Air conditioning device

Abstract

An air conditioning apparatus includes a refrigerant circuit that performs a refrigeration cycle for performing a heating operation in which a utilization-side space is heated by compressing a refrigerant to above a critical pressure, and a control device. A radiator includes a first radiator and a second radiator connected in parallel. An expansion valve includes a first expansion valve and a second expansion valve. The first radiator and the first expansion valve constitute a first utilization unit. The second radiator and the second expansion valve constitute a second utilization unit. The control device controls the first expansion valve to switch between a first state in which the first expansion valve is completely closed or opened at a slight opening degree, and a second state in which the first expansion valve is opened more than in the first state, when the first utilization unit is in a stop mode.

Description

Technical Field

[0001] This disclosure relates to an air conditioning device. Background Technology

[0002] For example, as shown in Patent Document 1, various technologies concerning air conditioning devices are disclosed. The air conditioning device disclosed in Patent Document 1 includes a refrigerant circuit. The refrigerant circuit has a compressor, a radiator, an expansion valve, and an evaporator, and performs a refrigeration cycle for heating operation to warm the room. In the air conditioning device disclosed in Patent Document 1, supercritical operation is performed, compressing the refrigerant to a pressure above the critical pressure.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Publication No. 2021-055874 Summary of the Invention

[0006] -The technical problem the invention aims to solve-

[0007] In a multi-split air conditioning system where a heat source unit is connected to multiple user units, it is sometimes necessary to stop some of the user units. In this case, throttling is usually performed by slightly opening the expansion valve of the user unit to be stopped.

[0008] In multi-split air conditioning systems operating in supercritical conditions, when the above method is used to stop some of the multiple operating units, a problem arises where the refrigerant pressure rises on the downstream side of the radiator of the operating unit. Simultaneously, it is also necessary to prevent the accumulation of liquid refrigerant in the radiator of the operating unit that was stopped.

[0009] Due to the above circumstances, it is difficult to stop some of the multiple operating units in a multi-split air conditioning system that is operating under supercritical conditions.

[0010] The purpose of this disclosure is to enable the shutdown of a portion of the multiple operating units in a multi-split air conditioning system that operates in a supercritical manner.

[0011] - Technical solutions used to solve technical problems -

[0012] The first aspect of this disclosure pertains to an air conditioning unit 1. The air conditioning unit 1 includes a refrigerant circuit 6 and a control device 130. The refrigerant circuit 6 has a compressor 20, a radiator 64, an expansion valve 63, and an evaporator 24. A refrigeration cycle for performing heating operation is conducted by compressing the refrigerant to a critical pressure Pc or higher, during which heating is provided to the side space R. The control device 130 controls the refrigerant circuit 6. The radiator 64 includes a first radiator 64A and a second radiator 64B connected in parallel. The expansion valve 63 includes a first expansion valve 63A corresponding to the first radiator 64A and a second expansion valve 64B corresponding to the second radiator 64A. The second expansion valve 63B corresponding to B, the first radiator 64A and the first expansion valve 63A constitute the first utilization unit 60A, the second radiator 64B and the second expansion valve 63B constitute the second utilization unit 60B. When the first utilization unit 60A is in the stop mode M1, the control device 130 controls the first expansion valve 63A to switch between the first state J1 and the second state J2. In the first state J1, the first expansion valve 63A is completely closed or opened with a small opening. In the second state J2, the first expansion valve 63A is opened more than in the first state J1.

[0013] According to the first aspect, in a multi-split air conditioning unit 1 that operates in supercritical mode, the first utilization unit 60A in the first utilization unit 60A and the second utilization unit 60B can be stopped.

[0014] The second aspect of this disclosure pertains to the air conditioning device 1 of the first aspect. The refrigerant circuit 6 includes a gas-liquid separator 25 connected downstream of the radiator 64, which separates the refrigerant into gaseous and liquid refrigerant. The control device 130 switches the first expansion valve 63A from the second state J2 to the first state J1 based on an increase in the pressure Pd of the gas-liquid separator 25.

[0015] According to the second aspect, when the pressure Pd of the gas-liquid separator 25 located downstream of the radiator 64 rises, the pressure Pd of the gas-liquid separator 25 can be suppressed by switching the first expansion valve 63A of the first utilization unit 60A from the second state J2 to the first state J1 and throttling the first expansion valve 63A of the first utilization unit 60A.

[0016] The third aspect of this disclosure pertains to the air conditioning device 1 of the second aspect. When the difference between the refrigerant temperature TIA at the inlet IA of the first radiator 64A and the refrigerant temperature TEA at the outlet EA of the first radiator 64A is greater than a first value Q1, or when the refrigerant temperature TEA at the outlet EA of the first radiator 64A rises over time, the control device 130 switches the first expansion valve 63A from the second state J2 to the first state J1.

[0017] According to the third aspect, even without directly measuring the pressure Pd of the gas-liquid separator 25, the first expansion valve 63A of the first utilization unit 60A can be switched from the second state J2 to the first state J1 when the pressure Pd of the gas-liquid separator 25 rises.

[0018] The fourth aspect of this disclosure pertains to the air conditioning device 1 of the second aspect. When the duration of the second state J2 is greater than the second value Q2, the control device 130 switches the first expansion valve 63A from the second state J2 to the first state J1.

[0019] According to the fourth aspect, even without directly measuring the pressure Pd of the gas-liquid separator 25, the first expansion valve 63A of the first utilization unit 60A can be switched from the second state J2 to the first state J1 when the pressure Pd of the gas-liquid separator 25 rises.

[0020] The fifth aspect of this disclosure pertains to the air conditioning device 1 described in any one of the first to fourth aspects. When the temperature TIA of the refrigerant at the inlet IA of the first radiator 64A is less than the temperature Tc at the critical point C of the refrigerant; or, when the difference between the temperature TIA of the refrigerant at the inlet IA of the first radiator 64A and the temperature TEA of the refrigerant at the outlet EA of the first radiator 64A is less than a third value Q3; or, when the difference between the temperature TIA of the refrigerant at the inlet IA of the first radiator 64A and the temperature TRA of the utilization side space RA involved in the first utilization unit 60A is less than a fourth value Q4; or, when the duration of the first state J1 is greater than a fifth value Q5, the control device 130 switches the first expansion valve 63A from the first state J1 to the second state J2.

[0021] According to the fifth aspect, by switching the first expansion valve 63A of the first utilization unit 60A from the first state J1 to the second state J2, the first expansion valve 63A of the first utilization unit 60A is opened, thereby preventing the accumulation of liquid refrigerant in the first radiator 64A of the first utilization unit 60A.

[0022] The sixth aspect of this disclosure pertains to the air conditioning unit 1 described in any one of the first to fifth aspects. When the first utilizing unit 60A is in stop mode M1 and the second utilizing unit 60B is in operating mode M2, the control device 130 causes the opening degree of the first expansion valve 63A to be less than the opening degree of the second expansion valve 63B.

[0023] According to the sixth aspect, while the second utilization unit 60B is in operation, the first utilization unit 60A can be stopped.

[0024] The seventh aspect of this disclosure pertains to the air conditioning unit 1 described in any one of the first to sixth aspects. The control device 130 initiates heating operation while the fan 62A in the first utilizing unit 60A is stopped. After the heating operation is initiated, when the temperature TEA of the refrigerant at the outlet EA of the first radiator 64A is greater than the temperature Tc at the critical point C of the refrigerant, the control device 130 drives the fan 62A.

[0025] According to the seventh aspect, it is possible to prevent the pressure generated by the compressor 20 from becoming too high immediately after the heating operation is started.

[0026] The eighth aspect of this disclosure pertains to the air conditioning device 1 of the seventh aspect. The refrigerant circuit 6 includes a gas-liquid separator 25, an exhaust passage 41, and a switching valve 42. The gas-liquid separator 25 is connected to the downstream side of the radiator 64, and separates the refrigerant into gaseous and liquid refrigerant. The exhaust passage 41 connects the gas storage section 25a of the gas-liquid separator 25 to the suction side 20i of the compressor 20. The switching valve 42 is disposed on the exhaust passage 41, and the control device 130 opens the switching valve 42 when heating operation is started.

[0027] According to the eighth aspect, by promoting the flow of gaseous refrigerant from the gas storage section 25a of the gas-liquid separator 25 into the suction side 20i of the compressor 20 during the start-up of heating operation, it is possible to increase the rate of pressure rise generated by the compressor 20. Attached Figure Description

[0028] Figure 1 This is a piping system diagram of the air conditioning unit 1 according to the first embodiment.

[0029] Figure 2 This is a diagram of the piping system near the air conditioning unit 60 according to the first embodiment.

[0030] Figure 3 This is a block diagram illustrating the connection relationship between the controller 130 and the peripheral device according to the first embodiment.

[0031] Figure 4 It is a graph showing the relationship between the specific enthalpy h of the refrigerant involved in the first embodiment and the pressure P.

[0032] Figure 5 This is a piping system diagram showing the first air conditioning unit 60A in the first embodiment being in stop mode M1 and the second air conditioning unit 60B being in operation mode M2.

[0033] Figure 6 This is a control flow diagram of the first air conditioning unit 60A involved in the first embodiment.

