Heat source unit and air conditioner

Abstract

To propose a heat source unit of an air conditioner capable of suppressing occurrence of pressure abnormality in a refrigerant flow path due to a filled carbon dioxide refrigerant becoming supercritical.SOLUTION: A heat source unit is connected to a utilization unit, and constitutes an air conditioner. The heat source unit comprises a compressor, a heat source heat exchanger, a first closing valve, a second closing valve, a refrigerant flow path, and a refrigerant. The refrigerant flow path is a flow path in which the compressor, the heat source heat exchanger, the first closing valve, and the second closing valve are connected by refrigerant pipes. The refrigerant is filled in the refrigerant flow path. The refrigerant is carbon dioxide. An amount V1 (kg) of the refrigerant filled in the refrigerant flow path, a volume V2 (L) of the refrigerant flow path, and a design pressure P (MPa) of the refrigerant flow path satisfy the following relations: V1×a≤V2≤V1×b; a=0.078×P2-2.111×P+15.771; b=0.055×P2-1.768×P+16.144.SELECTED DRAWING: Figure 1

Description

Technical Field

[0004] ,

[0002] , , , Refrigerant storage container , ,

[0006] , , , , , , , , , A refrigerant storage container stores refrigerant. , , , , , , , ,

[0005] ,

[0003]

[0001] It relates to a heat source unit and an air conditioner.

Background Art

[0002] An air conditioner using carbon dioxide as a refrigerant is known. Patent Document 1 (Japanese Patent Application Laid-Open No. 2008-045769) discloses a method for filling a carbon dioxide refrigerant for the purpose of improving the efficiency of the installation work of an air conditioner.

[0003] In order to further improve the efficiency of the installation work of an air conditioner, a technique is known in which a refrigerant is pre-filled in a heat source unit (outdoor unit) at a manufacturing factory, and the refrigerant is filled into a refrigerant circuit by connecting the heat source unit and a utilization unit (indoor unit) at an installation location.

Summary of the Invention

Problems to be Solved by the Invention

[0004] When carbon dioxide is used as the refrigerant pre-filled in the outdoor unit, the refrigerant in the refrigerant flow path may become supercritical due to an increase in the outside air temperature. Since the pressure of the supercritical refrigerant rapidly increases, there is a risk of abnormal pressure occurring in the refrigerant flow path.

[0005] The present disclosure proposes a heat source unit of an air conditioner that suppresses the occurrence of abnormal pressure in a refrigerant flow path caused by the filled carbon dioxide refrigerant becoming supercritical.

Means for Solving the Problems

[0006] The heat source unit of the first aspect is connected to a utilization unit and constitutes an air conditioner. The heat source unit includes a compressor, a heat source heat exchanger, a first shut-off valve, a second shut-off valve, a refrigerant flow path, Refrigerant storage container and. The refrigerant flow path is a flow path in which the compressor, the heat source heat exchanger, the first shut-off valve, and the second shut-off valve are connected by refrigerant pipes. A refrigerant storage container stores refrigerant. The refrigerant is carbon dioxide.

[0007] When the volume of the refrigerant flow path in the heat source unit is V2 (L) and the volume of the refrigerant storage container is V3 (L), 0.4 × V2 ≤ V3 < 0.9 × V2 It satisfies the relationship.

[0008] The heat source unit in the second perspective is the heat source unit in the first perspective, where V2(L) is the volume of the refrigerant flow path (20) that is closed from the outside by the first shut-off valve and the second shut-off valve.

[0009] A heat source unit according to the third aspect is a heat source unit according to the first or second aspect, wherein the refrigerant storage container includes a first refrigerant storage container (27) provided on the suction side of the compressor (21) in the refrigerant flow path (20).

[0010] The heat source unit of the fourth aspect is the heat source unit of the third aspect, comprising a refrigerant amount adjustment unit (28) connected to a refrigerant flow path, wherein the refrigerant amount adjustment unit (28) has a second refrigerant storage container (28a).

[0011] The heat source unit of the fifth aspect is the heat source unit of the fourth aspect, wherein the second refrigerant storage container (28a) has a first port (28aa) connected to the discharge side of the compressor (21) and a second port connected to the suction side of the compressor.

[0012] The heat source unit of the sixth perspective is the heat source unit of the fifth perspective, wherein the refrigerant amount adjustment unit (28) is provided with a solenoid valve (28d) installed in a pipe (20b) connected to the discharge side of the compressor (21). When the solenoid valve (28d) is open, it supplies refrigerant to the second refrigerant storage container (28a) via the first port (28aa).

[0013] The heat source unit of the seventh aspect is the heat source unit of the fifth or sixth aspect, wherein the refrigerant amount adjustment unit (28) includes an expansion mechanism (28e) provided between the suction side of the compressor (21) and the second refrigerant storage container (28a). The expansion mechanism (28e) adjusts the flow rate of the refrigerant flowing from the second port (28ab) to the suction side of the compressor (21) and reduces the pressure of the refrigerant.

