Patent Description:
In the related art, a water heating system including a water heat exchanger that heats water by using a refrigerant is known. In the water heating system, scale may adhere due to water being heated at the water heat exchanger. An example of a technique based on the assumption that scale adheres to a water heat exchanger is a heat pump hot water supply system disclosed in <CIT>. Further, <CIT> relates to a heat exchanger including a first pipe carrying a heating medium, and a second pipe carrying water that exchanges heat with the heating medium. The heating medium flowing through the first pipe and the water flowing through the second pipe form a counterflow, and the first pipe includes an internal heat exchanger for heat exchange between the heating medium flowing upstream of the first pipe and the heating medium flowing in the first pipe. <CIT> describes a heating and hot water supply apparatus using a heat pump cycle and having a pressure regulating valve which is provided between a heating condenser and a hot water supply condenser. <CIT> relates to a heat pump-type hot water feeding apparatus including a cooling cycle circuit, a heat storage tank, and a hydro kit heat exchanging unit. <CIT> discloses a hot water supply device which includes a plurality of condensers, a water storage part, a second heating passage that guides water, heated in one of the condensers, to the water storage part, and a first heating passage diverging from the second heating passage and guiding water, heated in the other of the condensers, to the water storage part.

In the heat pump hot water supply system disclosed in Patent Literature <NUM>, a water heat exchanger is divided into a high-temperature-side water heat exchanger and a low-temperature-side water heat exchanger, a hot water output temperature sensor is provided on a hot water outlet side of the high-temperature-side water heat exchanger, and a hot water temperature sensor is provided on an outlet side of the low-temperature-side water heat exchanger. In addition, the heat pump hot water supply system includes a control unit that, when a value detected by the outlet hot water temperature sensor of the low-temperature-side water heat exchanger exceeds a set value at the time of a reduction in performance caused by scale adhesion to the high-temperature-side water heat exchanger, performs suppression control on the hot water outlet temperature to be less than or equal to a set value, and outputs reduction information about the hot water output temperature and maintenance information about the high-temperature-side water heat exchanger.

However, in Patent Literature <NUM> above, the adhesion of scale is limited at the high-temperature-side water heat exchanger to prevent the spread of scale to the low-temperature-side water heat exchanger. In this way, in Patent Literature <NUM>, scale is caused to adhere to the high-temperature-side water heat exchanger. In this case, the frequency of cleaning or exchanging the high-temperature-side water heat exchanger is increased, and costs are increased.

A water heating system according to a first aspect includes a refrigerant circuit and a water circuit. The refrigerant circuit has a compressor, and a refrigerant flows in the refrigerant circuit. Water flows in the water circuit. The refrigerant circuit and the water circuit share a water heat exchanger that heats water by using the refrigerant discharged from the compressor. The water heat exchanger includes a first heat-exchanging unit. In the first heat-exchanging unit, the refrigerant and water at a water outlet portion of the water heat exchanger exchange heat with each other. The refrigerant circuit further has a heat radiator.

The heat radiator is disposed between the compressor and the first heat-exchanging unit, and radiates heat of the refrigerant discharged from the compressor to water that flows on an upstream side of the water outlet portion.

In the water heating system according to the first aspect, the first heat-exchanging unit at which the refrigerant and water at the water outlet portion exchange heat with each other is a portion at which water has a high temperature in the water heat exchanger. However, in the water heating system according to the first aspect, the heat radiator that radiates the heat of the refrigerant is disposed between the compressor and the first heat-exchanging unit. Since the heat radiator causes the refrigerant to radiate the heat before the refrigerant flows into the first heat-exchanging unit, the temperature of the refrigerant that flows into the first heat-exchanging unit can be reduced. Therefore, in the first heat-exchanging unit, it is possible to suppress an increase in the temperature of the water at the water outlet portion. Accordingly, it is possible to prevent scale from adhering to the water heat exchanger. The temperature of the water that flows on the upstream side of the water outlet portion is lower than the temperature of water that flows in the water outlet portion. Here, the heat radiator is capable of heating the low-temperature water on the upstream side by the refrigerant before water is heated at the first heat-exchanging unit. Therefore, it is possible to prevent scale from adhering to the water heat exchanger and to efficiently heat the water.

A water heating system according to a second aspect is the water heating system according to the first aspect, in which the heat radiator includes a heat storage material that radiates heat of the refrigerant.

The water heating system according to the second aspect makes it possible to prevent scale from adhering to the water heat exchanger and to store the heat of the refrigerant in the heat storage material.

A water heating system according to a third aspect is the water heating system according to the first aspect or the second aspect in which the heat radiator includes a heat-radiating device that radiates heat of the refrigerant to atmosphere.

The water heating system according to the third aspect makes it possible to prevent scale from adhering to the water heat exchanger and to radiate the heat of the refrigerant to the atmosphere.

A water heating system according to a fourth aspect is the water heating system according to the third aspect, in which the water heat exchanger further includes a second heat-exchanging unit that exchanges heat with the refrigerant on an upstream side of the first heat-exchanging unit in the water circuit. The heat radiator includes the second heat-exchanging unit.

In the water heating system according to the fourth aspect, the temperature of water that flows in the second heat-exchanging unit is lower than the temperature of water that flows in the first heat-exchanging unit. Here, the heat radiator is capable of heating the low-temperature water in the second heat-exchanging unit by using the refrigerant before water is heated at the first heat-exchanging unit. Therefore, it is possible to realize a water heating system that prevents scale from adhering to the water heat exchanger and that is capable of efficiently heating water.

A water heating system according to a fifth aspect is the water heating system according to the fourth aspect, in which the refrigerant circuit further has a bypass pipe in which the refrigerant bypasses one of the first heat-exchanging unit and the second heat-exchanging unit when a defrosting operation is performed.

In the water heating system according to the fifth aspect, due to the refrigerant bypassing the first heat-exchanging unit at the time of the defrosting operation, it is possible to use the heat amount that has been stored at the second heat-exchanging unit having a high-temperature refrigerant, as a result of which it is possible to reduce a defrosting operation time. Due to the refrigerant bypassing the second heat-exchanging unit at the time of the defrosting operation, it is possible to use the heat amount that has been stored by heat exchange with the high-temperature refrigerant, as a result of which it is possible to cause water to reach a predetermined temperature at an early stage at the time of a heating operation.

A water heating system according to a sixth aspect is the water heating system according to any one of the first aspect to the fifth aspect, in which, in at least a part of the water heat exchanger, a water flow direction and a refrigerant flow direction are in a counter-flow relationship.

The water heating system according to the sixth aspect is capable of improving heat exchange efficiency by causing the refrigerant and water to flow in a counter-flow relationship.

A water heating system according to a seventh aspect is the water heating system according to any one of the first aspect to the sixth aspect, in which at least one of the refrigerant circuit and the water circuit is configured to allow circulation also in a corresponding one of a reverse refrigerant flow direction and a reverse water flow direction.

In the water heating system according to the seventh aspect, even if scale adheres, the scale can be dispersed due to circulation in the reverse direction, as a result of which the life of the water heat exchanger can be increased.

A water heating system according to an eighth aspect is the water heating system according to any one of the first aspect to the seventh aspect, in which the water circuit further has a take-out portion that takes out water from between a water inlet portion and the water outlet portion of the water heat exchanger.

The water heating system according to the eighth aspect makes it possible to take out high-temperature water at the water outlet portion and intermediate-temperature water between the water outlet portion and the water inlet portion, the high-temperature water and the intermediate-temperature water being heated by the refrigerant in the water heat exchanger.

A water heating system according to an embodiment of the present invention is described with reference to the drawings.

A water heating system <NUM> according to an embodiment of the present invention heats water by using a refrigerant. The water heating system <NUM> of the present embodiment is a hot water supply system.

As shown in <FIG>, the water heating system <NUM> includes a refrigerant circuit <NUM> and a water circuit <NUM>. The refrigerant circuit <NUM> and the water circuit <NUM> share a water heat exchanger <NUM> that heats water by using the refrigerant.

