AIR CONDITIONING SYSTEM

Abstract

 An air conditioning system (100) includes a refrigerant circuit (10), a heat exchanger (30a, 30b, 30c), a shutoff valve (70), and a refrigerant leakage sensor (50a, 50b, 50c). The refrigerant circuit includes a first part (11a, 11b, 11c) and a second part (12). The heat exchanger is provided in the first part and exchanges heat between a refrigerant and air in an air conditioning target space. The shutoff valve is provided in the refrigerant circuit and shuts off communication between the first part and the second part. The refrigerant leakage sensor detects that refrigerant concentration is within a first range and detects the refrigerant leaked from the first part. The shutoff valve is placed to set the refrigerant concentration in the air conditioning target space within a second range larger than the first range, when it is assumed that all the refrigerant present in the first part has leaked to the air conditioning target space.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an air conditioning system.

BACKGROUND ART

[0002] Patent Literature 1 (Japanese Laid-Open Patent Application No. 2019-45129) discloses an air conditioning system in which a shutoff valve is connected to the outside of a utilization-side unit. The shutoff valve is a part to be closed when a refrigerant leakage is detected, and shuts off the flow between a heat source-side unit and the utilization-side unit to prevent all the refrigerant filled in a refrigerant circuit of the air conditioning system from leaking.

SUMMARY OF THE INVENTION

<Technical Problem>

[0003] If refrigerant leakage occurs in the utilization-side unit, it is considered that the refrigerant contained in the refrigerant flow path connecting the utilization-side unit to the shutoff valve leaks to an air conditioning target space. Therefore, depending on the distance between the shutoff valve and the utilization-side unit, the refrigerant concentration in the air conditioning target space may exceed LFL (Lower Flammability Limit) However, no detailed study has been made in the past as to where to place the shutoff valve with respect to the utilization-side unit.

<Solution to Problem>

[0004] An air conditioning system of a first aspect includes a refrigerant circuit, a heat exchanger, a shutoff valve, and a refrigerant leakage sensor. The refrigerant circuit includes a first part and a second part. The heat exchanger is provided in the first part, and cools or heats air in an air conditioning target space by exchanging heat between a refrigerant and the air in the air conditioning target space. The shutoff valve is provided in the refrigerant circuit and shuts off communication between the first part and the second part. The refrigerant leakage sensor detects the refrigerant leaked from the first part. The refrigerant leakage sensor detects that refrigerant concentration is within a first range. The shutoff valve is placed to set the refrigerant concentration in the air conditioning target space within a second range larger than the first range, when it is assumed that all the refrigerant present in the first part has leaked to the air conditioning target space.

[0005] In the air conditioning system of the first aspect, the shutoff valve is placed at a position where the refrigerant concentration in the air conditioning target space is within the second range even if all the refrigerant present in the first part has leaked to the air conditioning target space. This inhibits the refrigerant concentration in the air conditioning target space from exceeding LFL.

[0006] The air conditioning system of a second aspect is the air conditioning system of the first aspect, in which when the lower limit concentration of refrigerant combustion is LFL [kg/m³], the first range is from LFL/X1 to LFL/X2 and the second range is from LFL/Y1 to LFL/Y2. X1 is larger than Y1, and X2 is larger than Y2.

[0007] The air conditioning system of the second aspect sets the first range and the second range such that the refrigerant concentration is smaller than LFL in the air conditioning target space. This inhibits the refrigerant concentration in the air conditioning target space from exceeding LFL.

[0008] The air conditioning system of a third aspect is the air conditioning system of the first aspect or the second aspect, in which the refrigerant circuit includes a utilization-side refrigerant flow path that is part of the first part, a heat source-side refrigerant flow path that is part of the second part, and a first connection flow path and a second connection flow path connecting the utilization-side refrigerant flow path to the heat source-side refrigerant flow path. The shutoff valve includes a first shutoff valve provided in the first connection flow path and a second shutoff valve provided in the second connection flow path. The first connection flow path includes a utilization-side first connection flow path between the utilization-side refrigerant flow path and the first shutoff valve, and a heat source-side first connection flow path between the heat source-side refrigerant flow path and the first shutoff valve. The second connection flow path includes a utilization-side second connection flow path between the utilization-side refrigerant flow path and the second shutoff valve, and a heat source-side second connection flow path between the heat source-side refrigerant flow path and the second shutoff valve. The first shutoff valve and the second shutoff valve are placed based on volume of the utilization-side refrigerant flow path, volume of the utilization-side first connection flow path, volume of the utilization-side second connection flow path, and volume of the air conditioning target space.

[0009] In the air conditioning system of the third aspect, the first shutoff valve and the second shutoff valve are placed based on the volume of the utilization-side refrigerant flow path, the volume of the utilization-side first connection flow path, the volume of the utilization-side second connection flow path, and the volume of the air conditioning target space. This inhibits the refrigerant concentration in the air conditioning target space from exceeding LFL.

[0010] The air conditioning system of a fourth aspect is the air conditioning system of the first aspect, in which when the lower limit concentration of refrigerant combustion is LFL [kg/m³], the first range is from LFL/X1 to LFL/X2 and the second range is from LFL/Y1 to LFL/Y2. LFL/Y1 is larger than LFL/X1, and LFL/Y2 is larger than LFL/X2.

[0011] The air conditioning system of the fourth aspect sets the first range and the second range such that the refrigerant concentration is smaller than LFL in the air conditioning target space. The refrigerant leakage sensor is configured to detect the refrigerant in the first range having refrigerant concentration smaller than the refrigerant concentration in the second range in both upper limit and lower limit. This inhibits the refrigerant concentration in the air conditioning target space from exceeding LFL.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] 

FIG. 1 is a diagram showing a schematic configuration of an air conditioning system as one embodiment of a refrigerant cycle device.

FIG. 2 is a control block diagram of the air conditioning system.

FIG. 3 is a control flowchart when a refrigerant leaks

FIG. 4 is a schematic configuration diagram of the air conditioning system according to Modification A.

FIG. 5 is a schematic configuration diagram of the air conditioning system according to Modification B.

FIG. 6 is a schematic configuration diagram of the air conditioning system according to Modification E.

DESCRIPTION OF EMBODIMENT

[0013] With reference to the drawings, an air conditioning system 100 according to one embodiment of the present disclosure will be described below.

(1) Overall configuration

(1-1) Air conditioning system

[0014] The outline of the air conditioning system 100 including an air conditioning apparatus 1 according to one embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic configuration diagram of the air conditioning system 100. The air conditioning apparatus 1 of the air conditioning system 100 is an apparatus that performs vapor compression refrigeration cycle and cools and heats air conditioning target space. The air conditioning target space is, for example, an office or a living room in a house. In the present embodiment, the air conditioning apparatus 1 is an apparatus that can both cool and heat the air conditioning target space. However, the air conditioning apparatus 1 of the present disclosure is not limited to the air conditioning apparatus capable of both cooling and heating, and may be, for example, an apparatus capable of only cooling.

