Refrigerant circuit system

Abstract

[Problem] To propose a refrigerant circuit system capable of switching a refrigeration cycle in accordance with the necessary heating capacity. [Solution] A binary refrigerant circuit system using two types of refrigerants in which a high-temperature-side circuit (40) provided with a high-temperature-side compressor (69), a high-temperature-side heat exchanger (70), and a high-temperature-side expansion mechanism (71), and a low-temperature-side circuit (30) provided with a high-temperature-side expansion mechanism (71) are connected via a cascade heat exchanger (67), said high-temperature-side circuit (40) being provided with a high-temperature-side compressor (69), a high-temperature-side heat exchanger (70), and a high-temperature-side expansion mechanism (71). The refrigerant circuit system is provided with a low-temperature-side circuit (30) provided with a low-temperature-side compressor (51), a low-temperature-side utilization heat exchanger (68), low-temperature-side expansion mechanisms (54, 55), and a low-temperature-side heat source heat exchanger (52), and is provided with a switching circuit (80) for switching between a first cycle in which refrigerant flows from the low-temperature-side compressor (51) to the cascade heat exchanger (67) and a second cycle in which refrigerant flows from the low-temperature-side utilization heat exchanger (68) to the cascade heat exchanger (67). In the second cycle, the refrigerant flowing from the low-temperature-side compressor (51) to the low-temperature-side utilization heat exchanger (68) is caused to flow to the cascade heat exchanger (67).

Description

Technical Field

[0001] This disclosure relates to a refrigerant circuit system. Background Technology

[0002] Patent document 1 discloses a refrigeration cycle device that has a high-element refrigerant circuit using propane, a low-element refrigerant circuit using carbon dioxide, and a heat medium circuit, which can achieve high efficiency in both cooling and heating.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 7146117 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] For example, to further improve the cooling or heating capacity of the refrigeration cycle device using Patent Document 1, it is necessary to increase the amount of refrigerant. However, flammable spontaneous refrigerants, such as propane, are flammable, thus limiting their use. Therefore, in refrigeration cycles using flammable spontaneous refrigerants, for example, it is impossible to fill the refrigerant to a certain quantity, thus limiting the capacity.

[0008] This disclosure proposes a refrigerant loop system capable of switching the refrigeration cycle according to the required heating capacity.

[0009] Methods for solving problems

[0010] The refrigerant circuit system disclosed herein is a binary refrigerant circuit system formed by connecting a high-element-side circuit 40 using a first refrigerant and a low-element-side circuit 30 using a second refrigerant via a cascaded heat exchanger 67. The high-element-side circuit 40 includes a high-element-side compressor 69, a high-element-side utilization heat exchanger 70, and a high-element-side expansion mechanism 71. The low-element-side circuit 30 includes a low-element-side compressor 51, a low-element-side utilization heat exchanger 68, low-element-side expansion mechanisms 54 and 55, and a low-element-side heat source heat exchanger 52. The refrigerant circuit system has a switching loop 80 for a first cycle and a second cycle. In the first cycle, refrigerant flows from the low-element-side compressor 51 to the cascaded heat exchanger 67. In the second cycle, refrigerant flowing from the low-element-side compressor 51 to the low-element-side utilization heat exchanger 68 flows back to the cascaded heat exchanger 67. In this configuration, the refrigeration cycle can be switched according to the required heating capacity.

[0011] Here, in the refrigerant circuit system disclosed herein, the high-element heat exchanger 70 and the low-element heat exchanger 68 are water heat exchangers, and the refrigerant circuit system also includes a heat medium circuit 50, which includes heat medium piping 85, 86, 87, 89, a pump 84, and a tank 82.

[0012] Here, in the refrigerant circuit system disclosed herein, the low-element side circuit 30 further includes a bypass flow path 811, a first stopcock valve 65, and a second stopcock valve 66.

[0013] Here, in the refrigerant circuit system of this disclosure, when it is determined that the necessary heating capacity is not achieved when using the first cycle for heating operation, the system switches to the second cycle. In this case, the switching of the refrigeration cycle can be performed by comparing the current heating capacity with the necessary heating capacity.

[0014] Here, in the refrigerant loop system disclosed herein, the necessary heating capacity is determined based on three factors: the user-set target hot water outlet temperature, the current inlet water temperature, and the water flow rate.

[0015] Here, the refrigerant circuit system of this disclosure can switch to the second cycle when the speed of the compressor 69 on the high-side is above the upper limit or a certain threshold and the pump command value for controlling the flow of the heat medium is below a certain threshold, but the temperature of the first heat medium from the heat medium piping 87 has not reached the target value.

[0016] Furthermore, the refrigerant circuit system of this disclosure switches to the second cycle when it determines that the rotational speed of the high-side compressor 69 is above the upper limit or a certain threshold, and the heating capacity estimated based on the inlet water temperature, outlet hot water temperature, and pump command value has not reached the target capacity, and the heating capacity has not increased for a certain period of time. In this case, it can prevent switching to the refrigeration cycle before the heating capacity is fully increased.

[0017] Furthermore, in the refrigerant circuit system of this disclosure, the pump command value used in determining the switch from the first cycle to the second cycle is changed according to the length of the heat medium piping. In this case, the same flow rate of water can flow even when the length of the heat medium piping is different.

[0018] Furthermore, when an anomaly occurs in the high-side circuit 40, the refrigerant circuit system of this disclosure operates for heating only through the low-side circuit 30. In this case, even if the high-side circuit cannot be used, a certain level of heating capacity can be ensured solely through the low-side circuit.

[0019] Furthermore, the refrigerant circuit system of this disclosure reports an anomaly when an anomaly occurs in the high-side circuit 40. In this case, the occurrence of the anomaly can be confirmed even when not on-site, and a determination can be made on the user side to operate the heating system solely through the low-side circuit.

[0020] Furthermore, in the refrigerant circuit system disclosed herein, the high-element side circuit 40 is installed indoors. In this case, even if a flammable refrigerant is used in the high-element side circuit, the filling amount limit for the flammable refrigerant can be met, and it can be installed even in an indoor environment where only a certain degree of ventilation is possible.

[0021] Furthermore, in the refrigerant circuit system disclosed herein, both refrigerants are natural refrigerants.

[0022] Furthermore, the refrigerant circuit system of this disclosure uses propane in the high-element side circuit 40 and carbon dioxide in the low-element side circuit 30.

[0023] Furthermore, in the refrigerant circuit system of this disclosure, the heat medium supplied from the pump 84 flows in the heat medium circuit 50 in the order of the low-element side using the heat exchanger 68 and the high-element side using the heat exchanger 70. In this case, the refrigeration cycle corresponding to the necessary heating capacity can be switched by switching the switching circuit 80 without switching the flow path on the heat medium circuit 50 side.

[0024] Furthermore, the refrigerant circuit system disclosed herein also includes a four-way switching valve 53, which is used to switch between heating and cooling operation. Attached Figure Description

[0025] Figure 1 This is a refrigerant circuit diagram illustrating a structural example of the refrigerant circuit system of this embodiment.

[0026] Figure 2 This is a thermal medium circuit diagram illustrating a structural example of the thermal medium circuit in this embodiment.

