JP7584305B2 - Heat pump chiller system and plate heat exchanger connection method - Google Patents

Description

This disclosure relates to a heat pump chiller system and a method for connecting a plate heat exchanger.

In a system that includes multiple heat pump chillers with plate heat exchangers, the water circuit through which water flows is generally standardized as counterflow or parallel flow between the water and refrigerant in all plate heat exchangers of any heat pump chiller, with counterflow or parallel flow being fixed for cooling operation and heating operation. Counterflow is more efficient for heat exchange between water and refrigerant. Therefore, for example, if heating operation is counterflow and cooling operation is parallel flow, the performance of cooling operation (parallel flow) will be lower than that of heating operation (counterflow).

The second embodiment of Patent Document 1 discloses a refrigerant circuit configured such that during cooling operation, the refrigerant and the heat medium flow in countercurrent flow in the first intermediate heat exchanger 211 and in parallel flow in the second intermediate heat exchanger 212, thereby weakening the cooling of the heat medium passing through the second intermediate heat exchanger 212.

JP 2017-101855 A

There is a need for a heat pump chiller system that is not biased in terms of high performance in either cooling or heating operation and low performance in the other.

Therefore, the present disclosure aims to provide a heat pump chiller system and a method for connecting plate heat exchangers that can solve the above-mentioned problems.

According to one aspect of the present disclosure, a heat pump chiller system includes a first heat pump chiller including a first plate heat exchanger that performs heat exchange between a heat medium supplied to a load and a first refrigerant, a second heat pump chiller including a second plate heat exchanger that performs heat exchange between the heat medium and a second refrigerant, a third heat pump chiller including a third plate heat exchanger that performs heat exchange between the heat medium and a third refrigerant, a fourth heat pump chiller including a fourth plate heat exchanger that performs heat exchange between the heat medium and a fourth refrigerant, and a connecting flow path connecting the third plate type heat exchanger and the fourth plate type heat exchanger, and a switching mechanism for switching between the third plate type heat exchanger and the fourth plate type heat exchanger to supply the heat medium, wherein when the flow directions of the heat medium and the first refrigerant in the first plate type heat exchanger are counter-current to each other, the flow directions of the heat medium and the second refrigerant in the second plate type heat exchanger are parallel to each other, and when the flow directions of the heat medium and the second refrigerant in the second plate type heat exchanger are counter-current to each other, a flow path for the heat medium is provided such that the flow directions of the heat medium and the first refrigerant in the first plate heat exchanger are parallel to each other when the flow direction of the third refrigerant in the third plate heat exchanger and the flow direction of the fourth refrigerant in the fourth plate heat exchanger are both from top to bottom, the connecting flow path is provided such that the flow of the heat medium in both the third plate heat exchanger and the fourth plate heat exchanger is from bottom to top when the flow direction of the third refrigerant in the third plate heat exchanger and the flow direction of the fourth refrigerant in the fourth plate heat exchanger are both from top to bottom, The heat medium is supplied to the third plate type heat exchanger so as to flow from the third plate type heat exchanger to the fourth plate type heat exchanger in that order, and when the flow direction of the third refrigerant in the third plate type heat exchanger and the flow direction of the fourth refrigerant in the fourth plate type heat exchanger are both switched from bottom to top, the heat medium is supplied to the fourth plate type heat exchanger by control of the switching mechanism so as to flow from the fourth plate type heat exchanger to the third plate type heat exchanger in that order.

According to one aspect of the present disclosure, there is provided a first heat pump chiller including a first plate heat exchanger that performs heat exchange between a heat medium supplied to a load and a first refrigerant, a second heat pump chiller including a second plate heat exchanger that performs heat exchange between the heat medium and a second refrigerant, a third heat pump chiller including a third plate heat exchanger that performs heat exchange between the heat medium and a third refrigerant, a fourth heat pump chiller including a fourth plate heat exchanger that performs heat exchange between the heat medium and a fourth refrigerant, and a heat pump chiller including a second plate heat exchanger that performs heat exchange between the heat medium and a fourth refrigerant. a switching mechanism for switching to either the third plate heat exchanger or the fourth plate heat exchanger to supply the heat medium, wherein when the flow directions of the heat medium and the first refrigerant in the first plate heat exchanger are counter-current to each other , the flow directions of the heat medium and the second refrigerant in the second plate heat exchanger are parallel to each other, and when the flow directions of the heat medium and the second refrigerant in the second plate heat exchanger are counter-current to each other, the flow directions of the heat medium and the second refrigerant in the first plate heat exchanger are parallel to each other. the first plate heat exchanger and the second plate heat exchanger are connected so that the flow directions of the heat medium and the first refrigerant are parallel to each other ; when the flow direction of the third refrigerant in the third plate heat exchanger and the flow direction of the fourth refrigerant in the fourth plate heat exchanger are both from top to bottom, the connecting flow paths are provided so that the flow of the heat medium in both the third plate heat exchanger and the fourth plate heat exchanger is from bottom to top; and the switching mechanism is controlled to switch the heat medium between the third plate heat exchanger and the fourth plate heat exchanger. and when a flow direction of the third refrigerant in the third plate type heat exchanger and a flow direction of the fourth refrigerant in the fourth plate type heat exchanger are both switched from bottom to top, the heat medium is supplied to the fourth plate type heat exchanger under the control of the switching mechanism so that the heat medium flows from the fourth plate type heat exchanger to the third plate type heat exchanger .

The heat pump chiller system and plate heat exchanger connection method disclosed herein can prevent performance degradation during either cooling or heating operation.

1 is a diagram illustrating an example of a heat pump chiller system according to a first embodiment. FIG. 1 is a schematic diagram of a typical plate heat exchanger. FIG. 2 is a diagram showing connections of the plate heat exchanger according to the first embodiment. FIG. 1 is a first diagram showing an example of settings and operations of the heat pump chiller system according to the first embodiment. FIG. 2 is a second diagram showing an example of settings and operations of the heat pump chiller system according to the first embodiment. FIG. 1 is a first diagram showing connections of a plate heat exchanger according to a second embodiment. FIG. 2 is a second diagram showing the connection of the plate heat exchanger according to the second embodiment. FIG. 11 is a diagram illustrating an example of a heat pump chiller system according to a third embodiment. FIG. 11 is a diagram showing the relationship between the flows of water and a refrigerant according to the third embodiment. FIG. 1 is a diagram showing the connections of a typical plate heat exchanger.