[0015] The air conditioning apparatus 1 of the air conditioning system 100 mainly includes a heat source-side unit 2, a plurality of utilization-side units 3a, 3b, and 3c, a first connection flow path 21, a second connection flow path 22, and a control unit 19 (see FIG. 2). The plurality of utilization-side units 3a, 3b, and 3c is connected in parallel to the heat source-side unit 2. The first connection flow path 21 and the second connection flow path 22 connect the heat source-side unit 2 to the utilization-side units 3a, 3b, and 3c via a shutoff valve 70. The first connection flow path 21 and the second connection flow path 22 are laid at an installation site of the air conditioning apparatus 1. The pipe diameter and the pipe length of the first connection flow path 21 and the second connection flow path 22 are selected according to the design specification and the installation environment. The control unit 19 controls the heat source-side unit 2, the utilization-side units 3a, 3b, and 3c, and the shutoff valve 70. A vapor compression refrigerant circuit 10 of the air conditioning apparatus 1 is configured by connecting a heat source-side refrigerant flow path 14 of the heat source-side unit 2 to utilization-side refrigerant flow paths 13a, 13b, and 13c of the utilization-side units 3a, 3b, and 3c by the first connection flow path 21 and the second connection flow path 22 via the shutoff valve 70. The heat source-side refrigerant flow path 14 is a refrigerant flow path provided inside the heat source-side unit 2. The utilization-side refrigerant flow paths 13a, 13b, and 13c are refrigerant flow paths provided inside the utilization-side units 3a, 3b, and 3c, respectively. The first connection flow path 21 includes utilization-side first connection flow paths 21aa, 21ab, and 21ac and a heat source-side first connection flow path 21b. As shown in FIG. 1, the utilization-side first connection flow paths 21aa, 21ab, and 21ac and the heat source-side first connection flow path 21b are divided by first shutoff valves 71a, 71b, and 71c, respectively. The second connection flow path 22 includes utilization-side second connection flow paths 22aa, 22ab, and 22ac and a heat source-side second connection flow path 22b. As shown in FIG. 1, the utilization-side second connection flow paths 22aa, 22ab, and 22ac and the heat source-side second connection flow path 22b are divided by second shutoff valves 72a, 72b, and 72c, respectively. The shutoff valve 70 is disposed in the refrigerant circuit 10. The shutoff valve 70 includes the first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c.

[0016] Although not restrictive, the refrigerant circuit 10 is filled with a flammable refrigerant. The flammable refrigerant includes the refrigerant categorized as Class 3 (higher flammability), Class 2 (lower flammability), and Subclass 2L (slight flammability) according to the standards of ASHRAE 34, Designation and safety classification of refrigerant in the Unites States or the standards of ISO 817, Refrigerants - designation and safety classification. For example, as the refrigerant, any one of R1234yf, R1234ze(E), R516A, R445A, R444A, R454C, R444B, R454A, R455A, R457A, R459B, R452B, R454B, R447B, R32, R447A, R446A, and R459A is adopted. In the present embodiment, the refrigerant to use is R32. If R32 leaks from the refrigerant circuit 10 to the air conditioning target space (inside room) and the refrigerant concentration in the room increases, a combustion accident may occur due to the flammability of the refrigerant. It is required to prevent this combustion accident.

[0017] Note that the air conditioning system 100 and the air conditioning apparatus 1 of the present disclosure are also useful when the refrigerant is not flammable.

[0018] The configuration of the air conditioning system 100 including the air conditioning apparatus 1 will be described in detail below.

(2) Detailed configuration

(2-1) Refrigerant circuit

[0019] The refrigerant circuit 10 of the air conditioning apparatus 1 is divided by the plurality of first shutoff valves 71a, 71b, and 71c and the plurality of second shutoff valves 72a, 72b, and 72c into a plurality of first parts 11a, 11b, and 11c and a second part 12. Note that since the first shutoff valve 71a and the first shutoff valves 71b and 71c have similar configurations, only the configuration of the first shutoff valve 71a is described here. The description of the configurations of the first shutoff valves 71b and 71c is omitted, and instead of the subscript "a" indicating each part of the first shutoff valve 71a, the subscripts "b" and "c" are added, respectively. The second shutoff valves 72a, 72b, and 72c and the first parts 11a, 11b, and 11c are described in a similar manner.

[0020] The first shutoff valve 71a is a shutoff valve that shuts off the flow of the liquid refrigerant flowing inside the first connection flow path 21 under the control of the control unit 19. The first connection flow path 21 is divided by the first shutoff valve 71a into the utilization-side first connection flow path 21aa and the heat source-side first connection flow path 21b. The first shutoff valve 71a is connected to the liquid side of the utilization-side refrigerant flow path 13a by the utilization-side first connection flow path 21aa. The first shutoff valve 71a is connected to the heat source-side refrigerant flow path 14 by the heat source-side first connection flow path 21b.

[0021] The second shutoff valve 72a is a shutoff valve that shuts off the flow of the gas refrigerant flowing inside the second connection flow path 22 under the control of the control unit 19. The second connection flow path 22 is divided by the second shutoff valve 72a into the utilization-side second connection flow path 22aa and the heat source-side second connection flow path 22b. The second shutoff valve 72a is connected to the gas side of the utilization-side refrigerant flow path 13a by the utilization-side second connection flow path 22aa. The second shutoff valve 72a is connected to the heat source-side refrigerant flow path 14 by the heat source-side second connection flow path 22b.

[0022] The first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c may be disposed near the utilization-side units 3a, 3b, and 3c, but may be disposed away from the utilization-side units 3a, 3b, and 3c, respectively. Alternatively, as will be described in Modification E, the first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c may be disposed inside a casing of the utilization-side units 3a, 3b, and 3c, respectively.

[0023] As shown in FIG. 1, the first parts 11a, 11b, and 11c refer to utilization-side parts in the refrigerant circuit 10 divided by the first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c, respectively. The first part 11a includes the utilization-side refrigerant flow path 13a, the utilization-side first connection flow path 21aa, and the utilization-side second connection flow path 22aa. The detailed configuration of the utilization-side refrigerant flow path 13a will be described later. The utilization-side first connection flow path 21aa is part of the first connection flow path 21. The utilization-side first connection flow path 21aa connects the utilization-side refrigerant flow path 13a to the first shutoff valve 71a. The utilization-side second connection flow path 22aa is part of the second connection flow path 22. The utilization-side second connection flow path 22aa connects the utilization-side refrigerant flow path 13a to the second shutoff valve 72a.

[0024] As shown in FIG. 1, the second part 12 refers to a heat source-side part in the refrigerant circuit 10 divided by the first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c. The second part 12 includes the heat source-side refrigerant flow path 14, the heat source-side first connection flow path 21b, and the heat source-side second connection flow path 22b. The detailed configuration of the heat source-side refrigerant flow path 14 will be described later. The heat source-side first connection flow path 21b is part of the first connection flow path 21. The heat source-side first connection flow path 21b connects the heat source-side refrigerant flow path 14 to the first shutoff valve 71a. The heat source-side second connection flow path 22b is part of the second connection flow path 22. The heat source-side second connection flow path 22b connects the heat source-side refrigerant flow path 14 to the second shutoff valve 72a.

