KR101117032B1 - Heat pump system having cascade heat exchange - Google Patents

Abstract

The present invention relates to a heat pump system having a cascade heat exchanger. A first compressor for compressing the first refrigerant, a cascade heat exchanger for condensing the first refrigerant compressed by the first compressor, a first expansion device for expanding the first refrigerant through the cascade heat exchanger and the first expansion device A first cycle having a heat source side heat exchanger for exchanging a first refrigerant with an external heat source; A second compressor for compressing a second refrigerant, a load side heat exchanger for exchanging the second refrigerant compressed by the second compressor with a load side secondary fluid flowing through the load, and a second expansion device for expanding the second refrigerant passing through the load side heat exchanger And a cascade heat exchanger configured to heat-exchange the second refrigerant having passed through the second expansion device with the first refrigerant; A load side secondary fluid line installed such that the load side secondary fluid passes through the load side heat exchanger; A first refrigerant flowing between the first compressor and the cascade heat exchanger in the first cycle, and an auxiliary heat exchanger for heat exchange between the second refrigerant flowing between the load side heat exchanger and the second expansion device in the second cycle; It is characterized by. By such a configuration, it is possible to efficiently provide hot water at a higher temperature, and the system can be stably operated.

Description

Heat pump system having cascade heat exchanger

The present invention relates to a heat pump system that provides hot water generated through a refrigerant cycle to heat a building or to be used for hot water supply in a kitchen or a bathroom. More particularly, the present invention relates to a heat pump system having a cascade heat exchanger capable of efficiently operating hot water at a higher temperature and stably operating the heat pump system.

1 is a view showing a heat pump system having a conventional cascade heat exchanger for providing heating and hot water for use in a kitchen or bathroom. 1 is a heat pump system, but since the present invention is applied to heating, the refrigerant circulation during cooling and a related configuration are omitted. This is also the same in the drawings illustrating the present invention.

The conventional heat pump system of FIG. 1 has a first cycle 10 on the low temperature side and a second cycle 20 on the high temperature side, and the first cycle 10 and the second cycle 20 are cascade heat exchangers. Heat exchange with each other at (30).

Specifically, in the first cycle 10, the first refrigerant circulates through the first compressor 11, the cascade heat exchanger 30, the first expansion device 13, and the heat source side heat exchanger 14. At this time, the cascade heat exchanger 30 functions as a condenser condensing the first refrigerant. The heat source side heat exchanger 14 acts as an evaporator in which the first refrigerant and the heat source are heat-exchanged to evaporate the first refrigerant. At this time, ambient air, geothermal heat, seawater heat, and the like can be used as the heat source.

In the second cycle 20, the second refrigerant circulates through the second compressor 21, the load side heat exchanger 22, the second expansion device 23, and the cascade heat exchanger 30. At this time, the cascade heat exchanger 30 in the second cycle 20 serves as an evaporator for evaporating the second refrigerant. In the second cycle, the load-side heat exchanger 22 performs heat exchange with the load-side secondary fluid (for example, water) used for heating and water supply, and functions as a condenser in which the second refrigerant is condensed. The load side secondary fluid which has become hot due to the heat exchange while passing through the load side heat exchanger 22 is supplied to the storage heat storage tank 40 or directly supplied to the load side while circulating the load side secondary fluid line L50. When stored in the heat storage tank 40, the load-side secondary fluid is supplied to the load side such as the kitchen or the bathroom again through the heating pipe or the hot water supply pipe.

In the heat pump system including the cascade heat exchanger, the first refrigerant compressed to the high temperature and high pressure state in the first compressor 11 of the first cycle 10 is the second cycle of the second cycle 20 in the cascade heat exchanger 30. By heat-exchanging with a refrigerant, the temperature of the second refrigerant flowing into the second compressor 21 in the second cycle 20 can be made high. The second refrigerant, which has become such a high temperature, may be compressed again by the second compressor 21 of the second cycle 20 to increase the temperature of the second refrigerant, and the second refrigerant compressed by the second compressor 21 may be The temperature of the load side secondary fluid is increased by heat exchange with the heat storage tank 40 or the load side secondary fluid circulating in the load side in the second condenser 22.

