Air-conditioning device

Abstract

An air-conditioning device (100) comprises: an outdoor unit (40); a plurality of indoor units (50); a relay machine (10); a refrigerant circuit in which a refrigerant circulates; and a heat medium circuit in which a heat medium having a global warming potential (GWP) lower than that of the refrigerant circulates. The heat medium circuit has: a first pump (11), a second pump (21), a first heat exchanger (12), a second heat exchanger (22), a first branch header (13), a second branch header (23), a first merging header (16), a second merging header (26), a plurality of first opening / closing valves (14), a plurality of second opening / closing valves (24), a plurality of third opening / closing valves (15), a plurality of fourth opening / closing valves (25), a fifth opening / closing valve (17), a sixth opening / closing valve (27), a seventh opening / closing valve (33), an eighth opening / closing valve (34), a ninth opening / closing valve (35), and a tenth opening / closing valve (36), which are arranged in the relay machine; an outbound main pipe (41) and a return main pipe (42) that connect the relay machine and the outdoor unit; and a plurality of outbound branch pipes (51) and a plurality of return branch pipes (52) that connect the relay machine to each of the indoor units.

Description

air conditioning equipment

[0001] The present disclosure relates to an air conditioning apparatus, and more particularly to an air conditioning apparatus including an outdoor unit, a plurality of indoor units, and a relay unit.

[0002] BACKGROUND ART Conventionally, air conditioners have been known that include an outdoor unit, a plurality of indoor units, and a relay unit, and in which the outdoor unit and the plurality of indoor units are connected via the relay unit.

[0003] International Publication No. 2009 / 133640 discloses an air conditioning apparatus as described above, in which the outdoor unit and the relay unit are connected via first and second extension pipes, and the relay unit and the indoor unit are connected via third and fourth extension pipes. The air conditioning apparatus includes an intermediate heat exchanger disposed within the relay unit.

[0004] In the air conditioner, heat is transferred between the outdoor unit and the relay unit by circulating a refrigerant through the first and second extension pipes, and between the relay unit and the indoor unit by circulating water or antifreeze through the third and fourth extension pipes. The intermediate heat exchanger provided in the relay unit exchanges heat between the refrigerant and the water or antifreeze, transferring heat from the indoor unit to the outdoor unit via the intermediate heat exchanger in the relay unit during cooling operation, and transferring heat from the outdoor unit to the indoor unit via the intermediate heat exchanger in the relay unit during heating operation.

[0005] In the air conditioner described above, two pipes can be used to connect both the outdoor unit and the relay unit, and the relay unit and the indoor unit, thereby reducing the cost of piping materials and the number of construction steps.

[0006] WO 2009 / 133640

[0007] However, the above-mentioned air conditioner has a problem in that the refrigerant charge amount in the air conditioner increases when the first and second extension pipes between the outdoor unit and the relay unit are installed over a long distance (e.g., 110 meters). Because the global warming potential (GWP) of refrigerants is higher than that of heat transfer media such as water and antifreeze, the greater the refrigerant charge amount, the greater the air conditioner's impact on global warming. Furthermore, refrigerants have the problem of being more expensive and having a higher risk of combustion in the event of a leak, compared to heat transfer media such as water and antifreeze. Therefore, the market and society demand air conditioners with a smaller total refrigerant charge amount.

[0008] A primary object of the present invention is to provide an air conditioner that can reduce the amount of refrigerant charged compared to the above-mentioned conventional air conditioners.

[0009] An air conditioning apparatus according to the present disclosure includes an outdoor unit, a plurality of indoor units, a relay unit, a refrigerant circuit through which a refrigerant circulates, and a heat medium circuit through which a heat medium having a lower global warming potential (GWP) than the refrigerant circulates. The refrigerant circuit is disposed within the relay unit and includes a compressor, a first heat exchanger, an expansion valve, and a second heat exchanger, and is configured so that the refrigerant circulates through the compressor, the first heat exchanger, the expansion valve, and the second heat exchanger in that order. The heat medium circuit includes a first pump, a second pump, a first heat exchanger, a second heat exchanger, a first branch header, a second branch header, a first merging header, a second merging header, a plurality of first on-off valves, a plurality of second on-off valves, a plurality of third on-off valves, a plurality of fourth on-off valves, a fifth on-off valve, a sixth on-off valve, a seventh on-off valve, an eighth on-off valve, a ninth on-off valve, and a tenth on-off valve, all of which are arranged in the relay unit; an outdoor heat exchanger arranged in the outdoor unit; indoor heat exchangers arranged in each of the indoor units; a main outgoing pipe and a main ingoing pipe connecting the relay unit to the outdoor unit; and a plurality of outgoing branch pipes and a plurality of ingoing branch pipes connecting the relay unit to each of the indoor units. One end of each of the outgoing branch pipes is connected to the first branch header via a respective one of the first on-off valves and to the second branch header via a respective one of the second on-off valves. The other end of each of the outgoing branch pipes is connected to one end of the indoor heat exchanger of each of the indoor units. One end of each of the multiple return branch pipes is connected to the first merging header via a respective one of multiple third on-off valves and to the second merging header via a respective one of multiple fourth on-off valves. The other end of each of the multiple return branch pipes is connected to the other end of each of the indoor heat exchangers of the multiple indoor units. The first branch header and the first merging header are connected via a fifth on-off valve. The second branch header and the second merging header are connected via a sixth on-off valve. Within the relay unit, the first merging header, the first pump, the first heat exchanger, and the first branch header are connected in this order. Within the relay unit, the second merging header, the second pump, the second heat exchanger, and the second branch header are connected in this order. One end of the outward main pipe is connected to the first merging header via a seventh on-off valve and to the second merging header via an eighth on-off valve. The other end of the outward main pipe is connected to one end of the outdoor heat exchanger of the outdoor unit. One end of the return main pipe is connected to the first pump via a ninth on-off valve, and is connected to the second pump via a tenth on-off valve.The other end of the return main pipe is connected to the other end of the outdoor heat exchanger of the outdoor unit.

[0010] According to the present invention, it is possible to provide an air conditioner that can reduce the amount of refrigerant charged compared to the conventional air conditioner described above.

[0011] FIG. 1 is a diagram showing an air conditioning apparatus according to embodiment 1. FIG. 1 is a diagram showing a refrigerant circuit and a heat medium circuit when the air conditioning apparatus shown in FIG. 1 is in a full cooling operation state. FIG. 2 is a diagram showing a refrigerant circuit and a heat medium circuit when the air conditioning apparatus shown in FIG. 1 is in a cooling-dominated operation state. FIG. 3 is a diagram showing a refrigerant circuit and a heat medium circuit when the air conditioning apparatus shown in FIG. 1 is in a full heating operation state. FIG. 4 is a diagram showing a refrigerant circuit and a heat medium circuit when the air conditioning apparatus shown in FIG. 1 is in a heating-dominated operation state. FIG. 5 is a diagram showing a refrigerant circuit and a heat medium circuit when the air conditioning apparatus shown in FIG. 1 is in a low outdoor air cooling operation state. FIG. 6 is a diagram showing an air conditioning apparatus according to embodiment 2. FIG. 7 is a diagram showing an air conditioning apparatus according to embodiment 3. FIG. 8 is a diagram showing an air conditioning apparatus according to embodiment 4.

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, identical or corresponding parts are designated by the same reference numerals, and descriptions thereof will not be repeated. Furthermore, the vertical and horizontal positional relationships of each component in each drawing do not limit the physical positional relationships of each component.

[0013] Embodiment 1. <Configuration of Air Conditioning Apparatus> As shown in Fig. 1, an air conditioning apparatus 100 according to Embodiment 1 comprises a relay unit 10, an outdoor unit 40, and multiple indoor units 50a, 50b, and 50c. The air conditioning apparatus 100 shown in Fig. 1 comprises three indoor units 50a, 50b, and 50c, but the number of indoor units may be any number equal to or greater than two.

[0014] The relay unit 10 includes a refrigerant circuit through which a refrigerant circulates. The relay unit 10, the outdoor unit 40, and the multiple indoor units 50a, 50b, and 50c include a heat medium circuit through which a heat medium with a lower global warming potential (GWP) than the refrigerant circulates. The heat medium with a lower global warming potential (GWP) than the refrigerant is, for example, water or antifreeze. The refrigerant circuit is included only in the relay unit 10. The outdoor unit 40 and the multiple indoor units 50a, 50b, and 50c do not include a refrigerant circuit.

