Air conditioner

Abstract

An air conditioner (100) comprises: a branch unit (10); a plurality of indoor units (50a, 50b, 50c); an outdoor unit (60); a plurality of forward branch pipes (51a, 51b, 51c) and a plurality of return

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an air conditioning apparatus. BACKGROUND ART

[0002] An air conditioning apparatus including an outdoor unit, a plurality of indoor units and a branch unit, wherein the outdoor unit and the plurality of indoor units are connected through the branch unit, has been conventionally known.

[0003] International Publication No. 2009 / 133640 discloses an air conditioning apparatus in which an outdoor machine (outdoor unit) and a branch unit (branch portion) are connected to each other through a first extension pipe and a second extension pipe, and the branch unit and an indoor machine (indoor unit) are connected to each other through a third extension pipe and a fourth extension pipe. The air conditioning apparatus includes an intermediate heat exchanger disposed in the branch unit.

[0004] In the air conditioning apparatus described in the publication above, heat transfer is performed by circulating refrigerant through the first extension pipe and the second extension pipe in the outdoor machine and the branch unit, and heat transfer is performed by circulating water through the third extension pipe and the fourth extension pipe in the branch unit and the indoor machine. Heat is exchanged between the refrigerant and the water in the intermediate heat exchanger disposed in the branch unit, whereby heat is transferred from the indoor machine through the intermediate heat exchanger in the branch unit to the outdoor machine during a cooling operation and heat is transferred from the outdoor machine through the intermediate heat exchanger in the branch unit to the indoor machine during a heating operation.

[0005] In the air conditioning apparatus described in the publication above, the two pipes are used for connection between the outdoor machine and the branch unit and for connection between the branch unit and the indoor machine, and thus, the cost of piping materials and the man-hours of work can be reduced. CITATION LIST PATENT LITERATURE

[0006] PTL 1: International Publication No. 2009 / 133640 SUMMARY OF INVENTION TECHNICAL PROBLEM

[0007] However, in the air conditioning apparatus described in the publication above, an amount of filled refrigerant in the air conditioning apparatus may increase when the first extension pipe and the second extension pipe between the outdoor machine and the branch unit are installed over a long distance (e.g., 110 meters).

[0008] In addition, when the air conditioning apparatus is placed, the branch unit and the indoor machine, and the outdoor unit may be transported to a placement location on different days. In this case, in the air conditioning apparatus described in the publication above, a test run of the air conditioning apparatus cannot be performed unless the branch unit and the indoor machine, and the outdoor unit all become ready.

[0009] The present disclosure has been made in light of the above-described problems and an object thereof is to provide an air conditioning apparatus in which an amount of filled refrigerant can be reduced and a test run can be performed with a branch unit and an indoor unit. SOLUTION TO PROBLEM

[0010] An air conditioning apparatus according to the present disclosure includes: a branch unit; a plurality of indoor units; an outdoor unit; a plurality of supply branch pipes and a plurality of return branch pipes that connect the branch unit to respective ones of the plurality of indoor units; and a supply main pipe and a return main pipe that connect the branch unit and the outdoor unit to each other. The branch unit includes a first branch header, a second branch header, a first confluence header, a second confluence header, a plurality of first supply branch pipe on-off valves, a plurality of second supply branch pipe on-off valves, a plurality of first return branch pipe on-off valves, a plurality of second return branch pipe on-off valves, a first bypass valve, a second bypass valve, a first pump, a second pump, a first heat exchanger, a second heat exchanger, a first compressor, a first expansion valve, and a first four-way valve that are disposed in the branch unit. The plurality of indoor units include a plurality of indoor heat exchangers disposed in the plurality of indoor units, respectively. One end of each of the plurality of supply branch pipes is connected to the first branch header through a corresponding one of the plurality of first supply branch pipe on-off valves, and connected to the second branch header through a corresponding one of the plurality of second supply branch pipe on-off valves. Another end of each of the plurality of supply branch pipes is connected to one end of a corresponding one of the plurality of indoor heat exchangers. One end of each of the plurality of return branch pipes is connected to the first confluence header through a corresponding one of the plurality of first return branch pipe on-off valves, and connected to the second confluence header through a corresponding one of the plurality of second return branch pipe on-off valves. Another end of each of the plurality of return branch pipes is connected to another end of a corresponding one of the plurality of indoor heat exchangers. The first branch header and the first confluence header are connected to each other through the first bypass valve. The second branch header and the second confluence header are connected to each other through the second bypass valve. The first confluence header, the first pump, the first heat exchanger, and the first branch header are connected together to form a first pipe path that allows a heat medium to flow in order of the first confluence header, the first pump, the first heat exchanger, and the first branch header. The second confluence header, the second pump, the second heat exchanger, and the second branch header are connected together to form a second pipe path that allows the heat medium to flow in order of the second confluence header, the second pump, the second heat exchanger, and the second branch header. The first compressor, the first four-way valve, the first heat exchanger, the first expansion valve, and the second heat exchanger are connected together to form a first refrigerant pipe path that allows refrigerant to flow. The first four-way valve is configured to be switched to cause the refrigerant to flow in order of the first compressor, the first fourway valve, the first heat exchanger, the first expansion valve, the second heat exchanger, and the first four-way valve, or to cause the refrigerant to flow in order of the first compressor, the first four-way valve, the second heat exchanger, the first expansion valve, the first heat exchanger, and the first four-way valve. One end of the supply main pipe is connected to one end of the outdoor unit. Another end of the supply main pipe is connected to the second pipe path. One end of the return main pipe is connected to another end of the outdoor unit. Another end of the return main pipe is connected to the second pipe path. In the first heat exchanger, heat is exchanged between the refrigerant flowing in the first refrigerant pipe path and the heat medium flowing in the first pipe path. In the second heat exchanger, heat is exchanged between the refrigerant flowing in the first refrigerant pipe path and the heat medium flowing in the second pipe path. ADVANTAGEOUS EFFECTS OF INVENTION

[0011] Inthe air conditioning apparatus according to the present disclosure, an amount of filled refrigerant can be reduced and a test run can be performed with a branch unit and an indoor unit. BRIEF DESCRIPTION OF DRAWINGS

[0012] Fig. 1 is a refrigerant circuit diagram of an air conditioning apparatus according to a first embodiment. Fig. 2 is a refrigerant circuit diagram of the air conditioning apparatus according to the first embodiment during a cooling-only operation. Fig. 3 is a refrigerant circuit diagram of the air conditioning apparatus according to the first embodiment during a cooling-dominated operation. Fig. 4 is a refrigerant circuit diagram of the air conditioning apparatus according to the first embodiment during a heating-only operation. Fig. 5 is a refrigerant circuit diagram of the air conditioning apparatus according to the first embodiment during a heating-dominated operation. Fig. 6 is a refrigerant circuit diagram of the air conditioning apparatus according to the first embodiment during a low-outdoor-air cooling operation. Fig. 7 is a refrigerant circuit diagram of an air conditioning apparatus according to a second embodiment. Fig. 8 is a refrigerant circuit diagram of an air conditioning apparatus according to a third embodiment. Fig. 9 is a refrigerant circuit diagram of the air conditioning apparatus according to the third embodiment during a cooling-only operation. Fig. 10 is a refrigerant circuit diagram of the air conditioning apparatus according to the third embodiment during a cooling-dominated operation. Fig. 11 is a refrigerant circuit diagram of the air conditioning apparatus according to the third embodiment during a heating-only operation. Fig. 12 is a refrigerant circuit diagram of the air conditioning apparatus according to the third embodiment during a heating-dominated operation. Fig. 13 is a refrigerant circuit diagram of an air conditioning apparatus according to a fourth embodiment during a defrosting operation. Fig. 14 is a refrigerant circuit diagram of an air conditioning apparatus according to a fifth embodiment. Fig. 15 is a cross-sectional view of a supply branch pipe and a return branch pipe and a supply main pipe and a return main pipe of an air conditioning apparatus according to a sixth embodiment. DESCRIPTION OF EMBODIMENTS

[0013] Embodiments will be described in detail below with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference characters and description thereof will not be repeated in principle.

[0014] First Embodiment. A configuration of an air conditioning apparatus 100 according to a first embodiment will be described with reference to Fig. 1. As shown in Fig. 1, air conditioning apparatus 100 according to the first embodiment includes a branch unit 10, a plurality of indoor units 50a, 50b and 50c, an outdoor unit 60, a plurality of supply branch pipes 51a, 51b and 51c, a plurality of return branch pipes 52a, 52b and 52c, a supply main pipe 61, and a return main pipe 62. The plurality of supply branch pipes 51 and the plurality of return branch pipes 52 connect branch unit 10 to respective ones of the plurality of indoor units 50a, 50b and 50c. In the present embodiment, air conditioning apparatus 100 includes three indoor units 50a, 50b and 50c. Any number of indoor units may be included as long as a plurality of indoor units are included. Supply main pipe 61 and return main pipe 62 connect branch unit 10 and outdoor unit 60 to each other.