[0027] Figure 3 This is a refrigerant circuit diagram showing the flow of refrigerant during heating operation in the first cycle of this embodiment.

[0028] Figure 4 (a) is the pressure-enthalpy curve during heating operation in the first cycle, and (b) is the pressure-enthalpy curve in the high-element side loop.

[0029] Figure 5 This is a refrigerant circuit diagram showing the flow of refrigerant during heating operation in the second cycle of this embodiment.

[0030] Figure 6 The diagrams are pressure-enthalpy curves during heating operation in the second cycle. (a) is the pressure-enthalpy curve in the high-element loop, and (b) is the pressure-enthalpy curve in the low-element loop.

[0031] Figure 7A This is a block diagram illustrating a structural example of the main equipment in this embodiment.

[0032] Figure 7B This is a flowchart of the switching from the first cycle to the second cycle during heating operation. (a) shows an example of the case where the upper limit of the speed of the high-side compressor is used, and (b) shows an example of the case where the threshold of the speed of the high-side compressor is used.

[0033] Figure 7C This is a flowchart of the switching from the second cycle to the first cycle during heating operation. (a) shows an example of using the necessary heating capacity, and (b) shows an example of using the target hot water temperature.

[0034] Figure 7D This is a flowchart of the refrigerant circuit system startup process in this embodiment.

[0035] Figure 8A This is a schematic refrigerant circuit diagram of the switching circuit in the refrigerant circuit system of Variation Example 1.

[0036] Figure 8B This is a schematic refrigerant circuit diagram of the switching circuit in the refrigerant circuit system of Variation Example 2.

[0037] Figure 8C This is a schematic refrigerant circuit diagram of the switching circuit in the refrigerant circuit system of Variation Example 3.

[0038] Figure 9A This is a schematic diagram of the heat medium circuit in the refrigerant circuit system of Variation Example 4.

[0039] Figure 9B This is a schematic diagram of the heat medium circuit in the refrigerant circuit system of Modified Example 5. Detailed Implementation

[0040] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings.

[0041] <Structure of Refrigerant Circuit System>

[0042] Figure 1 This is a refrigerant circuit diagram illustrating a structural example of the refrigerant circuit system of this embodiment.

[0043] The refrigerant circuit system 1 of this embodiment is, for example, a hot water supply system. The hot water supply system supplies hot water to a target. In this embodiment, the target includes hot water supply objects such as faucets, showers, and bathtubs, and heating devices that use hot water. The refrigerant circuit system 1 of this embodiment is, for example, composed of an outdoor unit 10 installed outdoors and an indoor unit 20 installed indoors. The outdoor unit 10 has a low-current side circuit 30, a portion of which is connected to the indoor unit 20. The indoor unit 20 has a high-current side circuit 40 and a heat transfer medium circuit 50. The refrigerant circuit system 1 of this embodiment may also include a control unit 100 (see reference 100). Figure 7A ).

[0044] The first refrigerant filling the high-level circuit 40 and the second refrigerant filling the low-level circuit 30 are, for example, natural refrigerants. The low-level circuit 30 is, for example, filled with carbon dioxide, and the high-level circuit 40 is, for example, filled with propane.

[0045] The low-level side circuit 30 includes a low-level side compressor 51, a low-level side heat source heat exchanger 52, a four-way switching valve 53, a first expansion valve 54, shut-off valves 61, 62, 63, and 64, a first stopcock valve 65, a second stopcock valve 66, a cascaded heat exchanger 67, and a low-level side utilization heat exchanger 68. Furthermore, the low-level side circuit 30 includes a switching circuit 80 that directs refrigerant flow through the cascaded heat exchanger 67 instead of the low-level side utilization heat exchanger 68. The low-level side circuit 30 may also include a second expansion valve 55, a liquid receiver 56, and check valves 57, 58, 59, and 60.

[0046] Furthermore, the low-level side circuit 30 is not limited to the structure described above. For example, the low-level side circuit 30 may also be configured to include a filter, a radiator, an oil separator, etc. It may also be configured to include a pressure sensor, a high-pressure switch as a protection detector, etc.

[0047] The low-side compressor 51 draws in refrigerant from the suction side and discharges the compressed refrigerant from the discharge side. The low-side compressor 51 may also have a gas-liquid separator on its suction side to separate the refrigerant into gas and liquid. The discharge side of the low-side compressor 51 is connected to the first port P1 of the four-way switching valve 53, and the suction side of the low-side compressor 51 is connected to the third port P3 of the four-way switching valve 53.

[0048] The low-side heat source heat exchanger 52 exchanges heat between the refrigerant and the external gas. During heating operation, the low-side heat source heat exchanger 52 functions as an evaporator. The low-side heat source heat exchanger 52 can also be configured to include an outdoor fan.

[0049] The four-way switching valve 53 has a first valve port P1, a second valve port P2, a third valve port P3, and a fourth valve port P4. It can switch between a state where the first valve port P1 is connected to the second valve port P2 and the third valve port P3 is connected to the fourth valve port P4, and a state where the first valve port P1 is connected to the fourth valve port P4 and the second valve port P2 is connected to the third valve port P3. During heating operation, the four-way switching valve 53 is in the state where the first valve port P1 is connected to the second valve port P2 and the third valve port P3 is connected to the fourth valve port P4.

[0050] The first expansion valve 54 and the second expansion valve 55 are examples of a low-level expansion mechanism. They are configured to have a variable opening degree and have the function of reducing the pressure of the refrigerant circulating in the low-level circuit 30 and expanding the refrigerant.

[0051] The receiver 56 is a tank for storing liquid refrigerant that has been condensed into liquid by the cascaded heat exchanger 67. The low-side circuit 30 may also be configured to have piping connecting the receiver 56 to the low-side compressor 51.

[0052] Check valves 57, 58, 59, and 60 are used to prevent refrigerant backflow and determine the direction of refrigerant flow. Details regarding refrigerant flow will be discussed later.

[0053] The shut-off valves 61, 62, 63, and 64 serve to connect the piping of the outdoor unit 10 and the piping of the indoor unit 20.

[0054] The cascaded heat exchanger 67 performs heat exchange between the low-level side loop 30 and the high-level side loop 40. The cascaded heat exchanger 67 has flow paths connected to the low-level side loop 30 and to the high-level side loop 40. For example, the cascaded heat exchanger 67 is a double-tube heat exchanger that combines two pipes of different diameters into inner and outer double layers. Furthermore, the cascaded heat exchanger 67 can also be other forms of heat exchangers such as plate heat exchangers.

[0055] During heating operation, the cascaded heat exchanger 67 functions as a condenser in the low-level loop 30 and as an evaporator in the high-level loop 40.

[0056] A heat exchanger 68 on the low-side circuit 30 facilitates heat exchange between the low-side circuit 30 and the heat medium circuit 50. The low-side heat exchanger 68 has a flow path connected to the low-side circuit 30 and a flow path connected to the heat medium circuit 50. During heating operation, the low-side heat exchanger 68 functions as a condenser. The heat medium flowing in the heat medium circuit 50 is heated by taking heat from the second refrigerant flowing in the low-side circuit 30, thus performing the heating function. The low-side heat exchanger 68 is a water-based heat exchanger, but it is not limited to this; for example, it can also be constructed as an air-based heat exchanger.