[0034] Figure 7 This is a piping system diagram showing the situation in the second embodiment where the first air conditioning unit 60A is in stop mode M1 and the second air conditioning unit 60B is in operation mode M2. Detailed Implementation

[0035] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that this disclosure is not limited to the embodiments shown below, and various modifications can be made without departing from the technical concept of this disclosure. The accompanying drawings are for conceptual illustration of this disclosure; therefore, for ease of understanding, dimensions, scales, or quantities may sometimes be exaggerated or simplified as needed.

[0036] <First Implementation>

[0037] The air conditioning unit 1 according to the first embodiment will now be described. The air conditioning unit 1 performs a refrigeration cycle. The air conditioning unit 1 is also referred to as a refrigeration unit. The air conditioning unit 1 regulates the indoor air. The air conditioning unit 1 cools the object being cooled. The object being cooled here includes the air inside equipment such as cold storage, freezer, and display cases. Hereinafter, the aforementioned equipment will be referred to as a cooling device. The air conditioning unit 1 is a multi-split air conditioning unit consisting of multiple units (first air conditioning unit 60A, second air conditioning unit 60B, and cooling device unit 70) connected to a heat source unit 10.

[0038] (1) Overall structure

[0039] Figure 1 This is a duct system diagram for air conditioning unit 1. (Example) Figure 1 As shown, the air conditioning unit 1 includes an outdoor heat source unit 10, an air conditioning unit 60 for regulating indoor air, and a cooling equipment unit 70 for cooling the air inside the storage room. The air conditioning unit 60 includes a first air conditioning unit 60A and a second air conditioning unit 60B connected in parallel with each other.

[0040] The air conditioning unit 1 includes four connecting pipes 2, 3, 4, and 5 that connect the heat source unit 10, the air conditioning unit 60, and the cooling equipment unit 70. In the air conditioning unit 1, the heat source unit 10, the air conditioning unit 60, and the cooling equipment unit 70 are connected through these connecting pipes 2, 3, 4, and 5, thereby forming a refrigerant circuit 6. In other words, the air conditioning unit 1 includes a refrigerant circuit 6.

[0041] Refrigerant circuit 6 contains pre-filled refrigerant. A refrigeration cycle is performed by circulating the refrigerant in refrigerant circuit 6. The refrigerant used in this embodiment is carbon dioxide. A refrigeration cycle is performed in refrigerant circuit 6, where the refrigerant is compressed to above a critical pressure.

[0042] (1-1) Connecting pipes

[0043] The four connecting pipes 2, 3, 4, and 5 consist of a first liquid connecting pipe 2, a first gas connecting pipe 3, a second liquid connecting pipe 4, and a second gas connecting pipe 5. The first liquid connecting pipe 2 and the first gas connecting pipe 3 correspond to the air conditioning unit 60. The second liquid connecting pipe 4 and the second gas connecting pipe 5 correspond to the cooling equipment unit 70.

[0044] (2) Heat source unit

[0045] The heat source unit 10 has a heat source circuit 11 and an outdoor fan 12. The heat source circuit 11 has a compressor 20, an outdoor heat exchanger 24, and a gas-liquid separator 25. The heat source circuit 11 has a first outdoor expansion valve 26 and a second outdoor expansion valve 27. The heat source circuit 11 also has a subcooled heat exchanger 28 and an intercooler 29.

[0046] The heat source circuit 11 has four shut-off valves 13, 14, 15, and 16. The four shut-off valves 13, 14, 15, and 16 are composed of a first gas shut-off valve 13, a first liquid shut-off valve 14, a second gas shut-off valve 15, and a second liquid shut-off valve 16.

[0047] A first gas connection pipe 3 is connected to the first gas shut-off valve 13. A first liquid connection pipe 2 is connected to the first liquid shut-off valve 14. A second gas connection pipe 5 is connected to the second gas shut-off valve 15. A second liquid connection pipe 4 is connected to the second liquid shut-off valve 16.

[0048] The heat source unit 10 has a flow path switching mechanism 30. Figure 1 In the piping system diagram of refrigerant circuit 6, a detailed illustration of the flow path switching mechanism 30 is omitted. The flow path switching mechanism 30 switches the flow path of the refrigerant in refrigerant circuit 6.

[0049] (2-1) Compressor

[0050] Compressor 20 compresses the refrigerant. Compressor 20 includes a first compressor 21, a second compressor 22, and a third compressor 23. Compressor 20 can perform single-stage compression and two-stage compression of the refrigerant.

[0051] The first compressor 21 is a cooling equipment compressor corresponding to the cooling equipment unit 70. The second compressor 22 is an air conditioning compressor corresponding to the air conditioning unit 60. The first compressor 21 and the second compressor 22 are low-level compressors. The first compressor 21 and the second compressor 22 are connected in parallel.

[0052] The third compressor 23 is an advanced compressor. The third compressor 23 is connected in series with the first compressor 21, or in series with the second compressor 22.

[0053] The first compressor 21, the second compressor 22, and the third compressor 23 are rotary compressors whose compression mechanisms are driven by electric motors. The first compressor 21, the second compressor 22, and the third compressor 23 are variable-capacity compressors. The speed of the electric motors of the first compressor 21, the second compressor 22, and the third compressor 23 is adjusted by a frequency converter. In other words, the first compressor 21, the second compressor 22, and the third compressor 23 are configured such that their operating capacity is adjustable.

[0054] A first suction pipe 21a is connected to the suction section of the first compressor 21. A first discharge pipe 21b is connected to the discharge section of the first compressor 21. A second suction pipe 22a is connected to the suction section of the second compressor 22. A second discharge pipe 22b is connected to the discharge section of the second compressor 22. A third suction pipe 23a is connected to the suction section of the third compressor 23. A third discharge pipe 23b is connected to the discharge section of the third compressor 23.

[0055] (2-2) Intermediate flow path

[0056] The heat source circuit 11 includes an intermediate flow path 18. The intermediate flow path 18 connects the ejection section of the first compressor 21 and the ejection section of the second compressor 22 to the suction section of the third compressor 23. The intermediate flow path 18 includes a first ejection pipe 21b, a second ejection pipe 22b, and a third suction pipe 23a.

[0057] (2-3) Outdoor heat exchanger and outdoor fan

[0058] The outdoor heat exchanger 24 is an example of an evaporator. The outdoor heat exchanger 24 is a finned-tube air heat exchanger. An outdoor fan 12 is arranged near the outdoor heat exchanger 24. The outdoor fan 12 delivers outdoor air. The outdoor heat exchanger allows the refrigerant flowing inside it to exchange heat with the outdoor air delivered by the outdoor fan 12.

[0059] (2-4) Liquid-side flow path

[0060] The heat source circuit 11 includes a liquid-side flow path 40. The liquid-side flow path 40 is located between the liquid-side end of the outdoor heat exchanger 24 and two liquid shut-off valves 14 and 16. The liquid-side flow path 40 includes a first pipe 40a, a second pipe 40b, a third pipe 40c, a fourth pipe 40d, and a fifth pipe 40e.

[0061] One end of the first pipe 40a is connected to the liquid side of the outdoor heat exchanger 24. The other end of the first pipe 40a is connected to the top of the gas-liquid separator 25. One end of the second pipe 40b is connected to the bottom of the gas-liquid separator 25. The other end of the second pipe 40b is connected to the second liquid shut-off valve 16. One end of the third pipe 40c is connected to the middle section of the second pipe 40b. The other end of the third pipe 40c is connected to the first liquid shut-off valve 14. One end of the fourth pipe 40d is connected to the portion of the first pipe 40a located between the first outdoor expansion valve 26 and the gas-liquid separator 25. The other end of the fourth pipe 40d is connected to the middle section of the third pipe 40c. One end of the fifth pipe 40e is connected to the portion of the first pipe 40a located between the outdoor heat exchanger 24 and the first outdoor expansion valve 26. The other end of the fifth pipe 40e is connected to the portion of the second pipe 40b located between the connection point of the second pipe 40b and the third pipe 40c and the gas-liquid separator 25.

[0062] (2-5) Outdoor expansion valve

[0063] The first outdoor expansion valve 26 is installed on the first pipe 40a. The first outdoor expansion valve 26 is located on the first pipe 40a between the liquid side end of the outdoor heat exchanger 24 and the connection between the first pipe 40a and the fourth pipe 40d. The second outdoor expansion valve 27 is installed on the fifth pipe 40e. Both the first outdoor expansion valve 26 and the second outdoor expansion valve 27 are adjustable expansion valves. Both the first outdoor expansion valve 26 and the second outdoor expansion valve 27 are electronic expansion valves whose opening is adjusted according to a pulse signal.

[0064] (2-6) Gas-liquid separator

[0065] The gas-liquid separator 25 is also called a liquid receiver. The gas-liquid separator 25 is a sealed container for storing refrigerant. The gas-liquid separator 25 separates the refrigerant into gaseous and liquid refrigerant. A gas storage section 25a and a liquid storage section 25b are formed inside the gas-liquid separator 25. The gas storage section 25a is formed on the top side of the gas-liquid separator 25. The liquid storage section 25b is formed on the bottom side of the gas-liquid separator 25.

