Refrigerant circulation device

Abstract

If the specifications of the shut-off valve in the refrigerant circulation device are too high, it will lead to an increase in manufacturing costs. The air conditioning unit (1) is a device that circulates flammable refrigerant in the refrigerant circuit (10), including a liquid-side shut-off valve (71a) and a gas-side shut-off valve (68a). Both the liquid-side and gas-side shut-off valves are set to a shut-off state when a refrigerant leak is detected, thereby suppressing refrigerant leakage into a designated space. Regarding the air leakage of the liquid-side shut-off valve (71a) and the gas-side shut-off valve (68a) in the shut-off state, when the fluid is air at 20°C and the pressure difference before and after is 1 MPa, i.e., the leakage during shut-off, the leakage during shut-off of the liquid-side shut-off valve is less than 300 × R (cm). 3 / min), the leakage rate of the gas-side shut-off valve is greater than 300×R(cm) when the flow is interrupted. 3 / min). Where R=(ρ md ×V md ×A d ) / (C r ×(2×ΔP r / ρ 1r ) 0.5 ×A v ×ρ 1rl +A v ×(2 / (λ+1)) ((λ+1) / 2(λ‑1)) ×(λ×P 1r ×ρ 1rg ) 0.5 Alternatively, R = 1, where R is determined based on at least one of the permissible average concentration, leakage height, and type of refrigerant.

Description

Technical Field

[0001] This disclosure relates to a refrigerant circulation device. Background Technology

[0002] The Japan Refrigeration and Air Conditioning Manufacturers Association's guideline, "Guidelines for Facilities to Ensure Safety in the Event of Refrigerant Leakage in Commercial Air Conditioners Using Slightly Flammable (A2L) Refrigerants" (JRA GL-16:2017), issued on September 1, 2017, specifies the "Specifications for Safety Shut-off Valves" in Appendix A (Specifications), which must be met. One of the specifications for the aforementioned safety shut-off valve is the leakage rate when the valve is closed. Specifically, when the fluid is air and the pressure difference across the safety shut-off valve is 1 MPa, the leakage rate should be 300 (cm³). 3 The following values ​​( / min) are specified as the leakage rate that a safety shut-off valve should meet when the valve is closed. Summary of the Invention The technical problem that the invention aims to solve

[0003] The aforementioned guidelines stipulate that when a safety shut-off valve is used as a safety measure, it must be positioned appropriately within the refrigerant circuit to be shut off, ensuring that the maximum refrigerant concentration in the target living room (room) during a leak is below one-quarter of the LFL value. Furthermore, the guidelines specify that the refrigerant circuit must be shut off based on the signal from a detector used to detect refrigerant leaks.

[0004] A safety shut-off valve is a valve that cuts off the flow of refrigerant leaking from the refrigerant circuit to the refrigerant leak space when refrigerant leaks. The lower flammability limit (LFL) is the minimum concentration of refrigerant that can propagate a flame when the refrigerant and air are uniformly mixed, as specified in ISO 817. The maximum concentration of refrigerant during a leak is obtained by dividing the total amount of refrigerant in the refrigerant circuit by the volume of the space where the refrigerant is trapped (the value obtained by multiplying the floor area by the leak height).

[0005] The aforementioned guidelines require that, regardless of whether the safety shut-off valve is a gas-side safety shut-off valve (hereinafter referred to as a gas-side shut-off valve) or a liquid-side safety shut-off valve (hereinafter referred to as a liquid-side shut-off valve), leakage when the valve is closed must be suppressed to a minimum. Generally, when the diameter of the gas refrigerant connection pipe is larger than that of the liquid refrigerant connection pipe, and the gas-side shut-off valve has a larger diameter and the sealing clearance is constant, the larger perimeter of the sealing part results in a larger clearance area. Therefore, under the same air pressure difference, the leakage of the gas-side shut-off valve is often greater when closed compared to the liquid-side shut-off valve. To meet the requirements of the aforementioned guidelines, the valve clearance of the gas-side shut-off valve needs to be reduced; therefore, this presents a technical problem of increased manufacturing or purchase costs for the gas-side shut-off valve. Technical solutions adopted to solve technical problems

[0006] The refrigerant circulation device of the first aspect of this disclosure is a refrigerant circulation device that circulates a flammable refrigerant in a refrigerant circuit. The refrigerant circulation device includes a gas-side shut-off valve and a liquid-side shut-off valve, a detection unit, and a control unit. The gas-side shut-off valve and the liquid-side shut-off valve are located on opposite sides of a first section of the refrigerant circuit. The detection unit detects refrigerant leakage from the first section to a designated space. When the detection unit detects refrigerant leakage from the first section to the designated space, the control unit sets the gas-side shut-off valve and the liquid-side shut-off valve to a shut-off state. The leakage rate of the gas-side shut-off valve and the liquid-side shut-off valve during shut-off is the leakage rate of the gas-side shut-off valve and the liquid-side shut-off valve in a single-phase gas phase under standard conditions when the pressure difference before and after the shut-off state is a designated pressure. The leakage rate of the gas-side shut-off valve during shut-off is greater than that of the liquid-side shut-off valve during shut-off. Furthermore, the leakage rate during shut-off has the same meaning as the leakage rate when the valve is closed as described in the aforementioned guidelines.

[0007] In a refrigerant circulation system, the gas-side shut-off valve and the liquid-side shut-off valve are used to shut off the refrigerant, which has a different density. The gas-side shut-off valve shuts off the gaseous refrigerant, while the liquid-side shut-off valve shuts off the liquid refrigerant. Therefore, if the leakage rate of the liquid-side shut-off valve during shut-off is reduced in advance, even if the leakage rate of the gas-side shut-off valve during shut-off is slightly increased, the total amount of refrigerant leaking from the first section into the designated space can be suppressed to a predetermined amount. Therefore, in the refrigerant circulation system of the first viewpoint, the leakage rate of the gas-side shut-off valve during shut-off is increased to be greater than that of the liquid-side shut-off valve. This reduces the manufacturing or purchase cost of the gas-side shut-off valve.

[0008] The refrigerant circulation device of the second aspect of this disclosure is the refrigerant circulation device of the first aspect. The leakage rate during flow interruption is the air leakage rate at a temperature of 20°C and a specified pressure of 1 MPa. The leakage rate of the gas-side flow interruption valve during flow interruption is greater than 300 × R (cm). 3 / min). The leakage rate of the liquid-side shut-off valve during shut-off is less than 300×R (cm). 3 / min).

[0009] The refrigerant circulation device of the third aspect of this disclosure is the refrigerant circulation device of the first aspect. The leakage rate when the gas-side shut-off valve is interrupted is 300 × R (cm). 3 The leakage rate is less than 1.0 to 2.7 times that of the liquid-side shut-off valve when the flow is interrupted. The leakage rate is 300 × R (cm³). 3 The value is less than 0.94 times that of ( / min).

[0010] This structure ensures safety in case of refrigerant leakage and reduces the manufacturing or purchase cost of the gas-side shut-off valve.

[0011] The refrigerant circulation device of the fourth aspect of this disclosure is the refrigerant circulation device of the first aspect. When the gas-side shut-off valve is shut off, the leakage is within 300 × R (cm). 3 The leakage rate is in the range of 1.6 to 2.7 times that of the flow rate of the liquid-side shut-off valve during shut-off. The leakage rate is within 300 × R (cm³) when the flow is interrupted. 3 The range is 0.37 to 0.94 times that of ( / min).

[0012] This structure ensures safety in case of refrigerant leakage and reduces the manufacturing or purchase cost of the gas-side shut-off valve.

[0013] Based on the refrigerant circulation device of any of the second to fourth viewpoints, in the refrigerant circulation device of the fifth viewpoint of this disclosure, R = 1.

[0014] Based on the refrigerant circulation apparatus of any of the second to fourth viewpoints, in the refrigerant circulation apparatus of the sixth viewpoint of this disclosure, R=(ρ md ×V md ×A d ) / (C r ×(2×ΔP r / ρ 1r ) 0.5 ×A v ×ρ 1rl +A v ×(2 / (λ+1)) ((λ+1) / 2(λ-1)) ×(λ×P 1r ×ρ 1rg ) 0.5 ).

[0015] A v It is the valve gap cross-sectional area (m²) of the gas-side shut-off valve and the liquid-side shut-off valve under their respective shut-off states. 2 ).

[0016] ρ 1rl It is the density of the liquid refrigerant (kg / m³) 3 ).

[0017] ρ 1rg It is the density of the gaseous refrigerant (kg / m³) 3 ).

[0018] P 1r It refers to the refrigerant pressure (MPa) on the upstream side of both the gas-side shut-off valve and the liquid-side shut-off valve.

[0019] λ is the specific heat ratio of the refrigerant.

[0020] ρ md It is the density (kg / m³) of the mixture of air and refrigerant flowing through the gap of the door that separates the interior and exterior of a designated space. 3 ).

[0021] V md It is the velocity (m / s) of the mixture of air and refrigerant flowing through the gap of the door that separates the inside and outside of a specified space.

[0022] A d It is the area (m²) of the gap between the doors that separate the interior and exterior of a specified space. 2 ).

[0023] ΔP r It is the pressure difference (Pa) between the inside and outside of the hole at the location where refrigerant is leaking.

[0024] C r It is the refrigerant flow coefficient when liquid refrigerant flows through an orifice at a location where refrigerant is leaking.

[0025] C r It is 0.6.

[0026] In the refrigerant circulation device of the sixth viewpoint, for example, when R32 is used as the refrigerant and the first part of the refrigerant circuit is located at a height of 2.2m above the ground in a specified space, if 1 / 4 of the LFL (lower flammability limit) specified in ISO 817 is set as the permissible refrigerant concentration in the specified space, then R = 1.96.

[0027] Based on this structure, the manufacturing or purchase cost of the gas-side shut-off valve is further suppressed.

[0028] Based on the refrigerant circulation apparatus of any of the second to fourth viewpoints, in the refrigerant circulation apparatus of the seventh viewpoint of this disclosure, R is determined according to at least one of the permissible average concentration, leakage height, and type of refrigerant. The permissible average concentration is the average concentration of refrigerant leaking into a specified space. The permissible average concentration is the concentration within a range deemed impossible for refrigerant leaking into the specified space to burn. The leakage height is the location of the first portion of the specified space when refrigerant leaks into it.

[0029] Based on this structure, since R is calculated by taking into account the size of the space specified for the refrigerant circulation device, the location of the refrigerant circulation device, and the type of refrigerant, it is possible to determine the leakage specifications that the gas-side shut-off valve and the liquid-side shut-off valve should meet when shutting off.

