Air conditioning system

Abstract

To stop some of utilization units in a multi-type air conditioning apparatus that performs supercritical operation.SOLUTION: An air conditioning apparatus comprises: a refrigerant circuit that has a compressor, a radiator, an expansion valve, and an evaporator, and performs a refrigeration cycle for executing heating operation for heating a utilization-side space by compressing a refrigerant to a critical pressure or higher; and a control device for controlling the refrigerant circuit. The radiator includes a first radiator and a second radiator, which are connected in parallel to each other. The expansion valve includes a first expansion valve corresponding to a first radiator and a second expansion valve corresponding to a second radiator. 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. When the first utilization unit is in a stop mode, the control device controls the first expansion valve to switch between a first state in which the first expansion valve is fully closed or is opened with a very small opening degree, and a second state in which the first expansion valve is opened more than when the first expansion valve is in the first state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an air conditioner.

Background Art

[0002] For example, as disclosed in Patent Document 1, various technologies for air conditioners are disclosed. The air conditioner 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 a room. In the air conditioner disclosed in Patent Document 1, a supercritical operation of compressing the refrigerant to a pressure equal to or higher than the critical pressure is performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a multi-type air conditioner in which a plurality of user units are connected to one heat source unit, some of the plurality of user units may be stopped. At this time, usually, the expansion valve of the user unit to be stopped is throttled with the valve slightly open.

[0005] In a multi-type air conditioner that performs supercritical operation, when some of the plurality of user units are stopped by the above method, there is a problem that the pressure of the refrigerant rises on the downstream side of the radiator of the user unit. At the same time, it is necessary to suppress the accumulation of liquid refrigerant in the radiator of the user unit to be stopped.

[0006] Due to such events, it has been difficult to stop some of the plurality of user units in a multi-type air conditioner that performs supercritical operation.

[0007] The purpose of this disclosure is to enable the shutdown of some of the multiple utilization units in a multi-type air conditioning system that performs supercritical operation. [Means for solving the problem]

[0008] A first aspect of this disclosure relates to an air conditioning system (1). The air conditioning system (1) includes a compressor (20), a radiator (64), an expansion valve (63), and an evaporator (24), and a refrigerant circuit (6) that performs a refrigeration cycle for performing a heating operation that heats the user-side space (R) by compressing the refrigerant to a critical pressure (Pc) or higher, and a control device (130) that controls the refrigerant circuit (6). The radiator (64) includes a first radiator (64A) and a second radiator (64B) connected in parallel to each other, and the expansion valve (63) includes a first expansion valve (63A) corresponding to the first radiator (64A) and a second expansion valve (63A) corresponding to the second radiator (64B). B) includes, wherein the first heat sink (64A) and the first expansion valve (63A) constitute a first utilization unit (60A), and the second heat sink (64B) and the second expansion valve (63B) constitute a second utilization unit (60B), and the control device (130) controls the first expansion valve (63A) to switch between a first state (J1) in which the first expansion valve (63A) is fully closed or opened to a small degree, and a second state (J2) in which the first expansion valve (63A) is opened more than in the first state (J1), when the first utilization unit (60A) is in stop mode (M1).

[0009] According to the first embodiment, in a multi-type air conditioning system (1) that performs supercritical operation, it becomes possible to stop the first utilization unit (60A) of the two utilization units (60B) (60A and 60A).

[0010] A second aspect of the present disclosure relates to the air conditioning system (1) of the first aspect. The refrigerant circuit (6) is connected downstream of the radiator (64) and includes a gas-liquid separator (25) that separates the refrigerant into gaseous and liquid refrigerants, and 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).

[0011] According to the second embodiment, when the pressure (Pd) of the gas-liquid separator (25) located downstream of the heat sink (64) rises, the rise in 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).

[0012] A third aspect of this disclosure relates to the air conditioning system (1) of the second aspect. The control device (130) switches the first expansion valve (63A) from the second state (J2) to the first state (J1) when the difference between the temperature of the refrigerant (TIA) at the inlet (IA) of the first radiator (64A) and the temperature of the refrigerant (TEA) at the outlet (EA) of the first radiator (64A) is greater than a first value (Q1), or when the temperature of the refrigerant (TEA) at the outlet (EA) of the first radiator (64A) rises over time.

[0013] According to the third embodiment, 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.

[0014] A fourth aspect of this disclosure relates to the air conditioning system (1) of the second aspect. The control device (130) switches the first expansion valve (63A) from the second aspect (J2) to the first aspect (J1) when the duration of the second aspect (J2) is greater than the second value (Q2).

[0015] According to the fourth embodiment, 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.

[0016] A fifth aspect of this disclosure relates to an air conditioning system (1) according to any one of the first to fourth aspects. The control device (130) switches the first expansion valve (63A) from the first state (J1) to the second state (J2) when the temperature (TIA) of the refrigerant at the inlet (IA) of the first heat sink (64A) is less than the temperature (Tc) of the refrigerant at the critical point (C), or when the difference between the temperature (TIA) of the refrigerant at the inlet (IA) of the first heat sink (64A) and the temperature (TEA) of the refrigerant at the outlet (EA) of the first heat sink (64A) is less than the third value (Q3), or when the difference between the temperature (TIA) of the refrigerant at the inlet (IA) of the first heat sink (64A) and the temperature (TRA) of the utilization-side space (RA) related to the first utilization unit (60A) is less than the fourth value (Q4), or when the duration of the first state (J1) is greater than the fifth value (Q5).

[0017] According to the fifth embodiment, by switching the first expansion valve (63A) of the first utilization unit (60A) from the first state (J1) to the second state (J2) and opening the first expansion valve (63A) of the first utilization unit (60A), the accumulation of liquid refrigerant in the first heat sink (64A) of the first utilization unit (60A) can be suppressed.

[0018] A sixth aspect of the present disclosure relates to an air conditioning system (1) according to any one of the first to fifth aspects. The control device (130) makes the opening of the first expansion valve (63A) smaller than the opening of the second expansion valve (63B) when the first utilization unit (60A) is in stop mode (M1) and the second utilization unit (60B) is in operation mode (M2).

[0019] According to the sixth aspect, the first usage unit (60A) can be stopped while the second usage unit (60B) is operating.

[0020] The seventh aspect of the present disclosure is directed to the air conditioner (1) according to any one of the first to sixth aspects. The control device (130) starts the heating operation with the fan (62A) in the first usage unit (60A) stopped, and after starting the heating operation, when the temperature (TEA) of the refrigerant at the outlet (EA) of the first radiator (64A) becomes higher than the temperature (Tc) at the critical point (C) of the refrigerant, the control device (130) drives the fan (62A).

[0021] According to the seventh aspect, it is possible to suppress excessive increase in the pressure by the compressor (20) immediately after starting the heating operation.

[0022] The eighth aspect of the present disclosure is directed to the air conditioner (1) according to the seventh aspect. The refrigerant circuit (6) has a gas-liquid separator (25) connected to the downstream side of the radiator (64) and separating the refrigerant into a gas refrigerant and a liquid refrigerant, a gas vent passage (41) connecting the gas storage portion (25a) of the gas-liquid separator (25) and the suction side (20i) of the compressor (20), and an on-off valve (42) provided in the gas vent passage (41), and the control device (130) opens the on-off valve (42) at the start of the heating operation.