[0015] Branch unit 10 has a first branch header 13, a second branch header 23, a first confluence header 16, a second confluence header 26, a plurality of first supply branch pipe on-off valves 14a, 14b and 14c, a plurality of second supply branch pipe on-off valves 24a, 24b and 24c, a plurality of first return branch pipe on-off valves 15a, 15b and 15c, a plurality of second return branch pipe on-off valves 25a, 25b and 25c, a first bypass valve 17, a second bypass valve 27, a first pump 11, a second pump 21, a first heat exchanger 12, a second heat exchanger 22, a first compressor 31, a first expansion valve 32, and a first four-way valve 18 that are disposed in branch unit 10.

[0016] The plurality of indoor units 50a, 50b and 50c have a plurality of indoor heat exchangers 53a, 53b and 53c disposed in the plurality of indoor units 50a, 50b and 50c, respectively. The plurality of indoor units 50a, 50b and 50c have indoor blowers 54a, 54b and 54c disposed in the plurality of indoor units 50a, 50b and 50c, respectively.

[0017] One end of each of the plurality of supply branch pipes 5 la, 5 lb and 51c is connected to first branch header 13 through a corresponding one of the plurality of first supply branch pipe on-off valves 14a, 14b and 14c, and connected to second branch header 23 through a corresponding one of the plurality of second supply branch pipe on-off valves 24a, 24b and 24c.

[0018] Each of the plurality of first supply branch pipe on-off valves 14a, 14b and 14c opens and closes a pipe path that connects a corresponding one of the plurality of supply branch pipes 51a, 51b and 51c to first branch header 13. Each of the plurality of second supply branch pipe on-off valves 24a, 24b and 24c opens and closes a pipe path that connects a corresponding one of the plurality of supply branch pipes 51a, 51b and 51c to second branch header 23. The pipe path that connects a corresponding one of the plurality of supply branch pipes 51 a, 5 lb and 51c to second branch header 23 branches off from the pipe path that connects a corresponding one of the plurality of supply branch pipes 51a, 51b and 51c to first branch header 13.

[0019] Another end of each of the plurality of supply branch pipes 51a, 51b and 51c is connected to one end of a corresponding one of the plurality of indoor heat exchangers 53a, 53b and 53c.

[0020] One end of each of the plurality of return branch pipes 52a, 52b and 52c is connected to first confluence header 16 through a corresponding one of the plurality of first return branch pipe on-off valves 15a, 15b and 15c, and connected to second confluence header 26 through a corresponding one of the plurality of second return branch pipe on-off valves 25a, 25b and 25c.

[0021] Each of the plurality of first return branch pipe on-off valves 15a, 15b and 15c opens and closes a pipe path that connects a corresponding one of the plurality of return branch pipes 52a, 52b and 52c to first confluence header 16. Each of the plurality of second return branch pipe on-off valves 25a, 25b and 25c opens and closes a pipe path that connects a corresponding one of the plurality of return branch pipes 52a, 52b and 52c to second confluence header 26. The pipe path that connects a corresponding one of the plurality of return branch pipes 52a, 52b and 52c to second confluence header 26 branches off from the pipe path that connects a corresponding one of the plurality of return branch pipes 52a, 52b and 52c to first confluence header 16.

[0022] Another end of each of the plurality of return branch pipes 52a, 52b and 52c is connected to another end of a corresponding one of the plurality of indoor heat exchangers 53a, 53b and 53c.

[0023] First branch header 13 and first confluence header 16 are connected to each other through first bypass valve 17. First bypass valve 17 opens and closes a bypass path that connects first branch header 13 to first confluence header 16.

[0024] Second branch header 23 and second confluence header 26 are connected to each other through second bypass valve 27. Second bypass valve 27 opens and closes a bypass path that connects second branch header 23 to second confluence header 26.

[0025] First confluence header 16, first pump 11, first heat exchanger 12, and first branch header 13 are connected together to form a first pipe path Pl that allows a heat medium to flow in order of first confluence header 16, first pump 11, first heat exchanger 12, and first branch header 13. First confluence header 16, first pump 11, first heat exchanger 12, and first branch header 13 are connected by a pipe, thereby forming first pipe path Pl.

[0026] Second confluence header 26, second pump 21, second heat exchanger 22, and second branch header 23 are connected together to form a second pipe path P2 that allows the heat medium to flow in order of second confluence header 26, second pump 21, second heat exchanger 22, and second branch header 23. Second confluence header 26, second pump 21, second heat exchanger 22, and second branch header 23 are connected by a pipe, thereby forming second pipe path P2.

[0027] First compressor 31, first four-way valve 18, first heat exchanger 12, first expansion valve 32, and second heat exchanger 22 are connected together to form a first refrigerant pipe path RI that allows refrigerant to flow. First compressor 31, first four-way valve 18, first heat exchanger 12, first expansion valve 32, and second heat exchanger 22 are connected by a pipe, thereby forming first refrigerant pipe path RI. First refrigerant pipe path RI has a refrigeration cycle.

[0028] First four-way valve 18 is configured to be switched to cause the refrigerant to flow in order of first compressor 31, first four-way valve 18, first heat exchanger 12, first expansion valve 32, second heat exchanger 22, and first four-way valve 18, or to cause the refrigerant to flow in order of first compressor 31, first four-way valve 18, second heat exchanger 22, first expansion valve 32, first heat exchanger 12, and first four-way valve 18.

[0029] One end of supply main pipe 61 is connected to one end of outdoor unit 60. Another end of supply main pipe 61 is connected to second pipe path P2. The other end of supply main pipe 61 may be detachably connected to second pipe path P2. A connection portion between second pipe path P2 and the other end of supply main pipe 61 is configured to be capable of closing second pipe path P2.

[0030] One end of return main pipe 62 is connected to another end of outdoor unit 60. Another end of return main pipe 62 is connected to second pipe path P2. The other end of return main pipe 62 may be detachably connected to second pipe path P2. A connection portion between second pipe path P2 and the other end of return main pipe 62 is configured to be capable of closing second pipe path P2.

[0031] The connection portion between second pipe path P2 and the other end of supply main pipe 61 closes second pipe path P2 and the connection portion between second pipe path P2 and the other end of return main pipe 62 closes second pipe path P2, whereby second pipe path P2 forms a closed circuit.

[0032] In first heat exchanger 12, heat is exchanged between the refrigerant flowing in first refrigerant pipe path RI and the heat medium flowing in first pipe path Pl.

[0033] In second heat exchanger 22, heat is exchanged between the refrigerant flowing in first refrigerant pipe path RI and the heat medium flowing in second pipe path P2.

[0034] Branch unit 10 has a flow rate adjustment valve 33 disposed in branch unit 10 and disposed in second pipe path P2. Flow rate adjustment valve 33 opens and closes second pipe path P2. Flow rate adjustment valve 33 is connected between a point of branch from supply main pipe 61 and a point of confluence with return main pipe 62 in second pipe path P2.

[0035] Outdoor unit 60 has a cooling tower 63 disposed in outdoor unit 60. Cooling tower 63 and branch unit 10 are connected to each other through supply main pipe 61 and return main pipe 62. Outdoor unit 60 has a blower 64 disposed in outdoor unit 60.

[0036] The one end of supply main pipe 61 is connected to one end of cooling tower 63. The other end of supply main pipe 61 is connected between second pump 21 and second heat exchanger 22 in second pipe path P2. The other end of supply main pipe 61 is connected to a pipe that connects second pump 21 and second heat exchanger 22 to each other in second pipe path P2.

[0037] The one end of return main pipe 62 is connected to another end of cooling tower 63. The other end of return main pipe 62 is connected between second pump 21 and second heat exchanger 22 in second pipe path P2. The other end of return main pipe 62 is connected to the pipe that connects second pump 21 and second heat exchanger 22 to each other in second pipe path P2.