[0030] The refrigerant circulation device of the eighth aspect of this disclosure is the refrigerant circulation device of any of the first to seventh aspects. The flammable refrigerant is a slightly flammable refrigerant classified as "2L" according to the American ANSI / ASHRAE 34-2013 standard. The flammable refrigerant is a weakly flammable refrigerant classified as "2" according to the American ANSI / ASHRAE 34-2013 standard. The flammable refrigerant is a highly flammable refrigerant classified as "3" according to the American ANSI / ASHRAE 34-2013 standard. Attached Figure Description

[0031] Figure 1 This is a diagram showing the schematic structure of an air conditioning unit as one embodiment of a refrigerant circulation device. Figure 2 This is a diagram showing the refrigerant circuit of an air conditioning unit. Figure 3 It is a diagram showing a room (a designated space) equipped with air conditioning. Figure 4 This is a control block diagram of an air conditioning unit. Figure 5 This is a diagram illustrating the control process used to address refrigerant leaks. Figure 6 This is a diagram showing the refrigerant leakage rate in gas-side and liquid-side shut-off valves when they meet the specifications for safety shut-off valves in Appendix A (Specification) of the guidelines of the Japan Refrigeration and Air Conditioning Manufacturers Association. Figure 7 This is a graph showing the ratio of the refrigerant leakage rate in the liquid-side shut-off valve to the refrigerant leakage rate in the gas-side shut-off valve. Detailed Implementation

[0032] (1) Structure of air conditioning unit like Figure 1and Figure 2 As shown, an air conditioning unit 1, as one embodiment of a refrigerant circulation device, is a device that uses a vapor compression refrigeration cycle to cool or heat rooms (defined spaces) within buildings such as skyscrapers. The air conditioning unit 1 mainly includes a heat source side unit 2, multiple user side units 3a, 3b, 3c, and 3d, relay units 4a, 4b, 4c, and 4d connected to each user side unit 3a, 3b, 3c, and 3d, refrigerant connecting pipes 5 and 6, and a control unit 19 (see reference). Figure 4 Multiple utilization-side units 3a, 3b, 3c, and 3d are connected in parallel relative to heat source-side unit 2. Refrigerant connecting pipes 5 and 6 connect heat source-side unit 2 to utilization-side units 3a, 3b, 3c, and 3d via relay units 4a, 4b, 4c, and 4d. Control unit 19 controls the equipment comprising heat source-side unit 2, utilization-side units 3a, 3b, 3c, and 3d, and relay units 4a, 4b, 4c, and 4d.

[0033] Refrigerant circuit 10 is filled with R32. If flammable refrigerant leaks from refrigerant circuit 10 into the room (specified space) SP (refer to...). Figure 3 This could lead to a higher concentration of refrigerant in the room's SP (presumably referring to a specific type of refrigerant), potentially causing a combustion accident. Therefore, it is necessary to prevent such combustion accidents.

[0034] In addition, the air conditioning unit 1 switches the side units 3a, 3b, 3c, and 3d to cooling or heating operation via the switching mechanism 22 of the heat source side unit 2.

[0035] (1-1) Refrigerant connecting pipe The liquid refrigerant connecting pipe 5 mainly comprises: a confluence pipe section extending from the heat source side unit 2; a first branch pipe section 5a, 5b, 5c, 5d that branches into multiple (four in this case) branches in front of the relay units 4a, 4b, 4c, 4d; and second branch pipe sections 5aa, 5bb, 5cc, 5dd, the second branch pipe sections 5aa, 5bb, 5cc, 5dd connecting the relay units 4a, 4b, 4c, 4d with the utilization side units 3a, 3b, 3c, 3d.

[0036] In addition, the gas refrigerant connecting pipe 6 mainly has: a merging pipe section extending from the heat source side unit 2; a first branch pipe section 6a, 6b, 6c, 6d that branches into multiple (four in this case) in front of the relay units 4a, 4b, 4c, 4d; and second branch pipe sections 6aa, 6bb, 6cc, 6dd, the second branch pipe sections 6aa, 6bb, 6cc, 6dd connecting the relay units 4a, 4b, 4c, 4d with the utilization side units 3a, 3b, 3c, 3d.

[0037] (1-2) Utilizing side units Side units 3a, 3b, 3c, and 3d are installed indoors in buildings, etc. As described above, side units 3a, 3b, 3c, and 3d are connected to heat source side unit 2 via liquid refrigerant connecting pipe 5, gaseous refrigerant connecting pipe 6, and relay units 4a, 4b, 4c, and 4d to form part of refrigerant circuit 10.

[0038] Next, the structures of the utilizing side units 3a, 3b, 3c, and 3d will be explained. Furthermore, since utilizing side unit 3a has the same structure as utilizing side units 3b, 3c, and 3d, only the structure of utilizing side unit 3a will be explained here. As for the structures of utilizing side units 3b, 3c, and 3d, the letters "b", "c", and "d" will be used to represent the parts of utilizing side unit "3a", respectively, and the descriptions of each part will be omitted.

[0039] The utilization-side unit 3a mainly includes a utilization-side expansion valve 51a and a utilization-side heat exchanger 52a. Furthermore, the utilization-side unit 3a has a utilization-side liquid refrigerant pipe 53a and a utilization-side gaseous refrigerant pipe 54a. The utilization-side liquid refrigerant pipe 53a connects the liquid-side end of the utilization-side heat exchanger 52a to the liquid refrigerant connecting pipe 5 (here, the branch pipe section 5aa), and the utilization-side gaseous refrigerant pipe 54a connects the gaseous end of the utilization-side heat exchanger 52a to the gaseous refrigerant connecting pipe 6 (here, the second branch pipe section 6aa). The utilization-side circuit 3aa (first part) of the utilization-side unit 3a is composed of these utilization-side liquid refrigerant pipes 53a, utilization-side expansion valve 51a, utilization-side heat exchanger 52a, and utilization-side gaseous refrigerant pipes 54a.

[0040] The utilization-side expansion valve 51a is an electrically operated expansion valve that can reduce the pressure of the refrigerant and regulate the flow rate of the refrigerant flowing through the utilization-side heat exchanger 52a, and is installed on the utilization-side liquid refrigerant pipe 53a.

[0041] The utilization side heat exchanger 52a is a heat exchanger that functions as an evaporator for refrigerant to cool indoor air or as a heat exchanger for refrigerant to heat indoor air. Here, the utilization side unit 3a has a utilization side fan 55a. The utilization side fan 55a supplies indoor air, which serves as a cooling or heating source for the refrigerant flowing through the utilization side heat exchanger 52a, to the utilization side heat exchanger 52a. The utilization side fan 55a is driven by a utilization side fan motor 56a.

[0042] Various sensors are provided in the utilization side unit 3a. Specifically, the utilization side unit 3a is equipped with: a utilization side heat exchange liquid side sensor 57a, which detects the temperature of the refrigerant at the liquid side end of the utilization side heat exchanger 52a; a utilization side heat exchange gas side sensor 58a, which detects the temperature of the refrigerant at the gas side end of the utilization side heat exchanger 52a; and an indoor air sensor 59a, which detects the temperature of the indoor air drawn into the utilization side unit 3a. Furthermore, the utilization side unit 3a is equipped with a refrigerant leak detection unit 79a for detecting refrigerant leaks. The refrigerant leak detection unit 79a may be, for example, a semiconductor gas sensor or a detection unit that detects a sharp drop in refrigerant pressure within the utilization side unit 3a. When a semiconductor gas sensor is used, it is used in conjunction with the utilization side control unit 93a (see reference 93a). Figure 4 (Connection). In the case where a detection unit is used to detect a sharp drop in refrigerant pressure, a pressure sensor is installed in the refrigerant piping, and the utilization-side control unit 93a includes a detection algorithm that determines refrigerant leakage based on changes in the sensor value of the pressure sensor.

[0043] Additionally, while the refrigerant leak detection unit 79a is located in the user-side unit 3a, it is not limited to this location. It can also be installed in a remote control used to operate the user-side unit 3a, or in an indoor space where the user-side unit 3a is used for air conditioning. For example, the detection unit 79a can be located near the lower part of the outlet where refrigerant leaks from the user-side unit 3a into the designated space SP. Alternatively, it can be located directly below the user-side unit 3a or the outlet in the designated space SP, within a horizontal distance of 10m from the connection point with the indoor piping, and at a height of 0.3m or less from the ground. If the user-side expansion valve 51a, originally installed in the user-side unit 3a, has a fully closing function, this expansion valve can also be used as a liquid-side shut-off valve 71a.

[0044] (1-3) Heat source side unit The heat source side unit 2 is located outdoors in buildings such as buildings, for example, on the roof or ground. As described above, the heat source side unit 2 is connected to the utilization side units 3a, 3b, 3c, and 3d via the liquid refrigerant connecting pipe 5, the gaseous refrigerant connecting pipe 6, and the relay units 4a, 4b, 4c, and 4d, forming part of the refrigerant circuit 10.

[0045] The heat source side unit 2 mainly includes a compressor 21 and a heat source side heat exchanger 23. Furthermore, the heat source side unit 2 has a switching mechanism 22, which is a cooling / heating switching mechanism that switches between cooling and heating operation states. In cooling operation state, the heat source side heat exchanger 23 functions as a refrigerant heat exchanger, and the utilization side heat exchangers 52a, 52b, 52c, and 52d function as refrigerant evaporators. In heating operation state, the heat source side heat exchanger 23 functions as a refrigerant evaporator, and the utilization side heat exchangers 52a, 52b, 52c, and 52d function as refrigerant heat exchangers. The switching mechanism 22 is connected to the suction side of the compressor 21 via a refrigerant suction pipe 31. A storage tank 29 is provided on the refrigerant suction pipe 31 to temporarily store the refrigerant drawn into the compressor 21. The discharge side of the compressor 21 is connected to the switching mechanism 22 via a refrigerant discharge pipe 32. The switching mechanism 22 is connected to the gas side of the heat exchanger 23 on the heat source side via a first heat source side gas refrigerant pipe 33. The liquid side of the heat exchanger 23 is connected to the liquid refrigerant connecting pipe 5 on the heat source side via a heat source side liquid refrigerant pipe 34. A liquid-side shut-off valve 27 is provided at the connection point of the heat source side liquid refrigerant pipe 34 to the liquid refrigerant connecting pipe 5. The switching mechanism 22 is connected to the gas refrigerant connecting pipe 6 on the heat source side via a second heat source side gas refrigerant pipe 35. A gas-side shut-off valve 28 is provided at the connection point of the second heat source side gas refrigerant pipe 35 to the gas refrigerant connecting pipe 6. The liquid-side shut-off valve 27 and the gas-side shut-off valve 28 are, for example, manually operated valves. During operation, the liquid-side shut-off valve 27 and the gas-side shut-off valve 28 are set to the open state.

[0046] Compressor 21 is a device for compressing refrigerant, for example, a hermetically sealed compressor that uses a positive displacement compression element (not shown) such as a rotary or scroll compressor to rotate via a motor 21a.

[0047] The switching mechanism 22 is a device capable of switching the flow of refrigerant within the refrigerant circuit 10, and is, for example, constituted by a four-way switching valve. When the heat source-side heat exchanger 23 functions as a refrigerant heat exchanger and the utilization-side heat exchangers 52a, 52b, 52c, and 52d function as refrigerant evaporators (hereinafter referred to as the "refrigeration operation state"), the switching mechanism 22 connects the discharge side of the compressor 21 to the gas side of the heat source-side heat exchanger 23 (see reference 22). Figure 2 (Solid line of switching mechanism 22). Furthermore, when the heat source-side heat exchanger 23 is used as an evaporator for refrigerant and the heat exchangers 52a, 52b, 52c, and 52d are used as heat exchangers for refrigerant (hereinafter referred to as "heating operation state"), the switching mechanism 22 connects the suction side of the compressor 21 to the gas side of the heat source-side heat exchanger 23 (see reference 22). Figure 2(The dashed line of the first switching mechanism 22).

[0048] The heat source-side heat exchanger 23 functions as either a refrigerant heat exchanger or a refrigerant evaporator. Here, the heat source-side unit 2 includes a heat source-side fan 24. The heat source-side fan 24 draws outdoor air into the heat source-side unit 2, causes it to exchange heat with the refrigerant in the heat source-side heat exchanger 23, and then exhausts it to the outside. The heat source-side fan 24 is driven by a motor.

