AIR CONDITIONING APPARATUS

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application of PCT/JP2022/039915 filed Oct. 26, 2022, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an air conditioning apparatus, and particularly, to an air conditioning apparatus including an outdoor unit, a plurality of indoor units, and a branch unit.

BACKGROUND

A conventionally-known air conditioning apparatus includes an outdoor unit, a plurality of indoor units, and a branch unit, in which the outdoor unit is connected to the plurality of indoor units via the branch unit.

WO 2009/133640 A1 discloses such an air conditioning apparatus, in which the outdoor unit is connected to the branch unit via a first extension pipe and a second extension pipe, and the branch unit is connected to the indoor unit via a third extension pipe and a fourth extension pipe. The air conditioning apparatus includes an intermediate heat exchanger disposed in the branch unit.

In the air conditioning system described above, heat transfer is performed by circulating refrigerant through the first third extension pipe and the second extension pipe in the outdoor unit and the branch unit, and heat transfer is performed by circulating water or antifreeze through the third extension pipe and the fourth extension pipe in the branch unit and the indoor unit. The intermediate heat exchanger included in the branch unit performs heat exchange between the refrigerant and the water or antifreeze to transfer heat from the indoor unit to the outdoor unit via the intermediate heat exchanger in the branch unit during a cooling operation and transfer heat from the outdoor unit to the indoor unit via the intermediate heat exchanger in the branch unit during a heating operation.

In the air conditioning apparatus described above, two pipes can be used for connection between the outdoor unit and the branch unit and for connection between the branch unit and the indoor unit, thus reducing the cost of piping materials and the man-hours of work.

PATENT LITERATURE

• • PTL 1: WO 2009/133640 A1

SUMMARY

In the air conditioning system described above, however, the amount of filled refrigerant in the air conditioning apparatus may increase when the first extension pipe and the second extension pipe between the outdoor unit and the branch unit are installed over a long distance (e.g., 110 meters). The refrigerant has a global warming potential (GWP) higher than that of a heat medium such as water and antifreeze, and accordingly, the impact of the air conditioning apparatus on global warming increases as the amount of filled refrigerant increases. In addition, the refrigerant may be costly and have a high risk of combustion in the event of leakage compared to the heat medium such as water and the antifreeze. For these reasons, air conditioning apparatuses with a lower total amount of filled refrigerant are in demand in the market and society.

A main object of the present invention is to provide an air conditioning apparatus that can have a reduced amount of filled refrigerant compared to the convention air conditioning apparatus described above.

An air conditioning apparatus according to the present disclosure includes: an outdoor unit, a plurality of indoor units, and a branch unit; a refrigerant circuit through which refrigerant circulates; and a heat medium circuit through which a heat medium having a global warming potential (GWP) lower than that of the refrigerant circulates. The refrigerant circuit is disposed in the branch unit, has a compressor, a first heat exchanger, an expansion valve, and a second heat exchanger, and is provided such that the refrigerant circulates through the compressor, the first heat exchanger, the expansion valve, and the second heat exchanger in order. The heat medium circuit has a first pump, a second pump, the first heat exchanger, the second heat exchanger, a first branch header, a second branch header, a first merge header, a second merge 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 disposed in the branch 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 branch unit to the outdoor unit, and a plurality of supply branch pipes and a plurality of return branch pipes connecting the branch unit to respective ones of the plurality of indoor units. A first end of each of the plurality of supply branch pipes is connected to the first branch header via a corresponding one of the plurality of first on-off valves and is connected to the second branch header via a corresponding one of the plurality of second on-off valves. A second end of each of the plurality of supply branch pipes is connected to a first end of the indoor heat exchanger of a corresponding one of the plurality of indoor units. A first end of each of the plurality of return branch pipes is connected to the first merge header via a corresponding one of the plurality of third on-off valves and is connected to the second merge header via a corresponding one of the plurality of fourth on-off valves. A second end of each of the plurality of return branch pipes is connected to a second end of the indoor heat exchanger of a corresponding one of the plurality of indoor units. The first branch header is connected to the first merge header via the fifth on-off valve. The second branch header is connected to the second merge header via the sixth on-off valve. In the branch unit, the first merge header, the first pump, the first heat exchanger, and the first branch header are connected in order. In the branch unit, the second merge header, the second pump, the second heat exchanger, and the second branch header are connected in order. A first end of the supply main pipe is connected to the first merge header via the seventh on-off valve and is connected to the second merge header via the eighth on-off valve. A second end of the supply main pipe is connected to a first end of the outdoor heat exchanger of the outdoor unit. A first end of the return main pipe is connected to the first pump via the ninth on-off valve and is connected to the second pump via the tenth on-off valve. A second end of the return main pipe is connected to a second end of the outdoor heat exchanger of the outdoor unit.

According to the present invention, an air conditioning apparatus can be provided that can have a reduced amount of filled refrigerant compared to the conventional air conditioning apparatus described above.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an air conditioning apparatus according to Embodiment 1.

FIG. 2 shows a refrigerant circuit and a heat medium circuit when the air conditioning apparatus shown in FIG. 1 is during a cooling-only operation.

FIG. 3 shows the refrigerant circuit and the heat medium circuit when the air conditioning apparatus shown in FIG. 1 is during a cooling-led operation.

FIG. 4 shows the refrigerant circuit and the heat medium circuit when the air conditioning apparatus shown in FIG. 1 is during a heating-only operation.

FIG. 5 shows the refrigerant circuit and the heat medium circuit when the air conditioning apparatus shown in FIG. 1 is during a heating-led operation.

FIG. 6 shows the refrigerant circuit and the heat medium circuit when the air conditioning apparatus shown in FIG. 1 is during a low-outside-air cooling operation.

FIG. 7 shows an air conditioning apparatus according to Embodiment 2.

FIG. 8 shows an air conditioning apparatus according to Embodiment 3.

FIG. 9 shows an air conditioning apparatus according to Embodiment 4.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described below with reference to the drawings. In the following drawings, the same or corresponding portions are denoted by the same reference numerals, and description thereof will not be repeated. In addition, the vertical and horizontal positional relationships of components in each figure do not limit the physical positional relationships of the components.

Embodiment 1

Configuration of Air Conditioning Apparatus

As shown in FIG. 1, an air conditioning apparatus 100 according to Embodiment 1 includes a branch unit 10, an outdoor unit 40, and a plurality of indoor units 50a, 50b, 50c. Air conditioning apparatus 100 shown in FIG. 1 includes three indoor units 50a, 50b, 50c, but the number of indoor units may be any number of two or more.

Branch unit 10 includes a refrigerant circuit through which refrigerant circulates. Branch unit 10, outdoor unit 40, and the plurality of indoor units 50a, 50b, 50c include a heat medium circuit through which a heat medium having a global warming potential (GWP) lower than that of the refrigerant circulates. The heat medium having a global warming potential (GWP) lower than that of the refrigerant is, for example, water or antifreeze. The refrigerant circuit is included only in branch unit 10. The refrigerant circuit is not included in outdoor unit 40 or the plurality of indoor units 50a, 50b, 50c.