[0038] A capacity of second pump 21 is larger than a capacity of first pump 11. <Operation of Air Conditioning Apparatus> Air conditioning apparatus 100 performs a cooling-only operation, a cooling-dominated operation, a heating-only operation, a heating-dominated operation, or a low-outdoor-air cooling operation, depending on operation modes of the plurality of indoor units 50a, 50b and 50c and the outdoor air temperature. When the plurality of indoor units 50a, 50b and 50c in operation are all in a cooling operation mode, air conditioning apparatus 100 performs the cooling-only operation. When the plurality of indoor units 50a, 50b and 50c in operation are all in a heating operation mode, air conditioning apparatus 100 performs the heating-only operation. The cooling operation mode and the heating operation mode may coexist in the plurality of indoor units 50a, 50b and 50c in operation. When a total of air conditioning loads of the indoor units in the cooling operation mode is larger than a total of air conditioning loads of the indoor units in the heating operation mode, air conditioning apparatus 100 performs the cooling-dominated operation. When the total of the air conditioning loads of the indoor units in the heating operation mode is larger than the total of the air conditioning loads of the indoor units in the cooling operation mode, air conditioning apparatus 100 performs the heating-dominated operation. When the plurality of indoor units 50a, 50b and 50c in operation are all in the cooling operation mode and the outdoor temperature is sufficiently lower than the indoor temperature (e.g., when the outdoor air temperature is equal to or lower than 5 °C), air conditioning apparatus 100 performs the low-outdoor-air cooling operation.

[0039] <Cooling-Only Operation> The cooling-only operation of air conditioning apparatus 100 will be described with reference to Fig. 2. As shown in Fig. 2, when all of the plurality of indoor units 50a, 50b and 50c operate in the cooling operation mode, air conditioning apparatus 100 performs the cooling-only operation. In the cooling-only operation, the plurality of first supply branch pipe on-off valves 14a, 14b and 14c, the plurality of first return branch pipe on-off valves 15a, 15b and 15c, and second bypass valve 27 are opened and the plurality of second supply branch pipe on-off valves 24a, 24b and 24c, the plurality of second return branch pipe on-off valves 25a, 25b and 25c, first bypass valve 17, and flow rate adjustment valve 33 are closed. Thus, a cold water circuit extending from first pump 11 through first heat exchanger 12, first branch header 13, the plurality of first supply branch pipe on-off valves 14a, 14b and 14c, the plurality of supply branch pipes 51 a, 5 lb and 51c, the plurality of indoor heat exchangers 53a, 53b and 53c, the plurality of return branch pipes 52a, 52b and 52c, the plurality of first return branch pipe on-off valves 15a, 15b and 15 c, and first confluence header 16 to again reach first pump 11 is formed. In addition, a hot water circuit extending from second pump 21 through supply main pipe 61, cooling tower 63, return main pipe 62, second heat exchanger 22, second branch header 23, second bypass valve 27, and second confluence header 26 to again reach second pump 21 is formed.

[0040] In the refrigeration cycle, a refrigerant circuit in which the refrigerant flows from first compressor 31 through first four-way valve 18, second heat exchanger 22, first expansion valve 32, first heat exchanger 12, and first four-way valve 18 to again reach first compressor 31 is formed. In this case, second heat exchanger 22 functions as a condenser and first heat exchanger 12 functions as an evaporator.

[0041] First, an operation of the refrigeration cycle will be described. Gas singlephase refrigerant discharged from first compressor 31 flows through first four-way valve 18 into second heat exchanger 22 and condenses into liquid single-phase refrigerant by heat exchange with the heat medium of the hot water circuit flowing in second heat exchanger 22. The liquid single-phase refrigerant flowing out from second heat exchanger 22 flows into first expansion valve 32 and is decompressed and expanded into gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant flows into first heat exchanger 12 and evaporates into gas single-phase refrigerant by heat exchange with the heat medium of the cold water circuit flowing in first heat exchanger 12. The gas single-phase refrigerant flowing out from first heat exchanger 12 is again suctioned into first compressor 31 and circulates in the refrigerant circuit.

[0042] Next, an operation of the cold water circuit will be described. The heat medium circulating in the cold water circuit is water or antifreeze. The heat medium flowing out from first pump 11 is cooled by heat exchange with the refrigerant in first heat exchanger 12, and flows through first branch header 13, the plurality of first supply branch pipe on-off valves 14a, 14b and 14c, and the plurality of supply branch pipes 51a, 51b and 51c into the plurality of indoor heat exchangers 53a, 53b and 53c in the plurality of indoor units 50a, 50b and 50c. While the plurality of indoor units 50a, 50b and 50c are in operation, the plurality of indoor blowers 54a, 54b and 54c are operating and the heat medium cools the indoor air blown by the plurality of indoor blowers 54a, 54b and 54c in the plurality of indoor heat exchangers 53a, 53b and 53c. The heat medium increased in temperature by heat exchange with the indoor air flows through the plurality of return branch pipes 52a, 52b and 52c, the plurality of first return branch pipe on-off valves 15a, 15b and 15 c, and first confluence header 16 into first pump 11 and circulates in the cold water circuit.

[0043] Finally, an operation of the hot water circuit will be described. The heat medium circulating in the hot water circuit is water or antifreeze. The heat medium flowing out from second pump 21 flows through supply main pipe 61 to cooling tower 63 and releases heat to the outdoor air. The heat medium decreased in temperature by heat release to the outdoor air flows through return main pipe 62 into second heat exchanger 22 in branch unit 10 and is heated by heat exchange with the refrigerant. The heat medium increased in temperature by heat exchange with the refrigerant flows through second branch header 23, second bypass valve 27 and second confluence header 26 into second pump 21 and circulates in the hot water circuit.

[0044] The refrigeration cycle in branch unit 10 generates cold heat required by the plurality of indoor units 50a, 50b and 50c during the cooling operation. The cold water circuit supplies the low-temperature heat medium to the plurality of indoor units 50a, 50b and 50c through first heat exchanger 12. The hot waste heat generated during the refrigeration cycle operation is transferred to the high-temperature heat medium through second heat exchanger 22 and is discharged from cooling tower 63 in outdoor unit 60 by the hot water circuit. <Cooling-Dominated Operation> The cooling-dominated operation of air conditioning apparatus 100 will be described with reference to Fig. 3. As shown in Fig. 3, when the plurality of indoor units 50a and 50b operate in the cooling operation mode and indoor unit 50c operates in the heating operation mode, air conditioning apparatus 100 performs the cooling-dominated operation. In the cooling-dominated operation, the plurality of first supply branch pipe on-off valves 14a and 14b, the plurality of first return branch pipe on-off valves 15a and 15b, second supply branch pipe on-off valve 24c, second return branch pipe on-off valve 25 c, and second bypass valve 27 are opened and first supply branch pipe on-off valve 14c, first return branch pipe on-off valve 15c, first bypass valve 17, the plurality of second supply branch pipe on-off valves 24a and 24b, the plurality of second return branch pipe on-off valves 25a and 25b, and flow rate adjustment valve 33 are closed. Thus, a cold water circuit extending from first pump 11 through first heat exchanger 12, first branch header 13, the plurality of first supply branch pipe on-off valves 14a and 14b, the plurality of supply branch pipes 51a and 51b, the plurality of indoor heat exchangers 53a and 53b, the plurality of return branch pipes 52a and 52b, the plurality of first return branch pipe on-off valves 15a and 15b, and first confluence header 16 to again reach first pump 11 is formed. In addition, a hot water circuit extending from second pump 21 through supply main pipe 61, cooling tower 63, return main pipe 62, second heat exchanger 22, second branch header 23, second supply branch pipe on-off valve 24c, supply branch pipe 51c, indoor heat exchanger 53c, return branch pipe 52c, second return branch pipe on-off valve 25c, and second confluence header 26, or through second branch header 23, second bypass valve 27 and second confluence header 26, to again reach second pump 21 is formed.

[0045] An operation of the refrigeration cycle is the same as that during the cooling- only operation. In addition, an operation of the cold water circuit is also similar to that during the cooling-only operation.

[0046] Next, an operation of the hot water circuit will be described. The heat medium flowing out from second pump 21 flows through supply main pipe 61 to cooling tower 63 and releases heat to the outdoor air. The heat medium decreased in temperature by heat release to the outdoor air flows through return main pipe 62 into second heat exchanger 22 in branch unit 10 and is heated by heat exchange with the refrigerant. The heat medium increased in temperature by heat exchange with the refrigerant flows through second branch header 23, second supply branch pipe on-off valve 24c and supply branch pipe 51a into indoor heat exchanger 53c in indoor unit 50c. While indoor unit 50c is in operation, indoor blower 54c is operating and the heat medium heats the indoor air blown by indoor blower 54c in indoor heat exchanger 53c. The heat medium decreased in temperature by heat exchange with the indoor air flows through return branch pipe 52c and second return branch pipe on-off valve 25c to second confluence header 26. The remaining heat medium that is not conveyed to indoor heat exchanger 53c flows through second bypass valve 27 to second confluence header 26, merges with the heat medium returning from indoor heat exchanger 53c and flows into first pump 11, and circulates in the hot water circuit.