The heat pump chiller system according to each embodiment will be described below with reference to Figures 1 to 8.

First Embodiment
(Configuration of heat pump chiller system)
FIG. 1 is a diagram illustrating an example of a heat pump chiller system according to an embodiment.
The heat pump chiller system 100 includes a heat pump chiller 1A, a heat pump chiller 1B, and a control device 10.
The heat pump chiller 1A and the heat pump chiller 1B are connected in series to the load by a pipe WL through which water flows. Water flows into the heat pump chiller 1A, is cooled or heated, and flows out of the heat pump chiller 1A. The water that flows out of the heat pump chiller 1A flows into the heat pump chiller 1B, is cooled or heated, and flows out of the heat pump chiller 1B.
The heat pump chiller 1A includes a compressor 2A, a four-way valve 3A, a heat exchanger 4A, a plate type heat exchanger 5A, an expansion valve 6A, a control device 7A, and the like.
The heat pump chiller 1B includes a compressor 2B, a four-way valve 3B, a heat exchanger 4B, a plate type heat exchanger 5B, an expansion valve 6B, a control device 7B, and the like.
The control device 10 controls the start, stop, etc. of the heat pump chillers 1A and 1B through the control devices 7A and 7B.
Hereinafter, when there is no need to distinguish between the heat pump chiller 1A and the heat pump chiller 1B, they will be referred to as the heat pump chiller 1. When there is no need to distinguish between the plate heat exchanger 5A and the plate heat exchanger 5B, they will be referred to as the plate heat exchanger 5. The same applies to other configurations.

The operation of the heat pump chiller system 100 during cooling operation will now be described. The control device 7A controls the four-way valve 3A so that the high-pressure side of the compressor 2A communicates with the heat exchanger 4A, and the low-pressure side of the compressor 2A communicates with the plate heat exchanger 5A. The control device 7A also operates the compressor 2A at a predetermined rotation speed and opens the expansion valve 6A to a predetermined opening degree based on the current water temperature and the set temperature. The control device 7B similarly controls the four-way valve 3B, the compressor 2B, and the expansion valve 6B.
Water flowing from the load side through the piping WL flows into the heat pump chiller 1A. In the heat pump chiller 1A, the compressor 2A compresses the refrigerant and discharges the high-pressure refrigerant. The high-pressure refrigerant is supplied to the heat source side heat exchanger 4A (condenser) via the four-way valve 3A, and condenses by exchanging heat with the outdoor air. This refrigerant is decompressed by the expansion valve 6A and supplied to the utilization side plate-type heat exchanger 5A (evaporator). In the plate-type heat exchanger 5A, the refrigerant absorbs heat from the water flowing through the piping WL, vaporizes, and is sucked into the compressor 2A. The compressor 2A discharges the high-pressure refrigerant, and the refrigerant circulates through the refrigerant circuit in the same manner as above. The water flowing through the piping WL is cooled by heat exchange in the plate-type heat exchanger 5A, and flows into the heat pump chiller 1B. In the heat pump chiller 1B, the refrigerant circulates in the same manner as in the heat pump chiller 1A, through the compressor 2B, heat exchanger 4B (condenser), expansion valve 6B, plate type heat exchanger 5B (evaporator), and compressor 2B in that order. Water that flows into the heat pump chiller 1B is cooled by heat exchange in the plate type heat exchanger 5B and supplied to the load. In the figure, the arrows indicate the direction of water flow.

The operation of the heat pump chiller system 100 during heating operation will now be described. As shown in Fig. 1, the control device 7A controls the four-way valve 3A so that the high-pressure side of the compressor 2A communicates with the plate heat exchanger 5A and the low-pressure side of the compressor 2A communicates with the heat exchanger 4A. The control device 7A also operates the compressor 2A at a predetermined rotation speed and opens the expansion valve 6A to a predetermined opening degree based on the current water temperature and the set temperature. The control device 7B similarly controls the four-way valve 3B, the compressor 2B, and the expansion valve 6B.
Water flowing from the load side through the piping WL flows into the heat pump chiller 1A. In the heat pump chiller 1A, the compressor 2A compresses the refrigerant and discharges the high-pressure refrigerant. The high-pressure refrigerant is supplied to the plate-type heat exchanger 5A (condenser) on the user side via the four-way valve 3A, and condenses by heat exchange with water. This refrigerant is decompressed by the expansion valve 6A and supplied to the heat exchanger 4A (evaporator) on the heat source side. The refrigerant absorbs heat from the outside air and the like in the heat exchanger 4A and vaporizes. The vaporized refrigerant is sucked into the compressor 2A. The compressor 2A discharges the high-pressure refrigerant, and the refrigerant circulates through the refrigerant circuit in the same manner as above. The water flowing through the piping WL is heated by heat exchange in the plate-type heat exchanger 5A and flows into the heat pump chiller 1B. In the heat pump chiller 1B, similarly to the heat pump chiller 1A, the refrigerant circulates through the compressor 2B, plate type heat exchanger 5B (condenser), expansion valve 6B, heat exchanger 4B (evaporator), and compressor 2B in that order. Water that flows into the heat pump chiller 1B is heated by heat exchange in the plate type heat exchanger 5B and supplied to the load.

(Configuration of plate heat exchanger)
Next, referring to FIG. 2, the structure of a general plate heat exchanger 5 will be briefly described. As shown in FIG. 2, the plate heat exchanger 5 has a first end 51 as an inlet for water and a second end 52 as an outlet for water. A pipe WL1 for introducing water is connected to the first end 51, and a pipe WL2 for discharging water is connected to the second end 52. The inlet and outlet for the refrigerant are the third end 53 and the fourth end 54. The pipe RL1 for introducing or discharging the refrigerant is connected to the third end 53, and the pipe RL2 for discharging or introducing the refrigerant is connected to the fourth end 54. The flow of the refrigerant is reversed between the cooling operation and the heating operation. In the heating operation, the refrigerant is introduced from the third end 53 and discharged from the fourth end 54, for example. In the cooling operation, the refrigerant is introduced from the fourth end 54 and discharged from the third end 53, for example.