Therefore, a heat pump system having such a cascade heat exchanger can generate a load side secondary fluid (water) having a higher temperature than when using one cycle.

However, in this conventional cascade type heat pump system, since the temperature of the load side secondary fluid generated by the performance of the device constituting the first and second cycles is determined, it can be obtained by operating the first and second cycles. If the user requires a temperature higher than the temperature (higher heating temperature or higher hot water temperature is required), it will not be able to respond.

In addition, when the temperature of the heat source side secondary fluid flowing into the heat source side heat exchanger 14 is low due to the decrease in the temperature of the heat source, the temperature of the first refrigerant flowing into the cascade heat exchanger 30 of the first cycle 10 may be reduced. The temperature is lowered, which causes the temperature of the second refrigerant flowing through the load side heat exchanger 22 in the second cycle 10 to be lowered, thereby lowering the temperature of the load side secondary fluid, so that hot water at a temperature required by the consumer cannot be supplied. Cases may occur.

In addition, when the degree of subcooling of the refrigerant at the outlet of the load-side heat exchanger 22 of the second cycle 20 is small, the outlet dryness of the second expansion device 23 is increased. In this case, the inlet flows into the cascade heat exchanger 30. As the second refrigerant flow rate of the second cycle 20 increases, the uniformity of the refrigerant distribution in the cascade heat exchanger 30 decreases, so that the refrigerant circulation flow rate decreases and the heat pump system performance decreases due to the decrease in the heat exchange performance of the cascade heat exchanger 30. Since a fall occurs, it is necessary to ensure adequately the outlet subcooling degree of the load side heat exchanger 22 of the second cycle 20.

The present invention is to solve the problem of the conventional heat pump system having a cascade heat exchanger, cascade heat exchange that can generate a load-side secondary fluid of a higher temperature when hot water is generated only by heat exchange in the cascade heat exchanger An object of the present invention is to provide a heat pump system having a machine.

In addition, an object of the present invention is to make it possible to stably operate the second cycle on the high temperature side by increasing the subcooling degree of the second refrigerant entering the expansion device in the second cycle on the high temperature side.

Heat pump system having a cascade heat exchanger according to the present invention for achieving the above object. A first compressor for compressing the first refrigerant, a cascade heat exchanger for condensing the first refrigerant compressed by the first compressor, a first expansion device for expanding the first refrigerant through the cascade heat exchanger and the first expansion device A first cycle having a heat source side heat exchanger for exchanging a first refrigerant with an external heat source; A second compressor for compressing a second refrigerant, a load side heat exchanger for exchanging the second refrigerant compressed by the second compressor with a load side secondary fluid, a second expansion device for expanding the second refrigerant passing through the load side heat exchanger, and the A second cycle comprising the cascade heat exchanger for exchanging a second refrigerant having passed through a second expansion device with the first refrigerant; A load side secondary fluid line installed such that the load side secondary fluid passes through the load side heat exchanger; A first refrigerant flowing between the first compressor and the cascade heat exchanger in the first cycle, and an auxiliary heat exchanger for heat exchange between the second refrigerant flowing between the load side heat exchanger and the second expansion device in the second cycle; It is characterized by.

In addition, the heat pump system having a cascade heat exchanger according to the present invention is characterized in that the first refrigerant from the first compressor in the first cycle is selectively supplied to the auxiliary heat exchanger.

In addition, the heat pump system having a cascade heat exchanger according to the present invention is characterized in that the second refrigerant from the load side heat exchanger in the second cycle is selectively supplied to the auxiliary heat exchanger.

In addition, the control method for controlling a heat pump system having a cascade heat exchanger according to the present invention having the above configuration, operating the first and second cycles, the first of the first cycle compressed in the first compressor The refrigerant passes through the auxiliary heat exchanger to exchange heat with the second refrigerant passing through the load side heat exchanger in the second cycle, and the first refrigerant passing through the auxiliary heat exchanger is the second refrigerant of the second cycle in the cascade heat exchanger. And to heat exchange with.

