Method for selecting heat medium of use side heat exchanger in installing air-conditioning system

A method for selecting a heat medium in installing an air-conditioning system includes: determining power required for use side heat exchangers corresponding to a plurality of air-conditioned spaces; calculating a total refrigerant amount required when a refrigerant is circulated through all the use side heat exchangers having the determined power; calculating a refrigerant concentration when the total refrigerant amount leaks to each air-conditioned space using the refrigerant, for each air-conditioned space; determining the refrigerant concentration for each air-conditioned space exceeds a predetermined limit concentration; when any air-conditioned space exceeds the limit concentration, selecting, as a nontoxic medium, the circulation heat medium of the use side heat exchanger installed in one of the air-conditioned spaces; and calculating a total refrigerant amount required when the refrigerant is circulated through all other use side heat exchangers.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application of PCT/JP2011/006703 filed on Nov. 30, 2011, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an air-conditioning apparatus used in, for example, a multi-air-conditioning apparatus for building.

BACKGROUND

As an air-conditioning apparatus, there is an apparatus in which a heat source unit (outdoor unit) is disposed outside a building and an indoor unit is disposed inside the building, for example, as in a multi-air-conditioning apparatus for building. A refrigerant circulating through a refrigerant circuit of such an air-conditioning apparatus rejects heat to (or removes heat from) air supplied to a heat exchanger of the indoor unit, thereby heating or cooling the air. Then, the heated or cooled air is sent to an air-conditioned space, thereby performing heating or cooling.

A building generally includes a plurality of indoor spaces, and thus such an air-conditioning apparatus also includes a plurality of indoor units accordingly. In addition, in the case where the size of the building is large, a refrigerant pipe connecting the outdoor unit to the indoor unit may be 100 m. When the length of the pipe connecting the outdoor unit to the indoor unit is long, an amount of the refrigerant injected to the refrigerant circuit is increased due to the long pipe.

Each indoor unit of such a multi-air-conditioning apparatus for building is generally disposed and used in an indoor space where a person is present (e.g., an office space, a living room, a store, etc.). When the refrigerant leaks from an indoor unit disposed in an indoor space for a certain reason, there is a possibility that the leak becomes problematic in terms of effect on human body and safety, since the refrigerant is flammable or toxic depending on its type. In addition, even when the refrigerant is not harmful to human body, it is also assumed that the oxygen concentration in the indoor space decreases due to the refrigerant leak, which influences on human body.

In order to deal with such a problem, a method is conceivable in which a two-loop system is employed in an air-conditioning apparatus, a refrigerant is used in a primary loop, harmless water or brine is used in a secondary loop to perform air-conditioning on a space where a person is present, the refrigerant in the primary side is used to perform direct air-conditioning on a shared space such as a corridor (e.g., see Patent Literature 1).

However, in the above system in which both air-conditioning with the refrigerant and air-conditioning with water or brine are performed, it is impossible to clearly determine which spaces air-conditioning with the refrigerant and air-conditioning with water or brine are selectively used.

PATENT LITERATURE

In the art as in Patent Literature 1 described above, there is hither to no method for selectively using air-conditioning with the refrigerant and air-conditioning with water or brine.

SUMMARY

Therefore, the present invention is directed to a usage method of presenting in which space air-conditioning with a refrigerant and air-conditioning with water or brine are selectively used in installing a system in which the air-conditioning with the refrigerant and the air-conditioning with water or brine are performed.

A method for selecting a heat medium of each of a plurality of use side heat exchangers in installing an air-conditioning system according to the present invention is a method for selecting a heat medium of each use side heat exchanger in installing an air-conditioning system in which a plurality of spaces are air-conditioning spaces and two types of circulation heat media including a refrigerant and a nontoxic medium are allowed to coexist as the circulation heat media of a use side heat exchanger installed in each of the plurality of spaces, the method including:

a first step of determining power required for the use side heat exchanger corresponding to each air-conditioned space;

a second step of calculating a total refrigerant amount required when the refrigerant is circulated through all the use side heat exchangers having the determined power;

a third step of calculating a refrigerant concentration when the total refrigerant amount leaks to each air-conditioned space using the refrigerant, for each air-conditioned space;

a fourth step of determining whether or not the refrigerant concentration for each air-conditioned space exceeds a predetermined limit concentration;

a fifth step of, when there are any air-conditioned spaces exceeding the limit concentration in the fourth step, selecting a nontoxic medium as the circulation heat medium of a use side heat exchanger installed in one of the air-conditioned spaces; and

a sixth step of calculating a total refrigerant amount required when the refrigerant is circulated through all the use side heat exchangers other than the use side heat exchanger in which the nontoxic medium is selected, as the total refrigerant amount in the third step.