As shown in the figure, the plate heat exchanger 5 includes a plurality of plates 55a to 55e. The plurality of plates 55a to 55e are made of a heat-conducting material and are capable of exchanging heat between both surfaces of the plates. The plurality of plates 55 are stacked at intervals from one another, so that flow paths 56a to 56d are formed between the plates 55a to 55e stacked inside the plate heat exchanger 5. For example, a flow path 56a is formed between the plates 55a and 55b, and a flow path 56b is formed between the plates 55b and 55c. The same is true for the flow paths 56c and 56d. Water and a refrigerant flow alternately through the stacked plurality of flow paths. For example, the refrigerant flows through the flow paths 56a and 56c, and the water flows through the flow paths 56b and 56d. The flow of water is indicated by solid arrows, and an example of the flow of the refrigerant is indicated by dashed arrows. In the plate heat exchanger 5, heat exchange is performed between the water and the refrigerant through the plates 55a to 55e, which are made of a heat-conducting material. As shown in the figure, in the plate heat exchanger 5, the water and refrigerant flow vertically.

(How to connect a plate heat exchanger)
Fig. 8 shows an example of connection between a general plate heat exchanger 5A' and a plate heat exchanger 5B'. Fig. 8 shows the plate heat exchangers 5A' and 5B' when the plate 55 is viewed from the front. The plate heat exchanger 5 is used so that the vaporized refrigerant flows upward from the lower side of the plate 55a, etc., and the liquefied refrigerant flows downward from the upper side of the plate 55a, etc. That is, as shown in Fig. 8, in each of the plate heat exchangers 5A' and 5B', the refrigerant moves upward during cooling operation and moves downward during heating operation. The flow of the refrigerant during cooling operation is indicated by dashed arrows, and the flow of the refrigerant during heating operation is indicated by dashed arrows. Generally, plate heat exchangers 5A', 5B' (or plate heat exchangers 5A', 5B' in which the first end 51, which is a water inlet, is provided on the vertical lower side of the plate and the second end 52, which is a water outlet, is provided on the upper side of the plate) are provided on each of the heat pump chiller 1A and the heat pump chiller 1B, and these are connected in series. That is, as shown in FIG. 8, the second end 52A' provided on the upper side of the plate heat exchanger 5A' is connected to the first end 51B' provided on the lower side of the plate heat exchanger 5B'. Then, the flow of water in the plate heat exchangers 5A', 5B' is from the bottom to the top in both cases. As shown in the figure, in heating operation, the water and the refrigerant flow in opposite directions in both plate heat exchangers 5A' and 5B', and in cooling operation, the water and the refrigerant flow in the same direction in both plate heat exchangers 5A' and 5B'. When the water and the refrigerant flow in opposite directions, as in heating operation, it is called counterflow, and when the water and the refrigerant flow in the same direction, as in cooling operation, it is called parallel flow. Here, the heat exchange between the water and the refrigerant is more efficient in counterflow than in parallel flow. In the case of a heat pump chiller system connected as in the example of FIG. 8, higher performance is obtained in heating operation than in cooling operation, and performance is lower in cooling operation than in heating operation.

In this disclosure, the plate heat exchanger 5 is connected to eliminate bias in performance due to the operating mode and to obtain similar performance in both cooling and heating operations. At this time, since it is not preferable to change the flow of the refrigerant, the water flow is controlled so that parallel and counterflows are mixed in both cooling and heating operations. Figure 3 shows an example of the connection of the plate heat exchanger 5 according to this embodiment.

FIG. 3 is a diagram showing the connections of a plate heat exchanger according to an embodiment.
3, a plate heat exchanger 5A having a first end 51A provided on the vertical lower side of the plate and a second end 52A provided on the vertical upper side of the plate is provided in the heat pump chiller 1A, and a plate heat exchanger 5B having a first end 51B provided on the upper side of the plate and a second end 52B provided on the lower side of the plate is provided in the heat pump chiller 1B. The second end 52A and the first end 51B are connected by a pipe WL.
In this way, in the plate heat exchanger 5A, the water flowing in from the first end 51A flows from the bottom to the top, and the water flowing out from the second end 52A flows into the plate heat exchanger 5B from the first end 51B through the pipe WL. In the plate heat exchanger 5B, the water flows from the top to the bottom and flows out from the second end 52B. In this case, in the heating operation, the water and the refrigerant flow in countercurrent in the plate heat exchanger 5A, and in the plate heat exchanger 5B, the water and the refrigerant flow in parallel. In addition, in the cooling operation, the water and the refrigerant flow in parallel in the plate heat exchanger 5A, and in the plate heat exchanger 5B, the water and the refrigerant flow in countercurrent. In other words, in both the cooling operation and the heating operation, the water and the refrigerant exchange heat with one countercurrent heat exchanger and one parallel heat exchanger, and the performance difference and bias between the cooling operation and the heating operation are eliminated.

Next, the setup and operation of the heat pump chiller system 100 including the plate heat exchangers 5A, 5B illustrated in FIG. 3 will be described with reference to FIGS. 4A and 4B.
FIG. 4A is a first diagram illustrating an example of the settings and operation of a heat pump chiller system according to one embodiment.
In this embodiment, the plate heat exchanger 5 that bears a large cooling load or heating load is called the "main operating plate heat exchanger." As described with reference to Fig. 3, during cooling operation, water and refrigerant flow in parallel in the plate heat exchanger 5A, and water and refrigerant flow in countercurrent in the plate heat exchanger 5B. In this case, the plate heat exchanger 5B with high heat exchange efficiency is defined as the "main operating plate heat exchanger," and the control device 10 sets the heat pump chiller 1B to allocate a larger cooling load.