According to the present invention having the above configuration, the first refrigerant passing through the compressor in the first cycle and the second refrigerant passing through the load side heat exchanger in the second cycle are heat exchanged through the auxiliary heat exchanger to exchange heat with the secondary fluid of the load side in the load side heat exchanger. The temperature of the second refrigerant can be raised, and as a result, hot water at a higher temperature can be provided to produce hot water corresponding to a temperature required by the consumer.

In addition, the present invention increases the subcooling of the second refrigerant flowing into the second expansion device in the second cycle to enable the heat pump system to operate stably.

1 shows a heating system with a conventional cascade heat exchanger providing heating and hot water for use in a kitchen or bathroom.
2 is a view showing a first embodiment of a heat pump system having a cascade heat exchanger according to the present invention.
3 is a view showing a case where an auxiliary heat exchanger is not used in the second embodiment of a heat pump system having a cascade heat exchanger according to the present invention.
4 is a pressure-enthalpy diagram for the first and second cycles of a heat pump system with a cascade heat exchanger according to the present invention.
5 is a view showing a second embodiment of a heat pump system having a cascade heat exchanger according to the present invention.
6 is a view showing a third embodiment of a heat pump system having a cascade heat exchanger according to the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of a heat pump system having a cascade heat exchanger according to the present invention.

<First Embodiment>

First, as shown in FIG. 2, a heat pump system having a cascade heat exchanger according to the present invention is a first cycle 100, which is a low temperature side cycle in which a first refrigerant circulates, and a high temperature side cycle in which a second refrigerant circulates. The second cycle 200 is provided.

First, the first cycle 100 includes a first refrigerant line L100 through which the first refrigerant circulates, and the first compressor 110, the cascade heat exchanger 300, and the first expansion through the first refrigerant line. Apparatus 130 and heat source side heat exchanger 140. The first compressor 110 compresses the first refrigerant and sends the first refrigerant to the cascade heat exchanger 300. In the cascade heat exchanger 300, the first refrigerant exchanges heat with the second refrigerant circulating in the second cycle 200, which will be described later, to deprive heat, and the first expansion device 130 expands the first refrigerant, The side heat exchanger 140 exchanges the expanded first refrigerant with the heat source.

The first refrigerant flowing through the cascade heat exchanger 300 in the first cycle 100 loses heat to the second refrigerant during heat exchange with the second refrigerant flowing through the cascade heat exchanger 300 in the second cycle 200. do. Accordingly, in the first cycle 100, the cascade heat exchanger 300 acts as a condenser.

In addition, the first refrigerant flowing through the heat source side heat exchanger 140 in the first cycle 100 is evaporated by receiving heat from the heat source while exchanging heat with the heat source. Therefore, in the first cycle 100, the heat source side heat exchanger 140 acts as an evaporator. Here, as the heat source, ambient air, geothermal heat, seawater heat and the like may be used. When geothermal or seawater heat is used as the heat source, the heat source side secondary fluid may be configured to circulate the heat source and the heat source side heat exchanger 140. FIG. 2 is a heat source side secondary fluid through which the heat source side secondary fluid circulates. The form in which the line L600 is installed is shown.

In addition, the first cycle 100 is a point (point A) of the first refrigerant line (L100) of the outlet of the first compressor 110 (specifically, between the first compressor 110 and the cascade heat exchanger 300). The first refrigerant branch line (L110) branching from the. The first refrigerant branch line L110 branches at the point A and passes through the auxiliary heat exchanger 400, and then merges with the first refrigerant line L100 at the inlet of the cascade heat exchanger 300.

In addition, control valves A1 and A2 are respectively provided at the first refrigerant branch line L110 between the point A and the auxiliary heat exchanger 400 and the first refrigerant line L100 between the point A and the cascade heat exchanger 300. It is installed. The control valves A1 and A2 are selectively operated to allow the first refrigerant from the first compressor 110 to selectively pass through the auxiliary heat exchanger 400 or the cascade heat exchanger 300.