[0025] As will be described in detail later, if a refrigerant leakage occurs in the first part 11a, the control unit 19 causes the first shutoff valve 71a and the second shutoff valve 72a to shut off the refrigerant flow between the first part 11a and the second part 12. If the refrigerant flow between the first part 11a and the second part 12 is shut off, the total amount of refrigerant that may flow from the first part 11a into the air conditioning target space is equal to the total amount of refrigerant filled in the first part 11a.

[0026] The utilization-side unit 3 and the heat source-side unit 2 constituting part of the first part 11a and the second part 12 will be described below.

(2-2) Utilization-side unit

[0027] The utilization-side units 3a, 3b, and 3c are installed in the air conditioning target space such as in a room of a building. As described above, the utilization-side refrigerant flow paths 13a, 13b, and 13c of the utilization-side units 3a, 3b, and 3c are connected to the heat source-side unit 2 via the first connection flow path 21, the second connection flow path 22, and the shutoff valve 70, and constitutes part of the refrigerant circuit 10.

[0028] The configuration of the utilization-side units 3a, 3b, and 3c will be described. Note that since the utilization-side unit 3a and the utilization-side units 3b and 3c have similar configurations, only the configuration of the utilization-side unit 3a will be described here. The description of the configurations of the utilization-side units 3b and 3c is omitted, and instead of the subscript "a" indicating each part of the utilization-side unit 3a, the subscripts "b" and "c" are added, respectively. However, the utilization-side units 3a, 3b, and 3c do not have to have similar configurations, and for example, the capacity of the utilization-side units 3a, 3b, and 3c may be different from each other. The number of utilization-side units is not limited to three, and may be one, two, or three or more.

[0029] The utilization-side unit 3a mainly includes a utilization-side expansion valve 34a and a utilization-side heat exchanger (heat exchanger) 30a. Note that although detailed description is omitted, the utilization-side unit 3a includes a casing, and various constituent devices of the utilization-side unit 3a are housed inside the casing of the utilization-side unit 3a.

[0030] The utilization-side unit 3a includes the utilization-side refrigerant flow path 13a provided inside the utilization-side unit 3a. The utilization-side refrigerant flow path 13a includes the utilization-side heat exchanger (heat exchanger) 30a placed inside the utilization-side unit 3a, the utilization-side expansion valve 34a, and a utilization-side liquid refrigerant pipe 37a connecting the liquid side end of the utilization-side heat exchanger (heat exchanger) 30a to the utilization-side expansion valve 34a.

[0031] The utilization-side expansion valve 34a is an electrically powered expansion valve configured to adjust the flow rate of refrigerant flowing in the utilization-side heat exchanger (heat exchanger) 30a while decompressing the refrigerant, and is provided in the utilization-side liquid refrigerant pipe 37a. Note that the utilization-side expansion valve 34a is not limited to the electrically powered expansion valve, and may be another type of expansion valve such as a temperature automatic expansion valve.

[0032] The utilization-side heat exchanger (heat exchanger) 30a is a heat exchanger that functions as a refrigerant evaporator to cool indoor air, or functions as a refrigerant radiator to heat indoor air. The utilization-side heat exchanger (heat exchanger) 30a, which is not limited in terms of type, is a fin-and-tube heat exchanger including a plurality of heat transfer tubes and a plurality of fins, for example. Here, the utilization-side unit 3a includes a utilization-side fan 36a. The utilization-side fan 36a supplies the utilization-side heat exchanger (heat exchanger) 30a with indoor air as a cooling source or a heating source for the refrigerant flowing in the utilization-side heat exchanger (heat exchanger) 30a. The utilization-side fan 36a is, for example, a centrifugal fan such as a turbo fan or a sirocco fan. The utilization-side fan 36a is, but is not limited to, an inverter-controlled fan, for example.

[0033] The utilization-side unit 3a is provided with various sensors, although illustration is omitted. The sensors (not shown) include, but are not limited to, a sensor that detect the temperature of the refrigerant at the liquid side end of the utilization-side heat exchanger (heat exchanger) 30a, a sensor that detects the temperature of the refrigerant at the gas side end of the utilization-side heat exchanger (heat exchanger) 30a, a temperature sensor that measures the temperature in the air conditioning target space, and the like. The utilization-side unit 3a is provided with a refrigerant leakage sensor 50a that detects a refrigerant leakage. The refrigerant leakage sensor 50a in the present disclosure is configured to detect the refrigerant having refrigerant concentration in the range of LFL/X1 to LFL/X2. As the refrigerant leakage sensor 50a, for example, a semiconductor gas sensor or a detection unit that detects a sharp drop in the refrigerant pressure inside the utilization-side unit 3a can be adopted. When the semiconductor gas sensor is used, the semiconductor gas sensor is connected to a utilization-side control unit 93a (see FIG. 2). When the detection unit that detects a sharp drop in the refrigerant pressure is adopted, a pressure sensor is installed in the refrigerant pipe, and the utilization-side control unit 93a is provided with detection algorithm to determine refrigerant leakage from a change in a value of the sensor.

[0034] Note that here, the refrigerant leakage sensor 50a is provided in the utilization-side unit 3a, but the present disclosure is not limited to this example. The refrigerant leakage sensor 50a may be provided in a remote controller for operating the utilization-side unit 3a, in the air conditioning target space where the utilization-side unit 3a performs air conditioning, or the like.

(2-3) Heat source-side unit

[0035] The heat source-side unit 2 is installed outside a structure such as a building, for example, on the roof or on the ground. As described above, the heat source-side refrigerant flow path 14 of the heat source-side unit 2 is connected to the utilization-side units 3a, 3b, and 3c via the first connection flow path 21, the second connection flow path 22, and the shutoff valve 70, and constitutes part of the refrigerant circuit 10.

[0036] The heat source-side unit 2 mainly includes a compressor 25, a heat source-side heat exchanger 23, a switching mechanism 15, a first closing valve 17a, and a second closing valve 17b. Note that although detailed description is omitted, the heat source-side unit 2 includes a casing, and various constituent devices of the heat source-side unit 2 are housed inside the casing of the heat source-side unit 2. The switching mechanism 15 switches between a cooling operation state in which the heat source-side heat exchanger 23 functions as a refrigerant radiator and the utilization-side heat exchangers (heat exchangers) 30a, 30b, and 30c function as refrigerant evaporators, and a heating operation state in which the heat source-side heat exchanger 23 functions as a refrigerant evaporator and the utilization-side heat exchangers (heat exchangers) 30a, 30b, and 30c function as refrigerant radiators.