A refrigerant flows in the refrigerant circuit <NUM>. As the refrigerant, for example, a fluid containing R32 is sealed in the refrigerant circuit <NUM>.

The refrigerant circuit <NUM> includes a compressor <NUM>, a heat radiator <NUM>, a condenser <NUM>, an expansion valve <NUM>, and an evaporator <NUM>. In the refrigerant circuit <NUM>, the compressor <NUM>, the heat radiator <NUM>, the condenser <NUM>, the expansion valve <NUM>, and the evaporator <NUM> are sequentially connected to each other by a refrigerant pipe.

The compressor <NUM> is device that compresses a low-pressure refrigerant into a high-pressure refrigerant. The compressor <NUM> of the present embodiment is a compressor of a type that is capable of controlling the number of rotations by an inverter circuit and adjusting the discharge amount of the refrigerant.

The heat radiator <NUM> radiates heat of the refrigerant discharged from the compressor <NUM>. Therefore, the temperature of the refrigerant that has passed through the heat radiator <NUM> is reduced. The heat radiator <NUM> is disposed between a first heat-exchanging unit <NUM> of the water heat exchanger <NUM> (described below) and the compressor <NUM>.

The heat radiator <NUM> exchanges heat with a heat medium that differs from water in the water circuit <NUM>. The heat radiator <NUM> of the present embodiment includes at least one of a heat storage material that radiates heat of the refrigerant and a heat-radiating device that radiates heat of the refrigerant to the atmosphere. In the heat radiator <NUM>, the heat of the refrigerant is radiated to at least one of the heat storage material and the atmosphere.

The condenser <NUM> is a condenser that condenses and liquefies the refrigerant that flows in the refrigerant circuit <NUM> by heat exchange. In the present embodiment, the condenser <NUM> includes, for example, a heat transfer tube through which, in the water heat exchanger <NUM>, the refrigerant that flows in the refrigerant circuit <NUM> passes. In the water heat exchanger <NUM>, heat is exchanged between the refrigerant that flows in the condenser <NUM> and water that flows in the water circuit <NUM>.

The expansion valve <NUM> is a valve that decompresses and expands the refrigerant that flows in the refrigerant circuit <NUM>, and is, for example, an electronic expansion valve.

The evaporator <NUM> is an evaporator that evaporates the refrigerant that flows in the refrigerant circuit <NUM> by heat exchange. The evaporator <NUM> of the present embodiment is an outdoor unit where heat is exchanged between outside air and the refrigerant.

Water flows in the water circuit <NUM>. The water circuit <NUM> includes a circulation pump <NUM>, a heat absorber <NUM>, and a hot water storage tank <NUM>. In the water circuit, the circulation pump <NUM>, the heat absorber <NUM>, and the hot water storage tank <NUM> are sequentially connected to each other by a water pipe.

The water circuit <NUM> is a hot-water-supply hot water circuit that produces hot water from water. In the water circuit <NUM>, water or hot water circulates so that hot water heated at the heat absorber <NUM> of the water heat exchanger <NUM> is stored in the hot water storage tank <NUM>.

The circulation pump <NUM> circulates water. The heat absorber <NUM> heats water that flows in the water circuit <NUM> by heat exchange. In the present embodiment, the heat absorber <NUM> includes, for example, a heat transfer tube through which, in the water heat exchanger <NUM>, water that flows in the water circuit <NUM> passes. In the water heat exchanger <NUM>, heat is exchanged between water that flows in the heat absorber <NUM> and the refrigerant that flows in the refrigerant circuit <NUM>. The hot water storage tank <NUM> stores hot water heated at the heat absorber <NUM>.

In order to supply and discharge water in the hot water storage tank <NUM>, a water supply pipe <NUM> to the hot water storage tank <NUM> and a hot water discharge pipe <NUM> from the hot water storage tank <NUM> are connected to the water circuit <NUM>.

Note that the water circuit <NUM> may further include a scale trap for trapping scale.

In the water heat exchanger <NUM>, the heat radiator <NUM> of the refrigerant circuit <NUM> and the heat absorber <NUM> of the water circuit <NUM> are integrally formed. In the water heat exchanger <NUM>, heat is exchanged between the refrigerant that flows in the heat radiator <NUM> and water that flows in the heat absorber <NUM>.

The water heat exchanger <NUM> includes a water inlet portion <NUM> and a water outlet portion <NUM> in the water circuit <NUM>. The water inlet portion <NUM> is a portion near an inlet of the water circuit <NUM> in the water heat exchanger <NUM>. The water outlet portion <NUM> is a portion near an outlet of the water circuit <NUM> in the water heat exchanger <NUM>.

The water heat exchanger <NUM> includes a refrigerant inlet portion <NUM> and a refrigerant outlet portion <NUM> in the refrigerant circuit <NUM>. The refrigerant inlet portion <NUM> is a portion near an inlet of the refrigerant circuit <NUM> in the water heat exchanger <NUM>. The refrigerant outlet portion <NUM> is a portion near an outlet of the refrigerant circuit <NUM> in the water heat exchanger <NUM>.

In the water heat exchanger <NUM>, a water flow direction and a refrigerant flow direction are in a counter-flow relationship. In <FIG>, in the water heat exchanger <NUM>, the refrigerant flow direction is a downward direction and the water flow direction is an upward direction.

The water heat exchanger <NUM> includes the first heat-exchanging unit <NUM> and a second heat-exchanging unit <NUM>. In <FIG>, an upper side of the water heat exchanger <NUM> is the first heat-exchanging unit <NUM>, and a lower side of the water heat exchanger <NUM> is the second heat-exchanging unit <NUM>.

In the first heat-exchanging unit <NUM>, the refrigerant and water at the water outlet portion <NUM> exchange heat with each other. The first heat-exchanging unit <NUM> exchanges heat with the refrigerant on a downstream side of the water circuit <NUM> in the water heat exchanger <NUM>. Here, in the first heat-exchanging unit <NUM>, water at the water outlet portion <NUM> and the refrigerant at the refrigerant inlet portion <NUM> exchange heat with each other.

The second heat-exchanging unit <NUM> exchanges heat with the refrigerant on an upstream side of the first heat-exchanging unit <NUM> in the water circuit <NUM>. In the second heat-exchanging unit <NUM>, the refrigerant and water at the water inlet portion <NUM> exchange heat with each other. Here, in the second heat-exchanging unit <NUM>, water at the water inlet portion <NUM> and the refrigerant at the refrigerant outlet portion <NUM> exchange heat with each other.

As the water heat exchanger <NUM>, for example, a double-pipe-type heat exchanger or a plate-type heat exchanger can be used. The double-pipe-type heat exchanger is a heat exchanger including an inner pipe in which a refrigerant flow path or a water flow path is formed inside, and an outer pipe that is provided on an outer side of the inner pipe and in which a water flow path or the refrigerant flow path is formed between the outer pipe and the inner pipe. The plate-type heat exchanger is a heat exchanger in which water flow paths or fluid flow paths are alternately formed between a plurality of stacked plates.

Next, an operation of the water heating system <NUM> is described.

In the refrigerant circuit <NUM>, the refrigerant discharged from the compressor <NUM> flows into the heat radiator <NUM>. The heat radiator <NUM> radiates heat of the refrigerant discharged from the compressor <NUM>. The refrigerant whose temperature has been reduced due to the heat being radiated at the heat radiator <NUM> flows into the water heat exchanger <NUM>. At the condenser <NUM> of the water heat exchanger <NUM>, heat is radiated from water, and the refrigerant is condensed. After the refrigerant condensed at the condenser <NUM> has expanded at the expansion valve <NUM>, the refrigerant flows into the evaporator <NUM>. The refrigerant absorbs heat from outside air and evaporates at the evaporator <NUM>. In the refrigerant circuit <NUM>, the refrigerant circulates in this way, and a compression stroke, a condensation stroke, an expansion stroke, and an evaporation stroke are repeated. Between the compression stroke and the condensation stroke, the refrigerant radiates heat at the heat radiator <NUM>.