As used herein, " optional " means that the control valve A2 of the first refrigerant line L100 is opened while the first refrigerant flows to the first refrigerant branch line L110 by alternately opening the control valves A1 and A2. Not only does not flow to the installed line, or conversely, the first refrigerant does not flow to the first refrigerant branch line (L110) while flowing to the line where the control valve (A2) of the first refrigerant line (L100) is installed, By adjusting the opening degree of the valve (A1, A2) includes the case where the first refrigerant flows together to the line and the first refrigerant branch line (L110) and the control valve A2 is installed in the first refrigerant line (L100). In addition, the control valve (A1, A2) is used for the flow rate control valve, it is possible to adjust the flow rate of the secondary side fluid load. The same applies to the control valves B1 and B2 described below.

In the auxiliary heat exchanger 400, the first refrigerant exchanges heat with the second refrigerant of the second cycle 200, which will be described later. That is, in the present invention, the first refrigerant of the first cycle 100 and the second refrigerant of the second cycle 200 exchange heat in the cascade heat exchanger 300 and the auxiliary heat exchanger 400.

Next, the second cycle 200 includes a second compressor 210, a load side heat exchanger 220, a second expansion device 230, and a cascade heat exchanger 300, these configurations in which the second refrigerant flows. It is connected by the second refrigerant line (L200). The second refrigerant is compressed by the second compressor 210, heat exchanges with the load-side secondary fluid which will be described later in the load-side heat exchanger 220, expands through the second expansion device 230, and the cascade heat exchanger 300 Heat exchange with the first refrigerant flowing through the first cycle 100 while passing through) is introduced into the second compressor 210 again.

In the second cycle 200, the second refrigerant flowing through the load-side heat exchanger 220 loses heat while condensing with the load-side secondary fluid. Thus, in the second cycle 200, the load side heat exchanger 220 acts as a condenser. On the contrary, the temperature of the load-side secondary fluid supplied with heat by heat exchange in the load-side heat exchanger 220 increases.

In addition, the second refrigerant flowing through the cascade heat exchanger 300 in the second cycle 200 receives heat from the first refrigerant while performing heat exchange with the first refrigerant flowing through the cascade heat exchanger 300 in the first cycle 100. Will evaporate. Thus, in the second cycle 200 the cascade heat exchanger 300 acts as an evaporator.

 In addition, the second cycle 200 is a point B of the second refrigerant line L200 of the outlet of the load-side heat exchanger 220 (specifically, between the load-side heat exchanger 220 and the second expansion device 230). And a second refrigerant branch line (L210) branching at the point). The second refrigerant branch line L210 branches at the point B, passes through the auxiliary heat exchanger 400, and then merges with the second refrigerant line L200 at the inlet of the second expansion device 230.

In addition, control valves B1 and B2 are provided at the first refrigerant branch line L110 between the point B and the auxiliary heat exchanger 400 and the second refrigerant line L200 between the point B and the second expansion device 230. Each is installed. The control valves B1 and B2 are selectively operated to allow the second refrigerant from the load side heat exchanger 220 to selectively pass through the auxiliary heat exchanger 400 or the second expansion device 230.

In addition, the heat pump system having a cascade heat exchanger according to the present invention includes a heat storage tank 500 for storing the load-side secondary fluid, and between the load-side heat exchanger 220 and the heat storage tank of the second cycle 200. And a load side secondary fluid line (L500) configured to circulate the load side secondary fluid. In addition, the load side secondary fluid line (L500) is provided with a pump 510 for circulating the load side secondary fluid. In this embodiment, the load side secondary fluid uses water or the like.

The heat storage tank 500 is connected to a heating line (L510) connected to the load-side secondary fluid to circulate the floor or fan coil unit, etc., and a hot water supply line (L520) for supplying hot water to the kitchen or bathroom. . In the present embodiment, the heat storage tank 500 is provided, but in some cases, the heat storage tank may not be provided. In this case, the heating line 510 and the hot water supply line L520 are directly loaded to the secondary fluid line L500. ) Can be connected.

In addition, the load side secondary fluid line (L500) is provided with a supplementary water line (L530) that can supply the load side secondary fluid (water) from the outside. Replenishment water line (L530) is for replenishing the load-side secondary fluid is supplied to the kitchen or bathroom through the hot water supply line (L520). Supplement water line (L530) may be installed in the heat storage tank (500). And the replenishment water line (L530) is provided with a control valve (E1) for adjusting the flow rate of the replenishment water.