[0047] The refrigeration cycle in branch unit 10 generates cold heat required by the plurality of indoor units 50a and 50b during the cooling operation. The cold water circuit supplies the low-temperature heat medium to the plurality of indoor units 50a and 50b through first heat exchanger 12. The hot heat generated during the refrigeration cycle operation is supplied through second heat exchanger 22 to indoor unit 50c during the heating operation by the hot water circuit, and the remaining hot waste heat is discharged from cooling tower 63 in outdoor unit 60 by the hot water circuit.

[0048] When an amount of hot waste heat in cooling tower 63 is small, second bypass valve 27 may be closed. When the amount of hot waste heat in cooling tower 63 is large, second bypass valve 27 is opened, thereby reducing a flow rate of the heat medium flowing through indoor heat exchanger 53c to prevent the excessive hot waste heat from indoor heat exchanger 53c to the indoor space.

[0049] When an amount of hot waste heat in outdoor unit 60 is small, flow rate adjustment valve 33 may be opened. Generally, branch unit 10 and outdoor unit 60 are placed at a distance. Therefore, by opening flow rate adjustment valve 33, a flow rate of the heat medium flowing through supply main pipe 61 and return main pipe 62 can be reduced, which leads to a reduction in power consumption of second pump 21 caused by pipe friction losses in supply main pipe 61 and in return main pipe 62.

[0050] <Heating-Only Operation> The heating-only operation of air conditioning apparatus 100 will be described with reference to Fig. 4. As shown in Fig. 4, when all of the plurality of indoor units 50a, 50b and 50c operate in the heating operation mode, air conditioning apparatus 100 performs the heating-only operation. The plurality of first supply branch pipe on-off valves 14a, 14b and 14c, the plurality of first return branch pipe on-off valves 15a, 15b and 15c, and second bypass valve 27 are opened and the plurality of second supply branch pipe on-off valves 24a, 24b and 24c, the plurality of second return branch pipe on-off valves 25a, 25b and 25c, first bypass valve 17, and flow rate adjustment valve 33 are closed. Thus, a hot water circuit extending from first pump 11 through first heat exchanger 12, first branch header 13, the plurality of first supply branch pipe on-off valves 14a, 14b and 14c, the plurality of supply branch pipes 51a, 51b and 51c, the plurality of indoor heat exchangers 53a, 53b and 53c, the plurality of return branch pipes 52a, 52b and 52c, the plurality of first return branch pipe on-off valves 15a, 15b and 15 c, and first confluence header 16 to again reach first pump 11 is formed. In addition, a cold water circuit extending from second pump 21 through supply main pipe 61, cooling tower 63, return main pipe 62, second heat exchanger 22, second branch header 23, second bypass valve 27, and second confluence header 26 to again reach second pump 21 is formed.

[0051] In the refrigeration cycle, a refrigerant circuit in which the refrigerant flows from first compressor 31 through first four-way valve 18, first heat exchanger 12, first expansion valve 32, second heat exchanger 22, and first four-way valve 18 to again reach first compressor 31 is formed. In this case, first heat exchanger 12 functions as a condenser and second heat exchanger 22 functions as an evaporator.

[0052] First, an operation of the refrigeration cycle will be described. Gas singlephase refrigerant discharged from first compressor 31 flows through first four-way valve 18 into first heat exchanger 12 and condenses into liquid single-phase refrigerant by heat exchange with the heat medium of the hot water circuit flowing in first heat exchanger 12. The liquid single-phase refrigerant flowing out from first heat exchanger 12 flows into first expansion valve 32 and is decompressed and expanded into gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant flows into second heat exchanger 22 and evaporates into gas single-phase refrigerant by heat exchange with the heat medium of the cold water circuit flowing in second heat exchanger 22. The gas single-phase refrigerant flowing out from second heat exchanger 22 is again suctioned into first compressor 31 and circulates in the refrigerant circuit.

[0053] Next, an operation of the hot water circuit will be described. The heat medium circulating in the hot water circuit is water or antifreeze. The heat medium flowing out from first pump 11 is heated by heat exchange with the refrigerant in first heat exchanger 12, and flows through first branch header 13, the plurality of first supply branch pipe on-off valves 14a, 14b and 14c, and the plurality of supply branch pipes 51a, 51b and 51c into the plurality of indoor heat exchangers 53a, 53b and 53c in the plurality of indoor units 50a, 50b and 50c. While the plurality of indoor units 50a, 50b and 50c are in operation, the plurality of indoor blowers 54a, 54b and 54c are operating and the heat medium heats the indoor air blown by the plurality of indoor blowers 54a, 54b and 54c in the plurality of indoor heat exchangers 53a, 53b and 53c. The heat medium decreased in temperature by heat exchange with the indoor air flows through the plurality of return branch pipes 52a, 52b and 52c, the plurality of first return branch pipe on-off valves 15a, 15b and 15 c, and first confluence header 16 into first pump 11 and circulates in the hot water circuit.

[0054] Finally, an operation of the cold water circuit will be described. The heat medium circulating in the cold water circuit is water or antifreeze. The heat medium flowing out from second pump 21 flows through supply main pipe 61 to cooling tower 63 and absorbs heat from the outdoor air. The heat medium increased in temperature by heat absorption from the outdoor air flows through return main pipe 62 into second heat exchanger 22 in branch unit 10 and is cooled by heat exchange with the refrigerant. The heat medium decreased in temperature by heat exchange with the refrigerant flows through second branch header 23, second bypass valve 27 and second confluence header 26 into second pump 21 and circulates in the cold water circuit.

[0055] The refrigeration cycle in branch unit 10 generates hot heat required by the plurality of indoor units 50a, 50b and 50bc during the heating operation. The hot water circuit supplies the high-temperature heat medium to indoor units 50a, 50b and 50c through first heat exchanger 12. The cold waste heat generated during the refrigeration cycle operation is transferred to the low-temperature heat medium through second heat exchanger 22 and is discharged from cooling tower 63 in outdoor unit 60 by the cold water circuit.

[0056] <Heating-Dominated Operation> The heating-dominated operation of air conditioning apparatus 100 will be described with reference to Fig. 5. As shown in Fig. 5, when the plurality of indoor units 50a and 50b operate in the heating operation mode and indoor unit 50c operates in the cooling operation mode, air conditioning apparatus 100 performs the heating-dominated operation. In the heating-dominated operation, the plurality of first supply branch pipe on-off valves 14a and 14b, the plurality of first return branch pipe on-off valves 15a and 15b, second supply branch pipe on-off valve 24c, second return branch pipe on-off valve 25 c, and second bypass valve 27 are opened and first supply branch pipe on-off valve 14c, first return branch pipe on-off valve 15c, first bypass valve 17, the plurality of second supply branch pipe on-off valves 24a and 24b, the plurality of second return branch pipe on-off valves 25a and 25b, and flow rate adjustment valve 33 are closed. Thus, a hot water circuit extending from first pump 11 through first heat exchanger 12, first branch header 13, the plurality of first supply branch pipe on-off valves 14a and 14b, the plurality of supply branch pipes 51a and 51b, the plurality of indoor heat exchangers 53a and 53b, the plurality of return branch pipes 52a and 52b, the plurality of first return branch pipe on-off valves 15a and 15b, and first confluence header 16 to again reach first pump 11 is formed. In addition, a cold water circuit extending from second pump 21 through supply main pipe 61, cooling tower 63, return main pipe 62, second heat exchanger 22, second branch header 23, second supply branch pipe on-off valve 24c, supply branch pipe 51c, indoor heat exchanger 53c, return branch pipe 52c, second return branch pipe on-off valve 25c, and second confluence header 26, or through second branch header 23, second bypass valve 27 and second confluence header 26, to again reach second pump 21 is formed.

[0057] An operation of the refrigeration cycle is the same as that during the heating-only operation. In addition, an operation of the hot water circuit is also similar to that during the heating-only operation.

[0058] Next, an operation of the cold water circuit will be described. The heat medium flowing out from second pump 21 flows through supply main pipe 61 to cooling tower 63 and absorbs heat from the outdoor air. The heat medium increased in temperature by heat absorption from the outdoor air flows through return main pipe 62 into second heat exchanger 22 in branch unit 10 and is cooled by heat exchange with the refrigerant. The heat medium decreased in temperature by heat exchange with the refrigerant flows through second branch header 23, second supply branch pipe on-off valve 24c and supply branch pipe 51a into indoor heat exchanger 53c in indoor unit 50c. While indoor unit 50c is operating, indoor blower 54c is operating and the heat medium cools the indoor air blown by indoor blower 54c in indoor heat exchanger 53c. The heat medium increased in temperature by heat exchange with the indoor air flows through return branch pipe 52c and second return branch pipe on-off valve 25c to second confluence header 26. The remaining heat medium that is not conveyed to indoor heat exchanger 53c flows through second bypass valve 27 to second confluence header 26, merges with the heat medium returning from indoor heat exchanger 53c and flows into second pump 21, and circulates in the cold water circuit.