[0023] According to the eighth aspect, at the start of the heating operation, by promoting the inflow of the gas refrigerant from the gas storage portion (25a) of the gas-liquid separator (25) to the suction side (20i) of the compressor (20), it is possible to increase the rate of increase in the pressure by the compressor (20).

Brief Description of the Drawings

[0024] [Figure 1] FIG. 1 is a piping system diagram of the air conditioner (1) according to the first embodiment. [Figure 2] FIG. 2 is a piping system diagram near the air conditioning unit (60) according to the first embodiment. [Figure 3]FIG. 3 is a block diagram showing the connection relationship between the controller (130) according to the first embodiment and peripheral devices. [Figure 4] FIG. 4 is a graph showing the relationship between the specific enthalpy (h) and pressure (P) in the refrigerant according to the first embodiment. [Figure 5] FIG. 6 is a piping system diagram when the first air conditioning unit (60A) according to the first embodiment is in the stop mode (M1) and the second air conditioning unit (60B) is in the operation mode (M2). [Figure 6] FIG. 9 is a control flowchart of the first air conditioning unit (60A) according to the first embodiment. [Figure 7] FIG. 7 is a piping system diagram when the first air conditioning unit (60A) according to the second embodiment is in the stop mode (M1) and the second air conditioning unit (60B) is in the operation mode (M2).

Mode for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below, and various modifications can be made without departing from the technical idea of the present disclosure. Since each drawing is for conceptually explaining the present disclosure, dimensions, ratios, or numbers may be exaggerated or simplified as necessary for easy understanding.

[0026] <First Embodiment> The air conditioner (1) according to the first embodiment will be described. The air conditioner (1) performs a refrigeration cycle. The air conditioner (1) is also referred to as a refrigeration device. The air conditioner (1) performs air conditioning in a room. The air conditioner (1) cools a cooling target. Here, the cooling target includes the air inside equipment such as a refrigerator, a freezer, and a showcase. Hereinafter, such equipment is referred to as a cold facility. The air conditioner (1) is of a multi-type in which a plurality of utilization units (the first air conditioning unit (60A), the second air conditioning unit (60B), and the cold facility unit (70)) are connected to one heat source unit (10).

[0027] (1) Overall structure Figure 1 is a piping diagram of the air conditioning system (1). As shown in Figure 1, the air conditioning system (1) includes a heat source unit (10) installed outdoors, an air conditioning unit (60) for air conditioning the interior of the room, and a refrigeration unit (70) for cooling the air inside the room. The air conditioning unit (60) includes a first air conditioning unit (60A) and a second air conditioning unit (60B) connected in parallel to each other.

[0028] The air conditioning system (1) includes four connecting pipes (2, 3, 4, 5) that connect the heat source unit (10), the air conditioning unit (60), and the refrigeration unit (70). In the air conditioning system (1), the heat source unit (10), the air conditioning unit (60), and the refrigeration unit (70) are connected by these connecting pipes (2, 3, 4, 5) to form a refrigerant circuit (6). In other words, the air conditioning system (1) includes a refrigerant circuit (6).

[0029] The refrigerant circuit (6) contains a filled refrigerant. The refrigerant circuit (6) circulates the refrigerant to perform a refrigeration cycle. In this embodiment, the refrigerant is carbon dioxide. The refrigerant circuit (6) performs a refrigeration cycle in which the refrigerant is compressed to a pressure above critical pressure.

[0030] (1-1) Connecting piping The four connecting pipes (2, 3, 4, 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 refrigeration unit (70).

[0031] (2) Heat source unit The heat source unit (10) includes a heat source circuit (11) and an outdoor fan (12). The heat source circuit (11) includes a compressor (20), an outdoor heat exchanger (24), and a gas-liquid separator (25). The heat source circuit (11) includes a first outdoor expansion valve (26) and a second outdoor expansion valve (27). The heat source circuit (11) further includes a supercooling heat exchanger (28) and an intermediate cooler (29).

[0032] The heat source circuit (11) has four shut-off valves (13, 14, 15, 16). The four shut-off valves (13, 14, 15, 16) consist 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).

[0033] The first gas shut-off valve (13) is connected to the first gas connecting pipe (3). The first liquid shut-off valve (14) is connected to the first liquid connecting pipe (2). The second gas shut-off valve (15) is connected to the second gas connecting pipe (5). The second liquid shut-off valve (16) is connected to the second liquid connecting pipe (4).

[0034] The heat source unit (10) has a flow path switching mechanism (30). In the piping diagram of the refrigerant circuit (6), such as in Figure 1, the details of the flow path switching mechanism (30) are omitted. The flow path switching mechanism (30) switches the flow path of the refrigerant in the refrigerant circuit (6).

[0035] (2-1) Compressor The compressor (20) compresses the refrigerant. The compressor (20) has a first compressor (21), a second compressor (22), and a third compressor (23). The compressor (20) performs single-stage compression of the refrigerant and two-stage compression of the refrigerant.

[0036] The first compressor (21) is a refrigeration compressor corresponding to the refrigeration 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-stage compressors. The first compressor (21) and the second compressor (22) are connected in parallel.

[0037] The third compressor (23) is a high-stage compressor. The third compressor (23) is connected in series with the first compressor (21) or in series with the second compressor (22).

[0038] The first compressor (21), the second compressor (22), and the third compressor (23) are rotary compressors whose compression mechanism is driven by a motor. The first compressor (21), the second compressor (22), and the third compressor (23) are of variable displacement type. The rotational speed of the motors of the first compressor (21), the second compressor (22), and the third compressor (23) is adjusted by an inverter device. In other words, the first compressor (21), the second compressor (22), and the third compressor (23) are configured to have adjustable operating capacities.

[0039] The first suction pipe (21a) is connected to the suction section of the first compressor (21). The first discharge pipe (21b) is connected to the discharge section of the first compressor (21). The second suction pipe (22a) is connected to the suction section of the second compressor (22). The second discharge pipe (22b) is connected to the discharge section of the second compressor (22). The third suction pipe (23a) is connected to the suction section of the third compressor (23). The third discharge pipe (23b) is connected to the discharge section of the third compressor (23).

[0040] (2-2) Intermediate channel The heat source circuit (11) includes an intermediate flow path (18). The intermediate flow path (18) connects the discharge section of the first compressor (21) and the discharge section of the second compressor (22) to the suction section of the third compressor (23). The intermediate flow path (18) includes a first discharge pipe (21b), a second discharge pipe (22b), and a third suction pipe (23a).

[0041] (2-3) Outdoor heat exchanger and outdoor fan The outdoor heat exchanger (24) is an example of an evaporator. The outdoor heat exchanger (24) is a fin-and-tube type air heat exchanger. The outdoor fan (12) is positioned near the outdoor heat exchanger (24). The outdoor fan (12) transports outdoor air. The outdoor heat exchanger exchanges heat between the refrigerant flowing inside it and the outdoor air transported by the outdoor fan (12).

[0042] (2-4) Liquid side flow path The heat source circuit (11) includes a liquid-side flow path (40). The liquid-side flow path (40) is provided between the liquid-side end of the outdoor heat exchanger (24) and two liquid shut-off valves (14, 16). The liquid-side flow path (40) includes pipes 1 through 5 (40a, 40b, 40c, 40d, 40e).

