Heat source units and refrigeration equipment

Abstract

The heat source unit (10) has a low-pressure stage compressor (23), a high-pressure stage compressor (21), a heat source side heat exchanger (13), an accumulator (15), and a gas discharge passage (37). The gas discharge passage (37) connects an upper portion of the accumulator (15) to a suction port of the high-pressure stage compressor (21). A determination section (103) of the heat source unit (10) determines whether the amount of refrigerant filled in the refrigerant circuit (6) is excessive based on the pressure of the refrigerant sucked into the high-pressure stage compressor (21) and the superheat of the refrigerant.

Description

Technical Field

[0001] This disclosure relates to a heat source unit and a refrigeration device. Background Technology

[0002] Patent document 1 discloses a heat source unit. The heat source unit includes a low-pressure stage compressor, a high-pressure stage compressor, a heat source-side heat exchanger, and a liquid receiver. A venting passage is connected to the liquid receiver. The venting passage leads the gaseous refrigerant in the liquid receiver to the high-pressure stage compressor.

[0003] In Patent Document 1, the heat source unit is connected to the user-side unit via pipes to form a refrigerant circuit. In this refrigerant circuit, a two-stage compression refrigeration cycle is performed by circulating the refrigerant.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 2022-152437 Summary of the Invention

[0007] -The technical problem the invention aims to solve-

[0008] The length of the piping connecting the heat source unit and the user-side unit varies depending on the building where they are installed. Furthermore, if the piping lengths differ, the appropriate amount of refrigerant already filled in the refrigerant circuit will also differ. Therefore, during the installation of the heat source unit and the user-side unit, the operator must adjust the amount of refrigerant already filled in the refrigerant circuit.

[0009] However, the heat source unit in Patent Document 1, which includes a liquid receiver and a venting passage, does not have the function of determining whether the amount of refrigerant in the refrigerant circuit connected to the heat source unit is excessive.

[0010] The purpose of this disclosure is to determine whether the amount of refrigerant in the refrigerant circuit is excessive in a heat source unit that includes a liquid receiver and a venting passage.

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

[0012] The first aspect of this disclosure is a heat source unit 10, which is connected to a utilization side unit 50, 60 to form a refrigerant circuit 6 for a refrigeration cycle. The heat source unit 10 includes a heat source side circuit 11 and a judgment unit 103. The heat source side circuit 11 has a low-pressure stage compressor 23, a high-pressure stage compressor 21, a heat source side heat exchanger 13, and a liquid receiver 15. The judgment unit 103 determines whether the amount of refrigerant filled in the refrigerant circuit 6 is excessive. The heat source side circuit 11 has a venting passage 37, which connects the upper part of the liquid receiver 15 to the suction port of the high-pressure stage compressor 21. The judgment unit 103 determines whether the amount of refrigerant filled in the refrigerant circuit 6 is excessive based on the pressure of the refrigerant drawn into the high-pressure stage compressor 21 and the superheat of the refrigerant.

[0013] In the first aspect, the heat source unit 10 is connected to the utilization side units 50 and 60 to form a refrigerant circuit 6. In the heat source side circuit 11 of the heat source unit 10, a vent passage 37 connects the upper part of the liquid receiver 15 to the suction port of the high-pressure stage compressor 21. When there is an excess of refrigerant in the refrigerant circuit 6, the amount of liquid refrigerant in the liquid receiver 15 increases, and the liquid refrigerant and gaseous refrigerant are drawn into the high-pressure stage compressor 21 through the vent passage 37. Therefore, the state of the refrigerant drawn into the high-pressure stage compressor 21 differs depending on whether there is an excess of refrigerant in the refrigerant circuit 6 or an appropriate amount of refrigerant. Therefore, the determination unit 103 determines whether there is an excess of refrigerant in the refrigerant circuit 6 based on the pressure of the refrigerant drawn into the high-pressure stage compressor 21 and the superheat of the refrigerant.

[0014] The second aspect of this disclosure, based on the first aspect described above, involves the determination unit 103 determining, when the determination condition is met, that the amount of refrigerant filled in the refrigerant circuit 6 is excessive. The determination condition is as follows: the pressure of the refrigerant drawn into the high-pressure stage compressor 21 is higher than the reference pressure, and the superheat of the refrigerant drawn into the high-pressure stage compressor 21 is lower than the reference superheat.

[0015] When there is an excess of refrigerant in the refrigerant circuit 6, the liquid refrigerant in the receiver 15, along with the gaseous refrigerant, is drawn into the high-pressure stage compressor 21 through the vent passage 37. The more liquid refrigerant flowing in the vent passage 37, the lower the superheat of the refrigerant drawn into the high-pressure stage compressor 21. On the other hand, the higher the pressure of the refrigerant drawn into the high-pressure stage compressor 21, the higher the superheat of the refrigerant drawn into the high-pressure stage compressor 21. Therefore, if the pressure of the refrigerant drawn into the high-pressure stage compressor 21 is high, but the superheat of the refrigerant drawn into the high-pressure stage compressor 21 is low, it can be determined that there is an excess of refrigerant in the refrigerant circuit 6.

[0016] Therefore, when the judgment condition that "the pressure of the refrigerant drawn into the high-pressure stage compressor 21 is higher than the reference pressure and the superheat of the refrigerant drawn into the high-pressure stage compressor 21 is lower than the reference superheat" is met, the judgment unit 103 of the second aspect judges that the amount of refrigerant filled in the refrigerant circuit 6 is excessive.

[0017] The third aspect of this disclosure, based on the second aspect described above, involves the determination unit 103 repeatedly determining whether the determination condition is met. If the determination condition has been met multiple times within a specified time, the determination unit 103 determines that the amount of refrigerant filled in the refrigerant circuit 6 is excessive.

[0018] During the operation of the heat source unit, even if the amount of refrigerant filled in the refrigerant circuit 6 is appropriate, there is still a possibility that the judgment condition may be met by chance. Therefore, the judgment unit 103 of the third aspect repeatedly judges whether the judgment condition is met. If the judgment condition has been met multiple times within a specified time, it is judged that the amount of refrigerant filled in the refrigerant circuit 6 is excessive. Therefore, the possibility of mistakenly judging that the amount of refrigerant filled in the refrigerant circuit 6 is excessive even though the amount of refrigerant filled in the refrigerant circuit 6 is appropriate is reduced.

[0019] The fourth aspect of this disclosure, based on any one of the first to third aspects described above, involves filling the heat source side circuit 11 with carbon dioxide as a refrigerant.

[0020] In the fourth aspect, carbon dioxide is used as the refrigerant in the heat source side loop 11.

[0021] The fifth aspect of this disclosure is a refrigeration apparatus comprising a heat source unit 10 according to any one of the first to fourth aspects described above, and a utilization side unit 50, 60 connected to the heat source unit 10.

[0022] In the fifth aspect, the refrigeration unit 1 is composed of the heat source unit 10 and the utilization side units 50 and 60. Attached Figure Description

[0023] Figure 1 This is a piping system diagram showing the structure of the refrigeration device according to the first embodiment;

[0024] Figure 2 This is a block diagram showing the structure of the controller of the heat source unit according to the first embodiment;

[0025] Figure 3 This is equivalent to showing the flow of refrigerant during refrigeration operation. Figure 1 The image;

[0026] Figure 4 This shows the flow of refrigerant under the first heating operation, equivalent to Figure 1 The image;

[0027] Figure 5 This shows the flow of refrigerant under the second heating operation, equivalent to Figure 1 The image;

[0028] Figure 6 This is equivalent to showing the flow of refrigerant under the third heating operation. Figure 1 The image;

[0029] Figure 7 This is a flowchart illustrating the operation of the controller according to the first embodiment;

[0030] Figure 8 This is a piping system diagram showing the structure of the refrigeration device according to the second embodiment. Detailed Implementation

[0031] The embodiments will be described with reference to the accompanying drawings. It should be noted that the following embodiments are merely preferred examples and are not intended to limit the invention, its application, or its scope of use.

