side refrigerant sent to the first usage-side heat exchanger41aundergoes heat exchange with the low-pressure, usage-side refrigerant in the refrigeration cycle that circulates through the usage-side refrigerant circuit40aand releases heat in the first usage-side heat exchanger41a. The high-pressure, heat-source-side refrigerant having released heat in the first usage-side heat exchanger41ais sent from the first usage unit4ato the liquid refrigerant communication tube13by way of the first usage-side flow rate adjustment valve42aand the first usage-side liquid refrigerant tube45a.

The heat-source-side refrigerant sent from the heat source unit2and the first usage unit4ato the liquid refrigerant communication tube13merges in the liquid refrigerant communication tube13and is sent to the second usage unit10a. The heat-source-side refrigerant sent to the second usage unit10ais sent to the second usage-side flow rate adjustment valve102a. The heat-source-side refrigerant sent to the second usage-side flow rate adjustment valve102ais depressurized in the second usage-side flow rate adjustment valve102ato become a low-pressure gas-liquid two-phase state, and is then sent to the second usage-side heat exchanger101aby way of the second usage-side liquid refrigerant tube103a. The low-pressure heat-source-side refrigerant sent to the second usage-side heat exchanger101aundergoes heat exchange with the air medium fed by the usage-side fan105aand evaporates in the second usage-side heat exchanger101ato thereby perform indoor air cooling. The low-pressure, heat-source-side refrigerant evaporated in the second usage-side heat exchanger101ais sent from the second usage unit10ato the gas-refrigerant communication tube14by way of the second usage-side gas refrigerant tube104a.

The low-pressure, heat-source-side refrigerant sent to the gas-refrigerant communication tube14is sent to the heat source unit2. The low-pressure, heat-source-side refrigerant sent to the heat source unit2is sent to the heat-source-side accumulator28by way of the gas-side shutoff valve30, the second heat-source-side gas refrigerant tube23b, and the heat-source-side switching mechanism23. The low-pressure, heat-source-side refrigerant sent to the heat-source-side accumulator28is again taken into the heat-source-side compressor21by way of the heat-source-side intake tube21c.

In the usage-side refrigerant circuit40a, the low-pressure, usage-side refrigerant in the refrigeration cycle that is circulating through the usage-side refrigerant circuit40ais heated and evaporated by the radiation of the heat-source-side refrigerant in the first usage-side heat exchanger41a. The low-pressure, usage-side refrigerant evaporated in the first usage-side heat exchanger41ais sent to the usage-side accumulator67aby way of the second cascade-side gas-refrigerant tube69a. The low-pressure, usage-side refrigerant sent to the usage-side accumulator67ais taken into the usage-side compressor62aby way of the cascade-side intake tube71a, is compressed to high pressure in the refrigeration cycle, and is thereafter discharged to the cascade-side discharge tube70a. The high-pressure, usage-side refrigerant discharged to the cascade-side discharge tube70ais sent to the refrigerant/water heat exchanger65aby way of the first cascade-side gas-refrigerant tube72a. The high-pressure, usage-side refrigerant sent to the refrigerant/water heat exchanger65aundergoes heat exchange with the aqueous medium being circulated through the aqueous medium circuit80aby the circulation pump43aand releases heat in the refrigerant/water heat exchanger65a. The high-pressure, usage-side refrigerant having released heat in the refrigerant/water heat exchanger65ais depressurized in the refrigerant/water heat exchange-side flow rate adjustment valve66ato become a low-pressure gas-liquid two-phase state, and is then sent again to the first usage-side heat exchanger41aby way of the cascade-side liquid-refrigerant tube68a.