The refrigerant circuit has a compressor 31, a first heat exchanger 12, an expansion valve, and a second heat exchanger 22. Compressor 31, first heat exchanger 12, the expansion valve, and second heat exchanger 22 are disposed in branch unit 10. The refrigerant circuit is provided such that the refrigerant circulates through compressor 31, first heat exchanger 12, the expansion valve, and second heat exchanger 22 in order. The refrigerant circulating through the refrigerant circuit condenses by exchanging heat with the heat medium circulating through the heat medium circuit in first heat exchanger 12, and evaporates by exchanging heat with the heat medium circulating through the heat medium circuit in second heat exchanger 22.

The heat medium circuit has first pump 11, first heat exchanger 12, a first branch header 13, a first merge header 16, a second pump 21, a second heat exchanger 22, a second branch header 23, a second merge 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 in branch unit 10.

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

The heat medium circuit further has a supply main pipe 41 and a return main pipe 42 connecting branch unit 10 to outdoor unit 40, and a plurality of supply branch pipes 51a, 51b, 51c and a plurality of return branch pipes 52a, 52b, 52c connecting branch unit 10 to the plurality of indoor units 50a, 50b, 50c, respectively.

In branch unit 10, first merge header 16, first pump 11, first heat exchanger 12, and first branch header 13 are connected in series via a pipe in the stated order. First merge header 16, first pump 11, first heat exchanger 12, first branch header 13, and the plurality of pipes connecting these in series constitute a first pipe route.

In branch unit 10, second merge header 26, second pump 21, second heat exchanger 22, and second branch header 23 are connected in series via a pipe in the stated order. Second merge header 26, second pump 21, second heat exchanger 22, second branch header 23, and the plurality of pipes connecting these in series constitute a second pipe route.

Each of the first pipe route and the second pipe route is connected to outdoor heat exchanger 43 via supply main pipe 41 and return main pipe 42, and is connected to each of the plurality of indoor heat exchangers 53a, 53b, 53c via a corresponding one of the plurality of supply branch pipes 51a, 51b, 51c and a corresponding one of the plurality of return branch pipes 52a, 52b, 52c. Outdoor heat exchanger 43 and each of the plurality of indoor heat exchangers 53a, 53b, 53c are connected in parallel to each other with respect to the first pipe route, and are also connected in parallel to each other with respect to the second pipe route.

The heat medium circuit further has, in branch unit 10, a plurality of third pipe routes respectively connecting first branch header 13 of the first pipe route to the plurality of supply branch pipes 51a, 51b, 51c, a plurality of fourth pipe routes respectively connecting second branch header 23 of the second pipe route to the plurality of supply branch pipes 51a, 51b, 51c, a plurality of fifth pipe routes respectively connecting first merge header 16 of the first pipe route to the plurality of return branch pipes 52a, 52b, 52c, and a plurality of sixth pipe routes respectively connecting second merge header 26 of the second pipe route to the plurality of return branch pipes 52a, 52b, 52c.

Each of the plurality of first on-off valves 14a, 14b, 14c opens and closes the third pipe route. Each of the plurality of second on-off valves 24a, 24b, 24c opens and closes the fourth pipe route. Each of the plurality of third on-off valves 15a, 15b, 15c opens and closes the fifth pipe route. Each of the plurality of fourth on-off valves 25a, 25b, 25c opens and closes the sixth pipe route.

In other words, a first end of each of the plurality of supply branch pipes 51a, 51b, 51c is connected to first branch header 13 via a corresponding one of the plurality of first on-off valves 14a, 14b, 14c, and is connected to second branch header 23 via a corresponding one of the plurality of second on-off valves 24a, 24b, 24c. A second end of each of the plurality of supply branch pipes 51a, 51b, 51c is connected to a first end of a corresponding one of indoor heat exchangers 53a, 53b, 53c of the plurality of indoor units 50a, 50b, 50c. The first end of each of the plurality of return branch pipes 52a, 52b, 52c is connected to first merge header 16 via a corresponding one of the plurality of third on-off valves 15a, 15b, 15c, and is connected to second merge header 26 via a corresponding one of the plurality of fourth on-off valves 25a, 25b, 25c. A second end of each of the plurality of return branch pipes 52a, 52b, 52c is connected to a second end of a corresponding one of indoor heat exchangers 53a, 53b, 53c of the plurality of indoor units 50a, 50b, 50c.

A pair of the third pipe route and the fourth pipe route connected to one supply branch pipe 51 have, for example, a common part and a non-common part branched off from the common part. A pair of the fifth pipe route and the sixth pipe route connected to one return branch pipe 52 have, for example, a common part and a non-common part branched off from the common part. In this case, each of the plurality of first on-off valves 14a, 14b, 14c opens and closes the above-described non-common part of its corresponding third pipe route, and each of the plurality of second on-off valves 24a, 24b, 24c opens and closes the above-described non-common part of its corresponding fourth pipe route. Each of the plurality of third on-off valves 15a, 15b, 15c opens and closes the above-described non-common part of its corresponding fifth pipe route, and each of the plurality of fourth on-off valves 25a, 25b, 25c opens and closes the above-described non-common part of its corresponding sixth pipe route.

The heat medium circuit further has, in branch unit 10, a first bypass route connecting first branch header 13 and first merge header 16 of the first pipe route to each other, and a second bypass route connecting second branch header 23 and second merge header 26 of the second pipe route to each other. The first bypass route bypasses the plurality of supply branch pipes 51a, 51b, 51c, the plurality of indoor heat exchangers 53a, 53b, 53c, and the plurality of return branch pipes 52a, 52b, 52c, and connects first branch header 13 to first merge header 16. The second bypass route bypasses the plurality of supply branch pipes 51a, 51b, 51c, the plurality of indoor heat exchangers 53a, 53b, 53c, and the plurality of return branch pipes 52a, 52b, 52c, and connects second branch header 23 to second merge header 26.

Fifth on-off valve 17 opens and closes the first bypass route. Sixth on-off valve 27 opens and closes the second bypass route. In other words, first branch header 13 is connected to first merge header 16 via fifth on-off valve 17. Second branch header 23 is connected to second merge header 26 via sixth on-off valve 27.

The heat medium circuit further has, in branch unit 10, a seventh pipe route connecting first merge header 16 of the first pipe route to supply main pipe 41, an eighth pipe route connecting second merge header 26 of the second pipe route to supply main pipe 41, a ninth pipe route connecting return main pipe 42 to first pump 11 of the first pipe route, and a tenth pipe route connecting return main pipe 42 to second pump 21 of the second pipe route.