Hereinafter, the operation of the first embodiment of the heat pump system having the cascade heat exchanger according to the present embodiment having such a configuration will be described with reference to FIGS. 2 to 4. First, a case in which the first refrigerant of the first cycle 100 and the second refrigerant of the second cycle 200 performs heat exchange in the cascade heat exchanger 300 will be described with reference to FIG. 3. In this case, even though the first cycle 100 and the second cycle 200 are operated in a conventional manner, a load-side secondary fluid of sufficient temperature for heating and water supply can be generated, so that heat exchange does not occur in the auxiliary heat exchanger 400. Do not.

To this end, as shown in FIG. 3, the control valve A1 of the first cycle 100 is closed and the control valve A2 is opened, and the control valve B1 of the second cycle 200 is closed. Open the control valve (B2). When the first cycle 100 and the second cycle 200 are operated in this state, the first refrigerant of the first cycle 100 is in the state of a1-b1-c1-d1 shown in solid lines in the lower part of FIG. 4. The second refrigerant of the second cycle 200 undergoes a state change of a2-b2-c2-d2 shown in solid lines at the top of FIG. 4 while circulating the second cycle.

First, the first refrigerant is compressed by the first compressor 110 and becomes a b1 state from an a1 state. The first refrigerant in the b1 state exchanges heat with the second refrigerant in the cascade heat exchanger 300, thereby depriving heat of the first refrigerant, thereby becoming a c1 state. At this time, the temperature of the first refrigerant is TH1. The first refrigerant in the c1 state is in a state of d1 via the first expansion device 130. The first refrigerant in the d1 state is supplied with heat from the heat source-side heat exchanger 140 by heat exchange with the heat source to be in the a1 state (the temperature of the first refrigerant is referred to as TL1), and then the first compressor 110 is transferred to the first compressor 110. It goes through the incoming cycle.

The second refrigerant of the second cycle 200 passes through the cascade heat exchanger 300 and enters the second compressor 210 by being in the a2 state of the temperature TL2 by heat exchange in the d2 state. The temperature TL2 is less than the temperature TH1 of the first refrigerant passing through the cascade heat exchanger 300. When the second refrigerant is compressed by the second compressor 210, the second refrigerant is changed from the a2 state to the b2 state. At this time, the temperature of the second refrigerant is TH2. Thereafter, the second refrigerant undergoes heat exchange with the secondary fluid of the load side while passing through the load-side heat exchanger 220, thereby depriving heat, and thus the c2 state. ) After that, the second refrigerant enters the cascade heat exchanger 300 in the state of d2 while passing through the expansion device 230.

By the operation of the first cycle 100 and the second cycle 200 it is possible to generate a high-temperature load side secondary fluid for heating and water supply. However, when operating as shown in FIG. 3, when a load side secondary fluid having a higher temperature than that obtained by the operation of the first cycle and the second cycle is required or when the heat source side secondary fluid temperature decreases, TH1 Due to this decrease, when the temperature of the load side secondary fluid generated by the load side decreases due to the decrease of TL2 and TH2, it is impossible to obtain hot water at the temperature required by the consumer.

Therefore, when a load side secondary fluid having a higher temperature than that obtained by the operation of the first cycle and the second cycle is required and the heat source side secondary fluid temperature is lowered, as shown in FIG. At 400 the heat exchange is operated to occur.

Specifically, as shown in FIG. 2, the control valves A1 and A2 are opened in the first cycle 100, and the control valves B1 and B2 are opened in the second cycle 200. As a result, some of the first refrigerant compressed through the first compressor 110 in the first cycle 100 flows along the first refrigerant line L100 and flows into the cascade heat exchanger 300, and a part of the first refrigerant flows through the first refrigerant line L100. Along the branch line (L110) flows through the auxiliary heat exchanger 400 and the first refrigerant flowing through the first refrigerant line (L100) again flows into the cascade heat exchanger (300). In addition, the first refrigerant passing through the cascade heat exchanger 300 flows back into the first compressor 110 through the first expansion device 130 and the heat source side heat exchanger 140.

