Refrigeration equipment

Abstract

This disclosure provides a refrigeration system that uses carbon dioxide as a natural refrigerant and can efficiently operate air conditioning equipment in a refrigerant circuit that includes air conditioning equipment and refrigeration equipment. [Solution] The refrigeration system in this disclosure comprises a refrigeration cycle circuit connecting an outdoor unit having a plurality of compressors, an outdoor heat exchanger, and a gas-liquid separator, an indoor unit having an indoor heat exchanger, and a refrigeration unit having a refrigerated heat exchanger, wherein the plurality of compressors are composed of low-stage compressors and high-stage compressors, the indoor heat exchanger with a high evaporation temperature is connected to the high-stage compressor, the refrigerated heat exchanger with a low evaporation temperature is connected to the low-stage compressor, and a branch pipe is provided to connect refrigerant piping connecting the indoor heat exchanger and the high-stage compressor, and refrigerant piping connecting the refrigerated heat exchanger and the low-stage compressor, with an on / off valve provided in the middle of the branch pipe.

Description

Technical Field

[0004] , ,

[0005] , , ,

[0001] The present disclosure relates to a refrigeration device.

Background Art

[0002] Patent Document 1 discloses a cascade heat exchanger that exchanges heat between the low-pressure side of a refrigerant circuit for air conditioning and the high-pressure side of a refrigerant circuit for cooling storage equipment. During the cooling operation of the refrigerant circuit for air conditioning, the refrigerant on the high-pressure side of the refrigerant circuit for cooling storage equipment is made to flow through the cascade heat exchanger via a condenser. During the heating operation of the refrigerant circuit for air conditioning, the refrigerant on the high-pressure side of the refrigerant circuit for cooling storage equipment is made to flow through the cascade heat exchanger and then through the condenser.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a refrigeration device that uses natural refrigerant carbon dioxide (R744) and can efficiently operate air conditioning equipment in a refrigerant circuit including air conditioning equipment and cold storage equipment.

Means for Solving the Problems

[0005] The refrigeration system in this disclosure comprises a refrigeration cycle circuit connecting an outdoor unit having a plurality of compressors, an outdoor heat exchanger, and a gas-liquid separator, an indoor unit having an indoor heat exchanger, and a refrigeration unit having a refrigerated heat exchanger. The plurality of compressors consist of low-stage compressors and high-stage compressors. The indoor heat exchanger, which has a high evaporation temperature, is connected to the high-stage compressor, and the refrigerated heat exchanger, which has a low evaporation temperature, is connected to the low-stage compressor. The system comprises a branch pipe connecting refrigerant piping that connects the indoor heat exchanger and the high-stage compressor, and refrigerant piping that connects the refrigerated heat exchanger and the low-stage compressor. An on / off valve is provided in the middle of the branch pipe. [Effects of the Invention]

[0006] According to the refrigeration system in this disclosure, by closing or opening the on / off valve, it is possible to operate in one-stage compression using only the high-stage compressor or two-stage compression using both the low-stage compressor and the high-stage compressor. Therefore, energy efficiency can be improved even when operating only the air conditioning system with a high evaporation temperature. [Brief explanation of the drawing]

[0007] [Figure 1] Circuit diagram showing the refrigeration system during cooling operation in Embodiment 1 [Figure 2] Circuit diagram of the refrigeration system showing the operation of the heating system in Embodiment 1. [Figure 3] Circuit diagram of a refrigeration system showing the operation of compressing the refrigerant from the indoor heat exchanger in two stages during cooling operation in Embodiment 1. [Modes for carrying out the invention]

[0008] (Knowledge and other information that formed the basis of this disclosure) At the time the inventors conceived of this disclosure, there was a refrigeration system in stores such as convenience stores that combined refrigeration and air conditioning equipment into a single refrigeration circuit, and used the waste heat from the refrigeration equipment for heating in winter to save energy. In recent years, such technologies have involved configuring a complex refrigeration cycle by controlling two or more different evaporation temperatures, as seen in air conditioning and refrigeration equipment. However, such technologies do not disclose how to operate air conditioning equipment or refrigeration equipment alone. In particular, the inventors discovered a problem in that when the refrigeration equipment is stopped and only the air conditioning equipment is operated independently, it is not possible to operate it efficiently according to the cooling load. The subject matter of this disclosure was created to solve this problem. This disclosure provides a refrigeration system that uses the natural refrigerant carbon dioxide (R744) and can efficiently operate air conditioning equipment in a refrigerant circuit that includes both air conditioning equipment and refrigeration equipment.