Seventh on-off valve 33 opens and closes the seventh pipe route. Eighth on-off valve 34 opens and closes the eighth pipe route. Ninth on-off valve 35 opens and closes the ninth pipe route. Tenth on-off valve 36 opens and closes the tenth pipe route.

The seventh pipe route is connected to the part in first merge header 16 which is located downstream of the point of connection between first merge header 16 and each of the plurality of fifth pipe routes, as viewed from first pump 11. The eighth pipe route is connected to the part in second merge header 26 which is located downstream of a point connection between second merge header 26 and each of the plurality of sixth pipe routes, as viewed from second pump 21.

The seventh pipe route and the eighth pipe route have, for example, a common part and a non-common part branched off from the common part. The ninth pipe route and the tenth pipe route have, for example, a common part and a non-common part branched off from the common part. In this case, seventh on-off valve 33 opens and closes the above-described non-common part of the seventh pipe route, and eighth on-off valve 34 opens and closes the above-described non-common part of the eighth pipe route. Ninth on-off valve 35 opens and closes the above-described non-common part of the ninth pipe route, and tenth on-off valve 36 opens and closes the above-described non-common part of the tenth pipe route.

In other words, a first end of supply main pipe 41 is connected to first merge header 16 of the first pipe route via seventh on-off valve 33, and is connected to second merge header 26 of the second pipe route via the eighth on-off valve. A second end of supply main pipe 41 is connected to a first end of outdoor heat exchanger 43 of outdoor unit 40.

A first end of return main pipe 42 is connected to first pump 11 of the first pipe route via ninth on-off valve 35, and is connected to second pump 21 of the second pipe route via tenth on-off valve 36. A second end of return main pipe 42 is connected to a second end of outdoor heat exchanger 43 of outdoor unit 40.

The heat medium circuit further has, in branch unit 10, a third bypass route connecting the seventh pipe route to the ninth pipe route, a fourth bypass route connecting the eighth pipe route to the tenth pipe route, an eleventh on-off valve 18 that opens and closes the third bypass route, and a twelfth on-off valve 28 that opens and closes the fourth bypass route.

From a different perspective, the first pipe route has a pipe 19 connecting first merge header 16 to first pump 11. Each of the seventh pipe route connecting first merge header 16 to supply main pipe 41 and the ninth pipe route connecting return main pipe 42 to first pump 11 of the first pipe route is connected to pipe 19. A point of connection C between pipe 19 and the ninth pipe route is disposed downstream of a point of connection A between pipe 19 and the seventh pipe route, as viewed from first pump 11. Eleventh on-off valve 18 opens and closes pipe 19.

The second pipe route has a pipe 29 connecting second merge header 26 to second pump 21. Each of the eighth pipe route connecting second merge header 26 to supply main pipe 41 and the tenth pipe route connecting return main pipe 42 to second pump 21 of the second pipe route is connected to pipe 29. A point of connection D between pipe 29 and the tenth pipe route is disposed downstream of a point of connection B between pipe 29 and the eighth pipe route, as viewed from second pump 21. Twelfth on-off valve 28 opens and closes pipe 29.

Each on-off valve described above is, for example, a solenoid valve.

In air conditioning apparatus 100, the magnitude relationship between the minimum value of the inner diameter of each of supply main pipe 41 and return main pipe 42 and the maximum value of the inner diameter of each of the plurality of supply branch pipes 51a, 51b, 51c and the plurality of return branch pipes 52a, 52b, 52c is not particularly limited. For example, the minimum value of the inner diameter of each of supply main pipe 41 and return main pipe 42 may be equal to the maximum value of the inner diameter of each of the plurality of supply branch pipes 51a, 51b, 51c and the plurality of return branch pipes 52a, 52b, 52c.

Operation of Air Conditioning Apparatus

Air conditioning apparatus 100 performs a cooling-only operation shown in FIG. 2, a cooling-led operation shown in FIG. 3, a heating-only operation shown in FIG. 4, a heating-led operation shown in FIG. 5, or a low-outside-air cooling operation shown in FIG. 6, depending on the operation mode of each of the plurality of indoor units 50a, 50b, 50c and the temperature of outside air taken in by outdoor unit 40. In FIGS. 2 to 6, the on-off valves painted in black indicate the on-off valves that are closed.

When all the indoor units in operation are in the cooling operation mode, air conditioning apparatus 100 performs the cooling-only operation. When all the indoor units in operation are in the heating operation mode, air conditioning apparatus 100 performs the heating-only operation. When some of the indoor units in operation are in the cooling operation mode and the other indoor units are in the heating operation mode, air conditioning apparatus 100 performs the cooling-led operation if the total air conditioning load of the indoor units in the cooling operation mode is greater than the total air conditioning load of the indoor units in the heating operation mode, and air conditioning apparatus 100 performs the heating-led operation if the total air conditioning load of the indoor units in the heating operation mode is greater than the total air conditioning load of the indoor units in the cooling operation mode. When all the indoor units in operation are in the cooling operation mode and the outside air temperature is sufficiently lower than the indoor temperature (e.g., the outside air temperature is 5° C. or lower), air conditioning apparatus 100 performs the low-outside-air cooling operation.

When air conditioning apparatus 100 is in each operating state, at least any one of a hot water circuit in which a heat medium heated by exchanging heat with refrigerant in first heat exchanger 12 circulates, and a cold water circuit which includes the second pipe route and in which a heat medium cooled by exchanging heat with refrigerant in second heat exchanger 22 circulates is formed in the heat medium circuit. More specifically, when air conditioning apparatus 100 is in each operating state, the on-off valves included in the heat medium circuit form at least any one of a hot water circuit including first heat exchanger 12 and the indoor heat exchanger of an indoor unit, which is in the heating operation mode, among indoor units 50a, 50b, 50c, and a cold water circuit including second heat exchanger 22 and the indoor heat exchanger of the indoor unit, which is in the cooling operation mode, among indoor units 50a, 50b, 50c.

The refrigeration cycles realized in the refrigerant circuit when air conditioning apparatus 100 is in the respective states of the cooling-only operation, cooling-led operation, heating-only operation, and heating-led operation are mutually equivalent. When air conditioning apparatus 100 is in the respective states of the cooling-only operation, cooling-led operation, heating-only operation, and heating-led operation, in the refrigerant circuit, first heat exchanger 12 acts as a condenser and second heat exchanger 22 acts as an evaporator. Specifically, gas single-phase refrigerant discharged from compressor 31 condenses by exchanging heat with the heat medium circulating through the hot water circuit in first heat exchanger 12, thus turning into liquid single-phase refrigerant. The liquid single-phase refrigerant that has flowed out of first heat exchanger 12 is decompressed to be expanded in expansion valve 32, thus turning into gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant that has flowed out of expansion valve 32 evaporates by exchanging heat with the heat medium circulating through the cold water circuit in second heat exchanger 22, thus turning into gas single-phase refrigerant. The gas single-phase refrigerant that has flowed out of second heat exchanger 22 is suctioned again into compressor 31 and circulates through the refrigerant circuit.