[0014] The heat source unit of the eighth perspective is any of the heat source units of the first to seventh perspectives, and further comprises a flow path switching mechanism for switching the direction in which the refrigerant flows in the refrigerant flow path. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram of the air conditioning system 1 equipped with a heat source unit 2 according to the first embodiment. [Figure 2] This is the Mollier diagram for R32. [Figure 3] This is the Mollier diagram for carbon dioxide. [Figure 4] This is a schematic diagram of the air conditioning system 1a equipped with a heat source unit 2a according to the second embodiment. [Modes for carrying out the invention]

[0016] <First Embodiment> (1) Overall structure FIG. 1 is a schematic configuration diagram of an air conditioner 1 including a heat source unit 2 according to the first embodiment. The air conditioner 1 performs a vapor compression refrigeration cycle operation and executes an air conditioning operation (cooling operation and heating operation) in an air conditioning target space (not shown) such as a room. The air conditioner 1 includes one heat source unit 2, one utilization unit 3, and first connection pipes 6 and second connection pipes 7 that connect the heat source unit 2 and the utilization unit 3. The heat source unit 2, the utilization unit 3, and the connection pipes 6 and 7 connected to each other constitute a refrigerant circuit 10. The refrigerant filled in the refrigerant circuit 10 is carbon dioxide. Hereinafter, the first connection pipes 6 and the second connection pipes 7 are also collectively referred to as connection pipes 6 and 7.

[0017] Although details will be described later, the refrigerant filled in the refrigerant circuit 10 is filled in the heat source unit 2 at a manufacturing factory or the like. At the installation location or the like of the air conditioner 1, when the heat source unit 2 and the utilization unit 3 are connected via the connection pipes 6 and 7, the refrigerant filled in the heat source unit 2 is filled in the refrigerant circuit 10.

[0018] (2) Detailed Configuration (2-1) Utilization Unit The utilization unit 3 is installed in the air conditioning target space. The utilization unit 3 has a utilization-side refrigerant flow path 30 that constitutes a part of the refrigerant circuit 10. The utilization-side refrigerant flow path 30 includes a utilization-side heat exchanger 31.

[0019] (2-1-1) Utilization-Side Heat Exchanger The utilization-side heat exchanger 31 causes heat exchange between the refrigerant flowing inside and the air in the air conditioning target space. One end of the utilization-side heat exchanger 31 is connected to the first connection pipe 6 via a refrigerant pipe 30a. The other end of the utilization-side heat exchanger 31 is connected to the second connection pipe 7 via the refrigerant pipe 30a.

[0020] (2-2) Heat Source Unit The heat source unit 2 is installed outside the space to be air-conditioned (e.g., outdoors). The heat source unit 2 has a heat source refrigerant flow path 20 that constitutes part of the refrigerant circuit 10. The heat source refrigerant flow path 20 includes a compressor 21, a flow path switching mechanism 22, a heat source heat exchanger 23, a heat source expansion mechanism 24, a first shut-off valve 25, a second shut-off valve 26, and an accumulator 27. The compressor 21, the flow path switching mechanism 22, the heat source heat exchanger 23, the heat source expansion mechanism 24, the first shut-off valve 25, the second shut-off valve 26, and the accumulator 27 are connected to each other via refrigerant piping 20a. The heat source refrigerant flow path 20 is an example of a refrigerant flow path.

[0021] (2-2-1) Compressor The compressor 21 draws in low-pressure refrigerant from the refrigeration cycle through the suction pipe 21a, compresses the refrigerant using a compression mechanism (not shown), and discharges the compressed refrigerant as high-pressure refrigerant through the discharge pipe 21b. In this embodiment, the heat source unit 2 has only one compressor 21, but the number of compressors 21 is not limited to one and may be multiple. The starting, stopping, and capacity control of the compressor 21 can be performed by a control unit (not shown).

[0022] (2-2-2) Flow path switching mechanism The flow path switching mechanism 22 switches the direction of refrigerant flow, changing the state of the refrigerant circuit 10 between a first state and a second state. When the refrigerant circuit 10 is in the first state, the heat source heat exchanger 23 functions as a refrigerant evaporator, and the user-side heat exchanger 31 functions as a refrigerant evaporator. When the refrigerant circuit 10 is in the second state, the heat source heat exchanger 23 functions as a refrigerant evaporator, and the user-side heat exchanger 31 functions as a refrigerant evaporator. The state of the flow path switching mechanism 22 can be changed by a control unit (not shown).

[0023] In this embodiment, the flow path switching mechanism 22 is a four-way switching valve having four ports P1, P2, P3, and P4. Port P1 is connected to one end of the heat source heat exchanger 23. Port P2 is connected to the discharge pipe 21b of the compressor 21. Port P3 is connected to the accumulator 27. Port P4 is connected to the second shut-off valve 26. In the first state, port P1 communicates with port P2, and port P3 communicates with port P4. In the second state, port P1 communicates with port P3, and port P2 communicates with port P4.

[0024] The flow path switching mechanism 22 is not limited to a four-way switching valve. For example, the flow path switching mechanism 22 may be configured by combining multiple solenoid valves and refrigerant pipes so as to achieve the switching of the refrigerant flow direction as described above.

[0025] (2-2-3) Heat source heat exchanger The heat source heat exchanger 23 performs heat exchange between the refrigerant flowing inside and the air (heat source air) at the installation location of the heat source unit 2. One end of the heat source heat exchanger 23 is connected to port P1 of the flow path switching mechanism 22. The other end of the heat source heat exchanger 23 is connected to the heat source expansion mechanism 24.