[0015] The refrigerant circuit has a compressor 31, a first heat exchanger 12, an expansion valve, and a second heat exchanger 22. The compressor 31, the first heat exchanger 12, the expansion valve, and the second heat exchanger 22 are disposed inside the relay unit 10. The refrigerant circuit is configured so that the refrigerant circulates sequentially through the compressor 31, the first heat exchanger 12, the expansion valve, and the second heat exchanger 22. The refrigerant circulating through the refrigerant circuit condenses in the first heat exchanger 12 by exchanging heat with the heat medium circulating through the heat medium circuit, and evaporates in the second heat exchanger 22 by exchanging heat with the heat medium circulating through the heat medium circuit.

[0016] Within the relay unit 10, the heat medium circuit has a first pump 11, a first heat exchanger 12, a first branch header 13, a first merging header 16, a second pump 21, a second heat exchanger 22, a second branch header 23, a second merging header 26, a plurality of first on-off valves 14a, 14b, 14c, a plurality of second on-off valves 24a, 24b, 24c, a plurality of third on-off valves 15a, 15b, 15c, a plurality of fourth on-off valves 25a, 25b, 25c, a fifth on-off valve 17, a sixth on-off valve 27, a seventh on-off valve 33, an eighth on-off valve 34, a ninth on-off valve 35, and a tenth on-off valve 36.

[0017] The heat medium circuit has an outdoor heat exchanger 43 in the outdoor unit 40. The heat medium circuit has indoor heat exchangers 53a, 53b, 53c in each of the indoor units 50a, 50b, 50c.

[0018] The heat medium circuit further includes an outward main pipe 41 and a return main pipe 42 that connect the relay unit 10 and the outdoor unit 40, and a plurality of outward branch pipes 51a, 51b, 51c and a plurality of return branch pipes 52a, 52b, 52c that connect the relay unit 10 and each of the plurality of indoor units 50a, 50b, 50c.

[0019] Within the relay unit 10, the first junction header 16, the first pump 11, the first heat exchanger 12, and the first branch header 13 are connected in series via piping in the order listed. The first junction header 16, the first pump 11, the first heat exchanger 12, and the first branch header 13, as well as the multiple piping connecting them in series, form a first piping path.

[0020] Within the relay unit 10, the second junction header 26, the second pump 21, the second heat exchanger 22, and the second branch header 23 are connected in series via piping in this order. The second junction header 26, the second pump 21, the second heat exchanger 22, the second branch header 23, and the multiple piping connecting them in series constitute a second piping path.

[0021] Each of the first piping path and the second piping path is connected to the outdoor heat exchanger 43 via the outward main piping 41 and the return main piping 42, and is also connected to each of the indoor heat exchangers 53a, 53b, and 53c via a plurality of outward branch pipings 51a, 51b, and 51c and a plurality of return branch pipings 52a, 52b, and 52c. The outdoor heat exchanger 43 and each of the indoor heat exchangers 53a, 53b, and 53c are connected in parallel to each other with respect to the first piping path, and are also connected in parallel to each other with respect to the second piping path.

[0022] Within the relay unit 10, the heat medium circuit further has a plurality of third piping paths connecting the first branch header 13 of the first piping path and each of the plurality of outward branch pipes 51 a, 51 b, 51 c, a plurality of fourth piping paths connecting the second branch header 23 of the second piping path and each of the plurality of outward branch pipes 51 a, 51 b, 51 c, a plurality of fifth piping paths connecting the first junction header 16 of the first piping path and each of the plurality of return branch pipes 52 a, 52 b, 52 c, and a plurality of sixth piping paths connecting the second junction header 26 of the second piping path and each of the plurality of return branch pipes 52 a, 52 b, 52 c.

[0023] Each of the plurality of first on-off valves 14a, 14b, and 14c opens and closes the third piping path. Each of the plurality of second on-off valves 24a, 24b, and 24c opens and closes the fourth piping path. Each of the plurality of third on-off valves 15a, 15b, and 15c opens and closes the fifth piping path. Each of the plurality of fourth on-off valves 25a, 25b, and 25c opens and closes the sixth piping path.

[0024] In other words, one end of each of the plurality of outward branch pipes 51 a, 51 b, 51 c is connected to the first branch header 13 via each of the plurality of first on-off valves 14 a, 14 b, 14 c, and is connected to the second branch header 23 via each of the plurality of second on-off valves 24 a, 24 b, 24 c. The other end of each of the plurality of outward branch pipes 51 a, 51 b, 51 c is connected to one end of each of the indoor heat exchangers 53 a, 53 b, 53 c of the plurality of indoor units 50 a, 50 b, 50 c. One end of each of the plurality of return branch pipes 52 a, 52 b, 52 c is connected to the first merging header 16 via each of the plurality of third on-off valves 15 a, 15 b, 15 c, and is connected to the second merging header 26 via each of the plurality of fourth on-off valves 25 a, 25 b, 25 c. The other ends of the plurality of return branch pipes 52a, 52b, 52c are connected to the other ends of the indoor heat exchangers 53a, 53b, 53c of the plurality of indoor units 50a, 50b, 50c, respectively.

[0025] A set of third and fourth piping paths connected to one outward branch pipe 51 may have, for example, a common portion and a non-common portion branching off from the common portion. A set of fifth and sixth piping paths connected to one return branch pipe 52 may have, for example, a common portion and a non-common portion branching off from the common portion. In this case, each of the first on-off valves 14a, 14b, and 14c opens and closes the non-common portion of each third piping path, and each of the second on-off valves 24a, 24b, and 24c opens and closes the non-common portion of each fourth piping path. Each of the third on-off valves 15a, 15b, and 15c opens and closes the non-common portion of each fifth piping path, and each of the fourth on-off valves 25a, 25b, and 25c opens and closes the non-common portion of each sixth piping path.

[0026] The heat medium circuit further includes, within the relay unit 10, a first bypass path connecting the first branch header 13 of the first piping path and the first merging header 16, and a second bypass path connecting the second branch header 23 of the second piping path and the second merging header 26. The first bypass path connects the first branch header 13 and the first merging header 16, bypassing the plurality of outward branch pipes 51a, 51b, 51c, the plurality of indoor heat exchangers 53a, 53b, 53c, and the plurality of return branch pipes 52a, 52b, 52c. The second bypass path connects the second branch header 23 and the second merging header 26, bypassing the plurality of outward branch pipes 51a, 51b, 51c, the plurality of indoor heat exchangers 53a, 53b, 53c, and the plurality of return branch pipes 52a, 52b, 52c.

[0027] The fifth on-off valve 17 opens and closes the first bypass path. The sixth on-off valve 27 opens and closes the second bypass path. In other words, the first branch header 13 and the first merging header 16 are connected via the fifth on-off valve 17. The second branch header 23 and the second merging header 26 are connected via the sixth on-off valve 27.

[0028] Within the relay unit 10, the heat medium circuit further has a seventh piping path connecting the first junction header 16 of the first piping path and the outward main piping 41, an eighth piping path connecting the second junction header 26 of the second piping path and the outward main piping 41, a ninth piping path connecting the return main piping 42 and the first pump 11 of the first piping path, and a tenth piping path connecting the return main piping 42 and the second pump 21 of the second piping path.

[0029] The seventh on-off valve 33 opens and closes the seventh piping path. The eighth on-off valve 34 opens and closes the eighth piping path. The ninth on-off valve 35 opens and closes the ninth piping path. The tenth on-off valve 36 opens and closes the tenth piping path.

[0030] The seventh piping path is connected to a portion of the first junction header 16 that is located downstream of each connection point between the first junction header 16 and the plurality of fifth piping paths as viewed from the first pump 11. The eighth piping path is connected to a portion of the second junction header 26 that is located downstream of each connection point between the second junction header 26 and the plurality of sixth piping paths as viewed from the second pump 21.

[0031] The seventh and eighth piping paths have, for example, a common portion and a non-common portion branching off from the common portion. The ninth and tenth piping paths have, for example, a common portion and a non-common portion branching off from the common portion. In this case, the seventh on-off valve 33 opens and closes the non-common portion of the seventh piping path, and the eighth on-off valve 34 opens and closes the non-common portion of each of the eighth piping paths. The ninth on-off valve 35 opens and closes the non-common portion of the ninth piping path, and the tenth on-off valve 36 opens and closes the non-common portion of the tenth piping path.

[0032] In other words, one end of the outgoing main pipe 41 is connected to the first junction header 16 of the first piping path via the seventh on-off valve 33, and is connected to the second junction header 26 of the second piping path via the eighth on-off valve. The other end of the outgoing main pipe 41 is connected to one end of the outdoor heat exchanger 43 of the outdoor unit 40.