When air conditioning apparatus 100 is during the low-outside-air cooling operation, compressor 31 of the refrigerant circuit is stopped and the refrigeration cycle is not realized.

Cooling-Only Operation

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

As a result, in this state, in the heat medium circuit, the hot water circuit including first pump 11, first heat exchanger 12, first branch header 13, first merge header 16, supply main pipe 41, outdoor heat exchanger 43, and return main pipe 42, and the cold water circuit including second pump 21, second heat exchanger 22, second branch header 23, the plurality of supply branch pipes 51a, 51b, 51c, the plurality of indoor heat exchangers 53a, 53b, 53c, the plurality of return branch pipes 52a, 52b, 52c, and second merge header 26 are formed simultaneously. In the hot water circuit, first pump 11, first heat exchanger 12, first branch header 13, first merge header 16, supply main pipe 41, outdoor heat exchanger 43, and return main pipe 42 are connected in series in the stated order. In the cold water circuit, second pump 21, second heat exchanger 22, second branch header 23, each of the plurality of supply branch pipes 51a, 51b, 51c, each of the plurality of indoor heat exchangers 53a, 53b, 53c, each of the plurality of return branch pipes 52a, 52b, 52c, and second merge header 26 are connected in series in the stated order. In the cold water circuit, the plurality of indoor heat exchangers 53a, 53b, 53c are connected in parallel to one another with respect to each of second branch header 23 and second merge header 26.

In the hot water circuit, the heat medium that has flowed out of first pump 11 is heated by exchanging heat with the gas single-phase refrigerant in first heat exchanger 12. The heat medium heated in first heat exchanger 12 flows through first branch header 13, fifth on-off valve 17, first merge header 16, seventh on-off valve 33, and supply main pipe 41 into outdoor heat exchanger 43 in outdoor unit 40. During operation of outdoor unit 40, an outdoor blower 44 is in operation, and the heat medium dissipates heat by exchanging heat with the outside air blown by outdoor blower 44 in outdoor heat exchanger 43. The heat medium that has flowed out of outdoor heat exchanger 43 flows through return main pipe 42 and ninth on-off valve 35 into first pump 11, and circulates through the hot water circuit again.

In the cold water circuit, the heat medium that has flowed out of second pump 21 is cooled by exchanging heat with the gas-liquid two-phase refrigerant in second heat exchanger 22. The heat medium cooled in second heat exchanger 22 flows through second branch header 23, each of second on-off valves 24a, 24b, 24c, and each of supply branch pipes 51a, 51b, 51c into a corresponding one of indoor heat exchangers 53a, 53b, 53c. During operation of each of indoor units 50a, 50b, 50c, a corresponding one of indoor blowers 54a, 54b, 54c is in operation, and the heat medium cools the indoor air blown by each of indoor blowers 54a, 54b, 54c in a corresponding one of indoor heat exchangers 53a, 53b, 53c. The heat medium that has flowed out of each of indoor heat exchangers 53a, 53b, 53c flows through a corresponding one of return branch pipes 52a, 52b, 52c and a corresponding one of fourth on-off valves 25a, 25b, 25c into second merge header 26 to be merged in second merge header 26. The heat medium after merging in second merge header 26 flows through twelfth on-off valve 28 into second pump 21 and circulates through the cold water circuit again.

In this state, the cold heat required by each of indoor units 50a, 50b, 50c during the cooling operation is generated by the refrigerant circuit. The cold heat is transferred to the heat medium in the cold water circuit at second heat exchanger 22 and transported by the heat medium to each of indoor heat exchangers 53a, 53b, 53c to cool the indoor air in each of indoor heat exchangers 53a, 53b, 53c. Simultaneously, the hot waste heat generated in the refrigerant circuit is transferred to the heat medium in the hot water circuit at first heat exchanger 12, is transported to outdoor heat exchanger 43 by the heat medium, and is released into the outside air at outdoor heat exchanger 43.

Cooling-Led Operation

In the cooling-led operation shown in FIG. 3, indoor units 50a, 50b are in the cooling operation mode, and indoor unit 50c is in the heating operation mode. In this state, first on-off valve 14c, third on-off valve 15c, fifth on-off valve 17, second on-off valves 24a, 24b, fourth on-off valves 25a, 25b, twelfth on-off valve 28, seventh on-off valve 33, and ninth on-off valve 35 are opened, and first on-off valves 14a, 14b, third on-off valves 15a, 15b, eleventh on-off valve 18, second on-off valve 24c, fourth on-off valve 25c, sixth on-off valve 27, eighth on-off valve 34, and tenth on-off valve 36 are closed.

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

In the hot water circuit, first pump 11, first heat exchanger 12, first branch header 13, supply branch pipe 51c, indoor heat exchanger 53c, return branch pipe 52c, and first merge header 16 are connected in series in the stated order, and simultaneously, first pump 11, first heat exchanger 12, first branch header 13, first merge header 16, supply main pipe 41, outdoor heat exchanger 43, and return main pipe 42 are connected in series in the stated order. In the hot water circuit, indoor heat exchanger 53c and outdoor heat exchanger 43 are connected in series with each other via first merge header 16 while being connected in parallel to each other with respect to first branch header 13. Outdoor heat exchanger 43 is disposed downstream of indoor heat exchanger 53c as viewed from first pump 11.

In the cold water circuit, second pump 21, second heat exchanger 22, second branch header 23, each of supply branch pipes 51a, 51b, each of indoor heat exchangers 53a, 53b, each of return branch pipes 52a, 52b, and second merge header 26 are connected in series in the stated order.

In the hot water circuit, the heat medium that has flowed out of first pump 11 is heated by exchanging heat with the gas single-phase refrigerant in first heat exchanger 12. A portion of the heat medium heated in first heat exchanger 12 flows through first branch header 13, first on-off valve 14c, and supply branch pipe 51c into indoor heat exchanger 53c, and heats the indoor air blown by indoor blower 54c in indoor heat exchanger 53c. The heat medium that has flowed out of indoor heat exchanger 53c flows through return branch pipe 52c and third on-off valve 15c into first merge header 16, and in first merge header 16, merges with the remaining portion of the heat medium heated in first heat exchanger 12. The heat medium after merging in first merge header 16 flows through seventh on-off valve 33 and supply main pipe 41 into outdoor heat exchanger 43 in outdoor unit 40, and in outdoor heat exchanger 43, dissipates heat by exchanging heat with the outside air blown by outdoor blower 44. The heat medium that has flowed out of outdoor heat exchanger 43 flows through return main pipe 42 and ninth on-off valve 35 into first pump 11, and circulates through the hot water circuit again.