[0026] (2-2-4) Thermal Expansion Mechanism The heat source expansion mechanism 24 controls the flow rate of the refrigerant flowing through the heat source refrigerant flow path 20 and reduces the pressure of the refrigerant by controlling its opening degree. One end of the heat source expansion mechanism 24 is connected to the heat source heat exchanger 23. The other end of the heat source expansion mechanism 24 is connected to the first shut-off valve 25. The opening degree of the heat source expansion mechanism 24 can be controlled by a control unit (not shown).

[0027] (2-2-5) First shut-off valve and second shut-off valve The first shut-off valve 25 is a valve provided at the connection point between the heat source refrigerant flow path 20 and the first connecting pipe 6. When the first shut-off valve 25 is closed, the flow of refrigerant between the heat source refrigerant flow path 20 and the first connecting pipe 6 is restricted. The first shut-off valve 25 is, for example, a valve that is operated manually. In this embodiment, the first shut-off valve 25 is a three-way valve equipped with a service port that can communicate with the outside of the refrigerant circuit 10.

[0028] The second shut-off valve 26 is a valve provided at the connection point between the heat source refrigerant flow path 20 and the second connecting pipe 7. When the second shut-off valve 26 is closed, the flow of refrigerant between the heat source refrigerant flow path 20 and the second connecting pipe 7 is restricted. The second shut-off valve 26 is, for example, a manually operated valve. In this embodiment, the second shut-off valve 26 is a three-way valve equipped with a service port that can communicate with the outside of the refrigerant circuit 10.

[0029] The first shut-off valve 25 and the second shut-off valve 26 are closed when shipped from the manufacturing plant and are opened when the installation of the air conditioning unit 1 is completed. After the installation is completed, the first shut-off valve 25 and the second shut-off valve 26 are normally kept open.

[0030] (2-2-6) Accumulator The accumulator 27 is a container that stores excess refrigerant generated in the refrigerant circuit 10 in response to fluctuations in the operating load of the utilization unit 3. It is located between the port P3 of the flow path switching mechanism 22 and the suction pipe 21a of the compressor 21. The accumulator 27 is an example of a refrigerant storage container.

[0031] (2-2-7) Relationship between the amount of refrigerant filled and the volume of the heat source refrigerant flow path The heat source unit 2 is in a standalone state, not connected to either the utilization unit 3 or the connecting pipes 6 and 7, with refrigerant filling the heat source refrigerant flow path 20. The amount of refrigerant filling the heat source refrigerant flow path 20 is the amount that, when filled into the refrigerant circuit 10, allows the air conditioning system 1 to perform a refrigeration cycle operation with the required capacity. More specifically, the amount of refrigerant V1 (kg) filling the heat source refrigerant flow path 20 satisfies the following relationship (Equation 1) between the volume V2 (L) of the heat source refrigerant flow path 20 and the design pressure P (MPa) of the heat source refrigerant flow path 20. (Math 1) V1 × a ≤ V2 ≤ V1 × b ... (1) a=0.078×P2-2.111×P+15.771 ···(2) b=0.055×P2-1.768×P+16.144 (3)

[0032] V2, which is the volume of the heat source refrigerant flow path 20, is the volume of the space that is closed from the outside by the first shut-off valve 25 and the second shut-off valve 26, where the compressor 21, the flow path switching mechanism 22, the heat source heat exchanger 23, the heat source expansion mechanism 24, the first shut-off valve 25, the second shut-off valve 26, and the accumulator 27 are connected to each other using refrigerant piping 20a.

[0033] In this embodiment, the design pressure P (MPa) of the heat source refrigerant flow path 20 is 10 MPa or more and 14 MPa or less.

[0034] Furthermore, the volume V3 (L) of the accumulator 27 may satisfy the following relationship (Equation 2) with respect to the volume V2 (L) of the heat source refrigerant flow path 20. (Math 2) 0.4 × V2 ≤ V3 < 0.9 × V2

[0035] The refrigerant is typically filled into the heat source refrigerant flow path 20 at the manufacturing plant of the heat source unit 2. After the refrigerant is filled, the first shut-off valve 25 and the second shut-off valve are closed, which prevents the refrigerant from leaking out of the heat source refrigerant flow path 20 between the time the heat source unit 2 leaves the manufacturing plant and the time the air conditioning system 1 is installed.

[0036] (2-3) Connecting piping The connecting pipes 6 and 7 are connecting pipes that link the heat source refrigerant flow path 20 and the user-side refrigerant flow path 30 (in other words, the heat source unit 2 and the user unit 3). The refrigerant circuit 10 is formed by connecting the heat source refrigerant flow path 20, the user-side refrigerant flow path 30, the first connecting pipe 6, and the second connecting pipe 7.

[0037] The lengths of the connecting pipes 6 and 7 can be arbitrarily changed according to the distance between the heat source unit 2 and the utilization unit 3, with a maximum length of approximately 100m.

[0038] (3) Operation of the air conditioning system Next, we will explain the operation of each part of the air conditioning system 1 during air conditioning operation.

[0039] (3-1) Cooling operation During cooling operation, the flow path switching mechanism 22 is controlled to the first state. In addition, the opening degree of the heat source expansion mechanism 24 is controlled according to the load of the user-side heat exchanger 31.