In the water circuit <NUM>, water of the hot water storage tank <NUM> is supplied to the heat absorber <NUM> of the water heat exchanger <NUM> by the circulation pump <NUM>, and absorbs heat from the refrigerant and is thus heated. Hot water produced by heating returns to the hot water storage tank <NUM>, and circulation of the hot water in the water circuit <NUM> is continued until the heat storage temperature reaches a predetermined heat storage temperature.

In this way, after the refrigerant compressed to a high temperature at the compressor <NUM> has exchanged heat with a heat medium, other than water, that is heated at the heat radiator <NUM>, the refrigerant exchanges heat with water at the water outlet portion <NUM> of the water heat exchanger <NUM>.

The water heating system <NUM> of the present embodiment includes a refrigerant circuit <NUM> and a water circuit <NUM>. The refrigerant circuit <NUM> has a compressor <NUM>, and a refrigerant flows therein. Water flows in the water circuit <NUM>. The refrigerant circuit <NUM> and the water circuit <NUM> share the water heat exchanger <NUM> that heats water by using the refrigerant discharged from the compressor <NUM>. The water heat exchanger <NUM> includes a first heat-exchanging unit <NUM>. In the first heat-exchanging unit <NUM>, the refrigerant and water at the water outlet portion <NUM> exchange heat with each other. The refrigerant circuit <NUM> further has a heat radiator <NUM>. The heat radiator <NUM> is disposed between the compressor <NUM> and the first heat-exchanging unit <NUM>, and radiates heat of the refrigerant discharged from the compressor <NUM>.

In the water heating system <NUM> of the present embodiment, the first heat-exchanging unit <NUM> at which water at the water outlet portion <NUM> and the refrigerant exchange heat with each other is a portion at which water has the highest temperature in the water circuit <NUM> at the water heat exchanger <NUM>. Here, the heat radiator <NUM> that radiates heat of the refrigerant is disposed between the compressor <NUM> and the first heat-exchanging unit <NUM>. Since the heat radiator <NUM> radiates heat before the refrigerant flows into the first heat-exchanging unit <NUM>, the temperature of the refrigerant that flows into the first heat-exchanging unit <NUM> can be reduced. Therefore, in the first heat-exchanging unit <NUM>, it is possible to suppress an increase in the temperature of water at the water outlet portion <NUM>. Therefore, it is possible to suppress an increase in the temperature of a surface of the water outlet portion <NUM> of the first heat-exchanging unit <NUM>. Therefore, it is possible to prevent scale from adhering to the water heat exchanger <NUM>.

In this way, in the water heating system of the present embodiment, since it is possible to prevent scale from adhering to the water heat exchanger <NUM>, it is possible to reduce the frequency of cleaning or exchanging the water heat exchanger <NUM>.

In the water heating system <NUM>, the heat radiator <NUM> may include a heat storage material that radiates heat of the refrigerant. In this case, it is possible to prevent scale from adhering to the water heat exchanger <NUM> and to store the heat of the refrigerant in the heat storage material.

The water heating system <NUM> may include a heat-radiating device that radiates heat of the refrigerant to the atmosphere. In this case, it is possible to prevent scale from adhering to the water heat exchanger <NUM> and to radiate the heat of the refrigerant to the atmosphere.

Here, in at least a part of the water heat exchanger <NUM>, the water flow direction and the refrigerant flow direction are in a counter-flow relationship. By causing the refrigerant and water to flow in a counter-flow relationship, it is possible to improve heat exchange efficiency.

Although the heat radiator <NUM> of the first embodiment above includes at least one of a heat storage material and a heat-radiating device, the heat radiator <NUM> is not limited as long as it exchanges heat with a heat medium that differs from water in the water circuit <NUM>. In the present modification, the refrigerant circuit <NUM> has a plurality of outdoor units, at least one outdoor unit is used as an evaporator, and the other outdoor unit is used as the heat radiator <NUM>.

A water heating system <NUM> of a second embodiment shown in <FIG> is basically the same as the water heating system <NUM> of the first embodiment, but differs primarily in a heat radiator <NUM>. Although the heat radiator <NUM> of the first embodiment exchanges heat with a heat medium that differs from water in the water circuit <NUM>, the heat radiator <NUM> of the second embodiment exchanges heat with water in a water circuit <NUM>. As shown in <FIG>, in the water heating system <NUM> of the present embodiment, the heat radiator <NUM> is configured to radiate heat of a refrigerant to water that flows on an upstream side of a water outlet portion <NUM>.

In the heat radiator <NUM>, a heat medium with which the refrigerant discharged from a compressor <NUM> exchanges heat is water that is heated in a water heat exchanger <NUM>. Specifically, in a refrigerant pipe in which the refrigerant discharged from the compressor <NUM> flows, the heat radiator <NUM> is disposed on a portion close to a water pipe on an upstream side of the water heat exchanger <NUM>. Here, a refrigerant circuit <NUM> has a first refrigerant pipe <NUM> that connects the compressor <NUM> and the heat radiator <NUM> to each other and a second refrigerant pipe <NUM> that connects the heat radiator <NUM> and a refrigerant inlet portion <NUM> to each other.

Since the water circuit <NUM> and the water heat exchanger <NUM> are the same as those of the first embodiment, the description thereof is not repeated.

In the refrigerant circuit <NUM>, the refrigerant discharged from the compressor <NUM> flows into the heat radiator <NUM> via the first refrigerant pipe <NUM>. The heat radiator <NUM> radiates heat of the refrigerant discharged from the compressor <NUM> to water in the water circuit <NUM>. The refrigerant whose temperature has been reduced due to the heat being radiated at the heat radiator <NUM> flows into the water heat exchanger <NUM> via the second refrigerant pipe <NUM>. At a condenser <NUM> of the water heat exchanger <NUM>, heat is radiated from water, and the refrigerant is condensed. After the refrigerant condensed at the condenser <NUM> has expanded at an expansion valve <NUM>, the refrigerant flows into an evaporator <NUM>. At the evaporator <NUM>, heat is absorbed from outside air, and the refrigerant is evaporated. In the refrigerant circuit <NUM>, the refrigerant circulates in this way, and a compression stroke, a condensation stroke, an expansion stroke, and an evaporation stroke are repeated.

In the water circuit <NUM>, water of a hot water storage tank <NUM>, before being supplied to a heat absorber <NUM> of the water heat exchanger <NUM> by a circulation pump <NUM>, absorbs heat from the refrigerant that flows in the heat radiator <NUM> and is heated. The water that has been heated by the heat radiator <NUM> flows into the water heat exchanger <NUM> and further absorbs heat from the refrigerant at the heat absorber <NUM>, as a result of which the water is heated. Hot water produced by the heating returns to the hot water storage tank <NUM>.

In this way, after the refrigerant compressed to a high temperature at the compressor <NUM> has exchanged heat with water that flows on the upstream side of the water outlet portion <NUM>, the refrigerant exchanges heat with water at the water outlet portion <NUM> of the water heat exchanger <NUM>.

The water heating system <NUM> of the present embodiment is configured to radiate heat of the refrigerant to water that flows on the upstream side of the water outlet portion <NUM>.

In the water circuit <NUM> of the water heating system <NUM>, the temperature of water that flows on the upstream side of the water outlet portion <NUM> is lower than the temperature of water that flows in the water outlet portion <NUM>. Here, the heat radiator <NUM> is capable of heating the low-temperature water on the upstream side by the refrigerant before the water is heated at the first heat-exchanging unit <NUM>. Therefore, it is possible to prevent scale from adhering to the water heat exchanger <NUM> and to efficiently heat water.

A water heating system <NUM> of a third embodiment shown in <FIG> is basically the same as the water heating system <NUM> of the second embodiment, but differs primarily in a water heat exchanger <NUM> and a heat radiator <NUM>. Although the first heat-exchanging unit <NUM> and the second heat-exchanging unit <NUM> are disposed at one water heat exchanger <NUM> in the second embodiment, they are disposed at different water heat exchangers in the third embodiment. As shown in <FIG>, the water heating system <NUM> of the present embodiment includes a water heat exchanger constituted by a first heat-exchanging unit <NUM> and a water heat exchanger constituted by a second heat-exchanging unit <NUM>. The heat radiator <NUM> includes the second heat-exchanging unit <NUM>.