In the cold water circuit, the heat medium that has flowed out of second pump 21 is cooled by exchanging heat with the gas-liquid two-phase refrigerant in second heat exchanger 22, and flows through second branch header 23, each of second on-off valves 24a, 24b, and each of branch pipes 51a, 51b into a corresponding one of indoor heat exchangers 53a, 53b, and cools the indoor air blown by each of indoor blowers 54a, 54b in a corresponding one of indoor heat exchangers 53a, 53b. The heat medium that has flowed out of each of indoor heat exchangers 53a, 53b flows through a corresponding one of return branch pipes 52a, 52b and a corresponding one of fourth on-off valves 25a, 25b into second merge header 26 to be merged in second merge header 26. The heat medium after merging in second merge header 26 flows through twelfth on-off valve 28 into second pump 21 and circulates through the cold water circuit again.

In this state, the cold heat required by each of indoor units 50a, 50b during the cooling operation is generated in the refrigerant circuit, and the hot heat required by indoor unit 50c during the heating operation is generated in the refrigerant circuit. The above-described cold heat is transferred to the heat medium of the cold water circuit at second heat exchanger 22 and transported to each of indoor heat exchangers 53a, 53b by the heat medium to cool the indoor air in each of indoor heat exchangers 53a, 53b. Simultaneously, the above-described hot heat is transferred to the heat medium in the hot water circuit at first heat exchanger 12 and transported to indoor heat exchanger 53c by the heat medium to heat the indoor air in indoor heat exchanger 53c. The hot waste heat generated in each of the refrigerant circuit and the hot water circuit is transported to outdoor heat exchanger 43 by the heat medium in the hot water circuit and is released into the outside air at outdoor heat exchanger 43.

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

Heating-Only Operation

As shown in FIG. 4, during the heating-only operation of air conditioning apparatus 100, first on-off valves 14a, 14b, 14c, the plurality of third on-off valves 15a, 15b, 15c, eleventh on-off valve 18, sixth on-off valve 27, eighth on-off valve 34, and 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, fifth on-off valve 17, twelfth on-off valve 28, seventh on-off valve 33, and ninth on-off valve 35 are closed.

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

In the hot water circuit, first pump 11, first heat exchanger 12, first branch header 13, each of the plurality of supply branch pipes 51a, 51b, 51c, each of the plurality of indoor heat exchangers 53a, 53b, 53c, each of the plurality of return branch pipes 52a, 52b, 52c, and first merge header 16 are connected in series in the stated order. In the cold water circuit, second pump 21, second heat exchanger 22, second branch header 23, second merge header 26, supply main pipe 41, outdoor heat exchanger 43, and return main pipe 42 are connected in series in the stated order. In the hot water circuit, the plurality of indoor heat exchangers 53a, 53b, 53c are connected in parallel to one another with respect to each of second branch header 23 and second merge header 26.

In the hot water circuit, the heat medium that has flowed out of first pump 11 is heated by exchanging heat with the gas single-phase refrigerant in first heat exchanger 12. The heat medium heated in first heat exchanger 12 flows through first branch header 13, each of first on-off valves 14a, 14b, 14c, and each of supply branch pipes 51a, 51b, 51c into a corresponding one of indoor heat exchangers 53a, 53b, 53c. During operation of each of indoor units 50a, 50b, 50c, a corresponding one of indoor blowers 54a, 54b, 54c is operating, and the heat medium heats the indoor air blown by each of indoor blowers 54a, 54b, 54c in a corresponding one of indoor heat exchangers 53a, 53b, 53c. The heat medium that has flowed out of each of indoor heat exchangers 53a, 53b, 53c flows through a corresponding one of return branch pipes 52a, 52b, 52c and a corresponding one of fourth on-off valves 25a, 25b, 25c into first merge header 16 to be merged. The heat medium after merging in first merge header 16 flows through eleventh on-off valve 18 into first pump 11 and circulates through the hot water circuit again.

In the cold water circuit, the heat medium that has flowed out of second pump 21 is cooled by exchanging heat with the gas-liquid two-phase refrigerant in second heat exchanger 22. The heat medium cooled in second heat exchanger 22 flows through second branch header 23, sixth on-off valve 27, second merge header 26, eighth on-off valve 34, and supply main pipe 41 into outdoor heat exchanger 43. The heat medium absorbs heat from the outdoor air blown by outdoor blower 44 in outdoor heat exchanger 43. The heat medium that has flowed out of outdoor heat exchanger 43 flows through return main pipe 42 and tenth on-off valve 36 into second pump 21, and circulates through the cold water circuit again.

In this state, the hot heat required by each of indoor units 50a, 50b, 50c during the heating operation is generated in the refrigerant circuit. This hot heat is transferred to the heat medium in the hot water circuit at first heat exchanger 12 and transported by the heat medium to each of indoor heat exchangers 53a, 53b, 53c to heat the indoor air in each of indoor heat exchangers 53a, 53b, 53c. Simultaneously, the cold waste heat generated in the refrigerant circuit is transferred to the heat medium in the cold water circuit at second heat exchanger 22 and transported to outdoor heat exchanger 43 by the heat medium and is released into the outside air at outdoor heat exchanger 43.

Heating-Led Operation

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

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

In the hot water circuit, first pump 11, first heat exchanger 12, first branch header 13, each of supply branch pipes 51a, 51b, each of indoor heat exchangers 53a, 53b, each of return branch pipes 52a, 52b, and first merge header 16 are connected in series.

In the cold water circuit, second pump 21, second heat exchanger 22, second branch header 23, supply branch pipe 51c, indoor heat exchanger 53c, return branch pipe 52c, and second merge header 26 are connected in series in the stated order, and simultaneously, second pump 21, second heat exchanger 22, second branch header 23, second merge header 26, supply main pipe 41, outdoor heat exchanger 43, and return main pipe 42 are connected in series in the stated order. In the cold water circuit, indoor heat exchanger 53c and outdoor heat exchanger 43 are connected in series with each other via second merge header 26 while being connected in parallel to each other with respect to second branch header 23. Outdoor heat exchanger 43 is disposed downstream of indoor heat exchanger 53c as viewed from second pump 21.

In the hot water circuit, the heat medium that has flowed out of first pump 11 is heated by exchanging heat with the gas single-phase refrigerant in first heat exchanger 12, and flows through first branch header 13, each of first on-off valves 14a, 14b, and each of supply branch pipes 51a, 51b into a corresponding one of indoor heat exchangers 53a, 53b to heat the indoor air blown by each of indoor blowers 54a, 54b in a corresponding one of indoor heat exchangers 53a, 53b. The heat medium that has flowed out of each of indoor heat exchangers 53a, 53b flows through a corresponding one of return branch pipes 52a, 52b and a corresponding one of third on-off valves 15a, 15b into first merge header 16 to be merged in first merge header 16. The heat medium after merging in first merge header 16 flows through eleventh on-off valve 18 into first pump 11 and circulates through the hot water circuit again.