[0037] The heat source-side refrigerant flow path 14 of the heat source-side unit 2 includes, as refrigerant pipes, a suction pipe 31, a discharge pipe 32, a heat source-side first gas refrigerant pipe 33, a heat source-side liquid refrigerant pipe 38, and a heat source-side second gas refrigerant pipe 35 (see FIG. 1). The suction pipe 31 connects the switching mechanism 15 to the suction side of the compressor 25. The discharge pipe 32 connects the discharge side of the compressor 25 to the switching mechanism 15. The heat source-side first gas refrigerant pipe 33 connects the switching mechanism 15 to the gas side end of the heat source-side heat exchanger 23. The heat source-side liquid refrigerant pipe 38 connects the liquid side end of the heat source-side heat exchanger 23 to the first closing valve 17a. A heat source-side expansion valve 26 is provided in the heat source-side liquid refrigerant pipe 38. The heat source-side second gas refrigerant pipe 35 connects the switching mechanism 15 to the second closing valve 17b.

[0038] The compressor 25 sucks and compresses the low-pressure gas refrigerant in the refrigeration cycle, and discharges the high-pressure gas refrigerant in the refrigeration cycle. The compressor 25 is, for example, an inverter-controlled compressor. However, the compressor 25 may be a constant speed compressor.

[0039] The switching mechanism 15 is a device that can switch the flow of refrigerant in the refrigerant circuit 10, and includes, for example, a four-way switching valve. When the heat source-side heat exchanger 23 functions as a refrigerant radiator and the utilization-side heat exchangers (heat exchangers) 30a, 30b, and 30c function as refrigerant evaporators (in the cooling operation state), the switching mechanism 15 connects the discharge side of the compressor 25 to the gas side of the heat source-side heat exchanger 23 (see the solid line of the switching mechanism 15 in FIG. 1). When the heat source-side heat exchanger 23 functions as a refrigerant evaporator and the utilization-side heat exchangers (heat exchangers) 30a, 30b, and 30c function as refrigerant radiators (in the heating operation state), the switching mechanism 15 connects the suction side of the compressor 25 to the gas side of the heat source-side heat exchanger 23 (see the broken line of the switching mechanism 15 in FIG. 1). Note that the switching mechanism 15 may be implemented without using the four-way switching valve. For example, the switching mechanism 15 may be configured by combining a plurality of electromagnetic valves and pipes so as to implement switching of the refrigerant flow direction as described above.

[0040] The heat source-side heat exchanger 23 is a heat exchanger that functions as a refrigerant radiator or functions as a refrigerant evaporator. The heat source-side heat exchanger 23 is, but is not limited to, a fin-and-tube heat exchanger including a plurality of heat transfer tubes and a plurality of heat transfer fins, for example. Here, the heat source-side unit 2 includes a heat source-side fan 24. The heat source-side fan 24 sucks outdoor air into the heat source-side unit 2, causes the sucked outdoor air to exchange heat with the refrigerant in the heat source-side heat exchanger 23, and discharges the air to the outside. The heat source-side fan 24 is driven by a heat source-side fan motor. The heat source-side fan 24 is, for example, an inverter-controlled fan. However, the heat source-side fan 24 may be a constant speed fan.

[0041] In the cooling operation, the air conditioning apparatus 1 of the air conditioning system 100 causes the refrigerant to flow from the heat source-side heat exchanger 23 to the utilization-side heat exchangers (heat exchangers) 30a, 30b, and 30c, each functioning as a refrigerant evaporator, through the first connection flow path 21. In the heating operation, the air conditioning apparatus 1 causes the refrigerant to flow from the compressor 25 to the utilization-side heat exchangers (heat exchangers) 30a, 30b, and 30c, each functioning as a refrigerant radiator, through the second connection flow path 22. In the cooling operation, the switching mechanism 15 switches to the cooling operation state, the heat source-side heat exchanger 23 functions as a refrigerant radiator, and the refrigerant flows from the heat source-side unit 2 side to the utilization-side units 3a, 3b, and 3c side through the first connection flow path 21. In the heating operation, the switching mechanism 15 switches to the heating operation state, the refrigerant flows from the utilization-side units 3a, 3b, and 3c side to the heat source-side unit 2 side through the first connection flow path 21, and the heat source-side heat exchanger 23 functions as a refrigerant evaporator.

[0042] Here, the heat source-side liquid refrigerant pipe 38 is provided with the heat source-side expansion valve 26. The heat source-side expansion valve 26 is an electrically powered expansion valve configured to decompress the refrigerant in the heating operation, and is provided at a portion near the liquid side end of the heat source-side heat exchanger 23 in the heat source-side liquid refrigerant pipe 38. Note that the heat source-side expansion valve 26 is not limited to the electrically powered expansion valve, and may be another type of expansion valve such as a temperature automatic expansion valve.

[0043] The heat source-side unit 2 is provided with various sensors, although illustration is omitted. The sensors provided in the heat source-side unit 2 include, but are not limited to, a temperature sensor and a pressure sensor placed in the suction pipe 31 and the discharge pipe 32, a temperature sensor placed in the heat source-side heat exchanger 23 and the heat source-side liquid refrigerant pipe 38, a temperature sensor for measuring the temperature of heat source air, and the like. However, the heat source-side unit 2 does not have to include all of these sensors.

(2-4) Control unit

[0044] The control unit 19 is configured by connecting a heat source-side control unit 92 to the utilization-side control units 93a, 93b, and 93c via a transmission line 90, as shown in FIG. 2. The heat source-side control unit 92 controls constituent devices of the heat source-side unit 2. The utilization-side control units 93a, 93b, and 93c control constituent devices of the utilization-side units 3a, 3b, and 3c, the first shutoff valves 71a, 71b, and 71c, and the second shutoff valves 72a, 72b, and 72c, respectively. The heat source-side control unit 92 included in the heat source-side unit 2, and the utilization-side control units 93a, 93b, and 93c included in the utilization-side units 3a, 3b, and 3c exchange information such as control signals with one another via the transmission line 90.

[0045] The heat source-side control unit 92 includes a control board on which electrical components such as a microcomputer and a memory are mounted, and is connected to, for example, various constituent devices 15, 17a, 17b, 23, 24, 25, 26 of the heat source-side unit 2, various sensors (not shown), and the like. The utilization-side control units 93a, 93b, and 93c each include a control board on which electrical components such as a microcomputer and a memory are mounted, and for example, various constituent devices 30a, 30b, 30c, 34a, 34b, 34c, 36a, 36b, 36c of the utilization-side units 3a, 3b, and 3c, various shutoff valves 71a, 71b, 71c, 72a, 72b, and 72c, refrigerant leakage sensors 50a, 50b, and 50c, various sensors (not shown), and the like are connected.

[0046] In this way, the control unit 19 controls the operation of the entire air conditioning apparatus 1. Specifically, based on detection signals of various sensors (not shown) as described above, the refrigerant leakage sensors 50a, 50b, and 50c, and the like, the control unit 19 controls various constituent devices 15, 17a, 17b, 23, 24, 25, 26, 30a, 30b, 30c, 34a, 34b, 34c, 36a, 36b, 36c, 71a, 71b, 71c, 72a, 72b, and 72c of the air conditioning apparatus 1.