For example, when cooling operation is required to lower the temperature of water sent from the load side by 5°C and return it to the load, the control device 10 sets the set temperature of heat pump chiller 1A in control device 7A so that the temperature difference between the water flowing into heat pump chiller 1A and the water flowing out of heat pump chiller 1A is 2°C (the temperature of the outflowing water is 2°C lower). Then, for heat pump chiller 1B, which is the "main operating plate type heat exchanger," the control device 10 sets the set temperature in control device 7B so that the temperature difference between the water flowing in and the water flowing out is 3°C (the temperature of the outflowing water is 3°C lower).

Furthermore, when a relatively light-load cooling operation is required, for example, by lowering the temperature of the water sent from the load side by 3°C and returning it to the load, the control device 10 stops the heat pump chiller 1A and operates only the heat pump chiller 1B equipped with the "main operating plate-type heat exchanger" (light-load operation). The control device 10 sets the set temperature for the heat pump chiller 1B in the control device 7B to lower the water temperature by 3°C. The "Cooling" row in Figure 4A shows these settings and operation details.

In addition, in the configuration of FIG. 3, during heating operation, the water and the refrigerant flow in countercurrent in the plate heat exchanger 5A, and flow in parallel in the plate heat exchanger 5B. In this case, the control device 10 determines the plate heat exchanger 5A with high heat exchange efficiency as the "main operating plate heat exchanger" and sets the heat pump chiller 1A to allocate a larger heating load. For example, when a heating operation is required in which the temperature of the water sent from the load side is raised by 5°C and returned to the load, the control device 10 sets the set temperature in the control device 7A so that the temperature difference between the water flowing into the heat pump chiller 1A and the water flowing out of the heat pump chiller 1A is 3°C (the temperature of the outflowing water is 3°C higher). Then, the control device 10 sets the set temperature of the heat pump chiller 1B in the control device 7B so that the temperature difference between the water flowing into the heat pump chiller 1B and the water flowing out of the heat pump chiller 1B is 2°C (the temperature of the outflowing water is 2°C higher).

In addition, when a relatively light load heating operation is required, for example, where the temperature of the water sent from the load side is raised by 3°C and returned to the load, the control device 10 stops the heat pump chiller 1B and operates only the heat pump chiller 1A (light load operation). The control device 10 sets a set temperature in the control device 7A that will raise the water temperature by 3°C. The "Heating" row in Figure 4A shows these settings and operation details.

If light load operation continues for a long time, only the heat pump chiller 1 equipped with the "main operating plate type heat exchanger" will be used for a long time, and the other heat pump chiller 1 will be stopped for a long time. If this state continues for a long time, a difference in performance and condition will occur between the two heat pump chillers 1. To eliminate such bias, the control device 10 may perform a leveling operation when the difference between the operating time of heat pump chiller 1A and the operating time of heat pump chiller 1B exceeds a threshold value. Leveling operation is an operation that levels out the bias in the operating times of heat pump chillers 1A and 1B. Figure 4B shows an example of the settings and operation of the heat pump chiller system 100 in leveling operation.

(Leveling operation)
FIG. 4B is a second diagram illustrating an example of settings and operation of the heat pump chiller system according to one embodiment.
For example, in the case of cooling operation, if light load operation continues for a long time, the operation time of the heat pump chiller 1B becomes longer than the operation time of the heat pump chiller 1A by a predetermined time or more. Then, the control device 10 switches the "main operating plate type heat exchanger" from the plate type heat exchanger 5B to the plate type heat exchanger 5A. For example, the control device 10 starts the compressor 2A through the control device 7A and puts the heat pump chiller 1A into operation. The control device 10 also stops the compressor 2A through the control device 7B and stops the heat pump chiller 1B. The control device 10 also sets the set temperature in the control device 7A so that the temperature difference between the water flowing into the heat pump chiller 1A and the water flowing out is 3°C (the temperature of the outflowing water is 3°C lower). This makes it possible to stop the heat pump chiller 1B that has been in operation for a long time and operate the heat pump chiller 1A that has been stopped for a long time. For example, the control device 10 performs cooling operation using the heat pump chiller 1A until the operation times of the heat pump chillers 1A and 1B become equal. When the operation times of the heat pump chillers 1A and 1B become equal, the control device 10 again switches operation to the plate heat exchanger 5B, which has a higher heat exchange efficiency, as the "main operating plate heat exchanger."

Similarly, if the light-load heating operation continues for a long time, the operation time of the heat pump chiller 1A becomes longer than the operation time of the heat pump chiller 1B by a predetermined time or more. Then, the control device 10 switches the "main operating plate heat exchanger" from the plate heat exchanger 5A to the plate heat exchanger 5B. For example, the control device 10 stops the heat pump chiller 1A and starts the heat pump chiller 1B. The control device 10 also sets the set temperature in the control device 7B so that the temperature difference between the water flowing into and flowing out of the heat pump chiller 1B is 3°C (the temperature of the outflowing water is 3°C higher). Then, when the operation times of the heat pump chillers 1A and 1B become equal, the control device 10 again switches to light-load heating operation with the plate heat exchanger 5A, which has a high heat exchange efficiency, as the "main operating plate heat exchanger."

Note that it is not essential to perform the leveling operation. For example, when performance is prioritized, even if there is a discrepancy between the operating times of heat pump chiller 1A and heat pump chiller 1B, the control device 10 may continue operation during the performance-priority operation shown in FIG. 4A. Furthermore, the user can arbitrarily set in the control device 10 whether to perform performance-priority operation or leveling operation. Furthermore, when leveling operation is performed, the user can arbitrarily set in the control device 10 the timing of switching (operating time difference) from the heat pump chiller 1 with good heat exchange efficiency to the heat pump chiller 1 with poor heat exchange efficiency.

In this way, according to this embodiment, in a heat pump chiller system 100 equipped with two heat pump chillers 1, it is possible to eliminate the imbalance in performance between cooling and heating operations, and to make the cooling and heating operations equivalent. Furthermore, when only one heat pump chiller 1 is operated under low load, the heat pump chiller 1 with better performance can be selected and operated in cooling and heating operations. Furthermore, when the operating time of one heat pump chiller 1 becomes longer than a predetermined time, the other heat pump chiller 1 is switched to and continues operating, thereby leveling out the operating time.