[0066] (2-7) Exhaust pipe

[0067] The heat source circuit 11 has an exhaust pipe 41. The exhaust pipe 41 is an example of an exhaust passage. One end of the exhaust pipe 41 is connected to the gas storage section 25a located at the top of the gas-liquid separator 25. The other end of the exhaust pipe 41 is connected to the intermediate flow path 18. The exhaust pipe 41 delivers the gaseous refrigerant in the gas-liquid separator 25 to the intermediate flow path 18. The exhaust pipe 41 connects the gas storage section 25a of the gas-liquid separator 25 to the suction side 20i of the third compressor 23, which is a high-level compressor.

[0068] An exhaust valve 42 is provided on the exhaust pipe 41. The exhaust valve 42 is an example of a switch valve. The exhaust valve 42 is an expansion valve whose opening degree can be adjusted. The exhaust valve 42 is an electronic expansion valve whose opening degree is adjusted based on a pulse signal. The exhaust valve 42 can also be an electric valve or a solenoid switch valve, etc.

[0069] (2-8) Subcooled heat exchanger

[0070] The subcooled heat exchanger 28 has a first flow path 28a as a high-pressure side flow path and a second flow path 28b as a low-pressure side flow path. The subcooled heat exchanger 28 allows heat exchange between the refrigerant in the first flow path 28a and the refrigerant in the second flow path 28b. In other words, the subcooled heat exchanger 28 uses the refrigerant flowing in the second flow path 28b to cool the refrigerant flowing in the first flow path 28a.

[0071] The second flow path 28b forms part of the injection flow path 43. The injection flow path 43 includes an upstream flow path 44 and a downstream flow path 45.

[0072] One end of the upstream flow path 44 is connected to the third pipe 40c at a position further upstream than the connection point to the fourth pipe 40d. The other end of the upstream flow path 44 is connected to the inflow end of the second flow path 28b. An injection valve 46, serving as a subcooling-side pressure reducing valve, is provided on the upstream flow path 44. The injection valve 46 is an expansion valve whose opening is adjustable. The injection valve 46 is an electronic expansion valve whose opening is adjusted based on a pulse signal.

[0073] One end of the downstream flow path 45 is connected to the outlet end of the second flow path 28b. The other end of the downstream flow path 45 is connected to the intermediate flow path 18.

[0074] (2-9) Intercooler

[0075] An intercooler 29 is disposed in the intermediate flow path 18. The intercooler 29 is a finned tube type air heat exchanger. A cooling fan 29a is arranged near the intercooler 29. The intercooler 29 allows the refrigerant flowing inside it to exchange heat with the outdoor air supplied by the cooling fan 29a.

[0076] (2-10) Oil separation circuit

[0077] The heat source circuit 11 includes an oil separation circuit. The oil separation circuit has an oil separator 50, a first return oil pipe 51, and a second return oil pipe 52.

[0078] Oil separator 50 is connected to the third discharge pipe 23b. Oil separator 50 separates oil from the refrigerant discharged from compressor 20. The inflow ends of the first oil return pipe 51 and the second oil return pipe 52 are connected to oil separator 50. The outflow end of the first oil return pipe 51 is connected to intermediate flow path 18. A first oil quantity regulating valve 53 is provided on the first oil return pipe 51.

[0079] The outflow side of the second return oil pipe 52 is split into a first branch pipe 52a and a second branch pipe 52b. The first branch pipe 52a is connected to the oil storage section of the first compressor 21. The second branch pipe 52b is connected to the oil storage section of the second compressor 22. A second oil quantity regulating valve 54 is provided on the first branch pipe 52a. A third oil quantity regulating valve 55 is provided on the second branch pipe 52b.

[0080] (2-11) Bypass pipe

[0081] The heat source circuit 11 has a first bypass pipe 56, a second bypass pipe 57, and a third bypass pipe 58. The first bypass pipe 56 corresponds to the first compressor 21. The second bypass pipe 57 corresponds to the second compressor 22. The third bypass pipe 58 corresponds to the third compressor 23.

[0082] Specifically, the first bypass pipe 56 directly connects the first suction pipe 21a to the first discharge pipe 21b. The second bypass pipe 57 directly connects the second suction pipe 22a to the second discharge pipe 22b. The third bypass pipe 58 directly connects the third suction pipe 23a to the third discharge pipe 23b.

[0083] (2-12) Check valve

[0084] The heat source circuit 11 has multiple check valves. These check valves include a first check valve CV1 through a twelfth check valve CV12. These check valves CV1 through CV12 allow refrigerant to flow towards... Figure 1 The refrigerant should flow in the direction of the arrow, and flow in the opposite direction of the arrow is prohibited.

[0085] The first check valve CV1 and the second check valve CV2 are installed on the flow path switching mechanism 30.

[0086] The third check valve CV3 is installed on the third discharge pipe 23b. The fourth check valve CV4 is installed on the first pipe 40a. The fifth check valve CV5 is installed on the third pipe 40c. The sixth check valve CV6 is installed on the fourth pipe 40d. The seventh check valve CV7 is installed on the fifth pipe 40e. The eighth check valve CV8 is installed on the first bypass pipe 56. The ninth check valve CV9 is installed on the second bypass pipe 57. The tenth check valve CV10 is installed on the third bypass pipe 58. The eleventh check valve CV11 is installed on the first discharge pipe 21b. The twelfth check valve CV12 is installed on the second discharge pipe 22b.

[0087] (3) Air conditioning unit

[0088] Figure 2 This is a piping system diagram near air conditioning unit 60. Air conditioning unit 60 is an indoor unit. Air conditioning unit 60 has an indoor circuit 61 and an indoor fan 62. A first liquid connection pipe 2 is connected to the liquid side of indoor circuit 61. A first gas connection pipe 3 is connected to the gas side of indoor circuit 61. Indoor fan 62 is an example of a fan.

[0089] like Figure 2 As shown, the indoor circuit 61, from the liquid side to the gas side, includes an indoor expansion valve 63 and an indoor heat exchanger 64 in sequence. The indoor expansion valve 63 is an example of an expansion valve. The indoor expansion valve 63 is an expansion valve whose opening degree is adjustable. The indoor expansion valve 63 is an electronic expansion valve whose opening degree is adjusted based on a pulse signal.

[0090] The indoor heat exchanger 64 is a finned tube air heat exchanger. The indoor heat exchanger 64 is an example of a radiator. An indoor fan 62 is arranged near the indoor heat exchanger 64. The indoor fan 62 delivers indoor air. The indoor heat exchanger 64 allows the refrigerant flowing within it to exchange heat with the indoor air delivered by the indoor fan 62.

[0091] Air conditioning unit 60 includes a first air conditioning unit 60A and a second air conditioning unit 60B connected in parallel. Air conditioning unit 60 is an example of a utilizing unit. The first air conditioning unit 60A is an example of a first utilizing unit. The second air conditioning unit 60B is an example of a second utilizing unit. Indoor circuit 61 includes a first indoor circuit 61A and a second indoor circuit 61B connected in parallel. The first indoor circuit 61A corresponds to the first air conditioning unit 60A. The second indoor circuit 61B corresponds to the second air conditioning unit 60B.

[0092] The indoor heat exchanger 64 includes a first indoor heat exchanger 64A and a second indoor heat exchanger 64B connected in parallel with each other. The first indoor heat exchanger 64A is an example of a first radiator. The second indoor heat exchanger 64B is an example of a second radiator.

[0093] The indoor expansion valve 63 includes a first indoor expansion valve 63A corresponding to the first indoor heat exchanger 64A and a second indoor expansion valve 63B corresponding to the second indoor heat exchanger 64B. The first indoor expansion valve 63A is an example of a first expansion valve. The second indoor expansion valve 63B is an example of a second expansion valve. The indoor fan 62 includes a first indoor fan 62A corresponding to the first indoor heat exchanger 64A and a second indoor fan 62B corresponding to the second indoor heat exchanger 64B. The first indoor fan 62A is an example of a first fan. The second indoor fan 62B is an example of a second fan.

[0094] (4) Cooling equipment unit

[0095] The cooling equipment unit 70 is a unit used for cooling the warehouse. The cooling equipment unit 70 includes a cooling equipment circuit 71 and a cooling equipment fan 72. A second liquid connection pipe 4 is connected to the liquid side of the cooling equipment circuit 71. A second gas connection pipe 5 is connected to the gas side of the cooling equipment circuit 71.

[0096] The cooling equipment circuit 71 includes, sequentially from the liquid side to the gas side, a cooling equipment expansion valve 73 and a cooling equipment heat exchanger 74. The cooling equipment expansion valve 73 is an expansion valve whose opening is adjustable. The cooling equipment expansion valve 73 is an electronic expansion valve whose opening is adjusted based on pulse signals.

[0097] The cooling equipment heat exchanger 74 is a finned tube air heat exchanger. A cooling equipment fan 72 is arranged near the cooling equipment heat exchanger 74. The cooling equipment fan 72 delivers air from the storage area. The cooling equipment heat exchanger 74 allows the refrigerant flowing within it to exchange heat with the air delivered by the cooling equipment fan 72.

[0098] (5) Flow path switching mechanism

[0099] A flow path switching mechanism 30 is provided in the heat source circuit 11. The flow path switching mechanism 30 switches the flow path of the refrigerant circuit 6, at least between the first refrigeration cycle and the second refrigeration cycle. The first refrigeration cycle is a refrigeration cycle in which the outdoor heat exchanger 24 functions as a radiator, and the indoor heat exchanger 64 and the cooling equipment heat exchanger 74 function as evaporators. The second refrigeration cycle is a refrigeration cycle in which the outdoor heat exchanger 24 functions as an evaporator, and the indoor heat exchanger 64 and the cooling equipment heat exchanger 74 function as radiators.