[0043] One end of the first pipe (40a) is connected to the liquid side end 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 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 between the first outdoor expansion valve (26) and the gas-liquid separator (25) in the first pipe (40a). The other end of the fourth pipe (40d) is connected to the middle of the third pipe (40c). One end of the fifth pipe (40e) is connected between the outdoor heat exchanger (24) and the first outdoor expansion valve (26) in the first pipe (40a). The other end of the fifth pipe (40e) is connected between the gas-liquid separator (25) in the second pipe (40b) and the connection point of the third pipe (40c).

[0044] (2-5) Outdoor expansion valve The first outdoor expansion valve (26) is installed in the first pipe (40a). The first outdoor expansion valve (26) is installed in the first pipe (40a) between the liquid side end of the outdoor heat exchanger (24) and the connection to the fourth pipe (40d). The second outdoor expansion valve (27) is installed in the fifth pipe (40e). The first outdoor expansion valve (26) and the second outdoor expansion valve (27) are expansion valves whose opening degree can be adjusted. The first outdoor expansion valve (26) and the second outdoor expansion valve (27) are electronic expansion valves whose opening degree is adjusted based on a pulse signal.

[0045] (2-6) Gas-liquid separator The gas-liquid separator (25) is also called a receiver. The gas-liquid separator (25) is a sealed container for storing refrigerant. The gas-liquid separator (25) separates the refrigerant into gaseous refrigerant and liquid refrigerant. Inside the gas-liquid separator (25), a gas storage section (25a) and a liquid storage section (25b) are formed. 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).

[0046] (2-7) Gas venting pipe The heat source circuit (11) has a vent pipe (41). The vent pipe (41) is an example of a vent passage. One end of the vent pipe (41) is connected to the gas storage section (25a) at the top of the gas-liquid separator (25). The other end of the vent pipe (41) is connected to the intermediate passage (18). The vent pipe (41) sends the gas refrigerant gas in the gas-liquid separator (25) to the intermediate passage (18). The vent 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-stage compressor.

[0047] A gas venting valve (42) is provided in the gas venting pipe (41). The gas venting valve (42) is an example of an on / off valve. The gas venting valve (42) is an expansion valve whose opening degree can be adjusted. The gas venting valve (42) is an electronic expansion valve whose opening degree is adjusted based on a pulse signal. The gas venting valve (42) may also be an electric valve or an electromagnetic on / off valve.

[0048] (2-8) Supercooling heat exchanger The supercooled heat exchanger (28) has a first flow path (28a) which is a high-pressure side flow path and a second flow path (28b) which is a low-pressure side flow path. The supercooled heat exchanger (28) exchanges heat between the refrigerant in the first flow path (28a) and the refrigerant in the second flow path (28b). In other words, the supercooled heat exchanger (28) cools the refrigerant flowing through the first flow path (28a) with the refrigerant flowing through the second flow path (28b).

[0049] The second channel (28b) constitutes part of the injection channel (43). The injection channel (43) includes an upstream channel (44) and a downstream channel (45).

[0050] One end of the upstream channel (44) is connected upstream of the connection point of the fourth pipe (40d) in the third pipe (40c). The other end of the upstream channel (44) is connected to the inlet end of the second channel (28b). The upstream channel (44) is provided with an injection valve (46), which is a supercooling side pressure reducing valve. The injection valve (46) is an expansion valve whose opening degree is adjustable. The injection valve (46) is an electronic expansion valve whose opening degree is adjusted based on a pulse signal.

[0051] One end of the downstream channel (45) is connected to the outflow end of the second channel (28b). The other end of the downstream channel (45) is connected to the intermediate channel (18).

[0052] (2-9) Intercooler The intercooler (29) is installed in the intermediate flow path (18). The intercooler (29) is a fin-and-tube type air heat exchanger. A cooling fan (29a) is placed near the intercooler (29). The intercooler (29) exchanges heat between the refrigerant flowing inside it and the outside air transported by the cooling fan (29a).

[0053] (2-10) Oil separation circuit The heat source circuit (11) includes an oil separation circuit. The oil separation circuit has an oil separator (50), a first oil return pipe (51), and a second oil return pipe (52).

[0054] The oil separator (50) is connected to the third discharge pipe (23b). The oil separator (50) separates oil from the refrigerant discharged from the compressor (20). The inlet ends of the first oil return pipe (51) and the second oil return pipe (52) are in communication with the oil separator (50). The outlet end of the first oil return pipe (51) is connected to the intermediate flow path (18). The first oil return pipe (51) is provided with a first oil volume control valve (53).

[0055] The outlet side of the second oil return pipe (52) is separated into a first branch pipe (52a) and a second branch pipe (52b). The first branch pipe (52a) is connected to the oil reservoir of the first compressor (21). The second branch pipe (52b) is connected to the oil reservoir of the second compressor (22). The first branch pipe (52a) is equipped with a second oil volume control valve (54). The second branch pipe (52b) is equipped with a third oil volume control valve (55).

[0056] (2-11) Bypass pipe The heat source circuit (11) includes 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).

[0057] Specifically, the first bypass pipe (56) directly connects the first inhalation pipe (21a) and the first discharge pipe (21b). The second bypass pipe (57) directly connects the second inhalation pipe (22a) and the second discharge pipe (22b). The third bypass pipe (58) directly connects the third inhalation pipe (23a) and the third discharge pipe (23b).

[0058] (2-12) Check valve The heat source circuit (11) has a plurality of check valves. The plurality of check valves include check valves 1 to 12 (CV1 to CV12). These check valves (CV1 to CV12) allow the flow of refrigerant in the direction of the arrows in Figure 1 and prohibit the flow of refrigerant in the reverse direction.

[0059] The first check valve (CV1) and the second check valve (CV2) are provided in the flow path switching mechanism (30).

[0060] The third check valve (CV3) is installed in the third discharge pipe (23b). The fourth check valve (CV4) is installed in the first pipe (40a). The fifth check valve (CV5) is installed in the third pipe (40c). The sixth check valve (CV6) is installed in the fourth pipe (40d). The seventh check valve (CV7) is installed in the fifth pipe (40e). The eighth check valve (CV8) is installed in the first bypass pipe (56). The ninth check valve (CV9) is installed in the second bypass pipe (57). The tenth check valve (CV10) is installed in the third bypass pipe (58). The eleventh check valve (CV11) is installed in the first discharge pipe (21b). The twelfth check valve (CV12) is installed in the second discharge pipe (22b).

[0061] (3) Air conditioning unit Figure 2 is a piping diagram near the air conditioning unit (60). The air conditioning unit (60) is a unit installed indoors. The air conditioning unit (60) has an indoor circuit (61) and an indoor fan (62). The first liquid connecting pipe (2) is connected to the liquid side end of the indoor circuit (61). The first gas connecting pipe (3) is connected to the gas side end of the indoor circuit (61). The indoor fan (62) is an example of a fan.

[0062] As shown in Figure 2, the indoor circuit (61) has, in order from the liquid side end to the gas side end, an indoor expansion valve (63) and an indoor heat exchanger (64). The indoor expansion valve (63) is an example of an expansion valve. The indoor expansion valve (63) is an expansion valve whose opening degree can be adjusted. The indoor expansion valve (63) is an electronic expansion valve that adjusts its opening degree based on a pulse signal.

[0063] The indoor heat exchanger (64) is a fin-and-tube type air heat exchanger. The indoor heat exchanger (64) is an example of a heat radiator. The indoor fan (62) is positioned near the indoor heat exchanger (64). The indoor fan (62) transports indoor air. The indoor heat exchanger (64) exchanges heat between the refrigerant flowing inside it and the indoor air transported by the indoor fan (62).

