Refrigeration Cycle Equipment

Abstract

To increase reliability of a refrigeration cycle device.SOLUTION: In a refrigeration cycle device, a first refrigerant circulates in a low-dimensional refrigerant circuit. In a high-dimensional circuit, a second refrigerant that exchanges heat with the first refrigerant circulates in a cascade heat exchanger. In a water circuit having a second indoor heat exchanger and a water refrigerant heat exchanger, water that exchanges heat with the second refrigerant circulates in the water refrigerant heat exchanger. A heat radiator is connected to at least the high-dimensional circuit or the water circuit by a bypass flow passage so that the second refrigerant or the water can be bypassed. A control device, during heating operation by indoor equipment of the second indoor heat exchanger, can switch the heating operation to a first heating operation for flowing the second refrigerant or the water only to the bypass flow passage, or to a second heating operation for flowing the second refrigerant or the water to both the heat radiator and the bypass flow passage, and also in the second heating operation, it determines a rotational frequency of a second compressor on the basis of required capacities of the indoor equipment of the second indoor heat exchanger and the heat radiator.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a refrigeration cycle device. [Background technology]

[0002] Conventionally, there is a refrigeration cycle device that has a low-side refrigerant circuit through which a first refrigerant circulates, and a high-side refrigerant circuit that is connected to the low-side refrigerant circuit and through which a second refrigerant circulates that exchanges heat with the first refrigerant, forming a two-stage refrigeration cycle (Patent Document 1).

[0003] In this refrigeration cycle apparatus, a hot water generation unit and an indoor unit are connected in parallel to an outdoor unit to form a low-stage refrigerant circuit. A high-stage refrigerant circuit is formed in the hot water generation unit, and a water circuit through which water circulates is connected to the high-stage refrigerant circuit. Then, in the hot water generation unit, hot water is generated by heat exchange between the second refrigerant and the water. As a result, in the refrigeration cycle apparatus, the indoor unit connected to the low-stage refrigerant circuit conditions the user's room, and at the same time, hot water is supplied using the hot water generated in the hot water generation unit, and air conditioning is possible using the indoor unit using the hot water. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-179352 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above conventional technology, when the temperature of hot water to be generated in the hot water generating unit is low and the thermal load of the hot water generating unit is small, the compression ratio of the compressor in the high-stage refrigerant circuit tends to be small. This causes a problem of deterioration in reliability of the compressor in the high-stage refrigerant circuit, such as the vane not being able to follow the movement of the compressor roller, a so-called vane skipping phenomenon. If the compression ratio is increased by increasing the rotation speed of the compressor in the high-stage refrigerant circuit to prevent the reliability from decreasing, the water will be excessively heated by the second refrigerant, and the comfort of the hot water user will be impaired.

[0006] The disclosed technique has been made in consideration of the above points, and has an object to provide a highly reliable refrigeration cycle device. [Means for solving the problem]

[0007] A refrigeration cycle device according to one aspect of the present disclosure includes a low-stage refrigerant circuit, a high-stage refrigerant circuit, and a water circuit. Heat storage A device and a bypass flow path, Flow path switching The low-stage refrigerant circuit includes an outdoor heat exchanger, a first compressor, a cascade heat exchanger, a first pressure reducing means, and a first indoor heat exchanger, and a first refrigerant circulates therethrough. The high-stage refrigerant circuit includes a second compressor, a water-refrigerant heat exchanger, a second pressure reducing means, and a cascade heat exchanger, and a second refrigerant that exchanges heat with the first refrigerant in the cascade heat exchanger circulates therethrough. , the second compressor is driven The water circuit has a circulation pump, a second indoor heat exchanger, and a water-refrigerant heat exchanger, and water circulates to exchange heat with the second refrigerant in the water-refrigerant heat exchanger. Heat storage The device is A heat storage material is included, Water times On the road Connected, Heat storage material Heat of water Between the heat exchanger The bypass flow path is Heat storage Without the use of a device Water Bypass the Flow path switching The valve is Heat storage The device and the bypass flow path Water of Flow Path of switchingThe control device includes a first compressor, a first pressure reducing means, a second compressor, a second pressure reducing means, a circulation pump, and Flow path switching The control device controls the valve during heating operation by the indoor unit of the second indoor heat exchanger. ,water A first heating operation in which the air is circulated only through the bypass flow path, or ,water of Heat storage Second heating operation in which air flows through both the device and the bypass flow path or a third heating operation in which the water is caused to flow only through the heat storage device among the heat storage device and the bypass flow path, and the heat stored in the heat storage device is released to heat the water. In the second heating operation, the indoor unit of the second indoor heat exchanger and Heat storage Determine the rotation speed of the second compressor based on the required capacity of the equipment. The control device drives the second compressor so that the second refrigerant circulates in the high-temperature refrigerant circuit in the first heating operation and the second heating operation, and stops the second compressor so that the second refrigerant does not circulate in the high-temperature refrigerant circuit in the third heating operation. do. Effect of the Invention

[0008] According to one aspect, the reliability of the refrigeration cycle device can be improved. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram illustrating an example of a refrigeration cycle device according to an embodiment. [Diagram 2] FIG. 2 is a flowchart illustrating an example of control of the refrigeration cycle device according to the embodiment. [Diagram 3] FIG. 3 is a timing chart showing an example of the operation of the refrigeration cycle device according to the embodiment. [Figure 4] FIG. 4 is a pH diagram illustrating the refrigeration cycle of the refrigeration cycle device according to the embodiment. [Diagram 5] FIG. 5 is an explanatory diagram illustrating a first modified example of the refrigeration cycle device according to the embodiment. [Figure 6] FIG. 6 is a flowchart illustrating a control example of the first modification of the refrigeration cycle device according to the embodiment. [Figure 7] FIG. 7 is an explanatory diagram illustrating a second modified example of the refrigeration cycle device according to the embodiment. [Figure 8] FIG. 8 is a flowchart showing a control example of the second modification of the refrigeration cycle device according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a refrigeration cycle device according to an embodiment will be described with reference to the drawings. Components having the same functions in the embodiments are given the same reference numerals, and duplicated descriptions will be omitted. Note that the refrigeration cycle device described in the following embodiment is merely an example, and does not limit the embodiment. In addition, the following embodiments may be appropriately combined within a range that does not cause contradiction.