[0100] The flow path switching mechanism 30 has a first valve port P1, a second valve port P2, a third valve port P3, a fourth valve port P4, and switches between the first flow path 31, the second flow path 32, the third flow path 33, and the fourth flow path 34. Each switching flow path 31 to 34 is equipped with a switching mechanism (not shown). Each switching mechanism includes a switching valve and an expansion valve.

[0101] The first valve port P1 is connected to the discharge section of the third compressor 23. The second valve port P2 is connected to the suction section of the second compressor 22. The third valve port P3 is connected to the air-side end of the indoor heat exchanger 64. The fourth valve port P4 is connected to the air-side end of the outdoor heat exchanger 24.

[0102] The first flow path 31, the second flow path 32, the third flow path 33, and the fourth flow path 34 are connected in a bridge configuration. Switching the first flow path 31 connects the first valve port P1 to the third valve port P3. Switching the second flow path 32 connects the first valve port P1 to the fourth valve port P4. Switching the third flow path 33 connects the second valve port P2 to the third valve port P3. Switching the fourth flow path 34 connects the second valve port P2 to the fourth valve port P4.

[0103] A first check valve CV1 is provided in the switching fourth flow path 34. A second check valve CV2 is provided in the switching first flow path 31. The first check valve CV1 allows refrigerant to flow from the fourth valve port P4 towards the second valve port P2 in the switching fourth flow path 34, and prohibits refrigerant from flowing from the second valve port P2 towards the fourth valve port P4. The second check valve CV2 allows refrigerant to flow from the first valve port P1 towards the third valve port P3 in the switching first flow path 31, and prohibits refrigerant from flowing from the third valve port P3 towards the first valve port P1.

[0104] (6) Sensors

[0105] The air conditioning unit 1 has multiple sensors. These sensors include a refrigerant pressure sensor for detecting the pressure of the refrigerant, a refrigerant temperature sensor for detecting the temperature of the refrigerant, and an air temperature sensor for detecting the temperature of the air.

[0106] The refrigerant pressure sensor includes a high-pressure pressure sensor 101, an intermediate pressure sensor 102, a first suction pressure sensor 103, a second suction pressure sensor 104, and a receiver pressure sensor 105. The high-pressure pressure sensor 101 is mounted on the third discharge pipe 23b. The high-pressure pressure sensor 101 detects the pressure of the refrigerant on the discharge side of the compressor 20, in other words, it detects the high-pressure Ph of the refrigerant circuit 6.

[0107] An intermediate pressure sensor 102 is installed on the third suction pipe 23a. The intermediate pressure sensor 102 detects the refrigerant pressure between the low-stage compressor and the high-stage compressor; in other words, it detects the intermediate pressure of the refrigerant circuit 6. A first suction pressure sensor 103 is installed on the first suction pipe 21a. The first suction pressure sensor 103 detects the refrigerant pressure on the suction side of the first compressor 21. A second suction pressure sensor 104 is installed on the second suction pipe 22a. The second suction pressure sensor 104 detects the refrigerant pressure on the suction side of the second compressor 22.

[0108] A receiver pressure sensor 105 is disposed in the liquid-side flow path 40. Specifically, the receiver pressure sensor 105 is disposed on the second pipe 40b. The receiver pressure sensor 105 detects a pressure equivalent to the internal pressure of the gas-liquid separator 25 (the receiver pressure Pd described later). The receiver pressure sensor 105 detects a pressure equivalent to the pressure of the refrigerant in the first flow path 28a. It should be noted that the receiver pressure sensor 105 can also be a sensor that detects the pressure of the refrigerant in the gas-liquid separator 25.

[0109] The refrigerant temperature sensor includes a first ejection temperature sensor 111, a first suction temperature sensor 112, a second ejection temperature sensor 113, a second suction temperature sensor 114, a third ejection temperature sensor 115, a third suction temperature sensor 116, a liquid-side temperature sensor 117, an injection-side temperature sensor 118, an outdoor heat exchanger liquid-side temperature sensor 119, an outdoor heat exchanger gas-side temperature sensor 120, an indoor heat exchanger liquid-side temperature sensor 121, and an indoor heat exchanger gas-side temperature sensor 122.

[0110] A first discharge temperature sensor 111 is installed on the first discharge pipe 21b to detect the temperature of the refrigerant discharged from the first compressor 21. A first suction temperature sensor 112 is installed on the first suction pipe 21a to detect the temperature of the refrigerant drawn into the first compressor 21. A second discharge temperature sensor 113 is installed on the second discharge pipe 22b to detect the temperature of the refrigerant discharged from the second compressor 22. A second suction temperature sensor 114 is installed on the second suction pipe 22a to detect the temperature of the refrigerant drawn into the second compressor 22. A third discharge temperature sensor 115 is installed on the third discharge pipe 23b to detect the temperature of the refrigerant discharged from the third compressor 23. A third suction temperature sensor 116 is installed on the third suction pipe 23a to detect the temperature of the refrigerant drawn into the third compressor 23.

[0111] A liquid-side temperature sensor 117 is disposed on the liquid-side flow path 40. Specifically, the liquid-side temperature sensor 117 is disposed on the outlet side of the first flow path 28a of the subcooled heat exchanger 28 on the liquid-side flow path 40. The liquid-side temperature sensor 117 detects the temperature of the refrigerant flowing out of the first flow path 28a.

[0112] An injection-side temperature sensor 118 is disposed on the downstream flow path 45 of the injection flow path 43. In other words, the injection-side temperature sensor 118 is disposed on the outflow side of the second flow path 28b of the subcooled heat exchanger 28. The injection-side temperature sensor 118 detects the temperature of the refrigerant flowing out of the second flow path 28b.

[0113] The outdoor heat exchanger liquid-side temperature sensor 119 is installed on the heat transfer tube of the outdoor heat exchanger 24. The outdoor heat exchanger liquid-side temperature sensor 119 is located at the liquid-side end of the outdoor heat exchanger 24. The outdoor heat exchanger liquid-side temperature sensor 119 detects the temperature of the refrigerant at the liquid-side end of the outdoor heat exchanger 24.

[0114] An outdoor heat exchanger gas-side temperature sensor 120 is installed on the heat transfer tube of the outdoor heat exchanger 24. The outdoor heat exchanger gas-side temperature sensor 120 is located at the gas-side end of the outdoor heat exchanger 24. The outdoor heat exchanger gas-side temperature sensor 120 detects the temperature of the refrigerant at the gas-side end of the outdoor heat exchanger 24.

[0115] An indoor heat exchanger liquid-side temperature sensor 121 is disposed on the heat transfer tube of the indoor heat exchanger 64. The indoor heat exchanger liquid-side temperature sensor 121 is located at the liquid-side end of the indoor heat exchanger 64. The indoor heat exchanger liquid-side temperature sensor 121 detects the temperature of the refrigerant at the liquid-side end of the indoor heat exchanger 64. The indoor heat exchanger liquid-side temperature sensor 121 includes a first indoor heat exchanger liquid-side temperature sensor 121A and a second indoor heat exchanger liquid-side temperature sensor 121B.

[0116] The liquid-side temperature sensor 121A corresponds to the first indoor heat exchanger 64A. The liquid-side temperature sensor 121A is installed on the heat transfer tube of the first indoor heat exchanger 64A. The liquid-side temperature sensor 121A is located at the liquid-side end of the first indoor heat exchanger 64A. The liquid-side temperature sensor 121A detects the temperature of the refrigerant at the liquid-side end of the first indoor heat exchanger 64A.

[0117] The liquid-side temperature sensor 121B of the second indoor heat exchanger corresponds to the second indoor heat exchanger 64B. The liquid-side temperature sensor 121B is installed on the heat transfer tube of the second indoor heat exchanger 64B. The liquid-side temperature sensor 121B is located at the liquid-side end of the second indoor heat exchanger 64B. The liquid-side temperature sensor 121B detects the temperature of the refrigerant at the liquid-side end of the second indoor heat exchanger 64B.

[0118] An indoor heat exchanger gas-side temperature sensor 122 is disposed on the heat transfer tube of the indoor heat exchanger 64. The indoor heat exchanger gas-side temperature sensor 122 is disposed at the gas-side end of the indoor heat exchanger 64. The indoor heat exchanger gas-side temperature sensor 122 detects the temperature of the refrigerant at the gas-side end of the indoor heat exchanger 64. The indoor heat exchanger gas-side temperature sensor 122 includes a first indoor heat exchanger gas-side temperature sensor 122A and a second indoor heat exchanger gas-side temperature sensor 122B.

[0119] The first indoor heat exchanger gas-side temperature sensor 122A corresponds to the first indoor heat exchanger 64A. The first indoor heat exchanger gas-side temperature sensor 122A is installed on the heat transfer tube of the first indoor heat exchanger 64A. The first indoor heat exchanger gas-side temperature sensor 122A is located at the gas-side end of the first indoor heat exchanger 64A. The first indoor heat exchanger gas-side temperature sensor 122A detects the temperature of the refrigerant at the gas-side end of the first indoor heat exchanger 64A.