The number of heat pump chillers 1 constituting the heat pump chiller system 100 is not limited to two. For example, if there is an even number of heat pump chillers 1, two heat pump chillers 1 connected by the connection method illustrated in FIG. 3 are treated as one unit, and multiple such units are provided. If there is an odd number of heat pump chillers 1, one of the units is set with a water inlet/outlet and a refrigerant inlet/outlet so that the water and refrigerant flow in countercurrent directions in the most important operating state (for example, if heating operation is more important than cooling operation, the water and refrigerant are set to flow in countercurrent directions during heating operation), and the rest are composed of the above units.

Second Embodiment
A heat pump chiller system according to a second embodiment of the present invention will now be described with reference to FIGS.
In the first embodiment, corresponding flows and parallel flows are mixed in the two plate heat exchangers 5, and the water flows are controlled so that one of the plates has corresponding flows and the other has parallel flows. In the second embodiment, the water flows are controlled so that both of the two plate heat exchangers 5 have corresponding flows.

FIG. 5 is a first diagram showing connections of a plate heat exchanger according to the second embodiment.
Figure 5 shows two plate heat exchangers 5C and 5D. In the plate heat exchangers 5C and 5D, the first ends 51C and 51D, which are water inlets, are provided on the lower side of the plate, and the second ends 52C and 52D, which are water outlets, are provided on the upper side, similar to the general connection illustrated in Figure 8. However, unlike the example in Figure 8, in the third embodiment, the first ends 51C and 51D are water outlets and the second ends 52C and 52D are water inlets depending on the operation mode (cooling, heating). For example, the plate heat exchanger 5C is provided in the heat pump chiller 1A in Figure 1, and the plate heat exchanger 5D is provided in the heat pump chiller 1B.

Regarding the piping WL, the piping WL that introduces water to the heat pump chiller 1 on the upstream side is piping WL3, the piping WL that connects the heat pump chiller 1 on the upstream side to the heat pump chiller 1 on the downstream side is piping WL4, and the piping WL that discharges water from the heat pump chiller 1 on the downstream side is piping WL5. Then, connection points C1 and C2 with other piping are provided in order from the upstream side of the piping WL3, and connection points C3 and C4 with other piping are provided in order from the upstream side of the piping WL5. Then, connection point C1 and connection point C3 are connected by the piping WL6, and connection point C2 and connection point C4 are connected by the piping WL7. Also, a valve V1 is provided between connection point C1 and connection point C2 in the piping WL3, a valve V2 is provided in the piping WL6, and a valve V3 is provided in the piping WL7. Also, a valve V4 is provided between connection point C3 and connection point C4 in the piping WL3. The control device 10 controls the opening and closing of the valves V1 to V4. For example, during heating operation, the control device 10 opens the valves V1 and V4 and closes the valves V2 and V3. Then, the water flowing through the pipe WL3 flows into the plate heat exchanger 5C from the first end 51C and flows upward from the lower side of the plate on which the first end 51C is provided. The water also flows out from the second end 52C of the plate heat exchanger 5C and flows into the plate heat exchanger 5D from the first end 51D through the pipe WL4. In the plate heat exchanger 5D, the water also flows upward from the lower side of the plate, flows out from the second end 52D, and is supplied to the load through the pipe WL5. As shown in FIG. 5, the water and the refrigerant flow in countercurrents in both the plate heat exchangers 5C and 5D. This enables efficient heat exchange between the water and the refrigerant, and the performance of the heating operation can be improved compared to the first embodiment.

Next, the flow of water and refrigerant during cooling operation will be described with reference to FIG.
FIG. 6 is a second diagram showing the connection of the plate heat exchanger according to the second embodiment.
During cooling operation, the control device 10 closes the valves V1 and V4 and opens the valves V2 and V3. Then, the water flowing through the pipe WL3 flows through the pipe WL3, the pipe WL7, and the pipe WL5 in this order, flows into the plate heat exchanger 5D from the second end 52D, flows downward from the upper side where the second end 52D is provided, and flows out from the first end 51D of the plate heat exchanger 5D. Then, the water flows through the pipe WL4 into the plate heat exchanger 5C from the second end 52C, flows downward from the upper side where the second end 52C is provided, and flows out from the first end 51C of the plate heat exchanger 5C. The water flowing out of the plate heat exchanger 5C flows through the pipe WL3, the pipe WL6, and the pipe WL5 in this order, and is supplied to the load through the pipe WL5. As shown in Fig. 6, during cooling operation, the water and the refrigerant flow in countercurrent fashion in both plate heat exchangers 5C and 5D. This allows for efficient heat exchange between the water and the refrigerant, and improves the performance of the cooling operation compared to the first embodiment.

As described above, according to the second embodiment, regardless of whether the operation is cooling or heating, it is possible to realize corresponding flows of water and refrigerant in both of the two heat pump chillers 1. Therefore, unlike the general connection illustrated in Fig. 8, there is no decrease in performance in either cooling or heating operation, and high performance can be maintained in either operating state.
As in the first embodiment, during low load conditions, only one of the heat pump chillers 1 may be operated and the other may be stopped. In addition, when a time difference of a predetermined time or more occurs between the operation times of the heat pump chillers 1A and 1B, a leveling operation may be performed under the control of the control device 10.

In the second embodiment, the number of heat pump chillers 1 is not limited to two. For example, if there is an even number of heat pump chillers 1, two heat pump chillers 1 connected by the connection method illustrated in Figures 5 and 6 are treated as one unit, and multiple such units are provided. If there is an odd number of heat pump chillers 1, one of the units has a water inlet/outlet and a refrigerant inlet/outlet set so that the water and refrigerant flow in countercurrent directions in the most important operating state, and the rest are configured with the above units.