[0059] The refrigeration cycle in branch unit 10 generates hot heat required by the plurality of indoor units 50a and 50b during the heating operation. The hot water circuit supplies the high-temperature heat medium to the plurality of indoor units 50a and 50b through first heat exchanger 12. The cold heat generated during the refrigeration cycle operation is supplied through second heat exchanger 22 to indoor unit 50c during the cooling operation by the cold water circuit, and the remaining cold waste heat is discharged from cooling tower 63 in outdoor unit 60 by the cold water circuit.

[0060] When an amount of cold waste heat in outdoor unit 60 is small, second bypass valve 27 may be closed. When the amount of cold waste heat in outdoor unit 60 is large, second bypass valve 27 is opened, thereby reducing a flow rate of the heat medium flowing through indoor heat exchanger 53c to prevent excessing cooling from indoor heat exchanger 53c to the indoor space.

[0061] When the amount of cold waste heat in outdoor unit 60 is small, flow rate adjustment valve 33 may be opened. Generally, branch unit 10 and outdoor unit 60 are placed at a distance. Therefore, by opening flow rate adjustment valve 33, a flow rate of the heat medium flowing through supply main pipe 61 and return main pipe 62 can be reduced, which leads to a reduction in power consumption of second pump 21 caused by pipe friction losses in supply main pipe 61 and in return main pipe 62. <Low-Outdoor-Air Cooling Operation> The low-outdoor-air cooling operation of air conditioning apparatus 100 will be described with reference to Fig. 6. As shown in Fig. 6, when all of the plurality of indoor units 50a, 50b and 50c operate in the cooling operation mode and the outdoor temperature is sufficiently lower than the indoor temperature (e.g., when the outdoor air temperature is equal to or lower than 5°C), air conditioning apparatus 100 performs the low-outdoor-air cooling operation. In the low-outdoor-air cooling operation, the plurality of second supply branch pipe on-off valves 24a, 24b and 24c and the plurality of second return branch pipe on-off valves 25a, 25b and 25c are opened and the plurality of first supply branch pipe on-off valves 14a, 14b and 14c, the plurality of first return branch pipe on-off valves 15a, 15b and 15 c, first bypass valve 17, second bypass valve 27, and flow rate adjustment valve 33 are closed. Thus, a cold water circuit extending from second pump 21 through supply main pipe 61, cooling tower 63, return main pipe 62, second heat exchanger 22, second branch header 23, the plurality of second supply branch pipe on-off valves 24a, 24b and 24c, the plurality of supply branch pipes 51a, 51b and 51c, the plurality of indoor heat exchangers 53a, 53b and 53c, the plurality of return branch pipes 52a, 52b and 52c, the plurality of second return branch pipe on-off valves 25 a, 25b and 25 c, and second confluence header 26 to again reach second pump 21 is formed.

[0062] In this case, first compressor 31 in the refrigeration cycle is not operating and first heat exchanger 12 and second heat exchanger 22 do not act as hot and cold heat sources.

[0063] Next, an operation of the cold water circuit will be described. The heat medium flowing out from second pump 21 flows through supply main pipe 61 to cooling tower 63 and releases heat to the outdoor air. The heat medium decreased in temperature by heat release to the outdoor air flows through return main pipe 62 and through second heat exchanger 22, second branch header 23, the plurality of second supply branch pipe on-off valves 24a, 24b and 24c, and the plurality of supply branch pipes 51a, 51b and 51c in branch unit 10 into indoor heat exchangers 53a, 53b and 53c in the plurality of indoor units 50a, 50b and 50c. While the plurality of indoor units 50a, 50b and 50c are in operation, the plurality of indoor blowers 54a, 54b and 54c are operating and the heat medium cools the indoor air blown by the plurality of indoor blowers 54a, 54b and 54c in the plurality of indoor heat exchangers 53a, 53b and 53c. The heat medium increased in temperature by heat exchange with the indoor air flows through the plurality of second return branch pipe on-off valves 25 a, 25b and 25c and second confluence header 26 into second pump 21 and circulates in the cold water circuit.

[0064] The cold heat required by the plurality of indoor units 50a, 50b and 50c during the cooling operation is all provided by heat absorption from the outdoor air having a temperature lower than the indoor temperature and cold heat transfer by the cold water circuit. In the low-outdoor-air cooling operation, the operation of first compressor 31 in the refrigeration cycle is stopped, the low-temperature outdoor air is directly used as a cold heat source, and only second pump 21 is operated. Therefore, the cooling operation of the plurality of indoor units 50a, 50b and 50c can be achieved with low power consumption.

[0065] <Functions and Effects> In air conditioning apparatus 100 according to the first embodiment, branch unit 10 is connected to respective ones of the plurality of indoor units 50a, 50b and 50c by the plurality of supply branch pipes 51 and the plurality of return branch pipes 52, and first refrigerant pipe path RI is disposed in branch unit 10. Therefore, the refrigerant flows only in branch unit 10. Thus, as compared with the case in which the refrigerant flows through the plurality of indoor units 50a, 50b and 50c and outdoor unit 60, an amount of filled refrigerant can be reduced. The reduction in amount of filled refrigerant can lead to a reduction in refrigerant cost. The reduction in amount of filled refrigerant can also lead to a reduction in influence on global warming by the refrigerant.

[0066] In addition, branch unit 10 is connected to respective ones of the plurality of indoor units 50a, 50b and 50c by the plurality of supply branch pipes 51 and the plurality of return branch pipes 52, and first pipe path Pl, second pipe path P2 and first refrigerant pipe path RI are disposed in branch unit 10. In first heat exchanger 12 disposed in branch unit 10, heat is exchanged between the refrigerant flowing in first refrigerant pipe path RI and the heat medium flowing in first pipe path Pl. In second heat exchanger 22 disposed in branch unit 10, heat is exchanged between the refrigerant flowing in first refrigerant pipe path RI and the heat medium flowing in second pipe path P2. Therefore, heat exchange between the refrigerant and the heat medium can be performed between branch unit 10 and the plurality of indoor units 50a, 50b and 50c. Thus, a test run can be performed with branch unit 10 and the plurality of indoor units 50a, 50b and 50c.

[0067] In air conditioning apparatus 100 according to the first embodiment, flow rate adjustment valve 33 is connected between the point of branch from supply main pipe 61 and the point of confluence with return main pipe 62 in second pipe path P2. Therefore, by opening flow rate adjustment valve 33, the flow rate of the heat medium flowing through supply main pipe 61 and return main pipe 62 can be reduced, which leads to a reduction in power consumption of second pump 21 caused by pipe friction losses in supply main pipe 61 and in return main pipe 62.

[0068] In air conditioning apparatus 100 according to the first embodiment, outdoor unit 60 has cooling tower 63 disposed in outdoor unit 60. Therefore, during the refrigeration cycle operation, an excessive amount of heat in the hot heat source or the cold heat source when the plurality of indoor units 50a, 50b and 50c perform cooling and heating can be discharged in cooling tower 63. Thus, the cooling and heating capacities of the plurality of indoor units 50a, 50b and 50c can be adjusted without excess or deficiency.

[0069] In air conditioning apparatus 100 according to the first embodiment, the hot heat and the cold heat generated by the refrigeration cycle in branch unit 10 can be used to perform switching among the cooling-only operation, the cooling-dominated operation, the heating-only operation, and the heating-dominated operation in accordance with a setting of each of the plurality of indoor units 50a, 50b and 50c in each of the cooling operation mode and the heating operation mode. For example, in an air conditioning facility of a large-scale building, there is a case in which when an operation state of an indoor unit disposed in a general room is set to heating, an operation state of an indoor unit disposed in a room such as a computer room or a kitchen where an amount of heat generation is large is set to cooling. Air conditioning apparatus 100 according to the first embodiment is suitable for such an air conditioning facility.

[0070] In air conditioning apparatus 100 according to the first embodiment, the capacity of second pump 21 is larger than the capacity of first pump 11. The larger capacity of second pump 21 in second pipe path P2 connected to outdoor unit 60 makes it easier to supply the heat medium to outdoor unit 60 by second pump 21.