In a system which is able to selectively use both a refrigerant and water or brine in an indoor unit as a material transmitting heat to a living space, it is possible to automatically and simply select a method for selectively using them.

DETAILED DESCRIPTION

As shown inFIG. 1, an air-conditioning apparatus100according to the embodiment includes one outdoor unit1which is a heat source unit, a plurality of indoor units2, a heat medium relay unit3interposed between the outdoor unit1and the indoor units2, a plurality of indoor units71, and a relay unit70interposed between the outdoor unit1and the indoor units71. The heat medium relay unit3exchanges heat between a heat source side refrigerant and a heat medium. The outdoor unit1and the heat medium relay unit3are connected to each other via refrigerant pipes4for circulating the heat source side refrigerant. The heat medium relay unit3and each indoor unit2are connected to each other via pipes (heat medium pipes)5for circulating the heat medium. Cooling energy or heating energy generated by the outdoor unit1is sent via the heat medium relay unit3to each indoor unit2. In addition, the refrigerant having passed through the relay unit70is sent directly to each indoor unit71.

The air-conditioning apparatus100according to the embodiment employs a method enabling both a method of indirectly using the heat source side refrigerant (an indirect method) and a method of directly using the heat source side refrigerant (a direct method). In other words, the air-conditioning apparatus100performs both: an operation in which cooling energy or heating energy stored in the heat source side refrigerant is transmitted to media different from the heat source side refrigerant (hereinafter, referred to as heat medium), and an air-conditioned space is cooled or heated with the cooling energy or heating energy stored in the heat medium; and an operation in which the air-conditioned space is cooled or heated directly with the cooling energy or heating energy stored in the heat source side refrigerant.

As shown inFIG. 2, the air-conditioning apparatus100has a refrigeration cycle through which a refrigerant circulates, and each of indoor units2ato2dand71eto71fis allowed to freely select a cooling mode or a heating mode as an operation mode.

The air-conditioning apparatus100according to the embodiment has a refrigerant circulation circuit A in which a single refrigerant such as R-22 or R-134a, a pseudo azeotropic refrigerant mixture such as R-410A or R-404A, a zeotropic refrigerant mixture such as R-407C, a refrigerant which contains a double bond within a chemical formula thereof and of which global warning potential is relatively low, such as CF3CF═CH2, a mixture thereof, or a natural refrigerant such as CO2or propane is used as a refrigerant; and a heat medium circulation circuit B in which water or the like is used as a heat medium.

The outdoor unit1is provided with a compressor10which compresses the refrigerant, a first refrigerant flow switching device11composed of a four-way valve or the like, a heat source side heat exchanger12which serves as an evaporator or a condenser, and an accumulator19which stores an excess refrigerant, and these components are connected with the refrigerant pipe4.

In addition, the outdoor unit1is provided with a first connection pipe4a, a second connection pipe4b, and check valves13(13ato13d). Since the first connection pipe4a, the second connection pipe4b, the check valve13a, the check valve13b, the check valve13c, and the check valve13dare provided, the flow of the heat source side refrigerant which flows into the heat medium relay unit3and the relay unit70can be a constant direction regardless of an operation requested by the indoor unit2.

The compressor10sucks the heat source side refrigerant and compresses the heat source side refrigerant into a high-temperature and high-pressure state, and may be composed of, for example, a capacity-controllable inverter compressor or the like.

The first refrigerant flow switching device11switches between the flow of the heat source side refrigerant during a heating operation mode (during a heating only operation mode and during a heating main operation mode) and the flow of the heat source side refrigerant during a cooling operation mode (during a cooling only operation mode and during a cooling main operation mode).

The heat source side heat exchanger12serves as an evaporator during the heating operation, serves as a condenser during the cooling operation, and exchanges heat between the heat source side refrigerant and air supplied from an air-sending device such as a fan which is not shown.