[0040] In this state, when the compressor 21 is started, the low-pressure refrigerant in the refrigeration cycle is drawn in through the suction pipe 21a of the compressor 21, compressed, and discharged as high-pressure refrigerant from the discharge pipe 21b. The high-pressure refrigerant discharged from the compressor 21 is sent to the heat source heat exchanger 23 via the flow path switching mechanism 22, where it is cooled by heat exchange with the heat source air. In other words, the heat source heat exchanger 23 functions as a heat radiator. The high-pressure refrigerant cooled in the heat source heat exchanger 23 is depressurized as it passes through the heat source expansion mechanism 24, becoming a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant is sent to the utilization unit 3 via the first shut-off valve 25 and the first connecting pipe 6. The refrigerant sent to the utilization unit 3 is heated by heat exchange with the air in the conditioned space in the utilization-side heat exchanger 31, resulting in evaporation and becoming a low-pressure refrigerant. In other words, the utilization-side heat exchanger 31 functions as an evaporator. The low-pressure refrigerant heated in the user-side heat exchanger 31 is sent to the heat source unit 2 via the second connecting pipe 7, and flows into the accumulator 27 via the second shut-off valve 26 and the flow path switching mechanism 22. The low-pressure refrigerant that flows into the accumulator 27 is then drawn back into the compressor 21.

[0041] (3-2) Heating operation During heating operation, the flow path switching mechanism 22 is controlled to the second state. In addition, the heat source expansion mechanism 24 is controlled to an opening degree that reduces the pressure to a level that allows the refrigerant to be evaporated in the heat source heat exchanger 23.

[0042] In this state, when the compressor 21 is started, the low-pressure refrigerant in the refrigeration cycle is drawn in through the suction pipe 21a of the compressor 21, compressed, and discharged as high-pressure refrigerant from the discharge pipe 21b. The high-pressure refrigerant discharged from the compressor 21 is sent to the utilization unit 3 via the flow path switching mechanism 22, the second shut-off valve 26, and the second connecting pipe 7. The high-pressure refrigerant sent to the utilization unit 3 is cooled by heat exchange with the air in the space to be air-conditioned in the utilization-side heat exchanger 31. In other words, the utilization-side heat exchanger 31 functions as a heat radiator. The high-pressure refrigerant cooled in the utilization-side heat exchanger 31 is sent to the heat source unit 2 via the first connecting pipe 6. The refrigerant sent to the heat source unit 2 passes through the first shut-off valve 25 and then, as it passes through the heat source expansion mechanism 24, is depressurized to become a low-pressure gas-liquid two-phase refrigerant and flows into the heat source heat exchanger 23. The low-pressure gas-liquid two-phase refrigerant flowing into the heat source heat exchanger 23 is heated by heat exchange with the heat source air, evaporating and becoming low-pressure refrigerant again. In other words, the heat source heat exchanger 23 functions as an evaporator. The low-pressure refrigerant heated in the heat source heat exchanger 23 flows into the accumulator 27 via the flow path switching mechanism 22. The low-pressure refrigerant that flows into the accumulator 27 is then drawn back into the compressor 21.

[0043] (4) Refrigerant charging method Next, we will explain the method for filling the refrigerant circuit 10 with refrigerant during the installation of the air conditioning system 1.

[0044] The installation work for the air conditioning system 1 includes the steps of installing the heat source unit 2 and the utilization unit 3 at their respective installation locations, and connecting the heat source refrigerant flow path 20 and the utilization side refrigerant flow path 30 via connecting pipes 6 and 7.

[0045] In the air conditioning system 1, the heat source refrigerant flow path 20 of the heat source unit 2 is filled with refrigerant. Therefore, the heat source refrigerant flow path 20 and the user-side refrigerant flow path 30 are connected via connecting pipes 6 and 7, and the refrigerant filled in the heat source unit 2 is sent to the user unit 3 through the connecting pipes 6 and 7, thereby filling the refrigerant circuit 10. Thus, in the installation work of the air conditioning system 1, the refrigerant is filled in the refrigerant circuit 10 by connecting the heat source refrigerant flow path 20 and the user-side refrigerant flow path 30 via connecting pipes 6 and 7, eliminating the need to fill the refrigerant circuit 10 from the outside. Therefore, the air conditioning system 1 equipped with the heat source unit 2 allows for efficient installation work.

[0046] (5) Characteristics (5-1) The heat source unit 2 is connected to the utilization unit 3 and constitutes the air conditioning system 1. The heat source unit 2 comprises a compressor 21, a heat source heat exchanger 23, a first shut-off valve 25, a second shut-off valve 26, a heat source refrigerant flow path 20, and a refrigerant. The heat source refrigerant flow path 20 is a flow path through which the compressor 21, the heat source heat exchanger 23, the first shut-off valve 25, and the second shut-off valve 26 are connected by refrigerant piping 20a. The refrigerant is filled into the heat source refrigerant flow path 20. The refrigerant is carbon dioxide.

[0047] The amount of refrigerant V1 (kg) filled in the heat source refrigerant flow path 20, the volume V2 (L) of the heat source refrigerant flow path 20, and the design pressure P (MPa) of the heat source refrigerant flow path 20 satisfy the following relationship (Equation 1). (Math 1) V1 × a ≤ V2 ≤ V1 × b ... (1) a=0.078×P2-2.111×P+15.771 ···(2) b=0.055×P2-1.768×P+16.144 (3)

[0048] Carbon dioxide refrigerants are known to exhibit a more rapid increase in pressure when supercritical compared to other refrigerants. Figure 2 shows the Mollier diagram for R32. Figure 3 shows the Mollier diagram for carbon dioxide.