In the aqueous medium circuit80a, the aqueous medium circulating through the aqueous medium circuit80ais heated by the radiation of the usage-side refrigerant in the refrigerant/water heat exchanger65a. The aqueous medium heated in the refrigerant/water heat exchanger65ais taken into the circulation pump43aby way of the first usage-side water outlet tube48aand pressurized, and is then sent from the first usage unit4ato the aqueous medium communication tube16a. The aqueous medium sent to the aqueous medium communication tube16ais sent to the hot-water storage unit8aby way of the aqueous-medium-side switching mechanism161a. The aqueous medium sent to the hot-water storage unit8aundergoes heat exchange with the aqueous medium inside the hot-water storage tank81aand releases heat in the heat exchange coil82a, whereby the aqueous medium inside the hot-water storage tank81ais heated.

Operation in the hot-water supply/air-cooling operation mode for performing hot-water supply operation of the first usage unit4aand air-cooling operation of the second usage unit10aare performed in this manner.

In the configuration of the heat pump system300, in which the first usage unit4afor the hot-water-supply operation and the second usage unit10afor the air-cooling and air-warming operations are connected to the heat source unit2so as to enable the hot-water-supply/air-cooling operation, discharge saturation temperature control of the refrigerant circuits20,40aand subcooling degree control of the outlets of the heat exchangers41a,65aare performed, similar to the heat pump system200in the second embodiment (seeFIG. 6).

It is thereby possible in this heat pump system300, not only to obtain the same operational effects as the heat pump system200in the second embodiment, but also to perform an operation of heating the aqueous medium by the first usage-side heat exchanger41aand the usage-side refrigerant circuit40aand to use the heat of cooling of the heat-source-side refrigerant resulting from heating the aqueous medium in an operation of cooling the air medium by evaporation of the heat-source-side refrigerant in the second usage-side heat exchanger101a. Therefore, the heat of cooling of the heat-source-side refrigerant resulting from heating the aqueous medium can be effectively used, such as in using the aqueous medium heated by the first usage-side heat exchanger41aand the usage-side refrigerant circuit40afor a hot water supply and using the air medium cooled in the second usage-side heat exchanger101afor air-cooling of the room interior, for example, and energy can thereby be conserved.

Even in a configuration such as that of the above-described heat pump system300(seeFIG. 12), wherein the first usage unit4afor the hot-water-supply operation and the second usage unit10afor the air-cooling and air-warming operations are connected to the heat source unit2so as to enable the hot-water-supply/air-cooling operation, since an oil separation mechanism is not provided to the discharge of the usage-side compressor62a, refrigeration machine oil is readily led with the usage-side refrigerant into the refrigerant-water heat exchanger65afunctioning as a radiator of the usage-side refrigerant, and under high-temperature conditions, biphasic separation of the liquid usage-side refrigerant and the refrigeration machine oil occurs readily in the refrigerant-water heat exchanger65a, and refrigeration machine oil therefore readily backs up within the refrigerant-water heat exchanger65afunctioning as a radiator of the usage-side refrigerant, similar to the heat pump system200(seeFIG. 6) in Modification 1 of the second embodiment. When subcooling degree control of the outlet of the refrigerant-water heat exchanger65ais performed, the liquid usage-side refrigerant accumulates in the refrigerant-water heat exchanger65ain an amount corresponding to the usage-side refrigerant degree of subcooling SC2, therefore making biphasic separation of the liquid usage-side refrigerant and the refrigeration machine oil occur even more readily.

In view of this, the same oil recovery operation control (seeFIG. 2) as in the heat pump system200in the second embodiment (seeFIG. 6) is performed in this heat pump system300as well.

It is thereby possible to ensure that there will be no insufficiency of refrigeration machine oil in the usage-side compressor62a. During the oil recovery operation, the operation of making the refrigerant-water heat exchanger65afunction as a radiator of usage-side refrigerant and heating the aqueous medium can be continued, and the adverse effect that the oil recovery operation has on the hot-water-supply operation, the hot-water-supply/air-warming operation, and the hot-water-supply/air-cooling operation can thereby be reduced as much as possible.