[0033] One end of the return main pipe 42 is connected to the first pump 11 of the first piping path via the ninth on-off valve 35, and is connected to the second pump 21 of the second piping path via the tenth on-off valve 36. The other end of the return main pipe 42 is connected to the other end of the outdoor heat exchanger 43 of the outdoor unit 40.

[0034] Within the relay unit 10, the heat medium circuit further has a third bypass path connecting the seventh piping path and the ninth piping path, a fourth bypass path connecting the eighth piping path and the tenth piping path, an eleventh on-off valve 18 that opens and closes the third bypass path, and a twelfth on-off valve 28 that opens and closes the fourth bypass path.

[0035] From a different perspective, the first piping path has a pipe 19 that connects the first junction header 16 and the first pump 11. A seventh piping path that connects the first junction header 16 and the outbound main pipe 41 and a ninth piping path that connects the return main pipe 42 and the first pump 11 of the first piping path are each connected to the pipe 19. A connection point C between the pipe 19 and the ninth piping path is located downstream from a connection point A between the pipe 19 and the seventh piping path as viewed from the first pump 11. The eleventh on-off valve 18 opens and closes the pipe 19.

[0036] The second piping path has a pipe 29 connecting the second junction header 26 and the second pump 21. An eighth piping path connecting the second junction header 26 and the outward main pipe 41 and a tenth piping path connecting the return main pipe 42 and the second pump 21 of the second piping path are each connected to the pipe 29. A connection point D between the pipe 29 and the tenth piping path is located downstream from a connection point B between the pipe 29 and the eighth piping path as viewed from the second pump 21. The twelfth on-off valve 28 opens and closes the pipe 29.

[0037] The above-mentioned on-off valves are, for example, solenoid valves. In the air conditioning apparatus 100, the relationship between the minimum inner diameter of each of the outward main pipe 41 and the return main pipe 42 and the maximum inner diameter of each of the plurality of outward branch pipes 51 a, 51 b, 51 c and the plurality of return branch pipes 52 a, 52 b, 52 c is not particularly limited. For example, the minimum inner diameter of each of the outward main pipe 41 and the return main pipe 42 may be equal to the maximum inner diameter of each of the plurality of outward branch pipes 51 a, 51 b, 51 c and the plurality of return branch pipes 52 a, 52 b, 52 c.

[0038] <Operation of the air conditioner> The air conditioner 100 performs full cooling operation shown in Fig. 2, cooling-dominated operation shown in Fig. 3, full heating operation shown in Fig. 4, heating-dominated operation shown in Fig. 5, or low outdoor air cooling operation shown in Fig. 6, depending on the operation mode of each of the multiple indoor units 50a, 50b, 50c and the outdoor air temperature taken in by the outdoor unit 40. Note that in Figs. 2 to 6, the on-off valves painted in black indicate on-off valves that are closed.

[0039] When all operating indoor units are in cooling operation mode, the air conditioner 100 performs full cooling operation. When all operating indoor units are in heating operation mode, the air conditioner 100 performs full heating operation. When some operating indoor units are in cooling operation mode and the remaining indoor units are in heating operation mode, if the total air conditioning load of the indoor units in cooling operation mode is greater than the total air conditioning load of the indoor units in heating operation mode, the air conditioner 100 performs cooling-dominated operation, and if the total air conditioning load of the indoor units in heating operation mode is greater than the total air conditioning load of the indoor units in cooling operation mode, the air conditioner 100 performs heating-dominated operation. When all operating indoor units are in cooling operation mode and the outdoor temperature is sufficiently lower than the indoor temperature (for example, the outdoor temperature is 5 degrees or lower), the air conditioner 100 performs low outdoor air cooling operation.

[0040] When the air conditioning apparatus 100 is in each operating state, at least one of a hot water circuit in which a heat medium heated by heat exchange with a refrigerant in the first heat exchanger 12 circulates, and a chilled water circuit in which a heat medium cooled by heat exchange with a refrigerant in the second heat exchanger 22 circulates, including the second piping path. More specifically, when the air conditioning apparatus 100 is in each operating state, at least one of a hot water circuit including the first heat exchanger 12 and an indoor heat exchanger in one of the indoor units 50 a, 50 b, and 50 c that is in the heating operation mode, and a chilled water circuit including the second heat exchanger 22 and an indoor heat exchanger in one of the indoor units 50 a, 50 b, and 50 c that is in the cooling operation mode is formed by the on-off valves included in the heat medium circuit.

[0041] The refrigeration cycles realized in the refrigerant circuit when the air conditioning apparatus 100 is in cooling-only operation, cooling-dominated operation, heating-only operation, and heating-dominated operation are all equivalent. When the air conditioning apparatus 100 is in cooling-only operation, cooling-dominated operation, heating-dominated operation, and heating-dominated operation, the first heat exchanger 12 functions as a condenser, and the second heat exchanger 22 functions as an evaporator in the refrigerant circuit. Specifically, the single-phase gas refrigerant discharged from the compressor 31 condenses into a single-phase liquid refrigerant by exchanging heat with a heat medium circulating in the hot water circuit in the first heat exchanger 12. The single-phase liquid refrigerant flowing out of the first heat exchanger 12 is decompressed and expanded in the expansion valve 32 into a two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant flowing out of the expansion valve 32 evaporates into a single-phase gas refrigerant by exchanging heat with a heat medium circulating in the chilled water circuit in the second heat exchanger 22. The single-phase gas refrigerant that has flowed out of the second heat exchanger 22 is sucked back into the compressor 31 and circulates through the refrigerant circuit.

[0042] When the air conditioner 100 is in a low outdoor air temperature cooling operation state, the compressor 31 of the refrigerant circuit is stopped and the refrigeration cycle is not realized.

[0043] <Cooling only operation> As shown in FIG. 2 , when the air conditioning apparatus 100 is performing cooling only operation, the second on-off valves 24a, 24b, 24c, the fourth on-off valves 25a, 25b, 25c, the fifth on-off valve 17, the twelfth on-off valve 28, the seventh on-off valve 33, and the ninth on-off valve 35 are opened, and the first on-off valves 14a, 14b, 14c, the third on-off valves 15a, 15b, 15c, the eleventh on-off valve 18, the sixth on-off valve 27, the eighth on-off valve 34, and the tenth on-off valve 36 are closed.

[0044] As a result, in this state, the heat medium circuit simultaneously forms a hot water circuit including the first pump 11, the first heat exchanger 12, the first branch header 13, the first merging header 16, the outward main pipe 41, the outdoor heat exchanger 43, and the return main pipe 42, and a chilled water circuit including the second pump 21, the second heat exchanger 22, the second branch header 23, the plurality of outward 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, and the second merging header 26. In the hot water circuit, the first pump 11, the first heat exchanger 12, the first branch header 13, the first merging header 16, the outward main pipe 41, the outdoor heat exchanger 43, and the return main pipe 42 are connected in series in this order. In the chilled water circuit, the second pump 21, the second heat exchanger 22, the second branch header 23, each of the plurality of outward branch pipes 51 a, 51 b, 51 c, each of the plurality of indoor heat exchangers 53 a, 53 b, 53 c, ​​each of the plurality of return branch pipes 52 a, 52 b, 52 c, and the second junction header 26 are connected in series in this order. In the chilled water circuit, each of the plurality of indoor heat exchangers 53 a, 53 b, 53 c is connected in parallel to each of the second branch header 23 and the second junction header 26.

[0045] In the hot water circuit, the heat medium flowing out of the first pump 11 is heated by heat exchange with single-phase gas refrigerant in the first heat exchanger 12. The heat medium heated in the first heat exchanger 12 passes through the first branch header 13, the fifth on-off valve 17, the first merging header 16, the seventh on-off valve 33, and the outward main pipe 41, and flows into the outdoor heat exchanger 43 in the outdoor unit 40. When the outdoor unit 40 is in operation, the outdoor blower 44 is operating, and the heat medium dissipates heat by exchanging heat with outside air blown by the outdoor blower 44 in the outdoor heat exchanger 43. The heat medium flowing out of the outdoor heat exchanger 43 flows into the first pump 11 via the return main pipe 42 and the ninth on-off valve 35, and circulates again in the hot water circuit.