(3) Operation of air conditioning apparatus when refrigerant leaks

[0047] Next, the operation of the air conditioning apparatus 1 when a refrigerant leaks will be described with reference to FIG. 3. In a similar manner to the basic operation described above, the operation of the air conditioning apparatus 1 described below when a refrigerant leaks is performed by the control unit 19 that controls the constituent devices of the air conditioning apparatus 1.

[0048] Since similar control is performed even if the refrigerant leaks in any of the first parts 11a, 11b, and 11c, the case where the refrigerant leakage is detected in the first part 11a will be described here as an example.

[0049] In step S1 of FIG. 3, it is determined whether any of the refrigerant leakage sensors 50a, 50b, and 50c of the utilization-side units 3a, 3b, and 3c has detected a refrigerant leakage. Here, when the refrigerant leakage sensor 50a of the utilization-side unit 3a detects the refrigerant leakage in the first part 11a, the process proceeds to next step S2.

[0050] In step S2, in the first part 11a where the refrigerant leaks, an alarm is issued to a person in the space where the utilization-side unit 3a is installed (air conditioning target space) by using an alarm device (not shown) that issues an alarm with an alarm sound such as a buzzer and turns on light.

[0051] Next, in step S3, the first shutoff valve 71a and the second shutoff valve 72a, which are shutoff valves corresponding to the first part 11a where the refrigerant leaks, are closed. Accordingly, the upstream side and the downstream side of the first shutoff valve 71a and the second shutoff valve 72a are separated from each other, and the refrigerant flow between the first part 11a and the second part 12 discontinues. As a result, the inflow of refrigerant from the second part 12 or the first parts 11b and 11c to the first part 11a discontinues.

(4) Method of determining position to place refrigerant shutoff valve

[0052] (4-1)
If the refrigerant leaks in the first part 11a, all the refrigerant filled in the refrigerant circuit 10 may leak to the air conditioning target space. Therefore, when the refrigerant leakage sensor 50a detects the refrigerant leakage, the control unit 19 shuts off the first shutoff valve 71a and the second shutoff valve 72a. Since the refrigerant flow between the first part 11a and the second part 12 is shut off accordingly, all the refrigerant filled in the refrigerant circuit 10 is prevented from leaking to the air conditioning target space. In this case, the total amount of refrigerant contained in the first part 11a is the total amount of refrigerant considered to leak to the air conditioning target space. The maximum value of the total amount of refrigerant contained in the first part 11a can be calculated from the volume of the utilization-side refrigerant flow path 13a, the volume of the utilization-side first connection flow path 21aa, and the volume of the utilization-side second connection flow path 22aa. As the volume of the utilization-side refrigerant flow path 13a, the volume of the utilization-side first connection flow path 21aa, and the volume of the utilization-side second connection flow path 22aa increase, the maximum value of the total amount of refrigerant contained in the first part 11a increases.

[0053] If the amount of refrigerant contained in the first part 11a is large and the volume of the air conditioning target space is small, the refrigerant concentration of the refrigerant leaked to the air conditioning target space may be large. In other words, if the volume of the utilization-side refrigerant flow path 13a, the volume of the utilization-side first connection flow path 21aa, and the volume of the utilization-side second connection flow path 22aa are large, and if the volume of the air conditioning target space is small, the refrigerant concentration of the refrigerant R32 near the floor of the air conditioning target space may become large and exceed the LFL/safety factor. Note that the lower flammability limit (LFL) is minimum refrigerant concentration specified by ISO 817 and enabling flame propagation in a state where a refrigerant and air are mixed uniformly. Therefore, the first shutoff valve 71a and the second shutoff valve 72a need to be placed at positions where there is no risk of exceeding the LFL/safety factor of the air conditioning target space even if all the refrigerant present in the first part 11a leaks to the air conditioning target space.

(4-2) Second range

[0054] The refrigerant circuit 10 of the air conditioning apparatus 1 is divided by the first shutoff valve 71a and the second shutoff valve 72a into the first part 11a and the second part 12. The first part 11a includes the utilization-side refrigerant flow path 13a, the utilization-side first connection flow path 21aa, and the utilization-side second connection flow path 22aa. The total amount of refrigerant contained in the first part 11a is the total amount of refrigerant that is considered to leak to the air conditioning target space. The maximum value of the total amount of refrigerant contained in the first part 11a can be calculated from the volume of the utilization-side refrigerant flow path 13a, the volume of the utilization-side first connection flow path 21aa, and the volume of the utilization-side second connection flow path 22aa. In other words, the maximum value of the total amount of refrigerant contained in the first part 11a changes depending on the positions where the first shutoff valve 71a and the second shutoff valve 72a are placed in the refrigerant circuit 10. For example, when the first shutoff valve 71a and the second shutoff valve 72a are placed away from the position of the utilization-side unit 3a in the refrigerant circuit 10, the volume of the utilization-side first connection flow path 21aa and the volume of the utilization-side second connection flow path 22aa are large, and therefore the maximum value of the total amount of refrigerant contained in the first part 11a is large.

[0055] If a refrigerant leakage occurs in the first part 11a, the refrigerant concentration of the refrigerant leaked to the air conditioning target space changes depending on the positions where the first shutoff valve 71a and the second shutoff valve 72a are placed in the refrigerant circuit 10. In the present disclosure, the first shutoff valve 71a and the second shutoff valve 72a are placed at positions where the refrigerant concentration in the air conditioning target space is within the second range when it is assumed that all the refrigerant present in the first part 11a at a predetermined temperature, a predetermined pressure, and a predetermined phase state leaks to the air conditioning target space. The second range is a range of refrigerant concentration in which it is considered that the occurrence of combustion accident caused by the refrigerant leakage in the air conditioning target space can be inhibited. The second range is from LFL/Y1 to LFL/Y2. Y1 and Y2 are safety factors. When the second range is B, the second range is, but is not limited to, LFL/100 < B < LFL/1, for example. Even if the refrigerant leakage occurs in the first part 11a and the refrigerant leaks to the air conditioning target space, the occurrence of combustion accident is inhibited when the refrigerant concentration in the air conditioning target space is within the second range.

(4-3) First range

[0056] As described above, if the refrigerant leakage occurs in the first part 11a, after the refrigerant leakage sensor 50a detects the refrigerant leakage, the control unit 19 causes the first shutoff valve 71a and the second shutoff valve 72a to shut off the flow of refrigerant between the first part 11a and the second part 12. In other words, only after the refrigerant leakage sensor 50a detects the refrigerant leakage, the control unit 19 can cause the first shutoff valve 71a and the second shutoff valve 72a to shut off the flow of refrigerant between the first part 11a and the second part 12.