[0049] Furthermore, in the air conditioning unit 1, during cooling operation, refrigerant flows from the heat source side heat exchanger 23 through the liquid refrigerant connecting pipe 5 and relay units 4a, 4b, 4c, 4d to the utilization side heat exchangers 52a, 52b, 52c, 52d, which function as evaporators of the refrigerant. In addition, in the air conditioning unit 1, during heating operation, refrigerant flows from the compressor 21 through the gaseous refrigerant connecting pipe 6 and relay units 4a, 4b, 4c, 4d to the utilization side heat exchangers 52a, 52b, 52c, 52d, which function as heat exchangers of the refrigerant. During cooling operation, the configuration is as follows: the switching mechanism 22 is switched to cooling operation, the heat source side heat exchanger 23 functions as a heat exchanger of the refrigerant, and the refrigerant flows from the heat source side unit 2 to the utilization side units 3a, 3b, 3c, 3d through the liquid refrigerant connecting pipe 5 and relay units 4a, 4b, 4c, 4d. When in heating operation, the system is configured as follows: the switching mechanism 22 is switched to the heating operation state, and the refrigerant flows from the utilization side units 3a, 3b, 3c, 3d to the heat source side unit 2 through the liquid refrigerant connecting pipe 5 and the relay units 4a, 4b, 4c, 4d. The heat source side heat exchanger 23 functions as an evaporator for the refrigerant.

[0050] Furthermore, a heat source-side expansion valve 25 is provided here on the heat source-side liquid refrigerant pipe 34. The heat source-side expansion valve 25 is an electrically operated expansion valve that reduces the pressure of the refrigerant during heating operation, and is located on the liquid side end of the heat source-side liquid refrigerant pipe 34 near the heat source-side heat exchanger 23.

[0051] Furthermore, a refrigerant return pipe 41 is connected to the liquid refrigerant pipe 34 on the heat source side, and a refrigerant cooler 45 is provided therein. The refrigerant return pipe 41 branches off a portion of the refrigerant flowing through the liquid refrigerant pipe 34 on the heat source side and sends it to the compressor 21. The refrigerant cooler 45 uses the refrigerant flowing through the refrigerant return pipe 41 to cool the refrigerant flowing through the liquid refrigerant pipe 34 on the heat source side. Here, the heat source side expansion valve 25 is located in the portion of the liquid refrigerant pipe 34 on the heat source side, closer to the heat exchanger 23 than the refrigerant cooler 45.

[0052] The refrigerant return pipe 41 is a refrigerant pipe that sends refrigerant branching off from the heat source side liquid refrigerant pipe 34 to the suction side of the compressor 21. Furthermore, the refrigerant return pipe 41 mainly includes a refrigerant return inlet pipe 42 and a refrigerant return outlet pipe 43. The refrigerant return inlet pipe 42 branches off a portion of the refrigerant flowing through the heat source side liquid refrigerant pipe 34 from the portion between the liquid side end of the heat source side heat exchanger 23 and the liquid side shut-off valve 27 (here, the portion between the heat source side expansion valve 25 and the refrigerant cooler 45), and sends it to the inlet of the refrigerant return pipe 41 side of the refrigerant cooler 45. A refrigerant return expansion valve 44 is provided in the refrigerant return inlet pipe 42. The refrigerant return expansion valve 44 reduces the pressure of the refrigerant flowing through the refrigerant return pipe 41 while regulating the flow rate of the refrigerant flowing through the refrigerant cooler 45. The refrigerant return expansion valve 44 is an electrically operated expansion valve. The refrigerant return outlet pipe 43 delivers refrigerant from the outlet of the refrigerant return pipe 41 side of the refrigerant cooler 45 to the suction refrigerant pipe 31. The refrigerant return outlet pipe 43 of the refrigerant return pipe 41 is connected to the inlet side portion of the storage tank 29 in the suction refrigerant pipe 31. Furthermore, the refrigerant cooler 45 uses the refrigerant flowing through the refrigerant return pipe 41 to cool the refrigerant flowing through the heat source side liquid refrigerant pipe 34.

[0053] Various sensors are installed in the heat source side unit 2. Specifically, the heat source side unit 2 includes: a discharge pressure sensor 36, which detects the pressure (discharge pressure) of the refrigerant discharged from the compressor 21; a discharge temperature sensor 37, which detects the temperature (discharge temperature) of the refrigerant discharged from the compressor 21; and a suction pressure sensor 39, which detects the pressure (suction pressure) of the refrigerant drawn into the compressor 21. Furthermore, the heat source side unit 2 includes a heat source side heat exchanger liquid side sensor 38, which detects the temperature of the refrigerant at the liquid side end of the heat source side heat exchanger 23 (heat source side heat exchanger outlet temperature).

[0054] (1-4) Relay Unit Relay units 4a, 4b, 4c, and 4d are installed in rooms (designated spaces) of buildings such as towers. (Refer to SP) Figure 3The space SP1 behind the ceiling of the unit 2. Relay units 4a, 4b, 4c, and 4d, together with liquid refrigerant connecting pipe 5 and gaseous refrigerant connecting pipe 6, are located between the user-side units 3a, 3b, 3c, and 3d and the heat source-side unit 2, forming part of the refrigerant circuit 10. Relay units 4a, 4b, 4c, and 4d are sometimes configured close to the user-side units 3a, 3b, 3c, and 3d, and sometimes configured far away from the user-side units 3a, 3b, 3c, and 3d, and sometimes relay units 4a, 4b, 4c, and 4d are concentrated in one location.

[0055] Next, the structures of relay units 4a, 4b, 4c, and 4d will be described. Furthermore, since relay unit 4a has the same structure as relay units 4b, 4c, and 4d, only the structure of relay unit 4a will be described here. For the structures of relay units 4b, 4c, and 4d, "b", "c", or "d" will be used to represent the parts of relay unit 4a, respectively, and the descriptions of each part will be omitted.

[0056] The relay unit 4a mainly has a liquid connection pipe 61a and a gas connection pipe 62a.

[0057] One end of the liquid connecting pipe 61a is connected to the first branch pipe section 5a of the liquid refrigerant connecting pipe 5, and the other end is connected to the second branch pipe section 5aa of the liquid refrigerant connecting pipe 5. A liquid-side shut-off valve 71a is provided on the liquid connecting pipe 61a. The liquid-side shut-off valve 71a is an electrically operated expansion valve.

[0058] One end of the gas connecting pipe 62a is connected to the first branch pipe section 6a of the gas refrigerant connecting pipe 6, and the other end is connected to the second branch pipe section 6aa of the gas refrigerant connecting pipe 6. A gas-side shut-off valve 68a is provided on the gas connecting pipe 62a. The gas-side shut-off valve 68a is an electrically operated expansion valve.

[0059] In addition, when operating in cooling or heating mode, the liquid-side shut-off valve 71a and the gas-side shut-off valve 68a are set to the fully open state.

[0060] (1-5) Control Department like Figure 4As shown, the control unit 19 is composed of a heat source side control unit 92, relay side control units 94a, 94b, 94c, 94d, and utilization side control units 93a, 93b, 93c, 93d connected via transmission lines 95 and 96. The heat source side control unit 92 controls the equipment constituting the heat source side unit 2. The relay side control units 94a, 94b, 94c, 94d control the equipment constituting the relay units 4a, 4b, 4c, 4d. The utilization side control units 93a, 93b, 93c, 93d control the equipment constituting the utilization side units 3a, 3b, 3c, 3d. The heat source side control unit 92 located in heat source side unit 2, the relay side control units 94a, 94b, 94c, and 94d located in relay units 4a, 4b, 4c, and 4d, and the utilization side control units 93a, 93b, 93c, and 93d located in utilization side units 3a, 3b, 3c, and 3d can exchange control signals and other information with each other via transmission lines 95 and 96.

[0061] The heat source side control unit 92 includes a control board with electrical components such as a microcomputer and a memory, and is connected to various constituent devices 21, 22, 24, 25, 44, and various sensors 36, 37, 38, and 39 of the heat source side unit 2. The relay side control units 94a, 94b, 94c, and 94d include a control board with electrical components such as a microcomputer and a memory, and are connected to gas-side shut-off valves 68a-68d and liquid-side shut-off valves 71a-71d of the relay units 4a, 4b, 4c, and 4d. Furthermore, the relay side control units 94a, 94b, 94c, and 94d are connected to the heat source side control unit 92 via a first transmission line 95. The utilization side control units 93a, 93b, 93c, and 93d include control boards equipped with electrical components such as microcomputers and memory, and are connected to various constituent devices 51a-51d, 55a-55d, and various sensors 57a-57d, 58a-58d, 59a-59d, and 79a-79d of the utilization side units 3a, 3b, 3c, and 3d. Here, the wiring for connecting the refrigerant leak detection units 79a, 79b, 79c, and 79d to the utilization side control units 93a, 93b, 93c, and 93d is designated as wiring 97a, 97b, 97c, and 97d. Furthermore, the utilization side control units 93a, 93b, 93c, and 93d and the relay side control units 94a, 94b, 94c, and 94d are connected via a second transmission line 96.

[0062] In this way, the control unit 19 performs overall operation control of the air conditioning unit 1. Specifically, the control unit 19 controls the various constituent devices 21, 22, 24, 25, 44, 51a-51d, 55a-55d, 68a-68d, and 71a-71d of the air conditioning unit 1 (here, the heat source side unit 2, the utilization side units 3a, 3b, 3c, 3d, and the relay units 4a, 4b, 4c, 4d) based on the detection signals of the various sensors 36, 37, 38, 39, 57a-57d, 58a-58d, 59a-59d, and 79a-79d mentioned above.

[0063] (2) Basic operation of air conditioning unit Next, the basic operation of the air conditioning unit 1 will be explained. As mentioned above, the basic operation of the air conditioning unit 1 includes cooling operation and heating operation. In addition, the basic operation of the air conditioning unit 1 described below is performed by the control unit 19, which controls the constituent equipment of the air conditioning unit 1 (heat source side unit 2, utilization side units 3a, 3b, 3c, 3d and relay units 4a, 4b, 4c, 4d).

[0064] (2-1) Refrigeration Operation During refrigeration operation, for example, when all side units 3a, 3b, 3c, and 3d are in refrigeration operation (when all side heat exchangers 52a, 52b, 52c, and 52d function as evaporators for the refrigerant, and the heat source side heat exchanger 23 functions as a heat exchanger for the refrigerant), the switching mechanism 22 switches to the refrigeration operation state. Figure 2 (As shown by the solid line in the switching mechanism 22), the compressor 21, the heat source side fan 24, and the utilization side fans 55a, 55b, 55c, and 55d are driven. Furthermore, the liquid-side shut-off valves 71a, 71b, 71c, and 71d and the gas-side shut-off valves 68a, 68b, 68c, and 68d of the relay units 4a, 4b, 4c, and 4d are set to the fully open state.

[0065] Here, the operation of various devices in the utilizing side units 3a, 3b, 3c, and 3d is controlled by the side control units 93a, 93b, 93c, and 93d. The side control units 93a, 93b, 93c, and 93d transmit information indicating that the utilizing side units 3a, 3b, 3c, and 3d should operate in cooling mode to the heat source side control unit 92 and the relay side control units 94a, 94b, 94c, and 94d via transmission lines 95 and 96. The heat source side control unit 92 and the relay side control units 94a, 94b, 94c, and 94d control various devices in the heat source side unit 2 and the relay units 4a, 4b, 4c, and 4d, respectively, based on the information received from the utilizing side units 3a, 3b, 3c, and 3d.

[0066] During refrigeration operation, the high-pressure refrigerant discharged from the compressor 21 is sent to the heat source side heat exchanger 23 via the switching mechanism 22. The refrigerant sent to the heat source side heat exchanger 23 is cooled by exchanging heat with the outdoor air supplied by the heat source side fan 24, which functions as a refrigerant heat exchanger, and thus condenses. The refrigerant then flows out of the heat source side unit 2 through the heat source side expansion valve 25, the refrigerant cooler 45, and the liquid side shut-off valve 27. At this time, the refrigerant flowing out of the heat source side unit 2 is cooled in the refrigerant cooler 45 by the refrigerant flowing through the refrigerant return pipe 41.