In the heat pump system300(seeFIG. 12) described above, as shown inFIG. 13, it is possible to furthermore provide the usage-side refrigerant circuit40awith a first usage-side switching mechanism64a(the same as the first usage-side switching mechanism64aprovided to the heat pump system200in the second embodiment) capable of switching between a usage-side radiating operation state in which the refrigerant/water heat exchanger65ais made to function as a radiator of the usage-side refrigerant and the first usage-side heat exchanger41ais made to function as an evaporator of the usage-side refrigerant, and a usage-side evaporating operation state in which the refrigerant/water heat exchanger65ais made to function as an evaporator of the usage-side refrigerant and the first usage-side heat exchanger41ais made to function as a radiator of the usage-side refrigerant; and it is possible to further connect the first usage unit4ato the gas-refrigerant communication tube14and to further provide a second usage-side switching mechanism53acapable of switching between an aqueous medium-heating operation state in which the first usage-side heat exchanger41ais made to function as a radiator of the heat-source-side refrigerant introduced from the discharge refrigerant communication tube12, and an aqueous medium-cooling operation state in which the first usage-side heat exchanger41ais made to function as an evaporator of the heat-source-side refrigerant introduced from the liquid refrigerant communication tube13.

Here, the first usage-side gas refrigerant tube54ais connected together with the first usage-side discharge refrigerant tube46ato the gas side of the channel through which the heat-source-side refrigerant of the first usage-side heat exchanger41aflows. The gas-refrigerant communication tube14is connected to the first usage-side gas refrigerant tube54a. The second usage-side switching mechanism53ahas a first usage-side discharge on-off valve55a(in this case, the first usage-side discharge non-return valve49ais omitted) provided to the first usage-side discharge refrigerant tube46a, and a first usage-side gas on-off valve56aprovided to the first usage-side gas refrigerant tube54a; and is used for setting an aqueous medium-heating operation state by opening the first usage-side discharge on-off valve55aand closing the first usage-side gas on-off valve56a, and setting an aqueous medium-cooling operation state by closing the first usage-side discharge on-off valve55aand opening the first usage-side gas on-off valve56a. The first usage-side discharge on-off valve55aand the first usage-side gas on-off valve56aare composed of solenoid valves, both being capable of on-off control. The second usage-side switching mechanism53amay be configured using a three-way valve or the like.

With the heat pump system300having such a configuration, in the case that defrosting of the heat-source-side heat exchanger24has been determined to be required, depending on operation in the hot-water supply operation mode, the air-warming operation mode, and the hot-water supply/air-warming operation mode, it is possible to perform a defrosting operation in which the heat-source-side heat exchanger24is made to function as a radiator of the heat-source-side refrigerant by setting the heat-source-side switching mechanism23in a heat-source-side radiating operation state; the second usage-side heat exchanger101ais made to function as an evaporator of the heat-source-side refrigerant and the refrigerant/water heat exchanger65ais made to function as an evaporator of the usage-side refrigerant by setting the first usage-side switching mechanism64ain a usage-side evaporating operation state; and the first usage-side heat exchanger41ais made to function as a radiator of the usage-side refrigerant.

Operation in the defrosting operation is described below with reference toFIG. 4.

First, it is determined whether predetermined defrosting operation start conditions have been satisfied (i.e., whether defrosting of the heat-source-side heat exchanger24is required) (step S11). Here, it is determined whether the defrosting operation start conditions have been satisfied on the basis of whether the defrosting time interval Δtdf (i.e., the cumulative operation time from the end of the previous defrosting operation) has reached the predetermined defrosting time interval setting value Δtdfs.

The process starts the defrosting operation below in the case that it has been determined that the defrosting operation start conditions have been satisfied (step S12).

When the defrosting operation is started, a switch is made in the heat-source-side refrigerant circuit20to switch the heat-source-side switching mechanism23to the heat-source-side radiating operation state (the state indicated by the solid lines of heat-source-side switching mechanism23ofFIG. 14), a switch is made in the usage-side refrigerant circuit40ato switch the first usage-side switching mechanism64ato the usage-side evaporating operation state (the state indicated by the broken lines of first usage-side switching mechanism64ainFIG. 14), the second usage-side switching mechanism53ais switched to the aqueous medium-cooling operation state (i.e., the state in which the first usage-side discharge on-off value55ais closed and the first usage-side gas on-off valve56ais open), and the intake-return expansion valve26ais set in a closed state.