[0057] Therefore, if the refrigerant concentration that can be detected by the refrigerant leakage sensor 50a is larger than concentration in the second range, it is considered that an amount of refrigerant exceeding the second range leaks from the first part 11a to the air conditioning target space before the first shutoff valve 71a and the second shutoff valve 72a shut off the flow between the first part 11a and the second part 12.

[0058] In view of the above-described circumstances, the refrigerant leakage sensor 50a is configured to detect the refrigerant having refrigerant concentration in the first range smaller than the refrigerant concentration in the second range. The first range is from LFL/X1 to LFL/X2. X1 and X2 are safety factors. When the first range is A, the first range is, but is not limited to, LFL/100 ≤ A ≤ LFL/4, for example.

[0059] In general, combustion accidents in the air conditioning target space caused by a refrigerant leakage occur because a large amount of refrigerant that exceeds the lower limit concentration of combustion in the air conditioning target space leaks to the air conditioning target space. The refrigerant leakage sensor 50a in the present disclosure can detect the refrigerant having refrigerant concentration within the first range. The refrigerant concentration of the refrigerant in the first range is smaller than the refrigerant concentration of the refrigerant in the second range. In other words, the refrigerant leakage sensor 50a can detect even a refrigerant having small (thin) refrigerant concentration. This allows the control unit 19 to control the first shutoff valve 71a and the second shutoff valve 72a such that the refrigerant concentration in the air conditioning target space is within the second range after the refrigerant leakage sensor 50a detects the refrigerant leakage.

(4-4) Relationship between first range and second range

[0060] As described above, the second range is a range of refrigerant concentration in which it is considered that the occurrence of combustion accident caused by the refrigerant leakage in the air conditioning target space can be inhibited. As described above, if the refrigerant leakage sensor 50a cannot detect the refrigerant having refrigerant concentration in the second range, the refrigerant exceeding the second range may leak to the air conditioning target space.

[0061] Therefore, in the present disclosure, it is determined that X1 for the first range is larger than Y1 for the second range, and that X2 for the first range is larger than Y2 for the second range. In other words, the numerical value to be substituted for X1 for the first range is larger than the numerical value to be substituted for Y1 for the second range, and the numerical value to be substituted for X2 for the first range is larger than the numerical value to be substituted for Y2 for the second range. For example, if the safety factor X1 for the first range is 50 and the safety factor X2 is 4, the safety factor Y1 for the second range is, for example, 49, and the safety factor Y2 is, for example, 1. In this way, the refrigerant concentration in the first range is definitely smaller than the refrigerant concentration in the second range, and the refrigerant leakage sensor 50a can detect the refrigerant leakage before the amount of refrigerant exceeding the second range leaks to the air conditioning target space.

[0062] X1 being larger than Y1 and X2 being larger than Y2 mean that, in other words, LFL/Y1 is refrigerant concentration larger than LFL/X1, and LFL/Y2 is refrigerant concentration larger than LFL/X2. In other words again, this means that LFL/Y1 is darker in refrigerant concentration than LFL/X1, and LFL/Y2 is darker in refrigerant concentration than LFL/X2. Therefore, if the first range is A and the second range is B, it can be said that the first range and the second range are ranges that satisfy the following formulas.

[0063] When A and B satisfy Formulas 1 and 2, the refrigerant leakage sensor 50a can detect the refrigerant in the second range.

(4-5) Method of determining position to place refrigerant shutoff valve

[0064] According to what has been described above, one example of the method of determining the position to place the first shutoff valve 71a and the second shutoff valve 72a in the refrigerant circuit 10 will be described. Although not restrictive, to begin with, the second range is determined, which is a range of refrigerant concentration in which it is considered to be possible to inhibit the occurrence of combustion accident caused by a refrigerant leakage in the air conditioning target space when the refrigerant leakage occurs from the first part 11a. Next, the first range, which is a range of refrigerant concentration that can be detected by the refrigerant leakage sensor 50a, is determined. At this time, in order to allow the refrigerant leakage sensor 50a to reliably detect the refrigerant having refrigerant concentration in the second range, the refrigerant concentration in the first range is set smaller than the refrigerant concentration in the second range. Finally, the first shutoff valve 71a and the second shutoff valve 72a are placed at positions where the refrigerant leaked to the air conditioning target space is within the second range even if the refrigerant leakage occurs in the first part 11a. As the positions where the first shutoff valve 71a and the second shutoff valve 72a are placed move away from the utilization-side unit 3a, the volume of the utilization-side first connection flow path 21aa and the volume of the utilization-side second connection flow path 22aa will increase, and therefore an amount of refrigerant that can exceed the second range may be contained in the first part 11a. Therefore, the first shutoff valve 71a and the second shutoff valve 72a are placed based on the volume of the utilization-side refrigerant flow path 13a, the volume of the utilization-side first connection flow path 21aa, the volume of the utilization-side second connection flow path 22aa, and the volume of the air conditioning target space. In this way, the positions to place the first shutoff valve 71a and the second shutoff valve 72a in the refrigerant circuit 10 are determined.

[0065] The method of determining the positions to place the first shutoff valve 71a and the second shutoff valve 72a in the refrigerant circuit 10 is not limited to the above method, and the first range may be determined first. For example, as the refrigerant leakage sensor 50a, the refrigerant leakage sensor 50a capable of detecting certain concentration in the first range is determined. Next, the second range is determined such that the refrigerant concentration in the second range is larger (higher) than the refrigerant concentration in the first range. This allows the refrigerant leakage sensor 50a to detect a refrigerant smaller (thinner) than the second range. Finally, the first shutoff valve 71a and the second shutoff valve 72a are placed at positions where the refrigerant leaked to the air conditioning target space is within the second range even if the refrigerant leakage occurs in the first part 11a. The upper limit of the second range is a value smaller than LFL/1.

(5) Features

[0066] (5-1)
The air conditioning system 100 of the first aspect includes the refrigerant circuit 10, the heat exchangers 30a, 30b, and 30c, the shutoff valve 70, and the refrigerant leakage sensors 50a, 50b, and 50c. The refrigerant circuit 10 includes the first parts 11a, 11b, and 11c and the second part 12. The heat exchangers 30a, 30b, and 30c are provided in the first parts 11a, 11b, and 11c, respectively, and cool or heat the air in the air conditioning target space by exchanging heat between the refrigerant and the air in the air conditioning target space. The shutoff valve 70 is provided in the refrigerant circuit 10 and shuts off communication between the first parts 11a, 11b, and 11c and the second part 12. The refrigerant leakage sensors 50a, 50b, and 50c detect the refrigerant leaked from the first parts 11a, 11b, and 11c, respectively. The refrigerant leakage sensors 50a, 50b, and 50c detect that the refrigerant concentration is within the first range. The shutoff valve 70 is placed such that the refrigerant concentration in the air conditioning target space is within the second range, which is a range larger than the first range, when it is assumed that all the refrigerant present in the first parts 11a, 11b, and 11c has leaked to the air conditioning target space.