A refrigerant circuit <NUM> includes a compressor <NUM>, a first condenser 13a, a second condenser 13b, an expansion valve <NUM>, and an evaporator <NUM>. In the refrigerant circuit <NUM>, the compressor <NUM>, the first condenser 13a, the second condenser 13b, the expansion valve <NUM>, and the evaporator <NUM> are sequentially connected to each other by a refrigerant pipe. A first refrigerant pipe <NUM> connects the compressor <NUM> and the first condenser 13a to each other. A second refrigerant pipe <NUM> connects the first condenser 13a and the second condenser 13b to each other. A third refrigerant pipe <NUM> connects the second condenser 13b and the evaporator <NUM> to each other.

The first condenser 13a is disposed at the second heat-exchanging unit <NUM> of a water heat exchanger <NUM>. At the first condenser 13a, in the second heat-exchanging unit <NUM>, heat is exchanged between a refrigerant that flows in the first condenser 13a and water that flows in a water circuit <NUM>.

The second condenser 13b is connected in series with the first condenser 13a. The second condenser 13b is disposed at the first heat-exchanging unit <NUM> of the water heat exchanger <NUM>. At the second condenser 13b, in the first heat-exchanging unit <NUM>, heat is exchanged between a refrigerant that flows in the second condenser 13b and water that flows in the water circuit <NUM>.

The heat radiator <NUM> of the present embodiment is the second heat-exchanging unit <NUM> in the refrigerant circuit <NUM>. Therefore, the heat radiator <NUM> radiates the heat of the refrigerant to water that flows in the second heat-exchanging unit <NUM>.

The water circuit <NUM> includes a circulation pump <NUM>, a first heat absorber 22a, a second heat absorber 22b, and a hot water storage tank <NUM>. In the water circuit <NUM>, the circulation pump <NUM>, the first heat absorber 22a, the second heat absorber 22b, and the hot water storage tank <NUM> are sequentially connected to each other by a water pipe.

The first heat absorber 22a is disposed at the second heat-exchanging unit <NUM> of the water heat exchanger <NUM>. At the first heat absorber 22a, in the second heat-exchanging unit <NUM>, heat is exchanged with the refrigerant that flows in the first condenser 13a.

The second heat absorber 22b is connected in series with the first heat absorber 22a. The second heat absorber 22b is disposed at the first heat-exchanging unit <NUM> of the water heat exchanger <NUM>. At the second heat absorber 22b, in the first heat-exchanging unit <NUM> of the water heat exchanger <NUM>, heat is exchanged between water that flows in the second heat absorber 22b and water that flows in the refrigerant circuit <NUM>.

The water heat exchanger <NUM> is divided into a water heat exchanger including the first heat-exchanging unit <NUM> and a water heat exchanger including the second heat-exchanging unit <NUM>. The first heat-exchanging unit <NUM> has a water outlet portion <NUM> and a refrigerant outlet portion <NUM>. The water outlet portion <NUM> corresponds to the second heat absorber 22b, and the refrigerant outlet portion <NUM> corresponds to the second condenser 13b. The second heat-exchanging unit <NUM> has a water inlet portion <NUM> and a refrigerant inlet portion <NUM>. The water inlet portion <NUM> corresponds to the first heat absorber 22a, and the refrigerant inlet portion <NUM> corresponds to the first condenser 13a.

In the first heat-exchanging unit <NUM>, a water flow direction and a refrigerant flow direction are in a counter-flow relationship. In the second heat-exchanging unit <NUM>, a water flow direction and a refrigerant flow direction are in a counter-flow relationship. In <FIG>, the refrigerant flow direction in the first heat-exchanging unit <NUM> and the refrigerant flow direction in the second heat-exchanging unit <NUM> are the same. In <FIG>, the water flow direction in the first heat-exchanging unit <NUM> and the water flow direction in the second heat-exchanging unit <NUM> are the same.

Here, the water heat exchanger <NUM> is constituted by two heat exchangers. In the present description, in the water heat exchanger <NUM> that is constituted by one or a plurality of heat exchangers, the water outlet portion <NUM> is an outlet vicinity portion including an outlet that is positioned on a most downstream side of the water circuit <NUM>.

In the refrigerant circuit <NUM>, the refrigerant discharged from the compressor <NUM> flows into the second heat-exchanging unit <NUM>, serving as the heat radiator <NUM>, via the first refrigerant pipe <NUM>. At the second heat-exchanging unit <NUM>, in the first condenser 13a, heat of the refrigerant discharged from the compressor <NUM> is radiated to water in the water circuit <NUM>. The refrigerant whose temperature has been reduced due to the heat being radiated at the heat radiator <NUM> flows into the first heat-exchanging unit <NUM> via the second refrigerant pipe <NUM>. At the first heat-exchanging unit <NUM>, in the second condenser 13b, heat is radiated to water in the water circuit <NUM> and the refrigerant is condensed. After the refrigerant condensed at the first condenser <NUM> and the second condenser <NUM> has expanded at the expansion valve <NUM>, the refrigerants flow into the evaporator <NUM> via the third refrigerant pipe <NUM>.

In the water circuit <NUM>, water of the hot water storage tank <NUM> flows into the second heat-exchanging unit <NUM> by the circulation pump <NUM>. At the second heat-exchanging unit <NUM>, serving as the heat radiator <NUM>, water of the water circuit <NUM> absorbs heat from the refrigerant and is heated at the first heat absorber 22a. The water that has been heated at the heat radiator <NUM> flows into the first heat-exchanging unit <NUM> and further absorbs heat from the refrigerant at the second heat absorber 22b, as a result of which the water is heated. Hot water produced by the heating returns to the hot water storage tank <NUM>.

In this way, after the refrigerant compressed to a high temperature at the compressor <NUM> has exchanged heat with water at the second heat-exchanging unit <NUM>, the refrigerant exchanges heat with water at the water outlet portion <NUM> of the first heat-exchanging unit <NUM>.

The water heat exchanger <NUM> of the water heating system <NUM> of the present embodiment further includes the second heat-exchanging unit <NUM> that exchanges heat with the refrigerant on an upstream side of the first heat-exchanging unit <NUM> in the water circuit <NUM>. The heat radiator <NUM> includes the second heat-exchanging unit <NUM>.

In the water heating system <NUM> of the present embodiment, the temperature of water that flows in the second heat-exchanging unit <NUM> is lower than the temperature of water that flows in the first heat-exchanging unit <NUM>. Here, the heat radiator <NUM> is capable of heating the low-temperature water at the second heat-exchanging unit <NUM> by the refrigerant before the water is heated at the first heat-exchanging unit <NUM>. Therefore, it is possible to realize the water heating system <NUM> that is capable of preventing scale from adhering to the water heat exchanger <NUM> and that is capable of efficiently heating water.

Although the water heating system <NUM> of the above-described embodiment includes two separated water heat exchangers, a water heating system 3a of the present modification shown in <FIG> includes a first heat-exchanging unit <NUM> and a second heat-exchanging unit <NUM> that are separated by a refrigerant flow path of one water heat exchanger <NUM>.

The water heat exchanger <NUM> includes the first heat-exchanging unit <NUM> and the second heat-exchanging unit <NUM>. In the refrigerant circuit <NUM> inside the water heat exchanger <NUM>, a refrigerant flow path that passes through the first heat-exchanging unit <NUM> and a refrigerant flow path that passes through the second heat-exchanging unit <NUM> are separated from each other. The second refrigerant pipe <NUM> of the refrigerant circuit <NUM> causes a refrigerant that has flowed out from the first heat-exchanging unit <NUM> to flow into the second heat-exchanging unit <NUM> of the water heat exchanger <NUM> that is shared with the first heat-exchanging unit <NUM>.