[0011] Fig. 1 is an explanatory diagram showing an example of a refrigeration cycle apparatus 1 according to an embodiment. As shown in Fig. 1, the refrigeration cycle apparatus 1 includes a low-stage refrigerant circuit 10, a high-stage refrigerant circuit 20, a water circuit 30, a heat storage device 33, a first flow path adjustment valve 34a, a second flow path adjustment valve 34b, and a third flow path adjustment valve 34c as flow path switching valves, and a control device 50.

[0012] The low-stage refrigerant circuit 10 has an outdoor heat exchanger 11, a low-stage side compressor 12, a cascade heat exchanger 13, expansion valves 14a, 14b (first pressure reducing means), an indoor heat exchanger 15 (first indoor heat exchanger), operating valves 16a, 16b and a four-way valve 17, and a refrigerant (first refrigerant) circulates through it.

[0013] The outdoor heat exchanger 11 exchanges heat between outside air and the refrigerant circulating in the low-level refrigerant circuit 10 in an outdoor unit 11a provided outdoors.

[0014] The low-stage side compressor 12 is a compressor whose operating capacity can be varied according to, for example, the driving of a motor (not shown) whose rotation speed is controlled by an inverter under the control of the control device 50. The low-stage side compressor 12 is an example of a first compressor that compresses the refrigerant circulating in the low-stage refrigerant circuit 10 by being driven at a rotation speed controlled by the control device 50.

[0015] The cascade heat exchanger 13 exchanges heat between the refrigerant circulating through the low stage refrigerant circuit 10 and the refrigerant circulating through the high stage refrigerant circuit 20 (second refrigerant).

[0016] The expansion valves 14a and 14b are electronic expansion valves driven by a pulse motor (not shown) under the control of the control device 50. The expansion valves 14a and 14b adjust the flow rate of the refrigerant flowing into the cascade heat exchanger 13 and the indoor heat exchanger 15 by adjusting the opening degree according to the number of pulses given to the pulse motor.

[0017] The indoor heat exchanger 15 exchanges heat between the indoor air and the refrigerant circulating through the low-stage refrigerant circuit 10 in a low-stage side indoor unit 15a provided indoors.

[0018] The control valves 16a and 16b are valves that are manually switched between open and closed. The control valves 16a and 16b are used to switch whether or not the refrigerant flows through the indoor heat exchanger 15 by opening and closing them, and are used when flowing the refrigerant through the indoor heat exchanger 15 after the low-stage side indoor unit 15a is installed in a room, or when stopping the flow of the refrigerant into the indoor heat exchanger 15 when the low-stage side indoor unit 15a is removed.

[0019] The four-way valve 17 is a valve for switching the flow direction of the refrigerant in the low-level refrigerant circuit 10 under the control of the control device 50. Specifically, the four-way valve 17 switches the flow of the refrigerant so that the indoor heat exchanger 15 serves as an evaporator and the outdoor heat exchanger 11 serves as a condenser during cooling operation, and so that the indoor heat exchanger 15 serves as a condenser and the outdoor heat exchanger 11 serves as an evaporator during heating operation.

[0020] The high-stage refrigerant circuit 20 has a high-stage compressor 21, a water-refrigerant heat exchanger 22, an expansion valve 23 (second pressure reduction means) and a cascade heat exchanger 13, in which a refrigerant (second refrigerant) circulates to exchange heat with the refrigerant (first refrigerant) circulating through the low-stage refrigerant circuit 10.

[0021] The high-stage side compressor 21 is a compressor whose operating capacity can be varied according to, for example, the driving of a motor (not shown) whose rotation speed is controlled by an inverter under the control of the control device 50. The high-stage side compressor 21 is an example of a second compressor that compresses the refrigerant circulating in the high-stage refrigerant circuit 20 by being driven at a rotation speed controlled by the control device 50.

[0022] The water-refrigerant heat exchanger 22 exchanges heat between the refrigerant circulating through the high-temperature refrigerant circuit 20 and the water circulating through the water circuit 30 .

[0023] The expansion valve 23 is an electronic expansion valve that is driven by a pulse motor (not shown) under the control of the control device 50. The expansion valve 23 adjusts the flow rate of the refrigerant flowing into the cascade heat exchanger 13 by adjusting the opening degree according to the number of pulses given to the pulse motor.

[0024] The water circuit 30 has a circulation pump 31, an indoor heat exchanger 32 (second indoor heat exchanger), a heat storage device 33, a first flow path adjustment valve 34a to a third flow path adjustment valve 34c, and a bypass flow path 40, and water circulates in the water-refrigerant heat exchanger 22 to exchange heat with the refrigerant (second refrigerant) circulating through the high-temperature refrigerant circuit 20.

[0025] The circulation pump 31 is a pump whose operating capacity can be varied according to the driving of a motor (not shown) whose rotation speed is controlled by an inverter under the control of the control device 50. The circulation pump 31 is driven at a rotation speed controlled by the control device 50, thereby making it possible to adjust the flow rate of water circulating through the low-stage refrigerant circuit 10.

[0026] The indoor heat exchanger 32 exchanges heat between the indoor air and the water circulating through the water circuit 30 in a high-temperature side indoor unit 32a provided indoors.

[0027] The heat storage device 33 includes a heat storage material 33a that absorbs and stores heat by exchanging heat with the water circulating through the water circuit 30. In other words, the heat storage device 33 dissipates heat from the water circulating through the water circuit 30. The heat storage material 33a that absorbs the heat of the water through heat exchange is heated and stores the heat. In addition, a bypass flow path 40 is connected in parallel to the heat storage device 33. By passing the water circulating through the water circuit 30 through the bypass flow path 40, the water can be circulated without passing through the heat storage device 33.