[0057] The low-level side circuit 30 has a bypass flow path 811. The bypass flow path 811 connects the flow path connecting the low-level side heat exchanger 68 and the cascaded heat exchanger 67 with the flow path connecting the low-level side heat exchanger 68 and the low-level side compressor 51.

[0058] The first stopcock valve 65 and the second stopcock valve 66 function to switch whether the second refrigerant flows through the low-side heat exchanger 68 by opening and closing. The first stopcock valve 65 is disposed in the flow path connecting the low-side heat exchanger 68 to the low-side compressor 51, and the second stopcock valve 66 is disposed in the bypass flow path 811. When the refrigerant flows through the low-side heat exchanger 68, the first stopcock valve 65 is open and the second stopcock valve 66 is closed. On the other hand, when the refrigerant does not flow through the low-side heat exchanger 68 but flows through the bypass flow path 811 to the cascaded heat exchanger 67, the first stopcock valve 65 is closed and the second stopcock valve 66 is open. The first stopcock valve 65 and the second stopcock valve 66 are controlled by the control unit 100 (see below) according to the switching conditions described later. Figure 7A Control its opening and closing.

[0059] The high-element side circuit 40 includes a cascaded heat exchanger 67, a high-element side compressor 69, a high-element side utilization heat exchanger 70, and a high-element side expansion mechanism 71.

[0060] Furthermore, the high-element side circuit 40 is not limited to the structure described above. For example, the high-element side circuit 40 may also be configured to include a filter, a radiator, an oil separator, etc. It may also be configured to include a pressure sensor, a high-pressure switch as a protection detector, etc.

[0061] The high-element compressor 69 draws in refrigerant from the suction side and discharges the compressed refrigerant from the discharge side. The high-element compressor 69 may also have a gas-liquid separator on its suction side to separate the refrigerant into gas and liquid. The discharge side of the high-element compressor 69 is connected to the high-element side via a heat exchanger 70, and the suction side of the high-element compressor 69 is connected to a cascaded heat exchanger 67.

[0062] Heat exchanger 70 on the high-current side facilitates heat exchange between the high-current side circuit 40 and the heat transfer medium circuit 50. During heating operation, the high-current side heat exchanger 70 functions as a condenser. The heat transfer medium flowing in the heat transfer medium circuit 50 is heated by taking heat from the refrigerant flowing in the high-current side circuit 40, thus performing the heating function. The high-current side heat exchanger 70 is a water-based heat exchanger, but it is not limited to this; for example, it can also be constructed as an air-based heat exchanger.

[0063] The high-level side expansion mechanism 71 has the function of reducing the pressure of the refrigerant circulating in the high-level side circuit 40 and expanding the refrigerant. The high-level side expansion mechanism 71 is, for example, a capillary tube. Because the flow path of the capillary tube is narrow, the flow of the refrigerant is resisted, and the pressure drops. Furthermore, the high-level side circuit 40 can also be configured to have an expansion valve instead of a capillary tube.

[0064] Figure 7A This is a block diagram illustrating the structure of the main equipment in this embodiment. The control unit 100 is, for example, a controller 100. The controller 100 is a device for controlling the operation of the hot water supply system. The controller 100 includes an MCU (Micro Control Unit), electrical circuits, and electronic circuits. The MCU includes a CPU (Central Processing Unit) 101, a memory 102, and a communication interface (communication I / F) 103. Various programs for execution by the CPU 101 are stored in the memory 102. The controller 100 can be composed of a single physically independent element or two or more physically separate elements.

[0065] The controller 100 controls the low-level side circuit 30 and the high-level side circuit 40. Specifically, the controller 100 controls the low-level side compressor 51, the high-level side compressor 69, the four-way switching valve 53, the first expansion valve 54, and the second expansion valve 55.

[0066] The heat transfer medium circuit 50 exchanges heat with the low-side circuit 30 and the high-side circuit 40 via the low-side heat exchanger 68 and the high-side heat exchanger 70, providing a heat exchange function. The heat transfer medium circuit 50 is filled with brine such as water, seawater, lake water, or antifreeze as the heat transfer medium. Alternatively, it can be filled with antifreeze such as tetrabutylammonium bromide hydrate (TBAB), silicone oil, or ethylene glycol as the heat transfer medium.

[0067] use Figure 2 An example of the structure of the heat medium circuit 50 will be described. Figure 2 This is a thermal medium circuit diagram illustrating a structural example of the thermal medium circuit 50 in this embodiment.

[0068] In addition to the heat exchanger 68 on the low-level side and the heat exchanger 70 on the high-level side, the heat medium circuit 50 may also include, for example, a three-way plug valve 81, a tank 82, a heat exchanger 83, a pump 84, and heat medium piping 85-89. The three-way plug valve 81 may also be replaced by a T-pipe, for example.

[0069] The hot medium flowing in the hot medium piping 85 of the hot medium circuit 50 is driven by the pump 84 and circulates within the hot medium piping 85. The hot medium flowing in the hot medium piping 85 passes through the low-side heat exchanger 68 and the high-side heat exchanger 70, where it is heated by exchanging heat with the refrigerant flowing in the low-side circuit 30 and the high-side circuit 40. Here, after passing through the low-side heat exchanger 68, the hot medium flows to the high-side heat exchanger 70. The hot water flowing out of the high-side heat exchanger 70 is delivered to the tank 82 or the hot medium piping 86 by the three-way stopcock valve 81, depending on its purpose.

[0070] When heating is required, the three-way stopcock valve 81 supplies hot water to the heat medium piping 86. The heat medium piping 86 is connected to each room where heating is required, and performs the heating function in each room. The water used for heating and then cooled returns from the heat medium piping 89. The water returning from the heat medium piping 89 enters the low-element heat exchanger 68 and the high-element heat exchanger 70, where it is heated by heat exchange and then supplied to the rooms again.

[0071] When hot water is being supplied, the three-way stopcock valve 81 delivers hot water to the tank 82. Water is stored in the tank 82, and heat exchange occurs between the water flowing through the heat medium piping 85 and the water stored in the tank 82 via a heat exchanger 83. The water stored in the tank 82 is heated by the heat exchanger 83 and supplied to the heat medium piping 87 for hot water supply, such as for showering. Conversely, the water flowing in the heat medium piping 85 is cooled by the heat exchanger 83, then enters the low-element side using the heat exchanger 68 and the high-element side using the heat exchanger 70, where it is heated by heat exchange and supplied to the tank 82 again. Furthermore, when using the water stored in the tank 82, tap water or similar water is replenished from the heat medium piping 88.

[0072] The refrigerant circuit system 1 of this embodiment can switch between the first cycle and the second cycle by using a switching circuit 80. The switching circuit 80 uses a first stopcock valve 65, a second stopcock valve 66, and a bypass flow path 811 to switch between the first cycle and the second cycle. When the first cycle is in use, the low-side circuit 30 prevents the refrigerant from flowing through the low-side heat exchanger 68 by closing the first stopcock valve 65 and opening the second stopcock valve 66, and instead directs the second refrigerant to the cascaded heat exchanger 67. When the second cycle is in use, the second refrigerant flows to the low-side heat exchanger 68 by closing the first stopcock valve 65 and opening the second stopcock valve 66, where heat exchange occurs.