[0120] The second indoor heat exchanger gas-side temperature sensor 122B corresponds to the second indoor heat exchanger 64B. The second indoor heat exchanger gas-side temperature sensor 122B is installed on the heat transfer tube of the second indoor heat exchanger 64B. The second indoor heat exchanger gas-side temperature sensor 122B is located at the gas-side end of the second indoor heat exchanger 64B. The second indoor heat exchanger gas-side temperature sensor 122B detects the temperature of the refrigerant at the gas-side end of the second indoor heat exchanger 64B.

[0121] The air temperature sensor includes an outdoor air temperature sensor 123 and an indoor temperature sensor 124. The outdoor air temperature sensor 123 detects the temperature of the outdoor air.

[0122] The indoor temperature sensor 124 detects the indoor temperature of the room where the air conditioning unit 60 (indoor heat exchanger 64) is installed. The indoor temperature sensor 124 includes a first indoor temperature sensor 124A and a second indoor temperature sensor 124B.

[0123] The first indoor temperature sensor 124A detects the indoor temperature of the room where the first air conditioning unit 60A (first indoor heat exchanger 64A) is installed. The second indoor temperature sensor 124B detects the indoor temperature of the room where the second air conditioning unit 60B (second indoor heat exchanger 64B) is installed.

[0124] (7) Controller

[0125] Figure 3 This is a block diagram illustrating the connection relationship between the controller 130, which serves as a control device, and peripheral devices. The air conditioning unit 1 includes the controller 130. The controller 130 is an example of a control device. The controller 130 controls the refrigerant circuit 6. The controller 130 includes a microcomputer mounted on a control board and a storage device (specifically, a semiconductor memory) storing software for operating the microcomputer.

[0126] like Figure 3 As shown, the controller 130 includes an outdoor controller 131, an indoor controller 132, and a cooling equipment controller 133. (As...) Figure 1As shown, the outdoor controller 131 is installed in the heat source unit 10. The indoor controller 132 is installed in the air conditioning unit 60. The cooling equipment controller 133 is installed in the cooling equipment unit 70. The outdoor controller 131 can communicate with the indoor controller 132 and the cooling equipment controller 133.

[0127] The indoor controller 132 includes a first indoor controller 132A and a second indoor controller 132B connected in parallel. The first indoor controller 132A corresponds to the first air conditioning unit 60A. The second indoor controller 132B corresponds to the second air conditioning unit 60B.

[0128] The controller 130 receives control commands from the user and detection signals from various sensors. The controller 130 controls the various components of the air conditioning unit 1. Specifically, the controller 130 controls the on / off state of the first compressor 21, the second compressor 22, and the third compressor 23. The controller 130 adjusts the capacity (strictly speaking, the motor speed) of the first compressor 21, the second compressor 22, and the third compressor 23. The controller 130 controls the on / off state of each fan. The controller 130 adjusts the opening degree of each expansion valve. The controller 130 switches the opening and closing of each valve.

[0129] (8) Heating operation

[0130] (8-1) Operation of the air conditioning unit during heating

[0131] The operation of air conditioning unit 1 will be described. The operation of air conditioning unit 1 includes cooling equipment operation, refrigeration operation, refrigeration / cooling equipment operation, heating operation, heating / cooling equipment operation, and defrosting operation. In this example, only heating operation will be described. During heating operation, the cooling equipment unit 70 stops, and the air conditioning unit 60 heats the room. Figure 1 The thick lines in the middle represent the flow of refrigerant during heating operation.

[0132] like Figure 1 As shown, during heating operation, the controller 130 closes the switching second flow path 32 and the switching third flow path 33 and opens the switching first flow path 31 and the switching fourth flow path 34 by controlling the switching valves set on each switching flow path 31 to 34.

[0133] Controller 130 stops the first compressor 21 and starts the second compressor 22 and the third compressor 23. Controller 130 opens the second outdoor expansion valve 27 and the injection valve 46 to a predetermined degree and closes the first outdoor expansion valve 26. Controller 130 closes the cooling equipment expansion valve 73 and opens the indoor expansion valve 63. Controller 130 starts the outdoor fan 12 and the indoor fan 62 and stops the cooling equipment fan 72.

[0134] During heating operation, the following refrigeration cycle is performed, in which the indoor heat exchanger 64 functions as a radiator, the outdoor heat exchanger 24 functions as an evaporator, and the function of the cooling equipment heat exchanger 74 is substantially stopped.

[0135] Specifically, the refrigerant compressed by the second compressor 22 is cooled in the intercooler 29 and then drawn into the third compressor 23. The refrigerant compressed by the third compressor 23 is then sent to the air conditioning unit 60.

[0136] The refrigerant delivered to the air conditioning unit 60 dissipates heat in the indoor heat exchanger 64. As a result, the indoor air is heated. After dissipating heat in the indoor heat exchanger 64, the refrigerant flows into the gas-liquid separator 25. In the gas-liquid separator 25, the refrigerant is separated into gaseous refrigerant and liquid refrigerant.

[0137] The liquid refrigerant separated in the gas-liquid separator 25 is cooled by the refrigerant flowing through the injection path 43 in the subcooled heat exchanger 28. The refrigerant in the injection path 43 is then sent to the intermediate path 18.

[0138] The refrigerant, having been cooled by the subcooled heat exchanger 28, is depressurized by the second outdoor expansion valve 27 and then evaporates in the outdoor heat exchanger 24. The refrigerant evaporated in the outdoor heat exchanger 24 is then drawn into the second compressor 22 and compressed again.

[0139] (8-2) Components of an air conditioning unit during heating

[0140] In heating operation, the refrigerant circuit 6 includes a second compressor 22 in the compressor 20, a third compressor 23 in the compressor 20, an indoor heat exchanger 64 as a radiator, an indoor expansion valve 63 as an expansion valve, and an outdoor heat exchanger 24 as an evaporator.

[0141] The air conditioning unit 60, which is a first air conditioning unit 60A as a first utilization unit, includes a second air conditioning unit 60B as a second utilization unit. The first air conditioning unit 60A and the second air conditioning unit 60B are connected in parallel with each other.

[0142] The indoor heat exchanger 64, which serves as a radiator, includes a first indoor heat exchanger 64A as a first radiator and a second indoor heat exchanger 64B as a second radiator. The first indoor heat exchanger 64A and the second indoor heat exchanger 64B are connected in parallel with each other.

[0143] The indoor expansion valve 63, which serves as an expansion valve, includes a first indoor expansion valve 63A corresponding to the first indoor heat exchanger 64A and a second indoor expansion valve 63B corresponding to the second indoor heat exchanger 64B. The first indoor expansion valve 63A and the second indoor expansion valve 63B are connected in parallel with each other.

[0144] The indoor fan 62, which functions as a fan, includes a first indoor fan 62A corresponding to the first indoor heat exchanger 64A and a second indoor fan 62B corresponding to the second indoor heat exchanger 64B. The first indoor fan 62A and the second indoor fan 62B are connected in parallel.

[0145] An indoor heat exchanger 64 serving as a radiator, an indoor expansion valve 63 serving as an expansion valve, and an indoor fan 62 serving as a fan constitute an air conditioning unit 60 that utilizes the unit.

[0146] The first indoor heat exchanger 64A, which serves as the first radiator, the first indoor expansion valve 63A, which serves as the first expansion valve, and the first indoor fan 62A, which serves as the first fan, constitute the first air conditioning unit 60A as the first utilization unit.

[0147] The second indoor heat exchanger 64B, which serves as the second radiator, the second indoor expansion valve 63B, which serves as the second expansion valve, and the second indoor fan 62B, which serves as the second fan, constitute the second air conditioning unit 60B as the second utilization unit.

[0148] The refrigerant circuit 6 has a gas-liquid separator 25, an exhaust pipe 41 as an exhaust passage, and an exhaust valve 42 as a switching valve.

[0149] The gas-liquid separator 25 is connected downstream of the indoor heat exchanger 64 during heating operation. The gas-liquid separator 25 separates the refrigerant into gaseous and liquid refrigerant. A gas storage section 25a and a liquid storage section 25b are formed inside the gas-liquid separator 25. The gas storage section 25a is located at the top of the gas-liquid separator 25 and stores the gaseous refrigerant. The liquid storage section 25b is located at the bottom of the gas-liquid separator 25 and stores the liquid refrigerant.

[0150] One end of the exhaust pipe 41 is connected to the gas storage section 25a of the gas-liquid separator 25. The other end of the exhaust pipe 41 is connected to the intermediate flow path 18. The intermediate flow path 18 is connected to the third suction pipe 23a of the suction side 20i of the third compressor 23 located in the compressor 20.

[0151] The exhaust pipe 41 connects the gas storage section 25a of the gas-liquid separator 25 to the third suction pipe 23a of the suction side 20i of the third compressor 23 in the compressor 20 via the intermediate flow path 18. The exhaust valve 42 is provided on the exhaust pipe 41.

[0152] High-pressure sensor 101 detects the high-pressure in refrigerant circuit 6. The high-pressure in refrigerant circuit 6 is also the pressure of the refrigerant on the discharge side of the third compressor 23.