In the cold water circuit, the heat medium that has flowed out of second pump 21 is cooled by exchanging heat with the gas-liquid two-phase refrigerant in second heat exchanger 22. A portion of the heat medium cooled in second heat exchanger 22 flows through second branch header 23, second on-off valve 24c, and supply branch pipe 51c into indoor heat exchanger 53c, and cools the indoor air blown by indoor blower 54c in indoor heat exchanger 53c. The heat medium that has flowed out of indoor heat exchanger 53c flows through return branch pipe 52c and fourth on-off valve 25c into second merge header 26 to be merged with the remaining portion of the heat medium cooled in second heat exchanger 22 at second merge header 26. The heat medium that has been merged in second merge header 26 flows through eighth on-off valve 34 and supply main pipe 41 into outdoor heat exchanger 43 in outdoor unit 40, and absorbs heat by exchanging heat with the outside air blown by outdoor blower 44 in outdoor heat exchanger 43. The heat medium that has flowed out of outdoor heat exchanger 43 flows through return main pipe 42 and tenth on-off valve 36 into second pump 21 and circulates through the cold water circuit again.

In this state, the hot heat required by each of indoor units 50a, 50b during the heating operation is generated in the refrigerant circuit, and the cold heat required by indoor unit 50c during the cooling operation is generated in the refrigerant circuit. The above-described hot heat is transferred to the heat medium in the hot water circuit at first heat exchanger 12 and transported to each of indoor heat exchangers 53a, 53b by the heat medium to heat the indoor air in each of indoor heat exchangers 53a, 53b. The above-described cold heat is transferred to the heat medium in the cold water circuit at second heat exchanger 22 and transported to indoor heat exchanger 53c by the heat medium to cool the indoor air at indoor heat exchanger 53c. The cold waste heat generated in each of the refrigerant circuit and the hot water circuit is transported to outdoor heat exchanger 43 by the heat medium in the cold water circuit and is released into the outside air at outdoor heat exchanger 43.

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

Low-Outside-Air Cooling Operation

As shown in FIG. 6, during the low-outside-air cooling operation of air conditioning apparatus 100, the plurality of second on-off valves 24a, 24b, 24c, the plurality of fourth on-off valves 25a, 25b, 25c, eighth on-off valve 34, and tenth on-off valve 36 are opened, and first on-off valves 14a, 14b, 14c, the plurality of third on-off valves 15a, 15b, 15c, fifth on-off valve 17, sixth on-off valve 27, eleventh on-off valve 18, twelfth on-off valve 28, seventh on-off valve 33, and ninth on-off valve 35 are closed.

In addition, in this state, compressor 31 of the refrigerant circuit is stopped, and the refrigeration cycle is not realized. Thus, first heat exchanger 12 does not act as a hot heat source. Similarly, second heat exchanger 22 does not act as a cold heat source.

In this state, only the cold water circuit is formed in the heat medium circuit. The cold water circuit includes second pump 21, second heat exchanger 22, second branch header 23, each of the plurality of supply branch pipes 51a, 51b, 51c, each of the plurality of indoor heat exchangers 53a, 53b, 53c, each of the plurality of return branch pipes 52a, 52b, 52c, second merge header 26, eighth on-off valve 34, supply main pipe 41, outdoor heat exchanger 43, return main pipe 42, and tenth on-off valve 36. In the cold water circuit, second pump 21, second heat exchanger 22, second branch header 23, each of the plurality of supply branch pipes 51a, 51b, 51c, each of the plurality of indoor heat exchangers 53a, 53b, 53c, each of the plurality of return branch pipes 52a, 52b, 52c, second merge header 26, supply main pipe 41, outdoor heat exchanger 43, and return main pipe 42 are connected in series in the stated order. In the cold water circuit, the plurality of indoor heat exchangers 53a, 53b, 53c are connected in parallel to one another with respect to each of second branch header 23 and second merge header 26. Outdoor heat exchanger 43 is connected in series with each of the plurality of indoor heat exchangers 53a, 53b, 53c. Outdoor heat exchanger 43 is disposed downstream of indoor heat exchanger 53c as viewed from second pump 21.

In the cold water circuit, the heat medium that has flowed out of second pump 21 flows through second heat exchanger 22 and then flows through second branch header 23 and each of second on-off valves 24a, 24b, 24c into a corresponding one of indoor heat exchangers 53a, 53b, 53c. The heat medium cools the indoor air blown by each of indoor blowers 54a, 54b, 54c in a corresponding one of indoor heat exchangers 53a, 53b, 53c. The heat medium that has flowed out of each of indoor blowers 54a, 54b, 54c flows through fourth on-off valve 25, second merge header 26, and eighth on-off valve 34 into outdoor heat exchanger 43. The heat medium is cooled by the outside air blown by outdoor blower 44 in outdoor heat exchanger 43. The heat medium that has flowed out of outdoor heat exchanger 43 flows through tenth on-off valve 36 into second pump 21 and circulates through the cold water circuit.

In this state, the cold heat required by each of indoor units 50a, 50b, 50c during the cooling operation is all covered by heat absorption from the outside air having a temperature lower than the indoor temperature and by cold heat transfer by the cold water circuit. In this state, compressor 31 of the refrigeration cycle is stopped, and low-temperature outdoor air can be used directly as a cold heat source, resulting in lower power consumption than in the cooling-only operation state.

When the flow rate (circulating flow rate) of the heat medium circulating through the heat medium circuit during operation of second pump 21 is low, or when the power consumption during operation of second pump 21 is high, first pump 11 may be operated, seventh on-off valve 33 and ninth on-off valve 35 may be opened, and second on-off valve 24 and fourth on-off valve 25 corresponding to indoor unit 50 during the cooling operation may be stopped, and first on-off valve 14 and third on-off valve 15 corresponding to this indoor unit 50 may be opened. Consequently, a cold water circuit including second pump 21 and a cold water circuit including first pump 11 can be formed simultaneously in the heat medium circuit, thus maximizing the total value of the circulating flow rates of second pump 21 and first pump 11 or minimizing the total value of the power consumption of second pump 21 and first pump 11.

Functions and Effects

In air conditioning apparatus 100, only branch unit 10 has a refrigerant circuit, and heat transport between branch unit 10 and outdoor unit 40 and between branch unit 10 and each of indoor units 50a, 50b, 50c is performed by a heat medium. Thus, in air conditioning apparatus 100, the amount of filled refrigerant in air conditioning apparatus 100 can be reduced compared to the above-described conventional air conditioning apparatus regardless of the length of each of supply main pipe 41 and return main pipe 42 connecting branch unit 10 to outdoor unit 40, and the plurality of supply branch pipes 51a, 51b, 51c and the plurality of return branch pipes 52a, 52b, 52c connecting branch unit 10 to the respective indoor units 50a, 50b, 50c.