[0064] The air conditioning unit (60) includes a first air conditioning unit (60A) and a second air conditioning unit (60B) connected in parallel to each other. The air conditioning unit (60) is an example of a user unit. The first air conditioning unit (60A) is an example of a first user unit. The second air conditioning unit (60B) is an example of a second user unit. The indoor circuit (61) includes a first indoor circuit (61A) and a second indoor circuit (61B) connected in parallel to each other. 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).

[0065] The indoor heat exchanger (64) includes a first indoor heat exchanger (64A) and a second indoor heat exchanger (64B) connected in parallel to each other. The first indoor heat exchanger (64A) is an example of a first heat radiator. The second indoor heat exchanger (64B) is an example of a second heat radiator.

[0066] The indoor expansion valve (63) is the first indoor expansion valve (63A) corresponding to the first indoor heat exchanger (64A), Includes a second indoor expansion valve (63B) corresponding to the second indoor heat exchanger (64B), and a 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 a first indoor heat exchanger (64A) and a second indoor fan (62B) corresponding to a 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.

[0067] (4) Refrigeration unit The refrigeration unit (70) is a utilization unit for cooling the inside of the storage unit. The refrigeration unit (70) has a refrigeration circuit (71) and a refrigeration fan (72). A second liquid connecting pipe (4) is connected to the liquid side end of the refrigeration circuit (71). A second gas connecting pipe (5) is connected to the gas side end of the refrigeration circuit (71).

[0068] The refrigeration circuit (71) has, in order from the liquid side end to the gas side end, a refrigeration expansion valve (73) and a refrigeration heat exchanger (74). The refrigeration expansion valve (73) is an expansion valve whose opening degree is adjustable. The refrigeration expansion valve (73) is an electronic expansion valve that adjusts its opening degree based on a pulse signal.

[0069] The refrigerated heat exchanger (74) is a fin-and-tube type air heat exchanger. The refrigerated fan (72) is positioned near the refrigerated heat exchanger (74). The refrigerated fan (72) transports the air inside the chamber. The refrigerated heat exchanger (74) exchanges heat between the refrigerant flowing inside it and the air inside the chamber transported by the refrigerated fan (72).

[0070] (5) Flow path switching mechanism The 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) to switch between at least 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 heat radiator and the indoor heat exchanger (64) and the chilled 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 chilled heat exchanger (74) function as heat radiators.

[0071] The flow path switching mechanism (30) has a first port (P1), a second port (P2), a third port (P3), a fourth port (P4), a first switching flow path (31), a second switching flow path (32), a third switching flow path (33), and a fourth switching flow path (34). Each switching flow path (31-34) is provided with an opening / closing mechanism (not shown). Each opening / closing mechanism includes an opening / closing valve and an expansion valve.

[0072] The first port (P1) is connected to the discharge section of the third compressor (23). The second port (P2) is connected to the suction section of the second compressor (22). The third port (P3) is connected to the gas end of the indoor heat exchanger (64). The fourth port (P4) is connected to the gas end of the outdoor heat exchanger (24).

[0073] The first switching channel (31), the second switching channel (32), the third switching channel (33), and the fourth switching channel (34) are connected in a bridge configuration. The first switching channel (31) connects the first port (P1) and the third port (P3). The second switching channel (32) connects the first port (P1) and the fourth port (P4). The third switching channel (33) connects the second port (P2) and the third port (P3). The switching fourth channel (34) connects the second port (P2) and the fourth port (P4).

[0074] A first check valve (CV1) is provided in the fourth switching flow path (34). A second check valve (CV2) is provided in the first switching flow path (31). The first check valve (CV1) allows the flow of refrigerant from the fourth port (P4) to the second port (P2) in the fourth switching flow path (34), and prohibits the flow of refrigerant from the second port (P2) to the fourth port (P4). The second check valve (CV2) allows the flow of refrigerant from the first port (P1) to the third port (P3) in the first switching flow path (31), and prohibits the flow of refrigerant from the third port (P3) to the first port (P1).

[0075] (6) Sensor The air conditioning system (1) has a plurality of sensors. The plurality of 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.

[0076] The refrigerant pressure sensor includes a high-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 sensor (101) is installed in the third discharge pipe (23b). The high-pressure sensor (101) is located in the compressor. The pressure of the refrigerant on the discharge side of (20), in other words, the high pressure (Ph) of the refrigerant circuit (6), is detected.

[0077] An intermediate pressure sensor (102) is installed in the third suction pipe (23a). The intermediate pressure sensor (102) detects the refrigerant pressure between the lower-stage compressor and the higher-stage compressor, in other words, the intermediate pressure of the refrigerant circuit (6). A first suction pressure sensor (103) is installed in 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 in the second suction pipe (22a). The second suction pressure sensor (104) detects the refrigerant pressure on the suction side of the second compressor (22).

[0078] The receiver pressure sensor (105) is installed in the liquid-side flow path (40). Specifically, the receiver pressure sensor (105) is installed in the second pipe (40b). The receiver pressure sensor (105) detects a pressure equivalent to the internal pressure of the gas-liquid separator (25) (receiver pressure (Pd) described later). The receiver pressure sensor (105) detects a pressure equivalent to the refrigerant pressure in the first flow path (28a). The receiver pressure sensor (105) may also be a sensor that detects the refrigerant pressure in the gas-liquid separator (25).

[0079] The refrigerant temperature sensor includes a first discharge temperature sensor (111), a first suction temperature sensor (112), a second discharge temperature sensor (113), a second suction temperature sensor (114), a third discharge 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).

[0080] The first discharge temperature sensor (111) is installed in the first discharge pipe (21b) and detects the temperature of the refrigerant discharged from the first compressor (21). The first intake temperature sensor (112) is installed in the first intake pipe (21a) and detects the temperature of the refrigerant drawn into the first compressor (21). The second discharge temperature sensor (113) is installed in the second discharge pipe (22b) and detects the temperature of the refrigerant discharged from the second compressor (22). The second intake temperature sensor (114) is installed in the second intake pipe (22a) and detects the temperature of the refrigerant drawn into the second compressor (22). The third discharge temperature sensor (115) is installed in the third discharge pipe (23b) and detects the temperature of the refrigerant discharged from the third compressor (23). The third intake temperature sensor (116) is installed in the third intake pipe (23a) and detects the temperature of the refrigerant drawn into the third compressor (23).

[0081] The liquid-side temperature sensor (117) is installed in the liquid-side flow path (40). Specifically, the liquid-side temperature sensor (117) is installed on the outlet side of the first flow path (28a) of the subcooled heat exchanger (28) in the liquid-side flow path (40). The liquid-side temperature sensor (117) detects the temperature of the refrigerant that has flowed out of the first flow path (28a).

[0082] The injection-side temperature sensor (118) is located in the downstream flow path (45) of the injection flow path (43). In other words, the injection-side temperature sensor (118) is located on the outlet 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 that has flowed out of the second flow path (28b).

[0083] 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 installed 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).

[0084] The 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 installed at the gas 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 end of the outdoor heat exchanger (24).

[0085] The indoor heat exchanger liquid-side temperature sensor (121) is installed in the heat transfer tubes of the indoor heat exchanger (64). The indoor heat exchanger liquid-side temperature sensor (121) is installed 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).