Each indoor unit2is provided with a use side heat exchanger26. The use side heat exchanger26is connected to a heat medium flow control device25and a second heat medium flow switching device23of the heat medium relay unit3via pipes5. The use side heat exchanger26exchanges heat between the heat medium and air supplied from an air-sending device such as a fan which is not shown, to generate air for heating or air for cooling which is to be supplied to an indoor space7.

Each indoor unit71is provided with a use side heat exchanger61and an expansion valve62. The use side heat exchanger61is connected to an expansion device65and an expansion device66of the relay unit70via pipes67and to solenoid valves63and solenoid valves64of the relay unit70via pipes. The use side heat exchanger61exchanges heat between the heat medium and air supplied from an air-sending device such as a fan which is not shown, to generate air for heating or air for cooling which is to be supplied to an indoor space80.

The heat medium relay unit3is provided with two intermediate heat exchangers15(15aand15b) which exchange heat between the refrigerant and the heat medium, two expansion devices16(16aand16b) which reduce the pressure of the refrigerant, two opening/closing devices17(17aand17b) which open/close a flow path of the refrigerant pipe4, two second refrigerant flow switching devices18(18aand18b) which switch a refrigerant flow path, two pumps21(21aand21b) which circulates the heat medium, four first heat medium flow switching devices22(22ato22d) which are connected to one of the pipes5, the four second heat medium flow switching devices23(23ato23d) which are connected to the other pipe5, and the four heat medium flow control devices25(25ato25b) which are connected to the pipe5to which the first heat medium flow switching devices22are connected.

The intermediate heat exchangers15aand15bserve as condensers (radiators) or evaporators, exchange heat between the heat source side refrigerant and the heat medium, and transmit to the heat medium cooling energy or heating energy which is generated by the outdoor unit1and stored in the heat source side refrigerant. The intermediate heat exchanger15ais provided between the expansion device16aand the second refrigerant flow switching device18ain the refrigerant circulation circuit A and is used to cool the heat medium during a cooling and heating mixed operation mode. The intermediate heat exchanger15bis provided between the expansion device16band the second refrigerant flow switching device18bin the refrigerant circulation circuit A and is used to heat the heat medium during the cooling and heating mixed operation mode.

The expansion devices16aand16bhave functions as a pressure reducing valve and an expansion valve and reduce the pressure of the heat source side refrigerant to expand the heat source side refrigerant. The expansion device16ais provided at the upstream side of the intermediate heat exchanger15ain the flow of the heat source side refrigerant during the cooling only operation mode. The expansion device16bis provided at the upstream side of the intermediate heat exchanger15bin the flow of the heat source side refrigerant during the cooling only operation mode. These expansion devices16may be composed of expansion devices whose opening degree is variably controllable, such as electronic expansion valves.

The opening/closing devices17aand17bare composed of two-way valves or the like and open/close the refrigerant pipe4.

The second refrigerant flow switching devices18aand18bare composed of four-way valves or the like and switch flow of the heat source side refrigerant in accordance with the operation mode. The second refrigerant flow switching device18ais provided at the downstream side of the intermediate heat exchanger15ain the flow of the heat source side refrigerant during the cooling only operation mode. The second refrigerant flow switching device18bis provided at the downstream side of the intermediate heat exchanger15bin the flow of the heat source side refrigerant during the cooling only operation mode.

The pumps21aand21bcirculate the heat medium within the pipes5. The pump21ais provided on the pipe5between the intermediate heat exchanger15aand the second heat medium flow switching device23. The pump21bis provided on the pipe5between the intermediate heat exchanger15band the second heat medium flow switching device23. These pumps21may be composed of, for example, capacity-controllable pumps or the like. It should be noted that the pump21amay be provided on the pipe5between the intermediate heat exchanger15aand the first heat medium flow switching devices22. In addition, the pump21bmay be provided on the pipe5between the intermediate heat exchanger15band the first heat medium flow switching devices22.

The first heat medium flow switching devices22(22ato22d) are composed of three-way valves or the like and switch a flow path of the heat medium. The number of the provided first heat medium flow switching devices22corresponds to the number of the installed indoor units2. Each first heat medium flow switching device22is connected at one of the three ways to the intermediate heat exchanger15a, at one of the three ways to the intermediate heat exchanger15b, and at one of the three ways to the heat medium flow control device25, and is provided at an outlet side of the heat medium flow path at the use side heat exchanger26. It should be noted that the first heat medium flow switching devices22are illustrated as the first heat medium flow switching device22a, the first heat medium flow switching device22b, the first heat medium flow switching device22c, and the first heat medium flow switching device22din order from the lower side of the sheet surface so as to correspond to the indoor units2.