[0049] As shown in Figure 2, R32, which is in a gas-liquid two-phase state, can maintain this state even at 70°C, which is the upper limit of the refrigerant temperature that can rise due to ambient temperature and direct sunlight, as is normally expected in a non-operating heat source unit, with a pressure of approximately 5.0 MPa.

[0050] In contrast, as shown in Figure 3, carbon dioxide in a gas-liquid two-phase state becomes supercritical when it exceeds the critical point CP (critical temperature: approximately 31.1°C, critical pressure: approximately 7.38 MPa). When carbon dioxide becomes supercritical, for example, if its density is 500 kg / m³, the pressure, which was approximately 9 MPa (Pr1) at 40°C, rapidly increases to approximately 14.9 MPa (Pr2) at 70°C, which is the upper limit of the refrigerant temperature that is normally expected to rise due to ambient temperature and direct sunlight. As a result, in the heat source refrigerant flow path 20 filled with carbon dioxide refrigerant, a pressure anomaly occurs where the pressure of the supercritical refrigerant exceeds the design pressure P of the heat source refrigerant flow path 20 due to rising ambient temperature, etc., which may cause damage to various parts that make up the heat source refrigerant flow path 20.

[0051] In the heat source unit 2, the relationship between the refrigerant charge amount V1 and the volume V2 of the heat source refrigerant flow path 20 is set based on (Equation 1) obtained from the temperature-pressure relationship between carbon dioxide refrigerant and the assumed refrigerant temperature range. Here, the assumed refrigerant temperature range is 50°C to 70°C. 50°C is the temperature expected in a warehouse or other location where the heat source unit 2 is stored, especially during the summer (for example, the temperature inside the warehouse). 70°C is the upper limit of the refrigerant temperature that rises due to ambient temperature, direct sunlight, etc., in a warehouse or other location where the heat source unit 2 is stored.

[0052] Equation 1(2) calculates the specific volume at which damage due to pressure rise is suppressed in each part of the heat source refrigerant flow path 20, where the refrigerant temperature is 50°C and the design pressure is P.

[0053] Equation 1(3) determines the specific volume at which the heat source refrigerant flow path 20, which is at the design pressure P, becomes excessively large when the refrigerant temperature is 70°C, thereby suppressing the enlargement of the heat source refrigerant flow path 20.

[0054] When the design pressure P of the heat source refrigerant flow path 20 is arbitrarily selected for any refrigerant amount V1, the volume V2 of the heat source refrigerant flow path 20 is set to be greater than or equal to the volume V1 × a calculated on the left side of Equation 1 (1), and less than or equal to the volume V1 × b calculated on the right side of Equation 1 (1). This suppresses the enlargement of the heat source refrigerant flow path 20 while suppressing the occurrence of pressure abnormalities in the refrigerant flow path caused by the carbon dioxide refrigerant filling the heat source refrigerant flow path 20 becoming supercritical.

[0055] Therefore, the heat source unit 2 suppresses the enlargement of the heat source refrigerant flow path 20 while also suppressing the occurrence of pressure abnormalities in the refrigerant flow path caused by the carbon dioxide refrigerant filling the heat source refrigerant flow path 20 becoming supercritical.

[0056] (5-2) The design pressure P is between 10 MPa and 14 MPa.

[0057] When the refrigerant pressure is 14 MPa, the point calculated by Equation 1(2) is the first point Pa in Figure 3, and the point calculated by Equation 1(3) is the second point Pb in Figure 3. Furthermore, when the refrigerant pressure is 10 MPa, the point calculated by Equation 1(2) is the third point Pc in Figure 3, and the point calculated by Equation 1(3) is the fourth point Pd in ​​Figure 3. Then, when the volume V2 of the heat source refrigerant flow path 20 satisfies Equation 1(1), the refrigerant filled in the heat source refrigerant flow path 20 is included in the area shown by the hatched area in Figure 3.

[0058] (5-3) It is preferable that the volume V3 (L) of the accumulator 27 satisfies the following relationship (Equation 2) with respect to the volume V2 (L) of the heat source refrigerant flow path 20. (Math 2) 0.4 × V2 ≤ V3 < 0.9 × V2

[0059] In the heat source unit 2, since refrigerant can be stored not only in the heat source refrigerant flow path 20 but also in the accumulator 27, a sufficient volume V2 can be secured, effectively suppressing the occurrence of pressure abnormalities in the refrigerant flow path.

[0060] (5-4) The heat source unit 2 further includes a flow path switching mechanism 22 that switches the direction in which the refrigerant flows in the heat source refrigerant flow path 20, and an accumulator 27 that stores the refrigerant.

[0061] The accumulator 27 not only stores the filled refrigerant, but can also store excess refrigerant that is generated due to fluctuations in the operating load between cooling and heating operations.

[0062] (6) Variant (6-1) Variation A1 The air conditioning system 1 may be a multi-type air conditioning system consisting of one heat source unit 2 and multiple utilization units 3.

[0063] (6-2) Modified example A2 The air conditioning system 1 may not have a flow path switching mechanism 22 and may be capable of performing only either cooling or heating operation as the air conditioning operation.

[0064] (6-3) Modified example A3 The installation work of the air conditioning system 1 may further include a step of additional refrigerant charging after the step of connecting the heat source unit 2 and the utilization unit 3 via connecting pipes 6 and 7. The additional refrigerant charging step is performed when the length of the connecting pipes 6 and 7 used to connect the heat source unit 2 and the utilization unit 3 is equal to or greater than a predetermined first length L1.