[0009] The embodiments will be described in detail below with reference to the drawings. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art. The attached drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0010] (Embodiment 1) Embodiment 1 will be described below with reference to the drawings. [1-1. Structure] Figure 1 is a circuit diagram showing the refrigeration circuit of the refrigeration device 1 in Embodiment 1. In Figure 1, for the sake of explanation, the valve body in the open state is shown in white, the valve body in the closed state is shown in black, and the throttling mechanism in the closed state is indicated by a dot. In Figure 1, for the sake of explanation, the piping through which the refrigerant flows is shown with thick lines, and the piping through which the refrigerant does not flow is shown with thin lines. The same applies to the following figures. The refrigeration circuit uses carbon dioxide (R744), a natural refrigerant that is non-flammable and non-toxic. As shown in Figure 1, the refrigeration system 1 comprises an outdoor unit 10, an indoor unit 20, and a refrigeration unit 30. The indoor unit 20 is used to provide air conditioning inside stores such as convenience stores and supermarkets, while the refrigeration equipment 30 is used to cool the interiors of refrigerated display cases and freezer display cases, which are installed in the stores as cooling storage equipment.

[0011] The refrigeration system 1 includes an outdoor unit 10 which is formed by sequentially connecting a two-stage compressor including a low-stage compressor 11 and high-stage compressors 12, 12, a first flow path switching mechanism 50, an outdoor heat exchanger 15, a second flow path switching mechanism 54, and a gas-liquid separator 16. The high-stage compressors 12, 12 are connected in parallel on the discharge side of the low-stage compressor 11. An accumulator 13 is positioned between the low-stage compressor 11 and the high-stage compressor 12. An intermediate-pressure pipe 80 is positioned between the discharge port of the low-stage compressor 11 and the suction port of the high-stage compressor 12. The intermediate-pressure pipe 80 connects the discharge port of the low-stage compressor 11 to the accumulator 13. The refrigerant discharged from the low-stage compressor 11 is mixed and homogenized by the accumulator 13 with the refrigerant flowing in from the indoor heat exchanger 22 and the refrigerant flowing in from the subcooled heat exchanger 90 (described later) via the intermediate-pressure pipe 80, and then evenly distributed to the two high-stage compressors 12, 12.

[0012] An oil separator 14 is connected to the discharge side of the high-stage compressor 12. A first flow path switching mechanism 50 is connected to the oil separator 14, and an outdoor heat exchanger 15 is connected to the first flow path switching mechanism 50. The first flow path switching mechanism 50 includes a pipe 40 connecting the oil separator 14 and the outdoor heat exchanger 15, and a first cooling valve 51 is connected to the pipe 40. The first heating pipe 41 is connected to the inlet side of the first cooling valve 51 of the piping 40. The first heating pipe 41 is equipped with a first heating valve 52. The first heating pipe 41 is connected to a pipe 71 that connects the outlet side of the indoor heat exchanger 22 of the indoor unit 20 to the medium-pressure pipe 80. A heating switching valve 23 is provided in the pipe 71.

[0013] On the outlet side of the first refrigeration valve 51 among the pipes 40, a first outdoor return pipe 42 is connected. The first outdoor return pipe 42 has an outdoor refrigerant return valve 53. The first outdoor return pipe 42 is connected to a pipe 72 that connects the refrigeration heat exchanger 31 of the refrigeration equipment 30 and the suction port of the low-stage compressor 11, and a refrigeration outlet-side expansion mechanism 33 of the refrigeration equipment 30 is connected to this pipe 72.