The second heat medium flow switching devices23(23ato23d) are composed of three-way valves or the like and switch the flow path of the heat medium. The number (four here) of the provided second heat medium flow switching devices23corresponds to the number of the installed indoor units2. Each second heat medium flow switching device23is connected at one of the three ways to the intermediate heat exchanger15a, at one of the three ways to the intermediate heat exchanger15b, and at one of the three ways to the use side heat exchanger26, and is provided at an inlet side of the heat medium flow path at the use side heat exchanger26. Here, the second heat medium flow switching devices23are illustrated as the second heat medium flow switching device23a, the second heat medium flow switching device23b, the second heat medium flow switching device23c, and the second heat medium flow switching device23din order from the lower side of the sheet surface so as to correspond to the indoor units2.

The heat medium flow control devices25(25ato25d) are composed of two-way valves whose opening area is controllable, or the like, and adjust a flow rate of the heat medium flowing through the pipe5. The number of the provided heat medium flow control devices25corresponds to the number of the installed indoor units2. Each heat medium flow control device25is connected at one way to the use side heat exchanger26and at the other way to the first heat medium flow switching device22, and is provided at the outlet side of the heat medium flow path at the use side heat exchanger26. Here, the heat medium flow control devices25are illustrated as the heat medium flow control device25a, the heat medium flow control device25b, the heat medium flow control device25c, and the heat medium flow control device25din order from the lower side of the sheet surface so as to correspond to the indoor units2. In addition, each heat medium flow control device25may be provided at the inlet side of the heat medium flow path at the use side heat exchanger26.

The pipes5for circulating the heat medium therethrough are composed of a pipe connected to the intermediate heat exchanger15aand a pipe connected to the intermediate heat exchanger15band are connected via the first heat medium flow switching devices22and the second heat medium flow switching devices23. The pipes5are branched in accordance with the number of the indoor units2connected to the heat medium relay unit3(here, each branched into 4 portions). The pipes5are configured such that it is determined whether to cause the heat medium from the intermediate heat exchanger15ato flow into the use side heat exchanger26or the heat medium from the intermediate heat exchanger15bto flow into the use side heat exchanger26, by controlling the first heat medium flow switching devices22and the second heat medium flow switching devices23.

The relay unit70is arranged between the outdoor unit1and the indoor units71(71eto71h). The relay unit70includes the solenoid valves63eto63hwhich switch the flow of the refrigerant to the cooling side, the solenoid valves64eto64hwhich switch the flow of the refrigerant to the heating side, a cooling indoor unit inlet expansion device65, and an expansion device66which opens during the heating only/heating main operation, and allows for cooling and heating mixed operation of the indoor units71. In addition, the indoor units71(71eto71h) each include a use side heat exchanger61(61eto61h) using the refrigerant and an indoor expansion device62(62eto62h).

[Explanation of Operation Mode]

In the air-conditioning apparatus100, the compressor10, the first refrigerant flow switching device11, the heat source side heat exchanger12, the opening/closing devices17, the second refrigerant flow switching devices18, the refrigerant flow paths at the intermediate heat exchangers15, the expansion devices16, and the accumulator19are connected to each other via the refrigerant pipes4to form the refrigerant circulation circuit A. In addition, the heat medium flow paths at the intermediate heat exchangers15, the pumps21, the first heat medium flow switching devices22, the heat medium flow control devices25, the use side heat exchangers26, and the second heat medium flow switching devices23are connected to each other via the pipes5to form the heat medium circulation circuit B. In other words, a plurality of the use side heat exchangers26are connected in parallel to each of the intermediate heat exchangers15.

Thus, in the air-conditioning apparatus100, the outdoor unit1and the heat medium relay unit3are connected to each other via the intermediate heat exchanger15aand the intermediate heat exchanger15bprovided in the heat medium relay unit3, and the heat medium relay unit3and the indoor units2are also connected to each other via the intermediate heat exchanger15aand the intermediate heat exchanger15b. In other words, in the air-conditioning apparatus100, at the intermediate heat exchanger15aand the intermediate heat exchanger15b, heat is exchanged between the heat source side refrigerant circulating through the refrigerant circulation circuit A and the heat medium circulating through the heat medium circulation circuit B.