[0067] The refrigerant flowing out from the heat source side unit 2 is sent to the relay units 4a, 4b, 4c, and 4d in a branched manner through the liquid refrigerant connecting pipe 5 (the confluence pipe section and the first branch pipe sections 5a, 5b, 5c, and 5d). The refrigerant sent to the relay units 4a, 4b, 4c, and 4d flows out from the relay units 4a, 4b, 4c, and 4d through the liquid side shut-off valves 71a, 71b, 71c, and 71d.

[0068] Refrigerant flowing from relay units 4a, 4b, 4c, and 4d is sent to user-side units 3a, 3b, 3c, and 3d via second branch pipe sections 5aa, 5bb, 5cc, and 5dd (the sections in liquid refrigerant connecting pipe 5 that connect relay units 4a, 4b, 4c, and 4d to user-side units 3a, 3b, 3c, and 3d). The refrigerant sent to user-side units 3a, 3b, 3c, and 3d is then depressurized by user-side expansion valves 51a, 51b, 51c, and 51d before being sent to user-side heat exchangers 52a, 52b, 52c, and 52d. The refrigerant supplied to the utilization-side heat exchangers 52a, 52b, 52c, and 52d is heated and evaporated by exchanging heat with indoor air supplied from the room by the utilization-side fans 55a, 55b, 55c, and 55d, which function as evaporators of the refrigerant. The evaporated refrigerant flows out from the utilization-side units 3a, 3b, 3c, and 3d. On the other hand, the indoor air cooled in the utilization-side heat exchangers 52a, 52b, 52c, and 52d is sent into the room, thereby cooling the room.

[0069] The refrigerant flowing out from the utilization side units 3a, 3b, 3c, and 3d is sent to the relay units 4a, 4b, 4c, and 4d through the second branch pipe sections 6aa, 6bb, 6cc, and 6dd of the gas refrigerant connecting pipe 6. The refrigerant sent to the relay units 4a, 4b, 4c, and 4d flows out from the relay units 4a, 4b, 4c, and 4d through the gas side shut-off valves 68a, 68b, 68c, and 68d.

[0070] The refrigerant flowing from relay units 4a, 4b, 4c, and 4d is sent to the heat source side unit 2 in a combined state through the gas refrigerant connecting pipe 6 (the confluence pipe section and the first branch pipe sections 6a, 6b, 6c, and 6d). The refrigerant sent to the heat source side unit 2 is drawn into the compressor 21 through the gas side shut-off valve 28, the switching mechanism 22, and the storage tank 29.

[0071] (2-2) Heating Operation During heating operation, for example, when all side units 3a, 3b, 3c, and 3d are in heating operation (when all side heat exchangers 52a, 52b, 52c, and 52d function as refrigerant heat exchangers, and heat source side heat exchanger 23 functions as a refrigerant evaporator), the switching mechanism 22 switches to the heating operation state. Figure 2 (As shown by the dashed line in the switching mechanism 22), the compressor 21, the heat source side fan 24, and the utilization side fans 55a, 55b, 55c, and 55d are driven. Furthermore, the liquid-side shut-off valves 71a, 71b, 71c, and 71d and the gas-side shut-off valves 68a, 68b, 68c, and 68d of the relay units 4a, 4b, 4c, and 4d are set to the fully open state.

[0072] Here, the operation of various devices in the utilizing side units 3a, 3b, 3c, and 3d is controlled by the side control units 93a, 93b, 93c, and 93d. The side control units 93a, 93b, 93c, and 93d transmit information indicating the intention to operate the utilizing side units 3a, 3b, 3c, and 3d in heating mode to the heat source side control unit 92 and the relay side control units 94a, 94b, 94c, and 94d via transmission lines 95 and 96. The heat source side control units 92 and the relay side control units 94a, 94b, 94c, and 94d, upon receiving information from the utilizing side units 3a, 3b, 3c, and 3d, control the operation of various devices in the heat source side unit 2 and the relay units 4a, 4b, 4c, and 4d.

[0073] The high-pressure refrigerant discharged from the compressor 21 flows out from the heat source side unit 2 through the switching mechanism 22 and the gas side shut-off valve 28.

[0074] The refrigerant flowing out from the heat source side unit 2 is sent to the relay units 4a, 4b, 4c, and 4d via the gas refrigerant connecting pipe 6 (the confluence pipe section and the first branch pipe sections 6a, 6b, 6c, and 6d). The refrigerant sent to the relay units 4a, 4b, 4c, and 4d flows out from the relay units 4a, 4b, 4c, and 4d through the gas side shut-off valves 68a, 68b, 68c, and 68d.

[0075] The refrigerant flowing from relay units 4a, 4b, 4c, and 4d is sent to user-side units 3a, 3b, 3c, and 3d via second branch pipe sections 6aa, 6bb, 6cc, and 6dd (the sections in gas refrigerant connecting pipe 6 that connect relay units 4a, 4b, 4c, and 4d to user-side units 3a, 3b, 3c, and 3d). The refrigerant sent to user-side units 3a, 3b, 3c, and 3d is then sent to user-side heat exchangers 52a, 52b, 52c, and 52d. The high-pressure refrigerant sent to user-side heat exchangers 52a, 52b, 52c, and 52d is cooled and condensed by exchanging heat with indoor air supplied from the room by user-side fans 55a, 55b, 55c, and 55d, which function as heat exchangers for the refrigerant. The refrigerant, after being depressurized by the expansion valves 51a, 51b, 51c, and 51d on the utilization side, flows out from the utilization side units 3a, 3b, 3c, and 3d. On the other hand, indoor air heated in the heat exchangers 52a, 52b, 52c, and 52d on the utilization side is sent into the room, thereby providing indoor heating.

[0076] Refrigerant flowing from the utilization side units 3a, 3b, 3c, and 3d is sent to relay units 4a, 4b, 4c, and 4d via the second branch pipe sections 5aa, 5bb, 5cc, and 5dd (the sections in the liquid refrigerant connecting pipe 5 that connect relay units 4a, 4b, 4c, and 4d to the utilization side units 3a, 3b, 3c, and 3d). The refrigerant sent to relay units 4a, 4b, 4c, and 4d flows out of relay units 4a, 4b, 4c, and 4d through liquid-side shut-off valves 71a, 71b, 71c, and 71d.

[0077] Refrigerant flowing from relay units 4a, 4b, 4c, and 4d is sent to heat source side unit 2 in a combined state through liquid refrigerant connecting pipe 5 (combination pipe section and first branch pipe sections 5a, 5b, 5c, and 5d). The refrigerant sent to heat source side unit 2 is then sent to heat source side expansion valve 25 via liquid side shut-off valve 27 and refrigerant cooler 45. After being depressurized by heat source side expansion valve 25, the refrigerant is sent to heat source side heat exchanger 23. The refrigerant sent to heat source side heat exchanger 23 is heated by exchanging heat with outdoor air supplied by heat source side fan 24, thereby evaporating. The evaporated refrigerant is drawn into compressor 21 via switching mechanism 22 and storage tank 29.

[0078] (3) Operation of the air conditioning unit when refrigerant leaks Next, use Figure 5The control flow shown illustrates the operation of the air conditioning unit 1 when a refrigerant leak occurs. Furthermore, the operation of the air conditioning unit 1 during a refrigerant leak, as described below, is performed by the control unit 19, which controls the constituent equipment of the air conditioning unit 1 (heat source side unit 2, utilization side units 3a, 3b, 3c, 3d, and relay units 4a, 4b, 4c, 4d), in the same manner as the basic operation described above.

[0079] The same control is used for any refrigerant leaks occurring in any of the utilization side units 3a, 3b, 3c, and 3d. Therefore, the following explanation will be based on the case where refrigerant leakage into the room where utilization side unit 3a is installed.

[0080] exist Figure 5 In step S1, it is determined whether any of the refrigerant leakage detection units 79a, 79b, 79c, and 79d of the utilization side units 3a, 3b, 3c, and 3d has detected a refrigerant leak. Here, if the refrigerant leakage detection unit 79a of the utilization side unit 3a detects a refrigerant leak into a designated space (indoor area) of the utilization side unit 3a, the process proceeds to the next step S2.

[0081] In step S2, in the utilization side unit 3a where a refrigerant leak has occurred, an alarm is issued to a person in the designated space of the utilization side unit 3a by emitting a warning sound such as a buzzer and turning on an alarm (not shown) that illuminates a light.

[0082] Next, in step S3, it is determined whether the utilization side unit 3a is in cooling operation. Here, if the utilization side unit 3a is in heating operation, or if the utilization side unit 3a is in a stopped or temporarily stopped state where it is neither cooling nor heating, the process proceeds from step S3 to step S4.

[0083] In step S4, the utilizing side unit 3a is put into cooling operation to reduce the refrigerant pressure in the utilizing side unit 3a. However, the cooling operation in step S4 differs from normal cooling operation; it prioritizes reducing the refrigerant pressure in the utilizing side unit 3a. When the air conditioning unit 1 is in heating operation, the switching mechanism 22 is switched to cooling operation mode to put the air conditioning unit 1 into cooling operation mode. When the utilizing side unit 3a is in a stopped or temporarily stopped state, the utilizing side unit 3a is set to cooling operation mode to reduce the refrigerant pressure in the utilizing side unit 3a.

[0084] Following step S4, in step S5, the opening of the heat source side expansion valve 25 of heat source side unit 2 is reduced. During normal refrigeration operation, the heat source side expansion valve 25 is fully open; reducing its opening here lowers the pressure of the refrigerant flowing to the utilization side units 3a, 3b, 3c, and 3d. Additionally, the utilization side expansion valve 51a of utilization side unit 3a is set to the fully open state.

[0085] Furthermore, in step S5, the opening of the refrigerant return expansion valve 44 is increased compared to normal refrigeration operation, thereby increasing the amount of refrigerant flowing through the refrigerant return pipe 41, which acts as a bypass path. As a result, more of the refrigerant that releases heat, condenses, and flows towards the user-side units 3a, 3b, 3c, and 3d in the heat source-side heat exchanger 23 returns to the suction side of the compressor 21 via the refrigerant return pipe 41. In other words, the amount of refrigerant that releases heat, condenses, and flows towards the user-side units 3a, 3b, 3c, and 3d in the heat source-side heat exchanger 23 is reduced. Through the above control, the pressure of the refrigerant in the user-side unit 3a, where refrigerant is leaking, is reduced more rapidly. Moreover, the refrigerant flowing through the refrigerant return pipe 41 flows into the storage tank 29. Therefore, a portion of the flowing-in refrigerant can be stored in the storage tank 29.

[0086] Furthermore, in step S5, the rotational speed of the side fan 55a also decreases.

[0087] In step S6, based on the sensor values ​​of the liquid-side heat exchanger sensor 57a and the gas-side heat exchanger sensor 58a of the utilization-side unit 3a, it is determined whether the pressure of the refrigerant in the utilization-side unit 3a is low enough. When it is determined that the sensor values ​​meet the predetermined conditions and the pressure of the refrigerant in the utilization-side unit 3a is low enough, the process proceeds from step S6 to step S7. Furthermore, in step S6, the time elapsed is monitored. If a predetermined time has elapsed after executing step S5, it is determined that the pressure of the refrigerant in the utilization-side unit 3a has decreased to some extent, and the process proceeds to step S7.

[0088] Additionally, in step S6, the pressure of the refrigerant in the utilization side unit 3a is monitored and controlled to ensure that the pressure of the refrigerant in the utilization side unit 3a is substantially not less than atmospheric pressure. The transition from step S6 to step S7 occurs before the pressure of the refrigerant in the utilization side unit 3a becomes less than atmospheric pressure.