[0032] (First Implementation)

[0033] The first embodiment will be described. The refrigeration device 1 of this embodiment is capable of cooling the object being cooled and conditioning the indoor air. The object being cooled here includes the air inside equipment such as cold storage rooms, freezers, and display cases.

[0034] - Overall structure of the refrigeration unit -

[0035] like Figure 1As shown, the refrigeration unit 1 includes an outdoor heat source unit 10, an air conditioning unit 50 for conditioning the indoor air, and a cooling unit 60 for cooling the air inside the storage room. In this embodiment, the refrigeration unit 1 includes one heat source unit 10, multiple cooling units 60, and multiple air conditioning units 50. It should be noted that the number of cooling units 60 or air conditioning units 50 included in the refrigeration unit 1 can also be one.

[0036] In the refrigeration unit 1, the refrigerant circuit 6 is composed of the heat source unit 10, the cooling unit 60, the air conditioning unit 50, and the connecting pipes 2, 3, 4, and 5 that connect these units 10, 50, and 60.

[0037] In refrigerant circuit 6, the refrigerant circulates, thereby performing a refrigeration cycle. In this embodiment, the refrigerant in refrigerant circuit 6 is carbon dioxide. Refrigerant circuit 6 is configured to perform a refrigeration cycle with high pressure reaching or exceeding the critical pressure of the refrigerant.

[0038] It should be noted that the refrigerant filled in refrigerant circuit 6 is not limited to carbon dioxide. Refrigerant circuit 6 can also be filled with so-called Freon refrigerant.

[0039] In the refrigerant circuit 6, multiple air conditioning units 50 are connected to the heat source unit 10 via a first liquid connection pipe 2 and a first gas connection pipe 3. In the refrigerant circuit 6, the multiple air conditioning units 50 are connected in parallel to each other.

[0040] In the refrigerant circuit 6, multiple cooling units 60 are connected to the heat source unit 10 via a second liquid connection pipe 4 and a second gas connection pipe 5. In the refrigerant circuit 6, multiple cooling units 60 are connected in parallel to each other.

[0041] -Heat source unit-

[0042] The heat source unit 10 has an outdoor fan 12 and an outdoor circuit 11. The outdoor circuit 11 includes a compression component C, a flow path switching mechanism 30, an outdoor heat exchanger 13, a first outdoor expansion valve 14a, a liquid receiver 15, a subcooled heat exchanger 16, an intercooler 17, and a bypass pipe 85. The outdoor circuit 11 is a heat source side circuit. In addition, the heat source unit 10 has a controller 101.

[0043] <Compression Components>

[0044] Compression unit C compresses the refrigerant. Compression unit C includes a high-pressure stage compressor 21, a first low-pressure stage compressor 23, and a second low-pressure stage compressor 22. The high-pressure stage compressor 21, the first low-pressure stage compressor 23, and the second low-pressure stage compressor 22 are rotary compressors whose compression mechanisms are driven by an electric motor. These compressors 21, 22, and 23 are, for example, hermetic scroll compressors. The high-pressure stage compressor 21, the first low-pressure stage compressor 23, and the second low-pressure stage compressor 22 are configured as variable-capacity compressors capable of changing the rotational speed of the compression mechanism.

[0045] Compression unit C performs two-stage compression. The first low-pressure stage compressor 23 compresses the refrigerant already drawn from the air conditioning unit 50 or the outdoor heat exchanger 13. The second low-pressure stage compressor 22 compresses the refrigerant already drawn from the cooling unit 60. The high-pressure stage compressor 21 draws in and compresses the refrigerant already injected by the first low-pressure stage compressor 23 and the refrigerant already injected by the second low-pressure stage compressor 22.

[0046] A high-pressure stage suction pipe 21a and a high-pressure stage discharge pipe 21b are connected to the high-pressure stage compressor 21. The high-pressure stage discharge pipe 21b is a discharge pipe for the refrigerant that has been discharged from the high-pressure stage compressor 21. A first low-pressure stage suction pipe 23a and a first low-pressure stage discharge pipe 23b are connected to the first low-pressure stage compressor 23. The first low-pressure stage suction pipe 23a is a suction pipe for the refrigerant to be drawn into the first low-pressure stage compressor 23. A second low-pressure stage suction pipe 22a and a second low-pressure stage discharge pipe 22b are connected to the second low-pressure stage compressor 22. In the compression unit C, the first low-pressure stage discharge pipe 23b and the second low-pressure stage discharge pipe 22b are connected to the high-pressure stage suction pipe 21a.

[0047] The second low-pressure stage suction pipe 22a is connected to the second gas connection pipe 5. The second low-pressure stage compressor 22 is connected to the cooling unit 60 via the second gas connection pipe 5. The first low-pressure stage suction pipe 23a is connected to the air conditioning unit 50 via the flow path switching mechanism 30 and the first gas connection pipe 3.

[0048] The compression component C includes a first low-pressure stage pipe 24c and a second low-pressure stage pipe 24b. The first low-pressure stage pipe 24c is a pipe through which refrigerant flows, bypassing the first low-pressure stage compressor 23. One end of the first low-pressure stage pipe 24c is connected to a first low-pressure stage suction pipe 23a, and the other end is connected to a first low-pressure stage discharge pipe 23b. The first low-pressure stage pipe 24c is arranged parallel to the first low-pressure stage compressor 23. The second low-pressure stage pipe 24b is a pipe through which refrigerant flows, bypassing the second low-pressure stage compressor 22. One end of the second low-pressure stage pipe 24b is connected to a second low-pressure stage suction pipe 22a, and the other end is connected to a second low-pressure stage discharge pipe 22b. The second low-pressure stage pipe 24b is arranged parallel to the second low-pressure stage compressor 22.

[0049] <Flow path switching mechanism>

[0050] The flow path switching mechanism 30 is a mechanism for switching the flow path of the refrigerant in the refrigerant circuit 6. The flow path switching mechanism 30 has a first pipe 31, a second pipe 32, a third pipe 33, a fourth pipe 34, a first reversing valve 81, and a second reversing valve 82.

[0051] The inflow ends of the first pipe 31 and the second pipe 32 are connected to the high-pressure stage discharge pipe 21b. The outflow ends of the third pipe 33 and the fourth pipe 34 are connected to the first low-pressure stage suction pipe 23a.

[0052] The first reversing valve 81 and the second reversing valve 82 respectively switch the flow path of the refrigerant to be drawn into the first low-pressure stage compressor 23 and the flow path of the refrigerant already sprayed from the high-pressure stage compressor 21. The first reversing valve 81 and the second reversing valve 82 are both four-way reversing valves with four valve ports.

[0053] The first port of the first reversing valve 81 is connected to the outflow end of the first pipe 31. The second port of the first reversing valve 81 is connected to the inflow end of the third pipe 33. The third port of the first reversing valve 81 is closed. The fourth port of the first reversing valve 81 is connected to one end of the first outdoor gas pipe 35. The other end of the first outdoor gas pipe 35 is connected to the first gas connection pipe 3.

[0054] The first port of the second directional valve 82 is connected to the outflow end of the second pipe 32. The second port of the second directional valve 82 is connected to the inflow end of the fourth pipe 34. The third port of the second directional valve 82 is connected to the second outdoor gas pipe 36. The fourth port of the second directional valve 82 is closed.