[0153] The indoor heat exchanger liquid-side temperature sensor 121 detects the temperature of the refrigerant at the liquid-side end of the indoor heat exchanger 64. During heating operation, the indoor heat exchanger liquid-side temperature sensor 121 detects the outlet refrigerant temperature TE, which is the refrigerant temperature at the outlet E of the indoor heat exchanger 64. The indoor heat exchanger liquid-side temperature sensor 121 includes a first indoor heat exchanger liquid-side temperature sensor 121A and a second indoor heat exchanger liquid-side temperature sensor 121B.

[0154] The liquid-side temperature sensor 121A of the first indoor heat exchanger 64A detects the temperature of the refrigerant at the liquid-side end of the first indoor heat exchanger 64A. During heating operation, the liquid-side temperature sensor 121A detects the first outlet refrigerant temperature TEA, which is the refrigerant temperature at the first outlet EA of the first indoor heat exchanger 64A. The first outlet refrigerant temperature TEA corresponds to the first indoor heat exchanger 64A. The liquid-side temperature sensor 121B of the second indoor heat exchanger 64B detects the temperature of the refrigerant at the liquid-side end of the second indoor heat exchanger 64B. During heating operation, the liquid-side temperature sensor 121B detects the second outlet refrigerant temperature TEB, which is the refrigerant temperature at the second outlet EB of the second indoor heat exchanger 64B. The second outlet refrigerant temperature TEB corresponds to the second indoor heat exchanger 64B.

[0155] The indoor heat exchanger gas-side temperature sensor 122 detects the temperature of the refrigerant at the gas-side end of the indoor heat exchanger 64. During heating operation, the indoor heat exchanger gas-side temperature sensor 122 detects the inlet refrigerant temperature TI, which is the refrigerant temperature at the inlet I of the indoor heat exchanger 64. The indoor heat exchanger gas-side temperature sensor 122 includes a first indoor heat exchanger gas-side temperature sensor 122A and a second indoor heat exchanger gas-side temperature sensor 122B.

[0156] The first indoor heat exchanger air-side temperature sensor 122A detects the temperature of the refrigerant at the air-side end of the first indoor heat exchanger 64A. During heating operation, the first indoor heat exchanger air-side temperature sensor 122A detects the first inlet refrigerant temperature TIA, which is the refrigerant temperature at the first inlet IA of the first indoor heat exchanger 64A. The first inlet refrigerant temperature TIA corresponds to the first indoor heat exchanger 64A. The second indoor heat exchanger air-side temperature sensor 122B detects the temperature of the refrigerant at the air-side end of the second indoor heat exchanger 64B. During heating operation, the second indoor heat exchanger air-side temperature sensor 122B detects the second inlet refrigerant temperature TIB, which is the refrigerant temperature at the second inlet IB of the second indoor heat exchanger 64B. The second inlet refrigerant temperature TIB corresponds to the second indoor heat exchanger 64B.

[0157] Indoor temperature sensor 124 detects the indoor temperature TR within an indoor space RA, which is a utilized space equipped with air conditioning unit 60 (indoor heat exchanger 64). Indoor space R is an example of a utilized space. Indoor space R corresponds to air conditioning unit 60.

[0158] The indoor space R includes a first indoor space RA, which serves as a first utilization side space, and a second indoor space RB, which serves as a second utilization side space. The first indoor space RA is an example of the first utilization side space. The first indoor space RA corresponds to the first air conditioning unit 60A. The second indoor space RB is an example of the second utilization side space. The second indoor space RB corresponds to the second air conditioning unit 60B.

[0159] The indoor temperature sensor 124 includes a first indoor temperature sensor 124A and a second indoor temperature sensor 124B. The first indoor temperature sensor 124A detects the first indoor temperature TRA in a first indoor space RA where a first air conditioning unit 60A (first indoor heat exchanger 64A) is installed. The first indoor temperature TRA corresponds to the first indoor heat exchanger 64A. The second indoor temperature sensor 124B detects the second indoor temperature TRB in a second indoor space RB where a second air conditioning unit 60B (second indoor heat exchanger 64B) is installed. The second indoor temperature TRB corresponds to the second indoor heat exchanger 64B.

[0160] The reservoir pressure sensor 105 detects the reservoir pressure Pd, which is the pressure of the gas-liquid separator 25.

[0161] (9) Supercritical operation

[0162] Figure 4 It is a graph showing the relationship between the specific enthalpy h of the refrigerant and the pressure P. Figure 4Also known as the P-h diagram. The refrigerant circulating in refrigerant loop 6 is carbon dioxide. The critical pressure Pc at the critical point C of carbon dioxide as a refrigerant is lower than that of other natural refrigerants; specifically, it is 7.38 MPa in absolute pressure. The critical temperature Tc at the critical point C of carbon dioxide as a refrigerant is 31.1 °C. The critical specific enthalpy hc at the critical point C of carbon dioxide as a refrigerant is approximately 330 kJ / kg. The critical pressure Pc, critical temperature Tc, and critical specific enthalpy hc correspond to each other.

[0163] The refrigerant circuit 6 performs a refrigeration cycle for heating operation by compressing the refrigerant to a critical pressure above Pc. In this heating operation, the indoor space R, which is the utilization side space, is heated.

[0164] Refrigerant circuit 6 operates in supercritical mode. The high-pressure Ph of refrigerant circuit 6 becomes above the critical pressure Pc.

[0165] When the refrigerant is compressed to a pressure above the critical pressure Pc, in other words, when the high pressure Ph of the refrigerant circuit 6 reaches a pressure above the critical pressure Pc, it is difficult to control the temperature of the refrigerant because there is no condensation temperature of the refrigerant in the region above the critical pressure Pc.

[0166] The smaller the specific enthalpy (h) of a refrigerant, the greater the proportion of liquid and the smaller the proportion of gas in the refrigerant. Conversely, the greater the specific enthalpy (h) of a refrigerant, the smaller the proportion of liquid and the greater the proportion of gas in the refrigerant.

[0167] like Figure 4 As shown, the outlet specific enthalpy he of the refrigerant at outlet E of the indoor heat exchanger 64 is less than the critical specific enthalpy hc at the critical point C of the refrigerant. Compared with the refrigerant at the critical point C, the refrigerant at outlet E of the indoor heat exchanger 64 has a larger proportion of liquid and a smaller proportion of gas.

[0168] (10) Stop mode

[0169] The controller 130 executes a stop mode M1 and an operation mode M2 ​​for the first air conditioning unit 60A and the second air conditioning unit 60B. Specifically, the stop mode M1 is the thermo-off mode. In this example, the first air conditioning unit 60A is in stop mode M1 and the second air conditioning unit 60B is in operation mode M2. Figure 5 This is a piping system diagram showing the first air conditioning unit 60A in stop mode M1 and the second air conditioning unit 60B in operation mode M2.

[0170] It should be noted that, Figure 5The thickness of the solid line indicates the flow rate, which in turn indicates the opening degree of the first indoor expansion valve 63A and the second indoor expansion valve 63B. Figure 5 The diagram above represents the first state J1, which will be described later. Figure 5 The following diagram represents the second state J2, which will be described later.

[0171] When the first air conditioning unit 60A is in stop mode M1 and the second air conditioning unit 60B is in operation mode M2, the controller 130 causes the opening degree of the first indoor expansion valve 63A to be less than the opening degree of the second indoor expansion valve 63B. The opening degree of the second indoor expansion valve 63B in operation mode M2 ​​is, for example, fully open (100%). The opening degree of the first indoor expansion valve 63A in stop mode M1 will be described later.

[0172] When the first air conditioning unit 60A is in stop mode M1, the controller 130 controls the first indoor expansion valve 63A to switch between the first state J1 and the second state J2. In the first state J1, the first indoor expansion valve 63A is completely closed (0%). In the second state J2, the first indoor expansion valve 63A is opened more than in the first state J1. However, the opening degree of the first indoor expansion valve 63A in the second state J2 is greater than the opening degree of the second indoor expansion valve 63B in operation mode M2. The opening degree of the first indoor expansion valve 63A in the second state J2 is, for example, about a few percent.

[0173] In operating mode M2, the second indoor fan 62B operates. In stop mode M1, the first indoor fan 62A stops or operates at a lower load than in operating mode M2.

[0174] If the first indoor expansion valve 63A is in the first state J1 (fully closed), liquid refrigerant will accumulate in the first indoor heat exchanger 64A. Therefore, when the stop mode M1 starts, the first indoor expansion valve 63A is in the second state J2.

[0175] On the other hand, if the first indoor expansion valve 63A is in the second state J2, the liquid reservoir pressure Pd of the gas-liquid separator 25 will rise. In the second state J2, the liquid reservoir pressure Pd of the gas-liquid separator 25 rises because the air conditioning unit 1 is operating in a supercritical manner.

[0176] Therefore, the controller 130 switches the expansion valve 63A in the first chamber from the second state J2 to the first state J1 based on the rise in the reservoir pressure Pd, which is the pressure of the gas-liquid separator 25. It should be noted that the rise in the reservoir pressure Pd of the gas-liquid separator 25 can be directly measured by the reservoir pressure sensor 105, or it can be indirectly determined by other methods, which will be described later.