[0028] The first flow path adjustment valve 34a to the third flow path adjustment valve 34c are adjustment valves whose opening degree can be adjusted by a pulse motor (not shown) under the control of the control device 50. The first flow path adjustment valve 34a to the third flow path adjustment valve 34c can adjust the flow path and flow rate of the water flowing through the heat storage device 33 and the bypass flow path 40 by adjusting the opening degree between a closed state and an open state of the valve according to the number of pulses given to the pulse motor.

[0029] The heat storage device 33 may not include the heat storage material 33a, and may be a heat dissipation device 33b (see FIG. 5) that simply dissipates heat from water. The heat storage device 33 (heat dissipation device 33b) may be provided on the high-stage refrigerant circuit side and connected to the high-stage refrigerant circuit by a bypass flow path so that the refrigerant in the high-stage refrigerant circuit can be bypassed (see FIG. 7). That is, the heat storage device 33 (heat dissipation device 33b) may be connected to at least one of the high-stage refrigerant circuit 20 or the water circuit 30 by a bypass flow path 40 so that the refrigerant in the high-stage refrigerant circuit 20 or the water in the water circuit 30 can be bypassed.

[0030] The control device 50 has a control unit 51 that controls the entire refrigeration cycle apparatus 1, a memory unit 52 that stores various information, and a temperature detection unit 53 (temperature detection means) that detects the temperatures of each part in the refrigeration cycle apparatus 1.

[0031] The control unit 51 receives the required capacity for the low-side indoor unit 15a, the high-side indoor unit 32a, the heat storage device 33, etc. during heating or cooling operation. The control unit 51 controls the operation of each part during heating or cooling operation according to the received required capacity for the low-side indoor unit 15a, the high-side indoor unit 32a, the heat storage device 33, etc. Note that the required capacity of the low-side indoor unit 15a is, for example, a value based on the difference between the temperature set by the user for the low-side indoor unit 15a and the room temperature. Also, the required capacity of the high-side indoor unit 32a is, for example, a value based on the difference between the temperature set by the user for the high-side indoor unit 32a and the room temperature. Also, the required capacity of the heat storage device 33 may be a surplus capacity calculated by subtracting the required capacity of the high-side indoor unit 32a from a threshold A (described in detail later).

[0032] For example, the control unit 51 determines the rotation speed of the low-side compressor 12 according to the total required capacity of the low-side indoor unit 15a, the high-side indoor unit 32a, and the heat storage device 33, and drives the low-side compressor 12 at the determined rotation speed. The control unit 51 also determines the rotation speed of the high-side compressor 21 according to the total required capacity of the high-side indoor unit 32a and the heat storage device 33, and drives the high-side compressor 21 at the determined rotation speed. The control unit 51 also adjusts the opening degree of the expansion valves 14a and 14b to adjust the flow rate of the refrigerant so that the refrigerant flowing through the indoor heat exchanger 15 and the cascade heat exchanger 13 can efficiently exchange heat. Specifically, the control unit 51 adjusts the expansion valve 14a based on the temperature of the refrigerant in the indoor heat exchanger 15 detected by the temperature detection unit 53, and adjusts the expansion valve 14b based on the temperature of the refrigerant in the cascade heat exchanger 13 detected by the temperature detection unit 53. For example, the control unit 51 adjusts the expansion valves 14a, 14b so that the degree of subcooling of the refrigerant flowing out of the indoor heat exchanger 15 and the cascade heat exchanger 13 in heating operation and the degree of superheating of the refrigerant flowing out of the indoor heat exchanger 15 and the cascade heat exchanger 13 in cooling operation are predetermined target values. Furthermore, the control unit 51 may adjust the opening degrees of the second flow path adjustment valve 34b and the third flow path adjustment valve 34c based on the ratio between the required capacity of the high-temperature side indoor unit 32a and the required capacity of the heat storage device 33 in a second heating operation described later, to adjust the ratio of water flowing through the heat storage device 33 and the bypass flow path 40.

[0033] Furthermore, during heating operation by the high-temperature side indoor unit 32a of the indoor heat exchanger 32, the control unit 51 switches between heating operations (first and third heating operations) in which the water in the water circuit 30 flows only through the bypass flow path 40 out of the heat storage device 33 and the bypass flow path 40, and heating operations (second heating operation) in which the water in the water circuit 30 flows through both the heat storage device 33 and the bypass flow path 40. Specifically, the control unit 51 switches between the above heating operations by switching between opening and closing the first flow path adjustment valve 34a to the third flow path adjustment valve 34c (details will be described later).

[0034] The memory unit 52 stores in advance a rotation speed table that determines the rotation speeds of the low-side compressor 12, the high-side compressor 21, etc., in accordance with the required capacity of the low-side indoor unit 15a, the high-side indoor unit 32a, the heat storage device 33, etc., during heating or cooling operation. The control unit 51 can determine the rotation speeds of the low-side compressor 12, the high-side compressor 21, etc., in accordance with the required capacity by referring to the rotation speed table stored in the memory unit 52. In addition, the memory unit 52 stores in advance information on various threshold values ​​used for switching control. In addition, the memory unit 52 may store in advance a target pressure for controlling the low-side compressor 12 and the high-side compressor 21 in accordance with the required capacity of the low-side indoor unit 15a, the high-side indoor unit 32a, the heat storage device 33, etc. Specifically, a target condensing pressure during heating operation and a target evaporating pressure during cooling operation may be stored. Even in this case, since the rotation speeds of the low-side compressor 12 and the high-side compressor 21 are adjusted according to the target pressure, it can be said that the rotation speeds of the low-side compressor 12 and the high-side compressor 21 are determined based on the required capacities of the low-side indoor unit 15a, the high-side indoor unit 32a, the heat storage device 33, etc.

[0035] The temperature detection unit 53 obtains detection values ​​of temperature sensors (not shown) provided in each part in the refrigeration cycle apparatus 1, and detects the temperature of each part. For example, the temperature detection unit 53 detects the temperature (first temperature) of the water flowing into the indoor heat exchanger 32 and the temperature (second temperature) of the heat storage material 33a. The temperature detection unit 53 may be a pressure detection unit that obtains detection values ​​of pressure sensors (not shown) provided in each part in the refrigeration cycle apparatus 1, and detects the pressure of each part, or may be a detection unit that detects both the temperature and pressure of each part.