[0014] A second flow path switching mechanism 54 is connected to the outdoor heat exchanger 15. The second flow path switching mechanism 54 is formed by annularly connecting the ends of the first to fourth pipes 73, 74, 75, and 76 at connection parts A, B, C, and D. A second refrigeration expansion mechanism 55 is arranged in the first pipe 73. A second heating expansion mechanism 58 is arranged in the second pipe 74. A check valve 56 is arranged in the third pipe 75. A check valve 57 is arranged in the fourth pipe 76.

[0015] The connection part A between the second refrigeration expansion mechanism 55 and the second heating expansion mechanism 58 is connected to the outdoor heat exchanger 15, and the connection part B between the second heating expansion mechanism 58 and the check valve 56 is connected to a pipe 77 that connects the subcooling heat exchanger described later and the refrigeration heat exchanger 31. A refrigeration inlet-side expansion mechanism 32 is connected to this pipe 77. The connection part C between the check valve 56 and the check valve 57 is connected to the indoor heat exchanger 22 via a pipe 78. An indoor expansion mechanism 21 of the indoor unit 20 is connected to the pipe 78. The connection part D between the second refrigeration expansion mechanism 55 and the check valve 57 is connected to the gas-liquid separator 16 via a pipe 79. A throttling mechanism 17 is arranged in the pipe 79.​​​​​​​As a result, in the subcooling heat exchanger 90, the refrigerant sent from the gas-liquid separator 16 via a pipe and the gas refrigerant sent from the gas-liquid separator 16 via the gas refrigerant return pipe 81 are configured to perform heat exchange.

[0017] A gas refrigerant flow control valve 82 is provided in the middle of the gas refrigerant return pipe 81 and the subcooling heat exchanger 90. The gas refrigerant return pipe 81 from the subcooling heat exchanger 90 is connected to the medium-pressure pipe 80. In the present embodiment, a part of the gas refrigerant separated by the gas-liquid separator 16 and passing through the subcooling heat exchanger 90 is sent to the accumulator 13 and returned to the suction side of the high-stage compressor 12.

[0018] Also, the pipe on the outlet side of the subcooling heat exchanger 90 and the gas refrigerant return pipe 81 on the inlet side of the subcooling heat exchanger 90 are connected by a communication pipe 83, and a control valve 84 is provided in the middle of the communication pipe 83. In the subcooling heat exchanger 90, the refrigerant sent from the gas-liquid separator 16 via a pipe and the gas refrigerant sent from the gas-liquid separator 16 via the gas refrigerant return pipe 81 are configured to perform heat exchange. As a result, the refrigerant in the pipe 45 is cooled by the refrigerant in the gas refrigerant return pipe 81.

[0019] Also, in the present embodiment, a branch pipe 91 is provided to connect the outlet side of the indoor heat exchanger 22 and the outlet side of the cold equipment heat exchanger 31. An on-off valve 92 is provided in the middle of the branch pipe 91. The on-off valve 92 selects whether to open or close the on-off valve 92 based on the magnitude of the cooling load when the operation of the cold equipment 30 is stopped. When the on-off valve 92 is in the closed state, it can be operated by single-stage compression using only the high-stage compressor 12, and when the on-off valve 92 is in the open state, it can be operated by two-stage compression using the low-stage compressor 11 and the high-stage compressor 12.

[0020] The indoor heat exchanger 22 functions as an evaporator when the indoor unit 20 is in cooling operation, and its evaporation temperature is determined by the opening degree of the indoor expansion mechanism 21. In this embodiment, the evaporation temperature of the indoor heat exchanger 22 is determined according to the indoor temperature set for the indoor unit 20. The evaporation temperature range of the indoor heat exchanger 22 is, for example, 3°C to 6°C.

[0021] The refrigerated heat exchanger 31 functions as an evaporator, and its evaporation temperature is determined by the opening degree of the indoor expansion mechanism 21. In this embodiment, the evaporation temperature of the refrigerated heat exchanger 31 is determined according to the internal temperature set in the refrigeration equipment 30.