[0086] The first indoor heat exchanger liquid-side temperature sensor (121A) corresponds to the first indoor heat exchanger (64A). The first indoor heat exchanger liquid-side temperature sensor (121A) is installed in the heat transfer tube of the first indoor heat exchanger (64A). The first indoor heat exchanger liquid-side temperature sensor (121A) is installed at the liquid-side end of the first indoor heat exchanger (64A). The first indoor heat exchanger liquid-side temperature sensor (121A) detects the temperature of the refrigerant at the liquid-side end of the first indoor heat exchanger (64A).

[0087] The second indoor heat exchanger liquid-side temperature sensor (121B) corresponds to the second indoor heat exchanger (64B). The second indoor heat exchanger liquid-side temperature sensor (121B) is installed in the heat transfer tube of the second indoor heat exchanger (64B). The second indoor heat exchanger liquid-side temperature sensor (121B) is installed at the liquid-side end of the second indoor heat exchanger (64B). The second indoor heat exchanger liquid-side temperature sensor (121B) detects the temperature of the refrigerant at the liquid-side end of the second indoor heat exchanger (64B).

[0088] The indoor heat exchanger gas-side temperature sensor (122) is installed on the heat transfer tubes of the indoor heat exchanger (64). The indoor heat exchanger gas-side temperature sensor (122) is installed 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).

[0089] 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 in the heat transfer tube of the first indoor heat exchanger (64A). The first indoor heat exchanger gas-side temperature sensor (122A) is installed 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).

[0090] 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 in the heat transfer tube of the second indoor heat exchanger (64B). The second indoor heat exchanger gas-side temperature sensor (122B) is installed 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).

[0091] The air temperature sensor includes an outdoor air temperature sensor (123) and an indoor air temperature sensor (124). The outdoor air temperature sensor (123) detects the temperature of the outdoor air.

[0092] The indoor temperature sensor (124) detects the indoor temperature in 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).

[0093] The first indoor temperature sensor (124A) detects the indoor temperature in 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 in the room where the second air conditioning unit (60B) (second indoor heat exchanger (64B)) is installed.

[0094] (7) Controller Figure 3 is a block diagram showing the connection relationship between the controller (130) as a control device and peripheral equipment. The air conditioning system (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 memory device (specifically, semiconductor memory) that stores software for operating the microcomputer.

[0095] As shown in Figure 3, the controller (130) includes an outdoor controller (131), an indoor controller (132), and a cooling controller (133). As shown in Figure 1, 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 controller (133) is installed in the cooling unit (70). The outdoor controller (131) is installed in the indoor controller (132) and the cooling controller It can communicate with (133).

[0096] The indoor controller (132) includes a first indoor controller (132A) and a second indoor controller (132B) connected in parallel to each other. 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).

[0097] The controller (130) receives control commands from the user and detection signals from each sensor. The controller (130) controls each component of the air conditioning system (1). Specifically, the controller (130) turns on the first compressor (21), the second compressor (22), and the third compressor (23). The controller (130) controls the ON / OFF state. The controller (130) adjusts the capacity (more precisely, 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.

[0098] (8) Heating operation (8-1) Operation of the air conditioning system during heating The operation of the air conditioning system (1) will be explained. The operation of the air conditioning system (1) includes cooling operation, cooling operation, cooling and cooling operation, heating operation, heating and cooling operation, and defrost operation. In this example, only heating operation will be explained. In heating operation, the cooling unit (70) stops and the air conditioning unit (60) heats the room. The flow of refrigerant during heating operation is shown by a thick line in Figure 1.

[0099] As shown in Figure 1, during heating operation, the controller (130) controls the on / off valves provided in each switching passage (31-34) to close the second switching passage (32) and the third switching passage (33), and to open the first switching passage (31) and the fourth switching passage (34).

[0100] The controller (130) stops the first compressor (21) and starts the second compressor (22) and the third compressor (23). The controller (130) opens the second outdoor expansion valve (27) and the injection valve (46) to a predetermined opening and closes the first outdoor expansion valve (26). The controller (130) closes the refrigerated expansion valve (73) and opens the indoor expansion valve (63). The controller (130) starts the outdoor fan (12) and the indoor fan (62) and stops the refrigerated fan (72).

[0101] During heating operation, a refrigeration cycle is performed such that the indoor heat exchanger (64) functions as a radiator, the outdoor heat exchanger (24) functions as an evaporator, and the function of the refrigerated heat exchanger (74) is effectively stopped.

[0102] 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 sent to the air conditioning unit (60).

[0103] The refrigerant sent to the air conditioning unit (60) dissipates heat in the indoor heat exchanger (64). As a result, the indoor air is heated. The refrigerant that has dissipated heat in the indoor heat exchanger (64) flows into the gas-liquid separator (25). In the gas-liquid separator (25), the refrigerant is separated into gaseous refrigerant and liquid refrigerant.

[0104] The liquid refrigerant separated in the gas-liquid separator (25) is cooled in the subcooled heat exchanger (28) by the refrigerant flowing through the injection channel (43). The refrigerant in the injection channel (43) is sent to the intermediate channel (18).

[0105] The refrigerant 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 drawn into the second compressor (22) and compressed again.

[0106] (8-2) Components of an air conditioning system during heating In heating operation, the refrigerant circuit (6) includes a second compressor (22) of the compressor (20), a third compressor (23) of 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.

[0107] The air conditioning unit (60) as a user unit includes a first air conditioning unit (60A) as a first user unit and a second air conditioning unit (60B) as a second user unit. The first air conditioning unit (60A) and the second air conditioning unit (60B) are connected in parallel to each other.

[0108] The indoor heat exchanger (64) 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 to each other.

[0109] The indoor expansion valve (63), which functions 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 to each other.

[0110] The indoor fan (62) as a fan includes a first indoor fan (62A) as a first fan corresponding to the first indoor heat exchanger (64A), and a second indoor fan (62B) as a second fan corresponding to the second indoor heat exchanger (64B). The first indoor fan (62A) and the second indoor fan (62B) are connected in parallel to each other.

[0111] The indoor heat exchanger (64) as a heat radiator, the indoor expansion valve (63) as an expansion valve, and the indoor fan (62) as a fan constitute an air conditioning unit (60) as a utilization unit.

[0112] The first indoor heat exchanger (64A) as the first heat radiator, the first indoor expansion valve (63A) as the first expansion valve, and the first indoor fan (62A) as the first fan constitute the first air conditioning unit (60A) as the first utilization unit.

[0113] The second indoor heat exchanger (64B) as a second heat radiator, the second indoor expansion valve (63B) as a second expansion valve, and the second indoor fan (62B) as a second fan constitute the second air conditioning unit (60B) as a second utilization unit.

[0114] The refrigerant circuit (6) includes a gas-liquid separator (25), a gas vent pipe (41) as a gas venting passage, and a gas vent valve (42) as an on / off valve.

[0115] 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 refrigerant and liquid refrigerant. Inside the gas-liquid separator (25), a gas storage section (25a) and a liquid storage section (25b) are formed. The gas storage section (25a) is located at the top of the gas-liquid separator (25) and stores gaseous refrigerant. The liquid storage section (25b) is located at the bottom of the gas-liquid separator (25) and stores liquid refrigerant.

[0116] One end of the vent pipe (41) is connected to the gas storage section (25a) of the gas-liquid separator (25). The other end of the vent pipe (41) is connected to the intermediate passage (18). The intermediate passage (18) is connected to the third suction pipe (23a) on the suction side (20i) of the third compressor (23) of the compressor (20).