That is, the first refrigerant circulating in the first cycle 100 is initially changed to the state of a1-b1-c1-d1 shown in solid lines at the bottom of FIG. 4.

Meanwhile, in the second cycle 200, the second refrigerant is also initially subjected to a state change of a2-b2-c2-d2 shown by a solid line at the top of FIG. 4, but among the second refrigerants that have passed through the load-side heat exchanger 220. Some flow into the auxiliary heat exchanger 400 to exchange heat with the first refrigerant. At this time, the temperature of the second refrigerant is a temperature of the c2 state in FIG. 4, higher than the temperature of the b1 state of the first refrigerant. Therefore, the heat is transferred from the second refrigerant to the first refrigerant in the auxiliary heat exchanger 400 to increase the temperature of the first refrigerant. The first refrigerant having the elevated temperature is introduced into the cascade heat exchanger 400 by being combined with the first refrigerant which has not passed through the auxiliary heat exchanger 400. As a result, the first refrigerant flowing into the cascade heat exchanger 400 in the first cycle 100 is in the b1 'state, and after the heat exchange is performed in the cascade heat exchanger 400, the first refrigerant is in the c1' state. At this time, the temperature of the first refrigerant to be heat-exchanged in the cascade heat exchanger 400 is TH1 'indicated by a dotted line in FIG. 4, which is higher than the temperature TH1 when the auxiliary heat exchanger 400 is not used.

As shown by a dotted line in FIG. 4, the first refrigerant that has risen to the temperature TH1 ′ and the second refrigerant that heat exchanges in the cascade heat exchanger 300 are compared with TL2 which is a temperature when the auxiliary heat exchanger 400 is not used. It becomes high TL2 'temperature. The second refrigerant passing through the cascade heat exchanger 300 is in the state of a2 ', and is then compressed in the second compressor 210 to the state of b2', so that the load side heat exchanger 220 exchanges heat with the load side secondary fluid. do. At this time, the temperature of the second refrigerant that heat exchanges with the load-side secondary fluid will be TH2 'in FIG. 4, which is higher than the temperature TH2 when the auxiliary heat exchanger 400 is not used. Therefore, the load-side secondary fluid that exchanges heat with the temperature of TH2 'is higher than the temperature when the auxiliary heat exchanger 400 is not used, and as a result, a load-side secondary fluid having a higher temperature can be generated.

In addition, the second refrigerant passing through the load-side heat exchanger 220 in the second cycle 200 passes through the auxiliary heat exchanger 400 and then passes through the expansion device 230 and the cascade heat exchanger 300. The state of the second refrigerant circulating in the second cycle 200 passes through a2'-b2'-c2'-d2 'as shown by a dotted line in FIG.

In this embodiment, the temperature of the secondary fluid of the load side or the temperature of the first refrigerant flowing into the cascade heat exchanger 300 in the first cycle 100 is measured and compared with the temperature required for heating and hot water supply, and then adjusted. By adjusting the openings of the valves A1 and A2 and the control valves B1 and B2, the flow rate of the first refrigerant and the second refrigerant exchanged in the subsidiary heat exchanger 400 is adjusted, so that Can be controlled to meet the required temperature.

On the other hand, the state of c2 'as shown in Figure 4 is to lose more heat through the auxiliary heat exchanger 400, from the saturation state to the left side than the c2 state when not using the auxiliary heat exchanger 400 More biased. That is, the subcooling degree C is deprived of heat from the subsidiary heat exchanger 400 so that the subcooling degree C 'is increased than the subcooling degree C when the subsidiary heat exchanger 400 is not used.

When the second cycle 200 increases in the subcooling degree C ′, the second refrigerant flowing into the second expansion device 230 may be prevented from vaporizing due to the resistance of the pipe and becoming a gas. By maintaining the liquid state, the second cycle 200 can be stably operated by increasing the flow rate of the second refrigerant circulating through the second cycle 200.

<2nd embodiment>

Referring to FIG. 5, in the second embodiment, in the first embodiment, the second cycle 200 does not include the second refrigerant branch line L210 and the control valves B1 and B2. Specifically, in the second embodiment, the second refrigerant line L200 is connected to the auxiliary heat exchanger 400 in an open state so that the second refrigerant always passes through the auxiliary heat exchanger 400.