[0089] In step S7, the liquid-side shut-off valve 71a and the gas-side shut-off valve 68a of the relay unit 4a corresponding to the user-side unit 3a where a refrigerant leak has occurred are closed. This disconnects the user-side unit 3a from the refrigerant circuit 10 from which the refrigerant circulates, resulting in almost no refrigerant flow from the heat source-side unit 2 to the user-side unit 3a. Then, in step S7, the operation of all units, including the other user-side units 3b, 3c, 3d and the heat source-side unit 2, is stopped.

[0090] (4) Design or selection of gas-side shut-off valves and liquid-side shut-off valves As mentioned above, liquid-side shut-off valves 71a, 71b, 71c, and 71d, and gas-side shut-off valves 68a, 68b, 68c, and 68d are controlled to close when a refrigerant leak is detected (see [link to relevant documentation]). Figure 4 Step S7). In other words, when a refrigerant leak is detected in any of the utilization side units 3a, 3b, 3c, and 3d, the liquid-side shut-off valves 71a, 71b, 71c, and 71d and the gas-side shut-off valves 68a, 68b, 68c, and 68d of the corresponding relay units 4a, 4b, 4c, and 4d switch from the open, non-shutdown state to the closed shut-off state.

[0091] In the air conditioning unit 1 of this embodiment, the liquid-side shut-off valves 71a, 71b, 71c, 71d and the gas-side shut-off valves 68a, 68b, 68c, 68d are designed or selected in the following manner.

[0092] (4-1) Regarding the room (specified space) of the side unit equipped with air conditioning. First, before designing or selecting the gas-side shut-off valve and the liquid-side shut-off valve, information about the building equipped with the air conditioning unit 1 is obtained, specifically, information about the rooms where the utilization side units 3a, 3b, 3c, and 3d are installed.

[0093] Here, four units are configured together using side units 3a, 3b, 3c, and 3d and relay units 4a, 4b, 4c, and 4d. Figure 3 The ceiling-back space SP1 of the room (defined space) SP shown. Side units are not installed on the floor FL of this room SP. In other words, side units 3a, 3b, 3c, and 3d are ceiling-mounted units, not floor-mounted units.

[0094] Room SP is equipped with a door DR for entry and exit. Door DR is closed when no one is entering or exiting. A gap (undercut) UC exists beneath door DR. Furthermore, an air vent (not shown) is located in the ceiling of room SP. The area of ​​gap UC is A. d (m 2For example, if the height of gap UC is 4mm and the width is 800mm, then the area A of gap UC is... d It is their product, which is 0.0032 (m 2 ).

[0095] Furthermore, since the side units 3a, 3b, 3c, and 3d are arranged in the space SP1 behind the ceiling of room SP, the distance H from the ground FL to the side loops 3aa, 3bb, 3cc, and 3dd of the side units 3a, 3b, 3c, and 3d is equal to the height dimension (ceiling height) of room SP.

[0096] (4-2) Calculation method for refrigerant leakage rate of gas-side shut-off valve and liquid-side shut-off valve Next, the calculation method for the leakage amount required during the required flow interruption when designing or selecting the gas-side shut-off valve and the liquid-side shut-off valve will be explained in turn. In addition, in the following description, in order to explain the general gas-side shut-off valve and liquid-side shut-off valve and the utilization side unit, rather than the gas-side shut-off valve and liquid-side shut-off valve and the utilization side unit unique to the air conditioning unit 1 of this embodiment, the numbers and symbols marked in the drawings will not be used.

[0097] Furthermore, in this embodiment, "air" is used to evaluate the leakage amount when the flow is interrupted, as the gas is in a single gas phase under standard conditions.

[0098] As described in the "Summary of the Invention" above, in Appendix A (Specifications) of the guidelines of the Japan Refrigeration and Air Conditioning Manufacturers Association, when the fluid is air and the pressure difference across the gas-side shut-off valve and the liquid-side shut-off valve is 1 MPa, 300 (cm 3 The following leakage rates ( / min) are specified as the required leakage rates for gas-side and liquid-side shut-off valves during shut-off. Based on the same leakage rates during shut-off required by the above guidelines for both gas-side and liquid-side shut-off valves, the valve clearance and refrigerant leakage rate during shut-off, as assumed in the above guidelines, can be calculated. Figure 6 As shown, within the same leakage gap, the refrigerant leakage rate in the liquid-side shut-off valve is greater than that in the gas-side shut-off valve. This is because the density of liquid refrigerant is greater than that of gaseous refrigerant. Therefore, if the refrigerant leakage rate can be calculated according to the above guidelines, then it is possible to calculate the extent to which the leakage rate increases when the gas-side shut-off valve is shut off below that refrigerant leakage rate.

[0099] In both gas-side and liquid-side shut-off valves, the refrigerant leakage rate in the gas-side and liquid-side shut-off valves that meets the specifications outlined in the above guidelines is as follows: Figure 6As shown.

[0100] Figure 6 The horizontal axis represents the pressure equivalent saturation temperature of the refrigerant within the cycle. If the temperature around the room (defined space) where liquid refrigerant is stored or the heat exchanger on the heat source side changes, the aforementioned pressure equivalent saturation temperature within the cycle will change. Regarding the calculation of the refrigerant leakage rate derived from the leakage amount during flow interruption according to the above guidelines, there is firstly a method (one calculation method): for liquid refrigerants, calculation is performed using a formula based on Bernoulli's theorem; for gaseous refrigerants, calculation is performed using a formula expressing the flow rate of the compressible fluid. Secondly, there is another method (a second calculation method): calculation is performed using the Cv value, which represents the inherent leakage amount of both the gas-side and liquid-side flow interruption valves. Furthermore, the refrigerant leakage rate can also be calculated based on these leakage amount calculations. Figure 6 Solid lines represent values ​​obtained using one calculation method, and dashed lines represent values ​​obtained using another calculation method. Here, R32 with a flammability rating of A2L is used as a representative of flammable refrigerants. This graph can also be plotted in the same way as for other flammable refrigerants by setting their physical property values ​​to those of each refrigerant.

[0101] (4-2-1) Equivalent diameter d of valve gap when gas-side and liquid-side shut-off valves are shut off v Calculation In the above guidelines, when the fluid is air and the pressure difference across the gas-side shut-off valve and the liquid-side shut-off valve is 1 MPa, 300 (cm 3 The following values ​​( / min) are specified as the leakage limits that gas-side and liquid-side shut-off valves must meet during shut-off. Based on these conditions, the valve clearance for shut-off of both gas-side and liquid-side shut-off valves is first determined.

[0102] The valve clearance cross-sectional area A is calculated based on the air volumetric flow rate, the air inlet absolute pressure, the air density, and the air specific heat ratio. v The equivalent diameter d of the valve clearance is calculated by setting the cross-section as a circle. v The specific heat ratio κ of air is set to 1.40 (20℃). When the pressure ratio P2 / P1 exceeds (2 / (κ+1))×(κ / (κ-1)), the flow velocity exceeds the speed of sound. In the pressure difference mentioned above, P2 / P1=(1+0.1013) / 0.1013=10.87 (2 / (κ+1))×(κ / (κ-1))=(2 / 2.4)×1.4 / 0.4=0.528 Therefore, the flow velocity exceeds the supersonic speed.

[0103] Mass flow rate G a Volumetric flow rate Qa Valve clearance equivalent diameter d v The following formula can be used to calculate it. When the flow velocity exceeds the speed of sound, (Equation 1): G a =A v ×(2 / (κ+1)) ((κ+1) / 2(κ-1)) ×(κ×P 1a ×ρ 1a ) 0.5 (Equation 2): A v =Q a ×ρ 2a ×(2 / (κ+1)) (-(κ+1) / 2(κ-1)) ×(κ×P 1a ×ρ 1a ) (-0.5) (Equation 3): d v =(4×A) v / π) 0.5 .

[0104] In the aforementioned guidelines, the leakage rate during shut-off is specified to be 300 (cm³) for both gas-side and liquid-side shut-off valves. 3 / min), equivalent to 5×10 -6 (m 3 / s). Furthermore, in the aforementioned guidelines, the leakage rate during shut-off is similarly specified as 300 (cm²) for both gas-side and liquid-side shut-off valves. 3 Since the valve clearance is below ( / min), it is assumed that the same valve gap exists for both gas-side and liquid-side shut-off valves.

[0105] Substitute this condition into equation (2) and calculate A. v The permissible valve clearance (d) in Appendix A (specifies) of the above-mentioned "Specifications for Safety Shut-off Valves" is... vG ), valve gap cross-sectional area (A) vG )for: d vG =d vL = 5.47E-5(m) A vG =A vL =2.24E-9(m) 2 ).

[0106] (4-2-2) Calculation of refrigerant leakage rate based on one of the calculation methods Next, the valve clearance (d) is calculated. vG The leakage rate G of the leaked refrigerant r Perform the calculation.

[0107] The calculation is performed under the following conditions: in the liquid-side pipeline (liquid refrigerant connecting pipe), the upstream side of the shut-off valve when viewed from the user-side unit is liquid refrigerant, and in the gas-side pipeline (gas refrigerant connecting pipe), the upstream side of the shut-off valve when viewed from the user-side unit is gas refrigerant.

[0108] First, assuming the leak orifice is a throttling orifice and the liquid refrigerant flows through it, the leakage velocity of the refrigerant in the liquid-side pipeline, i.e., the refrigerant leakage velocity (G) of the liquid-side shut-off valve, can be calculated using Bernoulli's theorem. rL )hour, (Equation 4): G rL =C r ×(2×ΔP r / ρ 1rl ) 0.5 ×A vL ×ρ 1rl .

[0109] Next, the refrigerant leakage rate in the gas-side pipeline, i.e. the refrigerant leakage rate of the gas-side shut-off valve (G) rG The specific heat ratio κ is taken as the value of the refrigerant at 20°C saturated gas. Therefore, the leakage velocity of the refrigerant in the gas-side pipeline (G) is... rG )for (Equation 5): G rG =A vG ×(2 / (λ+1)) ((λ+1) / 2(λ-1)) ×(λ×P 1r ×ρ 1rg ) 0.5 .

[0110] Therefore, the refrigerant leakage rate G towards the specified space when the liquid-side shut-off valve and the gas-side shut-off valve are shut off is... r for (Equation 6): G r =G rL +G rG =C r ×(2×ΔP r / ρ 1rl ) 0.5 ×A vL ×ρ 1rl +A vG ×(2 / (λ+1)) ((λ+1) / 2(λ-1)) ×(λ×P 1r ×ρ 1rg ) 0.5 .

[0111] In addition, variables affecting the refrigerant leakage rate from the valve gap of the shut-off valve can be cited as (4-2-2-A) to (4-2-2-E). The relevant calculation methods for each are shown below.

[0112] (4-2-2-A) Types of refrigerants Assuming any one of R32, R452B, R454B, R1234yf, or R1234ze(E) is used as a refrigerant, calculate the physical property values ​​of each refrigerant using NISTRefpropV9.1 (a refrigerant property lookup and calculation software).

[0113] (4-2-2-B) The ambient temperature and the pressure difference between the refrigerant pressure and atmospheric pressure on the upstream side of the shut-off valve after the air conditioning unit stops determine the refrigerant pressure. It can be assumed that after the air conditioning unit stops, the refrigerant pressure located on the heat source side (upstream side) of the unit closer to the shut-off valve is determined by the highest temperature outside the building. According to the high-temperature test conditions for air conditioning units in the United States (Table 1 below), the highest external temperature is set to 55°C, and the refrigerant pressure on the upstream side of the shut-off valve is set to the saturation pressure at 55°C.