In the heat-source-side refrigerant circuit20in such a state, the low-pressure heat-source-side refrigerant in the refrigeration cycle is taken into the heat-source-side compressor21by way of the heat-source-side intake tube21c, compressed to high pressure in the refrigeration cycle, and thereafter discharged to the heat-source-side discharge tube21b. The high-pressure heat-source-side refrigerant discharged to the heat-source-side discharge tube21bhas the refrigeration machine oil separated out in the oil separator22a. The refrigeration machine oil separated out from the heat-source-side refrigerant in the oil separator22ais returned to the heat-source-side intake tube21cby way of the oil return tube22b. The high-pressure, heat-source-side refrigerant from which the refrigeration machine oil has been separated out is sent to the heat-source-side heat exchanger24by way of the heat-source-side switching mechanism23and the first heat-source-side gas-refrigerant tube23a. The high-pressure, heat-source-side refrigerant sent to the heat-source-side heat exchanger24undergoes heat exchange with ice deposited in the heat-source-side heat exchanger24and heat is released in the heat-source-side heat exchanger24. The high-pressure, heat-source-side refrigerant having released heat in the heat-source-side heat exchanger is sent to the subcooler27by way of the heat-source-side expansion valve25. The heat-source-side refrigerant sent to the subcooler27is sent from the heat source unit2to the liquid refrigerant communication tube13by way of the heat-source-side liquid-refrigerant tube24aand the liquid-side shutoff valve29without undergoing heat exchange because the heat-source-side refrigerant does not flow in the intake return tube26.

The heat-source-side refrigerant sent to the liquid refrigerant communication tube13branches in the liquid refrigerant communication tube13and is sent to the first usage unit4aand the second usage unit10a.

The heat-source-side refrigerant sent to the second usage unit10ais sent to the second usage-side flow rate adjustment valve102a. The heat-source-side refrigerant sent to the second usage-side flow rate adjustment valve102ais depressurized in the second usage-side flow rate adjustment valve102ato become a low-pressure gas-liquid two-phase state, and is then sent to the second usage-side heat exchanger101aby way of the second usage-side liquid refrigerant tube103a. The low-pressure, heat-source-side refrigerant sent to the second usage-side heat exchanger101aundergoes heat exchange with an air medium fed by the usage-side fan105aand evaporates in the second usage-side heat exchanger101a. The low-pressure, heat-source-side refrigerant thus evaporated in the second usage-side heat exchanger101ais sent from the second usage unit10ato the gas refrigerant communication tube14by way of the second usage-side gas refrigerant tube104a.

The heat-source-side refrigerant sent to the first usage unit4ais sent to the first usage-side flow rate adjustment valve42a. The heat-source-side refrigerant sent to the first usage-side flow rate adjustment valve42ais depressurized in the first usage-side flow rate adjustment valve42ato become a low-pressure gas-liquid two-phase state, and is then sent to the first usage-side heat exchanger41aby way of the first usage-side liquid refrigerant tube45a. The low-pressure, heat-source-side refrigerant sent to the first usage-side heat exchanger41aundergoes heat exchange with the high-pressure usage-side refrigerant in the refrigeration cycle that is circulated through the usage-side refrigerant circuit40aand evaporates in the first usage-side heat exchanger41a. The low-pressure, heat-source-side refrigerant thus evaporated in the first usage-side heat exchanger41ais sent from the first usage unit4ato the gas refrigerant communication tube14by way of the first usage-side gas refrigerant tube54aand the first usage-side gas on-off valve56aconstituting the first usage-side switching mechanism53a.