[0055] The first reversing valve 81 and the second reversing valve 82 are respectively in the first state ( Figure 1 The state shown by the solid line) and the second state ( Figure 1The directional valves 81 and 82 switch between states indicated by the dashed lines. In the first state, the first valve port is connected to the third valve port, and the second valve port is connected to the fourth valve port. In the second state, the first valve port is connected to the fourth valve port, and the second valve port is connected to the third valve port.

[0056] It should be noted that in the flow path switching mechanism 30, the first reversing valve 81 and the second reversing valve 82 can also be three-way valves with three valve ports.

[0057] <First Outdoor Heat Exchanger>

[0058] The outdoor heat exchanger 13 constitutes a heat source-side heat exchanger. The outdoor heat exchanger 13 is a finned-tube air heat exchanger. An outdoor fan 12 is arranged near the outdoor heat exchanger 13. The outdoor fan 12 delivers outdoor air. The outdoor heat exchanger 13 allows the refrigerant flowing within it to exchange heat with the outdoor air delivered by the outdoor fan 12.

[0059] A second outdoor gas pipe 36 is connected to the gas end of the outdoor heat exchanger 13. An outdoor flow path O is connected to the liquid end of the outdoor heat exchanger 13.

[0060] <Outdoor Flow Path>

[0061] The outdoor flow path O includes: outdoor first pipe O1, outdoor second pipe O2, outdoor third pipe O3, outdoor fourth pipe O4, outdoor fifth pipe O5, outdoor sixth pipe O6, outdoor seventh pipe O7, and outdoor eighth pipe O8.

[0062] One end of the outdoor first pipe O1 is connected to the liquid end of the outdoor heat exchanger 13. One end of the outdoor second pipe O2 and one end of the outdoor third pipe O3 are respectively connected to the other end of the outdoor first pipe O1. The other end of the outdoor second pipe O2 is connected to the top of the liquid reservoir 15.

[0063] One end of the outdoor fourth pipe O4 is connected to the bottom of the reservoir 15. One end of the outdoor fifth pipe O5 and the other end of the outdoor third pipe O3 are respectively connected to the other end of the outdoor fourth pipe O4. One end of the outdoor sixth pipe O6 and one end of the outdoor eighth pipe O8 are respectively connected to the other end of the outdoor fifth pipe O5.

[0064] The other end of the outdoor eighth pipe O8 is connected to the first liquid-side main pipe 4a of the second liquid connection pipe 4. The outdoor eighth pipe O8 is a liquid pipe for supplying liquid refrigerant downstream of the liquid receiver 15. The other end of the outdoor sixth pipe O6 is connected to the first liquid connection pipe 2. One end of the outdoor seventh pipe O7 is connected midway through the outdoor sixth pipe O6. The other end of the outdoor seventh pipe O7 is connected midway through the outdoor second pipe O2.

[0065] <Outdoor Expansion Valve>

[0066] A first outdoor expansion valve 14a is installed on the first outdoor pipe o1 of the outdoor circuit 11. Additionally, a second outdoor expansion valve 14b is installed on the third outdoor pipe o3 of the outdoor circuit 11. Both the first outdoor expansion valve 14a and the second outdoor expansion valve 14b are electronic expansion valves capable of adjusting their opening degree. The first outdoor expansion valve 14a and the second outdoor expansion valve 14b are expansion valves installed on the outdoor circuit 11, which serves as the heat source side circuit.

[0067] <Liquid Storage>

[0068] The receiver 15 constitutes a container for storing refrigerant. The receiver 15 is located downstream of the first outdoor expansion valve 14a. In the receiver 15, the refrigerant is separated into gaseous refrigerant and liquid refrigerant. The other end of the outdoor second pipe O2 and one end of the vent pipe 37 (described later) are connected to the top of the receiver 15.

[0069] The receiver 15 is covered with insulation material 15a. Glass wool can be cited as an example of insulation material 15a. By covering the receiver 15 with insulation material 15a, the amount of heat transferred from the outdoor air to the refrigerant in the receiver 15 is reduced under conditions of high outdoor air temperature, such as in summer.

[0070] Intermediate Injection Circuit

[0071] The outdoor circuit 11 includes an intermediate injection circuit 49. The intermediate injection circuit 49 is a circuit that supplies refrigerant, after being depressurized by the first outdoor expansion valve 14a, to the high-pressure stage suction pipe 21a. The intermediate injection circuit 49 includes a vent pipe 37 and an injection pipe 38.

[0072] One end of the injection pipe 38 is connected to the middle of the fifth outdoor pipe o5. The other end of the injection pipe 38 is connected to the high-pressure stage suction pipe 21a. A pressure reducing valve 40 is installed on the injection pipe 38. The pressure reducing valve 40 is an expansion valve with a variable opening degree.

[0073] The vent pipe 37 is a conduit used to deliver gaseous refrigerant from the receiver 15 to the high-pressure stage suction pipe 21a. One end of the vent pipe 37 is connected to the top of the receiver 15. The other end of the vent pipe 37 is connected midway to the injection pipe 38.

[0074] The vent pipe 37 leads the refrigerant (mainly gaseous refrigerant) in the receiver 15 to the high-pressure stage suction pipe 21a via the injection pipe 38. The vent pipe 37 forms a venting passage that connects the upper part of the receiver 15 to the suction port of the high-pressure stage compressor 21.

[0075] A vent valve 39 is connected to the vent pipe 37. The vent valve 39 is an electronic expansion valve with a variable opening degree.

[0076] <Subcooled heat exchanger>

[0077] The outdoor circuit 11 includes a subcooled heat exchanger 16. The subcooled heat exchanger 16 is a heat exchanger that cools the refrigerant (mainly liquid refrigerant) separated from the receiver 15. The subcooled heat exchanger 16 is located downstream of the receiver 15. The subcooled heat exchanger 16 has a first flow path 16a and a second flow path 16b. The subcooled heat exchanger 16 allows heat exchange between the refrigerant flowing in the first flow path 16a and the refrigerant flowing in the second flow path 16b.

[0078] In the subcooled heat exchanger 16, the refrigerant flowing in the first flow path 16a is cooled. The first flow path 16a is connected midway to the outdoor fourth pipe o4, which is a liquid pipe for supplying liquid refrigerant in the outdoor circuit 11.

[0079] The second flow path 16b is included in the intermediate injection circuit 49. Specifically, the second flow path 16b is connected downstream of the pressure reducing valve 40 in the injection pipe 38. The second flow path 16b supplies the refrigerant flow after its pressure is reduced by the pressure reducing valve 40.

[0080] Intercooler

[0081] Intercooler 17 is connected to intermediate flow path 41. One end of intermediate flow path 41 is connected to both the first low-pressure stage ejector pipe 23b and the second low-pressure stage ejector pipe 22b. The other end of intermediate flow path 41 is connected to high-pressure stage suction pipe 21a.

[0082] Intercooler 17 is a finned tube air heat exchanger. A blower fan 17a is arranged near intercooler 17. Intercooler 17 allows the refrigerant flowing inside it to exchange heat with outdoor air supplied by blower fan 17a.

[0083] <Check valve>

[0084] The outdoor circuit 11 includes: a first check valve CV1, a second check valve CV2, a third check valve CV3, a fourth check valve CV4, a fifth check valve CV5, a sixth check valve CV6, a seventh check valve CV7, an eighth check valve CV8, and a ninth check valve CV9. These check valves CV1 to CV9 allow refrigerant to flow towards... Figure 1 The refrigerant should flow in the direction indicated by the arrow; refrigerant should not flow in the opposite direction of the arrow.