[0067] In the air conditioning system 100 of the first aspect, the shutoff valve 70 is placed at a position where the refrigerant concentration in the air conditioning target space is within the second range, for example, even if all the refrigerant present in the first part 11a leaks to the air conditioning target space. This inhibits the refrigerant concentration in the air conditioning target space from exceeding LFL.

[0068] Furthermore, in the air conditioning system 100 of the first aspect, the refrigerant concentration in the second range is larger than the refrigerant concentration in the first range. Accordingly, for example, if a refrigerant leakage occurs in the first part 11a, an amount of refrigerant exceeding the LFL/safety factor in the air conditioning target space is inhibited from leaking from the first part 11a before the shutoff valve 70 shuts off the flow between the first part 11a and the second part 12.

[0069] (5-2)
The air conditioning system 100 of the second aspect is the air conditioning system 100 of the first aspect, in which when the lower limit concentration of refrigerant combustion is LFL (Lower Flammability Limit) [kg/m³], the first range is from LFL/X1 to LFL/X2 and the second range is from LFL/Y1 to LFL/Y2. X1 is larger than Y1, and X2 is larger than Y2.

[0070] The air conditioning system 100 of the second aspect sets the first range and the second range such that the refrigerant concentration is smaller than LFL in the air conditioning target space. This inhibits the refrigerant concentration in the air conditioning target space from exceeding LFL.

[0071] Note that X1 being larger than Y1 and X2 being larger than Y2 mean that, in other words, LFL/Y1 is larger than LFL/X1, and LFL/Y2 is larger than LFL/X2.

[0072] Note that the first range being from LFL/X1 to LFL/X2 means that, in other words, if the first range is A, LFL/X1 ≤ A ≤ LFL/X2.

[0073] Note that the second range being from LFL/Y1 to LFL/Y2 means that, in other words, if the second range is B, LFL/Y1 < B < LFL/Y2.

[0074] (5-3)
The air conditioning system 100 of the third aspect is the air conditioning system 100 of the first aspect or the second aspect, in which the refrigerant circuit 10 includes the utilization-side refrigerant flow paths 13a, 13b, and 13c, which are part of the first parts 11a, 11b, and 11c, the heat source-side refrigerant flow path 14, which is part of the second part 12, and the first connection flow path 21 and the second connection flow path 22 connecting the utilization-side refrigerant flow paths 13a, 13b, and 13c to the heat source-side refrigerant flow path 14. The shutoff valve 70 includes the first shutoff valves 71a, 71b, and 71c provided in the first connection flow path 21 and the second shutoff valves 72a, 72b, and 72c provided in the second connection flow path 22. The first connection flow path 21 includes the utilization-side first connection flow paths 21aa, 21ab, and 21ac between the utilization-side refrigerant flow paths 13a, 13b, and 13c and the first shutoff valves 71a, 71b, and 71c, and the heat source-side first connection flow path 21b between the heat source-side refrigerant flow path 14 and the first shutoff valves 71a, 71b, and 71c. The second connection flow path 22 includes the utilization-side second connection flow paths 22aa, 22ab, and 22ac between the utilization-side refrigerant flow paths 13a, 13b, and 13c and the second shutoff valves 72a, 72b, and 72c, and the heat source-side second connection flow path 22b between the heat source-side refrigerant flow path 14 and the second shutoff valves 72a, 72b, and 72c. The first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c are placed based on the volume of the utilization-side refrigerant flow paths 13a, 13b, and 13c, the volume of the utilization-side first connection flow paths 21aa, 21ab, and 21ac, the volume of the utilization-side second connection flow paths 22aa, 22ab, and 22ac, and the volume of the air conditioning target space.

[0075] In the air conditioning system 100 of the third aspect, the first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c are placed based on the volume of the utilization-side refrigerant flow paths 13a, 13b, and 13c, the volume of the utilization-side first connection flow paths 21aa, 21ab, and 21ac, the volume of the utilization-side second connection flow paths 22aa, 22ab, and 22ac, and the volume of the air conditioning target space. This inhibits the refrigerant concentration in the air conditioning target space from exceeding LFL.

[0076] (5-4)
The air conditioning system 100 of the fourth aspect is the air conditioning system 100 of the first aspect, in which when the lower limit concentration of refrigerant combustion is LFL [kg/m³], the first range is from LFL/X1 to LFL/X2 and the second range is from LFL/Y1 to LFL/Y2. LFL/Y1 is larger than LFL/X1, and LFL/Y2 is larger than LFL/X2.

[0077] The air conditioning system 100 of the fourth aspect sets the first range and the second range such that the refrigerant concentration is smaller than LFL in the air conditioning target space. This inhibits the refrigerant concentration in the air conditioning target space from exceeding LFL.

[0078] Note that the first range being from LFL/X1 to LFL/X2 means that, in other words, if the first range is A, LFL/X1 ≤ A ≤ LFL/X2.

[0079] The second range being from LFL/Y1 to LFL/Y2 means that, in other words, if the second range is B, LFL/Y1 < B < LFL/Y2.

(6) Modifications

[0080] The above-described embodiment can be appropriately modified as shown in the following modifications. Each modification may be applied in combination with other modifications insofar as no inconsistency arises. Note that constituent elements similar to those described in the first embodiment are denoted with similar reference signs, and the detailed description thereof will be omitted.

(6-1) Modification A

[0081] The above-described embodiment has described an example in which the first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c are placed in the refrigerant circuit 10 so as to correspond to the utilization-side units 3a, 3b, and 3c, respectively. However, if the above-described shutoff valves are placed at positions where the refrigerant concentration in the air conditioning target space is within the second range when it is assumed that all the refrigerant present in a first part 11A at a predetermined temperature, predetermined pressure, and predetermined phase state has leaked to the air conditioning target space, as shown in FIG. 4, one first shutoff valve 71A and one second shutoff valve 72A may be connected to each of the plurality of utilization-side units 3a, 3b, and 3c.

[0082] In this case, as shown in FIG. 4, the first part 11A includes the utilization-side refrigerant flow path 13a, the utilization-side refrigerant flow path 13b, the utilization-side refrigerant flow path 13c, the utilization-side liquid refrigerant pipe 37a, the utilization-side liquid refrigerant pipe 37b, the utilization-side liquid refrigerant pipe 37c, a utilization-side first connection flow path 21A, and a utilization-side second connection flow path 22A. The first connection flow path 21 includes the utilization-side first connection flow path 21A and the heat source-side first connection flow path 21b. The second connection flow path 22 includes the utilization-side second connection flow path 22A and the heat source-side second connection flow path 22b. Note that the configuration of the first shutoff valve 71A and the second shutoff valve 72A is similar to the configuration of the first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c, and thus the description thereof will be omitted.

[0083] Note that in FIG. 4, the utilization-side control unit 93a is connected to the first shutoff valve 71A and the second shutoff valve 72A, but this is not restrictive. The utilization-side control unit 93b or the utilization-side control unit 93c may be connected to the first shutoff valve 71A and the second shutoff valve 72A.