[0073] The following explains the first loop, the second loop, and their switching conditions.

[0074] <First Cycle>

[0075] Next, use Figure 3 and Figure 4 This will explain the operation of the refrigerant circuit system 1 during heating operation in the first cycle of this embodiment. Figure 3 This is a refrigerant circuit diagram showing the flow of refrigerant during heating operation in the first cycle of this embodiment. Figure 4 (a) is the pressure-enthalpy curve during heating operation in the first cycle, and (b) is the pressure-enthalpy curve in the high-element side loop 40.

[0076] During the first cycle, the first stopcock valve 65 is closed and the second stopcock valve 66 is open. Furthermore, during heating operation, the four-way switching valve 53 of the low-voltage side circuit 30 is in a state where the first valve port P1 is connected to the second valve port P2 and the third valve port P3 is connected to the fourth valve port P4.

[0077] During the first cycle, the second refrigerant travels along... Figure 3 The arrow loop is shown. More specifically, in the low-pressure side loop 30, the refrigerant first flows from a low-pressure state (see reference...). Figure 3 and Figure 4 Point 91 of (b) is compressed by the low-side compressor 51. The compressed refrigerant enters the cascaded heat exchanger 67 through the four-way switching valve 53, the shut-off valve 63, the shut-off valve 64, and the second plug valve 66. During the first cycle, no refrigerant flows through the low-side heat exchanger 68, and no heat exchange occurs. Therefore, in Figure 3 The state of the refrigerant does not change between points 92 and 93 (refer to...). Figure 4 (b) Points 92 and 93).

[0078] Cascaded heat exchanger 67 functions as a condenser in the low-level loop 30, where the refrigerant is cooled through heat exchange with the high-level loop 40 (see reference). Figure 3 and Figure 4 (b) point 94).

[0079] Refrigerant flowing from cascaded heat exchanger 67 enters liquid receiver 56 via shut-off valve 62, shut-off valve 61, check valve 60, and second expansion valve 55. Refrigerant flowing from liquid receiver 56 enters low-side heat source heat exchanger 52 via first expansion valve 54 and check valve 57. The refrigerant is depressurized as it passes through second expansion valve 55 and first expansion valve 54 (see reference). Figure 3 and Figure 4 (b) point 95).

[0080] The low-side heat source heat exchanger 52 functions as an evaporator, where the refrigerant is heated through heat exchange with the external gas (see reference). Figure 3 and Figure 4(b) Point 91). The refrigerant flowing out of the low-side heat source heat exchanger 52 enters the low-side compressor 51 again through the four-way switching valve 53. In this way, the refrigerant circulates in the low-side circuit 30.

[0081] Furthermore, in the high-element side circuit 40, the first refrigerant flows along... Figure 3 The arrow indicates a cycle. The refrigerant first flows from a low-pressure state (see reference). Figure 3 and Figure 4 Point 96 of (a) is compressed by the high-level compressor 69 (refer to) Figure 3 and Figure 4 (a) Point 97). The compressed refrigerant enters the high-level side using heat exchanger 70. The high-level side heat exchanger 70 functions as a condenser, where the refrigerant flowing in the high-level side circuit 40 is cooled by the heat medium flowing in the heat medium circuit 50 (see reference). Figure 3 and Figure 4 (a) point 98).

[0082] Next, the refrigerant passes through the high-side expansion mechanism 71, where it is depressurized (see reference). Figure 3 and Figure 4 (a) Point 99). The depressurized refrigerant enters the cascaded heat exchanger 67. The cascaded heat exchanger 67 functions as an evaporator in the high-side loop 40, where the refrigerant is heated by heat exchange with the low-side loop 30 (see reference). Figure 3 and Figure 4 (a) Point 96). The refrigerant flowing out of the cascaded heat exchanger 67 re-enters the high-level compressor 69. In this way, the refrigerant circulates in the high-level circuit 40.

[0083] During the first cycle of use, the heat medium flowing in the heat medium circuit 50 is heated by exchanging heat with the refrigerant flowing in the high-side circuit 40 via the high-side heat exchanger 70. On the other hand, during the first cycle of use, heat exchange in the low-side heat exchanger 68 does not occur.

[0084] <Second Cycle>

[0085] Next, use Figure 5 and Figure 6 To illustrate the operation of the refrigerant circuit system 1 during heating operation in the second cycle of this embodiment. Figure 5 This is a refrigerant circuit diagram showing the flow of refrigerant during heating operation in the second cycle of this embodiment. Figure 6 The diagrams are pressure-enthalpy curves during heating operation in the second cycle. (a) is the pressure-enthalpy curve in the high-element side loop 40, and (b) is the pressure-enthalpy curve in the low-element side loop 30.

[0086] During the second cycle, the first stopcock valve 65 is in the open state, and the second stopcock valve 66 is in the closed state. Furthermore, during heating operation, the four-way switching valve 53 is in a state where the first valve port P1 is connected to the second valve port P2, and the third valve port P3 is connected to the fourth valve port P4.

[0087] During the second cycle, the refrigerant travels along... Figure 5 The arrow loop is shown. More specifically, in the low-pressure side loop 30, the refrigerant first flows from a low-pressure state (see reference...). Figure 5 and Figure 6 (b) Point 91) is compressed by the low-side compressor 51 (refer to) Figure 5 and Figure 6 (b) Point 92). The compressed refrigerant enters the low-level heat exchanger 68 via the four-way switching valve 53, shut-off valve 63, shut-off valve 64, and first plug valve 65. The low-level heat exchanger 68 functions as a condenser, where the refrigerant flowing in the low-level circuit 30 is cooled by the heat medium flowing in the heat medium circuit 50 (see reference). Figure 5 and Figure 6 (b) Point 93). The refrigerant flowing from the low-element side through heat exchanger 68 enters the cascade heat exchanger 67.

[0088] Cascaded heat exchanger 67 functions as a condenser in the low-level loop 30, where the refrigerant is cooled through heat exchange with the high-level loop 40 (see reference). Figure 5 and Figure 6 (b) point 94).

[0089] Refrigerant flowing from cascaded heat exchanger 67 enters liquid receiver 56 via shut-off valve 62, shut-off valve 61, check valve 60, and second expansion valve 55. Refrigerant flowing from liquid receiver 56 enters low-side heat source heat exchanger 52 via first expansion valve 54 and check valve 57. The refrigerant is depressurized as it passes through second expansion valve 55 and first expansion valve 54 (see reference). Figure 5 and Figure 6 (b) point 95).

[0090] The low-side heat source heat exchanger 52 functions as an evaporator, where the refrigerant is heated through heat exchange with the external gas (see reference). Figure 5 and Figure 6 (b) Point 91). The refrigerant flowing out of the low-side heat source heat exchanger 52 enters the low-side compressor 51 again through the four-way switching valve 53. In this way, the refrigerant circulates in the low-side circuit 30.

[0091] Furthermore, in the high-current side loop 40 during the second cycle, the flow of the refrigerant and the pressure-enthalpy diagram during heating operation are the same as those during the first cycle.