[0022] In this embodiment, the refrigeration equipment 30 allows for the selection and setting of one of the following temperature ranges for the interior of the unit: for example, a refrigeration temperature range (3°C to 6°C), a temperature range slightly higher than the refrigeration temperature range (3°C to 8°C), a partial freezing temperature range (-3°C to -1°C), and a freezing temperature range (-20°C to -18°C). Therefore, the evaporation temperature range of the refrigeration heat exchanger 31 is set lower than the temperature range inside the unit.

[0023] When the refrigeration equipment 30 is set to a refrigeration temperature range, the evaporation temperature range of the refrigerated heat exchanger 31 is, for example, -5°C to 0°C. When the refrigeration equipment 30 is set to a partial temperature range, the evaporation temperature range of the refrigerated heat exchanger 31 is, for example, -12°C to -8°C. When the refrigeration equipment 30 is set to a refrigeration temperature range, the evaporation temperature range of the refrigerated heat exchanger 31 is, for example, -40°C to -20°C.

[0024] Thus, the refrigeration system 1 is equipped with two heat exchangers with different evaporation temperature ranges. Of these two heat exchangers with different evaporation temperature ranges, the indoor heat exchanger 22 is connected to the suction side of the high-stage compressor 12, and the refrigerated heat exchanger 31, which has a lower evaporation temperature range than the indoor heat exchanger 22, is connected to the suction side of the low-stage compressor 11.

[0025] [1-2. Operation] Next, the operation of this embodiment will be described. First, let's explain how to operate the air conditioning. When operating in cooling mode, the first cooling valve 51 is opened, as shown in Figure 1. The first heating valve 52 and the outdoor refrigerant return valve 53 are closed. The on / off valve 92 is closed. In this state, by driving the low-stage compressor 11 and each high-stage compressor 12, the refrigerant compressed by the low-stage compressor 11 is sent to each high-stage compressor 12, where it is further compressed and discharged toward the oil separator 14.

[0026] The refrigerant, after passing through the oil separator 14, is sent to the outdoor heat exchanger 15 through the first cooling valve 51, where it exchanges heat with the outside air. The refrigerant after heat exchange is sent to the gas-liquid separator 16 via the second cooling expansion mechanism 55 and the throttling mechanism 17. The gaseous refrigerant from the gas-liquid separator 16 is sent to the subcooled heat exchanger 90, with the flow rate of the refrigerant controlled by the gaseous refrigerant flow control valve 82.

[0027] The refrigerant from the gas-liquid separator 16 is sent to the subcooled heat exchanger 90 via piping 45, where it exchanges heat with the refrigerant sent via the gas refrigerant return piping 81 and the gas refrigerant flow control valve 82. After being expanded by the indoor expansion mechanism 21 via piping 75 and check valve 56, it is sent to the indoor heat exchanger 22. In the indoor heat exchanger 22, the refrigerant exchanges heat with the indoor air, thereby cooling the indoor air. The refrigerant that has exchanged heat with the indoor air is returned to each high-stage compressor 12 via the accumulator 13.

[0028] Meanwhile, a portion of the refrigerant from the subcooled heat exchanger 90 is expanded by the cooling inlet expansion mechanism 32 via the piping 77 and then sent to the cooling heat exchanger 31. Heat exchange takes place in the cooling heat exchanger 31 to cool the cooling equipment 30. The refrigerant that has undergone heat exchange in the cooling heat exchanger 31 is returned to the low-stage compressor 11 via the cooling inlet expansion mechanism 32.

[0029] Furthermore, the refrigerant that has undergone heat exchange in the subcooled heat exchanger 90 is sent to the medium-pressure piping 80. By controlling the amount of gaseous refrigerant returned from the subcooled heat exchanger 90 with the gaseous refrigerant flow control valve 82, a differential pressure can be generated between the refrigerant sent from the subcooled heat exchanger 90 to the indoor heat exchanger 22 and the refrigerant sent from the indoor heat exchanger 22 to the low-stage compressor 11.