The heat-source-side refrigerant sent from the second usage unit10aand the first usage unit4ato the gas refrigerant communication tube14merges in the gas refrigerant communication tube14and is sent to the heat source unit2. The low-pressure, heat-source-side refrigerant sent to the heat source unit2is sent to the heat-source-side accumulator28by way of the gas-side shutoff valve30, the second heat-source-side gas refrigerant tube23b, and the heat-source-side switching mechanism23. The low-pressure, heat-source-side refrigerant sent to the heat-source-side accumulator28is again taken into the heat-source-side compressor21by way of the heat-source-side intake tube21c.

The high-pressure, usage-side refrigerant in the refrigeration cycle that circulates through the usage-side refrigerant circuit40areleases heat in the usage-side refrigerant circuit40aby the evaporation of the heat-source-side refrigerant in the first usage-side heat exchanger41a. The high-pressure, usage-side refrigerant having released heat in the first usage-side heat exchanger41ais sent to the refrigerant/water heat exchange-side flow rate adjustment valve66a. The high-pressure, usage-side refrigerant sent to the refrigerant/water heat exchange-side flow rate adjustment valve66ais depressurized in the refrigerant/water heat exchange-side flow rate adjustment valve66ato become a low-pressure gas-liquid two-phase state, and is then sent to the refrigerant/water heat exchanger65aby way of the cascade-side liquid-refrigerant tube68a. The low-pressure, usage-side refrigerant sent to the refrigerant/water heat exchanger65aundergoes heat exchange with the aqueous medium circulated through the aqueous medium circuit80aby the circulation pump43aand evaporates in the refrigerant/water heat exchanger65a. The low-pressure, usage-side refrigerant thus evaporated in the refrigerant/water heat exchanger65ais sent to the usage-side accumulator67aby way of the first cascade-side gas-refrigerant tube72aand the second usage-side switching mechanism64a. The low-pressure, usage-side refrigerant sent to the usage-side accumulator67ais taken into the usage-side compressor62aby way of the cascade-side intake tube71a, compressed to high pressure in the refrigeration cycle, and thereafter discharged to the cascade-side discharge tube70a. The high-pressure, usage-side refrigerant discharged to the cascade-side discharge tube70ais again sent to the first usage-side heat exchanger41aby way of the second usage-side switching mechanism64aand the second cascade-side gas-refrigerant tube69a.

In this manner, the defrosting operation is started in which the heat-source-side heat exchanger24is made to function as a radiator of the heat-source-side refrigerant by setting the heat-source-side switching mechanism23in the heat-source-side heat-release operation state; the second usage-side heat exchanger101ais made to function as an evaporator of the heat-source-side refrigerant and the refrigerant/water heat exchanger65ais made to function as an evaporator of the usage-side refrigerant by setting the second usage-side switching mechanism64ain a usage-side evaporating operation state; and the first usage-side heat exchanger41ais made to function as a radiator of the usage-side refrigerant (i.e., as an evaporator of the heat-source-side refrigerant).

It is determined whether predetermined defrosting operation end conditions have been satisfied (i.e., whether defrosting of the heat-source-side heat exchanger24has ended; step S13). Here, it is determined whether the defrosting operation end conditions have been satisfied depending on whether the heat-source-side heat exchanger temperature Thx has reached the predetermined defrosting completion temperature Thxs, or whether the defrosting operation time tdf, which is the time elapsed from the start of the defrosting operation, has reached a predetermined defrosting operation setting time tdfs.

In the case that it has been determined that the defrosting operation end conditions have been satisfied, the defrosting operation is ended and the process returns to the hot-water supply operation mode, the air-warming operation mode, and/or the hot-water supply/air-warming operation mode (step S14).