Third Embodiment
Hereinafter, a heat pump chiller system according to a third embodiment of the present invention will be described with reference to FIGS. 7A and 7B.
In the third embodiment, a heat pump chiller system 100' is provided that combines the first and second embodiments. FIG. 7A shows the heat pump chiller system 100' according to the third embodiment. The heat pump chiller system 100' includes a heat pump chiller 1A, a heat pump chiller 1B, a heat pump chiller 1C, a heat pump chiller 1D, and a control device 10 that controls the heat pump chillers 1A to 1D. The heat pump chillers 1A to 1D are connected in series. That is, water flowing from the load side flows into the heat pump chiller 1A, is heat exchanged and flows out, then flows into the heat pump chiller 1B, is heat exchanged and flows out, then flows into the heat pump chiller 1C, is heat exchanged and flows out, then flows into the heat pump chiller 1D, is heat exchanged and flows out, and is then supplied to the load.

The heat pump chiller 1A is equipped with a plate heat exchanger 5A as shown in FIG. 3, and the heat pump chiller 1B is equipped with a plate heat exchanger 5B as shown in FIG. 3. The plate heat exchanger 5A and the plate heat exchanger 5B are connected as shown in FIG. 3.

The heat pump chiller 1C is equipped with a plate heat exchanger 5C as shown in Figs. 5 and 6, and the heat pump chiller 1D is equipped with a plate heat exchanger 5D as shown in Figs. 5 and 6. The plate heat exchanger 5C and the plate heat exchanger 5D are connected as shown in Figs. 5 and 6. The second end 52B of the plate heat exchanger 5B (Fig. 3) is connected to the pipe WL3 as shown in Figs. 5 and 6.

During cooling operation, the control device 10 closes valves V1 and V4 and opens valves V2 and V3 as shown in FIG. 6. During heating operation, the control device 10 opens valves V1 and V4 and closes valves V2 and V3 as shown in FIG. 5.

Figure 7B shows the relationship between the flow directions of water and refrigerant in plate heat exchangers 5A to 5D when controlled in this way. As shown in Figure 7B, during cooling operation, the flow is parallel in plate heat exchanger 5A and counter-flow in plate heat exchangers 5B to 5D. During heating operation, the flow is parallel in plate heat exchanger 5B and counter-flow in plate heat exchangers 5A, 5C to 5D.

By combining the first and second embodiments in this way, the ratio of parallel flow to counterflow can be set to 1:3, enabling high performance operation in both cooling and heating modes.

The control devices 7 and 10 are equipped with a computer. The computer includes a CPU, a main memory device, an auxiliary memory device, an input/output interface, a communication interface, and the like. Each process in the control devices 7 and 10 can be realized, for example, by the CPU or the like of the control devices 7 and 10 executing a program. The program executed by the control devices 7 and 10 may be recorded on a computer-readable recording medium, and may be realized by reading and executing the program recorded on the recording medium. The control devices 7 and 10 include hardware such as an OS and peripheral devices. The computer-readable recording medium is, for example, a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, and a storage device such as a hard disk built into the control devices 7 and 10.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as set forth in the claims, as well as in the scope and gist of the invention.

<Additional Notes>
The heat pump chiller systems 100, 100' and the plate heat exchanger connection methods described in each embodiment can be understood, for example, as follows.

(1) A heat pump chiller system 100, 100' according to a first aspect comprises a first heat pump chiller 1A including a first plate heat exchanger 5A that performs heat exchange between a heat medium (water) supplied to a load and a first refrigerant, and a second heat pump chiller 1B including a second plate heat exchanger 5B that performs heat exchange between the heat medium and a second refrigerant, wherein a flow path of the heat medium is provided such that when the flow directions of the heat medium and the first refrigerant in the first plate heat exchanger 5A are counter-current, the flow directions of the heat medium and the second refrigerant in the second plate heat exchanger 5B are parallel, and when the flow directions of the heat medium and the second refrigerant in the second plate heat exchanger 5B are counter-current, the flow directions of the heat medium and the first refrigerant in the first plate heat exchanger 5A are parallel.
This allows the cooling operation and heating operation to be performed with the same level of performance.

(2) The heat pump chiller system 100, 100' according to the second aspect is the heat pump chiller system 100, 100' according to (1), further comprising a heat medium flow path connecting the heat medium outlet of the first plate heat exchanger 5A and the heat medium inlet of the second plate heat exchanger 5B, and the first heat pump chiller 1A and the second heat pump chiller 1B are connected in series.

(3) The heat pump chiller system 100, 100' according to the third aspect is the heat pump chiller system 100, 100' according to (1) to (2), in which the first refrigerant and the second refrigerant flow vertically from bottom to top during cooling operation, and the first refrigerant and the second refrigerant flow vertically from top to bottom during heating operation.

(4) A heat pump chiller system 100, 100' according to a fourth aspect is the heat pump chiller system 100, 100' of (1) to (3), wherein, during heating operation, when the flow directions of the heat medium and the first refrigerant are counter-flowing, a set temperature is set so that a difference between the temperature of the heat medium at the inlet and the temperature of the heat medium at the outlet of the first heat pump chiller is greater than a difference between the temperature of the heat medium at the inlet and the temperature of the heat medium at the outlet of the second heat pump chiller, and when the flow directions of the heat medium and the second refrigerant are counter-flowing, a set temperature is set so that a difference between the temperature of the heat medium at the inlet and the temperature of the heat medium at the outlet of the second heat pump chiller is greater than a difference between the temperature of the heat medium at the inlet and the temperature of the heat medium at the outlet of the first heat pump chiller.
By having a large heating load borne by the heat pump chiller equipped with the plate heat exchanger 5, which has high heat exchange efficiency, efficient heating operation can be performed.

(5) A fifth aspect of the heat pump chiller system 100, 100' is the heat pump chiller system 100, 100' of (1) to (4), wherein, during cooling operation, when the flow directions of the heat medium and the first refrigerant are counter-flowing, a set temperature is set so that a difference between the temperature of the heat medium at the inlet and the temperature of the heat medium at the outlet of the first heat pump chiller is greater than a difference between the temperature of the heat medium at the inlet and the temperature of the heat medium at the outlet of the second heat pump chiller, and when the flow directions of the heat medium and the second refrigerant are counter-flowing, a set temperature is set so that a difference between the temperature of the heat medium at the inlet and the temperature of the heat medium at the outlet of the second heat pump chiller is greater than a difference between the temperature of the heat medium at the inlet and the temperature of the heat medium at the outlet of the first heat pump chiller.
By having a large cooling load borne by the heat pump chiller equipped with the plate heat exchanger 5, which has high heat exchange efficiency, efficient cooling operation can be performed.