[0117] The gas vent pipe (41) connects the gas storage section (25a) of the gas-liquid separator (25) to the third suction pipe (23a) on the suction side (20i) of the third compressor (23) of the compressor (20) via the intermediate passage (18). The gas vent valve (42) is provided on the gas vent pipe (41).

[0118] The high-pressure sensor (101) detects the high pressure in the refrigerant circuit (6). The high pressure in the refrigerant circuit (6) is also the pressure of the refrigerant on the discharge side of the third compressor (23).

[0119] 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) as the temperature of the refrigerant 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).

[0120] The first indoor heat exchanger liquid-side temperature sensor (121A) detects the temperature of the refrigerant at the liquid-side end of the first indoor heat exchanger (64A). In heating operation, the first indoor heat exchanger liquid-side temperature sensor (121A) detects the first outlet refrigerant temperature (TEA), which is the temperature of the refrigerant 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 second indoor heat exchanger liquid-side temperature sensor (121B) detects the temperature of the refrigerant at the liquid-side end of the second indoor heat exchanger (64B). In heating operation, the second indoor heat exchanger liquid-side temperature sensor (121B) detects the second outlet refrigerant temperature (TEB), which is the temperature of the refrigerant 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).

[0121] The indoor heat exchanger gas-side temperature sensor (122) detects the temperature of the refrigerant at the gas 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) as the temperature of the refrigerant 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).

[0122] 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). During heating operation, the first indoor heat exchanger gas-side temperature sensor (122A) detects the first inlet refrigerant temperature (TIA), which is the temperature of the refrigerant 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 gas-side temperature sensor (122B) detects the temperature of the refrigerant at the gas-side end of the second indoor heat exchanger (64B). During heating operation, the second indoor heat exchanger gas-side temperature sensor (122B) detects the second inlet refrigerant temperature (TIB), which is the temperature of the refrigerant 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).

[0123] The indoor temperature sensor (124) detects the indoor temperature (TR) in the indoor space (RA), which is the user-side space where the air conditioning unit (60) (indoor heat exchanger (64)) is installed. The indoor space (R) is an example of a user-side space. The indoor space (R) corresponds to the air conditioning unit (60).

[0124] The interior space (R) includes the first interior space (RA) as the first user-side space and the second interior space (RB) as the second user-side space. The first interior space (RA) is an example of the first user-side space. The first interior space (RA) corresponds to the first air conditioning unit (60A). The second interior space (RB) is an example of the second user-side space. The second interior space (RB) corresponds to the second air conditioning unit (60B).

[0125] 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 the first indoor space (RA) where the 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 the second indoor space (RB) where the 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).

[0126] The receiver pressure sensor (105) detects the receiver pressure (Pd) as the pressure of the gas-liquid separator (25).

[0127] (9) Supercritical operation Figure 4 is a graph showing the relationship between specific enthalpy (h) and pressure (P) in a refrigerant. Figure 4 is also called a Ph diagram. The refrigerant circulating in the refrigerant circuit (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 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.

[0128] The refrigerant circuit (6) performs a refrigeration cycle to execute a heating operation that heats the indoor space (R) as the usage space by compressing the refrigerant to a critical pressure (Pc) or higher.

[0129] The refrigerant circuit (6) operates under supercritical conditions. The high pressure (Ph) of the refrigerant circuit (6) becomes equal to or greater than the critical pressure (Pc).

[0130] When the refrigerant is compressed above the critical pressure (Pc), in other words, when the high pressure (Ph) in the refrigerant circuit (6) exceeds the critical pressure (Pc), it becomes difficult to control the temperature of the refrigerant because there is no condensation temperature for the refrigerant in the region above the critical pressure (Pc).

[0131] The smaller the specific enthalpy (h) of the refrigerant, the greater the proportion of liquid in the refrigerant and the greater the proportion of gas in the refrigerant. The larger the specific enthalpy (h) of the refrigerant, the greater the proportion of liquid in the refrigerant and the greater the proportion of gas in the refrigerant.

[0132] As shown in Figure 4, the outlet specific enthalpy (he) of the refrigerant at the outlet (E) of the indoor heat exchanger (64) is smaller than the critical specific enthalpy (hc) of the refrigerant at its critical point (C). The refrigerant at the outlet (E) of the indoor heat exchanger (64) has a larger proportion of liquid and a smaller proportion of gas compared to the refrigerant at its critical point (C).

[0133] (10) Stop mode 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, we illustrate the case where 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 is a piping diagram for the case where the first air conditioning unit (60A) is in stop mode (M1) and the second air conditioning unit (60B) is in operation mode (M2).

[0134] In Figure 5, the thickness of the solid lines indicates the magnitude of the flow rate, and consequently, the magnitude of the opening of the first chamber expansion valve (63A) and the second chamber expansion valve (63B). The upper part of Figure 5 shows the first state (J1), which will be described later, and the lower part of Figure 5 shows the second state (J2), which will be described later.

[0135] The controller (130) reduces the opening of the first indoor expansion valve (63A) to less than the opening of the second indoor expansion valve (63B) 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 opening of the second indoor expansion valve (63B) in operation mode (M2) is, for example, fully open (100%). The opening of the first indoor expansion valve (63A) in stop mode (M1) will be described later.

[0136] The controller (130) controls the first indoor expansion valve (63A) to switch between a first state (J1) and a second state (J2) when the first air conditioning unit (60A) is in stop mode (M1). In the first state (J1), the first indoor expansion valve (63A) is fully 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 the operating mode (M2). The opening degree of the first indoor expansion valve (63A) in the second state (J2) is, for example, a few percent.

[0137] In operating mode (M2), the second indoor fan (62B) is operated. In stop mode (M1), the first indoor fan (62A) is stopped or operated at a lower load than in operating mode (M2).

[0138] When the first indoor expansion valve (63A) is in the first state (J1) (fully closed), liquid refrigerant accumulates in the first indoor heat exchanger (64A). Therefore, at the start of stop mode (M1), the first indoor expansion valve (63A) is in the second state (J2).

[0139] On the other hand, when the first chamber expansion valve (63A) is in the second state (J2), the receiver pressure (Pd) of the gas-liquid separator (25) rises. The reason why the receiver pressure (Pd) of the gas-liquid separator (25) rises when in the second state (J2) is because the air conditioning system (1) is operating in supercritical mode.

[0140] Therefore, the controller (130) switches the first chamber expansion valve (63A) from the second state (J2) to the first state (J1) based on the rise in the receiver pressure (Pd) as the pressure of the gas-liquid separator (25). As will be described later, the rise in the receiver pressure (Pd) of the gas-liquid separator (25) may be measured directly by the receiver pressure sensor (105) or determined indirectly by other means.

[0141] The controller (130) switches the first indoor expansion valve (63A) from the second state (J2) to the first state (J1) when the difference between the first inlet refrigerant temperature (TIA) of the first indoor heat exchanger (64A) at the first inlet (IA) and the first outlet refrigerant temperature (TEA) of the first indoor heat exchanger (64A) is greater than a first value (Q1). 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 a few degrees Celsius.

[0142] Alternatively, the controller (130) switches the first indoor expansion valve (63A) from the second state (J2) to the first state (J1) when the first outlet refrigerant temperature (TEA) of the first outlet (EA) of the first indoor heat exchanger (64A) rises over time. For example, this could occur when the first outlet refrigerant temperature (TEA) rises by several degrees Celsius over a period of time ranging from a few seconds to a few minutes.