With the heat pump system300, when the heat-source-side heat exchanger24is to be defrosted, not only is the heat-source-side switching mechanism23set in the heat-source-side radiating operation state to thereby cause the heat-source-side heat exchanger24to function as a radiator of the heat-source-side refrigerant, but also the first usage-side switching mechanism64ais set in the usage-side evaporating operation state to thereby cause the refrigerant/water heat exchanger65ato function as an evaporator of the usage-side refrigerant and cause the first usage-side heat exchanger41ato function as a radiator of the usage-side refrigerant. Therefore, the heat-source-side refrigerant cooled by releasing heat in the heat-source-side heat exchanger24is heated by the heat released by the usage-side refrigerant in the first usage-side heat exchanger41a, and the usage-side refrigerant cooled by releasing heat in the first usage-side heat exchanger41acan be heated by evaporation in the refrigerant/water heat exchanger65a, whereby the defrosting of the heat-source-side heat exchanger24can be reliably performed. Also, since the second usage-side heat exchanger101ais also made to function as an evaporator of the heat-source-side refrigerant, the defrosting operation time tdf can be reduced and it is possible to inhibit a reduction in the temperature of the air medium cooled in the second usage unit10a.

In the heat pump system300having such a configuration, when the oil recovery operation becomes necessary in the hot-water-supply operation mode, the hot-water-supply/air-warming operation mode, or the hot-water-supply/air-cooling operation mode, the oil recovery operation of Modification 2 of the second embodiment can be performed while the first usage-side switching mechanism64ais kept in the usage-side radiating operation state (i.e., is not switched).

A configuration such as that of the heat pump system300(seeFIG. 13) in Modification 2 is provided with the second usage-side switching mechanism53a, which is capable of switching between an aqueous medium-heating operation state in which the first usage-side heat exchanger41ais made to function as a radiator of the heat-source-side refrigerant introduced from the discharge refrigerant communication tube12and an aqueous medium-cooling operation state in which the first usage-side heat exchanger41ais made to function as an evaporator of the heat-source-side refrigerant introduced from the liquid refrigerant communication tube13. In such a configuration, the heat-source-side refrigerant discharged from the heat-source-side compressor21stagnates in the discharge refrigerant communication tube12and the flow rate of the heat-source-side refrigerant taken into the heat-source-side compressor21is liable to be insufficient (i.e., an insufficient refrigerant-circulation rate) in the case that operation of the first usage unit4ais stopped and the second usage unit10a(air-cooling operation or air-warming operation) is operated (the case in which the discharge refrigerant communication tube12is not used).

In view of the above, the heat pump system300is provided with a first refrigerant recovery mechanism57afor placing the discharge refrigerant communication tube12and the gas refrigerant communication tube14in communication when the second usage-side switching mechanism53ais in the aqueous medium-heating operation state or the aqueous medium-cooling operation state, as shown inFIG. 14. Here, the first refrigerant recovery mechanism57ais a refrigerant tube having a capillary tube in which one end is connected to the portion of the first usage-side discharge refrigerant tube46athat connects the first usage-side discharge on-off valve55aand the discharge refrigerant communication tube12, and the other end is connected to the portion of the first usage-side gas refrigerant tube54athat connects the first usage-side gas on-off valve56aand the gas refrigerant communication tube14; and the discharge refrigerant communication tube12and the gas refrigerant communication tube14are in communication regardless of the on-off state of the first usage-side discharge on-off valve55aand/or the first usage-side gas on-off valve56a.

In the heat pump system300, the heat-source-side refrigerant is thereby made less likely to stagnate in the discharge refrigerant communication tube12, and it is therefore possible to minimize the occurrence of an insufficient refrigerant-circulation rate in the heat-source-side refrigerant circuit20.

A configuration such as that of the heat pump system300(seeFIG. 13) in Modification 2 is provided with the second usage-side switching mechanism53a, which is capable of switching between an aqueous medium-heating operation state in which the first usage-side heat exchanger41ais made to function as a radiator of the heat-source-side refrigerant introduced from the discharge refrigerant communication tube12and an aqueous medium-cooling operation state in which the first usage-side heat exchanger41ais made to function as an evaporator of the heat-source-side refrigerant introduced from the liquid refrigerant communication tube13. In such a configuration, the heat-source-side refrigerant stagnates in the first usage-side heat exchanger41aand the flow rate of the heat-source-side refrigerant taken into the heat-source-side compressor21is liable to be insufficient (i.e., an insufficient refrigerant-circulation rate) in the case that operation of the first usage unit4ais stopped and the second usage unit10a(air-cooling operation or air-warming operation) is operated.