[0114] [Table 1] a There are no regulations regarding outdoor relative humidity, as it has no impact on performance. b Dew point temperature and relative humidity were evaluated at 0.973 atm (14.3 psi). c According to AHRI standard 210 / 240 d T3* is the modified T3 condition, where the indoor settings are similar to the AHRI condition. Source: Evaluation of Alternative Refrigerants for High-Ambient-Temperature Environments: R-22 and R-410A Alternatives for Mini-Split Air Conditioners, ORNL, P5, 2015

[0115] (4-2-2-C) Liquid density, gas density The density (kg / m³) of the liquid refrigerant was calculated using NISTRefprop V9.1. 3 Density of gaseous refrigerant (kg / m³) 3 ).

[0116] (4-2-2-D) Specific heat ratio The specific heat ratio was calculated using NISTRefprop V9.1. Additionally, the specific heat ratio of a saturated gas of refrigerant at 27°C was calculated.

[0117] (4-2-2-E) State of refrigerant in liquid-side and gas-side pipelines After setting the shut-off valve to the shut-off state, the refrigerant in both the liquid-side and gas-side pipelines upstream of the shut-off valve is assumed to be in the liquid and gas phases, or in both gas and gas phases. Here, the calculation is performed assuming the refrigerant leakage rate is greater than the calculated rate. In other words, the calculation is performed assuming that, after setting the shut-off valve to the shut-off state, the refrigerant in the liquid-side pipeline upstream of the shut-off valve is in the liquid phase and the refrigerant in the gas-side pipeline upstream of the shut-off valve is in the gas phase.

[0118] If the variables are calculated as described above, the leakage rates of refrigerant leaking from the valve gap for different refrigerants are shown in Table 2 below, for example.

[0119] [Table 2] The refrigerant leakage rate through the valve gap when the shut-off valve is closed. (Conditions) Ambient temperature 55°C, shut-off valve gap equivalent to 300 cc / min, specific heat ratio 27°C.

[0120] Furthermore, by simply changing the physical property values, the refrigerant leakage rate of each refrigerant under varying ambient temperatures (external building temperatures) can be calculated using equations (4), (5), and (6). There is a tendency for the refrigerant leakage rate to increase with higher ambient temperatures. Therefore, by determining the refrigerant leakage rate under different external temperatures (maximum external gas temperatures) in each region, suitable shut-off valves for each region can be selected and designed.

[0121] (4-2-3) Calculation of refrigerant leakage rate based on calculation method two Next, formulas are shown for calculating the leakage of both the gas-side shut-off valve and the liquid-side shut-off valve using the Cv value, which represents the inherent leakage of the valve.

[0122] If the Cv value is used to determine the leakage of the gas-side shut-off valve, then (Equation 7): Cv=Q×3600×(ρ / ρa ×(273+20)) 0.5 / (2519×P1 / 1000000).

[0123] If the Cv value is used to determine the leakage of the liquid-side shut-off valve, then (Equation 8): Cv=0.02194×Q×1000×60×(ρ / 1000 / Δp / 1000000) 0.5 .

[0124] In the aforementioned guidelines, to ensure that the refrigerant leakage of both the gas-side and liquid-side shut-off valves meets the requirement of 300 (cm³) when the fluid is air and the pressure difference across the gas-side and liquid-side shut-off valves is 1 MPa... 3 If (equation 7) is used for values ​​below ( / min), then Cv satisfies the following relationship: Cv = 1.11 × 10 -4 .

[0125] Furthermore, the leakage rates of gaseous and liquid refrigerants can be calculated using the aforementioned Cv values ​​and equations (7) and (8).

[0126] (4-3) Through the calculations performed in (4-1) to (4-2), the valve clearance and refrigerant leakage rate assumed in the aforementioned guidelines were derived. Next, based on these, the extent to which the leakage rate of the gas-side shut-off valve could increase during shut-off was calculated. Furthermore, the appropriate extent to which the leakage rate of the liquid-side shut-off valve should decrease during shut-off as the leakage rate of the gas-side shut-off valve increases was calculated. For this purpose, a range from 300 (cm²) was defined as the sum of the refrigerant leakage rates of both the gas-side and liquid-side shut-off valves being equal to the sum of the refrigerant leakage rates under the assumption of the same valve clearance for both valves according to the aforementioned guidelines. 3 The design or selection is based on changing the leakage rate of the gas-side shut-off valve and the liquid-side shut-off valve during shut-off, starting from / min.

[0127] The changes in refrigerant leakage rate in the gas-side shut-off valve and the liquid-side shut-off valve under the above conditions are as follows: Figure 6 As shown.

[0128] When the leakage rates of the gas-side and liquid-side shut-off valves are changed during shut-off, the refrigerant leakage rate in the gas-side shut-off valve increases from g0 to g. 00 The refrigerant leakage rate in the liquid-side shut-off valve decreased from l0 to l 00Here, the ratio of the refrigerant leakage rate in the liquid-side shut-off valve to the refrigerant leakage rate in the gas-side shut-off valve before the leakage is changed when altering the gas-side and liquid-side shut-off valves is... (Equation 9): l0 / g0 = X.

[0129] Furthermore, the ratio of the refrigerant leakage rate in the gas-side shut-off valve after the leakage rate during shut-off is changed to the refrigerant leakage rate in the gas-side shut-off valve before the leakage rate during shut-off is set as (Equation 10): g 00 / g0=Y.

[0130] If the sum of the refrigerant leakage rates in the liquid-side and gas-side shut-off valves remains unchanged before and after the change in leakage rate during the flow interruption, then (Equation 11): l0-l 00 =g 00 -g0. If equation (9) and equation (10) are used to transform equation (11), then (Equation 12): l 00 = (X-Y+1)×g0.

[0131] Therefore, the change in refrigerant leakage rate in the liquid-side shut-off valve can be calculated using the following formula. (Equation 13): l 00 / l0=1-(Y-1) / X.

[0132] Table 3 shows the diameters of the gaseous refrigerant connecting pipes and the liquid refrigerant connecting pipes.

[0133] [Table 3]

[0134] As shown in Table 3 under the gas / liquid side pipe diameter item, the ratio of the gas-side refrigerant connection pipe diameter to the liquid-side refrigerant connection pipe diameter is in the range of approximately 1.6 to approximately 2.7 times. The leakage rate of the gas-side shut-off valve increases proportionally to this refrigerant connection pipe diameter ratio when it shuts off relative to the liquid-side shut-off valve. Figure 7 X represents the ratio of the refrigerant leakage rate in the liquid-side shut-off valve to the refrigerant leakage rate in the gas-side shut-off valve. If the pressure within the refrigerant cycle is varied within the range of saturation pressure at 10°C to 55°C, then X varies by a factor of 2.7 to 10.8.

[0135] Here, with Y = 1.6, we can obtain from equation (13) l 00 / l0=1-0.6 / X If X is varied by a factor of 2.7 to 10.8 at this time, it represents the change in the refrigerant leakage rate in the liquid-side shut-off valve.00 / l0 varies between 0.78 and 0.94 times. Therefore, in this case, as long as it is within 300 (cm) 3 The design range can be 0.78 to 0.94 times ( / min) or the maximum leakage rate during liquid-side shut-off can be selected.

[0136] Similarly, when Y = 2.7, we can obtain from equation (13) l 00 / l0=1-1.7 / X If X is varied within the range of 2.7 to 10.8 times at this time, it represents the change in the refrigerant leakage rate in the liquid-side shut-off valve. 00 / l0 varies between 0.37 and 0.84 times. Therefore, in this case, as long as it is within 300 (cm) 3 The design range can be 0.37 to 0.84 times ( / min) or the maximum leakage rate during liquid-side shut-off can be selected.

[0137] Based on these results, it can be seen that if the refrigerant leakage rate in the gas-side shut-off valve is varied within the range of 1.6 to 2.7 times, then the change in the refrigerant leakage rate in the liquid-side shut-off valve will be l 00 / l0 varies in the range of 0.37 to 0.94 times.

[0138] Based on the above, the leakage rate of the gas-side shut-off valve during shut-off can be increased to the shut-off leakage rate specified in the above guidelines, i.e., 300 (cm³). 3 The leakage rate is within the range of 1.0 to 2.7 times that of the flow interruption rate ( / min). In this case, the leakage rate of the liquid-side shut-off valve during shut-off is within the range of 300 (cm³) specified in the above guidelines. 3 Set the range to less than 0.94 times the value of ( / min).

[0139] If the leakage rate of the gas-side shut-off valve and the liquid-side shut-off valve is changed within the above range, the sum of the refrigerant leakage rates of the gas-side shut-off valve and the liquid-side shut-off valve is equal to the sum of the refrigerant leakage rates under the condition that the gas-side shut-off valve and the liquid-side shut-off valve have the same valve clearance according to the above guidelines.

[0140] If further appropriate design or selection is made, then the leakage rate will be 300 (cm³) when the flow is interrupted as specified in the above guidelines. 3 When changing the leakage rate of the gas-side shut-off valve within the range of 1.6 to 2.7 times ( / min) during shut-off, the leakage rate during shut-off specified in the above guidelines is 300 (cm). 3 The leakage rate of the liquid-side shut-off valve can be changed within the range of 0.37 to 0.94 times ( / min) to adjust the leakage rate during shut-off.

[0141] (4-4) Next, it is assumed that a door is installed in a designated space (room) where an air conditioning unit is located. The case where a gap exists under the door and leaked refrigerant is discharged to the outside through this gap. Based on the above, the refrigerant leakage rate in the shut-off valve is set.

[0142] First, let G be the refrigerant discharge rate that allows the refrigerant to escape from the gap under the door to the outside of the room. d And calculate G d . (Equation 14): G d =ρ md ×V md ×A d (Equation 15): V md =C d ×(2×Δp d / ρ md ) 0.5 (Equation 16): Δp d =(ρ md -ρ a )×g×h s (Equation 17): ρ md =ρ mr +ρ ma (Equation 18): ρ mr =N / 100×(U r ×10 -3 ) / (24.5×10 -3 ) (Equation 19): ρ ma = (100-N) / 100×(U) a ×10 -3 ) / (24.5×10 -3 ) (Formula 20): N=LFL / S

[0143] As variables affecting the refrigerant discharge rate, examples include (4-4-1-A) and (4-4-1-B).

[0144] (4-4-1-A) Leakage Height (4-4-1-B) Safety factor of average refrigerant concentration in a room (specified space) relative to the LFL The leakage height is the location of the first portion of the specified space when refrigerant leaks into it. This is, for example, 2.2m when the side unit is installed on the ceiling, and for example, 0.6m when the side unit is installed on the floor (refer to IEC 60335-2-40:2016). The permissible average concentration is the average concentration of refrigerant leaked into the specified space, which is the refrigerant concentration within the range deemed impossible to burn when leaked into the specified space. The permissible average concentration is obtained by dividing the LFL by a safety factor. The refrigerant discharge rate is affected, for example, as shown in Table 4 below, depending on whether the safety factor is set to 4 or 2.

[0145] [Table 4] The refrigerant discharge rate Gd [kg / h] through the gap under the door and towards the outside.

[0146] (4-4-2) Next, the maximum leakage during the interruption state of the shut-off valve when there is a gap below the valve (Q) is calculated. max ) to perform calculations.