(6) A sixth aspect of the heat pump chiller system 100, 100' is the heat pump chiller system 100, 100' of any one of (1) to (5), in which when the load is equal to or less than a predetermined threshold and the flow directions of the heat medium and the first refrigerant are counter-current, the operation of the second heat pump chiller is stopped, and when the flow directions of the heat medium and the second refrigerant are counter-current, the operation of the first heat pump chiller is stopped.
In the case of low load, the load is covered by operating the heat pump chiller 1 equipped with the plate heat exchanger 5, which has high heat exchange efficiency, and energy-saving operation can be achieved by stopping the operation of the heat pump chiller 1 equipped with the plate heat exchanger 5, which has high heat exchange efficiency.

(7) A seventh aspect of the heat pump chiller system 100, 100' is the heat pump chiller system 100, 100' of (1) to (6), wherein, when the operating time of the first heat pump chiller is longer than a predetermined time than the operating time of the second heat pump chiller, the first heat pump chiller is stopped and the second heat pump chiller is operated, regardless of the relationship between the flow directions of the heat medium and the refrigerant, and when the operating time of the second heat pump chiller is longer than a predetermined time than the operating time of the first heat pump chiller, the second heat pump chiller is stopped and the first heat pump chiller is operated, regardless of the relationship between the flow directions of the heat medium and the refrigerant.
The operation times of the heat pump chillers 1A and 1B can be equalized.

(8) The heat pump chiller system 100, 100' according to an eighth aspect is the heat pump chiller system 100, 100' of any one of (1) to (7), wherein when the heat medium outlet in the first plate heat exchanger is provided on the vertical lower side, the heat medium inlet in the second plate heat exchanger is provided on the vertical lower side, and when the heat medium outlet in the first plate heat exchanger is provided on the vertical upper side, the heat medium inlet in the second plate heat exchanger is provided on the vertical upper side.
This allows the two heat pump chillers to have a mixture of counter flow and parallel flow.

(9) A heat pump chiller system 100' according to a ninth aspect is the heat pump chiller system 100' of any one of (1) to (8), further comprising a third heat pump chiller 1C including a third plate heat exchanger 5C that performs heat exchange between the heat medium and a third refrigerant, a fourth heat pump chiller 1D including a fourth plate heat exchanger 5D that performs heat exchange between the heat medium and a fourth refrigerant, a connection flow path that connects the third plate heat exchanger 5C and the fourth plate heat exchanger 5D, and a switching mechanism (pipes WL3, WL5, WL6, WL7, valves V1 to V4) that switches to either the third plate heat exchanger or the fourth plate heat exchanger to supply the heat medium, and the flow direction of the fourth refrigerant in the third plate type heat exchanger is from top to bottom, the connecting flow paths are provided so that the flows of the heat medium in both the third plate type heat exchanger and the fourth plate type heat exchanger are from bottom to top, and the heat medium is supplied to the third plate type heat exchanger such that the heat medium flows from the third plate type heat exchanger to the fourth plate type heat exchanger under the control of the switching mechanism, and when the flow direction of the third refrigerant in the third plate type heat exchanger and the flow direction of the fourth refrigerant in the fourth plate type heat exchanger are both switched from bottom to top, the heat medium is supplied to the fourth plate type heat exchanger such that the heat medium flows from the fourth plate type heat exchanger to the third plate type heat exchanger under the control of the switching mechanism.
This allows the water and refrigerant to flow in opposite directions regardless of the flow of the refrigerant, enabling high performance to be achieved in both cooling and heating operations.

(10) The method of connecting plate heat exchangers according to the tenth aspect is a heat pump chiller system including a first heat pump chiller having a first plate heat exchanger that performs heat exchange between a heat medium supplied to a load and a first refrigerant, and a second heat pump chiller having a second plate heat exchanger that performs heat exchange between the heat medium and a second refrigerant, in which the first plate heat exchanger and the second plate heat exchanger are connected such that when the flow directions of the heat medium and the first refrigerant in the first plate heat exchanger are counter-current, the flow directions of the heat medium and the second refrigerant in the second plate heat exchanger are parallel, and when the flow directions of the heat medium and the second refrigerant in the second plate heat exchanger are counter-current, the flow directions of the heat medium and the first refrigerant in the first plate heat exchanger are parallel.

100, 100'... Heat pump chiller system 1, 1A, 1B, 1C, 1D... Heat pump chiller 7, 7A, 7B, 10... Control device 2, 2A, 2B... Compressor 3, 3A, 3B... Four-way valve 4, 4A, 4B... Heat exchanger 5, 5A, 5B... Plate type heat exchanger 6, 6A, 6B... Expansion valve WL, WL1, WL2, WL3, WL4, WL5, WL6, WL7... Piping V1, V2, V3, V4... Valve

Claims (9)