In addition, in general, the internal pressure of the pipe (e.g., a water pipe through which water flows) of the heat medium circuit is lower than the internal pressure of the refrigerant pipe of the refrigerant circuit. For example, the internal pressure of the refrigerant pipe is as high as a maximum of about 4 megapascals, whereas the internal pressure of the water pipe is less than 1 megapascal at a maximum. Thus, the pipe of the heat medium circuit can be easily installed compared to the refrigerant pipe, and accordingly, air conditioning apparatus 100 can be easily installed compared to a conventional air conditioning apparatus in which heat transfer between the branch unit and the outdoor unit, each indoor unit is performed by refrigerant. In addition, in air conditioning apparatus 100, the risk of refrigerant leakage is reduced compared to the conventional air conditioning apparatus.

Also, if the heat medium leaks from the heat medium circuit of air conditioning apparatus 100, the impact on global warming is smaller than when the refrigerant leaks in a conventional air conditioning apparatus because the global warming potential (GWP) of the heat medium is lower than that of carbon dioxide.

Further, in air conditioning apparatus 100, two pipes are used for connection between branch unit 10 and outdoor unit 40 and for connection between branch unit 10 and each indoor unit, and thus, installation can be performed more easily than when three pipes are used for connection between branch unit 10 and outdoor unit 40 and for connection between branch unit 10 and each indoor unit.

Further, in air conditioning apparatus 100, switch can be made between the cooling-only operation, the cooling-led operation, the heating-only operation, and the heating-led operation in accordance with the operation mode of each of the plurality of indoor units 50a, 50b, 50c, using the hot heat and cold heat generated by the refrigeration cycle realized in the refrigerant circuit included in branch unit 10. For example, in the air conditioning facility of a large building, when the operating state of the indoor unit installed in a general room is set to heating, the operating state of the indoor unit installed in a room having a large heat generation amount, such as a computer room or a kitchen, may be set to cooling. Air conditioning apparatus 100 is suitable for such an air conditioning facility.

In addition, in air conditioning apparatus 100, when the outside air temperature is sufficiently lower than the temperature of the room in which the indoor unit during the cooling operation is installed, the low-outside-air cooling operation is performed. During the low-outside-air cooling operation, compressor 31 of the refrigeration cycle is stopped, and low-temperature outdoor air is directly used as a cold heat source, leading to lower power consumption than during the cooling-only operation.

In addition, in air conditioning apparatus 100, in the cooling-led operation, as eleventh on-off valve 18 is closed, the hot waste heat can be supplied to outdoor unit 40 after supply of the hot heat, transferred to the heat medium in first heat exchanger 12, to indoor unit 50c during the heating operation. This can suppress a temperature drop of the heat medium in indoor heat exchanger 53c, and accordingly, the temperature difference between the heat medium in indoor heat exchanger 53c and the indoor air can be maintained, thus preventing a decline in the heating capacity of indoor unit 50 during the heating operation in the cooling-led operation.

Similarly, in the heating-led operation, as twelfth on-off valve 28 is closed, the cold waste heat can be supplied to outdoor unit 40 after supply of the cold heat, transferred to the heat medium in second heat exchanger 22, to indoor unit 50c during the cooling operation. This can suppress a temperature rise of the heat medium in indoor heat exchanger 53c, and accordingly, the temperature difference between the heat medium in indoor heat exchanger 53c and the indoor air can be maintained, thus preventing a decline in the cooling capacity of indoor unit 50 during the cooling operation in the heating-led operation.

As described above, in air conditioning apparatus 100, not only can the amount of filled refrigerant be reduced compared to the conventional refrigeration cycle apparatus described above, but also the difficulty of installation, cost, and risk of refrigerant leakage are low, power consumption is kept low in the low-outside-air cooling operation, a decline in the heating capacity of indoor unit 50 during the heating operation can be prevented in the cooling-led operation, and further, a decline in the cooling capacity of indoor unit 50 during the cooling operation can be prevented in the heating-led operation.

Embodiment 2

As shown in FIG. 7, an air conditioning apparatus 101 according to Embodiment 2 has basically the same configuration and achieves the same effects as those of air conditioning apparatus 100 according to Embodiment 1, but differs from air conditioning apparatus 100 in that the heat medium circuit does not include the third bypass route connecting the seventh pipe route to the ninth pipe route or eleventh on-off valve 18. The following will mainly describe the points in which air conditioning apparatus 101 differs from air conditioning apparatus 100.

In air conditioning apparatus 101, the heat medium circuit does not have, in branch unit 10, the third bypass route connecting the seventh pipe route to the ninth pipe route or eleventh on-off valve 18 that opens and closes the third bypass route. From a different perspective, the first pipe route does not have pipe 19 connecting first merge header 16 to first pump 11.

The heat medium circuit of air conditioning apparatus 101 is the same as the heat medium circuit of air conditioning apparatus 100, except that the state in which the seventh pipe route is connected to the ninth pipe route via the third bypass route cannot be realized. Air conditioning apparatus 101 can perform at least the cooling-only operation, the cooling-led operation, or the low-outside-air cooling operation.

Air conditioning apparatus 101 is suitable for an air conditioning facility 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.

Embodiment 3

As shown in FIG. 8, an air conditioning apparatus 102 according to Embodiment 3 has basically the same configuration and achieves the same effects as those of air conditioning apparatus 100 according to Embodiment 1, but differs from air conditioning apparatus 100 in that the minimum value of the flow path sectional area of each of supply main pipe 41 and return main pipe 42 is greater than the maximum value of the flow path sectional area of each of the plurality of supply branch pipes 51a, 51b, 51c and the plurality of return branch pipes 52a, 52b, 52c. The following will mainly describe the points in which air conditioning apparatus 102 differs from air conditioning apparatus 100. In FIG. 8, the flow paths of the heat medium formed inside supply main pipe 41, return main pipe 42, the plurality of supply branch pipes 51a, 51b, 51c, and the plurality of return branch pipes 52a, 52b, 52c are indicated by the broken lines. The minimum value of the flow path sectional area of each of supply main pipe 41 and return main pipe 42 is greater than the maximum value of the flow path sectional area of each of the plurality of supply branch pipes 51a, 51b, 51c and the plurality of return branch pipes 52a, 52b, 52c. Each of supply main pipe 41, return main pipe 42, the plurality of supply 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 supply main pipe 41 and return main pipe 42 is greater than the maximum value of the inner diameter of each of the plurality of supply branch pipes 51a, 51b, 51c and the plurality of return branch pipes 52a, 52b, 52c.