[0036] Fig. 2 is a flowchart showing a control example of the refrigeration cycle device 1 according to the embodiment. Specifically, Fig. 2 is a flowchart showing a control example during heating operation by the high-side indoor unit 32a of the indoor heat exchanger 32, and the low-side indoor unit 15a may be stopped, but is in heating operation in this control example. In other words, the rotation speed of the low-side compressor 12 is determined according to the total required capacity of all of the low-side indoor unit 15a, the high-side indoor unit 32a, and the heat storage device 33, and it is assumed that the low-side compressor 12 is driven at that rotation speed.

[0037] 2, when the process is started, the control unit 51 closes the first flow path adjustment valve 34a and the second flow path adjustment valve 34b and opens the third flow path adjustment valve 34c to perform a heating operation (first heating operation) in which water in the water circuit 30 flows only through the bypass flow path 40. The control unit 51 also determines the rotation speed of the high-temperature side compressor 21 according to the sum of the required capacities of the high-temperature side indoor unit 32a and the heat storage device 33, and operates the high-temperature side compressor 21 at the determined rotation speed (S1).

[0038] Next, the control unit 51 judges whether the required capacity of the high-side indoor unit 32a is equal to or less than a predetermined threshold A (S2). This threshold A is set corresponding to the minimum required capacity that results in a compressor rotation speed that can ensure a sufficient compression ratio to ensure the reliability of the high-side compressor 21. In other words, if the required capacity of the high-side indoor unit 32a is not equal to or less than the threshold A, if the high-side compressor 21 is driven at a compressor rotation speed according to the required capacity, a sufficient compression ratio to ensure the reliability of the high-side compressor 21 can be ensured. Also, if the required capacity of the high-side indoor unit 32a is equal to or less than the threshold A, if the high-side compressor 21 is driven at a compressor rotation speed according to the required capacity, there is a possibility that a sufficient compression ratio to ensure the reliability of the high-side compressor 21 cannot be ensured.

[0039] If the required capacity of the high-temperature side indoor unit 32a is not equal to or less than the threshold A (S2: No), the control unit 51 returns the process to S1. If the required capacity of the high-temperature side indoor unit 32a is equal to or less than the threshold A (S2: Yes), the control unit 51 opens the second flow path adjustment valve 34b and the third flow path adjustment valve 34c (S3). As a result, the control unit 51 switches to a heating operation (second heating operation) in which water in the water circuit 30 flows to both the heat storage device 33 and the bypass flow path 40 (S4). The second heating operation is an operation in which the load on the high-temperature refrigerant circuit 20 is increased by flowing the refrigerant to the heat storage device 33, and a compressor rotation speed at which a compression ratio can be ensured is ensured.

[0040] Next, the control unit 51 judges whether the required capacity of the high temperature side indoor unit 32a is equal to or less than a predetermined threshold A (S5). This is the same process as S2, but since the processes from S4 to S6 are repeated as described below, the required capacity may change during that time. If the required capacity of the high temperature side indoor unit 32a is not equal to or less than the threshold A (S5: No), the control unit 51 returns the process to S1. As a result, if it is not equal to or less than the threshold A, the second heating operation is switched to the first heating operation.

[0041] When the required capacity of the high temperature side indoor unit 32a is equal to or less than the threshold A (S5: Yes), the control unit 51 determines whether or not the temperature difference between the temperature (first temperature) of the water flowing into the indoor heat exchanger 32 and the temperature (second temperature) of the heat storage device 33 is equal to or less than a first predetermined temperature based on the detection result of the temperature detection unit 53 (S6). Here, the first predetermined temperature is set to a value that is small enough to determine that the first temperature and the second temperature are close to each other, for example, 2.0 deg. When the temperature difference is not equal to or less than the first predetermined temperature (S6: No), the control unit 51 returns the process to S4 and continues the second heating operation.

[0042] When the temperature difference is equal to or lower than the first predetermined temperature (S6: Yes), it means that the water circulating through the water circuit 30 is hardly absorbing heat by the heat storage material 33a, and that heat storage in the heat storage material 33a is hardly occurring. Therefore, the control unit 51 stops the operation of the high-temperature side compressor 21, and opens the first flow path adjustment valve 34a and closes the second flow path adjustment valve 34b and the third flow path adjustment valve 34c (S7). As a result, the control unit 51 causes the water in the water circuit 30 to flow only through the heat storage device 33, and causes the heat storage device 33 to radiate the heat stored therein (heat the water by radiating heat), that is, switches to a heating operation (third heating operation) that utilizes the temperature of the heat storage device 33 (S8). The third heating operation is an operation that stops the high-temperature side compressor 21 by radiating the heat stored in the heat storage device 33, and enables heating without causing a problem with the compression ratio of the high-temperature side compressor 21.

[0043] Next, the control unit 51 judges whether the required capacity of the high temperature side indoor unit 32a is equal to or less than a predetermined threshold A (S9). This is the same process as S2, but since the processes from S8 to S10 are repeated as described below, the required capacity may change during that time. If the required capacity of the high temperature side indoor unit 32a is not equal to or less than the threshold A (S9: No), the control unit 51 returns the process to S1. As a result, if the required capacity is not equal to or less than the threshold A, the third heating operation is switched to the first heating operation.

[0044] When the required capacity of the high-temperature side indoor unit 32a is equal to or lower than the threshold A (S9: Yes), the control unit 51 judges whether or not the temperature difference between the temperature (first temperature) of the water flowing into the indoor heat exchanger 32 and the temperature (second temperature) of the heat storage device 33 is equal to or higher than a second predetermined temperature based on the detection result of the temperature detection unit 53 (S10). Here, the second predetermined temperature is set to a value that is large enough to judge that the first temperature and the second temperature have diverged, for example, 5 degrees. When the temperature difference is not equal to or higher than the second predetermined temperature (S10: No), the control unit 51 returns the process to S8 and continues the third heating operation. When the temperature difference is equal to or higher than the second predetermined temperature (S10: Yes), it means that the heat stored in the heat storage material 33a has been used sufficiently. Therefore, the control unit 51 starts the operation of the high-temperature side compressor 21 (S11) and returns the process to S1.