[0046] In the chilled water circuit, the heat medium flowing out of the second pump 21 is cooled by heat exchange with a gas-liquid two-phase refrigerant in the second heat exchanger 22. The heat medium cooled in the second heat exchanger 22 flows into each indoor heat exchanger 53a, 53b, 53c via the second branch header 23, each second on-off valve 24a, 24b, 24c, and each outward branch pipe 51a, 51b, 51c. When each indoor unit 50a, 50b, 50c is in operation, each indoor fan 54a, 54b, 54c is operating, and the heat medium cools the indoor air blown by each indoor fan 54a, 54b, 54c in each indoor heat exchanger 53a, 53b, 53c. The heat medium flowing out of each indoor heat exchanger 53a, 53b, 53c passes through each return branch pipe 52a, 52b, 52c and each fourth on-off valve 25a, 25b, 25c, flows into the second junction header 26, and is joined in the second junction header 26. The heat medium joined in the second junction header 26 passes through the twelfth on-off valve 28 and flows into the second pump 21, and circulates again in the chilled water circuit.

[0047] In this state, the cold energy required by each of the indoor units 50a, 50b, and 50c in cooling operation is generated in the refrigerant circuit. The cold energy is transferred to the heat medium in the chilled water circuit in the second heat exchanger 22, and carried by the heat medium to each of the indoor heat exchangers 53a, 53b, and 53c, where it cools the indoor air. At the same time, the warm exhaust heat generated in the refrigerant circuit is transferred to the heat medium in the hot water circuit in the first heat exchanger 12, and carried by the heat medium to the outdoor heat exchanger 43, where it is released to the outside air. <Cooling-dominated operation> In the cooling-dominated operation shown in FIG. 3, the indoor units 50a and 50b are in the cooling operation mode, and the indoor unit 50c is in the heating operation mode. In this state, the first on-off valve 14c, the third on-off valve 15c, the fifth on-off valve 17, the second on-off valves 24a, 24b, the fourth on-off valves 25a, 25b, the twelfth on-off valve 28, the seventh on-off valve 33, and the ninth on-off valve 35 are opened, and the first on-off valves 14a, 14b, the third on-off valves 15a, 15b, the eleventh on-off valve 18, the second on-off valve 24c, the fourth on-off valve 25c, the sixth on-off valve 27, the eighth on-off valve 34, and the tenth on-off valve 36 are closed.

[0048] As a result, in this state, in the heat medium circuit, a hot water circuit including the first pump 11, the first heat exchanger 12, the first branch header 13, the first on-off valve 14c, the outward branch pipe 51c, the indoor heat exchanger 53c, the return branch pipe 52c, the third on-off valve 15c, the fifth on-off valve 17, the first merging header 16, the seventh on-off valve 33, the outward main pipe 41, the outdoor heat exchanger 43, the return main pipe 42, and the ninth on-off valve 35, and a cold water circuit including the second pump 21, the second heat exchanger 22, the second branch header 23, the second on-off valves 24a, 24b, the outward branch pipes 51a, 51b, the indoor heat exchangers 53a, 53b, the return branch pipes 52a, 52b, the fourth on-off valves 25a, 25b, the second merging header 26, and the twelfth on-off valve 28 are simultaneously formed.

[0049] In the hot water circuit, the first pump 11, the first heat exchanger 12, the first branch header 13, the outward branch pipe 51c, the indoor heat exchanger 53c, the return branch pipe 52c, and the first merging header 16 are connected in series in the stated order, and the first pump 11, the first heat exchanger 12, the first branch header 13, the first merging header 16, the outward main pipe 41, the outdoor heat exchanger 43, and the return main pipe 42 are connected in series in the stated order. In the hot water circuit, the indoor heat exchanger 53c and the outdoor heat exchanger 43 are connected in parallel to each other with respect to the first branch header 13, but are also connected in series to each other via the first merging header 16. The outdoor heat exchanger 43 is located downstream of the indoor heat exchanger 53c when viewed from the first pump 11.

[0050] In the chilled water circuit, the second pump 21, the second heat exchanger 22, the second branch header 23, the outward branch pipes 51a, 51b, the indoor heat exchangers 53a, 53b, the return branch pipes 52a, 52b, and the second merging header 26 are connected in series in the order listed.

[0051] In the hot water circuit, the heat medium flowing out of the first pump 11 is heated by heat exchange with a single-phase gas refrigerant in the first heat exchanger 12. A portion of the heat medium heated in the first heat exchanger 12 flows into the indoor heat exchanger 53c via the first branch header 13, the first on-off valve 14c, and the outward branch piping 51c, and heats the indoor air blown by the indoor blower 54c in the indoor heat exchanger 53c. The heat medium flowing out of the indoor heat exchanger 53c flows into the first junction header 16 via the return branch piping 52c and the third on-off valve 15c, and is merged in the first junction header 16 with the remainder of the heat medium heated in the first heat exchanger 12. The heat medium merged in the first merging header 16 flows into the outdoor heat exchanger 43 in the outdoor unit 40 via the seventh on-off valve 33 and the outbound main pipe 41, and dissipates heat in the outdoor heat exchanger 43 by exchanging heat with outside air blown by the outdoor blower 44. The heat medium flowing out of the outdoor heat exchanger 43 flows into the first pump 11 via the inbound main pipe 42 and the ninth on-off valve 35, and circulates again through the hot water circuit.

[0052] In the chilled water circuit, the heat medium flowing out of the second pump 21 is cooled by heat exchange with a gas-liquid two-phase refrigerant in the second heat exchanger 22, and then flows into the indoor heat exchangers 53a, 53b via the second branch header 23, the second on-off valves 24a, 24b, and the outward branch pipes 51a, 51b. The indoor air blown by the indoor fans 54a, 54b is cooled in the indoor heat exchangers 53a, 53b. The heat medium flowing out of the indoor heat exchangers 53a, 53b flows into the second junction header 26 via the return branch pipes 52a, 52b and the fourth on-off valves 25a, 25b, and then merges in the second junction header 26. The heat medium merged in the second junction header 26 flows into the second pump 21 via the twelfth on-off valve 28 and circulates again in the chilled water circuit.

[0053] In this state, the refrigerant circuit generates the cold energy required by each of the indoor units 50a, 50b in cooling operation, and the refrigerant circuit generates the hot energy required by the indoor unit 50c in heating operation. The cold energy is transferred to the heat medium in the cold water circuit by the second heat exchanger 22 and carried by the heat medium to each of the indoor heat exchangers 53a, 53b, where it cools the indoor air. At the same time, the hot energy is transferred to the heat medium in the hot water circuit by the first heat exchanger 12 and carried by the heat medium to the indoor heat exchanger 53c, where it heats the indoor air. The hot exhaust heat generated in the refrigerant circuit and the hot water circuit is carried by the heat medium in the hot water circuit to the outdoor heat exchanger 43, where it is released to the outside air.

[0054] Note that, when the amount of heat (hot exhaust heat) that can be released to the outside air in the outdoor heat exchanger 43 is small, the fifth on-off valve 17 may be closed. When the amount of hot exhaust heat from the outdoor heat exchanger 43 is large, the fifth on-off valve 17 is opened to reduce the flow rate of the heat medium flowing through the indoor heat exchanger 53c, thereby preventing the heat medium flowing through the indoor heat exchanger 53c from excessively heating the indoor air.

[0055] <Heating only operation> As shown in FIG. 4 , when the air conditioning apparatus 100 is performing heating only operation, the first on-off valves 14a, 14b, 14c, the plurality of third on-off valves 15a, 15b, 15c, the eleventh on-off valve 18, the sixth on-off valve 27, the eighth on-off valve 34, and the tenth on-off valve 36 are opened, and the plurality of second on-off valves 24a, 24b, 24c, the plurality of fourth on-off valves 25a, 25b, 25c, the fifth on-off valve 17, the twelfth on-off valve 28, the seventh on-off valve 33, and the ninth on-off valve 35 are closed.

[0056] As a result, in this state, in the heat medium circuit, a hot water circuit including the first pump 11, the first heat exchanger 12, the first branch header 13, a plurality of outward branch pipes 51a, 51b, 51c, a plurality of indoor heat exchangers 53a, 53b, 53c, a plurality of return branch pipes 52a, 52b, 52c, and the first merging header 16, and a cold water circuit including the second pump 21, the second heat exchanger 22, the second branch header 23, the second merging header 26, the outward main pipe 41, the outdoor heat exchanger 43, and the return main pipe 42 are simultaneously formed.