[0065] As described above, the heat source refrigerant flow path 20 of the heat source unit 2 is filled with an amount of refrigerant (hereinafter also referred to as the required amount of refrigerant) that, when filled into the refrigerant circuit 10, allows the air conditioner 1 to perform a refrigeration cycle operation with the required capacity. However, when the heat source unit 2 and the utilization unit 3 are located far apart from each other, it becomes necessary to connect the heat source unit 2 and the utilization unit 3 using longer-than-usual connecting pipes 6 and 7. In such cases, the capacity of the refrigerant circuit 10 becomes larger than initially assumed, and the amount of refrigerant filled into the heat source refrigerant flow path 20 of the heat source unit 2 may become insufficient compared to the required amount of refrigerant. Therefore, in the air conditioner 1 according to modification A3, the maximum length for which the amount of refrigerant filled into the heat source refrigerant flow path 20 does not fall below the required amount of refrigerant is set in advance as the first length L1. In other words, the length of the connecting pipes 6 and 7 is changed according to the installation positions of the heat source unit 2 and the utilization unit 3. The connecting pipes 6 and 7 have a first length L1 as one of their length variations, which eliminates the need for additional refrigerant charging into the refrigerant circuit 10 formed by the connection of the heat source unit 2 and the utilization unit 3 via the connecting pipes 6 and 7. The heat source unit 2 is filled with an amount of refrigerant corresponding to the amount of refrigerant required in the refrigerant circuit 10 when the connecting pipes 6 and 7 are of the first length L1.

[0066] This allows workers performing the installation of the air conditioning system 1 to determine whether the lengths of the connecting pipes 6 and 7 required for the installation of the air conditioning system 1 are equal to or greater than the first length L1.

[0067] If the lengths of the connecting pipes 6 and 7 are shorter than the first length L1, the amount of refrigerant filled in the heat source refrigerant flow path 20 is greater than the required amount, so the additional refrigerant filling process is unnecessary. Therefore, the additional refrigerant filling process is not performed, and after the process of connecting the heat source unit 2 and the utilization unit 3 via the connecting pipes 6 and 7 is completed, the installation work is finished. In other words, the amount of refrigerant filled in the heat source refrigerant flow path 20 of the heat source unit 2 is greater than the required amount of refrigerant in the refrigerant circuit 10 formed by connecting the heat source unit 2 and the utilization unit 3 via the connecting pipes 6 and 7 when the connecting pipes 6 and 7 are shorter than the first length L1.

[0068] On the other hand, if the length of the connecting pipes 6 and 7 is greater than or equal to the first length L1, the amount of refrigerant filled in the heat source refrigerant flow path 20 is insufficient, and an additional refrigerant filling process is required. Therefore, an additional refrigerant filling process is performed, and an amount of refrigerant corresponding to the length of the connecting pipes 6 and 7 is added to the refrigerant circuit 10. The refrigerant is added, for example, from the service port of the first shut-off valve 25 or the second shut-off valve 26.

[0069] If the air conditioning system 1 is a paired type air conditioning system comprising one heat source unit 2 and one utilization unit 3, the first length L1 is, for example, about 15 m. If the air conditioning system 1 is a multi-type air conditioning system comprising one heat source unit 2 and multiple utilization units 3, the first length L1 is, for example, about 30 m to 70 m.

[0070] (6-4) Modification A4 The heat source refrigerant flow path 20 of the heat source unit 2 may further have a receiver for storing excess refrigerant. In this case, V3 includes the volume of the receiver in addition to the volume of the accumulator 27.

[0071] <Second Embodiment> (1) Overall structure The heat source unit 2a according to the second embodiment will be described, focusing on the differences from the heat source unit 2. Like the heat source unit 2, the heat source unit 2a is connected to one or more user units 3 using the first connecting pipe 6 and the second connecting pipe 7 to constitute the air conditioning system 1a. In the following, features that are the same as or corresponding to the first embodiment are denoted by the same reference numerals and their description is omitted. Figure 4 is a schematic diagram of the air conditioning system 1a equipped with the heat source unit 2a according to the second embodiment.

[0072] The main difference between the heat source unit 2a and the heat source unit 2 is that the heat source unit 2a is further equipped with a refrigerant quantity adjustment unit 28. The refrigerant quantity adjustment unit 28 stores the refrigerant to be filled during the installation work of the air conditioning system 1a, and also stores excess refrigerant that is generated in the refrigerant circuit 10 in response to fluctuations in the operating load of the utilization unit 3. The refrigerant quantity adjustment unit 28 is included in the heat source refrigerant flow path 20 of the heat source unit 2a. As a result, the heat source unit 2a is filled with more refrigerant in the heat source refrigerant flow path 20 than the heat source unit 2. The refrigerant quantity adjustment unit 28 includes a refrigerant storage container 28a, a pressure regulating valve 28b, a check valve 28c, a solenoid valve 28d, and an expansion mechanism 28e.

[0073] (2) Detailed configuration (2-1) Refrigerant storage container The refrigerant storage container 28a is a container (tank) that stores at least a portion of the refrigerant that fills the heat source refrigerant flow path 20, and also stores excess refrigerant generated in the refrigerant circuit 10. The refrigerant storage container 28a has a first port 28aa and a second port 28ab. The refrigerant storage container 28a is an example of a refrigerant storage container.