[0085] The first check valve CV1 is connected to the high-pressure stage outlet pipe 21b. The second check valve CV2 is connected to the second low-pressure stage outlet pipe 22b. The third check valve CV3 is connected to the first low-pressure stage outlet pipe 23b. The fourth check valve CV4 is connected to the outdoor second pipe O2. The fifth check valve CV5 is connected to the outdoor third pipe O3. The sixth check valve CV6 is connected to the outdoor sixth pipe O6. The seventh check valve CV7 is connected to the outdoor seventh pipe O7. The eighth check valve CV8 is connected to the second low-pressure stage pipe 24b. The ninth check valve CV9 is connected to the first low-pressure stage pipe 24c.

[0086] <sensor>

[0087] The heat source unit 10 has various sensors. These sensors include: a high-pressure sensor 71, an intermediate-pressure sensor 72, a first low-pressure sensor 73, a second low-pressure sensor 74, a liquid refrigerant pressure sensor 75, and a high-pressure stage suction temperature sensor 77.

[0088] The high-pressure sensor 71 is connected to the high-pressure stage discharge pipe 21b. The high-pressure sensor 71 detects the pressure of the refrigerant (high-pressure refrigerant pressure HP) that has been discharged by the high-pressure stage compressor 21.

[0089] Intermediate pressure sensor 72 is connected downstream of intercooler 17 in intermediate flow path 41. Intermediate pressure sensor 72 detects the pressure of the refrigerant in intermediate flow path 41. In other words, intermediate pressure sensor 72 detects the pressure of the refrigerant to be drawn into high-pressure stage compressor 21.

[0090] The first low-pressure sensor 73 is connected to the second low-pressure stage suction pipe 22a. The first low-pressure sensor 73 detects the pressure of the suction refrigerant (the pressure LP1 of the first low-pressure refrigerant) to be drawn into the second low-pressure stage compressor 22.

[0091] The second low-pressure sensor 74 is connected to the first low-pressure stage suction pipe 23a. The second low-pressure sensor 74 detects the pressure of the suction refrigerant (the pressure LP2 of the second low-pressure refrigerant) to be drawn into the first low-pressure stage compressor 23.

[0092] A liquid refrigerant pressure sensor 75 is connected to the outdoor fourth pipe O4. The liquid refrigerant pressure sensor 75 detects the pressure of the refrigerant flowing in the outdoor fourth pipe O4. In other words, the liquid refrigerant pressure sensor 75 detects the pressure of the liquid refrigerant in the receiver 15.

[0093] A high-pressure stage suction temperature sensor 77 is installed on the high-pressure stage suction pipe 21a. The high-pressure stage suction temperature sensor 77 detects the temperature of the refrigerant flowing in the high-pressure stage suction pipe 21a. In other words, the high-pressure stage suction temperature sensor 77 detects the temperature of the refrigerant to be drawn into the high-pressure stage compressor 21.

[0094] <Controller>

[0095] like Figure 2 As shown, the controller 101 includes a microcomputer 102 and a storage device 105. The microcomputer 102 is mounted on a control board, and the storage device 105 stores software for operating the microcomputer 102. The storage device 105 is a semiconductor memory. The controller 101 controls the components of the heat source unit 10.

[0096] The microcomputer 102 of the controller 101 functions as the refrigerant dosage determination unit 103 by executing a program stored in the storage device 105. The refrigerant dosage determination unit 103 determines whether the amount of refrigerant already filled into the refrigerant circuit 6 is more than the appropriate amount. In other words, the refrigerant dosage determination unit 103 determines whether the amount of refrigerant already filled into the refrigerant circuit 6 is excessive.

[0097] Here, when the refrigeration unit 1 is installed in a building or the like, the heat source unit 10, the cooling unit 60, and the air conditioning unit 50 are respectively placed in designated locations, and then connecting pipes 2, 3, 4, and 5 are laid between the cooling unit 60 and the air conditioning unit 50 and the heat source unit 10. As a result, a refrigerant circuit 6 is formed.

[0098] The number of cooling units 60 and air conditioning units 50, as well as the lengths of connecting pipes 2, 3, 4, and 5, typically vary depending on the building where the refrigeration unit 1 is installed. On the other hand, the appropriate amount of refrigerant already filled into the refrigerant circuit 6 varies depending on the number of cooling units 60 and air conditioning units 50 installed in the refrigerant circuit 6, and the lengths of connecting pipes 2, 3, 4, and 5 installed in the refrigerant circuit 6. Therefore, during the installation of the refrigeration unit 1, operators need to replenish refrigerant to the refrigerant circuit 6 as needed.

[0099] After the operator has added refrigerant to the refrigerant circuit 6, it is necessary to confirm whether the amount of refrigerant added to the refrigerant circuit 6 is appropriate. Therefore, during the trial operation of the refrigeration unit 1 after the operator has added refrigerant to the refrigerant circuit 6, the refrigerant quantity determination unit 103 of the controller 101 determines whether the amount of refrigerant added to the refrigerant circuit 6 is excessive.

[0100] -Air conditioning unit-

[0101] Air conditioning unit 50 is the first-use unit installed in the room. Air conditioning unit 50 regulates the air in the indoor space. Air conditioning unit 50 has an indoor fan 52 and an indoor circuit 51. A first liquid connection pipe 2 is connected to the liquid end of the indoor circuit 51. A first gas connection pipe 3 is connected to the gas end of the indoor circuit 51.

[0102] In the indoor circuit 51, an indoor expansion valve 53 and an indoor heat exchanger 54 are arranged sequentially from the liquid end to the gas end. The indoor expansion valve 53 is an electronic expansion valve with variable opening. The indoor heat exchanger 54 is a finned tube air heat exchanger. An indoor fan 52 is arranged near the indoor heat exchanger 54. The indoor fan 52 delivers indoor air. The indoor heat exchanger 54 facilitates heat exchange between the refrigerant flowing within it and the indoor air delivered by the indoor fan 52.

[0103] - Cooling Unit -

[0104] Cooling unit 60 is a second-use unit installed within the room. Cooling unit 60 is, for example, a refrigerated display case installed in a convenience store or similar store. It should be noted that cooling unit 60 can also be a unit cooler used to cool the air inside a cold storage room.

[0105] The cooling unit 60 has a cooling fan 62 and a cooling circuit 61. A liquid-side branch pipe 4c of a second liquid connection pipe 4 is connected to the liquid end of the cooling circuit 61. A gas-side branch pipe 5c of a second gas connection pipe 5 is connected to the gas end of the cooling circuit 61.

[0106] In the cooling circuit 61, a cooling expansion valve 63 and a cooling heat exchanger 64 are arranged sequentially from the liquid end to the gas end. The cooling expansion valve 63 is an electronically controlled expansion valve with a variable opening. The cooling heat exchanger 64 is a finned tube air heat exchanger. A cooling fan 62 is arranged near the cooling heat exchanger 64. The cooling fan 62 delivers air from the storage chamber. The cooling heat exchanger 64 allows the refrigerant flowing inside it to exchange heat with the air delivered by the cooling fan 62.

[0107] - Operation of the refrigeration unit -

[0108] The operation of the refrigeration unit 1 will be described. The refrigeration unit 1 performs refrigeration operation, first heating operation, second heating operation, and third heating operation. In addition, the refrigeration unit 1 performs defrosting operation, which melts the frost adhering to the outdoor heat exchanger 13.

[0109] <Refrigeration Operation>

[0110] Reference Figure 3 The refrigeration operation of refrigeration unit 1 will be explained. The refrigeration operation is the operation of air conditioning unit 50 to cool the indoor space.