[0057] In the hot water circuit, the first pump 11, the first heat exchanger 12, the first branch header 13, the plurality of outward branch pipes 51a, 51b, 51c, the plurality of indoor heat exchangers 53a, 53b, 53c, the plurality of return branch pipes 52a, 52b, 52c, and the first merging header 16 are connected in series in the order listed. In the chilled water circuit, the second pump 21, the second heat exchanger 22, the second branch header 23, the second merging header 26, the outward main pipe 41, the outdoor heat exchanger 43, and the return main pipe 42 are connected in series in the order listed. In the hot water circuit, the plurality of indoor heat exchangers 53a, 53b, 53c are connected in parallel to the second branch header 23 and the second merging header 26.

[0058] In the hot water circuit, the heat medium flowing out of the first pump 11 is heated by heat exchange with single-phase gas refrigerant in the first heat exchanger 12. The heat medium heated in the first heat exchanger 12 flows into the indoor heat exchangers 53a, 53b, and 53c via the first branch header 13, the first on-off valves 14a, 14b, and 14c, and the outward branch pipes 51a, 51b, and 51c. When the indoor units 50a, 50b, and 50c are operating, the indoor fans 54a, 54b, and 54c are operating, and the heat medium heats the indoor air blown by the indoor fans 54a, 54b, and 54c in the indoor heat exchangers 53a, 53b, and 53c. The heat medium flowing out of each indoor heat exchanger 53a, 53b, 53c passes through each return branch pipe 52a, 52b, 52c and each fourth on-off valve 25a, 25b, 25c, flows into the first junction header 16, and is joined in the first junction header 16. The heat medium joined in the first junction header 16 flows into the first pump 11 through the eleventh on-off valve 18, and circulates again in the hot water circuit.

[0059] In the chilled water circuit, the heat medium flowing out from the second pump 21 is cooled by heat exchange with gas-liquid two-phase refrigerant in the second heat exchanger 22. The heat medium cooled in the second heat exchanger 22 flows into the outdoor heat exchanger 43 via the second branch header 23, the sixth on-off valve 27, the second merging header 26, the eighth on-off valve 34, and the outbound main pipe 41. In the outdoor heat exchanger 43, the heat medium absorbs heat from outdoor air blown by the outdoor blower 44. The heat medium flowing out from the outdoor heat exchanger 43 flows into the second pump 21 via the return main pipe 42 and the tenth on-off valve 36, and circulates again in the chilled water circuit.

[0060] In this state, the hot heat required by each of the indoor units 50a, 50b, and 50c during heating operation is generated in the refrigerant circuit. The hot heat is transferred to the heat medium in the hot water circuit by the first heat exchanger 12, and then carried by the heat medium to each of the indoor heat exchangers 53a, 53b, and 53c, where it heats the indoor air. At the same time, the cold exhaust heat generated in the refrigerant circuit is transferred to the heat medium in the cold water circuit by the second heat exchanger 22, and then carried by the heat medium to the outdoor heat exchanger 43, where it is released into the outside air.

[0061] 5, the indoor units 50a and 50b are in the heating operation mode, and the indoor unit 50c is in the cooling operation mode. In this state, the first on-off valves 14a and 14b, the third on-off valves 15a and 15b, the eleventh on-off valve 18, the second on-off valve 24c, the fourth on-off valve 25c, the sixth on-off valve 27, the eighth on-off valve 34, and the tenth on-off valve 36 are opened, and the first on-off valve 14c, the third on-off valve 15c, the fifth on-off valve 17, the second on-off valves 24a and 24b, the fourth on-off valves 25a and 25b, the twelfth on-off valve 28, the seventh on-off valve 33, and the ninth on-off valve 35 are closed.

[0062] As a result, in this state, in the heat medium circuit, a hot water circuit including the first pump 11, the first heat exchanger 12, the first branch header 13, the first on-off valves 14a, 14b, the outward branch pipes 51a, 51b, the indoor heat exchangers 53a, 53b, the return branch pipes 52a, 52b, the third on-off valves 15a, 15b, the first merging header 16, and the eleventh on-off valve 18, and a cold water circuit including the second pump 21, the second heat exchanger 22, the second branch header 23, the second on-off valve 24c, the outward branch pipe 51c, the indoor heat exchanger 53c, the return branch pipe 52c, the fourth on-off valve 25c, the second merging header 26, the sixth on-off valve 27, the eighth on-off valve 34, the outward main pipe 41, the outdoor heat exchanger 43, the return main pipe 42, and the tenth on-off valve 36 are simultaneously formed.

[0063] In the hot water circuit, the first pump 11, the first heat exchanger 12, the first branch header 13, the outward branch pipes 51a, 51b, the indoor heat exchangers 53a, 53b, the return branch pipes 52a, 52b, and the first merging header 16 are connected in series.

[0064] In the chilled water circuit, the second pump 21, the second heat exchanger 22, the second branch header 23, the outward branch pipe 51c, the indoor heat exchanger 53c, the return branch pipe 52c, and the second merging header 26 are connected in series in the order listed, and the second pump 21, the second heat exchanger 22, the second branch header 23, the second merging header 26, the outward main pipe 41, the outdoor heat exchanger 43, and the return main pipe 42 are connected in series in the order listed. In the chilled water circuit, the indoor heat exchanger 53c and the outdoor heat exchanger 43 are connected in parallel to each other with respect to the second branch header 23, but are also connected in series to each other via the second merging header 26. The outdoor heat exchanger 43 is located downstream of the indoor heat exchanger 53c when viewed from the second pump 21.

[0065] In the hot water circuit, the heat medium flowing out of the first pump 11 is heated by heat exchange with single-phase gas refrigerant in the first heat exchanger 12, and flows into the indoor heat exchangers 53a, 53b via the first branch header 13, the first on-off valves 14a, 14b, and the outward branch pipes 51a, 51b. The heat medium flows into the indoor heat exchangers 53a, 53b via the return branch pipes 52a, 52b and the third on-off valves 15a, 15b. The heat medium flows into the first junction header 16 and merges with the first junction header 16. The heat medium merged in the first junction header 16 flows into the first pump 11 via the eleventh on-off valve 18 and circulates again through the hot water circuit.

[0066] In the chilled water circuit, the heat medium flowing out of the second pump 21 is cooled by heat exchange with a gas-liquid two-phase refrigerant in the second heat exchanger 22. A portion of the heat medium cooled in the second heat exchanger 22 flows into the indoor heat exchanger 53c via the second branch header 23, the second on-off valve 24c, and the outward branch piping 51c, and cools the indoor air blown by the indoor fan 54c in the indoor heat exchanger 53c. The heat medium flowing out of the indoor heat exchanger 53c flows into the second junction header 26 via the return branch piping 52c and the fourth on-off valve 25c, and is merged in the second junction header 26 with the remainder of the heat medium cooled in the second heat exchanger 22. The heat medium that has merged in the second merging header 26 flows into the outdoor heat exchanger 43 in the outdoor unit 40 via the eighth on-off valve 34 and the outbound main pipe 41, and absorbs heat in the outdoor heat exchanger 43 by exchanging heat with outside air blown by the outdoor blower 44. The heat medium that has flowed out of the outdoor heat exchanger 43 flows into the second pump 21 via the inbound main pipe 42 and the tenth on-off valve 36, and circulates again in the chilled water circuit.

[0067] In this state, the refrigerant circuit generates the hot heat required by each indoor unit 50a, 50b in heating operation, and the refrigerant circuit generates the cold heat required by the indoor unit 50c in cooling operation. The hot heat is transferred to the heat medium in the hot water circuit in the first heat exchanger 12, and carried by the heat medium to each indoor heat exchanger 53a, 53b, where it heats the indoor air. The cold heat is transferred to the heat medium in the cold water circuit in the second heat exchanger 22, and carried by the heat medium to the indoor heat exchanger 53c, where it cools the indoor air. The cold exhaust heat generated in the refrigerant circuit and hot water circuit is carried by the heat medium in the cold water circuit to the outdoor heat exchanger 43, where it is released to the outside air.

[0068] Note that, when the amount of heat (amount of cold exhaust heat) that can be released to the outside air in the outdoor heat exchanger 43 is small, the sixth on-off valve 27 may be closed. When the amount of cold exhaust heat from the outdoor heat exchanger 43 is large, the sixth on-off valve 27 is opened to reduce the flow rate of the heat medium flowing through the indoor heat exchanger 53c, thereby preventing the heat medium flowing through the indoor heat exchanger 53c from excessively cooling the indoor air.