[0030] Next, we will explain how the system operates when using the heating function. Figure 2 is a circuit diagram of the refrigeration unit 1 showing the operation of the heating system. The flow of refrigerant is indicated by arrows in the figure. As shown in Figure 2, when performing heating operation, the first heating valve 52 is opened, and the first cooling valve 51 and the second cooling expansion mechanism 55 are closed. The on / off valve 92 is closed.

[0031] In this state, by driving the low-stage compressor 11 and each high-stage compressor 12, the refrigerant compressed by the low-stage compressor 11 is sent to each high-stage compressor 12, where it is further compressed and discharged toward the oil separator 14. The refrigerant, after passing through the oil separator 14, is sent to the indoor heat exchanger 22 through the first heating valve 52, where it exchanges heat with the indoor air to heat the indoor air.

[0032] The refrigerant that has undergone heat exchange in the indoor heat exchanger 22 is sent to the gas-liquid separator 16 via pipes 78 and 76. The refrigerant from the gas-liquid separator 16 is sent to the subcooled heat exchanger 90 via pipe 45, where it exchanges heat with the refrigerant sent via the gas refrigerant return pipe 81 and the gas refrigerant flow control valve 82. After being expanded by the cooling inlet expansion mechanism 32 via pipe 77, it is sent to the refrigerated heat exchanger 31. Heat exchange takes place in the refrigerated heat exchanger 31 to cool the refrigerated equipment 30. The refrigerant that has undergone heat exchange in the refrigerated heat exchanger 31 is returned to the low-stage compressor 11 via the cooling inlet expansion mechanism 32. In other words, in the refrigeration system 1 of this disclosure, the indoor heat exchanger 22 is configured to function as a gas cooler during heating, and the outdoor heat exchanger 15 is not used.

[0033] Next, we will explain the operation of compressing the refrigerant supplied from the indoor heat exchanger 22 in two stages during cooling operation. Figure 3 is a circuit diagram of the refrigeration system 1 showing the operation of compressing the refrigerant from the indoor heat exchanger 22 in two stages during cooling operation. The flow of refrigerant is indicated by arrows in the figure. When operating in cooling mode, the first cooling valve 51 is opened, as shown in Figure 3. The first heating valve 52, the heating switching valve 23, and the outdoor refrigerant return valve 53 are closed. The on / off valve 92 is opened. The cooling inlet expansion mechanism 32 and the cooling outlet expansion mechanism 33 are closed to prevent refrigerant from flowing to the cooling heat exchanger 31, thereby stopping the operation of the cooling equipment 30.

[0034] In this state, by driving the low-stage compressor 11 and each high-stage compressor 12, the refrigerant compressed by the low-stage compressor 11 is sent to each high-stage compressor 12, where it is further compressed and discharged toward the oil separator 14.

[0035] The refrigerant, after passing through the oil separator 14, is sent to the outdoor heat exchanger 15 through the first cooling valve 51, where it exchanges heat with the outside air. The refrigerant after heat exchange is sent to the gas-liquid separator 16 via the second cooling expansion mechanism 55 and the throttling mechanism 17. The gaseous refrigerant from the gas-liquid separator 16 is sent to the subcooled heat exchanger 90 via the gaseous refrigerant return pipe 81 and the gaseous refrigerant flow control valve 82. The refrigerant from the gas-liquid separator 16 is sent to the subcooled heat exchanger 90 via piping 45, where it exchanges heat with the refrigerant sent via the gas refrigerant return piping 81 and the gas refrigerant flow control valve 82. After being expanded by the indoor expansion mechanism 21 via piping 75 and check valve 56, it is sent to the indoor heat exchanger 22. In the indoor heat exchanger 22, the refrigerant exchanges heat with the indoor air, thereby cooling the indoor air. The refrigerant that has exchanged heat with the indoor air is sent to the low-stage compressor 11 via the branch pipe 91 and the on-off valve 92.