Plate-type heat exchangers are suitably used as water heat exchangers in the water heating system <NUM> of the above-described embodiment in which the first heat-exchanging unit <NUM> and the second heat-exchanging unit <NUM> are separated into a plurality of water heat exchangers. On the other hand, a double-pipe-type heat exchanger is suitably used as a water heat exchanger in the water heating system 3a of the present modification in which one water heat exchanger is divided into the first heat-exchanging unit <NUM> and the second heat-exchanging unit <NUM> by the refrigerant flow path.

A water heating system <NUM> of a fourth embodiment shown in <FIG> is basically the same as the water heating system <NUM> of the third embodiment, but differs primarily in a refrigerant circuit <NUM>. The water heating system <NUM> of the present embodiment is capable of performing a defrosting operation for defrosting. The refrigerant circuit <NUM> further has a bypass pipe <NUM> in which a refrigerant bypasses a first heat-exchanging unit <NUM> when a defrosting operation is performed.

The refrigerant circuit <NUM> further has the bypass pipe <NUM>, a first valve B1, and a second valve B2.

The bypass pipe <NUM> is connected to a second refrigerant pipe <NUM> that connects a first condenser 13a and a second condenser 13b to each other and to a third refrigerant pipe <NUM> that connects the second condenser 13b and an expansion valve <NUM> to each other. When a defrosting operation is performed, the refrigerant that flows in the third refrigerant pipe <NUM> bypasses the first heat-exchanging unit <NUM> and flows in the second refrigerant pipe <NUM> due to the bypass pipe <NUM>.

The first valve B1 is provided at the second refrigerant pipe <NUM>. The second valve B2 is provided at the bypass pipe <NUM>. The first valve B1 and the second valve B2 are on-off valves.

Since a water circuit <NUM> and a water heat exchanger <NUM> are the same as those of the third embodiment, a description thereof is not repeated.

<FIG> shows flows of the refrigerant and water when a heating operation of the present embodiment is performed. A heating operation of the water heating system <NUM> is described with reference to <FIG>.

At the time of the heating operation, the first valve B1 is fully open and the second valve B2 is fully closed. In the refrigerant circuit <NUM>, the refrigerant discharged from a compressor <NUM> passes through a first refrigerant pipe <NUM> and flows into a second heat-exchanging unit <NUM>, serving as a heat radiator <NUM>. At the second heat-exchanging unit <NUM>, in the first condenser 13a, heat of the refrigerant discharged from the compressor <NUM> is radiated to water in the water circuit <NUM>. Since the first valve B1 is open, the refrigerant whose temperature has been reduced due to the heat being radiated at the heat radiator <NUM> flows through the second refrigerant pipe <NUM> and flows into the first heat-exchanging unit <NUM>. At the first heat-exchanging unit <NUM>, in the second condenser 13b, heat is radiated to water in the water circuit <NUM> and the refrigerant is condensed. After the refrigerant condensed at the second condenser <NUM> has passed through the third refrigerant pipe <NUM> and has expanded at the expansion valve <NUM>, the refrigerant flows into an evaporator <NUM>.

In the water circuit <NUM>, water of a hot water storage tank <NUM> flows sequentially into the second heat-exchanging unit <NUM> and the first heat-exchanging unit <NUM> by a circulation pump <NUM>. Water in the water circuit <NUM> is heated by the refrigerant at the second heat-exchanging unit <NUM> and the first heat-exchanging unit <NUM>. Hot water produced by the heating returns to the hot water storage tank <NUM>.

<FIG> shows flows of the refrigerant and water when a defrosting operation of the present embodiment is performed. In <FIG>, a water inlet portion <NUM>, a water outlet portion <NUM>, a refrigerant inlet portion <NUM>, and a refrigerant outlet portion <NUM> are each provided with a reference sign based on a direction of flow of the refrigerant and water when a heating operation is performed (the same as in <FIG>). A defrosting operation of the water heating system <NUM> is described with reference to <FIG>.

When, at the time of the heating operation, frost formation is detected due to, for example, a reduction in the temperature of the refrigerant at the evaporator <NUM>, a defrosting operation that dissolves the frost that has adhered to the evaporator <NUM> is performed.

When the defrosting operation is performed, the first valve B1 is fully closed and the second valve B2 is fully open. The refrigerant discharged from the compressor <NUM> flows into a heat exchanger that functions as the evaporator <NUM> when a heating operation is performed, radiates heat to outside air, and is condensed. Although the refrigerant passes through the third refrigerant pipe <NUM> after being expanded at the expansion valve <NUM>, since the first valve B1 is closed and the second valve B2 is open, the refrigerant bypasses the first heat-exchanging unit <NUM> and passes through the bypass pipe <NUM>. The refrigerant flows through the second refrigerant pipe <NUM> connected to the bypass pipe <NUM> and flows into the second heat-exchanging unit <NUM>. The refrigerant passes through a flow path that functions as the first condenser 13a when a heating operation is performed and the first refrigerant pipe <NUM>, and is sucked into the compressor <NUM>.

In the water heating system <NUM> of the present embodiment, the refrigerant circuit <NUM> further has a bypass pipe <NUM> in which the refrigerant bypasses the first heat-exchanging unit <NUM> when a defrosting operation is performed. Since, by bypassing the first heat-exchanging unit <NUM> when a defrosting operation is performed, it is possible to use the heat amount that has been stored at the second heat-exchanging unit <NUM> that contains a high-temperature refrigerant, it is possible to reduce a defrosting operation time.

A water heating system <NUM> of a fifth embodiment shown in <FIG> is basically the same as the water heating system <NUM> of the third embodiment, but differs primarily in a refrigerant circuit <NUM>. The water heating system <NUM> of the present embodiment is capable of performing a defrosting operation. The refrigerant circuit <NUM> further has a bypass pipe <NUM> in which a refrigerant bypasses a second heat-exchanging unit <NUM> when a defrosting operation is performed.

The bypass pipe <NUM> is connected to a first refrigerant pipe <NUM> that connects a compressor <NUM> and a first condenser 13a to each other and to a second refrigerant pipe <NUM> that connects the first condenser 13a and a second condenser 13b to each other. When a defrosting operation is performed, the refrigerant that flows in the second refrigerant pipe <NUM> bypasses the second heat-exchanging unit <NUM> and flows in the first refrigerant pipe <NUM> due to the bypass pipe <NUM>.

At the time of the heating operation, the first valve B1 is fully open and the second valve B2 is fully closed. In the refrigerant circuit <NUM>, since the first valve B1 is open, the refrigerant discharged from the compressor <NUM> flows through the first refrigerant pipe <NUM> and flows into the second heat-exchanging unit <NUM>, serving as a heat radiator <NUM>. At the second heat-exchanging unit <NUM>, in the first condenser 13a, heat of the refrigerant discharged from the compressor <NUM> is radiated to water in the water circuit <NUM>. The refrigerant whose temperature has been reduced due to the heat being radiated at the heat radiator <NUM> flows through the second refrigerant pipe <NUM> and flows into the first heat-exchanging unit <NUM>. At the first heat-exchanging unit <NUM>, in the second condenser 13b, heat is radiated to water in the water circuit <NUM> and the refrigerant is condensed. After the refrigerant condensed at the second condenser <NUM> has passed through a third refrigerant pipe <NUM> and has expanded at an expansion valve <NUM>, the refrigerant flows into an evaporator <NUM>.

When the defrosting operation is performed, the first valve B1 is fully closed and the second valve B2 is fully open. The refrigerant discharged from the compressor <NUM> flows into a heat exchanger that functions as the evaporator <NUM> when a heating operation is performed, radiates heat to outside air, and is condensed. After the refrigerant has expanded at the expansion valve <NUM>, the refrigerant flows through the third refrigerant pipe <NUM> and flows into the first heat-exchanging unit <NUM>. Then, the refrigerant flows through a flow path that functions as a second condenser 13b when a heating operation is performed, and flows out from the first heat-exchanging unit <NUM>. Thereafter, although the refrigerant passes through the second refrigerant pipe <NUM>, since the first valve B1 is closed and the second valve B2 is open, the refrigerant bypasses the second heat-exchanging unit <NUM> and passes through the bypass pipe <NUM>. The refrigerant passes through the first refrigerant pipe <NUM> that is connected to the bypass pipe <NUM>, and is sucked into the compressor <NUM>.