[0143] Alternatively, the controller (130) switches the first chamber expansion valve (63A) from the second state (J2) to the first state (J1) when the duration of the second state (J2) is greater than the second value (Q2). The second value (Q2) is, for example, several seconds to several minutes.

[0144] Alternatively, the controller (130) may switch the first chamber expansion valve (63A) from the second state (J2) to the first state (J1) when the receiver pressure (Pd) of the gas-liquid separator (25), as measured by the receiver pressure sensor (105), rises above a threshold, or when the receiver pressure (Pd) of the gas-liquid separator (25), as measured by the receiver pressure sensor (105), rises over time (for example, when it rises by several Pa over a period of time from a few seconds to a few minutes).

[0145] 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).

[0146] Specifically, the controller (130) switches the first indoor expansion valve (63A) from the first state (J1) to the second state (J2) when the first inlet refrigerant temperature (TIA) of the refrigerant 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.

[0147] Alternatively, the controller (130) switches the first indoor expansion valve (63A) from the first state (J1) to the second state (J2) when the difference between the first inlet refrigerant temperature (TIA) of the refrigerant at the first inlet (IA) of the first indoor heat exchanger (64A) and the first outlet refrigerant temperature (TEA) of the refrigerant at the first outlet (EA) of the first indoor heat exchanger (64A) is smaller than the third value (Q3). 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 a few degrees Celsius.

[0148] Alternatively, the controller (130) switches the first indoor expansion valve (63A) from the first state (J1) to the second state (J2) when the difference between the first inlet refrigerant temperature (TIA) of the refrigerant 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 utilization side space) related to the first air conditioning unit (60A) (first utilization unit) is smaller than the fourth value (Q4). 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 a few degrees Celsius.

[0149] Alternatively, the controller (130) switches the first chamber expansion valve (63A) from the first state (J1) to the second state (J2) when the duration of the first state (J1) is greater than the fifth value (Q5). The fifth value (Q5) is, for example, several seconds to several minutes.

[0150] (11) Starting the heating operation This section describes how to start the heating operation in the air conditioning system (1). Only the startup of the heating operation in the first air conditioning unit (60A) will be described; the explanation for the startup of the heating operation in the second air conditioning unit (60B) will be omitted.

[0151] The controller (130) executes the start mode (M3) for the first air conditioning unit (60A). In start mode (M3), the controller (130) starts the heating operation with the first indoor fan (62A) in the first air conditioning unit (60A) stopped. In start mode (M3), after the heating operation has started, the controller (130) drives the first indoor fan (62A) when the first outlet refrigerant temperature (TEA) of the refrigerant 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.

[0152] In startup mode (M3), the controller (130) opens the gas vent valve (42) of the gas vent pipe (41) when starting the heating operation. Note that "opening the gas vent valve (42)" includes not only opening the gas vent valve (42) which is currently at zero opening, but also increasing the opening of the gas vent valve (42) which is already open.

[0153] The same applies when the second air conditioning unit (60B) is started up.

[0154] (12) Control flow Figure 6 is a control flowchart of the first air conditioning unit (60A). Starting from the start, in the first step (S1), the first air conditioning unit (60A) enters startup mode (M3) upon receiving a heating operation start command from the user to the controller (130).

[0155] In the second step (S2), the controller (130) starts the heating operation with the first indoor fan (62A) in the first air conditioning unit (60A) 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 gas vent valve (42) of the gas vent pipe (41) remains closed.

[0156] In the third step (S3), the controller (130) determines whether the first outlet refrigerant temperature (TEA) of the refrigerant 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, the process returns to the second step (S2).

[0157] In the fourth step (S4), the controller (130) opens the gas vent valve (42) of the gas vent pipe (41).

[0158] In step 5 (S5), the first air conditioning unit (60A) switches to operating mode (M2).

[0159] In step 6 (S6), the first air conditioning unit (60A) enters stop mode (M1) (thermo-off mode) in response to a stop command (thermo-off command) from the user to the controller (130).

[0160] In step 7 (S7), the first chamber expansion valve (63A) is set to the second state (J2). Specifically, the opening of the first chamber expansion valve (63A) is reduced to, for example, a few percent.

[0161] In step 8 (S8), the controller (130) determines whether the receiver pressure (Pd) of the gas-liquid separator (25) has risen. 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 the first value (Q1), the first outlet refrigerant temperature (TEA) has risen over time, or the duration of the second state (J2) is greater than the second value (Q2).

[0162] Alternatively, the controller (130) may determine whether either of the following conditions is met: the receiver pressure (Pd) of the gas-liquid separator (25) has risen above a threshold, or the receiver pressure (Pd) of the gas-liquid separator (25) has risen over time.

[0163] If the above conditions are met, proceed to step 9 (S9). If the above conditions are not met, return to step 7 (S7).

[0164] In step 9 (S9), the first chamber expansion valve (63A) is set to the first state (J1). Specifically, the opening degree of the first chamber expansion valve (63A) is set to fully closed (0%).

[0165] In the tenth step (S10), the controller (130) determines whether or not liquid refrigerant has accumulated in the first indoor heat exchanger (64A).

[0166] 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 room temperature (TRA) is less than the fourth value (Q4), or the duration of the first state (J1) is greater than the fifth value (Q5).

[0167] If the above conditions are met, return to step 7 (S7). If the above conditions are not met, proceed to step 11 (S11).

[0168] In step 11 (S11), it is determined whether or not there is a command from the user to terminate operation. If there is a command to terminate operation, proceed to step 12 (S12). If there is no command to terminate operation, return to step 7 (S7).

[0169] In step 12 (S12), the controller (130) terminates the operation of the first air conditioning unit (60A). Then, the process ends.

[0170] In stop mode (M1), steps 7 (S7) (second state (J2)) and 9 (S9) (first state (J1)) are repeated.

[0171] The controller (130) may return to step 5 (S5) based on a driving mode transition command from the user.

[0172] The controller (130) may perform each operation automatically without relying on each command from the user.

[0173] (Effects and Benefits) According to this embodiment, in a multi-type air conditioning system (1) that performs supercritical operation, it becomes possible to stop the first air conditioning unit (60A) of the two air conditioning units (60B) (1st air conditioning unit (60A)).

[0174] 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), and thereby throttling the first indoor expansion valve (63A) of the first air conditioning unit (60A), it is possible to suppress the rise in refrigerant pressure downstream of the indoor heat exchanger (64) of the air conditioning unit (60). In particular, it is possible to suppress the rise in the receiver pressure (Pd) of the gas-liquid separator (25) located downstream of the indoor heat exchanger (64) of the air conditioning unit (60).

[0175] Furthermore, 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) and opening the first indoor expansion valve (63A) of the first air conditioning unit (60A), it is possible to suppress the accumulation of liquid refrigerant in the first indoor heat exchanger (64A) of the first air conditioning unit (60A).

[0176] When the receiver pressure (Pd) of the gas-liquid separator (25) located downstream of the indoor heat exchanger (64) of the air conditioning unit (60) rises, the rise in the receiver pressure (Pd) of the gas-liquid separator (25) can be suppressed 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) and thereby throttling the first indoor expansion valve (63A) of the first air conditioning unit (60A).

[0177] Even without directly measuring the receiver 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 receiver pressure (Pd) of the gas-liquid separator (25) rises.