[0074] The first port 28aa is a port provided for adjusting the pressure inside the refrigerant storage container 28a. The first port 28aa is connected to the refrigerant piping 20a, which connects to port P3 of the flow path switching mechanism 22 and the accumulator 27, and to the discharge pipe 21b of the compressor 21 via pressure adjustment piping 20b.

[0075] The second port 28ab is a port through which refrigerant flows. The second port 28ab is connected to the suction pipe 21a of the compressor 21 via the refrigerant piping 20a.

[0076] (2-2) Pressure regulating valve The pressure regulating valve 28b is a valve that prevents the pressure of the refrigerant in the refrigerant storage container 28a from becoming too high. The pressure regulating valve 28b is installed in the pressure regulating pipe 20b connected to the refrigerant pipe 20a that connects port P3 of the flow path switching mechanism 22 to the accumulator 27. The pressure regulating valve 28b opens when the pressure of the refrigerant in the refrigerant storage container 28a exceeds a predetermined value, releasing the high-pressure refrigerant to the accumulator 27.

[0077] (2-3) Check valves and solenoid valves The check valve 28c and solenoid valve 28d are valves used to increase the pressure of the refrigerant in the refrigerant storage container 28a. The check valve 28c and solenoid valve 28d are installed in the pressure regulating piping 20b connected to the discharge pipe 21b of the compressor 21. When the solenoid valve 28d opens during the operation of the compressor 21, the high-pressure refrigerant discharged from the compressor 21 is sent to the refrigerant storage container 28a. The solenoid valve 28d is typically opened when filling the refrigerant circuit 10 with refrigerant from the refrigerant storage container 28a. The check valve 28c prevents refrigerant from flowing from the refrigerant storage container 28a to the discharge pipe 21b of the compressor 21. The opening and closing of the solenoid valve 28d can be performed by a control unit (not shown). Note that the check valve 28c and solenoid valve 28d may be a flow rate adjustment mechanism including an electric valve.

[0078] (2-4) Expansion mechanism The expansion mechanism 28e adjusts the flow rate of refrigerant flowing through the refrigerant piping 20a connecting the suction pipe 21a of the compressor 21 and the refrigerant storage container 28a, and also reduces the pressure of the refrigerant. The opening degree of the expansion mechanism 28e can be controlled by a control unit (not shown).

[0079] (2-5) Relationship between the amount of refrigerant charged and the volume of the heat source refrigerant flow path Similar to the heat source unit 2, the heat source unit 2a is also in a standalone state, not connected to either the utilization unit 3 or the connecting pipes 6 and 7, with refrigerant filling the heat source refrigerant flow path 20. The amount of refrigerant filling the heat source refrigerant flow path 20 is the amount that, when filled into the refrigerant circuit 10, allows the air conditioning system 1a to perform a refrigeration cycle operation with the required capacity. In this case, the amount of refrigerant V1 (kg) filling the heat source refrigerant flow path 20 satisfies the relationship (Equation 1) above between the volume V2 (L) of the heat source refrigerant flow path 20 and the design pressure P (MPa) of the heat source refrigerant flow path 20.

[0080] Furthermore, in the heat source unit 2a, V3 includes the volume of the accumulator 27 as well as the volume of the refrigerant storage container 28a. V3(L) satisfies the relationship (Equation 2) above with respect to the volume V2(L) of the heat source refrigerant flow path 20.

[0081] (3) Operation of the air conditioning system In both cooling and heating operations, the expansion mechanism 28e and the solenoid valve 28d are controlled to be fully open or nearly fully open when refrigerant is being supplied. When refrigerant supply ends, the expansion mechanism 28e and the solenoid valve 28d are controlled to be fully closed or nearly fully closed. This ensures that the necessary refrigerant is supplied to the refrigerant circuit 10 of the air conditioning unit 1a. In addition, any surplus refrigerant that was pre-filled in the refrigerant storage container 28a is stored in the refrigerant storage container 28a without being supplied to the refrigerant circuit 10.

[0082] The operation of other parts of the air conditioning unit 1a during air conditioning operation is the same as that of air conditioning unit 1, so the explanation will be omitted.

[0083] (4) Refrigerant charging method The installation work for the air conditioning system 1a includes the steps of installing the heat source unit 2 and the utilization unit 3 at their respective locations, connecting the heat source unit 2 and the utilization unit 3 via connecting pipes 6 and 7, and further including the step of sending the refrigerant stored in the refrigerant storage container 28a to the refrigerant circuit 10.

[0084] In the process where the refrigerant stored in the refrigerant storage container 28a is sent to the refrigerant circuit 10, the opening of the heat source expansion mechanism 24, the solenoid valve 28d, and the expansion mechanism 28e is controlled to be fully open or nearly fully open. In this state, when the compressor 21 is started, the high-pressure refrigerant discharged from the compressor 21 passes through the first port 28aa and pushes the refrigerant stored in the refrigerant storage container 28a out through the second port 28ab. As a result, the refrigerant that has passed through the expansion mechanism 28e is drawn in through the suction pipe 21a of the compressor 21 and fills the refrigerant circuit 10. This process ends when the compressor 21 stops.