At this time, by controlling the opening and closing of the control valves A1 and A2 in the first cycle 100, the same effects as in the first embodiment are obtained. Specifically, when the control valve A1 is closed, even though the second refrigerant always passes through the auxiliary heat exchanger 400, since the first refrigerant does not pass through the auxiliary heat exchanger 400, the first refrigerant and the second refrigerant are separated from each other. If the heat exchange is not performed, and the opening of the control valve A1 or the opening degree is adjusted in the open state, the first and second refrigerants may be heat-exchanged in the auxiliary heat exchanger 400. The amount of heat exchange can be controlled.

Third Embodiment

Referring to FIG. 6, in the third embodiment, in the first embodiment, the first cycle 100 does not include the first refrigerant branch line L110 and the control valves A1 and A2. Specifically, in the third embodiment, the first refrigerant line L100 is connected to the auxiliary heat exchanger 400 in an open state so that the first refrigerant always passes through the auxiliary heat exchanger 400.

At this time, by controlling the opening and closing of the control valve (B1, B2) in the second cycle 200 has the same effect as in the first embodiment. Specifically, when the control valve B1 is closed, even though the first refrigerant always passes through the subsidiary heat exchanger 400, the second refrigerant does not pass through the subsidiary heat exchanger 400 between the first refrigerant and the second refrigerant. If the heat exchange is not performed, and the opening of the control valve B1 or the opening degree is adjusted in the open state, the first and second refrigerants may be heat-exchanged in the auxiliary heat exchanger 400. The amount of heat exchange can be controlled.

As described above, the heat pump for hot water supply according to the present invention has been described with reference to the preferred embodiments, but the present invention is not limited to these embodiments, and should be understood by those skilled in the art. Various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as set forth in the claims.

100: first cycle 110: first compressor
130: first expansion device 140: heat source side heat exchanger
200: second cycle 210: second compressor
220: load side heat exchanger 230: second expansion device
300: cascade heat exchanger 400: auxiliary heat exchanger
500: heat storage tank L100: first refrigerant line
L110: First refrigerant branch line L200: Second refrigerant line
L210: Second refrigerant branch line L500: Load side secondary fluid line
L600: Heat source side secondary fluid line
A1, A2, B1, B2: Control Valve

Claims (4)

A first compressor for compressing the first refrigerant, a cascade heat exchanger for condensing the first refrigerant compressed by the first compressor, a first expansion device for expanding the first refrigerant through the cascade heat exchanger and the first expansion device A first cycle comprising a heat source side heat exchanger for exchanging a first refrigerant with an external heat source,
A second compressor for compressing a second refrigerant, a load side heat exchanger for exchanging the second refrigerant compressed by the second compressor with a load side secondary fluid flowing through the load, and a second expansion device for expanding the second refrigerant passing through the load side heat exchanger And a second cycle including the cascade heat exchanger for exchanging a second refrigerant having passed through the second expansion device with the first refrigerant;
A load side secondary fluid line installed such that the load side secondary fluid passes through the load side heat exchanger;
A first refrigerant flowing between the first compressor and the cascade heat exchanger in the first cycle, and an auxiliary heat exchanger for heat exchange between the second refrigerant flowing between the load side heat exchanger and the second expansion device in the second cycle; Heat pump system having a cascade heat exchanger, characterized in that. The method of claim 1,
And a first refrigerant from the first compressor in the first cycle is selectively supplied to the auxiliary heat exchanger. The method according to claim 1 or 2,
And a second refrigerant from the load side heat exchanger in the second cycle is selectively supplied to the auxiliary heat exchanger. A control method for controlling a heat pump system having a cascade heat exchanger according to claim 1,
Operate the first and second cycles and allow the first refrigerant of the first cycle compressed in the first compressor to exchange heat with the second refrigerant passing through the load side heat exchanger in the second cycle while passing through the auxiliary heat exchanger. And the first refrigerant passing through the auxiliary heat exchanger is heat-exchanged with the second refrigerant of the second cycle in the cascade heat exchanger.

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