a first heat pump chiller including a first plate heat exchanger that performs heat exchange between a heat medium to be supplied to a load and a first refrigerant;
a second heat pump chiller including a second plate heat exchanger that exchanges heat between the heat medium and a second refrigerant;
a third heat pump chiller including a third plate heat exchanger that performs heat exchange between the heat medium and a third refrigerant;
a fourth heat pump chiller including a fourth plate heat exchanger that performs heat exchange between the heat medium and a fourth refrigerant;
a connecting flow passage connecting the third plate heat exchanger and the fourth plate heat exchanger;
a switching mechanism that switches between the third plate heat exchanger and the fourth plate heat exchanger to supply the heat medium;
Equipped with
a flow path for the heat medium is provided such that when the flow directions of the heat medium and the first refrigerant in the first plate heat exchanger are counter-flowing, the flow directions of the heat medium and the second refrigerant in the second plate heat exchanger are parallel flowing, and when the flow directions of the heat medium and the second refrigerant in the second plate heat exchanger are counter-flowing, the flow directions of the heat medium and the first refrigerant in the first plate heat exchanger are parallel flowing ,
When the flow direction of the third refrigerant in the third plate heat exchanger and the flow direction of the fourth refrigerant in the fourth plate heat exchanger are both from top to bottom, the connection flow path is provided so that the flow of the heat medium in both the third plate heat exchanger and the fourth plate heat exchanger is from bottom to top, and the heat medium is supplied to the third plate heat exchanger by controlling the switching mechanism so that the heat medium flows in the order from the third plate heat exchanger to the fourth plate heat exchanger,
When the flow direction of the third refrigerant in the third plate heat exchanger and the flow direction of the fourth refrigerant in the fourth plate heat exchanger are both switched from bottom to top, the heat medium is supplied to the fourth plate heat exchanger by control of the switching mechanism so that the heat medium flows from the fourth plate heat exchanger to the third plate heat exchanger in that order.
Heat pump chiller system. A flow path for the heat medium connecting an outlet for the heat medium in the first plate heat exchanger and an inlet for the heat medium in the second plate heat exchanger,
The heat pump chiller system according to claim 1 , wherein the first heat pump chiller and the second heat pump chiller are connected in series. During cooling operation, the first refrigerant and the second refrigerant flow vertically from bottom to top, and during heating operation, the first refrigerant and the second refrigerant flow vertically from top to bottom.
The heat pump chiller system according to claim 1 or 2. during heating operation, when the flow directions of the heat medium and the first refrigerant are counter-flowing, set temperatures of the first heat pump chiller and the second heat pump chiller are set so that a difference between a temperature of the heat medium at an inlet of the first heat pump chiller and a temperature of the heat medium at an outlet thereof is larger than a difference between a temperature of the heat medium at an inlet of the second heat pump chiller and a temperature of the heat medium at an outlet thereof, and when the flow directions of the heat medium and the second refrigerant are counter-flowing, set temperatures are set so that a difference between a temperature of the heat medium at an inlet of the second heat pump chiller and a temperature of the heat medium at an outlet thereof is larger than a difference between a temperature of the heat medium at an inlet of the first heat pump chiller and a temperature of the heat medium at an outlet thereof.
The heat pump chiller system according to any one of claims 1 to 3. during cooling operation, when the flow directions of the heat medium and the first refrigerant are counter-flowing, set temperatures of the first heat pump chiller and the second heat pump chiller are set so that a difference between a temperature of the heat medium at an inlet of the first heat pump chiller and a temperature of the heat medium at an outlet thereof is larger than a difference between a temperature of the heat medium at an inlet of the second heat pump chiller and a temperature of the heat medium at an outlet thereof, and when the flow directions of the heat medium and the second refrigerant are counter-flowing, set temperatures are set so that a difference between a temperature of the heat medium at an inlet of the second heat pump chiller and a temperature of the heat medium at an outlet thereof is larger than a difference between a temperature of the heat medium at an inlet of the first heat pump chiller and a temperature of the heat medium at an outlet thereof.
The heat pump chiller system according to any one of claims 1 to 4. When a load is equal to or less than a predetermined threshold and the flow directions of the heat medium and the first refrigerant are counter-current flows, the second heat pump chiller is stopped, and when the flow directions of the heat medium and the second refrigerant are counter-current flows, the first heat pump chiller is stopped.
The heat pump chiller system according to any one of claims 1 to 5. When the operation time of the first heat pump chiller is longer than a predetermined time than the operation time of the second heat pump chiller, regardless of the relationship between the flow directions of the heat medium and the refrigerant, the first heat pump chiller is stopped and the second heat pump chiller is operated;
When an operation time of the second heat pump chiller is longer than a predetermined time than an operation time of the first heat pump chiller, the second heat pump chiller is stopped and the first heat pump chiller is operated regardless of a relationship between a flow direction of the heat medium and a flow direction of the refrigerant.
The heat pump chiller system according to any one of claims 1 to 6. When the outlet of the heat medium in the first plate heat exchanger is provided on the lower side in the vertical direction, the inlet of the heat medium in the second plate heat exchanger is provided on the lower side in the vertical direction; when the outlet of the heat medium in the first plate heat exchanger is provided on the upper side in the vertical direction, the inlet of the heat medium in the second plate heat exchanger is provided on the upper side in the vertical direction.
The heat pump chiller system according to any one of claims 1 to 7. a first heat pump chiller including a first plate heat exchanger that performs heat exchange between a heat medium to be supplied to a load and a first refrigerant, a second heat pump chiller including a second plate heat exchanger that performs heat exchange between the heat medium and a second refrigerant, a third heat pump chiller including a third plate heat exchanger that performs heat exchange between the heat medium and a third refrigerant, a fourth heat pump chiller including a fourth plate heat exchanger that performs heat exchange between the heat medium and a fourth refrigerant, a connecting flow path that connects the third plate heat exchanger and the fourth plate heat exchanger, and a switching mechanism that switches between the third plate heat exchanger or the fourth plate heat exchanger to supply the heat medium ,
The first plate heat exchanger and the second plate heat exchanger are connected such that when the flow directions of the heat medium and the first refrigerant in the first plate heat exchanger are counter-flowing, the flow directions of the heat medium and the second refrigerant in the second plate heat exchanger are parallel flowing, and when the flow directions of the heat medium and the second refrigerant in the second plate heat exchanger are counter-flowing, the flow directions of the heat medium and the first refrigerant in the first plate heat exchanger are parallel flowing,
When the flow direction of the third refrigerant in the third plate heat exchanger and the flow direction of the fourth refrigerant in the fourth plate heat exchanger are both from top to bottom, the connecting flow path is provided so that the flow of the heat medium in both the third plate heat exchanger and the fourth plate heat exchanger is from bottom to top, and the heat medium is supplied to the third plate heat exchanger by controlling the switching mechanism so that the heat medium flows in the order from the third plate heat exchanger to the fourth plate heat exchanger;
when the flow direction of the third refrigerant in the third plate heat exchanger and the flow direction of the fourth refrigerant in the fourth plate heat exchanger are both switched from bottom to top, the heat medium is supplied to the fourth plate heat exchanger by control of the switching mechanism so that the heat medium flows from the fourth plate heat exchanger to the third plate heat exchanger in that order.
How to connect a plate heat exchanger.

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