[0084] FIG. 4 illustrates the utilization-side units 3a, 3b, and 3c, but the number of utilization-side units is not limited to this example, and may be three or less, or three or more.

(6-2) Modification B

[0085] The above-described embodiment has described an example in which the first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c are placed corresponding to the three utilization-side units 3a, 3b, and 3c. However, the number of utilization-side units is not limited to three, and the number of first shutoff valves and the second shutoff valves is not limited to three. For example, as shown in FIG. 5, one utilization-side unit 3S may be connected to the heat source-side unit 2 by the first connection flow path 21 and the second connection flow path 22 via one first shutoff valve 71S and one second shutoff valve 72S.

[0086] In this case, as shown in FIG. 5, a first part 11S includes a utilization-side refrigerant flow path 13S, a utilization-side liquid refrigerant pipe 37S, a utilization-side first connection flow path 21S, and a utilization-side second connection flow path 22S. The first connection flow path 21 includes the utilization-side first connection flow path 21S and the heat source-side first connection flow path 21b. The second connection flow path 22 includes the utilization-side second connection flow path 22S and the heat source-side second connection flow path 22b.

[0087] Note that the configuration of constituent devices 30S, 34S, 36S, 37S, 50S, and 92S of the utilization-side unit 3S is similar to the configuration of various constituent devices 30a, 30b, 30c, 34a, 34b, 34c, 36a, 36b, 36c, 37a, 37b, 37c, 50a, 50b, 50c, 92a, 92b, and 92c of the utilization-side units 3a, 3b, and 3c, and thus the description thereof will be omitted. The configuration of the utilization-side refrigerant flow path 13 S is similar to the configuration of the utilization-side refrigerant flow paths 13a, 13b, and 13c, and thus the description thereof will be omitted.

(6-3) Modification C

[0088] The above-described embodiment has described that the utilization-side control units 93a, 93b, and 93c control the first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c, respectively. However, the heat source-side control unit 92 may control the first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c.

(6-4) Modification D

[0089] The above-described embodiment has described that the control unit 19 is configured by connecting the heat source-side control unit 92 to the utilization-side control units 93a, 93b, and 93c via the transmission line 90. However, the heat source-side control unit 92 or the utilization-side control units 93a, 93b, and 93c may control the operation of the entire air conditioning apparatus 1. For example, the heat source-side control unit 92 may control various constituent devices 15, 17a, 17b, 23, 24, 25, 26, 30a, 30b, 30c, 34a, 34b, 34c, 36a, 36b, 36c, 71a, 71b, 71c, 72a, 72b, and 72c of the air conditioning apparatus 1 based on detection signals of various sensors (not shown), the refrigerant leakage sensors 50a, 50b, and 50c, and the like.

(6-5) Modification E

[0090] The above-described embodiment has described an example in which the first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c are placed outside the utilization-side units 3a, 3b, and 3c and the heat source-side unit 2. However, as shown in FIG. 6, the utilization-side unit 3a may include the first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c inside the utilization-side units 3a, 3b, and 3c, by placement inside the casing of the utilization-side units 3a, 3b, and 3c. The first shutoff valves 71a, 71b, and 71c and the second shutoff valves 72a, 72b, and 72c placed inside the casing may be controlled by, for example, the utilization-side control units 93a, 93b, and 93c, although not restrictive.

<Supplementary note>

[0091] The embodiment of the present disclosure has been described above. It will be understood that various changes to modes and details can be made without departing from the spirit and scope of the present disclosure recited in the claims.

REFERENCE SIGNS LIST

[0092] 

10: refrigerant circuit

11a, 11b, 11c, 11A, 11S: first part

12: second part

13a, 13b, 13c, 13S: utilization-side refrigerant flow path

14: heat source-side refrigerant flow path

21: first connection flow path

22: second connection flow path

21aa, 21ab, 21ac, 21A, 21S: utilization-side first connection flow path

21b: heat source-side first connection flow path

22aa, 22ab, 22ac, 21A, 21S: utilization-side second connection flow path

22b: heat source-side second connection flow path

30a, 30b, 30c, 30S: heat exchanger

50a, 50b, 50c, 50S: refrigerant leakage sensor

70: shutoff valve (first shutoff valve, second shutoff valve)

71a, 71b, 71c, 71A, 71S: first shutoff valve

72a, 72b, 72c, 72A, 72S: second shutoff valve

100: air conditioning system

CITATION LIST

PATENT LITERATURE

[0093] Patent Literature 1: Japanese Laid-Open Patent Publication No. 2019-45129

Claims

1. An air conditioning system (100) comprising:

a refrigerant circuit (10) including a first part (11a, 11b, 11c, 11A, 11S) and a second part (12);

a heat exchanger (30a, 30b, 30c, 30S) provided in the first part and configured to cool or heat air in an air conditioning target space by exchanging heat between a refrigerant and the air in the air conditioning target space;

a shutoff valve (70) provided in the refrigerant circuit and configured to shut off communication between the first part and the second part; and

a refrigerant leakage sensor (50a, 50b, 50c, 50S) configured to detect the refrigerant leaked from the first part,

wherein

the refrigerant leakage sensor detects that refrigerant concentration is within a first range, and

the shutoff valve is placed to set the refrigerant concentration in the air conditioning target space within a second range that is a range larger than the first range when it is assumed that all the refrigerant present in the first part has leaked to the air conditioning target space.

2. The air conditioning system according to claim 1, wherein

when a lower limit concentration of combustion of the refrigerant is LFL [kg/m³], the first range is from LFL/X1 to LFL/X2,

the second range is from LFL/Y1 to LFL/Y2, and

X1 is larger than Y1, and X2 is larger than Y2.

3. The air conditioning system according to claim 1 or 2, wherein

the refrigerant circuit includes a utilization-side refrigerant flow path (13a, 13b, 13c, 13S) that is part of the first part, a heat source-side refrigerant flow path (14) that is part of the second part, and a first connection flow path (21) and a second connection flow path (22) connecting the utilization-side refrigerant flow path to the heat source-side refrigerant flow path,

the shutoff valve includes a first shutoff valve (71a, 71b, 71c, 71A, 71S) provided in the first connection flow path and a second shutoff valve (72a, 72b, 72c, 72A, 72S) provided in the second connection flow path,

the first connection flow path includes a utilization-side first connection flow path (21aa, 21ab, 21ac) between the utilization-side refrigerant flow path and the first shutoff valve, and a heat source-side first connection flow path (21b) between the heat source-side refrigerant flow path and the first shutoff valve,

the second connection flow path includes a utilization-side second connection flow path (22aa, 22ab, 22ac) between the utilization-side refrigerant flow path and the second shutoff valve, and a heat source-side second connection flow path (22b) between the heat source-side refrigerant flow path and the second shutoff valve, and

the first shutoff valve and the second shutoff valve are placed based on volume of the utilization-side refrigerant flow path, volume of the utilization-side first connection flow path, volume of the utilization-side second connection flow path, and volume of the air conditioning target space.

Drawing