In view of the above, in this heat pump system300, there is provided a second refrigerant recovery mechanism58afor placing the first usage-side heat exchanger41aand the gas refrigerant communication tube14in communication when the second usage-side switching mechanism53ais in an aqueous medium-heating operation state or in an aqueous medium-cooling operation state, as shown inFIG. 14. Here, the second refrigerant recovery mechanism58ahas a refrigerant tube having a capillary tube in which one end is connected to the portion of the first usage-side gas refrigerant tube54athat connects the gas side of the first usage-side heat exchanger41aand the first usage-side gas on-off valve56a, and the other end is connected to the portion of the first usage-side gas refrigerant tube54athat connects the first usage-side gas on-off valve56aand the gas refrigerant communication tube14; and the first usage-side gas on-off valve56ais bypassed to place the gas side of the first usage-side heat exchanger41aand the gas refrigerant communication tube14in communication even in the case that the operation of the first usage unit4ais stopped.

In this heat pump system300, the heat-source-side refrigerant is thereby made less likely to stagnate in the first usage-side heat exchanger41a, and it is therefore possible to minimize the occurrence of an insufficient refrigerant-circulation rate in the heat-source-side refrigerant circuit20.

Furthermore, in the heat pump system300(seeFIG. 13) in the modifications, the second usage-side switching mechanism53ais composed of the first usage-side discharge on-off valve55aand the first usage-side gas on-off valve56a, and the heat-source-side refrigerant is therefore fed from only the discharge refrigerant communication tube12to the first usage unit4ain any operation mode that accompanies a hot-water supply operation.

However, the heat-source-side refrigerant is at the high pressure of the refrigeration cycle not only in the discharge refrigerant communication tube12, but also in the gas refrigerant communication tube14in the hot-water supply operation mode and/or the hot-water supply/air-warming operation mode among the operation modes that accompany hot-water supply operation. Therefore, it is also possible to allow high-pressure, heat-source-side refrigerant to be sent from not only the discharge refrigerant communication tube12, but also from the gas refrigerant communication tube14to the first usage unit4ain the hot-water supply operation mode and/or the hot-water supply/air-warming operation mode.

In view of the above, in this heat pump system300, a first usage-side gas non-return valve59aand a first usage-side bypass refrigerant tube60aare furthermore provided to the first usage-side gas refrigerant tube54a; and, together with the first usage-side discharge on-off valve55aand the first usage-side gas on-off valve56a, constitute the second usage-side switching mechanism53a, as shown inFIG. 14. Here, the first usage-side gas non-return valve59ais provided to the portion of the first usage-side gas refrigerant tube54athat connects the first usage-side gas on-off valve56aand the gas refrigerant communication tube14. The first usage-side gas non-return valve59ais a non-return valve that allows the flow of heat-source-side refrigerant from the first usage-side heat exchanger41atoward the gas refrigerant communication tube14, and prohibits the flow of the heat-source-side refrigerant from the gas refrigerant communication tube14toward the first usage-side heat exchanger41a; and the flow of heat-source-side refrigerant from the gas refrigerant communication tube14toward the first usage-side heat exchanger41avia the first usage-side gas on-off valve56ais thereby prohibited. The first usage-side bypass refrigerant tube60ais connected to the first usage-side gas refrigerant tube54aso as to bypass the first usage-side gas on-off valve56aand the first usage-side gas non-return valve59a, and constitutes a portion of the first usage-side gas refrigerant tube54a. The first usage-side bypass refrigerant tube60ais provided with a first usage-side bypass non-return valve61afor allowing the flow of heat-source-side refrigerant from the gas refrigerant communication tube14to the first usage-side heat exchanger41aand prohibiting the flow of heat-source-side refrigerant from the first usage-side heat exchanger41ato the gas refrigerant communication tube14, whereby the flow of heat-source-side refrigerant from the gas refrigerant communication tube14to the first usage-side heat exchanger41ais allowed via the first usage-side bypass refrigerant tube60a.