[0111] During refrigeration operation, the first reversing valve 81 and the second reversing valve 82 are set to the first state, and the second outdoor expansion valve 14b is kept closed. Additionally, during refrigeration operation, the first low-pressure stage compressor 23, the second low-pressure stage compressor 22, and the high-pressure stage compressor 21 operate. During refrigeration operation, the refrigerant circulates in the refrigerant circuit 6, thereby performing the refrigeration cycle. The outdoor heat exchanger 13 functions as a heat exchanger (gas cooler), while the cooling heat exchanger 64 and the indoor heat exchanger 54 function as evaporators.

[0112] The refrigerant ejected from the high-pressure stage compressor 21 flows into the outdoor heat exchanger 13 through the second reversing valve 82, releasing heat towards the outdoor air. The refrigerant that has passed through the outdoor heat exchanger 13 is depressurized upon passing through the first outdoor expansion valve 14a, then passes through the receiver 15, and is subsequently cooled during its passage through the first flow path 16a of the subcooled heat exchanger 16. A portion of the refrigerant that has passed through the first flow path 16a of the subcooled heat exchanger 16 flows through the injection pipe 38 into the second flow path 16b of the subcooled heat exchanger 16, evaporates after absorbing heat, and then flows into the high-pressure stage suction pipe 21a. The remaining portion of the refrigerant that has passed through the first flow path 16a of the subcooled heat exchanger 16 flows separately into the first liquid connection pipe 2 and the second liquid connection pipe 4.

[0113] The refrigerant flowing in the first liquid connection pipe 2 is distributed to multiple air conditioning units 50. In each air conditioning unit 50, the refrigerant that has flowed into the indoor circuit 51 is depressurized as it passes through the indoor expansion valve 53, and then evaporates by absorbing heat from the indoor air in the indoor heat exchanger 54. Each air conditioning unit 50 blows the air that has been cooled in the indoor heat exchanger 54 into the indoor space.

[0114] The refrigerant that has flowed out of the indoor heat exchanger 54 of each air conditioning unit 50 flows into the first gas connection pipe 3 and merges with it, then flows into the first outdoor gas pipe 35 of the outdoor circuit 11, and then flows into the first low-pressure stage suction pipe 23a through the first reversing valve 81, and is then sucked in and compressed by the first low-pressure stage compressor 23.

[0115] The refrigerant flowing in the second liquid connection pipe 4 is distributed to multiple cooling units 60. In each cooling unit 60, the refrigerant that has flowed into the cooling circuit 61 is depressurized as it passes through the cooling expansion valve 63, and then evaporates by absorbing heat from the air inside the storage unit in the cooling heat exchanger 64. Each cooling unit 60 blows the air that has been cooled in the cooling heat exchanger 64 toward the storage space.

[0116] The refrigerant that has flowed out of the cooling heat exchanger 64 of each cooling unit 60 flows into the second gas connection pipe 5 and merges with it, then flows into the second low-pressure stage suction pipe 22a of the outdoor circuit 11, and is then sucked in and compressed by the second low-pressure stage compressor 22.

[0117] The refrigerant, compressed in the first low-pressure stage compressor 23 and the second low-pressure stage compressor 22 respectively, releases heat to the outside air in the intercooler 17, and then merges with the refrigerant flowing in the injection pipe 38 before being drawn into the high-pressure stage compressor 21. The high-pressure stage compressor 21 compresses the drawn-in refrigerant and then sprays it out.

[0118] <First Heating Operation>

[0119] Reference Figure 4 The first heating operation of the refrigeration unit 1 will be explained. The first heating operation is the operation in which the air conditioning unit 50 heats the room. The first heating operation is carried out under the condition that the heat released by the refrigerant in the air conditioning unit 50 is less than the heat absorbed by the refrigerant in the cooling unit 60.

[0120] During the first heating operation, the first reversing valve 81 is set to the second state, the second reversing valve 82 is set to the first state, and the second outdoor expansion valve 14b is kept closed. Additionally, during the first heating operation, the first low-pressure stage compressor 23 is off, while the second low-pressure stage compressor 22 and the high-pressure stage compressor 21 operate. During the first heating operation, the refrigerant circulates in the refrigerant circuit 6, thereby performing a refrigeration cycle. The indoor heat exchanger 54 and the outdoor heat exchanger 13 function as heat exchangers (gas coolers), and the cooling heat exchanger 64 functions as an evaporator.

[0121] A portion of the refrigerant that has been injected from the high-pressure stage compressor 21 flows into the first outdoor gas pipe 35 through the first reversing valve 81, and the remaining portion flows into the second outdoor gas pipe 36 through the second reversing valve 82.

[0122] Refrigerant flowing in the first outdoor gas pipe 35 is distributed to multiple air conditioning units 50 via the first gas connection pipe 3. In each air conditioning unit 50, the refrigerant that has flowed into the indoor circuit 51 releases heat towards the indoor air in the indoor heat exchanger 54, and then, after being depressurized by the indoor expansion valve 53, flows into the first liquid connection pipe 2. The refrigerant that has flowed from each air conditioning unit 50 into the first liquid connection pipe 2 flows into the liquid receiver 15 of the outdoor circuit 11. Each air conditioning unit 50 blows air that has been heated in the indoor heat exchanger 54 into the indoor space.

[0123] The refrigerant flowing in the second outdoor gas pipe 36 flows into the outdoor heat exchanger 13 and releases heat to the outdoor air. The refrigerant that has passed through the outdoor heat exchanger 13 is depressurized when it passes through the first outdoor expansion valve 14a and then flows into the liquid receiver 15.

[0124] The refrigerant flowing out of the receiver 15 is cooled during its passage through the first flow path 16a of the subcooled heat exchanger 16. A portion of the refrigerant that has passed through the first flow path 16a of the subcooled heat exchanger 16 flows through the injection pipe 38 into the second flow path 16b of the subcooled heat exchanger 16, and after absorbing heat and evaporating, flows into the high-pressure stage suction pipe 21a. The remaining portion of the refrigerant that has passed through the first flow path 16a of the subcooled heat exchanger 16 flows into the second liquid connection pipe 4.

[0125] The refrigerant flowing in the second liquid connection pipe 4 is distributed to multiple cooling units 60. In each cooling unit 60, the refrigerant that has flowed into the cooling circuit 61 is depressurized as it passes through the cooling expansion valve 63, and then evaporates by absorbing heat from the air inside the storage unit in the cooling heat exchanger 64. Each cooling unit 60 blows the air that has been cooled in the cooling heat exchanger 64 toward the storage space.

[0126] The refrigerant that has flowed out of the cooling heat exchanger 64 of each cooling unit 60 flows into the second gas connection pipe 5 and merges with it, then flows into the second low-pressure stage suction pipe 22a of the outdoor circuit 11, and is then sucked in and compressed by the second low-pressure stage compressor 22.

[0127] The refrigerant, already compressed in the second low-pressure stage compressor 22, releases heat to the outside air in the intercooler 17. After merging with the refrigerant flowing in the injection pipe 38, it is drawn into the high-pressure stage compressor 21. The high-pressure stage compressor 21 compresses the drawn-in refrigerant and then ejects it.

[0128] <Second Heating Operation>

[0129] Reference Figure 5 The second heating operation of the refrigeration unit 1 will be explained. The second heating operation is the operation in which the air conditioning unit 50 heats the room. The second heating operation is carried out under the condition that the heat released by the refrigerant in the air conditioning unit 50 and the heat absorbed by the refrigerant in the cooling unit 60 are in balance.

[0130] In the second heating operation, the first reversing valve 81 and the second reversing valve 82 are set to the second state, and the second outdoor expansion valve 14b is kept closed. Additionally, in the second heating operation, the first low-pressure stage compressor 23 is off, while the second low-pressure stage compressor 22 and the high-pressure stage compressor 21 are operating. In the second heating operation, a refrigeration cycle is performed by circulating refrigerant in the refrigerant circuit 6. The indoor heat exchanger 54 functions as a heat exchanger (gas cooler), the cooling heat exchanger 64 functions as an evaporator, and the outdoor heat exchanger 13 is off.