[0069] <Low outdoor air cooling operation> As shown in Figure 6, when the air conditioning apparatus 100 is performing low outdoor air cooling operation, the multiple second on-off valves 24a, 24b, 24c, the multiple fourth on-off valves 25a, 25b, 25c, the eighth on-off valve 34, and the tenth on-off valve 36 are opened, and the first on-off valves 14a, 14b, 14c, the multiple third on-off valves 15a, 15b, 15c, the fifth on-off valve 17, the sixth on-off valve 27, the eleventh on-off valve 18, the twelfth on-off valve 28, the seventh on-off valve 33, and the ninth on-off valve 35 are closed.

[0070] In this state, the compressor 31 of the refrigerant circuit is stopped, and the refrigeration cycle is not realized. Therefore, the first heat exchanger 12 does not function as a hot heat source. Similarly, the second heat exchanger 22 does not function as a cold heat source.

[0071] In this state, only the chilled water circuit is formed in the heat medium circuit. The chilled water circuit includes the second pump 21, the second heat exchanger 22, the second branch header 23, each of the plurality of outward branch pipes 51 a, 51 b, and 51 c, each of the plurality of indoor heat exchangers 53 a, 53 b, and 53 c, ​​each of the plurality of return branch pipes 52 a, 52 b, and 52 c, the second merging header 26, the eighth on-off valve 34, the outward main pipe 41, the outdoor heat exchanger 43, the return main pipe 42, and the tenth on-off valve 36. In the chilled water circuit, the second pump 21, the second heat exchanger 22, the second branch header 23, each of the plurality of outward branch pipes 51a, 51b, and 51c, each of the plurality of indoor heat exchangers 53a, 53b, and 53c, each of the plurality of return branch pipes 52a, 52b, and 52c, the second merging header 26, the outward main pipe 41, the outdoor heat exchanger 43, and the return main pipe 42 are connected in series in this order. In the chilled water circuit, each of the plurality of indoor heat exchangers 53a, 53b, and 53c is connected in parallel to each of the second branch header 23 and the second merging header 26. The outdoor heat exchanger 43 is connected in series to each of the plurality of indoor heat exchangers 53a, 53b, and 53c. The outdoor heat exchanger 43 is located downstream of the indoor heat exchanger 53c when viewed from the second pump 21.

[0072] In the chilled water circuit, the heat medium flowing out of the second pump 21 passes through the second heat exchanger 22, passes through the second branch header 23 and the second on-off valves 24a, 24b, and 24c, and flows into the indoor heat exchangers 53a, 53b, and 53c. In the indoor heat exchangers 53a, 53b, and 53c, the heat medium cools the indoor air blown by the indoor fans 54a, 54b, and 54c. The heat medium flowing out of the indoor fans 54a, 54b, and 54c flows into the outdoor heat exchanger 43 via the fourth on-off valve 25, the second merging header 26, and the eighth on-off valve 34. In the outdoor heat exchanger 43, the heat medium is cooled by the outside air blown by the outdoor fan 44. The heat medium flowing out of the outdoor heat exchanger 43 flows into the second pump 21 via the tenth on-off valve 36 and circulates through the chilled water circuit.

[0073] In this state, the cold energy required by each indoor unit 50a, 50b, 50c during cooling operation is entirely supplied by absorbing heat from the outside air, which is lower in temperature than the room, and by transporting cold energy through the chilled water circuit. In this state, the compressor 31 of the refrigeration cycle is stopped, and low-temperature outside air can be directly used as a cold energy source, so power consumption is reduced compared to the full cooling operation state.

[0074] Note that, when the flow rate (circulation flow rate) of the heat medium circulating through the heat medium circuit while the second pump 21 is operating is low, or when the power consumption during operation of the second pump 21 is high, the first pump 11 may be operated, the seventh on-off valve 33 and the ninth on-off valve 35 may be opened, the second on-off valve 24 and the fourth on-off valve 25 corresponding to some of the indoor units 50 in cooling operation may be closed, and the first on-off valve 14 and the third on-off valve 15 corresponding to those indoor units 50 may be opened. In this way, a chilled water circuit including the second pump 21 and a chilled water circuit including the first pump 11 may be simultaneously formed in the heat medium circuit, so that the total value of the circulation flow rates of the second pump 21 and the first pump 11 may be maximized, or the total value of the power consumption of the second pump 21 and the first pump 11 may be minimized.

[0075] <Operation and Effect> In the air conditioning apparatus 100, only the relay unit 10 has a refrigerant circuit, and heat is transported between the relay unit 10 and the outdoor unit 40, and between the relay unit 10 and each of the indoor units 50a, 50b, and 50c by a heat medium. Therefore, in the air conditioning apparatus 100, the amount of refrigerant charged in the air conditioning apparatus 100 can be reduced compared to the conventional air conditioning apparatus described above, regardless of the lengths of the outgoing main pipe 41 and the return main pipe 42 that connect the relay unit 10 and the outdoor unit 40, and the multiple outgoing branch pipes 51a, 51b, and 51c and the multiple return branch pipes 52a, 52b, and 52c that connect the relay unit 10 and each of the indoor units 50a, 50b, and 50c.

[0076] Furthermore, the internal pressure of the pipes (e.g., water pipes through which water flows) that constitute the heat medium circuit is generally lower than the internal pressure of the refrigerant pipes that constitute the refrigerant circuit. For example, the internal pressure of the refrigerant pipes is high, reaching a maximum of approximately 4 MPa, while the internal pressure of the water pipes is less than 1 MPa at most. Therefore, the pipes that constitute the heat medium circuit can be installed more easily than the refrigerant pipes, and therefore the air conditioning apparatus 100 can be installed more easily than conventional air conditioning apparatuses in which heat is transported between the relay unit and the outdoor units and each indoor unit by a refrigerant. Furthermore, the air conditioning apparatus 100 has a reduced risk of refrigerant leakage compared to the conventional air conditioning apparatuses.

[0077] Furthermore, even if the heat medium leaks from the heat medium circuit of the air conditioning device 100, the global warming potential (GWP) of the heat medium is lower than that of carbon dioxide, so the impact on global warming is smaller than when a refrigerant leaks in a conventional air conditioning device.

[0078] Furthermore, in the air conditioning device 100, the relay unit 10 and the outdoor unit 40 and the relay unit 10 and each indoor unit are connected by two pipes each, which makes installation easier than when the relay unit 10 and the outdoor unit 40 and the relay unit 10 and each indoor unit are connected by three pipes each.

[0079] Furthermore, the air conditioning apparatus 100 can switch between full cooling operation, cooling-dominated operation, full heating operation, and heating-dominated operation according to the operating mode of each of the multiple indoor units 50a, 50b, and 50c, using the hot and cold energy generated by the refrigeration cycle implemented in the refrigerant circuit included in the relay unit 10. For example, in air conditioning equipment for large buildings, indoor units located in general living rooms may operate in heating mode, while indoor units located in rooms with high heat output, such as computer rooms or kitchens, may operate in cooling mode. The air conditioning apparatus 100 is well suited for such air conditioning equipment.

[0080] Furthermore, in the air conditioner 100, when the outdoor air temperature is sufficiently lower than the temperature of the room where the indoor unit in cooling operation is installed, low outdoor air temperature cooling operation is performed. In low outdoor air temperature cooling operation, the compressor 31 of the refrigeration cycle is stopped and the low temperature outdoor air is directly used as a cold heat source, resulting in less power consumption than in full cooling operation.

[0081] Furthermore, in the air conditioning apparatus 100, by closing the eleventh on-off valve 18 during cooling-dominated operation, the hot heat transferred to the heat medium in the first heat exchanger 12 can be supplied to the indoor unit 50c in heating operation, and then the hot exhaust heat can be supplied to the outdoor unit 40. As a result, a decrease in the temperature of the heat medium in the indoor heat exchanger 53c can be suppressed, so the temperature difference between the heat medium in the indoor heat exchanger 53c and the indoor air can be maintained, and a decrease in the heating capacity of the indoor unit 50 in heating operation during cooling-dominated operation can be prevented.

[0082] Similarly, in heating-dominated operation, by closing the twelfth on-off valve 28, the cold heat transferred to the heat medium in the second heat exchanger 22 is supplied to the indoor unit 50c in cooling operation, and then the cold exhaust heat can be supplied to the outdoor unit 40. As a result, the temperature rise of the heat medium in the indoor heat exchanger 53c can be suppressed, so the temperature difference between the heat medium in the indoor heat exchanger 53c and the indoor air can be maintained, and a decrease in the cooling capacity of the indoor unit 50 in cooling operation during heating-dominated operation can be prevented.