[0045] 3 is a timing chart showing an example of the operation of the refrigeration cycle device according to the embodiment (horizontal axis indicates times t0 to t13, period T1: times t0 to t1, period T2: times t1 to t2, ..., period T13: times t12 to t13). In the timing chart in FIG. 3, from the top, the rotation speed of the low-stage side compressor 12, the required capacity of the low-stage side indoor unit 15a, the rotation speed of the high-stage side compressor 21, the total required capacity of the high-stage side indoor unit 32a and the heat storage device 33, the required capacity of the high-stage side indoor unit 32a, the temperature of the heat storage device 33, the required capacity of the heat storage device 33, and the opening and closing of the first flow control valve 34a, the second flow control valve 34b, and the third flow control valve 34c are shown on the vertical axis.

[0046] As shown in Fig. 3, during the initial period (T1 to T3), the control unit 51 closes the first flow path adjustment valve 34a and the second flow path adjustment valve 34b and opens the third flow path adjustment valve 34c to perform heating operation (first heating operation) in which water in the water circuit 30 flows only through the bypass flow path 40. At this time, the water circulating through the water circuit 30 does not dissipate heat on the heat storage device 33 side, but dissipates heat only on the high temperature side indoor unit 32a side. As a result, during the period (T1 to T3), the room is efficiently heated and the room warms up, and the required capacity of the high temperature side indoor unit 32a decreases.

[0047] Next, at time t3, the required capacity of the high-temperature side indoor unit 32a falls below the threshold A, that is, falls below the minimum required capacity at which the compressor rotation speed can ensure the compression ratio, so the control unit 51 opens the second flow path adjustment valve 34b and the third flow path adjustment valve 34c. As a result, the control unit 51 performs heating operation in which the water in the water circuit 30 flows to both the heat storage device 33 and the bypass flow path 40, and the load on the high-temperature refrigerant circuit 20 increases by the amount of heat dissipated by the water circulating in the water circuit 30 in the heat storage device 33. Therefore, even if the required capacity of the high-temperature side indoor unit 32a continues to fall further below the threshold A, the control unit 51 can ensure the compressor rotation speed at which the compression ratio can be ensured, and can prevent the reliability of the high-temperature side compressor 21 from deteriorating.

[0048] The control device 50 varies the threshold value A based on the pressure state (condensation pressure) of the refrigerant in the low-stage refrigerant circuit 10.

[0049] FIG. 4 is a ph diagram for explaining the refrigeration cycle of the refrigeration cycle device 1 according to the embodiment. In FIG. 4, the refrigeration cycle C1 is a refrigeration cycle of the low-stage refrigerant circuit 10, and the graph G1 shows the saturated liquid line and saturated vapor line of the refrigerant of the low-stage refrigerant circuit 10. Similarly, the refrigeration cycle C2 is a refrigeration cycle of the high-stage refrigerant circuit 20, and the graph G2 shows the saturated liquid line and saturated vapor line of the refrigerant of the high-stage refrigerant circuit 20. As shown in FIG. 4, when the condensation pressure in the refrigeration cycle C1 rises from the dotted line position C1a to the solid line position, the evaporation pressure in the refrigeration cycle C2 also rises from the dotted line position C2a to the solid line position. As a result, the compression ratio in the refrigeration cycle C2 decreases.

[0050] Therefore, as the condensing pressure in the refrigeration cycle C1 increases, the rotation speed required to ensure the compression ratio in the high-stage compressor 21 increases, and therefore the value of the threshold A is increased according to the increase in the condensing pressure in the refrigeration cycle C1. The condensing pressure in the refrigeration cycle C1 is obtained, for example, by detecting the condensing temperature in the cascade heat exchanger 13 of the refrigerant circulating in the low-stage refrigerant circuit 10 and converting it into a saturation pressure. Alternatively, the condensing pressure may be detected by providing a pressure sensor in the high-pressure section of the low-stage refrigerant circuit 10, i.e., between the outlet of the low-stage compressor 12 and the expansion valve 14a or 14b. The control unit 51 then obtains the value of the threshold A corresponding to the condensing pressure by referring to a table showing the correspondence between the condensing pressure and the threshold A.

[0051] Furthermore, the control device 50 may set the required capacity of the heat storage device 33 as the surplus capacity calculated by subtracting the required capacity of the high-temperature side indoor unit 32a from the threshold value A. In this case, in the refrigeration cycle device 1, the surplus heating capacity that would be generated when the high-temperature side compressor 21 is operated at a rotation speed for ensuring the compression ratio can be stored in the heat storage device 33, and operation in which the high-temperature side compressor 21 has a low compression ratio can be avoided without wasting power.

[0052] 3, during the period T4 to T8, the heating operation is continued in which the water in the water circuit 30 flows through both the heat storage device 33 and the bypass flow path 40, thereby increasing the temperature of the heat storage device 33. As a result, the temperature of the heat storage device 33 increases until the temperature difference between the temperature of the water flowing into the indoor heat exchanger 32 (first temperature) and the temperature of the heat storage device 33 (second temperature) becomes equal to or less than a predetermined threshold value (time t8).

[0053] When the temperature difference between the first temperature and the second temperature becomes equal to or less than a predetermined threshold, the control unit 51 stops the operation of the high-side compressor 21, and switches to a heating operation using the temperature of the heat storage device 33 by opening the first flow control valve 34a and closing the second flow control valve 34b and the third flow control valve 34c. At this time, the control unit 51 replaces the required capacity of the high-side indoor unit 32a with 0. That is, when determining the rotation speed of the low-side compressor 12 according to the total of the required capacities of the low-side indoor unit 15a, the high-side indoor unit 32a, and the heat storage device 33, the control unit 51 sets the required capacity of the high-side indoor unit 32a to 0. During the heating operation using the temperature of the heat storage device 33, the high-side indoor unit 32a performs heating using the heat stored in the heat storage device 33, and the high-side compressor 21 is stopped. Therefore, it is not necessary to determine the rotation speed of the low-side compressor 12 based on the high-side refrigerant circuit 20. Therefore, by replacing the required capacity of the high-stage side indoor unit 32a with 0 as described above, the control unit 51 can determine the rotation speed of the low-stage side compressor 12 based only on the required capacity of the low-stage side indoor unit 15a. This allows the control unit 51 to set the rotation speed of the low-stage side compressor 12 to an appropriate value suited to the heating operation that utilizes the temperature of the heat storage device 33, and highly reliable operation can be achieved throughout the entire cascade refrigeration cycle.