In the water heating system <NUM> of the present embodiment, the refrigerant circuit <NUM> further has a bypass pipe <NUM> in which a refrigerant bypasses the second heat-exchanging unit <NUM> when a defrosting operation is performed. Due to the refrigerant bypassing the second heat-exchanging unit <NUM> at the time of a defrosting operation, it is possible to use the heat amount that has been stored by heat exchange with a high-temperature refrigerant, as a result of which it is possible to cause water to reach a predetermined temperature at an early stage at the time of a heating operation.

In the fourth embodiment, the refrigerant circuit <NUM> further has the bypass pipe <NUM> in which the refrigerant bypasses the first heat-exchanging unit <NUM> when a defrosting operation is performed. In the fifth embodiment, the refrigerant circuit <NUM> further has a bypass pipe <NUM> in which a refrigerant bypasses the second heat-exchanging unit <NUM> when a defrosting operation is performed. In the present modification, as shown in <FIG>, the refrigerant circuit <NUM> further has a bypass pipe <NUM> in which a refrigerant bypasses the first heat-exchanging unit <NUM> and the second heat-exchanging unit <NUM> when a defrosting operation is performed.

A water heating system of the present modification has a configuration that is the same as the configuration of the water heating system of the first embodiment shown in <FIG>, but differs in that the refrigerant circuit <NUM> further has a bypass pipe <NUM>. The bypass pipe <NUM> of the present modification is connected to the second refrigerant pipe <NUM> that connects the heat radiator <NUM> and the condenser <NUM> to each other and to the third refrigerant pipe <NUM> that connects the condenser <NUM> and the expansion valve <NUM> to each other.

By closing the second valve B2 that is provided at the bypass pipe <NUM> and opening the first valve B1 that is provided at the second refrigerant pipe <NUM>, it is possible to perform a heating operation. By opening the second valve B2 that is provided at the bypass pipe <NUM> and closing the first valve B1 that is provided at the second refrigerant pipe <NUM>, it is possible to perform a defrosting operation.

A water heating system <NUM> of a sixth embodiment shown in <FIG> and <FIG> is basically the same as the water heating system <NUM> of the third embodiment, but differs primarily in a refrigerant circuit <NUM> and a water circuit <NUM>. The water heating system <NUM> of the present embodiment is configured so that at least one of the refrigerant circuit <NUM> and the water circuit <NUM> is configured to allow circulation also in a corresponding one of a reverse refrigerant flow direction and a reverse water flow direction.

The refrigerant circuit <NUM> further has a switching mechanism <NUM>. The switching mechanism <NUM> is a flow-path switching mechanism that switches a flow of a refrigerant in the refrigerant circuit <NUM>. Here, the switching mechanism <NUM> is a four-way switching valve. The switching mechanism <NUM> switches the direction of flow of the refrigerant between a first direction and a second direction that is a direction opposite to the first direction.

When the refrigerant is caused to flow in the first direction shown in <FIG>, as indicated by a solid line of the switching mechanism <NUM> in <FIG>, the switching mechanism <NUM> causes a first port 41a and a second port 41b to communicate with each other and causes a third port 41c and a fourth port 41d to communicate with each other. Therefore, a compressor <NUM> and a first condenser 13a are connected to each other, and a second condenser 13b and an expansion valve <NUM> are connected to each other.

When the refrigerant is caused to flow in the second direction shown in <FIG>, as indicated by a solid line of the switching mechanism in <FIG>, the switching mechanism <NUM> causes the first port 41a and the third port 41c to communicate with each other and causes the second port 41b and the fourth port 41d to communicate with each other. Therefore, the compressor <NUM> and the second condenser 13b are connected to each other, and the first condenser 13a and the expansion valve <NUM> are connected to each other.

The water circuit <NUM> further has a switching mechanism <NUM>. The switching mechanism <NUM> is a flow-path switching mechanism that switches the flow of water in the water circuit <NUM>. Here, the switching mechanism <NUM> is a four-way switching valve. The switching mechanism <NUM> switches the direction of flow of water between a first direction and a second direction that is a direction opposite to the first direction.

When the refrigerant is caused to flow in the first direction shown in <FIG>, as indicated by a solid line of the switching mechanism <NUM> in <FIG>, the switching mechanism <NUM> causes a first port 42a and a second port 42b to communicate with each other and causes a third port 42c and a fourth port 42d to communicate with each other. Therefore, a water supply port to a water heat exchanger <NUM> in a hot water tank <NUM> and a first heat absorber 22a are connected to each other, and a hot water receiving port from the water heat exchanger <NUM> in the hot water tank <NUM> and a second heat absorber 22b are connected to each other.

When water is to be caused to flow in the second direction shown in <FIG>, as indicated by a solid line of the switching mechanism in <FIG>, the switching mechanism <NUM> causes the first port 42a and the third port 42c to communicate with each other and causes the second port 42b and the fourth port 42d to communicate with each other. Therefore, the water supply port to the water heat exchanger <NUM> and the second heat absorber 22b are connected to each other, and the water receiving port from the water heat exchanger <NUM> in the hot water tank <NUM> and the first heat absorber 22a are connected to each other.

When the water heat exchanger <NUM> causes the refrigerant of the refrigerant circuit <NUM> and water of the water circuit <NUM> to circulate in a reverse direction by using a corresponding one of the switching mechanisms <NUM> and <NUM>, the first heat-exchanging unit <NUM> and the second heat-exchanging unit <NUM> are reversed.

When the refrigerant and water circulate in the first direction shown in <FIG>, a water heat exchanger on an upper side in <FIG> constitutes the first heat-exchanging unit <NUM>, and a water heat exchanger on a lower side in <FIG> constitutes the second heat-exchanging unit <NUM>. When the refrigerant and water circulate in the second direction shown in <FIG>, a water heat exchanger on a lower side in <FIG> constitutes the first heat-exchanging unit <NUM>, and a water heat exchanger on an upper side in <FIG> constitutes the second heat-exchanging unit <NUM>.

The water heating system <NUM> of the present embodiment is capable of performing a first heating operation in which the refrigerant and water flow in the first direction and a second heating operation in which the refrigerant and water flow in the second direction. The first heating operation and the second heating operation can be selected as appropriate. Here, the first heating operation and the second heating operation are alternately switched at a predetermined operation time.

<FIG> illustrates flows of the refrigerant and water in the first direction of the present embodiment. With reference to <FIG>, a heating operation of the water heating system <NUM> when the refrigerant and water flow in the first direction is described.

In the refrigerant circuit <NUM>, when the switching mechanism <NUM> is switched as shown in <FIG>, the refrigerant discharged from the compressor <NUM> flows through the second port 41a from the first port 41b and flows into the second heat-exchanging unit <NUM>, serving as a heat radiator <NUM>. At the second heat-exchanging unit <NUM>, in the first condenser 13a, heat of the refrigerant discharged from the compressor <NUM> is radiated to water in the water circuit <NUM>. The refrigerant whose temperature has been reduced due to the heat being radiated at the heat radiator <NUM> flows into the first heat-exchanging unit <NUM> via a second refrigerant pipe <NUM>. At the first heat-exchanging unit <NUM>, in the second condenser 13b, heat is radiated to water in the water circuit <NUM> and the refrigerant is condensed. After the refrigerant condensed at the second condenser 13b has passed through the fourth port 41d from the third port 41c and has expanded at the expansion valve <NUM>, the refrigerant flows into the evaporator <NUM>.

In the water circuit <NUM>, when the switching mechanism <NUM> is switched as shown in <FIG>, water of the hot water storage tank <NUM> passes through the second port 42b from the first port 42a and flows into the second heat-exchanging unit <NUM>. At the second heat-exchanging unit <NUM>, in the first heat absorber 22a, water in the water circuit <NUM> is heated by the heat radiator <NUM> due to heat being absorbed from the refrigerant. The water that has been heated at the heat radiator <NUM> flows into the first heat-exchanging unit <NUM> and further absorbs heat from the refrigerant at the second heat absorber 22b, as a result of which the water is heated. Hot water produced by the heating returns to the hot water storage tank <NUM> via the fourth port 42d from the third port 42c.