[0147] If the refrigerant discharged through the gap under the door to the outside of the room (a specified space) has a refrigerant discharge rate G d The refrigerant leakage rate G through the valve gap is greater than when the shut-off valve is set to shut-off state. r This allows the leakage rate during flow interruption to be set to be greater than 300 (cm). 3 / min). As described in (4-2-1) above, if the same maximum leakage rate (Q) is specified for both the gas-side shut-off valve and the liquid-side shut-off valve. max This is in contrast to the 300 (cm) specified in the guidelines of the Japan Refrigeration and Air Conditioning Manufacturers Association. 3 The multiplier R ( / min) is the same in all shut-off valves, including gas-side shut-off valves and liquid-side shut-off valves. (Equation 21): R = G d / G r (Equation 22): Q max =300×R

[0148] Here, it is assumed that before the shut-off valve is made to shut off, there is liquid refrigerant upstream of the shut-off valve on the liquid side line and gaseous refrigerant upstream of the shut-off valve on the gas side line. If equations (6) and (15) are substituted into equation (22), the following equation (23) is formed. (Equation 23): R=(ρ md ×V md ×A d ) / (Cr ×(2×ΔP r / ρ 1r ) 0.5 ×A v ×ρ 1rl +A v ×(2 / (λ+1)) ((λ+1) / 2(λ-1)) ×(λ×P 1r ×ρ 1rg ) 0.5 ).

[0149] If the ratio R related to each refrigerant is obtained using Equation 23, it is as shown in Table 5 below, for example.

[0150] [Table 5] Maximum permissible air leakage Q v The allowable ratio R

[0151] (4-4-3) The above explains the calculation of leakage during flow interruption, etc. Unless otherwise specified, the symbols used in the formulas have the following meanings (4-4-3-1) to (4-4-3-3).

[0152] (4-4-3-1) symbol A: Area (unit: m²) 2 ) C: Flow coefficient d: Equivalent diameter (unit: m) G: Mass flow rate (unit: kg·s) -1 ) g: acceleration due to gravity (unit: m·s²) -2 ) h: Leakage height (in meters) L: Lower flammability limit of refrigerant (LFL) (unit: kg·m³) -3 ) N: Refrigerant volume concentration (unit: vol%) P: Pressure (unit: Pa) Q: Volumetric flow rate (unit: m) 3 ·s -1 ) R: Valve leakage tolerance factor Δp: Pressure difference (unit: Pa) S: Safety factor U: Molecular weight of refrigerant v: velocity (unit: m·s) -1 ) X: The ratio of the refrigerant leakage rate in the liquid-side shut-off valve to the refrigerant leakage rate in the gas-side shut-off valve. Y: The ratio of the refrigerant leakage rate in the modified gas-side shut-off valve to the refrigerant leakage rate in the original gas-side shut-off valve.

[0153] (4-4-3-2) Greek letters κ: Specific heat ratio of air λ: Specific heat ratio of refrigerant ρ: Mass density (unit: kg·m³) -3 )

[0154] (4-4-3-3) Subscript a: air d: The gap under the door g: gas phase l: liquid phase m: The mixture of refrigerant and air r: refrigerant; s: refrigerant leak point v: shut-off valve G: Gas side pipeline L: Liquid side pipeline 1: Upstream 2: Downstream max: Allow 0: Before the change 00: After the change

[0155] (5) Characteristics of air conditioning units (5-1) The Japan Refrigeration and Air Conditioning Manufacturers Association's guideline, "Guidelines for Facilities to Ensure Safety in the Event of Refrigerant Leakage in Commercial Air Conditioners Using Slightly Flammable (A2L) Refrigerants" (JRA GL-16:2017), published on September 1, 2017, specifies the "Specifications for Safety Shut-off Valves" in Appendix A. Appendix A specifies that when the fluid is air and the pressure difference across the gas-side and liquid-side shut-off valves is 1 MPa, the leakage rate when the gas-side and liquid-side shut-off valves are shut off is 300 cm³. 3 / min).

[0156] Generally, gas-side shut-off valves tend to have larger orifice diameters, resulting in greater leakage under the same pressure differential. Conversely, liquid-side shut-off valves generally have smaller orifice diameters, leading to less leakage under the same pressure differential. The aforementioned guidelines require that, regardless of whether the shut-off valve is gas-side or liquid-side, leakage during shut-off be suppressed to 300 cm⁻¹. 3 / min) or less. However, designing or selecting the leakage rate of a gas-side shut-off valve with a valve orifice diameter larger than that of the liquid-side shut-off valve to be equal to the leakage rate of the liquid-side shut-off valve during shut-off would result in increased manufacturing or purchase costs.

[0157] Based on the leakage rate specified in the aforementioned guidelines during flow interruption, the refrigerant leakage rate assumed by the guidelines can be calculated. Furthermore, as... Figure 6 As shown, due to the different states of the refrigerant, the refrigerant leakage rate in the liquid-side shut-off valve is greater than that in the gas-side shut-off valve within the same valve gap. In other words, when the leakage amounts are the same in both the gas-side and liquid-side shut-off valves, more refrigerant will leak into the specified space because the refrigerant leakage rate in the liquid-side shut-off valve is faster than that in the gas-side shut-off valve.

[0158] In view of the above, in this embodiment, the leakage rate of the gas-side shut-off valves 68a, 68b, 68c, and 68d during shut-off is set to be greater than the leakage rate of the liquid-side shut-off valves 71a, 71b, 71c, and 71d during shut-off.

[0159] Therefore, even if the refrigerant leakage rate from gas-side shut-off valves 68a, 68b, 68c, and 68d increases, the refrigerant leakage rate from liquid-side shut-off valves 71a, 71b, 71c, and 71d will decrease, thus meeting the leakage rate requirements of the aforementioned guidelines during shut-off. This ensures safety and reduces the manufacturing cost of gas-side shut-off valves 68a, 68b, 68c, and 68d.

[0160] (5-2) In this embodiment, gas-side shut-off valves 68a, 68b, 68c, and 68d are designed with a leakage rate greater than 300 × R (cm) during shut-off. 3 A flow-stop valve with a flow rate of ( / min). On the other hand, for liquid-side flow-stop valves 71a, 71b, 71c, and 71d, a leakage rate of less than 300 × R (cm) during flow interruption is adopted. 3 The flow interruption valves ( / min) are designed to ensure safety and reduce the manufacturing cost of gas-side flow interruption valves 68a, 68b, 68c, and 68d. Here, when changing the leakage rate of the liquid-side and gas-side flow interruption valves during flow interruption, the R calculated in (4-4) is considered. Therefore, safety is ensured and the manufacturing cost of gas-side flow interruption valves 68a, 68b, 68c, and 68d is reduced.

[0161] (5-3) In the aforementioned guidelines, the leakage rate of both gas-side and liquid-side shut-off valves during shut-off is required to be suppressed to 300 (cm). 3 / min) or less. However, in this case, manufacturing or purchasing gas-side shut-off valves, which often have larger valve orifice diameters, would lead to increased costs. Therefore, in this embodiment, the refrigerant leakage rate in the gas-side shut-off valves 68a, 68b, 68c, 68d and the liquid-side shut-off valves 71a, 71b, 71c, 71d is in the range of 300×R(cm) where the refrigerant leakage rate is equal to the sum of the refrigerant leakage rates under the assumption of the same valve clearance for the gas-side and liquid-side shut-off valves according to the above guidelines. 3 The design or selection is based on changing the leakage rate of the gas-side shut-off valves 68a, 68b, 68c, 68d and the liquid-side shut-off valves 71a, 71b, 71c, 71d during shut-off.

[0162] When the gas-side shut-off valves 68a, 68b, 68c, and 68d are shut off according to the calculations shown in (4-3), the leakage rate is changed to 300 (cm). 3 When designed or selected in a manner that is 1.0 to 2.7 times ( / min), the leakage of liquid-side shut-off valves 71a, 71b, 71c, and 71d during shut-off is changed to 300 (cm). 3 The design or selection should be carried out in a manner that is less than 0.94 times the value of ( / min).

[0163] Furthermore, the R calculated in (4-4) is taken into account the leakage value when the gas-side shut-off valve and the liquid-side shut-off valve are shut off as selected as above.

[0164] Based on the above, when the gas-side shut-off valve is shut off, the leakage rate changes to 300 × R (cm). 3 When designed or selected in a manner that is 1.0 to 2.7 times ( / min), the leakage of liquid-side shut-off valves 71a, 71b, 71c, and 71d during shut-off is changed to 300×R(cm). 3 The design or selection method is less than 0.94 times the refrigerant leakage rate ( / min). In this case, the refrigerant leakage rate in the gas-side shut-off valves 68a, 68b, 68c, 68d and the liquid-side shut-off valves 71a, 71b, 71c, 71d is equal to the sum of the refrigerant leakage rates under the assumption of the same valve clearance for the gas-side shut-off valves 68a, 68b, 68c, 68d and the liquid-side shut-off valves 71a, 71b, 71c, 71d, according to the above guidelines.

[0165] In this way, even if the leakage of gas-side shut-off valves 68a, 68b, 68c, and 68d exceeds the 300 (cm³) specified in the aforementioned guidelines during shut-off, 3The leakage rate during flow interruption ( / min) can also be designed or selected in a manner that compensates for any excess leakage during flow interruption. This ensures safety and prevents increased costs associated with manufacturing or purchasing gas-side flow interruption valves 68a, 68b, 68c, and 68d.

[0166] With further appropriate design or selection, the leakage rate will be within 300 × R (cm) when the gas-side shut-off valves 68a, 68b, 68c, and 68d are shut off. 3 When the leakage rate is in the range of 1.6 to 2.7 times that of the liquid-side shut-off valves 71a, 71b, 71c, and 71d during shut-off, the leakage rate is within 300 × R (cm). 3 The liquid-side shut-off valves 71a, 71b, 71c, and 71d are designed or selected in a range of 0.37 to 0.94 times the flow rate ( / min).

[0167] (5-4) In air conditioning unit 1, taking into account the dimensions of the room (specified space) SP where its utilization side units 3a, 3b, 3c, and 3d are installed (the dimensions of the gap UC under the door DR, the ceiling height), the type of refrigerant (R32), and the installation location of the utilization side units 3a, 3b, 3c, and 3d (ceiling-mounted rather than floor-standing), the maximum leakage required for the shut-off valves is calculated using the methods described in (4-3) to (4-4-2) above, and the specifications of the liquid-side shut-off valves 71a, 71b, 71c, and 71d and the gas-side shut-off valves 68a, 68b, 68c, and 68d are determined. Specifically, as relative to 300 (cm 3 Calculate the allowable amount relative to the specification of 300 (cm) in Appendix A of the above guidelines by multiplying by R by ( / min). 3 To what extent can the baseline value of leakage during the interruption ( / min) increase? Next, determine the specific multiplier R value as shown in Table 5 above. Here, regarding R, if R32 is used as the refrigerant and the side units 3a, 3b, 3c, and 3d are installed on the ceiling of room SP, and the safety factor S is set to 4, then the multiplier R = 1.96 as shown in Table 5.

[0168] Consequently, in the air conditioning unit 1, the leakage rate is designed to reach 300 × 1.96 (cm²) during maximum flow interruption. 3 The specifications of liquid-side shut-off valves 71a, 71b, 71c, and 71d, and gas-side shut-off valves 68a, 68b, 68c, and 68d are determined in the following manner ( / min). Therefore, based on the reference value 300 (cm) 3Compared to the case where the specifications are determined by ( / min), the manufacturing or purchase costs of liquid-side shut-off valves 71a, 71b, 71c, 71d and gas-side shut-off valves 68a, 68b, 68c, 68d are reduced, and the introduction cost of air conditioning unit 1 using refrigerant (R32) that can prevent global warming is also suppressed.

[0169] Furthermore, in the air conditioning unit 1 where the specifications of such liquid-side shut-off valves 71a, 71b, 71c, 71d and gas-side shut-off valves 68a, 68b, 68c, 68d are already determined, based on the above... Figure 5 After the air conditioning unit 1 stops in step S7, the amount of refrigerant leaking from the valve gap between the liquid-side shut-off valve 71a and the gas-side shut-off valve 68a and flowing out into the room SP is also suppressed, and the refrigerant concentration in the room SP is suppressed to a value that is sufficiently low compared to LFL.