[0177] When the difference between the first inlet refrigerant temperature TIA at the first inlet IA of the first indoor heat exchanger 64A and the first outlet refrigerant temperature TEA at the first outlet EA of the first indoor heat exchanger 64A is greater than a first value Q1, the controller 130 switches the first indoor expansion valve 63A from the second state J2 to the first state J1. This difference is obtained by subtracting the first outlet refrigerant temperature TEA from the first inlet refrigerant temperature TIA. The first value Q1 is, for example, around several degrees Celsius.

[0178] Alternatively, when the refrigerant temperature TEA at the first outlet EA of the first indoor heat exchanger 64A rises over time, the controller 130 switches the first indoor expansion valve 63A from the second state J2 to the first state J1. For example, one could consider a scenario where the first outlet refrigerant temperature TEA rises by several degrees Celsius over a period of time ranging from several seconds to several minutes.

[0179] Alternatively, if the duration of the second state J2 is greater than the second value Q2, the controller 130 switches the first indoor expansion valve 63A from the second state J2 to the first state J1. The second value Q2 is, for example, approximately several seconds to several minutes.

[0180] Alternatively, the controller 130 may switch the first chamber expansion valve 63A from the second state J2 to the first state J1 when the reservoir pressure Pd of the gas-liquid separator 25, as measured by the reservoir pressure sensor 105, rises above a threshold, or when the reservoir pressure Pd of the gas-liquid separator 25, as measured by the reservoir pressure sensor 105, rises over time (e.g., by several Pa over a period of time from several seconds to several minutes).

[0181] When liquid refrigerant accumulates in the first indoor heat exchanger 64A, the controller 130 switches the first indoor expansion valve 63A from the first state J1 to the second state J2.

[0182] Specifically, when the refrigerant temperature TIA at the first inlet IA of the first indoor heat exchanger 64A is less than the critical temperature Tc at the critical point C of the refrigerant, the controller 130 switches the first indoor expansion valve 63A from the first state J1 to the second state J2.

[0183] Alternatively, when the difference between the first inlet refrigerant temperature TIA at the first inlet IA of the first indoor heat exchanger 64A and the first outlet refrigerant temperature TEA at the first outlet EA of the first indoor heat exchanger 64A is less than a third value Q3, the controller 130 switches the first indoor expansion valve 63A from the first state J1 to the second state J2. This difference is obtained by subtracting the first outlet refrigerant temperature TEA from the first inlet refrigerant temperature TIA. The third value Q3 is, for example, around several degrees Celsius.

[0184] Alternatively, when the difference between the first inlet refrigerant temperature TIA at the first inlet IA of the first indoor heat exchanger 64A and the first indoor temperature TRA of the first indoor space RA (first utilized side space) involved by the first air conditioning unit 60A (first utilized unit) is less than the fourth value Q4, the controller 130 switches the first indoor expansion valve 63A from the first state J1 to the second state J2. This difference is obtained by subtracting the first indoor temperature TRA from the first inlet refrigerant temperature TIA. The fourth value Q4 is, for example, around several degrees Celsius.

[0185] Alternatively, if the duration of the first state J1 is greater than the fifth value Q5, the controller 130 switches the first indoor expansion valve 63A from the first state J1 to the second state J2. The fifth value Q5 is, for example, approximately several seconds to several minutes.

[0186] (11) Start-up of heating operation

[0187] The start-up of the heating operation of air conditioning unit 1 will be explained. It should be noted that only the start-up of the heating operation of the first air conditioning unit 60A will be explained, and the start-up of the heating operation of the second air conditioning unit 60B will be omitted.

[0188] The controller 130 executes start-up mode M3 for the first air conditioning unit 60A. In start-up mode M3, the controller 130 starts heating operation while the first indoor fan 62A in the first air conditioning unit 60A is stopped. In start-up mode M3, after the heating operation is started, when the first outlet refrigerant temperature TEA at the first outlet EA of the first indoor heat exchanger 64A is greater than the critical temperature Tc at the critical point C of the refrigerant, the controller 130 drives the first indoor fan 62A.

[0189] In start-up mode M3, the controller 130 opens the exhaust valve 42 of the exhaust pipe 41 when heating operation is started. It should be noted that "opening the exhaust valve 42" includes not only opening the exhaust valve 42 with a new opening degree of zero, but also further increasing the opening degree of the already opened exhaust valve 42.

[0190] The same applies when starting the second air conditioning unit 60B.

[0191] (12) Control process

[0192] Figure 6 This is the control flowchart of the first air conditioning unit 60A. Starting from the beginning, in the first step S1, according to the heating operation start command issued by the user to the controller 130, the first air conditioning unit 60A starts the start mode M3.

[0193] In the second step S2, the controller 130 starts heating operation while the first indoor fan 62A in the first air conditioning unit 60A is stopped. Specifically, the controller 130 operates the second compressor 22 and the third compressor 23. The controller 130 opens the first indoor expansion valve 63A. At this time, the first indoor expansion valve 63A is, for example, fully open (100%). At this time, the first indoor fan 62A remains stopped. At this time, the exhaust valve 42 of the exhaust pipe 41 remains closed.

[0194] In the third step S3, the controller 130 determines whether the first outlet refrigerant temperature TEA at the first outlet EA of the first indoor heat exchanger 64A is greater than the critical temperature Tc at the critical point C of the refrigerant. If it is determined that the first outlet refrigerant temperature TEA is greater than the critical temperature Tc, the process proceeds to the fourth step S4. Otherwise, it returns to the second step S2.

[0195] In the fourth step S4, the controller 130 opens the exhaust valve 42 of the exhaust pipe 41.

[0196] In the fifth step S5, the first air conditioning unit 60A is switched to operating mode M2.

[0197] In the sixth step S6, according to the stop command (temperature control shutdown command) sent from the user to the controller 130, the first air conditioning unit 60A starts the stop mode M1 (temperature control shutdown mode).

[0198] In the seventh step S7, the first indoor expansion valve 63A is brought to the second state J2. Specifically, the opening degree of the first indoor expansion valve 63A is reduced to, for example, a few percent.

[0199] In the eighth step S8, the controller 130 determines whether the liquid reservoir pressure Pd of the gas-liquid separator 25 has increased. Specifically, the controller 130 determines whether any of the following conditions are met: the difference between the first inlet refrigerant temperature TIA and the first outlet refrigerant temperature TEA is greater than a first value Q1; the first outlet refrigerant temperature TEA increases over time; and the duration of the second state J2 is greater than a second value Q2.

[0200] Alternatively, the controller 130 may determine whether any of the following conditions are met: the liquid reservoir pressure Pd of the gas-liquid separator 25 rises and exceeds a threshold; and the liquid reservoir pressure Pd of the gas-liquid separator 25 rises over time.

[0201] If the above conditions are met, proceed to step nine, S9. If the above conditions are not met, return to step seven, S7.

[0202] In the ninth step S9, the first indoor expansion valve 63A is set to the first state J1. Specifically, the opening degree of the first indoor expansion valve 63A is set to fully closed (0%).

[0203] In the tenth step S10, the controller 130 determines whether liquid refrigerant has accumulated in the first indoor heat exchanger 64A.

[0204] Specifically, the controller 130 determines whether any of the following conditions are met: the first inlet refrigerant temperature TIA is less than the critical temperature Tc; the difference between the first inlet refrigerant temperature TIA and the first outlet refrigerant temperature TEA is less than the third value Q3; the difference between the first inlet refrigerant temperature TIA and the first indoor temperature TRA is less than the fourth value Q4; and the duration of the first state J1 is greater than the fifth value Q5.

[0205] If the above conditions are met, return to step 7 (S7). If the above conditions are not met, proceed to step 11 (S11).

[0206] In step eleven, S11, it is determined whether there is an operation termination command from the user. If there is an operation termination command, proceed to step twelfth, S12. If there is no operation termination command, return to step seven, S7.

[0207] In step S12, controller 130 causes the first air conditioning unit 60A to stop operating. Then, the "end" step is reached.

[0208] In stop mode M1, the seventh step S7 (second state J2) and the ninth step S9 (first state J1) are repeated.

[0209] It should be noted that the controller 130 can also return to step S5 based on the operating mode transfer command from the user.

[0210] The controller 130 can perform each operation automatically, without relying on each instruction from the user.

[0211] (Function and effect)

[0212] According to this embodiment, in a multi-split air conditioning unit 1 that operates in supercritical mode, the first air conditioning unit 60A in the first air conditioning unit 60A and the second air conditioning unit 60B can be stopped.

[0213] By switching the first indoor expansion valve 63A of the first air conditioning unit 60A from the second state J2 to the first state J1, throttling control is applied to the first indoor expansion valve 63A of the first air conditioning unit 60A, thereby suppressing the rise in refrigerant pressure downstream of the indoor heat exchanger 64 of the air conditioning unit 60. In particular, the rise in liquid receiver pressure Pd of the gas-liquid separator 25 located downstream of the indoor heat exchanger 64 of the air conditioning unit 60 can be suppressed.

[0214] In addition, by switching the first indoor expansion valve 63A of the first air conditioning unit 60A from the first state J1 to the second state J2, the first indoor expansion valve 63A of the first air conditioning unit 60A is opened, thereby preventing the accumulation of liquid refrigerant in the first indoor heat exchanger 64A of the first air conditioning unit 60A.