In this heat pump system300, high-pressure, heat-source-side refrigerant can thereby be sent from not only the discharge refrigerant communication tube12, but also from the gas refrigerant communication tube14to the first usage unit4ain the hot-water supply operation mode and the hot-water supply/air-warming operation mode. Therefore, the loss of pressure of the heat-source-side refrigerant fed from the heat source unit2to the first usage unit4ais reduced, which can contribute to an improvement in the hot-water supply capacity and/or operation efficiency.

In the heat pump systems300described above (seeFIGS. 12 to 14), a single first usage unit4aand a single second usage unit10aare connected to the heat source unit2via the refrigerant communication tubes12,13,14, but a plurality of first usage units4a,4b(two, in this case) may be connected in parallel to each other via the refrigerant communication tubes13,14, and/or a plurality of second usage units10a,10b(two, in this case) may be connected in parallel to each other via the refrigerant communication tubes12,13,14, as shown inFIGS. 15 to 17(in this case, the hot-water/air-warming unit, the hot-water storage unit, the aqueous medium circuits80a,80b, and the like are not shown). The configuration of the first usage unit4bis the same as the configuration of the first usage unit4awith the subscript “b” used in place of the subscript “a” of the reference numerals indicating each part of the first usage unit4a, and a description of each part of the first usage unit4bis therefore omitted. Also, the configuration of the second usage unit10bis the same as the configuration of the second usage unit10awith the subscript “b” used in place of the subscript “a” of the reference numerals indicating each part of the second usage unit10b, and a description of each part is therefore omitted.

In these heat pump systems300, it is possible to accommodate a plurality of locations and/or applications that require heating of the aqueous medium, and it is possible to accommodate a plurality of locations and/or applications that require cooling of the air medium.

In the heat pump systems300described above (seeFIGS. 12 to 17), the second usage-side flow rate adjustment valves102a,102bare provided inside the second usage units10a,10b, but it is possible to omit the second usage-side flow rate adjustment valves102a,102bfrom the second usage units10a,10band to provide an expansion valve unit17having the second usage-side flow rate adjustment valves102a,102b, as shown inFIG. 18(in this case, the hot-water/air-warming unit, the hot-water storage unit, the aqueous medium circuit80a, and the like are not shown).

Embodiments of the present invention and modifications thereof were described above with reference to the drawings, but specific configurations are not limited to these embodiments and modifications thereof, and it is possible to make modifications within a range that does not depart from the spirit of the invention.

In the heat pump systems200,300of the second and third embodiments and modifications thereof, the second usage units10a,10bmay be used for refrigeration and/or freezing, and purposes other than air cooling and air warming, rather than as usage units used for indoor air cooling and air warming.

In the heat pump system300of the third embodiment and modifications thereof, the gas-refrigerant communication tube14may be used as a refrigerant tube in which low-pressure, heat-source-side refrigerant flows in the refrigeration cycle by, e.g., placing the second heat-source-side gas refrigerant tube23band the heat-source-side intake tube21cin communication, whereby the second usage-side heat exchangers101a,101bare made to function only as evaporators of the heat-source-side refrigerant, and the second usage units10a,10bare used as cooling-dedicated usage units. In this case as well, operation in the hot-water supply/air-cooling operation mode is possible and energy savings can be ensured.

In the heat pump systems1,200,300of the first through third embodiments and modifications thereof, HFC-134a is used as the usage-side refrigerant, but no limitation is imposed thereby, and it is also possible to use, e.g., HFO-1234yf (2,3,3,3-tetrafluoro-1-propene) or another refrigerant in which the pressure that corresponds to a saturated gas temperature of 65° C. is a maximum gauge pressure of 2.8 MPa or less, preferably 2.0 MPa or less.

Industrial Applicability

The use of the present invention makes it possible to obtain a high-temperature aqueous medium in a heat pump system that can heat an aqueous medium using a heat pump cycle.