It should be noted that separately from the above refrigerant circuits, the outdoor unit1and the relay unit70are connected to each other via the pipes4, and the refrigerant is supplied from the relay unit70also to the indoor units71.

Each operation mode executed by the air-conditioning apparatus100will be described. On the basis of an instruction from each indoor unit2, the air-conditioning apparatus100allows a cooling operation or heating operation to be performed by the indoor unit2. In other words, the air-conditioning apparatus100allows the same operation to be performed by all of the indoor units2and the indoor units71, and allows different operations to be performed by the respective indoor units2.

The operation modes executed by the air-conditioning apparatus100include the cooling only operation mode in which all the activated indoor units2and71perform a cooling operation, the heating only operation mode in which all the activated indoor units2and71perform a heating operation, the cooling main operation mode as the cooling and heating mixed operation mode in which a cooling load is greater, and the heating main operation mode as the cooling and heating mixed operation mode in which a heating load is greater. Hereinafter, each operation mode will be described with flows of the heat source side refrigerant and the heat medium.

FIG. 3is a refrigerant circuit diagram showing the flow of the refrigerant during the cooling only operation mode of the air-conditioning apparatus100shown inFIG. 2. InFIG. 3, the cooling only operation mode will be described with, an example, the case where cooling energy loads are generated at the use side heat exchangers26a,26b, and61eto61h. InFIG. 3, the pipes represented by thick lines indicate pipes through which the refrigerants (the heat source side refrigerant and the heat medium) flow. In addition, inFIG. 3, the flow direction of the heat source side refrigerant is indicated by solid arrows, and the flow direction of the heat medium is indicated by dashed arrows.

In the case of the cooling only operation mode shown inFIG. 3, in the outdoor unit1, the first refrigerant flow switching device11is switched such that the heat source side refrigerant having discharged from the compressor10flows into the heat source side heat exchanger12. In the heat medium relay unit3, the pump21aand the pump21bare actuated, the heat medium flow control device25aand the heat medium flow control device25bare opened, and the heat medium flow control device25cand the heat medium flow control device25dare fully closed, whereby the heat medium circulates between each of the intermediate heat exchanger15aand the intermediate heat exchanger15band the use side heat exchanger26aand the use side heat exchanger26b.

First, flow of the heat source side refrigerant in the refrigerant circulation circuit A will be described. The low-temperature and low-pressure refrigerant is compressed by the compressor10into a high-temperature and high-pressure gas refrigerant, and is discharged therefrom. The high-temperature and high-pressure gas refrigerant having discharged from the compressor10flows through the first refrigerant flow switching device11into the heat source side heat exchanger12. Then, the gas refrigerant becomes a high-pressure liquid refrigerant while rejecting heat to the outside air at the heat source side heat exchanger12. The high-pressure refrigerant having flowed out of the heat source side heat exchanger12flows out of the outdoor unit1through the check valve13a, and flows through the refrigerant pipe4into the heat medium relay unit3. The high-pressure refrigerant having flowed into the heat medium relay unit3flows through the opening/closing device17a, then is branched, is expanded at the expansion device16aand the expansion device16binto a low-temperature and low-pressure two-phase refrigerant. It should be noted that the opening/closing device17bis closed.

The two-phase refrigerant flows into the intermediate heat exchanger15aand the intermediate heat exchanger15bwhich act as evaporators, and removes heat from the heat medium circulating through the heat medium circulation circuit B, whereby the two-phase refrigerant becomes a low-temperature and low-pressure gas refrigerant while cooling the heat medium. The gas refrigerant having flowed out of the intermediate heat exchanger15aand the intermediate heat exchanger15bflows out of the heat medium relay unit3through the second refrigerant flow switching device18aand the second refrigerant flow switching device18band flows through the refrigerant pipe4into the outdoor unit1again. The refrigerant having flowed into the outdoor unit1flows through the check valve13dand is sucked into the compressor10again through the first refrigerant flow switching device11and the accumulator19.