The flow rate of the heat medium flowing through each of supply main pipe 41 and return main pipe 42 becomes maximum in the cooling-only operation or the heating-only operation among the operations that air conditioning apparatus 102 can perform. In air conditioning apparatus 102, the minimum value of the flow path sectional area of each of supply main pipe 41 and return main pipe 42 is greater than the maximum value of the flow path sectional area of each of the plurality of supply branch pipes 51a, 51b, 51c and the plurality of return branch pipes 52a, 52b, 52c, and accordingly, the flow resistance inside each of supply main pipe 41 and return main pipe 42 can be suppressed.

In addition, because air conditioning apparatus 102 is not designed such that the internal volume of each of the plurality of supply branch pipes 51a, 51b, 51c and the plurality of return branch pipes 52a, 52b, 52c becomes excessively large, the total amount of the heat medium filled in the heat medium circuit (the amount of filled heat medium) of air conditioning apparatus 102 can be reduced. Consequently, in air conditioning apparatus 102, the time required for the air conditioning capacity to be demonstrated at the start of the cooling-only operation, cooling-led operation, heating-only operation, heating-led operation, or low-outside-air cooling operation can be reduced, improving the air conditioning capacity to follow the air conditioning load.

In addition, air conditioning apparatus 102 according to Embodiment 3 may have a configuration similar to that of air conditioning apparatus 101 according to Embodiment 2, except that the minimum value of the flow path sectional area of each of supply main pipe 41 and return main pipe 42 is greater than the maximum value of the flow path sectional area of each of the plurality of supply branch pipes 51a, 51b, 51c and the plurality of return branch pipes 52a, 52b, 52c.

Embodiment 4

As shown in FIG. 9, an air conditioning apparatus 103 according to Embodiment 4 has basically the same configuration and achieves the same effects as those of air conditioning apparatus 100 according to Embodiment 1, but differs from air conditioning apparatus 100 in that outdoor heat exchanger 43 has a first heat exchange unit 43a and a second heat exchange unit 43b having a smaller internal volume than that of first heat exchange unit 43a and that the area expansion ratio of second heat exchange unit 43b is smaller than the area expansion ratio of first heat exchange unit 43a. In this specification, 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 can be defined as an area expansion ratio. The following will mainly describe the points in which air conditioning apparatus 103 differs from air conditioning apparatus 100.

First heat exchange unit 43a and second heat exchange unit 43b are connected in parallel to each other with respect to supply main pipe 41 and return main pipe 42.

In outdoor unit 40, the heat medium circuit has an eleventh pipe route connecting the second end of supply main pipe 41 to a first end of first heat exchange unit 43a, and a twelfth pipe route connecting the second end of supply main pipe 41 to a first end of second heat exchange unit 43b. The eleventh pipe route and the twelfth pipe route have, for example, a common part and a non-common part branched off from the common part. In this case, the heat medium circuit further has, in outdoor unit 40, a thirteenth on-off valve 45a that opens and closes the non-common part of the eleventh pipe route and a fourteenth on-off valve 45b that opens and closes the non-common part of the twelfth pipe route.

In outdoor unit 40, the heat medium circuit further has a thirteenth pipe route connecting a second end of first heat exchange unit 43a to the second end of return main pipe 42, and a fourteenth pipe route connecting a second end of second heat exchange unit 43b to the second end of return main pipe 42. The thirteenth pipe route and the fourteenth pipe route have, for example, a common part and a non-common part branched off from the common part.

For example, the relative positional relationship between the first end of first heat exchange unit 43a, which is connected to the second end of supply main pipe 41, and the second end of first heat exchange unit 43a, which is connected to the above-described second end of return main pipe 42, is equivalent to the relative positional relationship between the first end of second heat exchange unit 43b, which is connected to the second end of supply main pipe 41, and the second end of second heat exchange unit 43b, which is connected to the second end of return main pipe 42.

In each of first heat exchange unit 43a and second heat exchange unit 43b of outdoor heat exchanger 43, for example, one outdoor blower 44 is provided to blow the outdoor air. In addition, first heat exchange unit 43a and second heat exchange unit 43b of outdoor heat exchanger 43 may be respectively provided with different outdoor blowers may be provided to blow the outdoor air.

In air conditioning apparatus 103, outdoor heat exchanger 43 has first heat exchange unit 43a and second heat exchange unit 43b having a smaller internal volume than that of first heat exchange unit 43a, and the area expansion ratio of second heat exchange unit 43b is smaller than the area expansion ratio of first heat exchange unit 43a. Thus, when air conditioning apparatus 103 is performing the low-outside-air cooling operation, the amount of heat dissipated from outdoor heat exchanger 43 to the outdoor air can be suppressed compared to air conditioning apparatus 100, thus suppressing an excessive decrease in the temperature of the heat medium in outdoor heat exchanger 43.

Air conditioning apparatus 103 is particularly suitable for an air conditioning apparatus that uses antifreeze as the heat medium. As the antifreeze has a higher viscosity and a higher flow resistance as its temperature decreases, if the temperature of the antifreeze decreases excessively in outdoor heat exchanger 43, the power consumption of second pump 21 (or second pump 21 and first pump 11 when second pump 21 and first pump 11 are driven simultaneously during the low outside air cooling operation as described above) will increase. In contrast, in air conditioning apparatus 103, even when the heat medium is the antifreeze, an excessive decrease in the temperature of the heating medium can be suppressed in outdoor heat exchanger 43, and thus, an increase in the flow resistance of the antifreeze can be suppressed, thus suppressing an increase in the power consumption of second pump 21.

Preferably, during the low-outside-air cooling operation of air conditioning apparatus 103, thirteenth on-off valve 45a is closed and fourteenth on-off valve 45b is opened. In this case, during the low-outside-air cooling operation, the heat medium flows only into second heat exchange unit 43b, which has a relatively small internal volume, of outdoor heat exchanger 43. As a result, during the low-outside-air cooling operation of air conditioning apparatus 103, thirteenth on-off valve 45a is closed and fourteenth on-off valve 45b is open, and thus, an excessive decrease in the temperature of the antifreeze can be suppressed in first heat exchange unit 43a, thus suppressing an increase in the power consumption of the pump.

In addition, air conditioning apparatus 103 according to Embodiment 4 may have the same configuration as that of air conditioning apparatus 101 according to Embodiment 2 or air conditioning apparatus 101 according to Embodiment 3, except that outdoor heat exchanger 43 has first heat exchange unit 43a and second heat exchange unit 43b having a smaller internal volume than that of first heat exchange unit 43a and that the area expansion rate of second heat exchange unit 43b is smaller than the area expansion rate of first heat exchange unit 43a.

Although the embodiments of the present disclosure have been described above, the above-described embodiments can be modified in various manners. In addition, the scope of the present disclosure is not limited to the above-described embodiments. It is intended that the scope of the present disclosure is defined by claims and encompasses all modifications and variations equivalent in meaning and scope to the claims.