[0131] Refrigerant injected from the high-pressure stage compressor 21 flows into the first outdoor gas pipe 35 through the first reversing valve 81, and is then distributed to multiple air conditioning units 50 through the first gas connection pipe 3. In each air conditioning unit 50, the refrigerant that has flowed into the indoor circuit 51 releases heat towards the indoor air in the indoor heat exchanger 54, and then, after being depressurized by the indoor expansion valve 53, flows into the first liquid connection pipe 2. The refrigerant that has flowed from each air conditioning unit 50 into the first liquid connection pipe 2 flows into the liquid receiver 15 of the outdoor circuit 11. Each air conditioning unit 50 blows the air that has been heated in the indoor heat exchanger 54 into the indoor space.

[0132] The refrigerant flowing out of the receiver 15 is cooled during its passage through the first flow path 16a of the subcooled heat exchanger 16. A portion of the refrigerant that has passed through the first flow path 16a of the subcooled heat exchanger 16 flows through the injection pipe 38 into the second flow path 16b of the subcooled heat exchanger 16, and after absorbing heat and evaporating, flows into the high-pressure stage suction pipe 21a. The remaining portion of the refrigerant that has passed through the first flow path 16a of the subcooled heat exchanger 16 flows into the second liquid connection pipe 4.

[0133] The refrigerant flowing in the second liquid connection pipe 4 is distributed to multiple cooling units 60. In each cooling unit 60, the refrigerant that has flowed into the cooling circuit 61 is depressurized as it passes through the cooling expansion valve 63, and then evaporates by absorbing heat from the air inside the storage unit in the cooling heat exchanger 64. Each cooling unit 60 blows the air that has been cooled in the cooling heat exchanger 64 toward the storage space.

[0134] The refrigerant that has flowed out of the cooling heat exchanger 64 of each cooling unit 60 flows into the second gas connection pipe 5 and merges with it, then flows into the second low-pressure stage suction pipe 22a of the outdoor circuit 11, and is then sucked in and compressed by the second low-pressure stage compressor 22.

[0135] The refrigerant, already compressed in the second low-pressure stage compressor 22, releases heat to the outside air in the intercooler 17. After merging with the refrigerant flowing in the injection pipe 38, it is drawn into the high-pressure stage compressor 21. The high-pressure stage compressor 21 compresses the drawn-in refrigerant and then ejects it.

[0136] <Third Heating Operation>

[0137] Reference Figure 6 The third heating operation of the refrigeration unit 1 will be explained. The third heating operation is the operation in which the air conditioning unit 50 heats the room. The third heating operation is carried out when the heat released by the refrigerant in the air conditioning unit 50 is greater than the heat absorbed by the refrigerant in the cooling unit 60.

[0138] In the third heating operation, the first reversing valve 81 and the second reversing valve 82 are set to the second state, and the first outdoor expansion valve 14a is kept fully open. Additionally, in the third heating operation, the first low-pressure stage compressor 23, the second low-pressure stage compressor 22, and the high-pressure stage compressor 21 operate. In the third heating operation, the refrigerant circulates in the refrigerant circuit 6, thereby performing a refrigeration cycle. The indoor heat exchanger 54 functions as a heat exchanger (gas cooler), and the cooling heat exchanger 64 and the outdoor heat exchanger 13 function as evaporators.

[0139] Refrigerant injected from the high-pressure stage compressor 21 flows into the first outdoor gas pipe 35 through the first reversing valve 81, and is then distributed to multiple air conditioning units 50 through the first gas connection pipe 3. In each air conditioning unit 50, the refrigerant that has flowed into the indoor circuit 51 releases heat towards the indoor air in the indoor heat exchanger 54, and then, after being depressurized by the indoor expansion valve 53, flows into the first liquid connection pipe 2. The refrigerant that has flowed from each air conditioning unit 50 into the first liquid connection pipe 2 flows into the liquid receiver 15 of the outdoor circuit 11. Each air conditioning unit 50 blows the air that has been heated in the indoor heat exchanger 54 into the indoor space.

[0140] The refrigerant that has flowed out of the receiver 15 is cooled during its passage through the first flow path 16a of the subcooled heat exchanger 16. The refrigerant branch that has passed through the first flow path 16a of the subcooled heat exchanger 16 flows into the outdoor fifth pipe O5 and the outdoor third pipe O3.

[0141] A portion of the refrigerant flowing in the fifth outdoor pipe O5 flows into the injection pipe 38, and the remainder flows into the eighth outdoor pipe O8. The refrigerant flowing in the injection pipe 38 flows into the second flow path 16b of the supercooled heat exchanger 16, and after absorbing heat and evaporating, flows into the high-pressure stage suction pipe 21a.

[0142] The refrigerant flowing in the outdoor eighth pipe 08 is distributed to multiple cooling units 60 via the second liquid connection pipe 4. In each cooling unit 60, the refrigerant that has flowed into the cooling circuit 61 is depressurized as it passes through the cooling expansion valve 63, and then evaporates by absorbing heat from the air inside the storage unit in the cooling heat exchanger 64. Each cooling unit 60 blows the air that has been cooled in the cooling heat exchanger 64 toward the storage space.

[0143] The refrigerant that has flowed out of the cooling heat exchanger 64 of each cooling unit 60 flows into the second gas connection pipe 5 and merges with it, then flows into the second low-pressure stage suction pipe 22a of the outdoor circuit 11, and is then sucked in and compressed by the second low-pressure stage compressor 22.

[0144] The refrigerant flowing in the outdoor third pipe o3 is depressurized when passing through the second outdoor expansion valve 14 and then flows into the outdoor heat exchanger 13, where it absorbs heat from the outdoor air and evaporates. The refrigerant that has passed through the outdoor heat exchanger 13 flows into the first low-pressure stage suction pipe 23a through the second reversing valve 82, and is then drawn in and compressed by the first low-pressure stage compressor 23.

[0145] The refrigerant, compressed in the first low-pressure stage compressor 23 and the second low-pressure stage compressor 22 respectively, releases heat to the outside air in the intercooler 17, and then merges with the refrigerant flowing in the injection pipe 38 before being drawn into the high-pressure stage compressor 21. The high-pressure stage compressor 21 compresses the drawn-in refrigerant and then sprays it out.

[0146] <Defrosting Operation>

[0147] The defrosting operation of the refrigeration unit 1 will be explained. The defrosting operation is for melting the frost adhering to the outdoor heat exchanger 13. During the third heating operation, when the frost adhering to the outdoor heat exchanger 13 reaches a certain level, the refrigeration unit 1 temporarily stops the third heating operation and performs the defrosting operation.

[0148] During defrosting operation, the refrigerant flows in the refrigerant circuit 6 in the same manner as in the first heating operation. Specifically, the second reversing valve 82 is set to the first state, and the outdoor heat exchanger 13 functions as a heat exchanger (gas cooler). The frost adhering to the outdoor heat exchanger 13 is melted by the refrigerant heating.

[0149] - Controller Actions -

[0150] As described above, during the trial operation of the refrigeration device 1 after refrigerant has been added to the refrigerant circuit 6, the refrigerant dosage determination unit 103 of the controller 101 determines whether the amount of refrigerant already added to the refrigerant circuit 6 is excessive. When the number of times the determination condition has been met from the start of operation until the reference time Hc has elapsed reaches the reference number Nc, the refrigerant dosage determination unit 103 of this embodiment determines that the amount of refrigerant already added to the refrigerant circuit 6 is excessive.