[0092] During the second cycle, the heat medium flowing in the heat medium circuit 50 exchanges heat with the refrigerant flowing in the low-side circuit 30 and the high-side circuit 40 via the low-side heat exchanger 68 and the high-side heat exchanger 70, respectively, thereby being heated.

[0093] <Switch Conditions>

[0094] For example, when a flammable refrigerant such as propane is used in the high-side circuit 40, its filling amount is limited. Therefore, in the first cycle, the heating capacity is limited only by heat exchange via the high-side heat exchanger 70. On the other hand, in the second cycle, both the low-side heat exchanger 68 and the high-side heat exchanger 70 are used for heat exchange, and the heat medium flowing in the heat medium circuit 50 is heated. When the second cycle is used, heat exchange also occurs in the low-side heat exchanger 68, thus providing a higher heating capacity compared to the first cycle.

[0095] Furthermore, in the second cycle, the refrigerant flowing in the low-side loop 30 is cooled in the low-side heat exchanger 68 and further cooled in the cascaded heat exchanger 67. Therefore, compared to the first cycle, a higher specific enthalpy can be achieved, thus improving the cooling effect.

[0096] On the other hand, in the second cycle, to ensure the outlet hot water temperature (the temperature of the first heat medium), it is necessary to increase the high pressure and the compressor speed. In contrast, in the first cycle, it is not necessary to set the pressure as in the second cycle, allowing for efficient operation.

[0097] Based on the above, it is preferable to implement the high-efficiency operation of the first cycle when the required heating capacity is small, and switch to the second cycle when the required heating capacity is large to ensure the heating capacity.

[0098] The following describes the switching between the first and second cycles in the refrigerant circuit system 1 of this embodiment.

[0099] <<Switching from the first cycle to the second cycle during heating operation>>

[0100] In the refrigerant circuit system 1 of this embodiment, for example, when the control unit 100 determines that the necessary heating capacity has not been reached, it switches from heating operation using the first cycle to heating operation using the second cycle. During the switch from the first cycle to the second cycle, the first stopcock valve 65 opens and the second stopcock valve 66 closes. The necessary heating capacity is determined by the control unit 100 based on three factors: the user-set hot water outlet temperature (target hot water outlet temperature), the current inlet water temperature, and the water flow rate.

[0101] When it is determined that the necessary heating capacity has not been reached, for example, when the speed of the compressor 69 on the high-side is above the upper limit or a certain threshold and the pump command value for controlling the water flow is below a certain threshold, but the outlet hot water temperature has not reached the target value. The outlet hot water temperature is the temperature of the water supplied from tank 82 to the heat medium piping 87.

[0102] use Figure 7B An example is given illustrating the process of switching from the first cycle to the second cycle during heating operation. Figure 7B This is a flowchart of the switching from the first cycle to the second cycle during heating operation. (a) shows an example of the case where the upper limit of the speed of the high-end compressor 69 is used, and (b) shows an example of the case where the threshold of the speed of the high-end compressor 69 is used.

[0103] right Figure 7B (a) To explain.

[0104] exist Figure 7B In (a), firstly, the operation utilizing the first cycle is performed (step 1001). The control unit 100 determines whether the speed of the compressor 69 on the high-end side is above the upper limit value (step 1002). If the speed is below the upper limit value (no in step 1002), the process returns to step 1001 and the operation utilizing the first cycle is performed.

[0105] If the rotational speed is above the upper limit (yes in step 1002), the control unit 100 determines whether the pump command value for controlling the water flow is below the threshold (step 1003). If the pump command value is above the threshold (no in step 1003), the system returns to step 1001 and performs operation using the first cycle.

[0106] If the pump command value is below the threshold (yes in step 1003), the control unit 100 determines whether the hot water temperature has reached the target value (step 1004). If the hot water temperature has not reached the target value (no in step 1004), the system returns to step 1001 and performs the first cycle.

[0107] When the hot water temperature reaches the target value (Yes in step 1004), the control unit 100 switches to operation using the second cycle (step 1005).

[0108] Next, regarding Figure 7B (b) Provide an explanation.

[0109] exist Figure 7BIn (b), firstly, the operation utilizing the first cycle is performed (step 1011). The control unit 100 determines whether the rotational speed of the high-end compressor 69 is above or above a threshold (step 1012). If the rotational speed is below the threshold (no in step 1012), the process returns to step 1011 and the operation utilizing the first cycle is performed.

[0110] If the rotational speed is above the threshold (yes in step 1012), the control unit 100 determines whether the pump command value for controlling the water flow rate is below the threshold (step 1013). If the pump command value is above the threshold (no in step 1013), the system returns to step 1011 and performs operation using the first cycle.

[0111] If the pump command value is below the threshold (yes in step 1013), the control unit 100 determines whether the hot water temperature has reached the target value (step 1014). If the hot water temperature has not reached the target value (no in step 1014), the system returns to step 1011 and performs the first cycle.

[0112] When the hot water temperature reaches the target value (Yes in step 1014), the control unit 100 switches to operation using the second cycle (step 1015).

[0113] The upper limit of the rotational speed of the compressor 69 on the high-end side means that it rotates at a speed higher than the upper limit of the continuous operation speed of the compressor set for each compressor. A case where the rotational speed of the compressor 69 on the high-end side is higher than a certain threshold is, for example, when the compressor 69 rotates at a speed of 75% or higher of its rotational capacity. A case where the pump command value for controlling the water flow is lower than a certain threshold is, for example, when the output value is lower than 50%. A case where the outlet hot water temperature does not reach the target value is, for example, when the target value is 55°C but the outlet temperature only reaches 50°C. In such cases, it is determined that the necessary heating capacity to achieve the target hot water temperature has not been reached in the first cycle, and a switch from the first cycle to the second cycle is initiated.

[0114] Furthermore, the speed of the high-side compressor 69 and the threshold value of the pump command mentioned above are just examples and are not limited to this. For example, the threshold values ​​could also be configured to be changed to serve as a reference for switching the refrigeration cycle.

[0115] By switching between the first and second cycles according to the switching conditions described above, the refrigeration cycle can be switched based on the speed of the compressor 69 on the high-end side, the pump command value, and the hot water outlet temperature.

[0116] Furthermore, a condition is determined to be insufficient heating capacity if, for example, the rotational speed of the compressor 69 on the high-end side is above the upper limit or a certain threshold, the heating capacity estimated based on the inlet water temperature, outlet hot water temperature, and pump command value has not reached the target capacity, and the heating capacity has not increased for a certain period of time. In the first cycle of use, even if the compressor 69 on the high-end side is operated at a speed above the upper limit or a certain threshold, if the heating capacity has not reached the target capacity and has not increased for a certain period of time, it is determined that the necessary heating capacity has not been reached in the first cycle.

[0117] For example, if the compressor 69 on the high-end side is rotating at 100% of its rotational capacity and the heating capacity estimated based on the inlet water temperature, outlet hot water temperature, and pump command value has not reached the target capacity for 5 minutes, the switch from the first cycle to the second cycle is performed.

[0118] Furthermore, the speed and duration of the aforementioned high-end compressor 69 are just one example and are not limited to this.