[0071] Furthermore, in air conditioning apparatus 100 according to the first embodiment, the refrigeration cycle is provided only in branch unit 10 and heat transfer between branch unit 10 and the plurality of indoor units 50a, 50b and 50c and between branch unit 10 and cooling tower 63 is performed with the heat medium (water or antifreeze). Therefore, the amount of filled refrigerant can be reduced regardless of the pipe length between branch unit 10 and the plurality of indoor units 50a, 50b and 50c and the pipe length between branch unit 10 and cooling tower 63.

[0072] Additionally, in air conditioning apparatus 100 according to the first embodiment, the two pipes are used for connection between branch unit 10 and the plurality of indoor units 50a, 50b and 50c and for connection between branch unit 10 and cooling tower 63. Therefore, particularly when a distance between branch unit 10 and the indoor units or a distance between branch unit 10 and cooling tower 63 is long, the time and effort required for installation can be reduced. In addition, generally, an internal pressure of a refrigerant pipe is high (up to about 4 megapascals) and thus the difficulty of installation thereof is high, whereas an internal pressure of a water pipe is relatively low (generally, less than 1 megapascal at most) and thus the water pipe can be installed more easily than the refrigerant pipe.

[0073] In addition, in the low-outdoor-air cooling operation, when the outdoor air temperature is sufficiently lower than the indoor temperature of the room in which the plurality of indoor units 50a, 50b and 50c during the cooling operation are placed, the operation of first compressor 31 in the refrigeration cycle is stopped, the low-temperature outdoor air is directly used as a cold heat source, and only second pump 21 is operated. Therefore, the cooling operation of the plurality of indoor units 50a, 50b and 50c can be achieved with low power consumption.

[0074] As described above, in air conditioning apparatus 100 according to the first embodiment, a reduction in amount of filled refrigerant, a reduction in difficulty of installation and installation cost, and the energy-saving operation in the low-outdoor-air cooling operation can be achieved at the same time.

[0075] Second Embodiment. Air conditioning apparatus 100 according to a second embodiment is identical to air conditioning apparatus 100 according to the first embodiment in terms of configuration, operations, and functions and effects, unless otherwise described.

[0076] A configuration of air conditioning apparatus 100 according to the second embodiment will be described with reference to Fig. 7. As shown in Fig. 7, air conditioning apparatus 100 according to the second embodiment has an underground heat exchanger 70, instead of cooling tower 63.

[0077] Outdoor unit 60 has underground heat exchanger 70 disposed in outdoor unit 60. Underground heat exchanger 70 and branch unit 10 are connected to each other through supply main pipe 61 and return main pipe 62.

[0078] The one end of supply main pipe 61 is connected to one end of underground heat exchanger 70. The other end of supply main pipe 61 is connected between second pump 21 and second heat exchanger 22 in second pipe path P2. The one end of return main pipe 62 is connected to another end of underground heat exchanger 70. The other end of return main pipe 62 is connected between second pump 21 and second heat exchanger 22 in second pipe path P2.

[0079] Next, functions and effects of air conditioning apparatus 100 according to the second embodiment will be described. From the perspective of preventing freezing of the heat medium (water or antifreeze) flowing through second pipe path P2 and suppressing an increase in viscosity thereof, a minimum temperature needs to be set for the heat medium.

[0080] In air conditioning apparatus 100 according to the first embodiment, in the case where the heating-only operation or the heating-dominated operation is performed when the outdoor air temperature is, for example, below zero, extraction of heat from the outdoor air in cooling tower 63 is difficult.

[0081] Air conditioning apparatus 100 according to the second embodiment has underground heat exchanger 70. Generally, the underground temperature is between 15°C and 25°C and is stable throughout the year, as compared with the outdoor air temperature. Therefore, underground heat exchanger 70 makes extraction of heat from the outdoor air easier, and thus, the heating-only operation or the heating-dominated operation can be stably achieved.

[0082] Third Embodiment. Air conditioning apparatus 100 according to a third embodiment is identical to air conditioning apparatus 100 according to the first embodiment in terms of configuration, operations, and functions and effects, unless otherwise described.

[0083] A configuration of air conditioning apparatus 100 according to the third embodiment will be described with reference to Fig. 8. As shown in Fig. 8, air conditioning apparatus 100 according to the third embodiment has an outdoor machine 40, instead of cooling tower 63.

[0084] Outdoor unit 60 has outdoor machine 40 disposed in the outdoor unit. Outdoor machine 40 has a second compressor 41, a second four-way valve 48, a second expansion valve 42, a third heat exchanger 43, and a fourth heat exchanger 44 that are disposed in outdoor machine 40. In addition, outdoor machine 40 has an outdoor blower 45 disposed in outdoor machine 40.

[0085] Second compressor 41, second four-way valve 48, third heat exchanger 43, second expansion valve 42, and fourth heat exchanger 44 are connected together to form a second refrigerant pipe path R2 that allows refrigerant to flow.

[0086] Outdoor machine 40 and branch unit 10 are connected to each other through supply main pipe 61 and return main pipe 62.

[0087] Second four-way valve 48 is configured to be switched to cause the refrigerant to flow in order of second compressor 41, second four-way valve 48, third heat exchanger 43, second expansion valve 42, fourth heat exchanger 44, and second fourway valve 48, or to cause the refrigerant to flow in order of second compressor 41, second four-way valve 48, fourth heat exchanger 44, second expansion valve 42, third heat exchanger 43, and second four-way valve 48.

[0088] The one end of supply main pipe 61 is connected to one end of third heat exchanger 43. The other end of supply main pipe 61 is connected between second heat exchanger 22 and second branch header 23 in second pipe path P2. The one end of return main pipe 62 is connected to another end of third heat exchanger 43. The other end of return main pipe 62 is connected between second heat exchanger 22 and second branch header 23 in second pipe path P2.

[0089] A suction volume of second compressor 41 in outdoor machine 40 is larger than a suction volume of first compressor 31 in branch unit 10. <Operation of Air Conditioning Apparatus> Air conditioning apparatus 100 performs the cooling-only operation, the cooling-dominated operation, the heating-only operation, or the heating-dominated operation, depending on the operation modes of the plurality of indoor units 50a, 50b and 50c. In air conditioning apparatus 100 according to the third embodiment, since fourth heat exchanger 44 exposed to the outdoor air is connected to third heat exchanger 43 through a refrigerant pipe, extraction of heat from the outdoor air cannot be performed in fourth heat exchanger 44 in a stop state of second compressor 41. Therefore, air conditioning apparatus 100 according to the third embodiment does not perform the low-outdoor-air cooling operation.

[0090] Referring to Figs. 9 to 12, in air conditioning apparatus 100 according to the third embodiment, outdoor machine 40 mainly generates hot heat and branch unit 10 generates the air conditioning capacity corresponding to the heating capacity at the time of the cooling-dominated operation and the cooling capacity at the time of the heating-dominated operation.

[0091] As shown in Fig. 9, when indoor units 50a, 50b and 50c in operation are all in the cooling operation mode, air conditioning apparatus 100 performs the cooling-only operation.

[0092] As shown in Fig. 10, when the cooling operation mode and the heating operation mode coexist in indoor units 50a, 50b and 50c in operation and a total of air conditioning loads of the indoor units in the cooling operation mode is larger than a total of air conditioning loads of the indoor units in the heating operation mode, air conditioning apparatus 100 performs the cooling-dominated operation.

[0093] As shown in Fig. 11, when indoor units 50a, 50b and 50c in operation are all in the heating operation mode, air conditioning apparatus 100 performs the heating-only operation.

[0094] As shown in Fig. 12, when the cooling operation mode and the heating operation mode coexist in indoor units 50a, 50b and 50c in operation and the total of the air conditioning loads of the indoor units in the heating operation mode is larger than the total of the air conditioning loads of the indoor units in the cooling operation mode, air conditioning apparatus 100 performs the heating-dominated operation.

[0095] Next, functions and effects of air conditioning apparatus 100 according to the third embodiment will be described. In air conditioning apparatus 100 according to the first embodiment having cooling tower 63 and air conditioning apparatus 100 according to the second embodiment having underground heat exchanger 70, all of the cooling and heating capacities of the plurality of indoor units 50a, 50b and 50c need to be generated in the refrigeration cycle in branch unit 10 in the cooling-only operation, the cooling-dominated operation, the heating-only operation, and the heating-dominated operation of air conditioning apparatus 100.