[0151] Reference Figure 7 The flowchart describes the actions performed by the cooling dose determination unit 103 of the controller 101.

[0152] <Step ST1>

[0153] First, the cooling dose determination unit 103 performs step ST1. In step ST1, the cooling dose determination unit 103 resets the number of times the condition has been met (N) to "zero". This number of times N represents the number of times the determination condition has been met.

[0154] <Step ST2>

[0155] Next, the cooling dose determination unit 103 performs step ST2. In step ST2, the cooling dose determination unit 103 starts timing the elapsed time H.

[0156] <Step ST3>

[0157] Next, the cooling dose determination unit 103 performs step ST3. In step ST3, the cooling dose determination unit 103 compares the current elapsed time H with a reference time Hc. If the elapsed time H has not reached the reference time Hc (H < Hc), the cooling dose determination unit 103 performs step ST4. On the other hand, if the elapsed time H has reached the reference time Hc (H ≥ Hc), the cooling dose determination unit 103 terminates the operation. The reference time Hc is preferably 2 hours or more.

[0158] <Step ST4>

[0159] In step ST4, the refrigerant dosage determination unit 103 acquires the measured value of the intermediate pressure sensor 72 as the suction pressure Pm of the high-pressure stage compressor 21, and the refrigerant dosage determination unit 103 also acquires the measured value of the high-pressure stage suction temperature sensor 77 as the suction temperature Tm of the high-pressure stage compressor 21.

[0160] <Step ST5>

[0161] Next, the refrigerant dosage determination unit 103 performs step ST5. In step ST5, the refrigerant dosage determination unit 103 calculates the superheat of the refrigerant drawn into the high-pressure stage compressor 21 (absorption superheat SHm). The refrigerant dosage determination unit 103 calculates the absorptive superheat SHm by subtracting the saturation temperature of the refrigerant at the absorptive pressure Pm from the absorptive temperature Tm.

[0162] <Step ST6>

[0163] Next, the refrigerant dosage determination unit 103 performs step ST6. In step ST6, the refrigerant dosage determination unit 103 determines whether a determination condition is met. The determination condition is that "the suction pressure Pm of the high-pressure stage compressor 21 is higher than the reference pressure Pc (Pm > Pc), and the suction superheat SHm of the high-pressure stage compressor 21 is lower than the reference superheat SHc (SHm < SHc)". The reference pressure Pc is, for example, 5 MPa. The reference superheat SHc is, for example, 5°C.

[0164] If the determination condition is met, the cooling dose determination unit 103 proceeds to step ST7. On the other hand, if the determination condition is not met, the cooling dose determination unit 103 proceeds to step ST3.

[0165] Here, when there is an excess of refrigerant in the refrigerant circuit 6, the liquid refrigerant in the receiver 15, along with the gaseous refrigerant, is drawn into the high-pressure stage compressor 21 through the vent pipe 37. The more liquid refrigerant flowing in the vent pipe 37, the lower the superheat of the refrigerant drawn into the high-pressure stage compressor 21.

[0166] On the other hand, the higher the pressure of the refrigerant drawn into the high-pressure stage compressor 21, the higher the superheat of the refrigerant drawn into the high-pressure stage compressor 21. Therefore, if the pressure of the refrigerant drawn into the high-pressure stage compressor 21 is high, but the superheat of the refrigerant drawn into the high-pressure stage compressor 21 is low, it can be determined that there is an excess of refrigerant in the refrigerant circuit 6.

[0167] Therefore, the refrigerant dosage determination unit 103 of this embodiment determines whether the determination condition "the suction pressure Pm of the high-pressure stage compressor 21 is higher than the reference pressure Pc (Pm>Pc) and the suction superheat SHm of the high-pressure stage compressor 21 is lower than the reference superheat SHc (SHm<SHc)" is met.

[0168] <Step ST7>

[0169] In step ST7, the cooling dose determination unit 103 updates the success rate N. Specifically, the value obtained by adding "1" to the previous success rate N is set as the new success rate N.

[0170] <Step ST8>

[0171] Next, the cooling dosage determination unit 103 performs step ST8. In step ST8, the cooling dosage determination unit 103 compares the number of occurrences N with the reference number Nc. If the condition "the number of occurrences N is greater than or equal to the reference number Nc (N≥Nc)" is met, the cooling dosage determination unit 103 performs step ST9. Otherwise, if this condition is not met, the cooling dosage determination unit 103 performs step ST3. The reference number Nc is an integer greater than or equal to 2. The reference number Nc is preferably 5 or more.

[0172] <Step ST9>

[0173] The condition in step ST8 is met when the elapsed time H reaches the reference time Hc, and the number of times the judgment condition in step ST6 is met (N) reaches the reference number Nc. Therefore, in step ST9, the refrigerant dosage judgment unit 103 determines that there is an excess of refrigerant in the refrigerant circuit 6 and informs the operator of this. For example, the refrigerant dosage judgment unit 103 informs the operator of the excess refrigerant in the refrigerant circuit 6 by displaying a predetermined display on the display unit of the remote control of the refrigeration unit 1.

[0174] -Features of the first embodiment (1)-

[0175] In the heat source unit 10 of this embodiment, the refrigerant dosage determination unit 103 of the controller 101 automatically determines that the amount of refrigerant already filled into the refrigerant circuit 6 of the refrigeration unit 1 is excessive. Therefore, the labor time required for installing the refrigeration unit 1 can be reduced. In addition, since it is possible to accurately determine whether the amount of refrigerant already filled into the refrigerant circuit 6 of the refrigeration unit 1 is excessive, the capacity of the refrigeration unit 1 can be reliably utilized.

[0176] -Features of the first embodiment (2)-

[0177] During the operation of the refrigeration unit 1, under the condition that the pressure of the refrigerant drawn into the high-pressure stage compressor 21 is low, even if the amount of refrigerant already filled into the refrigerant circuit 6 is appropriate, the superheat of the refrigerant drawn into the high-pressure stage compressor 21 may become lower. On the other hand, if the amount of refrigerant already filled into the refrigerant circuit 6 is appropriate, under the condition that the pressure of the refrigerant drawn into the high-pressure stage compressor 21 is high, the superheat of the refrigerant drawn into the high-pressure stage compressor 21 will also become higher.

[0178] Therefore, even though the pressure of the refrigerant drawn into the high-pressure stage compressor 21 is high, the superheat of the refrigerant drawn into the high-pressure stage compressor 21 is low. It can be determined that the amount of liquid refrigerant flowing from the receiver 15 to the high-pressure stage compressor 21 through the vent pipe 37 is large, and the amount of refrigerant already filled into the refrigerant circuit 6 is excessive.

[0179] Therefore, the refrigerant dosage determination unit 103 in this embodiment does not determine whether the amount of refrigerant filled in the refrigerant circuit 6 is excessive based on the superheat of the refrigerant drawn into the high-pressure stage compressor 21, but rather based on both the pressure and superheat of the refrigerant drawn into the high-pressure stage compressor 21. Therefore, according to this embodiment, the possibility of mistakenly determining that the amount of refrigerant filled in the refrigerant circuit 6 is excessive, even if the amount of refrigerant filled in the refrigerant circuit 6 is appropriate, can be reduced.

[0180] -Features of the first embodiment (3)-

[0181] During the operation of the refrigeration device 1, even if the amount of refrigerant filled in the refrigerant circuit 6 is appropriate, the judgment condition in the refrigerant dosage judgment unit 103 still exists (see reference). Figure 7 The possibility of step ST6) being accidentally fulfilled is reduced. Therefore, the refrigerant dosage determination unit 103 of this embodiment repeatedly determines whether the determination condition is fulfilled. If the number of times the determination condition is fulfilled N reaches the reference number Nc within the period from the elapsed time H to the reference time Hc, it is determined that the amount of refrigerant filled in the refrigerant circuit 6 is excessive. Therefore, according to this embodiment, the possibility of mistakenly determining that the amount of refrigerant filled in the refrigerant circuit 6 is excessive even though the amount of refrigerant filled in the refrigerant circuit 6 is appropriate is reduced.