[0054] Next, when the temperature difference between the temperature of the water flowing into the indoor heat exchanger 32 (first temperature) and the temperature of the heat storage device 33 (second temperature) becomes equal to or greater than a predetermined threshold (time t12), the control unit 51 starts operation of the high-temperature side compressor 21 and switches to heating operation with the first flow path adjustment valve 34a closed and the second flow path adjustment valve 34b and the third flow path adjustment valve 34c open.

[0055] Fig. 5 is an explanatory diagram for explaining a first modified example of the refrigeration cycle apparatus 1 according to the embodiment. As shown in Fig. 5, in a water circuit 30a, the heat storage device 33 may be replaced with a heat dissipation device 33b that only dissipates heat.

[0056] Fig. 6 is a flowchart showing a control example of the first modified example of the refrigeration cycle device according to the embodiment. As shown in Fig. 6, when the process is started, the control unit 51 closes the first flow path adjustment valve 34a and the second flow path adjustment valve 34b and opens the third flow path adjustment valve 34c to perform a heating operation (first heating operation) in which the water in the water circuit 30a flows only through the bypass flow path 40. The control unit 51 also determines the rotation speed of the high-temperature side compressor 21 according to the total required capacity of the high-temperature side indoor unit 32a and the heat radiator 33b, and operates the high-temperature side compressor 21 at the determined rotation speed (S21).

[0057] Next, the control unit 51 judges whether the required capacity of the high temperature side indoor unit 32a is equal to or less than a predetermined threshold A (S22). If it is not equal to or less than the threshold A (S22: No), the control unit 51 returns the process to S21. If it is equal to or less than the threshold A (S22: Yes), the control unit 51 opens the second flow path adjustment valve 34b and the third flow path adjustment valve 34c (S23). As a result, the control unit 51 switches to a heating operation (second heating operation) in which water in the water circuit 30a flows to both the heat dissipation device 33b and the bypass flow path 40 (S24).

[0058] Next, the control unit 51 determines whether the required capacity of the high temperature side indoor unit 32a is equal to or less than a predetermined threshold A (S25). If it is not equal to or less than the threshold A (S25: No), the control unit 51 returns the process to S21. As a result, if it is not equal to or less than the threshold A, the second heating operation is switched to the first heating operation. If it is equal to or less than the threshold A (S25: Yes), the control unit 51 returns the process to S24 and continues the second heating operation.

[0059] Fig. 7 is an explanatory diagram illustrating a second modified example of the refrigeration cycle apparatus 1 according to the embodiment. As shown in Fig. 7, the heat dissipation device 33b may be provided in the high-stage refrigerant circuit 20a and connected to the high-stage refrigerant circuit 20a via a bypass passage 40a so as to be able to bypass the refrigerant in the high-stage refrigerant circuit 20a.

[0060] The first flow path adjustment valve 35a to the third flow path adjustment valve 35c are adjustment valves whose opening degree can be adjusted by a pulse motor (not shown) under the control of the control device 50. The first flow path adjustment valve 35a to the third flow path adjustment valve 35c are capable of adjusting the flow rate of the refrigerant flowing through the heat dissipation device 33b and the bypass flow path 40a by adjusting the opening degree according to the number of pulses given to the pulse motor.

[0061] Fig. 8 is a flowchart showing a control example of the second modification of the refrigeration cycle device 1 according to the embodiment. As shown in Fig. 8, when the process is started, the control unit 51 closes the first flow path adjustment valve 35a and the second flow path adjustment valve 35b and opens the third flow path adjustment valve 35c to perform a heating operation (first heating operation) in which the refrigerant in the high-stage refrigerant circuit 20a flows only through the bypass flow path 40a. The control unit 51 also determines the rotation speed of the high-stage compressor 21 according to the total required capacity of the high-stage indoor unit 32a and the heat radiator 33b, and operates the high-stage compressor 21 at the determined rotation speed (S31).

[0062] Next, the control unit 51 judges whether the required capacity of the high-temperature side indoor unit 32a is equal to or less than a predetermined threshold A (S32). If it is not equal to or less than the threshold A (S32: No), the control unit 51 returns the process to S31. If it is equal to or less than the threshold A (S32: Yes), the control unit 51 opens the second flow path adjustment valve 35b and the third flow path adjustment valve 35c (S33). As a result, the control unit 51 switches to a heating operation (second heating operation) in which the refrigerant in the high-temperature refrigerant circuit 20a flows to both the heat radiator 33b and the bypass flow path 40a (S34). Note that, in the second heating operation, the control unit 51 may adjust the opening degree of the second flow path adjustment valve 35b and the third flow path adjustment valve 35c based on the ratio between the required capacity of the high-temperature side indoor unit 32a and the required capacity of the heat radiator 33b, and adjust the ratio of the second refrigerant flowing to the heat radiator 33b and the bypass flow path 40a.

[0063] Next, the control unit 51 determines whether the required capacity of the high temperature side indoor unit 32a is equal to or less than a predetermined threshold A (S35). If it is not equal to or less than the threshold A (S35: No), the control unit 51 returns the process to S31. As a result, if it is not equal to or less than the threshold A, the second heating operation is switched to the first heating operation. If it is equal to or less than the threshold A (S35: Yes), the control unit 51 returns the process to S34 and continues the second heating operation.