[0036] In other words, by opening the on / off valve 92, the refrigerant sent from the indoor heat exchanger 22 can be sent to the low-stage compressor 11, enabling two-stage compression by the low-stage compressor 11 and the high-stage compressor 12. Here, whether to open the on-off valve 92 and operate with two-stage compression, or to close the on-off valve 92 and operate with one-stage compression using only the high-stage compressor 12, is determined by the magnitude of the cooling load. For example, if the difference between the set temperature and the room temperature is greater than the specified value, or if the ambient temperature is higher than the specified value, the cooling load is judged to be high. When operating with two-stage compression, the COP increases by approximately 40% compared to when operating with single-stage compression. On the other hand, the cooling capacity decreases by approximately 40%. Therefore, when the cooling load is large during cooling operation, the on / off valve 92 should be opened or closed depending on whether the priority is given to COP or cooling capacity.

[0037] [1-3. Effects, etc.] As described above, the refrigeration system 1 in Embodiment 1 includes a refrigeration cycle circuit connecting an outdoor unit 10 having a low-stage compressor 11 and a high-stage compressor 12 (compressor), an outdoor heat exchanger 15, and a gas-liquid separator 16, an indoor unit 20 having an indoor heat exchanger 22, and a refrigeration equipment 30 having a refrigerated heat exchanger 31. The indoor heat exchanger 22, which has a high evaporation temperature, is connected to the high-stage compressor 12, and the refrigerated heat exchanger 31, which has a low evaporation temperature, is connected to the low-stage compressor 11. The system includes a refrigerant pipe 71 connecting the indoor heat exchanger 22 and the high-stage compressor 12, and a branch pipe 91 connecting the refrigerant pipe 72 connecting the refrigerated heat exchanger 31 and the low-stage compressor 11. An on / off valve 92 is provided in the middle of the branch pipe 91. This allows the system to operate in either single-stage compression using only the high-stage compressor 12 or two-stage compression using both the low-stage compressor 11 and the high-stage compressor 12, by closing the on-off valve 92. Therefore, energy efficiency can be improved even when operating only the air conditioning system with a high evaporation temperature.

[0038] Furthermore, in Embodiment 1, when the operation of the refrigeration equipment 30 is stopped, the refrigeration device 1 selects whether to open or close the on-off valve 92 based on the magnitude of the cooling load. As a result, when the cooling equipment 30 is stopped, the system can choose whether to open or close the on-off valve 92 based on the magnitude of the cooling load, thereby allowing it to select between operation that prioritizes COP (Coefficient of Performance) or operation that prioritizes cooling capacity. Therefore, even when only the air conditioning equipment is running, efficient operation can be achieved, improving energy efficiency.

[0039] Furthermore, the refrigeration system 1 in Embodiment 1 is provided with a gas refrigerant return pipe 81 that sends the gas refrigerant from the gas-liquid separator 16 to the high-stage compressor 12. The gas refrigerant return pipe 81 is provided with a gas refrigerant flow control valve 82 that controls the amount of gas refrigerant returned from the gas-liquid separator 16. By adjusting the opening of the gas refrigerant flow control valve 82, a differential pressure is generated between the refrigerant sent to the indoor heat exchanger 22 and the refrigerant sent from the indoor heat exchanger 22 to the low-stage compressor 11. This allows for the creation of a differential pressure between the refrigerant sent from the gas-liquid separator 16 to the indoor heat exchanger 22 and the refrigerant sent from the indoor heat exchanger 22 to the low-stage compressor 11 by adjusting the opening of the gas-refrigerant flow control valve 82. As a result, efficient operation can be achieved even when only the air conditioning equipment is running, improving energy efficiency.

[0040] Furthermore, the refrigeration device 1 in Embodiment 1 uses carbon dioxide as the refrigerant. This makes it possible to improve the cooling capacity of refrigeration system 1, which uses carbon dioxide as a refrigerant, as it has a low environmental impact. Therefore, it is possible to improve the efficiency of refrigeration system 1 while suppressing environmental impact.