[0215] When the liquid storage pressure Pd of the gas-liquid separator 25 located downstream of the indoor heat exchanger 64 of the air conditioning unit 60 rises, the first indoor expansion valve 63A of the first air conditioning unit 60A is switched from the second state J2 to the first state J1 to throttle the first indoor expansion valve 63A of the first air conditioning unit 60A, thereby suppressing the rise of the liquid storage pressure Pd of the gas-liquid separator 25.

[0216] Even without directly measuring the liquid storage pressure Pd of the gas-liquid separator 25, the first indoor expansion valve 63A of the first air conditioning unit 60A can be switched from the second state J2 to the first state J1 when the liquid storage pressure Pd of the gas-liquid separator 25 rises.

[0217] With the second air conditioning unit 60B in operation, the first air conditioning unit 60A can be stopped.

[0218] In the first air conditioning unit 60A, the first indoor fan 62A is not driven until the first outlet refrigerant temperature TEA at the first outlet EA of the first indoor heat exchanger 64A becomes greater than the critical temperature Tc at the critical point C of the refrigerant. This prevents the high pressure Ph generated by the compressor 20 from becoming too high immediately after the heating operation starts.

[0219] By promoting the flow of gaseous refrigerant from the gas storage section 25a of the gas-liquid separator 25 into the suction side 20i of the compressor 20 during the start-up of heating operation, the rate of increase of the high pressure Ph generated by the compressor 20 can be improved.

[0220] From an environmental protection perspective, using carbon dioxide as a refrigerant is beneficial.

[0221] <Second Implementation>

[0222] The air conditioning device 1 according to the second embodiment will now be described. In the following description, the same symbols are used to denote the same structure as in the above embodiment, and detailed descriptions are omitted. Figure 7 This is a piping system diagram showing the situation in the second embodiment where the first air conditioning unit 60A is in stop mode M1 and the second air conditioning unit 60B is in operation mode M2.

[0223] In the first state J1, the first chamber expansion valve 63A is not completely closed, but rather opened with a small opening. However, the small opening of the first chamber expansion valve 63A in the first state J1 is smaller than the opening of the first chamber expansion valve 63A in the second state J2. In other words, the opening of the first chamber expansion valve 63A in the second state J2 is larger than the small opening of the first chamber expansion valve 63A in the first state J1. In the second state J2, the first chamber expansion valve 63A is opened to a greater extent than in the first state J1. The small opening of the first chamber expansion valve 63A in the first state J1 is, for example, less than a few percent.

[0224] The other structures are the same as in the first embodiment. According to this embodiment, the same effects as in the first embodiment can be obtained.

[0225] <Other Implementation Methods>

[0226] The compressor can also be a single unit (single-stage).

[0227] There can be three or more indoor heat exchangers 64 that act as radiators.

[0228] The air conditioning unit 1 can also be configured to omit the cooling equipment unit 70.

[0229] The refrigerant does not have to be carbon dioxide.

[0230] Cooling equipment unit 70 may also be used as all or part of the first and second utilization units.

[0231] The embodiments and variations have been described above, but it should be understood that various changes can be made to their form and specific details without departing from the spirit and scope of the claims. Furthermore, elements of the above embodiments, variations, and other embodiments can be appropriately combined or substituted.

[0232] The terms “first,” “second,” “third,” etc., mentioned above are only used to distinguish statements containing these terms and do not limit the number or order of the statements.

[0233] - Symbol Explanation -

[0234] 1. Air conditioning unit

[0235] 6 refrigerant circuit

[0236] 20 compressors

[0237] 20i Inhalation Side

[0238] 24 Outdoor heat exchanger (evaporator)

[0239] 25 gas-liquid separator

[0240] 25a Gas Storage Section

[0241] 41. Exhaust pipe (exhaust passage)

[0242] 42. Exhaust valve (on / off valve)

[0243] 60A First Air Conditioning Unit (First Utilization Unit)

[0244] 60B Second Air Conditioning Unit (Second Utilization Unit)

[0245] 62A First Indoor Fan (Fan)

[0246] 63 Indoor expansion valve (expansion valve)

[0247] 63A First Indoor Expansion Valve (First Expansion Valve)

[0248] 63B Second Indoor Expansion Valve (Second Expansion Valve)

[0249] 64 Indoor heat exchanger (radiator)

[0250] 64A First Indoor Heat Exchanger (First Radiator)

[0251] 64B Second Indoor Heat Exchanger (Second Radiator)

[0252] 130 control device

[0253] C critical point

[0254] Pc critical pressure

[0255] Tc critical temperature (temperature)

[0256] R Interior space (utilizing side space)

[0257] RA First Interior Space (Utilizing Side Space)

[0258] Pd reservoir pressure (pressure)

[0259] IA first entrance (entrance)

[0260] TIA First Inlet Refrigerant Temperature (Temperature)

[0261] EA's first export (export)

[0262] TEA first outlet refrigerant temperature (temperature)

[0263] Q1 First Value

[0264] Q2 second value

[0265] Q3 Third Value

[0266] Q4 Fourth Value

[0267] Q5 Fifth Value

[0268] M1 Stop Mode

[0269] M2 operating mode

[0270] J1 First State

[0271] J2 second state

Claims

1. An air conditioning device, characterized in that: The air conditioning unit includes a refrigerant circuit (6) and a control device (130). The refrigerant circuit (6) includes a compressor (20), a radiator (64), an expansion valve (63), and an evaporator (24), and performs a refrigeration cycle for heating operation by compressing the refrigerant to a critical pressure (Pc) or higher, in which heating is performed using the side space (R). The control device (130) controls the refrigerant circuit (6). The radiator (64) includes a first radiator (64A) and a second radiator (64B) connected in parallel with each other. The expansion valve (63) includes a first expansion valve (63A) corresponding to the first radiator (64A) and a second expansion valve (63B) corresponding to the second radiator (64B). The first radiator (64A) and the first expansion valve (63A) constitute the first utilization unit (60A). The second radiator (64B) and the second expansion valve (63B) constitute the second utilization unit (60B). When the first utilization unit (60A) is in the stop mode (M1), the control device (130) controls the first expansion valve (63A) to switch between a first state (J1) and a second state (J2). In the first state (J1), the first expansion valve (63A) is completely closed or opened with a small opening. In the second state (J2), the first expansion valve (63A) is opened more than in the first state (J1).

2. The air conditioning device according to claim 1, characterized in that: The refrigerant circuit (6) has a gas-liquid separator (25) connected to the downstream side of the radiator (64), and the gas-liquid separator (25) separates the refrigerant into gaseous refrigerant and liquid refrigerant. The control device (130) switches the first expansion valve (63A) from the second state (J2) to the first state (J1) according to the pressure (Pd) of the gas-liquid separator (25).

3. The air conditioning device according to claim 2, characterized in that: When the difference between the temperature (TIA) of the refrigerant at the inlet (IA) of the first radiator (64A) and the temperature (TEA) of the refrigerant at the outlet (EA) of the first radiator (64A) is greater than a first value (Q1), or when the temperature (TEA) of the refrigerant at the outlet (EA) of the first radiator (64A) rises over time, the control device (130) switches the first expansion valve (63A) from the second state (J2) to the first state (J1).

4. The air conditioning device according to claim 2, characterized in that: When the duration of the second state (J2) is greater than the second value (Q2), the control device (130) switches the first expansion valve (63A) from the second state (J2) to the first state (J1).

5. The air conditioning device according to any one of claims 1 to 4, characterized in that: When the temperature (TIA) of the refrigerant at the inlet (IA) of the first radiator (64A) is less than the temperature (Tc) at the critical point (C) of the refrigerant; or, when the difference between the temperature (TIA) of the refrigerant at the inlet (IA) of the first radiator (64A) and the temperature (TEA) of the refrigerant at the outlet (EA) of the first radiator (64A) is less than a third value (Q3); or, when the difference between the temperature (TIA) of the refrigerant at the inlet (IA) of the first radiator (64A) and the temperature (TRA) of the utilization side space (RA) involved in the first utilization unit (60A) is less than a fourth value (Q4); or, when the duration of the first state (J1) is greater than a fifth value (Q5), the control device (130) switches the first expansion valve (63A) from the first state (J1) to the second state (J2).

6. The air conditioning device according to any one of claims 1 to 5, characterized in that: When the first utilization unit (60A) is in stop mode (M1) and the second utilization unit (60B) is in operation mode (M2), the control device (130) causes the opening of the first expansion valve (63A) to be less than the opening of the second expansion valve (63B).

7. The air conditioning device according to any one of claims 1 to 6, characterized in that: The control device (130) starts heating operation while the fan (62A) in the first utilization unit (60A) is stopped. After the heating operation is started, when the temperature (TEA) of the refrigerant at the outlet (EA) of the first radiator (64A) is greater than the temperature (Tc) at the critical point (C) of the refrigerant, the control device (130) drives the fan (62A).

8. The air conditioning device according to claim 7, characterized in that: The refrigerant circuit (6) has a gas-liquid separator (25), an exhaust passage (41), and a switching valve (42). The gas-liquid separator (25) is connected to the downstream side of the radiator (64), and the gas-liquid separator (25) separates the refrigerant into gaseous refrigerant and liquid refrigerant. The exhaust passage (41) connects the gas storage section (25a) of the gas-liquid separator (25) to the suction side (20i) of the compressor (20). The switching valve (42) is located on the exhaust passage (41). The control device (130) opens the switch valve (42) when the heating operation is started.

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