[0083] As described above, in the air conditioning apparatus 100, not only can the amount of refrigerant charged be reduced compared to the conventional refrigeration cycle apparatus described above, but the difficulty and cost of installation and the risk of refrigerant leakage are low, power consumption is kept low during low outdoor air temperature cooling operation, a decrease in the heating capacity of the indoor unit 50 during heating operation is prevented during cooling-dominated operation, and further, a decrease in the cooling capacity of the indoor unit 50 during cooling operation is prevented during heating-dominated operation.

[0084] Embodiment 2. As shown in Figure 7, an air conditioning apparatus 101 according to embodiment 2 has basically the same configuration as the air conditioning apparatus 100 according to embodiment 1 and achieves the same effects, but differs from the air conditioning apparatus 100 in that the heat medium circuit does not include the third bypass path connecting the seventh piping path and the ninth piping path, and the eleventh on-off valve 18. The following mainly describes the differences between the air conditioning apparatus 101 and the air conditioning apparatus 100.

[0085] In the air conditioning apparatus 101, the heat medium circuit does not have a third bypass path connecting the seventh piping path and the ninth piping path, nor an eleventh on-off valve 18 that opens and closes the third bypass path, within the relay unit 10. From a different perspective, the first piping path does not have a pipe 19 connecting the first junction header 16 and the first pump 11.

[0086] The heat medium circuit of the air conditioning apparatus 101 is the same as the heat medium circuit of the air conditioning apparatus 100, except that the seventh piping path and the ninth piping path cannot be connected via the third bypass path. The air conditioning apparatus 101 can perform at least full cooling operation, cooling-dominated operation, or low outdoor air cooling operation.

[0087] The air conditioner 101 is suitable for air conditioning equipment in which the total air conditioning load of the indoor units in the cooling operation mode is always greater than the total air conditioning load of the indoor units in the heating operation mode.

[0088] Embodiment 3. As shown in Figure 8, an air conditioning apparatus 102 according to embodiment 3 has basically the same configuration as the air conditioning apparatus 100 according to embodiment 1 and achieves the same effects, but differs from the air conditioning apparatus 100 in that the minimum value of the flow path cross-sectional area of ​​each of the outbound main pipe 41 and the inbound main pipe 42 is greater than the maximum value of the flow path cross-sectional area of ​​each of the multiple outbound branch pipes 51a, 51b, and 51c and the multiple inbound branch pipes 52a, 52b, and 52c. The following will mainly describe the differences between the air conditioning apparatus 102 and the air conditioning apparatus 100. In Figure 8, the heat medium flow paths formed inside each of the outbound main pipe 41, the inbound main pipe 42, the multiple outbound branch pipes 51a, 51b, and 51c, and the multiple inbound branch pipes 52a, 52b, and 52c are indicated by dashed lines. The minimum value of the flow path cross-sectional area of ​​each of the outward main pipe 41 and the return main pipe 42 is greater than the maximum value of the flow path cross-sectional area of ​​each of the plurality of outward branch pipes 51a, 51b, 51c and the plurality of return branch pipes 52a, 52b, 52c. Each of the outward main pipe 41, the return main pipe 42, the plurality of outward branch pipes 51a, 51b, 51c, and the plurality of return branch pipes 52a, 52b, 52c is, for example, a circular pipe. In this case, the minimum value of the inner diameter of each of the outward main pipe 41 and the return main pipe 42 is greater than the maximum value of the inner diameter of each of the plurality of outward branch pipes 51a, 51b, 51c and the plurality of return branch pipes 52a, 52b, 52c.

[0089] The flow rate of the heat medium flowing through each of the outbound main pipe 41 and the return main pipe 42 is maximum in an all-cooling operation state or an all-heating operation state among the various operating states that the air conditioning apparatus 102 can be in. In the air conditioning apparatus 102, the minimum value of the flow path cross-sectional area of ​​each of the outbound main pipe 41 and the return main pipe 42 is greater than the maximum value of the flow path cross-sectional area of ​​each of the multiple outbound branch pipes 51 a, 51 b, 51 c and the multiple return branch pipes 52 a, 52 b, 52 c, so that the flow resistance inside each of the outbound main pipe 41 and the return main pipe 42 can be suppressed.

[0090] Furthermore, in the air conditioning apparatus 102, the internal volumes of the plurality of outward branch pipes 51 a, 51 b, 51 c and the plurality of return branch pipes 52 a, 52 b, 52 c are not designed to be excessively large, and therefore it is possible to reduce the total amount of heat medium (heat medium filling amount) filled in the heat medium circuit of the air conditioning apparatus 102. As a result, in the air conditioning apparatus 102, it is possible to shorten the time required for the air conditioning capacity to be exerted when starting full cooling operation, cooling-dominated operation, full heating operation, heating-dominated operation, or low outdoor air cooling operation, and to improve the ability of the air conditioning capacity to follow the air conditioning load.

[0091] In addition, the air conditioning apparatus 102 according to embodiment 3 may have a configuration similar to that of the air conditioning apparatus 101 according to embodiment 2, except that the minimum value of the flow path cross-sectional area of ​​each of the outbound main pipe 41 and the inbound main pipe 42 is greater than the maximum value of the flow path cross-sectional area of ​​each of the multiple outbound branch pipes 51a, 51b, 51c and the multiple inbound branch pipes 52a, 52b, 52c.

[0092] Embodiment 4. As shown in FIG. 9 , an air conditioning apparatus 103 according to embodiment 4 has a configuration basically similar to that of the air conditioning apparatus 100 according to embodiment 1 and achieves similar effects. However, it differs from the air conditioning apparatus 100 in that the outdoor heat exchanger 43 has a first heat exchange section 43a and a second heat exchange section 43b with a smaller internal volume than the first heat exchange section 43a, and the area expansion rate of the second heat exchange section 43b is smaller than the area expansion rate of the first heat exchange section 43a. In this specification, the area expansion rate is defined as the value obtained by dividing the area of ​​the outer surface of the outdoor heat exchanger that can come into contact with outdoor air by the area of ​​the inner surface of the outdoor heat exchanger that can come into contact with the heat medium. Below, the differences between the air conditioning apparatus 103 and the air conditioning apparatus 100 will be mainly described.

[0093] The first heat exchange section 43a and the second heat exchange section 43b are connected in parallel to the outgoing main pipe 41 and the returning main pipe 42.

[0094] In the indoor unit 40, the heat medium circuit has an eleventh piping path connecting the other end of the outgoing main piping 41 and one end of the first heat exchanger 43a, and a twelfth piping path connecting the other end of the outgoing main piping 41 and one end of the second heat exchanger 43b. The eleventh and twelfth piping paths have, for example, a common portion and a non-common portion branching off from the common portion. In this case, in the outdoor unit 40, the heat medium circuit further has a thirteenth on-off valve 45a that opens and closes the non-common portion of the eleventh piping path, and a fourteenth on-off valve 45b that opens and closes the non-common portion of the twelfth piping path.

[0095] In the indoor unit 40, the heat medium circuit further has a thirteenth piping path that connects the other end of the first heat exchanger 43a and the other end of the return main piping 42, and a fourteenth piping path that connects the other end of the second heat exchanger 43b and the other end of the return main piping 42. The thirteenth piping path and the fourteenth piping path have, for example, a common portion and a non-common portion that branches off from the common portion.

[0096] For example, the relative positional relationship between the one end of the first heat exchanger 43a connected to the other end of the outbound main pipe 41 and the other end of the first heat exchanger 43a connected to the other end of the return main pipe 42 is equivalent to the relative positional relationship between the one end of the second heat exchanger 43b connected to the other end of the outbound main pipe 41 and the other end of the second heat exchanger 43b connected to the other end of the return main pipe 42.

[0097] For example, one outdoor fan 44 is provided to blow outdoor air to each of the first heat exchange section 43a and the second heat exchange section 43b of the outdoor heat exchanger 43. Note that different outdoor fans may be provided to blow outdoor air to each of the first heat exchange section 43a and the second heat exchange section 43b of the outdoor heat exchanger 43.

[0098] In the air conditioning apparatus 103, the outdoor heat exchanger 43 has a first heat exchange section 43a and a second heat exchange section 43b that has a smaller internal volume than the first heat exchange section 43a, and the area expansion rate of the second heat exchange section 43b is smaller than the area expansion rate of the first heat exchange section 43a. Therefore, when the air conditioning apparatus 103 is performing low outdoor air temperature cooling operation, the amount of heat released from the outdoor heat exchanger 43 to the outdoor air can be reduced compared to the air conditioning apparatus 100, and an excessive drop in the temperature of the heat medium in the outdoor heat exchanger 43 can be prevented.