[0085] In the air conditioning system 1a, the heat source unit 2a further includes a refrigerant quantity adjustment unit 28, so more refrigerant is filled into the heat source refrigerant flow path 20 compared to the heat source unit 2. Therefore, with the air conditioning system 1a equipped with the heat source unit 2a, even when there are multiple utilization units 3, the heat source unit 2a can sufficiently store the required amount of refrigerant in the heat source refrigerant flow path 20.

[0086] (5) Characteristics (5-1) The heat source unit 2a is connected to the utilization unit 3 and constitutes the air conditioning system 1a. The heat source unit 2a comprises a compressor 21, a heat source heat exchanger 23, a first shut-off valve 25, a second shut-off valve 26, a heat source refrigerant flow path 20, and a refrigerant. The heat source refrigerant flow path 20 of the heat source unit 2a is a flow path through which the compressor 21, the heat source heat exchanger 23, the first shut-off valve 25, the second shut-off valve 26, and the refrigerant amount adjustment unit 28 are connected by refrigerant piping 20a. The refrigerant is filled into the heat source refrigerant flow path 20. The refrigerant is carbon dioxide.

[0087] The amount of refrigerant V1 (kg) filled in the heat source refrigerant flow path 20, the volume V2 (L) of the heat source refrigerant flow path 20, and the design pressure P (MPa) of the heat source refrigerant flow path 20 satisfy the relationship (Equation 1) described above.

[0088] Therefore, the heat source unit 2a also suppresses the enlargement of the heat source refrigerant flow path 20 while preventing the occurrence of pressure abnormalities in the refrigerant flow path caused by the filled carbon dioxide refrigerant becoming supercritical.

[0089] (5-2) It is preferable that the volume V3 (L) of the accumulator 27 and the refrigerant storage container 28a satisfies the relationship (Equation 3) described above between them and the volume V2 (L) of the heat source refrigerant flow path 20.

[0090] In the heat source unit 2a, since the refrigerant can be stored not only in the heat source refrigerant flow path 20 but also in the accumulator 27 and the refrigerant storage container 28a, a sufficient volume V2 can be secured, effectively suppressing the occurrence of pressure abnormalities in the refrigerant flow path.

[0091] (6) Variant The air conditioning system 1a and the heat source refrigerant flow path 20 may also have the features of the above-described modified examples A1 to A5.

[0092] While embodiments of this disclosure have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of this disclosure as described in the claims. [Explanation of symbols]

[0093] 1, 1a: Air conditioning system 2, 2a: Heat source unit 3: Units used 6: First connecting pipe (connecting pipe) 7: Second connecting pipe (connecting pipe) 10: Refrigerant Circuit 20: Heat source refrigerant flow path (refrigerant flow path) 20a: Refrigerant piping 21: Compressor 22: Flow path switching mechanism 23:Heat source heat exchanger 25: First shut-off valve 26: Second shut-off valve 27: Accumulator (refrigerant storage container) 28: Refrigerant amount adjustment unit 28a: Refrigerant storage container L1: First length [Prior art documents] [Patent Documents]

[0094] [Patent Document 1] Japanese Patent Publication No. 2008-045769

Claims

1. A heat source unit (2, 2a) connected to the utilization unit (3) and constituting the air conditioning system (1, 1a), Compressor (21) and Heat source heat exchanger (23), First shut-off valve (25), The second shut-off valve (26) and The compressor, the heat source heat exchanger, the first shut-off valve, and the second shut-off valve are connected by refrigerant piping in a refrigerant flow path (20), Refrigerant storage containers (27, 28a) for storing refrigerant and Equipped with, The aforementioned refrigerant is It is carbon dioxide, When the volume of the refrigerant flow path is V2 (L) and the volume of the refrigerant storage container is V3 (L), 0.4 × V² ≤ V³ < 0.9 × V² Satisfying the relationship, Heat source unit.

2. The V2(L) is the volume of the refrigerant flow path (20) that is closed from the outside by the first shut-off valve and the second shut-off valve. The heat source unit according to claim 1.

3. The refrigerant storage container includes a first refrigerant storage container (27) provided on the suction side of the compressor (21) in the refrigerant flow path (20), The heat source unit according to claim 1.

4. comprising a refrigerant amount adjustment unit (28) connected to the refrigerant flow path, The refrigerant amount adjustment unit (28) has a second refrigerant storage container (28a), The heat source unit according to claim 3.

5. The second refrigerant storage container (28a) has a first port (28aa) connected to the discharge side of the compressor (21) and a second port connected to the suction side of the compressor, The heat source unit according to claim 4.

6. The refrigerant amount adjustment unit (28) comprises a solenoid valve (28d) provided in a pipe (20b) connected to the discharge side of the compressor (21), The solenoid valve (28d), when opened, supplies the refrigerant to the second refrigerant storage container (28a) via the first port (28aa). The heat source unit according to claim 5.

7. The refrigerant amount adjustment unit (28) comprises an expansion mechanism (28e) provided between the suction side of the compressor (21) and the second refrigerant storage container (28a), The expansion mechanism (28e) adjusts the flow rate of the refrigerant flowing from the second port (28ab) to the suction side of the compressor (21) and reduces the pressure of the refrigerant. The heat source unit according to claim 5.

8. The refrigerant flow path further comprises a flow path switching mechanism for switching the direction in which the refrigerant flows in the refrigerant flow path. A heat source unit according to any one of claims 1 to 7.

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