[0064] As described above, the refrigeration cycle device 1 includes the low-stage refrigerant circuit 10, the high-stage refrigerant circuit 20, the water circuit 30, the heat radiating device (heat storage device 33, heat radiating device 33b), the bypass flow path, the control valves (34a, 34b, 34c, 35a, 35b, 35c), and the control device 50. The low-stage refrigerant circuit 10 includes an outdoor heat exchanger 11, a low-stage compressor 12, a cascade heat exchanger 13, expansion valves 14a, 14b, and an indoor heat exchanger 15, and a first refrigerant circulates through the low-stage refrigerant circuit 10. The high-stage refrigerant circuit 20 includes a high-stage compressor 21, a water-refrigerant heat exchanger 22, an expansion valve 23, and a cascade heat exchanger 13, and a second refrigerant that exchanges heat with the first refrigerant in the cascade heat exchanger 13 circulates through the high-stage refrigerant circuit 20. The water circuit 30 has a circulation pump 31, an indoor heat exchanger 32, and a water-refrigerant heat exchanger 22, and water that exchanges heat with the second refrigerant circulates in the water-refrigerant heat exchanger 22. The heat dissipation device is connected to at least one of the high-stage refrigerant circuit 20 and the water circuit 30, and dissipates heat from the second refrigerant or the water. The bypass flow path bypasses the second refrigerant or the water without passing through the heat dissipation device. The adjustment valve adjusts the amount of the second refrigerant or the water flowing through the heat dissipation device and the bypass flow path 40. The control device 50 controls the low-stage side compressor 12, the expansion valves 14a, 14b, the high-stage side compressor 21, the expansion valve 23, the circulation pump 31, and the adjustment valve. During heating operation by the high-temperature side indoor unit 32a of the indoor heat exchanger 32, the control device 50 switches between a first heating operation in which the second refrigerant or water is caused to flow only through the bypass flow path 40 out of the heat radiator and the bypass flow path 40, or a second heating operation in which the second refrigerant or water is caused to flow through both the heat radiator and the bypass flow path 40. In the second heating operation, the control device 50 determines the rotation speed of the high-temperature side compressor 21 based on the required capacity of the high-temperature side indoor unit 32a of the indoor heat exchanger 32 and the heat radiator.

[0065] As a result, in the refrigeration cycle device 1, during the second heating operation, the load on the high-stage refrigerant circuit 20 increases by the amount of heat dissipated by the heat dissipation device, so that even if the high-stage compressor 21 is operated at a rotation speed that ensures the compression ratio, the capacity of the high-stage indoor unit 32a can be prevented from becoming excessive, and the reliability of the high-stage compressor 21 can be prevented from deteriorating without compromising user comfort.

[0066] Moreover, the heat dissipation device is a heat storage device 33 having a heat storage material 33a that exchanges heat with the second refrigerant or water and dissipates heat. During heating operation by the high-temperature side indoor unit 32a of the indoor heat exchanger 32, the control device 50 further switches to a third heating operation in which the second refrigerant or water flows only through the heat storage device 33 out of the heat storage device 33 and the bypass flow path 40, and the heat stored in the heat storage device 33 is dissipated. As a result, in the refrigeration cycle device 1, the heat stored in the heat storage device 33 can be effectively used, and the compression ratio of the high-temperature side compressor 21 can be ensured without wasting power.

[0067] Furthermore, the heat storage device 33 is provided in the water circuit 30, and the control device 50 stops the high-temperature side compressor 21 in the third heating operation. As a result, since the high-temperature side compressor 21 is stopped in the third heating operation in which the heat stored in the heat storage device 33 is released, a problem with the compression ratio in the high-temperature side compressor 21 does not occur, and deterioration of the reliability of the high-temperature side compressor 21 can be suppressed.

[0068] The low-stage refrigerant circuit 10 also has a four-way valve 17 that switches the path through which the first refrigerant circulates between heating operation and cooling operation by the low-stage indoor unit 15a of the indoor heat exchanger 15 under the control of the control device 50. When the low-stage indoor unit 15a of the indoor heat exchanger 15 is in heating operation and the heating operation by the high-stage indoor unit 32a of the indoor heat exchanger 32 is the first heating operation, the control device 50 switches from the first heating operation to the second heating operation when the required capacity of the high-stage indoor unit 32a of the indoor heat exchanger 32 becomes less than a predetermined value. As a result, the refrigeration cycle device 1 can avoid an operation in which the high-stage compressor 21 has a low compression ratio by switching to the second heating operation when the required capacity of the high-stage indoor unit 32a is less than a predetermined value and the high-stage compressor 21 is likely to have a low compression ratio.

[0069] Furthermore, the control device 50 changes the above-mentioned predetermined value based on the condensation pressure of the first refrigerant in the low-stage refrigerant circuit 10. This allows the refrigeration cycle device 1 to appropriately switch to the second heating operation under operating conditions where the high-stage side compressor 21 has a low compression ratio due to the condensation pressure of the first refrigerant, and makes it possible to avoid an operation where the high-stage side compressor 21 has a low compression ratio.

[0070] Furthermore, in the second heating operation, the control device 50 adjusts the openings of the second flow path adjustment valve 34b and the third flow path adjustment valve 34c based on the ratio between the required capacity of the high-temperature side indoor unit 32a of the indoor heat exchanger 32 and the required capacity of the heat radiator (heat storage device 33, heat radiator 33b), and adjusts the ratio of the second refrigerant or water flowing through the heat radiator and the bypass flow path 40. This allows the refrigeration cycle device 1 to circulate the refrigerant or water with an appropriate balance according to the required capacity.

[0071] In the refrigeration cycle apparatus 1, the required capacity of the heat dissipation device 33b is a surplus capacity calculated by subtracting the required capacity of the high-temperature side indoor unit 32a of the indoor heat exchanger 32 from the above-mentioned predetermined value. This allows the refrigeration cycle apparatus 1 to store the surplus heating capacity of the high-temperature side indoor unit 32a in the heat storage device 33, and can avoid operation with a low compression ratio of the high-temperature side compressor 21 without wasting power.