<FIG> illustrates flows of the refrigerant and water in the second direction of the present embodiment. A heating operation of the water heating system <NUM> when the refrigerant and water flow in the second direction is described with reference to <FIG>.

When the switching mechanism <NUM> is switched as shown in <FIG>, in the refrigerant circuit <NUM>, the refrigerant discharged from the compressor <NUM> flows through the third port 41c from the first port 41a and flows into the second heat-exchanging unit <NUM>, serving as the heat radiator <NUM>. At the second heat-exchanging unit <NUM>, in the second condenser 13b, heat of the refrigerant discharged from the compressor <NUM> is radiated to water in the water circuit <NUM>. The refrigerant whose temperature has been reduced due to the heat being radiated at the heat radiator <NUM> flows into the first heat-exchanging unit <NUM> via a second refrigerant pipe <NUM>. At the first heat-exchanging unit <NUM>, in the first condenser 13a, heat is radiated to water in the water circuit <NUM> and the refrigerant is condensed. After the refrigerant condensed at the first condenser 13a has passed through the fourth port 41d from the second port 41b and has expanded at the expansion valve <NUM>, the refrigerant flows into the evaporator <NUM>.

When the switching mechanism <NUM> is switched as shown in <FIG>, in the water circuit <NUM>, water of the hot water storage tank <NUM> passes through the third port 42c from the first port 42a and flows into the second heat-exchanging unit <NUM>. At the second heat-exchanging unit <NUM>, in the second heat absorber 22b, water in the water circuit <NUM> is heated by the heat radiator <NUM> due to heat being absorbed from the refrigerant. The water that has been heated at the heat radiator <NUM> flows into the first heat-exchanging unit <NUM> and further absorbs heat from the refrigerant at the first heat absorber 22a, as a result of which the water is heated. Hot water produced by the heating returns to the hot water storage tank <NUM> via the fourth port 42d from the second port 42b.

In the water heating system <NUM> of the present embodiment, the refrigerant circuit <NUM> and the water circuit <NUM> are configured to allow circulation also in a corresponding one of the reverse refrigerant flow direction and the reverse water flow direction. Even if scale adheres, the scale can be dispersed due to the circulation in a reverse direction, as a result of which the life of the water heat exchanger <NUM> can be increased.

In the embodiment above, both of the refrigerant circuit <NUM> and the water circuit <NUM> are configured to allow circulation also in a corresponding one of the reverse refrigerant flow direction and the reverse water flow direction. In the present modification, although the refrigerant circuit <NUM> is configured to cause a refrigerant to also circulate in a reverse direction, the water circuit <NUM> is configured to cause the water flow direction to be constant. Alternatively, while the water circuit <NUM> may be configured to allow circulation also in the reverse water flow direction, the refrigerant circuit <NUM> may be configured to cause the refrigerant flow direction to be constant.

Although in the embodiment above, the switching mechanism <NUM> of the refrigerant circuit <NUM> and the switching mechanism <NUM> of the water circuit <NUM> are each a four-way switching valve, they are not limited thereto. The switching mechanism <NUM> of the water circuit <NUM> of the present modification is a two-way switching valve or a reverse circulation pump.

A water heating system <NUM> of a seventh embodiment shown in <FIG> is basically the same as the water heating system <NUM> of the third embodiment, but differs primarily in a water circuit <NUM>. In the water heating system <NUM> of the present embodiment, the water circuit <NUM> further has a take-out portion <NUM> that takes out water from between a water inlet portion <NUM> and a water outlet portion <NUM> of a water heat exchanger <NUM>.

The water circuit <NUM> further has the take-out portion <NUM>, a third valve B3, a fourth valve B4, and an intermediate-temperature water tank 23b. The hot water tank <NUM> of the third embodiment shown in <FIG> corresponds to a high-temperature water tank 23a of the present embodiment shown in <FIG>.

The intermediate-temperature water tank 23b stores water having a temperature that is lower than the temperature of water that is stored in the high-temperature water tank 23a.

The take-out portion <NUM> of the present embodiment is a pipe that branches off from between a first heat absorber 22a and a second heat absorber 22b and that is connected to a receiving port of the intermediate-temperature water tank 23b in the water circuit <NUM>.

The intermediate-temperature water tank 23b receives intermediate-temperature water from the take-out portion <NUM>. Here, the intermediate-temperature water tank 23b is connected to a first water pipe <NUM> that supplies water to the water heat exchanger <NUM>. Therefore, the water circuit <NUM> has a first water circuit in the high-temperature water tank 23a and a second water circuit in the intermediate-temperature water tank 23b. Note that the water circuit <NUM> may not have a first water pipe <NUM>, and the intermediate-temperature water tank 23b may be constituted by a first water circuit that only receives intermediate-temperature water.

The third valve B3 is provided at the take-out portion <NUM>. The fourth valve B4 is provided at a water pipe <NUM> that connects the second heat absorber 22b and the high-temperature water tank 23a to each other. The third valve B3 and the fourth valve B4 are on-off valves.

Note that the water circuit <NUM> may further have a water pipe (not shown) that sends high-temperature water to intermediate-temperature water.

Since a refrigerant circuit <NUM> and the water heat exchanger <NUM> are the same as those of the third embodiment, the description thereof is not repeated.

First, a heating operation of taking out intermediate-temperature water and high-temperature water by opening the third valve B3 and the fourth valve B4 is described.

In the water circuit <NUM>, water at the high-temperature water tank 23a and water at the intermediate-temperature water tank 23b flow into a second heat-exchanging unit <NUM> by a circulation pump <NUM>. At the second heat-exchanging unit <NUM>, in the first heat absorber 22a, water in the water circuit <NUM> is heated by a heat radiator <NUM> due to heat being absorbed from a refrigerant.

A part of the water that has been heated at the heat radiator <NUM> flows into the first heat-exchanging unit <NUM> and further absorbs heat from the refrigerant at the second heat absorber 22b, as a result of which the water is heated. High-temperature water produced by the heating flows into the high-temperature water tank 23a.

The remaining water that has been heated at the heat radiator <NUM> flows as intermediate-temperature water into the intermediate-temperature water tank 23b via the take-out portion <NUM>.

In this way, the water heating system <NUM> of the present embodiment is capable of performing a heating operation that takes out intermediate-temperature water and high-temperature water. The ratio between the production of intermediate-temperature water and the production of high-temperature water can be arbitrarily changed by adjusting the opening degree of the third valve B3 and the opening degree of the fourth valve B4.

When the third valve B3 is closed and the fourth valve B4 is opened, a heating operation that takes out only high-temperature water is possible as in the third embodiment. When the third valve is opened and the fourth valve is closed, a heating operation that takes out only intermediate-temperature water is possible.

In the water heating system <NUM> of the present embodiment, the water circuit <NUM> further has a take-out portion <NUM> that takes out water from between the water inlet portion <NUM> and the water outlet portion <NUM> of the water heat exchanger <NUM>. Therefore, it is possible to take out high-temperature water at the water outlet portion <NUM> and intermediate-temperature water between the water outlet portion <NUM> and the water inlet portion <NUM>, the high-temperature water and the intermediate-temperature water being heated by the refrigerant in the water heat exchanger <NUM>.

In the water heating systems <NUM> to <NUM> of the first to seventh embodiments described above, in the water heat exchanger <NUM>, the water flow direction and the refrigerant flow direction are in a counter-flow relationship. In a water heating system <NUM> of the present embodiment shown in <FIG>, in at least a part of a water heat exchanger <NUM>, the water flow direction and the refrigerant flow direction are in a parallel-flow relationship.

A refrigerant circuit <NUM> of the present embodiment is basically the same as the refrigerant circuit <NUM> of the water heating system 3a shown in <FIG>, but differs in that a refrigerant outlet is positioned at one end of the water heat exchanger <NUM> (an upper end in <FIG>).

In a first heat-exchanging unit <NUM>, in <FIG>, a refrigerant flows upward and water flows upward. Therefore, in the first heat-exchanging unit <NUM>, water and the refrigerant exchange heat in a parallel flow.