[0041] (Other embodiments) As described above, Embodiment 1 has been explained as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this and can be applied to embodiments that have been modified, replaced, added, or omitted. Furthermore, it is possible to create new embodiments by combining the components described in Embodiment 1 above. Therefore, other embodiments are illustrated below.

[0042] In the above embodiment, the refrigeration system 1 was equipped with a low-stage compressor 11 and a high-stage compressor 12 as compressors, and was configured to enable two-stage compression, but this is just one example. For example, instead of the low-stage compressor 11 and the high-stage compressor 12, a compound compressor capable of two-stage compression may be provided as the compressor of the refrigeration circuit 2. Also, two or more of the low-stage compressor 11, the high-stage compressor 12, or compressors that replace them may be connected in parallel.

[0043] In the above embodiment, it was described that the system includes a first flow path switching mechanism 50 connected in a ring and a second flow path switching mechanism 54 connected in a ring, but this is just one example. The first flow path switching mechanism 50 is sufficient if it can switch between the indoor heat exchanger 22 and the outdoor heat exchanger 15 to function as a gas cooler, and regardless of which one is functioning as the gas cooler, the refrigerant that has passed through the gas cooler can be directed toward the gas-liquid separator 16. In other words, any part or all of the flow path switching mechanism may be replaced with an on-off valve, a check valve, a throttle valve, or a four-way valve, etc., as long as it has the same function as the first flow path switching mechanism 50 and the second flow path switching mechanism 54 in this embodiment.

[0044] In the above embodiment, carbon dioxide was described as being used as the refrigerant in the refrigeration system 1, but this is just one example. The type of refrigerant in the refrigeration system 1 is not particularly limited and may be a natural refrigerant other than carbon dioxide, or a refrigerant other than a natural refrigerant such as an HFC-based refrigerant or an HFO-based refrigerant. However, using carbon dioxide as the refrigerant in the refrigeration system 1 can reduce the risk of refrigerant leakage, such as environmental impact.

[0045] (Note) Based on the above description of embodiments, the following technologies are disclosed. (Technical 1) A refrigeration system comprising a refrigeration cycle circuit connecting an outdoor unit having multiple compressors, an outdoor heat exchanger, and a gas-liquid separator, an indoor unit having an indoor heat exchanger, and a refrigeration unit having a refrigerated heat exchanger, wherein the multiple compressors consist of low-stage compressors and high-stage compressors, the indoor heat exchanger with a high evaporation temperature is connected to the high-stage compressor, the refrigerated heat exchanger with a low evaporation temperature is connected to the low-stage compressor, and a branch pipe connecting refrigerant piping connecting the indoor heat exchanger and the high-stage compressor, and refrigerant piping connecting the refrigerated heat exchanger and the low-stage compressor, with an on / off valve provided in the middle of the branch pipe. With this configuration, by closing the on / off valve, the system can operate in one-stage compression using only the high-stage compressor, or in two-stage compression using both the low-stage and high-stage compressors. Therefore, energy efficiency can be improved even when operating only the air conditioning system with a high evaporation temperature.

[0046] (Technology 2) The refrigeration apparatus according to Technology 1, wherein when the operation of the refrigeration equipment is stopped, the on / off valve is selected to be opened or closed based on the magnitude of the cooling load. With this configuration, when the refrigeration equipment is stopped, the system can choose whether to open or close the on / off valve based on the magnitude of the cooling load, thereby allowing it to prioritize either COP (Coefficient of Performance) or cooling capacity. As a result, even when only the air conditioning equipment is running, efficient operation can be achieved, improving energy efficiency.

[0047] (Technology 3) A refrigeration apparatus according to Technology 1 or Technology 2, wherein a gas refrigerant return pipe is provided to send the gas refrigerant from the gas-liquid separator to the high-stage compressor, the gas refrigerant return pipe is provided with a gas refrigerant flow control valve for controlling the amount of gas refrigerant returned from the gas-liquid separator, and the opening degree of the gas refrigerant flow control valve is adjusted to generate a differential pressure between the refrigerant sent to the indoor heat exchanger and the refrigerant sent from the indoor heat exchanger to the low-stage compressor. With this configuration, by adjusting the opening of the gas refrigerant flow control valve, a differential pressure can be generated between the refrigerant sent from the gas-liquid separator to the indoor heat exchanger and the refrigerant sent from the indoor heat exchanger to the low-stage compressor. Therefore, even when operating only the air conditioning equipment, efficient operation can be achieved, improving energy efficiency.