[0119] By switching between the first and second cycles according to the aforementioned switching conditions, the cooling cycle can be switched if it is determined that the necessary heating capacity has not been reached in the first cycle. Furthermore, switching is implemented if it is determined that the heating capacity has not increased within a certain period of time, thereby preventing the cooling cycle from switching before the heating capacity has been fully increased.

[0120] Furthermore, the control unit 100 can, for example, switch from heating operation using the first cycle to heating operation using the second cycle when the current rotational speed of the compressor 69 on the high-end side is at its upper limit, and the current heating capacity does not reach the necessary heating capacity, or the current hot water outlet temperature does not reach the target hot water outlet temperature. The current heating capacity is determined by the control unit 100 based on the current hot water outlet temperature, the current inlet water temperature, and the water flow rate.

[0121] Alternatively, the switching can be controlled based on the temperature of other components, for example, it can be configured to control the switching based on the temperature of the heat medium supplied from the heat medium piping 86. The temperature is measured, for example, by a thermometer not shown.

[0122] Furthermore, it can also be configured such that the pump command value used in the decision to switch from the first cycle to the second cycle is changed according to the setting of the heat medium piping length. The heat medium piping length refers to the length of the heat medium piping 86, 87 (refer to...) that will transport the heat medium flowing in the heat medium circuit 50 to each room supplied with heating or hot water. Figure 2 ( ) Piping length.

[0123] Even with consistent pump command values, it is impossible to achieve consistent water flow rates when the lengths of the hot medium piping differ. Even when using pump 84 (refer to...) with the same pump command values... Figure 2 In the case of ), the amount of water that can flow also varies depending on the length of the heat medium piping.

[0124] When estimating heating capacity based on pump command values, the heating capacity cannot be accurately estimated if the flow rate of water varies depending on the length of the heat medium piping. Therefore, to reduce errors in estimating heating capacity, for example, the control unit 100 receives the input of the heat medium piping length and adjusts the pump command value based on the heat medium piping length setting.

[0125] For example, if the pump command value is 40% when the length of the hot medium piping is 15m, then setting the pump command value to 70% when the length of the hot medium piping is 30m can correct for the difference in water volume caused by the different lengths of the hot medium piping.

[0126] According to this structure, water can flow at the same rate even when the length of the heat medium piping is different.

[0127] <<Switching from the second cycle to the first cycle during heating operation>>

[0128] In the refrigerant circuit system 1 of this embodiment, for example, when the current heating capacity has reached the necessary heating capacity, or the current hot water outlet temperature has reached the target hot water outlet temperature, and the current speed of the high-side compressor 69 has a margin relative to the upper limit of the speed of the high-side compressor 69, the control unit can switch from heating operation using the second cycle to heating operation using the first cycle. When switching from the second cycle to the first cycle, the first stop valve 65 is closed and the second stop valve 66 is opened.

[0129] When the speed of the high-end compressor 69 has a margin relative to the upper limit, for example, the current speed of the high-end compressor 69 rotates at a speed less than 90% of the upper limit speed of the high-end compressor.

[0130] use Figure 7C An example is given illustrating the process of switching from the second cycle to the first cycle during heating operation. Figure 7C This is a flowchart of the switching from the second cycle to the first cycle during heating operation. (a) shows an example of using the necessary heating capacity, and (b) shows an example of using the target hot water temperature.

[0131] right Figure 7C (a) To explain.

[0132] exist Figure 7CIn (a), firstly, the second cycle is used (step 2001). The control unit 100 determines whether the current heating capacity has reached the necessary heating capacity (step 2002). If the current heating capacity has not reached the necessary heating capacity (no in step 2002), the process returns to step 2001 and the second cycle is used.

[0133] If the current heating capacity has reached the necessary heating capacity (yes in step 2002), the control unit 100 determines whether the current speed of the high-end compressor 69 has a margin relative to the upper limit of the speed of the high-end compressor 69 (step 2003). If there is no margin relative to the upper limit (no in step 2003), the system returns to step 2001 and operates using the second cycle.

[0134] If there is a margin relative to the upper limit (yes in step 2003), the control unit 100 switches to operation using the first cycle (step 2004).

[0135] Next, regarding Figure 7C (b) Provide an explanation.

[0136] exist Figure 7C In (b), firstly, the second cycle is used (step 2011). The control unit 100 determines whether the current hot water temperature has reached the target hot water temperature (step 2012). If the current hot water temperature has not reached the target hot water temperature (no in step 2012), the process returns to step 2011 and the second cycle is used.

[0137] If the current hot water outlet temperature reaches the target hot water outlet temperature (yes in step 2012), the control unit 100 determines whether the current speed of the high-end compressor 69 has a margin relative to the upper limit of the speed of the high-end compressor 69 (step 2013). If there is no margin relative to the upper limit (no in step 2013), the system returns to step 2011 and performs operation using the second cycle.

[0138] If there is a margin relative to the upper limit (yes in step 2013), the control unit 100 switches to operation using the first cycle (step 2014).

[0139] <<When starting up refrigerant circuit system 1>>

[0140] Figure 7D This is a flowchart of the refrigerant circuit system startup process in this embodiment.

[0141] When the refrigerant circuit system 1 of this embodiment is started, the control unit determines whether to perform heating operation using the first cycle or heating operation using the second cycle based on the switching determination capability. The switching determination capability is an indicator used to determine which of the first and second cycles to use during heating operation, and is determined by the control unit 100 based on the target hot water temperature and the outside gas temperature.

[0142] For example, such as Figure 7D As shown, when the switching capability exceeds the necessary heating capacity (yes in step 3001), the control unit 100 starts the refrigerant circuit system 1 as the first cycle (step 3002). On the other hand, when the switching capability is lower than the necessary heating capacity (no in step 3001), the control unit 100 starts the refrigerant circuit system 1 as the second cycle (step 3003).

[0143] <<Control Steps for Refrigerant Circuit System 1>>

[0144] The control flow of the refrigerant circuit system 1 in this embodiment includes the following steps: a first step where the user sets the hot water temperature; a second step where the control unit 100 calculates the necessary heating capacity and switching judgment capability; and a third step where, based on the calculated switching judgment capability, it determines whether to perform heating operation using the first cycle or heating operation using the second cycle. In the third step, if heating operation using the first cycle is performed, and (1) the current speed of the high-end compressor 69 is at its upper limit, and (2) the current heating capacity does not reach the necessary heating capacity, or (3) the current hot water temperature does not reach the target hot water temperature, a fourth step is performed to switch to heating operation using the second cycle. In the third step, if heating operation using the second cycle is performed, and (1) the current speed of the high-end compressor 69 has a margin relative to the upper limit of the high-end compressor 69's speed, and (2) the current heating capacity reaches the necessary heating capacity, or (3) the current hot water temperature reaches the target hot water temperature, a fifth step is performed to switch to heating operation using the first cycle.