[0170] (5-5) Used to calculate the allowable amount relative to the specification of 300 (cm) in Appendix A of the above guidelines. 3 The extent to which the baseline value of leakage during the interruption ( / min) can be increased is determined by at least one of the permissible average concentration, leakage height, and type of refrigerant.

[0171] As described in (4-4-1-A), the leakage height refers to the location of the first part of the specified space SP when refrigerant leaks into the specified space SP, which is, for example, 2.2m when the side unit is installed on the ceiling and, for example, 0.6m when the side unit is installed on the ground (refer to IEC 60335-2-40:2016).

[0172] As described in (4-4-1-B), the permissible average concentration refers to the average concentration of refrigerant leaked into the specified space SP, which is the refrigerant concentration within the range where the refrigerant leaked into the specified space SP is deemed impossible to burn. The permissible average concentration is obtained by dividing the LFL by the safety factor.

[0173] The type of refrigerant refers to any of the following: flammable refrigerants classified as "2L" according to the American ANSI / ASHRAE 34-2013 standard; weakly flammable refrigerants classified as "2" according to the American ANSI / ASHRAE 34-2013 standard; and highly flammable refrigerants classified as "3" according to the American ANSI / ASHRAE 34-2013 standard.

[0174] The multiplier R is determined based on at least one of these factors, as shown in Table 5, specifically taking a value in the range of 1.02 to 11.98. From this, the leakage specifications that the gas-side and liquid-side shut-off valves must meet during shut-off can be determined.

[0175] (5-6) In addition, considering that the specified space SP does not have a gap UC under the door DR, the above-mentioned calculation of the multiplier R is not required. Instead, R is simply set to 1, and the leakage of gas-side shut-off valves 68a, 68b, 68c, 68d and liquid-side shut-off valves 71a, 71b, 71c, 71d during shut-off is calculated. This allows for the design or selection of gas-side shut-off valves 68a, 68b, 68c, 68d and liquid-side shut-off valves 71a, 71b, 71c, 71d.

[0176] (6) Variations (6-1) The air conditioning unit 1 described above is installed in a room (defined space SP) of a building or similar structure. However, if it is installed in the interior space of another building, the design or selection of the shut-off valve can be changed to meet the conditions of the defined space SP. For example, the shut-off valve can be appropriately designed or selected for various spaces such as the interior space of a factory, a kitchen, a data center, a computer room, and the interior space of a commercial facility.

[0177] (6-2) In the above description of the embodiments, R32 was used as an example of the refrigerant circulating in the refrigerant circuit 10 of the air conditioning unit 1. However, when using other flammable refrigerants, as mentioned above, the ratio R is calculated based on the differences in the molecular weight and LFL of the refrigerant, and the specifications of the liquid-side shut-off valves 71a, 71b, 71c, 71d and the gas-side shut-off valves 68a, 68b, 68c, 68d are designed or selected accordingly.

[0178] (6-3) In the above embodiment, as an example of the operation of the air conditioning unit 1 in the event of a refrigerant leak, it is shown that... Figure 5 The control flow shown can be modified, but other actions can also be performed in case of refrigerant leakage. For example, upon detecting a refrigerant leak, the following control can be performed: evacuation operation is initiated, followed by closing the shut-off valve.

[0179] (6-4) In the above embodiment, in steps S4 and S5, the utilization side units 3a, 3b, 3c, and 3d are operated in refrigeration mode, the opening of the heat source side expansion valve 25 is reduced, and the pressure of the refrigerant flowing to the utilization side units 3a, 3b, 3c, and 3d is lowered. However, this control is an example, and other controls may also be implemented.

[0180] For example, if a refrigerant leak is detected into the designated space SP of the utilization side unit 3a, the liquid-side shut-off valve 71a and the gas-side shut-off valve 68a of the relay unit 4a corresponding to the utilization side unit 3a may be immediately closed.

[0181] Alternatively, the following control method can be used: if refrigerant leakage into the designated space SP of the utilization side unit 3a is detected, all liquid-side shut-off valves 71a, 71b, 71c, 71d and gas-side shut-off valves 68a, 68b, 68c, 68d are closed to disconnect all utilization side units 3a, 3b, 3c, 3d from the heat source side unit 2, and the compressor 21 of the heat source side unit 2 is also stopped.

[0182] (6-5) In the above embodiments, examples of utilization side units include utilization side units 3a, 3b, 3c, and 3d, which are installed in the form of being embedded in the ceiling. However, even for other types of utilization side units, the design or selection method of the shut-off valve is the same. For example, the multiplier R of ceiling-suspended utilization side units, floor-standing utilization side units, and wall-mounted utilization side units fixed to the side wall can also be calculated using the above-described (Equation 23).

[0183] (6-6) Generally, gas-side shut-off valves tend to have larger orifice diameters, resulting in greater leakage when shutting off the flow under the same pressure differential. Conversely, liquid-side shut-off valves generally have smaller orifice diameters, resulting in less leakage when shutting off the flow under the same pressure differential. Therefore, in the above embodiments, it is assumed that the orifice diameters of gas-side shut-off valves 68a, 68b, 68c, and 68d are larger than those of liquid-side shut-off valves 71a, 71b, 71c, and 71d. However, even when the valve orifice diameters of the liquid-side shut-off valves 71a, 71b, 71c, and 71d are larger than or equal to the valve orifice diameters of the gas-side shut-off valves 68a, 68b, 68c, and 68d, by increasing the leakage rate of the gas-side shut-off valves 68a, 68b, 68c, and 68d during shut-off to a level greater than the leakage rate specified in the aforementioned guidelines, and by reducing the leakage rate of the liquid-side shut-off valves 71a, 71b, 71c, and 71d during shut-off to a level less than the leakage rate specified in the aforementioned guidelines, it is possible to suppress the refrigerant leakage rate below the rate assumed in the aforementioned guidelines. In addition to the configuration of each of the gas-side shut-off valves 68a, 68b, 68c, and 68d and the liquid-side shut-off valves 71a, 71b, 71c, and 71d, a configuration of two gas-side shut-off valves and one liquid-side shut-off valve can also be considered.

[0184] (6-7) In this embodiment, "air" is used as the gas in a single-phase gaseous state under standard conditions to evaluate the leakage rate of gas-side shut-off valves 68a, 68b, 68c, and 68d and liquid-side shut-off valves 71a, 71b, 71c, and 71d during shut-off. However, the gas used to evaluate the leakage rate during shut-off is not limited to "air," and can be any gas type including "nitrogen" that is in a single-phase gaseous state under standard conditions.

[0185] The embodiments of this disclosure have been described above, but it should be understood that various changes in form and detail can be made without departing from the spirit and scope of this disclosure as set forth in the claims. Symbol Explanation

[0186] 1. Air conditioning unit (refrigerant circulation system) 3aa, 3bb, 3cc, 3dd Part 1 (using the side loop) 10 Refrigerant Circuit 19 Control Department 68a, 68b, 68c, 68d Gas-side shut-off valves 71a, 71b, 71c, 71d Liquid-side flow interruption valves 79a, 79b, 79c, 79d Inspection Department (Refrigerant Leakage Inspection Department) SP specified space Existing technical documents Non-patent literature

[0187] Guidelines for safety measures in case of refrigerant leakage in commercial air conditioners using slightly flammable (A2L) refrigerant (JRAGL-16:2017; Japan Refrigeration and Air Conditioning Manufacturers Association); and Appendix A (specifies) the specifications for safety shut-off valves.

Claims

1. A refrigerant circulation device (1), wherein the refrigerant circulation device circulates a flammable refrigerant in a refrigerant circuit (10), characterized in that, include: Gas-side shut-off valves (68a, 68b, 68c, 68d) and liquid-side shut-off valves (71a, 71b, 71c, 71d) are provided on both sides of the first part (3aa, 3bb, 3cc, 3dd) of the refrigerant circuit. Detection units (79a, 79b, 79c, 79d) detect refrigerant leakage from the first portion into the designated space (SP); and When the detection unit detects a refrigerant leak from the first part into the designated space, the control unit (19) sets the gas-side shut-off valve and the liquid-side shut-off valve to a shut-off state. The leakage amount (cm 3 / min) of the gas-side shutoff valve and the liquid-side shutoff valve at the time of shutoff is the leakage amount of a gas in a single phase in a gaseous state under standard conditions when the pressure difference before and after shutoff is 1 MPa, and is the leakage amount of air at 20°C. The leakage rate of the gas-side shut-off valve during shut-off is greater than that of the liquid-side shut-off valve during shut-off. The leakage rate of the gas-side shut-off valve during shut-off is greater than 300 × R (cm). 3 / min), The leakage during the interruption of the liquid-side shut-off valve is less than 300 × R (cm). 3 / min), R=(ρ md ×V md ×A d ) / (C r ×(2×ΔP) r / r 1rl ) 0.5 ×A v ×r 1rl +A v ×(2 / (λ+1)) （（λ+1） / 2（λ-1）） ×(λ×P 1r ×r 1rg ) 0.5 ), among which, A v It is the valve gap cross-sectional area (m²) of the gas-side shut-off valve and the liquid-side shut-off valve under the shut-off state respectively. 2 ), ρ 1rl It is the density of the liquid refrigerant (kg / m³) 3 ), ρ 1rg It is the density of the gaseous refrigerant (kg / m³) 3 ), P 1r It refers to the refrigerant pressure (MPa) upstream of both the gas-side shut-off valve and the liquid-side shut-off valve, which is the refrigerant saturation pressure when the maximum external temperature of the building is set to 55°C. λ is the specific heat ratio of the refrigerant. ρ md It is the density (kg / m³) of the mixture of air and refrigerant as the gas mixture flows through the gap of the door separating the inside and outside of the specified space. 3 The mixed gas is a mixture of air and refrigerant, representing the permissible average concentration of refrigerant in the specified space after refrigerant leakage into the specified space. V md It is the velocity (m / s) of the mixture of air and refrigerant as it flows through the gap of the door separating the inside and outside of the designated space, wherein the mixture of air and refrigerant is the mixture of air and refrigerant reaching the permissible average concentration of refrigerant in the designated space after refrigerant leakage into the designated space. A d It is the area (m²) of the gap between the doors that separate the inside and outside of the specified space. 2 ), ΔP r It is the pressure difference (Pa) between the inside and outside of the hole where the refrigerant is leaking. It is the pressure difference between the saturation pressure of the refrigerant and atmospheric pressure when the maximum external temperature of the building is set at 55°C. C r It is the refrigerant flow coefficient when liquid refrigerant flows through the orifice at the location where refrigerant is leaking, and it is 0.

6.

2. The refrigerant circulation device as described in claim 1, characterized in that, The leakage rate of the gas-side shut-off valve during shut-off is 300 × R (cm). 3 The concentration of the substance is less than 1.0 to 2.7 times that of the substance (per min). The leakage rate of the liquid-side shut-off valve during shut-off is 300 × R (cm). 3 The value is less than 0.94 times that of ( / min).

3. The refrigerant circulation device as described in claim 1, characterized in that, The leakage rate of the gas-side shut-off valve during shut-off is 300 × R (cm). 3 The range of 1.6 to 2.7 times ( / min) The leakage rate of the liquid-side shut-off valve during shut-off is 300 × R (cm). 3 The range is 0.37 to 0.94 times that of ( / min).

4. The refrigerant circulation device according to any one of claims 1 to 3, characterized in that, The flammable refrigerant is: According to the American ANSI / ASHRAE 34-2013 standard, it is a "2L" class of slightly flammable refrigerant; Refrigerants classified as "Level 2" weakly flammable according to the US ANSI / ASHRAE 34-2013 standard; or It is classified as a "Level 3" highly flammable refrigerant according to the American ANSI / ASHRAE 34-2013 standard.

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