[0096] In air conditioning apparatus 100 according to the third embodiment, outdoor unit 60 has outdoor machine 40. Therefore, the cooling capacity at the time of the cooling-only operation and the heating capacity at the time of the heating-only operation of air conditioning apparatus 100 can be generated in the refrigeration cycle in outdoor machine 40. Therefore, the refrigeration cycle in branch unit 10 can be reduced in size.

[0097] Since the refrigeration cycle in branch unit 10 is reduced in size, a placement space of the refrigeration cycle, a base and the cost required for branch unit 10 can be reduced, and vibration and noise mainly caused by first compressor 31 can be reduced. In addition, the amount of fdled refrigerant enclosed in branch unit 10 can also be reduced.

[0098] In air conditioning apparatus 100 according to the third embodiment, the suction volume of second compressor 41 in outdoor machine 40 is larger than the suction volume of first compressor 31 in branch unit 10. Therefore, a placement space of the refrigeration cycle, a base and the cost in branch unit 10 can be reduced, and vibration and noise caused by first compressor 31 can be reduced. In addition, the amount of filled refrigerant enclosed in branch unit 10 can also be reduced.

[0099] Fourth Embodiment. Air conditioning apparatus 100 according to a fourth embodiment is identical to air conditioning apparatus 100 according to the third embodiment in terms of configuration, operations, and functions and effects, unless otherwise described.

[0100] A defrosting operation of air conditioning apparatus 100 according to the fourth embodiment will be described with reference to Fig. 13. As shown in Fig. 13, in air conditioning apparatus 100 according to the fourth embodiment, the defrosting operation is performed when frost forms on fourth heat exchanger 44 and defrosting is required in the heating-only operation or the heating-dominated operation.

[0101] In air conditioning apparatus 100 according to the fourth embodiment, the defrosting operation for removing frost adhering to fourth heat exchanger 44 in outdoor machine 40 is performed. In the defrosting operation, the refrigerant flows through second refrigerant pipe path R2 and first refrigerant pipe path RI as described below.

[0102] In second refrigerant pipe path R2, the refrigerant flows from second compressor 41 through second four-way valve 48, fourth heat exchanger 44, second expansion valve 42, third heat exchanger 43, and second four-way valve 48 to again reach second compressor 41 in outdoor machine 40. That is, the refrigeration cycle in outdoor machine 40 forms a refrigerant circuit in which the refrigerant flows from second compressor 41 through second four-way valve 48, fourth heat exchanger 44, second expansion valve 42, third heat exchanger 43, and second four-way valve 48 to second compressor 41.

[0103] In first refrigerant pipe path RI, the refrigerant flows from first compressor 31, first four-way valve 18, second heat exchanger 22, first expansion valve 32, first heat exchanger 12, and first four-way valve 18 to again reach first compressor 31 in branch unit 10. That is, the refrigeration cycle in branch unit 10 forms a refrigerant circuit in which the refrigerant flows from first compressor 31 through first four-way valve 18, second heat exchanger 22, first expansion valve 32, first heat exchanger 12, and first four-way valve 18 to first compressor 31.

[0104] Next, functions and effects of air conditioning apparatus 100 according to the fourth embodiment will be described. In air conditioning apparatus 100 according to the fourth embodiment, the defrosting operation for removing frost adhering to fourth heat exchanger 44 in outdoor machine 40 is performed. Therefore, when frost forms on fourth heat exchanger 44 and defrosting is required in the heating-only operation or the heating-dominated operation, continuation of the heating operation of the indoor units and supply of an amount of defrosting heat to fourth heat exchanger 44 can be achieved.

[0105] Fifth Embodiment. Air conditioning apparatus 100 according to a fifth embodiment is identical to air conditioning apparatus 100 according to the third embodiment in terms of configuration, operations, and functions and effects, unless otherwise described.

[0106] A configuration of air conditioning apparatus 100 according to the fifth embodiment will be described with reference to Fig. 14. As shown in Fig. 14, in air conditioning apparatus 100 according to the fifth embodiment, branch unit 10 has a supply main pipe on-off valve 34 and a return main pipe on-off valve 35.

[0107] Supply main pipe on-off valve 34 is disposed at a connection portion between second pipe path P2 and supply main pipe 61 in branch unit 10. Supply main pipe on-off valve 34 is configured to be capable of opening and closing second pipe path P2 and supply main pipe 61. Return main pipe on-off valve 35 is disposed at a connection portion between second pipe path P2 and return main pipe 62 in branch unit 10. Return main pipe on-off valve 35 is configured to be capable of opening and closing second pipe path P2 and return main pipe 62.

[0108] Next, functions and effects of air conditioning apparatus 100 according to the fifth embodiment will be described. In air conditioning apparatus 100 according to the fifth embodiment, supply main pipe on-off valve 34 is disposed at the connection portion between second pipe path P2 and supply main pipe 61 in branch unit 10. Return main pipe on-off valve 35 is disposed at the connection portion between second pipe path P2 and return main pipe 62 in branch unit 10. Therefore, by closing supply main pipe on-off valve 34 and return main pipe on-off valve 35, second pipe path P2 in which the heat medium is circulated by second pump 21 can be formed by branch unit 10 and the plurality of indoor units 50a, 50b and 50c.

[0109] When branch unit 10 and outdoor machine 40 cannot be installed at the same time, or when there is a risk of water leakage in supply main pipe 61 and return main pipe 62 that connect branch unit 10 and outdoor machine 40 to each other, a test run about water leakage and water circulation can be performed with only branch unit 10 and the plurality of indoor units 50a, 50b and 50c.

[0110] Sixth Embodiment. Air conditioning apparatus 100 according to a sixth embodiment is identical to air conditioning apparatus 100 according to the first embodiment in terms of configuration, operations, and functions and effects, unless otherwise described.

[0111] Configurations of supply branch pipes 51, return branch pipes 52, supply main pipe 61, and return main pipe 62 of air conditioning apparatus 100 according to the sixth embodiment will be described with reference to Fig. 15. As shown in Fig. 15, an inner diameter of each of supply main pipe 61 and return main pipe 62 is larger than an inner diameter of each of the plurality of supply branch pipes 51 and an inner diameter of each of the plurality of return branch pipes 52. That is, a minimum value of the inner diameters of supply main pipe 61 and return main pipe 62 is larger than a maximum value of the inner diameters of all of supply branch pipes 51 and the inner diameters of all of return branch pipes 52.

[0112] Next, functions and effects of air conditioning apparatus 100 according to the sixth embodiment will be described. In air conditioning apparatus 100 according to the sixth embodiment, the inner diameter of each of supply main pipe 61 and return main pipe 62 is larger than the inner diameter of each of the plurality of supply branch pipes 51 and the inner diameter of each of the plurality of return branch pipes 52.

[0113] During the cooling-only operation in which the plurality of indoor units 50a, 50b and 50c are all in the cooling operation mode, or during the heating-only operation in which the plurality of indoor units 50a, 50b and 50c are in the heating operation mode, a maximum flow rate of the heat medium (water or antifreeze) flows through supply main pipe 61 and return main pipe 62.

[0114] Since the inner diameter of each of supply main pipe 61 and return main pipe 62 is larger than the inner diameter of each of the plurality of supply branch pipes 51 and the inner diameter of each of the plurality of return branch pipes 52, a flow resistance in each of supply main pipe 61 and return main pipe 62 can be suppressed.

[0115] In addition, by not designing an internal volume of each of supply branch pipes 51 and return branch pipes 52 excessively, a total volume value of the heat medium (water or antifreeze) retained in air conditioning apparatus 100 can be designed to be small. Therefore, a time period required until the air conditioning capacity is demonstrated at the start of the cooling and heating operations can be shortened. Thus, the air conditioning control followability can be improved.

[0116] Seventh Embodiment. Air conditioning apparatus 100 according to a seventh embodiment is identical to air conditioning apparatus 100 according to the first embodiment in terms of configuration, operations, and functions and effects, unless otherwise described.

[0117] In air conditioning apparatus 100 according to the seventh embodiment, a fluid smaller in influence on global warming per unit mass than carbon dioxide is enclosed as the heat medium flowing through first pipe path Pl and second pipe path P2. A global warming potential per unit mass of the heat medium is smaller than that of carbon dioxide.

[0118] In air conditioning apparatus 100 according to the seventh embodiment, the global warming potential per unit mass of the heat medium is smaller than that of carbon dioxide. Therefore, the influence on global warming at the time of leakage of the heat medium can be reduced.