[0048] (Technical 4) A refrigeration apparatus according to any one of Technical 1 to 3, wherein the refrigerant is a refrigerant that uses carbon dioxide. This configuration allows for improved cooling capacity in refrigeration systems that use carbon dioxide, which has a low environmental impact, as a refrigerant. Therefore, it is possible to increase the efficiency of refrigeration systems while suppressing environmental impact. [Industrial applicability]

[0049] This disclosure is suitably applicable to refrigeration systems that use carbon dioxide as a natural refrigerant and can efficiently operate air conditioning equipment in a refrigerant circuit that includes both air conditioning equipment and refrigeration equipment. [Explanation of symbols]

[0050] 1. Refrigeration equipment 10 Outdoor unit 11. Low-stage compressor 12 High-stage compressor 13 Accumulator 14 Oil Separator 15 Outdoor heat exchanger 16 Gas-liquid separator 17 Aperture mechanism 20 Indoor unit 21 Indoor Inflation Mechanism 22 Indoor heat exchanger 23 Heating switching valve 30 Refrigeration equipment 31 Refrigerated heat exchanger 32. Inlet-side expansion mechanism for refrigeration 33. Expansion mechanism for the outlet side of the cooling system 40 Piping 41 Heating piping 42. First return pipe for outdoor use 45 Piping 50 First flow path switching mechanism 51 Air conditioning valve 52 Heating valve 53 Outdoor refrigerant return valve 54 Second flow path switching mechanism 55 Expansion mechanism for cooling 56 Check valve 57 Check valve 58 Heating Expansion Mechanism 71 Piping 72 Piping 73 Piping 74 Piping 75 Piping 76 Piping 77 Piping 78 Piping 79 Piping 80 Medium-pressure piping 81 Gas refrigerant piping 82 Gas refrigerant flow control valve 83 Communication pipe 84 Control valve 90 Subcooling heat exchanger 91 Branch piping 92 Shut-off valves A Connection part B Connection part C connection D connection part

Claims

1. The system includes a refrigeration cycle circuit connecting an outdoor unit having multiple compressors, an outdoor heat exchanger, and a gas-liquid separator, an indoor unit having an indoor heat exchanger, and a refrigeration unit having a cooling heat exchanger. The multiple compressors consist of a low-stage compressor and a high-stage compressor. The indoor heat exchanger with a high evaporation temperature is connected to the high-stage compressor, and the refrigerated heat exchanger with a low evaporation temperature is connected to the low-stage compressor. The system includes a branch pipe connecting a refrigerant pipe that connects the indoor heat exchanger and the high-stage compressor, and a refrigerant pipe that connects the refrigerated heat exchanger and the low-stage compressor. A shut-off valve is provided in the middle of the aforementioned branch pipe. Refrigeration equipment.

2. If the operation of the aforementioned refrigeration equipment is stopped, the on / off valve is selected to be opened or closed based on the magnitude of the cooling load. The refrigeration apparatus according to claim 1.

3. A gas refrigerant return pipe is provided to send the gas refrigerant from the gas-liquid separator to the high-stage compressor. The gas refrigerant return piping is provided with a gas refrigerant flow control valve that controls the amount of gas refrigerant returned from the gas-liquid separator. The opening degree of the gas refrigerant flow control valve is adjusted to generate a differential pressure between the refrigerant sent to the indoor heat exchanger and the refrigerant sent from the indoor heat exchanger to the low-stage compressor. The refrigeration apparatus according to claim 2.

4. The refrigerant is a refrigerant that uses carbon dioxide. The refrigeration apparatus according to claim 1.

Images