[0099] The air conditioning apparatus 103 is particularly suitable for air conditioning apparatuses that use antifreeze as a heat medium. Antifreeze increases in viscosity and flow resistance as the temperature drops. Therefore, if the temperature of the antifreeze increases excessively in the outdoor heat exchanger 43, the power consumption of the second pump 21 (or the first pump 11 when the second pump 21 and the first pump 11 are simultaneously driven during low outdoor air temperature cooling operation as described above) increases. In contrast, even when the heat medium is antifreeze, the air conditioning apparatus 103 can prevent the temperature of the heat medium from decreasing excessively in the outdoor heat exchanger 43, thereby preventing an increase in the flow resistance of the antifreeze, and as a result, preventing an increase in the power consumption of the second pump 21.

[0100] Preferably, when the air conditioning apparatus 103 is performing low outdoor air temperature cooling operation, the thirteenth on-off valve 45a is closed and the fourteenth on-off valve 45b is open. In this case, during low outdoor air temperature cooling operation, the heat medium flows only into the second heat exchange section 43b, which has a relatively small internal volume, of the outdoor heat exchanger 43. As a result, when the air conditioning apparatus 103 is performing low outdoor air temperature cooling operation, the thirteenth on-off valve 45a is closed and the fourteenth on-off valve 45b is open, thereby preventing the temperature of the antifreeze solution in the first heat exchange section 43a from dropping excessively and suppressing an increase in power consumption of the pump.

[0101] The air conditioning apparatus 103 according to embodiment 4 may have a configuration similar to that of the air conditioning apparatus 101 according to embodiment 2 or the air conditioning apparatus 101 according to embodiment 3, except that the outdoor heat exchanger 43 has a first heat exchange section 43a and a second heat exchange section 43b having a smaller internal volume than the first heat exchange section 43a, and the area expansion rate of the second heat exchange section 43b is smaller than the area expansion rate of the first heat exchange section 43a.

[0102] Although the embodiments of the present disclosure have been described above, the above-described embodiments can be modified in various ways. Furthermore, the scope of the present disclosure is not limited to the above-described embodiments. The scope of the present disclosure is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0103] 10 relay unit, 11 first pump, 12 first heat exchanger, 13 first branch header, 14a, 14b, 14c first on-off valve, 15a, 15b, 15c third on-off valve, 16 first merging header, 17 fifth on-off valve, 18 eleventh on-off valve, 19, 29 piping, 21 second pump, 22 second heat exchanger, 23 second branch header, 24a, 24b, 24c second on-off valve, 25a, 25b, 25c fourth on-off valve, 26 second merging header, 27 sixth on-off valve, 28 twelfth on-off valve, 31 compressor, 32 expansion valve, 33 seventh on-off valve, 34 eighth on-off valve, 35 ninth on-off valve, 36 tenth on-off valve, 40 outdoor unit, 41 outward main piping, 42 return main piping, 43 outdoor heat exchanger, 43a First heat exchange section, 43b Second heat exchange section, 44 Outdoor blower, 45a Thirteenth on-off valve, 45b Fourteenth on-off valve, 50a, 50b, 50c Indoor unit, 51a, 51b, 51c Outward branch piping, 52a, 52b, 52c Return branch piping, 53a, 53b, 53c Indoor heat exchanger, 54a, 54b, 54c Indoor blower, 100, 101, 102, 103 Air conditioning apparatus.

Claims

1. An outdoor unit, a plurality of indoor units, and a relay unit, a refrigerant circuit in which a refrigerant circulates, and a heat medium circuit in which a heat medium having a lower global warming potential (GWP) than the refrigerant circulates, wherein the refrigerant circuit is disposed in the relay unit and has a compressor, a first heat exchanger, an expansion valve, and a second heat exchanger, and the refrigerant is provided to circulate in order through the compressor, the first heat exchanger, the expansion valve, and the second heat exchanger, the heat medium circuit includes a first pump, a second pump, the first heat exchanger, the second heat exchanger, a first branch header, a second branch header, a first confluence header, a second confluence header, a plurality of first on-off valves, a plurality of second on-off valves, a plurality of third on-off valves, a plurality of fourth on-off valves, a fifth on-off valve, a sixth on-off valve, a seventh on-off valve, an eighth on-off valve, a ninth on-off valve, and a tenth on-off valve, all of which are disposed in the relay unit; an outdoor heat exchanger disposed in the outdoor unit; an indoor heat exchanger disposed in each of the plurality of indoor units; a supply main pipe and a return main pipe connecting the relay unit and the outdoor unit; and a plurality of supply branch pipes and a plurality of return branch pipes connecting the relay unit and each of the plurality of indoor units, wherein one end of each of the plurality of supply branch pipes is connected to the first branch header via each of the plurality of first on-off valves and is connected to the second branch header via each of the plurality of second on-off valves; the other end of each of the plurality of supply branch pipes is connected to one end of the indoor heat exchanger of each of the plurality of indoor units; one end of each of the plurality of return branch pipes is connected to the first confluence header via each of the plurality of third on-off valves and is connected to the second confluence header via each of the plurality of fourth on-off valves; the other end of each of the plurality of return branch pipes is connected to the other end of the indoor heat exchanger of each of the plurality of indoor units; the first branch header is connected to the first confluence header via the fifth on-off valve; the second branch header is connected to the second confluence header via the sixth on-off valve; the first confluence header, the first pump, the first heat exchanger, and the first branch header are connected in sequence; the second confluence header, the second pump, the second heat exchanger, and the second branch header are connected in sequence; one end of the supply main pipe is connected to the first confluence header via the seventh on-off valve and is connected to the second confluence header via the eighth on-off valve; The other end of the forward main pipe is connected to one end of the outdoor heat exchanger of the outdoor unit. One end of the return main pipe is connected to the first pump via the ninth on-off valve and is also connected to the second pump via the tenth on-off valve. The other end of the return main pipe is connected to the other end of the outdoor heat exchanger of the outdoor unit. An air conditioner.

2. The heat medium circuit further has an eleventh on-off valve and a twelfth on-off valve. The connection point between the forward main pipe and the first confluence header is connected to the connection point between the return main pipe and the first pump via the eleventh on-off valve. The connection point between the forward main pipe and the second confluence header is connected to the connection point between the return main pipe and the second pump via the twelfth on-off valve. The air conditioner according to claim 1.

3. In the heat medium circuit, the eleventh on-off valve is arranged on the downstream side as viewed from the first pump rather than the first confluence header, and the twelfth on-off valve is arranged on the downstream side as viewed from the second pump rather than the second confluence header. The air conditioner according to claim 2.

4. When each of the plurality of indoor units performs a cooling operation in a low outside air state where the outside air temperature where the outdoor unit is arranged is lower than the indoor air temperature of each room where each of the plurality of indoor units is arranged. The compressor stops. The plurality of third on-off valves, the plurality of fourth on-off valves, the eighth on-off valve, and the tenth on-off valve are opened, and the plurality of first on-off valves, the plurality of second on-off valves, the fifth on-off valve, the sixth on-off valve, the seventh on-off valve, the ninth on-off valve, the eleventh on-off valve, and the twelfth on-off valve are closed. In the heat medium circuit, the second pump, the second heat exchanger, the second branch header, each of the plurality of third on-off valves, each of the plurality of forward branch pipes, the indoor heat exchanger, each of the plurality of return branch pipes, each of the plurality of fourth on-off valves, the second confluence header, the eighth on-off valve, the forward main pipe, the outdoor heat exchanger, the return main pipe, and the tenth on-off valve are connected in sequence. The air conditioner according to claim 2.

5. The minimum value of the flow path cross-sectional area of each of the forward main pipe and the return main pipe is larger than the maximum value of the flow path cross-sectional area of each of the plurality of forward branch pipes and the plurality of return branch pipes. The air conditioner according to any one of claims 1 to 4.

6. The outdoor heat exchanger has a plurality of heat exchange parts connected in parallel to the forward main pipe and the return main pipe, The plurality of heat exchange parts include a first heat exchange part and a second heat exchange part having an internal volume smaller than that of the first heat exchange part, When a value obtained by dividing an area of an outer surface of the outdoor heat exchanger capable of contacting outdoor air by an area of an inner surface of the outdoor heat exchanger capable of contacting the heat medium is defined as an area expansion ratio, the area expansion ratio of the second heat exchange part is smaller than the area expansion ratio of the first heat exchange part. The air conditioner according to any one of claims 1 to 4.

7. The air conditioner according to any one of claims 1 to 4, wherein a global warming potential (GWP) of the heat medium is smaller than that of carbon dioxide.