[0145] For example, when heating operation using the first cycle is currently in progress, the control unit 100 may periodically determine whether any of the following conditions (1) to (3) are met: (1) the current speed of the high-end compressor 69 is at its upper limit; (2) the current heating capacity has not reached the necessary heating capacity; (3) the current hot water outlet temperature has not reached the target hot water outlet temperature. Furthermore, for example, when heating operation using the second cycle is currently in progress, the control unit 100 may periodically determine whether any of the following conditions (1) to (3) are met: (1) the current speed of the high-end compressor 69 has a margin relative to the upper limit of the high-end compressor 69's speed; (2) the current heating capacity has reached the necessary heating capacity; (3) the current hot water outlet temperature has reached the target hot water outlet temperature.

[0146] Furthermore, it can be configured such that when an abnormality occurs in the high-side circuit 40, heating operation is performed only through the low-side circuit 30. An abnormality refers to a situation where operation using the high-side circuit 40 is impossible, such as a malfunction of the high-side compressor 69. Furthermore, it can be configured such that even in the event of a minor malfunction that is not to the point of inoperability, heating operation is performed only through the low-side circuit 30.

[0147] This structure allows for a certain level of heating capacity to be ensured even when the high-side circuit 40 cannot be used, solely through the low-side circuit 30.

[0148] Furthermore, it can be configured to report an anomaly when an anomaly occurs in the high-level circuit 40. The user receiving the anomaly report can then understand the unavailability of the high-level circuit 40 and respond quickly. According to this structure, the occurrence of an anomaly can be confirmed even when not on-site, and the user can determine whether to operate the heating system solely through the low-level circuit.

[0149] In this embodiment, the high-element side circuit 40 is installed indoors. When propane is used as the refrigerant filling the high-element side circuit 40 and installed indoors, according to IEC60335-2-40 Ed.7, the floor area of ​​the room where the equipment is installed is not limited when the refrigerant amount is 152g or less, but if it exceeds 152g, the floor area of ​​the room where the equipment is installed is limited, and safety measures in case of leakage are required.

[0150] In this invention, by suppressing the maximum heating capacity in the first cycle, the heat exchanger volume can be suppressed, thereby suppressing the refrigerant charge. In cases of insufficient heating capacity, the system switches to the second cycle, ensuring heating capacity even on the low-element side loop 30 side, thus expanding the maximum heating capacity. By suppressing the refrigerant charge in this way, the high-element side loop 40, filled with propane, can also be placed in a room where only a certain degree of ventilation is possible.

[0151] <Effect>

[0152] The refrigerant circuit system disclosed herein is a binary refrigerant circuit system formed by connecting a high-level refrigerant-using high-level side circuit 40 and a low-level refrigerant-using low-level side circuit 30 via a cascaded heat exchanger 67. The high-level side circuit 40 includes a high-level side compressor 69, a high-level side utilization heat exchanger 70, and a high-level side expansion mechanism 71. The low-level side circuit 30 includes a low-level side compressor 51, a low-level side utilization heat exchanger 68, a first expansion valve 54, a second expansion valve 55, and a low-level side heat source heat exchanger 52. The refrigerant circuit system has a switching loop 80 for a first cycle and a second cycle. In the first cycle, refrigerant flows from the low-level side compressor 51 to the cascaded heat exchanger 67. In the second cycle, refrigerant flowing from the low-level side compressor 51 to the low-level side utilization heat exchanger 68 flows to the cascaded heat exchanger 67. In this configuration, the refrigeration cycle can be switched according to the required heating capacity.

[0153] Here, in the refrigerant circuit system disclosed herein, the high-element heat exchanger 70 and the low-element heat exchanger 68 are water heat exchangers, and the refrigerant circuit system also includes a heat medium circuit 50, which includes heat medium piping 85, 86, 87, 89, a pump 84, and a tank 82.

[0154] Here, in the refrigerant circuit system disclosed herein, the low-element side circuit 30 further includes a bypass flow path 811, a first stopcock valve 65, and a second stopcock valve 66.

[0155] Here, in the refrigerant loop system 1 of this disclosure, when it is determined that the necessary heating capacity is not achieved when operating the first cycle for heating, the system switches to the second cycle. In this case, the switching of the refrigeration cycle can be performed by comparing the current heating capacity with the necessary heating capacity.

[0156] Here, in the refrigerant loop system disclosed herein, the necessary heating capacity is determined based on three factors: the user-set hot water outlet temperature (target hot water outlet temperature), the current inlet water temperature, and the water flow rate.

[0157] Here, in the refrigerant circuit system 1 of this disclosure, when the rotational speed of the high-side compressor 69 is above the upper limit or a certain threshold and the pump command value for controlling the flow rate of the heat medium is below a certain threshold, but the temperature of the first heat medium from the heat medium piping 87 has not reached the target value, the system switches to the second cycle. In this case, the switching of the refrigeration cycle can be based on the rotational speed of the high-side compressor 69, the pump command value, and the outlet hot water temperature.

[0158] Furthermore, in the refrigerant circuit system 1 of this disclosure, if it is determined that the rotational speed of the high-side compressor 69 is above the upper limit or a certain threshold, and the heating capacity estimated based on the inlet water temperature, outlet hot water temperature, and pump command value has not reached the target capacity, and the heating capacity has not increased for a certain period of time, the system switches to the second cycle. In this case, it is possible to prevent switching to the refrigeration cycle before the heating capacity is fully increased.

[0159] Furthermore, in the refrigerant circuit system 1 of this disclosure, the pump command value used in determining the switch from the first cycle to the second cycle is changed according to the length of the heat medium piping. In this case, the same flow rate of water can flow even when the length of the heat medium piping is different.

[0160] Furthermore, when an anomaly occurs in the high-side circuit 40, the refrigerant circuit system 1 of this disclosure operates for heating only through the low-side circuit 30. In this case, even if the high-side circuit 40 cannot be used, a certain level of heating capacity can be ensured using only the low-side circuit 30.

[0161] Furthermore, the refrigerant circuit system 1 of this disclosure reports an anomaly when an anomaly occurs in the high-side circuit 40. In this case, the occurrence of the anomaly can be confirmed even when not on-site, and a determination can be made on the user side whether heating operation is performed solely through the low-side circuit 30.

[0162] Furthermore, in the refrigerant circuit system 1 of this disclosure, the high-element side circuit 40 is installed indoors. In this case, even if a flammable refrigerant is used in the high-element side circuit, the filling amount limit of the flammable refrigerant can be met, and it can be installed even in an indoor space where only a certain degree of ventilation is possible.

[0163] Furthermore, in the refrigerant circuit system 1 disclosed herein, both refrigerants are natural refrigerants.

[0164] Furthermore, the refrigerant circuit system 1 of this disclosure uses propane in the high-element side circuit 40 and carbon dioxide in the low-element side circuit 30.

[0165] Furthermore, in the refrigerant circuit system 1 of this disclosure, the heat medium supplied from the pump 84 flows in the heat medium circuit 50 in the order of the low-element side using the heat exchanger 68 and the high-element side using the heat exchanger 70. In this case, no flow path switching is performed on the heat medium circuit 50 side, and the refrigeration cycle corresponding to the necessary heating capacity can be switched by switching the switching circuit 80.

[0166] Furthermore, the refrigerant circuit system disclosed herein also includes a four-way switching valve 53, which is used to switch between heating and cooling operation.

[0167] <Variation Example>

[0168] A variation of the refrigerant circuit system 1 of the present disclosure will be described. Furthermore, the following variations can be appropriately combined.