In a second heat-exchanging unit <NUM>, in <FIG>, the refrigerant flows downward and water flows upward. Therefore, in the second heat-exchanging unit <NUM>, water and the refrigerant exchange heat with each other in a counter-flow.

In the water heating system <NUM> of the present embodiment, in at least a part of the water heat exchanger <NUM>, the water flow direction and the refrigerant flow direction are in a parallel flow relationship. Here, in a part of the water heat exchanger <NUM>, the water flow direction and the refrigerant flow direction are in a parallel flow relationship. In this way, the water heat exchanger <NUM> can be configured so that the water heating system <NUM> causes the refrigerant and water to exchange heat with each other in a counter-flow and/or a parallel flow.

A water heating system <NUM> of a ninth embodiment shown in <FIG> includes a plurality of refrigerant circuits 10a and 10b and a plurality of water circuits 20a and 20b. The refrigerant circuit 10a and the water circuit 20a share a water heat exchanger 30a. The refrigerant circuit 10b and the water circuit 20a share a water heat exchanger 30b. The refrigerant circuit 10b and the water circuit 20b share a water heat exchanger 30c.

The refrigerant circuit 10a shown on an upper side of <FIG> is the same as the refrigerant circuit <NUM> of the modification of the third embodiment shown in <FIG>. To be specific, in the refrigerant circuit <NUM>, a compressor 11a, a first condenser 13a-<NUM> serving as a heat-radiator 12a, a second condenser 13a-<NUM>, an expansion valve 14a, and an evaporator 15a are sequentially connected to each other by a refrigerant pipe.

The refrigerant circuit 10b shown on a lower side in <FIG> includes a compressor 11b, a first condenser 13b-<NUM> serving as a heat radiator 12b, a second condenser 13b-<NUM>, an expansion valve 14b, and an evaporator 15b. In the refrigerant circuit 10b, the compressor 11b, the first condenser 13b-<NUM> serving as the heat radiator 12b, the second condenser 13b-<NUM>, the expansion valve 14b, and the evaporator 15b are sequentially connected to each other by a refrigerant pipe.

The water circuit 20a shown on the upper side of <FIG> is the same as the water circuit <NUM> of the third embodiment shown in <FIG>. To be specific, in the water circuit 20a, a circulation pump <NUM>, a first heat absorber 22a-<NUM>, a second heat absorber 22a-<NUM>, and a hot water storage tank 23a are sequentially connected to each other by a water pipe. The hot water storage tank 23a stores high-temperature water.

The water circuit 20b shown on the lower side of <FIG> is the same as the water circuit <NUM> of the first embodiment shown in <FIG>. To be specific, in the water circuit 20b, a circulation pump <NUM>, a heat absorber 22b, and a hot water storage tank 23b are sequentially connected to each other by a water pipe. The hot water storage tank 23b stores intermediate-temperature water.

The water heat exchanger 30a on the upper side of <FIG> constitutes the first heat-exchanging unit <NUM> in relation to the water heat exchanger 30b at the center. When the water heat exchanger 30a is seen as a single water heat exchanger, the water heat exchanger 30a includes the first heat-exchanging unit <NUM> in which the second condenser 13a-<NUM> and a water outlet portion <NUM> exchange heat with each other and the second heat-exchanging unit <NUM> in which the first condenser 13a-<NUM> and a water inlet portion <NUM> exchange heat with each other.

The water heat exchanger 30b at the center of <FIG> constitutes the second heat-exchanging unit <NUM> in relation to the water heat exchanger 30a. Further, in relation to the water heat exchanger 30c on the lower side of <FIG>, the water heat exchanger 30b constitutes the second heat-exchanging unit <NUM>.

The water heat exchanger 30c on the lower side of <FIG> constitutes the first heat-exchanging unit <NUM> in relation to the water heat exchanger 30b.

At the refrigerant circuit 10a, a refrigerant discharged from the compressor 11a flows into the second heat-exchanging unit <NUM> of the water heat exchanger 30a, serving as the heat radiator 12a, via a first refrigerant pipe 16a. At the second heat-exchanging unit <NUM> of the water heat exchanger 30a, in the first condenser 13a-<NUM>, serving as the heat radiator 12a, heat of the refrigerant discharged from the compressor 11a is radiated to water in the water circuit 20a. The refrigerant whose temperature has been reduced due to heat being radiated at the heat radiator 12a flows into the first heat-exchanging unit <NUM> of the water heat exchanger 30a via a second refrigerant pipe 17a. At the first heat-exchanging unit <NUM>, in the second condenser 13a-<NUM>, heat is radiated to water at the water circuit 20a and the refrigerant is condensed. After the refrigerant condensed at the first and second condensers 13a has expanded at the expansion valve <NUM>, the refrigerant flows into the evaporator <NUM> via the third refrigerant pipe 18a.

At the refrigerant circuit 10b, the refrigerant discharged from the compressor 11b flows into the water heat exchanger 30b, serving as the heat radiator 12b, via a first refrigerant pipe 16b. The water heat exchanger 30b is the second heat-exchanging unit <NUM>, and, at the first condenser 13b-<NUM> of the water heat exchanger 30b, heat of the refrigerant discharged from the compressor 11a is radiated to water in the water circuit 20a. The refrigerant whose temperature has been reduced due to heat being radiated at the heat radiator 12b flows into the water heat exchanger 30c via a second refrigerant pipe 17b. The water heat exchanger 30c is the first heat-exchanging unit <NUM>, and, at the second condenser 13b-<NUM> of the water heat exchanger 30c, heat is radiated to water in the water circuit 20b and the refrigerant is condensed. After the refrigerant that has been condensed at the first and second condensers 13b has expanded at the expansion valve 14b, the refrigerant flows into the evaporator 15b via a third refrigerant pipe 18b.

In the water circuit 20a, water in the hot water storage tank 23a flows into the water heat exchanger 30b by a circulation pump 21a. The water heat exchanger 30b is the second heat-exchanging unit <NUM>, and in the first heat absorber 22a-<NUM>, water in the water circuit 20a is heated by the heat radiator 12b due to heat being absorbed from the refrigerant. The water heated at the heat radiator 12b flows into the water heat exchanger 30a. At the water heat exchanger 30a, water is heated by further absorbing heat from the refrigerant at the second heat-exchanging unit <NUM> and the second heat absorber 22a-<NUM> of the first heat-exchanging unit <NUM>. The high-temperature water produced by the heating returns to the hot water storage tank <NUM>.

In the water circuit 20b, water in the hot water storage tank 23b flows into the second heat-exchanging unit <NUM> of the water heat exchanger 30c by a circulation pump 21b. At the first heat-exchanging unit <NUM> of the water heat exchanger 30c, water in the water circuit 20b is heated by absorbing heat from the refrigerant that has radiated heat at the water heat exchanger 30b, serving as the heat radiator 12b. The intermediate-temperature water produced by the heating returns to the hot water storage tank <NUM>.

The water heating system <NUM> of the present embodiment includes a plurality of evaporators <NUM>. Here, each evaporator <NUM> is an outdoor unit. In this way, the water heating system <NUM> of the present invention can also be applied to a system including a plurality of outdoor units.

Claim 1:
A water heating system (<NUM> to <NUM>) comprising:
a refrigerant circuit (<NUM>) that has a compressor (<NUM>) and in which a refrigerant flows; and
a water circuit (<NUM>) in which water flows,
wherein the refrigerant circuit and the water circuit share a water heat exchanger (<NUM>) that heats water by using the refrigerant discharged from the compressor,
wherein the water heat exchanger includes a first heat-exchanging unit (<NUM>) in which the refrigerant and water at a water outlet portion (<NUM>) of the water heat exchanger exchange heat with each other, and
wherein the refrigerant circuit further has a heat radiator (<NUM>) that is disposed between the compressor and the first heat-exchanging unit characterized in that the heat radiator (<NUM>) is configured to radiate heat of the refrigerant discharged from the compressor to water that flows on an upstream side of the water outlet portion.