[0178] The first air conditioning unit (60A) can be stopped while the second air conditioning unit (60B) is in operation.

[0179] 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) from the compressor (20) from becoming too high immediately after starting the heating operation.

[0180] When starting the heating operation, the rate at which the high pressure (Ph) is raised by the compressor (20) can be increased by promoting the inflow of gaseous refrigerant from the gas storage section (25a) of the gas-liquid separator (25) to the suction side (20i) of the compressor (20).

[0181] Using carbon dioxide as a refrigerant offers advantages from an environmental protection standpoint.

[0182] <Second Embodiment> The air conditioning system (1) according to the second embodiment will now be described. In the following description, components similar to those in the above embodiment will be denoted by the same reference numerals, and detailed descriptions will be omitted. Figure 7 is a piping diagram of the second embodiment when the first air conditioning unit (60A) is in stop mode (M1) and the second air conditioning unit (60B) is in operation mode (M2).

[0183] In the first state (J1), the first chamber expansion valve (63A) is not fully closed, but is open to a small degree. However, the small degree of opening of the first chamber expansion valve (63A) in the first state (J1) is smaller than the degree of opening of the first chamber expansion valve (63A) in the second state (J2). In other words, the degree of opening of the first chamber expansion valve (63A) in the second state (J2) is larger than the small degree of 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 more widely than in the first state (J1). The small degree of opening of the first chamber expansion valve (63A) in the first state (J1) is, for example, a few percent or less.

[0184] The other configurations are the same as in the first embodiment. According to this embodiment, the same effects as in the first embodiment can be obtained.

[0185] <Other Embodiments> A single compressor (single stage) is sufficient.

[0186] There may be three or more indoor heat exchangers (64) used as radiators.

[0187] The air conditioning system (1) may be configured in a way that omits the cooling unit (70).

[0188] The refrigerant does not have to be carbon dioxide.

[0189] A refrigeration unit (70) may be applied as all or part of the first utilization unit and the second utilization unit.

[0190] Although embodiments and modifications have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims. Furthermore, elements of the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate.

[0191] The designations "1st," "2nd," "3rd," etc., mentioned above are used to distinguish between the terms to which these designations are attached, and do not limit the number or order of those terms. [Explanation of Symbols]

[0192] 1. Air conditioning system 6. Refrigerant Circuit 20 Compressors 20i suction side 24. Outdoor heat exchanger (evaporator) 25 Gas-liquid separator 25a Gas storage section 41. Gas vent pipe (gas vent passage) 42. Gas vent valve (on / off valve) 60A First Air Conditioning Unit (First Utilization Unit) 60B Second air conditioning unit (second usage unit) 62A First Indoor Fan (Fan) 63. Indoor expansion valve (expansion valve) 63A First Chamber Expansion Valve (First Expansion Valve) 63B Second Chamber Expansion Valve (Second Expansion Valve) 64 Indoor heat exchanger (radiator) 64A 1st indoor heat exchanger (1st radiator) 64B 2nd indoor heat exchanger (2nd radiator) 130 Control device C critical point Pc critical pressure Tc critical temperature (temperature) R Indoor space (user side space) RA 1st indoor space (user side space) Pd Receiver pressure (pressure) IA Entrance 1 (Entrance) TIA 1st inlet refrigerant temperature (temperature) EA 1st exit (exit) TEA 1st outlet refrigerant temperature (temperature) Q1 1st value Q2 Second Value Q3 Third Value Q4 4th value Q5 Fifth Value M1 Stop Mode M2 driving mode J1 First Stage J2 Second Stage

Claims

1. A refrigerant circuit (6) having a compressor (20), a heat exchanger (64), an expansion valve (63), and an evaporator (24), and performing a refrigeration cycle for heating operation that heats the user-side space (R) by compressing the refrigerant to a critical pressure (Pc) or higher, The system includes a control device (130) that controls the refrigerant circuit (6), The heat sink (64) includes a first heat sink (64A) and a second heat sink (64B) connected in parallel to each other. The expansion valve (63) includes a first expansion valve (63A) corresponding to the first heat sink (64A) and a second expansion valve (63B) corresponding to the second heat sink (64B), The first heat sink (64A) and the first expansion valve (63A) constitute the first utilization unit (60A), The second heat sink (64B) and the second expansion valve (63B) constitute the second utilization unit (60B), The control device (130) controls the first expansion valve (63A) to switch between a first state (J1) in which the first expansion valve (63A) is fully closed or opened to a small degree, and a second state (J2) in which the first expansion valve (63A) is opened more than in the first state (J1), when the first utilization unit (60A) is in stop mode (M1). The refrigerant circuit (6) is connected downstream of the heat exchanger (64) and includes a gas-liquid separator (25) that separates the refrigerant into gaseous and liquid refrigerants. 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), and is an air conditioning system.

2. The control device (130) is When the difference between the temperature of the refrigerant at the inlet (IA) of the first heat sink (64A) (TIA) and the temperature of the refrigerant at the outlet (EA) of the first heat sink (64A) (TEA) is greater than the first value (Q1), Or, When the temperature of the refrigerant (TEA) at the outlet (EA) of the first heat sink (64A) rises over time, Switch the first expansion valve (63A) from the second state (J2) to the first state (J1). The air conditioning device according to claim 1.

3. The air conditioning device according to claim 1, wherein the control device (130) switches the first expansion valve (63A) from the second state (J2) to the first state (J1) when the duration of the second state (J2) is greater than the second value (Q2).

4. The control device (130) is When the temperature of the refrigerant (TIA) at the inlet (IA) of the first heat sink (64A) is less than the temperature (Tc) at the critical point (C) of the refrigerant, When the difference between the temperature of the refrigerant at the inlet (IA) of the first heat sink (64A) (TIA) and the temperature of the refrigerant at the outlet (EA) of the first heat sink (64A) (TEA) is less than the third value (Q3), Or, When the difference between the temperature of the refrigerant (TIA) at the inlet (IA) of the first heat sink (64A) and the temperature of the utilization-side space (RA) related to the first utilization unit (60A) (TRA) is less than the fourth value (Q4), When the duration of the first state (J1) is greater than the fifth value (Q5), Switch the first expansion valve (63A) from the first state (J1) to the second state (J2). An air conditioning device according to any one of claims 1 to 3.

5. The air conditioning system according to any one of claims 1 to 3, wherein the control device (130) makes the opening degree of the first expansion valve (63A) smaller than the opening degree of the second expansion valve (63B) when the first utilization unit (60A) is in stop mode (M1) and the second utilization unit (60B) is in operation mode (M2).

6. The control device (130) starts the heating operation with the fan (62A) in the first utilization unit (60A) stopped. The air conditioning system according to any one of claims 1 to 3, wherein the control device (130) drives the fan (62A) when, after the start of heating operation, the temperature (TEA) of the refrigerant at the outlet (EA) of the first radiator (64A) becomes greater than the temperature (Tc) of the refrigerant at its critical point (C).

7. The refrigerant circuit (6) includes a gas-liquid separator (25) connected downstream of the heat exchanger (64) and separating the refrigerant into gaseous and liquid refrigerant, a gas venting passage (41) connecting the gas storage section (25a) of the gas-liquid separator (25) and the suction side (20i) of the compressor (20), and an on / off valve (42) provided in the gas venting passage (41). The air conditioning device according to claim 6, wherein the control device (130) opens the on / off valve (42) when the heating operation is started.

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