[0169] <Variation Example 1>

[0170] In the refrigerant circuit system 1 disclosed herein, in the bypass flow path 811 of the low-side circuit 30, the first plug valve 65 is configured in the flow path that connects the low-side circuit to the low-side compressor 51 via the heat exchanger 68, but is not limited to this arrangement.

[0171] Figure 8A This is a schematic refrigerant circuit diagram of the switching circuit in the refrigerant circuit system of Variation Example 1. For example... Figure 8A As shown, the first stopcock valve 65 is configured to connect the low-element side to the cascaded heat exchanger 67 via the heat exchanger 68 (see reference). Figure 1 () Connected to the flow path.

[0172] <Variation Example 2>

[0173] Figure 8B This is a schematic refrigerant circuit diagram of the switching circuit in the refrigerant circuit system of Variation Example 2.

[0174] In the refrigerant circuit system 1 of the present disclosure, in the bypass flow path 811 of the low-side circuit 30, a first stopcock valve 65 and a second stopcock valve 66 are used to switch whether the second refrigerant flows through the low-side heat exchanger 68. In contrast, as... Figure 8B As shown, in the refrigerant circuit system 1 of Modified Example 2, one end of the bypass flow path 811 is connected to the low-side heat exchanger 68 and the low-side compressor 51 (see reference). Figure 1 A three-way valve 812 is configured at the flow path connection point.

[0175] <Variation Example 3>

[0176] Figure 8C This is a schematic refrigerant circuit diagram of the switching circuit in the refrigerant circuit system of Variation Example 3.

[0177] like Figure 8C As shown, in the refrigerant circuit system 1 of Modified Example 3, one end of the bypass flow path 811 is connected to the low-element side via heat exchanger 68 and cascaded heat exchanger 67 (see reference). Figure 1 A three-way valve 813 is configured at the flow path connection point.

[0178] <Variation Example 4>

[0179] Figure 9AThis is a schematic diagram of the heat medium circuit in the refrigerant circuit system of Variation Example 4.

[0180] In the heat medium circuit 50 of the refrigerant circuit system 1 of the present disclosure, the heat medium flows from the lower-level side to the higher-level side via the heat exchanger 68, but is not limited to this manner. Figure 9A As shown, in the heat medium circuit 50 of Modified Example 4, the heat medium flows from the high-element side to the low-element side via the heat exchanger 68 after passing through the heat exchanger 70.

[0181] <Variation Example 5>

[0182] Figure 9B This is a schematic diagram of the heat medium circuit in the refrigerant circuit system of Modified Example 5.

[0183] like Figure 9B As shown, in the heat medium circuit 50 of Modified Example 5, the heat medium circulates independently in the heat exchanger 68 on the low-level side and in the heat exchanger 70 on the high-level side.

[0184] The embodiments have been described above, but the scope of this disclosure is not limited to the scope described in the above embodiments. As can be seen from the claims, combinations of two or more of the above embodiments, as well as modifications or improvements made to the above embodiments, are also included in the scope of this disclosure.

[0185] Label Explanation

[0186] 1. Refrigerant circuit system; 10. Outdoor unit; 20. Indoor unit; 30. Low-element side circuit; 40. High-element side circuit; 50. Heat medium circuit; 51. Low-element side compressor; 52. Low-element side heat source heat exchanger; 53. Four-way switching valve; 54. First expansion valve; 55. Second expansion valve; 67. Cascaded heat exchanger; 68. Low-element side utilization heat exchanger; 69. High-element side compressor; 70. High-element side utilization heat exchanger; 71. High-element side expansion mechanism; 80. Switching circuit.

Claims

1. A refrigerant circuit system comprising a high-element circuit (40) using a first refrigerant and a low-element circuit (30) using a second refrigerant connected via a cascaded heat exchanger (67), characterized in that, The high-element side circuit (40) includes a high-element side compressor (69), a high-element side heat exchanger (70), and a high-element side expansion mechanism (71). The low-element side circuit (30) includes a low-element side compressor (51), a low-element side heat exchanger (68), a low-element side expansion mechanism (54, 55), and a low-element side heat source heat exchanger (52). The refrigerant circuit system has a switching circuit (80) for a first cycle and a second cycle. In the first cycle, the refrigerant flows from the low-side compressor (51) to the cascaded heat exchanger (67). In the second cycle, the refrigerant that flows from the low-side compressor (51) to the low-side heat exchanger (68) flows to the cascaded heat exchanger (67).

2. The refrigerant circuit system according to claim 1, wherein, The high-element side heat exchanger (70) and the low-element side heat exchanger (68) are water heat exchangers. The refrigerant circuit system also includes a heat medium circuit (50), which includes heat medium piping (85, 86, 87, 89), a pump (84), and a tank (82).

3. The refrigerant circuit system according to claim 2, wherein, The low-element side circuit (30) also includes a bypass flow path (811), a first plug valve (65), and a second plug valve (66).

4. The refrigerant circuit system according to claim 1 or 2, wherein, When it is determined that the necessary heating capacity is not achieved when using the first cycle for heating operation, the system switches to the second cycle.

5. The refrigerant circuit system according to claim 4, wherein, The required heating capacity is determined based on three factors: the user-set target hot water temperature, the current inlet water temperature, and the water flow rate.

6. The refrigerant loop system according to claim 4, wherein, When the rotational speed of the compressor (69) on the high-side is above the upper limit or a certain threshold and the pump command value for controlling the flow rate of the heat medium is below a certain threshold, but the temperature of the first heat medium from the heat medium piping (87) has not reached the target value, the second cycle is switched.

7. The refrigerant circuit system according to claim 4, wherein, If the speed of the high-speed compressor (69) is determined to be above the upper limit or a certain threshold, and the heating capacity estimated based on the inlet water temperature, outlet hot water temperature and pump command value has not reached the target capacity, and the heating capacity has not increased for a certain period of time, the second cycle is switched.

8. The refrigerant circuit system according to claim 4, wherein, The pump command value used in the decision to switch from the first cycle to the second cycle is changed according to the length of the heat medium piping.

9. The refrigerant loop system according to claim 2, wherein, When an abnormality occurs in the high-element side circuit (40), heating operation is performed only through the low-element side circuit (30).

10. The refrigerant loop system according to any one of claims 2 to 9, wherein, An anomaly report is made when an anomaly occurs in the high-element side circuit (40).

11. The refrigerant loop system according to any one of claims 2 to 9, wherein, The high-element side circuit (40) is located indoors.

12. The refrigerant loop system according to any one of claims 2, 4, and 9, wherein, Both of the refrigerants mentioned use natural refrigerants.

13. The refrigerant loop system according to claim 12, wherein, Propane is used in the high-element side circuit (40), and carbon dioxide is used in the low-element side circuit (30).

14. The refrigerant loop system according to claim 2, wherein, In the heat medium circuit (50), the heat medium supplied from the pump (84) flows in the order of the low-element side heat exchanger (68) and the high-element side heat exchanger (70).

15. The refrigerant loop system according to claim 2, wherein, The refrigerant circuit system also has a four-way switching valve (53), which can be used to switch between heating and cooling operation.

Images