[0072] The refrigeration cycle apparatus 1 further includes a temperature detection unit 53 that detects a first temperature of the water flowing into the indoor heat exchanger 32 and a second temperature of the heat storage device 33. When the temperature difference between the first temperature and the second temperature becomes less than a predetermined temperature difference in the second heating operation, the control device 50 switches to the third heating operation. This makes it possible to prevent the refrigeration cycle apparatus 1 from being unable to release heat from the water to the heat storage material 33a and thus preventing the water from being excessively heated.

[0073] Furthermore, the control device 50 determines the rotation speed of the low-stage side compressor 12 based on the sum of the required capacity of the low-stage side indoor unit 15a of the indoor heat exchanger 15, the required capacity of the high-stage side indoor unit 32a of the indoor heat exchanger 32, and the required capacity of the heat radiator 33b. Furthermore, in the third heating operation, the required capacity of the high-stage side indoor unit 32a of the indoor heat exchanger 32 is replaced with 0 to determine the rotation speed of the low-stage side compressor 12. This allows the refrigeration cycle device 1 to set the rotation speed of the low-stage side compressor 12 to an appropriate value suited to the second heating operation, and enables highly reliable operation of the entire two-stage refrigeration cycle. [Explanation of symbols]

[0074] 1...Refrigeration cycle device 10...Low source refrigerant circuit 11...Outdoor heat exchanger 11a...Outdoor unit 12...Low pressure compressor 13…Cascade heat exchanger 14a, 14b, 23...Expansion valve 15...Indoor heat exchanger 15a…Low-side indoor unit 16a, 16b...Operating valve 17...Four-way valve 20, 20a...High-temperature refrigerant circuit 21...High pressure compressor 22…Water refrigerant heat exchanger 30, 30a, 30b…water circuit 31...Circulation pump 32…Indoor heat exchanger 32a…High-side indoor unit 33...Heat storage device 33a...Heat storage material 33b...Heat dissipation device 34a, 35a...First flow path adjustment valve 34b, 35b...Second flow path adjustment valve 34c, 35c...Third flow control valve 40, 40a...Bypass flow path 50...Control device 51...Control unit 52...Storage section 53...Temperature detection section A…Threshold C1, C2... Refrigeration cycle G1, G2…Graph t0~t13…Time T1~T13…Period

Claims

1. a low-level refrigerant circuit including an outdoor heat exchanger, a first compressor, a cascade heat exchanger, a first pressure reducing means, and a first indoor heat exchanger, in which a first refrigerant circulates; a high-temperature refrigerant circuit including a second compressor, a water-refrigerant heat exchanger, a second pressure reducing means, and the cascade heat exchanger, in which a second refrigerant that exchanges heat with the first refrigerant in the cascade heat exchanger is circulated by driving the second compressor; a water circuit including a circulation pump, a second indoor heat exchanger, and the water-refrigerant heat exchanger, in which water circulates to exchange heat with the second refrigerant in the water-refrigerant heat exchanger; a heat storage device having a heat storage material and connected to the water circuit to exchange heat between the heat storage material and the water; a bypass flow path that bypasses the water without passing through the heat storage device; a flow path switching valve for switching a flow path of the water flowing between the heat storage device and the bypass flow path; a control device that controls the first compressor, the first pressure reducing means, the second compressor, the second pressure reducing means, the circulation pump, and the flow path switching valve, the control device, during a heating operation by the indoor unit of the second indoor heat exchanger, switches to a first heating operation in which the water is caused to flow only through the bypass flow path out of the heat storage device and the bypass flow path, a second heating operation in which the water is caused to flow both through the heat storage device and the bypass flow path, or a third heating operation in which the water is caused to flow only through the heat storage device out of the heat storage device and the bypass flow path, and heat stored in the heat storage device is released to heat the water, and in the second heating operation, determines a rotation speed of the second compressor based on a required capacity of the indoor unit of the second indoor heat exchanger and the heat storage device, The control device includes: In the first heating operation and the second heating operation, the second compressor is driven so that the second refrigerant is circulated through the high-temperature refrigerant circuit; In the third heating operation, the second compressor is stopped so that the second refrigerant is not circulated in the high-temperature refrigerant circuit. A refrigeration cycle device characterized by:

2. The low-temperature refrigerant circuit has a switching valve that switches a path through which the first refrigerant circulates between heating operation and cooling operation by the indoor unit of the first indoor heat exchanger under the control of the control device, the control device, when the heating operation by the indoor unit of the first indoor heat exchanger is in the heating operation and the heating operation by the indoor unit of the second indoor heat exchanger is the first heating operation, switches from the first heating operation to the second heating operation when a required capacity of the indoor unit of the second indoor heat exchanger becomes less than a predetermined value; 2. The refrigeration cycle device according to claim 1.

3. The control device changes the predetermined value based on a condensation pressure of the first refrigerant in the low-level refrigerant circuit.

3. The refrigeration cycle device according to claim 2.

4. the flow path switching valve is an adjustment valve capable of adjusting an amount of the water flowing through the heat storage device and the bypass flow path, The control device adjusts an opening degree of the regulating valve based on a ratio between a required capacity of the indoor unit of the second indoor heat exchanger and a required capacity of the heat storage device in the second heating operation, and adjusts a ratio of the water flowing into the heat storage device and the bypass flow path.

2. The refrigeration cycle device according to claim 1.

5. The required capacity of the heat storage device is a surplus capacity calculated by subtracting the required capacity of the indoor unit of the second indoor heat exchanger from the predetermined value.

3. The refrigeration cycle device according to claim 2.

6. The system further includes a temperature detection means for detecting a first temperature of the water flowing into the second indoor heat exchanger and a second temperature of the heat storage device, When a temperature difference between the first temperature and the second temperature becomes less than a predetermined temperature difference in the second heating operation, the control device switches to the third heating operation.

2. The refrigeration cycle device according to claim 1.

7. the control device determines a rotation speed of the first compressor based on a sum of a required capacity of an indoor unit of the first indoor heat exchanger, a required capacity of an indoor unit of the second indoor heat exchanger, and a required capacity of the heat storage device; In the third heating operation, the rotation speed of the first compressor is determined by replacing the required capacity of the indoor unit of the second indoor heat exchanger with 0.

2. The refrigeration cycle device according to claim 1.

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