[0182] (Second Implementation)

[0183] The second embodiment will be described. Here, the differences between the refrigeration device 1 of this embodiment and the refrigeration device 1 of the first embodiment will be explained.

[0184] -Structure of the Refrigeration Unit-

[0185] like Figure 8 As shown, in the refrigeration device 1 of this embodiment, the cooling unit 60 of the first embodiment is omitted. In the refrigerant circuit 6 of the refrigeration device 1 of this embodiment, one heat source unit 10 and multiple air conditioning units 50 are connected through a first liquid connection pipe 2 and a second gas connection pipe 5.

[0186] In the heat source unit 10 of this embodiment, the second low-pressure stage compressor 22, the second low-pressure stage suction pipe 22a, and the second low-pressure stage discharge pipe 22b of the first embodiment are omitted. The compression component C of this embodiment includes the first low-pressure stage compressor 23 and the high-pressure stage compressor 21, but does not include the second low-pressure stage compressor 22.

[0187] The heat source unit 10 in this embodiment includes a reversing valve 80 instead of the flow path switching mechanism 30 in the first embodiment. Similar to the first reversing valve 81 and the second reversing valve 82 in the first embodiment, this reversing valve 80 is composed of a four-way reversing valve 150. The first valve port of the reversing valve 80 is connected to the high-pressure stage outlet pipe 21b, the second valve port is connected to the first low-pressure stage intake pipe 23a, the third valve port is connected to the second outdoor gas pipe 36, and the fourth valve port is connected to the first outdoor gas pipe 35.

[0188] Reversing valve 80 in the first state ( Figure 8 The state shown by the solid line) and the second state ( Figure 8 The directional valve 80 switches between states (shown by the dashed line). In the first state, the first valve port is connected to the third valve port, and the second valve port is connected to the fourth valve port. In the second state, the first valve port is connected to the fourth valve port, and the second valve port is connected to the third valve port.

[0189] - Operation of the refrigeration unit -

[0190] The refrigeration device 1 in this embodiment performs refrigeration operation, heating operation, and defrosting operation.

[0191] During refrigeration operation, the reversing valve 80 is set to the first state. In the refrigerant circuit 6 during refrigeration operation, the first low-pressure stage compressor 23 and the high-pressure stage compressor 21 are working, the outdoor heat exchanger 13 functions as a heat exchanger (gas cooler), and the indoor heat exchangers 54 of each air conditioning unit 50 function as evaporators.

[0192] During heating operation, the reversing valve 80 is set to the second state. In the refrigerant circuit 6 during heating operation, the first low-pressure stage compressor 23 and the high-pressure stage compressor 21 operate, the indoor heat exchanger 54 of each air conditioning unit 50 functions as a heat exchanger (gas cooler), and the outdoor heat exchanger 13 functions as an evaporator.

[0193] The defrosting operation is for melting the frost adhering to the outdoor heat exchanger 13. During heating operation, when the frost adhering to the outdoor heat exchanger 13 reaches a certain level, the refrigeration unit 1 temporarily stops the heating operation and performs the defrosting operation.

[0194] During defrosting operation, the refrigerant flows in the refrigerant circuit 6 as it does during refrigeration operation. Specifically, the reversing valve 80 is set to the first state, and the outdoor heat exchanger 13 functions as a heat exchanger (gas cooler). The frost adhering to the outdoor heat exchanger 13 is melted by the refrigerant heating.

[0195] - Controller Actions -

[0196] The cooling dose determination unit 103 of the controller 101 performs the same operation as in the first embodiment. Therefore, the cooling dose determination unit 103 of this embodiment performs... Figure 7 The action shown determines whether the amount of refrigerant already filled into refrigerant circuit 6 is excessive.

[0197] (Other implementation methods)

[0198] The refrigerant dosage determination unit 103 in the first and second embodiments described above can also be configured to determine that the amount of refrigerant already filled into the refrigerant circuit 6 is excessive when the determination condition is continuously met within a specified time. Alternatively, the refrigerant dosage determination unit 103 in this modified example can also be configured to periodically determine whether the determination condition is met, and when the number of times the determination condition has been continuously met reaches a specified value, it is considered that the determination condition has been continuously met within a specified time, thereby determining that the amount of refrigerant already filled into the refrigerant circuit 6 is excessive.

[0199] The embodiments and modifications have been described above; however, it should be understood that various changes can be made to their form and specific details without departing from the spirit and scope of the claims. Furthermore, the above embodiments and modifications can be appropriately combined or substituted as long as the function of the object of this disclosure is not affected. Additionally, the terms "first," "second," "third," etc., used in the specification and claims are only used to distinguish statements containing these terms and are not intended to limit the number or order of the statements.

[0200] -Industry Applicability-

[0201] In summary, this disclosure is useful for heat source units and refrigeration equipment.

[0202] - Symbol Explanation -

[0203] 1. Refrigeration unit

[0204] 10 Heat source units

[0205] 11. Outdoor circuit (heat source side circuit)

[0206] 13 Outdoor heat exchanger (heat source side heat exchanger)

[0207] 15. Liquid reservoir

[0208] 21 High-pressure stage compressor

[0209] 23 First low-pressure stage compressor (low-pressure stage compressor)

[0210] 37. Venting pipe (venting passage)

[0211] 50 Air conditioning units (using side units)

[0212] 60 Cooling Unit (Utilizing Side Unit)

[0213] 101 Controller

[0214] 103 Cooling Dosage Judgment Unit (Judgment Unit)

Claims

1. A heat source unit (10) which is connected with a utilization side unit (50, 60) to constitute a refrigerant circuit (6) which performs a refrigeration cycle, characterized by: The heat source unit (10) includes a heat source side circuit (11) and a determination section (103), The heat source side circuit (11) has a low-pressure stage compressor (23), a high-pressure stage compressor (21), a heat source side heat exchanger (13), and an accumulator (15), The determination section (103) determines whether the amount of refrigerant filled in the refrigerant circuit (6) is excessive, The heat source side circuit (11) has a gas discharge passage (37) that connects an upper portion of the accumulator (15) to a suction port of the high-pressure stage compressor (21), The determination section (103) determines whether the amount of refrigerant filled in the refrigerant circuit (6) is excessive based on the pressure of the refrigerant sucked into the high-pressure stage compressor (21) and the superheat degree of the refrigerant.

2. The heat source unit according to claim 1, wherein: In a case where the determination condition has been established, the determination section (103) determines that the amount of refrigerant filled in the refrigerant circuit (6) is excessive, The determination condition is a condition in which the pressure of the refrigerant sucked into the high-pressure stage compressor (21) is higher than a reference pressure and the superheat degree of the refrigerant sucked into the high-pressure stage compressor (21) is lower than a reference superheat degree.

3. The heat source unit according to claim 2, wherein: The determination section (103) repeatedly performs determination of whether the determination condition is established, and in a case where the determination condition has been established a plurality of times within a prescribed time, the determination section (103) determines that the amount of refrigerant filled in the refrigerant circuit (6) is excessive.

4. The heat source unit according to any one of claims 1 to 3, wherein: Carbon dioxide is filled in the heat source side circuit (11) as the refrigerant.

5. A refrigeration apparatus characterized by comprising: The refrigeration device includes the heat source unit (10) according to any one of claims 1 to 4 and a utilization side unit (50, 60) connected to the heat source unit (10).

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