[0119] The embodiments described above can be combined as appropriate. It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present disclosure is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. REFERENCE SIGNS LIST

[0120] 10 branch unit; 11 first pump; 12 first heat exchanger; 13 first branch header; 14a, 14b, 14c first supply branch pipe on-off valve; 15a, 15b, 15c first return branch pipe on-off valve; 16 first confluence header; 17 first bypass valve; 18 first four-way valve; 21 second pump; 22 second heat exchanger; 23 second branch header; 24a, 24b, 24c second supply branch pipe on-off valve; 25a, 25b, 25c second return branch pipe on-off valve; 26 second confluence header; 27 second bypass valve; 31 first compressor; 32 first expansion valve; 33 flow rate adjustment valve; 34 supply main pipe on-off valve; 35 return main pipe on-off valve; 40 outdoor machine; 41 second compressor; 42 second expansion valve; 43 third heat exchanger; 44 fourth heat exchanger; 45 outdoor blower; 48 second four-way valve; 50a, 50b, 50c indoor unit; 51a, 51b, 51c supply branch pipe; 52a, 52b, 52c return branch pipe; 53a, 53b, 53c indoor heat exchanger; 54a, 54b, 54c indoor blower; 60 outdoor unit; 61 supply main pipe; 62 return main pipe; 63 cooling tower; 64 blower; 70 underground heat exchanger; 100 air conditioning apparatus; Pl first pipe path; P2 second pipe path; RI first refrigerant pipe path; R2 second refrigerant pipe path.

Claims

1. An air conditioning apparatus comprising:a branch unit;a plurality of indoor units;an outdoor unit;a plurality of supply branch pipes and a plurality of return branch pipes that connect the branch unit to respective ones of the plurality of indoor units; anda supply main pipe and a return main pipe that connect the branch unit and the outdoor unit to each other, whereinthe branch unit comprises a first branch header, a second branch header, a first confluence header, a second confluence header, a plurality of first supply branch pipe on-off valves, a plurality of second supply branch pipe on-off valves, a plurality of first return branch pipe on-off valves, a plurality of second return branch pipe on-off valves, a first bypass valve, a second bypass valve, a first pump, a second pump, a first heat exchanger, a second heat exchanger, a first compressor, a first expansion valve, and a first four-way valve that are disposed in the branch unit,the plurality of indoor units comprise a plurality of indoor heat exchangers disposed in the plurality of indoor units, respectively,one end of each of the plurality of supply branch pipes is connected to the first branch header through a corresponding one of the plurality of first supply branch pipe on-off valves, and connected to the second branch header through a corresponding one of the plurality of second supply branch pipe on-off valves,another end of each of the plurality of supply branch pipes is connected to one end of a corresponding one of the plurality of indoor heat exchangers,one end of each of the plurality of return branch pipes is connected to the first confluence header through a corresponding one of the plurality of first return branch pipe on-off valves, and connected to the second confluence header through a corresponding one of the plurality of second return branch pipe on-off valves,another end of each of the plurality of return branch pipes is connected to another end of a corresponding one of the plurality of indoor heat exchangers,the first branch header and the first confluence header are connected to each other through the first bypass valve,the second branch header and the second confluence header are connected to each other through the second bypass valve,the first confluence header, the first pump, the first heat exchanger, and the first branch header are connected together to form a first pipe path that allows a heat medium to flow in order of the first confluence header, the first pump, the first heat exchanger, and the first branch header,the second confluence header, the second pump, the second heat exchanger, and the second branch header are connected together to form a second pipe path that allows the heat medium to flow in order of the second confluence header, the second pump, the second heat exchanger, and the second branch header,the first compressor, the first four-way valve, the first heat exchanger, the first expansion valve, and the second heat exchanger are connected together to form a first refrigerant pipe path that allows refrigerant to flow,the first four-way valve is configured to be switched to cause the refrigerant to flow in order of the first compressor, the first four-way valve, the first heat exchanger, the first expansion valve, the second heat exchanger, and the first four-way valve, or to cause the refrigerant to flow in order of the first compressor, the first four-way valve, the second heat exchanger, the first expansion valve, the first heat exchanger, and the first four-way valve,one end of the supply main pipe is connected to one end of the outdoor unit, another end of the supply main pipe is connected to the second pipe path, one end of the return main pipe is connected to another end of the outdoor unit, another end of the return main pipe is connected to the second pipe path,in the first heat exchanger, heat is exchanged between the refrigerant flowing in the first refrigerant pipe path and the heat medium flowing in the first pipe path, andin the second heat exchanger, heat is exchanged between the refrigerant flowing in the first refrigerant pipe path and the heat medium flowing in the second pipe path.

2. The air conditioning apparatus according to claim 1, whereinthe branch unit comprises a flow rate adjustment valve disposed in the branch unit and disposed in the second pipe path, andthe flow rate adjustment valve is connected between a point of branch from the supply main pipe and a point of confluence with the return main pipe in the second pipe path.

3. The air conditioning apparatus according to claim 1 or 2, wherein the outdoor unit comprises a cooling tower disposed in the outdoor unit, the cooling tower and the branch unit are connected to each other through the supply main pipe and the return main pipe,the one end of the supply main pipe is connected to one end of the cooling tower,the other end of the supply main pipe is connected between the second pump and the second heat exchanger in the second pipe path,the one end of the return main pipe is connected to another end of the cooling tower, andthe other end of the return main pipe is connected between the second pump and the second heat exchanger in the second pipe path.

4. The air conditioning apparatus according to claim 1 or 2, wherein the outdoor unit comprises an underground heat exchanger disposed in the outdoor unit,the underground heat exchanger and the branch unit are connected to each other through the supply main pipe and the return main pipe,the one end of the supply main pipe is connected to one end of the undergroundheat exchanger,the other end of the supply main pipe is connected between the second pump and the second heat exchanger in the second pipe path,the one end of the return main pipe is connected to another end of the underground heat exchanger, andthe other end of the return main pipe is connected between the second pump and the second heat exchanger in the second pipe path.

5. The air conditioning apparatus according to claim 1 or 2, wherein the outdoor unit comprises an outdoor machine disposed in the outdoor unit, the outdoor machine comprises a second compressor, a second four-way valve, a second expansion valve, a third heat exchanger, and a fourth heat exchanger that are disposed in the outdoor machine,the second compressor, the second four-way valve, the third heat exchanger, the second expansion valve, and the fourth heat exchanger are connected together to form a second refrigerant pipe path that allows refrigerant to flow,the outdoor machine and the branch unit are connected to each other through the supply main pipe and the return main pipe,the second four-way valve is configured to be switched to cause the refrigerant to flow in order of the second compressor, the second four-way valve, the third heat exchanger, the second expansion valve, the fourth heat exchanger, and the second fourway valve, or to cause the refrigerant to flow in order of the second compressor, the second four-way valve, the fourth heat exchanger, the second expansion valve, the third heat exchanger, and the second four-way valve,the one end of the supply main pipe is connected to one end of the third heat exchanger,the other end of the supply main pipe is connected between the second heat exchanger and the second branch header in the second pipe path,the one end of the return main pipe is connected to another end of the third heatexchanger, andthe other end of the return main pipe is connected between the second heat exchanger and the second branch header in the second pipe path.

6. The air conditioning apparatus according to claim 5, wherein a suction volume of the second compressor in the outdoor machine is larger than a suction volume of the first compressor in the branch unit.

7. The air conditioning apparatus according to claim 5 or 6, whereina defrosting operation for removing frost adhering to the fourth heat exchanger in the outdoor machine is performed, andduring the defrosting operation,in the second refrigerant pipe path, the refrigerant flows from the second compressor through the second four-way valve, the fourth heat exchanger, the second expansion valve, the third heat exchanger, and the second four-way valve to again reach the second compressor in the outdoor machine, andin the first refrigerant pipe path, the refrigerant flows from the first compressor through the first four-way valve, the second heat exchanger, the first expansion valve, the first heat exchanger, and the first four-way valve to again reach the first compressor in the branch unit.

8. The air conditioning apparatus according to any one of claims 1 to 7, whereina capacity of the second pump is larger than a capacity of the first pump.

9. The air conditioning apparatus according to any one of claims 1 to 8, whereinthe branch unit comprises a supply main pipe on-off valve and a return main pipe on-off valve,the supply main pipe on-off valve is disposed at a connection portion betweenthe second pipe path and the supply main pipe in the branch unit, andthe return main pipe on-off valve is disposed at a connection portion between the second pipe path and the return main pipe in the branch unit.5

10. The air conditioning apparatus according to any one of claims 1 to9, whereinan inner diameter of each of the supply main pipe and the return main pipe is larger than an inner diameter of each of the plurality of supply branch pipes and an10 inner diameter of each of the plurality of return branch pipes.

11. The air conditioning apparatus according to any one of claims 1 to10, whereina global warming potential per unit mass of the heat medium is smaller than that15 of carbon dioxide.

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