Next, flow of the heat medium in the heat medium circulation circuit B will be described. In the cooling only operation mode, cooling energy of the heat source side refrigerant is transmitted to the heat medium at both the intermediate heat exchanger15aand the intermediate heat exchanger15b, and the cooled heat medium is moved in the pipes5by the pump21aand the pump21b. The heat medium having compressed by the pump21aand the pump21band flowed out therefrom flows through the second heat medium flow switching device23aand the second heat medium flow switching device23binto the use side heat exchanger26aand the use side heat exchanger26b. Then, the heat medium removes heat from the indoor air at the use side heat exchanger26aand the use side heat exchanger26b, thereby cooling the indoor space7.

Then, the heat medium flows out of the use side heat exchanger26aand the use side heat exchanger26band flows into the heat medium flow control device25aand the heat medium flow control device25b. At that time, the flow rate of the heat medium is controlled by the action of the heat medium flow control device25aand the heat medium flow control device25bto a flow rate required for an air conditioning load required in the indoor, and the heat medium flows into the use side heat exchanger26aand the use side heat exchanger26b. The heat medium having flowed out of the heat medium flow control device25aand the heat medium flow control device25bflows through the first heat medium flow switching device22aand the first heat medium flow switching device22binto the intermediate heat exchanger15aand the intermediate heat exchanger15band is sucked into the pump21aand the pump21bagain.

In executing the cooling only operation mode, since there is no need to flow the heat medium to the use side heat exchanger26in which there is no thermal load (including thermo-off), the flow path is closed by the heat medium flow control device25such that the heat medium does not flow to the use side heat exchanger26. InFIG. 3, the heat medium is flowing through the use side heat exchanger26aand the use side heat exchanger26bsince there are thermal loads in the use side heat exchanger26aand the use side heat exchanger26b, but there are no thermal loads in the use side heat exchanger26cand the use side heat exchanger26d, and the corresponding heat medium flow control device25cand the corresponding heat medium flow control device25dare fully closed. Then, when thermal loads are generated from the use side heat exchanger26cand the use side heat exchanger26d, the heat medium flow control device25cand the heat medium flow control device25dmay be opened to circulate the heat medium therethrough.

In addition, the heat source side refrigerant having passed through the above pipe4also flows to the relay unit70side, passes through the expansion device65and the expansion devices62, then removes heat and evaporates at the use side heat exchangers61, passes through the solenoid valve63, and then returns to the outdoor unit1. Thus, the indoor space80is cooled.

FIG. 4is a refrigerant circuit diagram showing the flow of the refrigerant during the heating only operation mode of the air-conditioning apparatus100shown inFIG. 2. InFIG. 4, the heating only operation mode will be described with, as an example, the case where heating energy loads are generated at the use side heat exchangers26a,26b, and61eto61h. InFIG. 4, the pipes represented by thick lines indicate pipes through which the refrigerants (the heat source side refrigerant and the heat medium) flow. In addition, inFIG. 4, the flow direction of the heat source side refrigerant is indicated by solid arrows, and the flow direction of the heat medium is indicated by dashed arrows.

In the case of the heating only operation mode shown inFIG. 4, in the outdoor unit1, the first refrigerant flow switching device11is switched such that the heat source side refrigerant having discharged from the compressor10flows into the heat medium relay unit3without passing through the heat source side heat exchanger12. In the heat medium relay unit3, the pump21aand the pump21bare actuated, the heat medium flow control device25aand the heat medium flow control device25bare opened, and the heat medium flow control device25cand the heat medium flow control device25dare fully closed, whereby the heat medium circulates between each of the intermediate heat exchanger15aand the intermediate heat exchanger15band the use side heat exchanger26aand the use side heat exchanger26b.

First, flow of the heat source side refrigerant in the refrigerant circulation circuit A will be described. The low-temperature and low-pressure refrigerant is compressed by the compressor10into a high-temperature and high-pressure gas refrigerant, and is discharged therefrom. The high-temperature and high-pressure gas refrigerant having discharged from the compressor10passes through the first refrigerant flow switching device11and the check valve13band flows out of the outdoor unit1. The high-temperature and high-pressure gas refrigerant having flowed out of the outdoor unit1flows through the refrigerant pipe4into the heat medium relay unit3. The high-temperature and high-pressure gas refrigerant having flowed into the heat medium relay unit3is branched, passes through the second refrigerant flow switching device18aand the second refrigerant flow switching device18b, and flows into the intermediate heat exchanger15aand the intermediate heat exchanger15b.

The high-temperature and high-pressure gas refrigerant having flowed into the intermediate heat exchanger15aand the intermediate heat exchanger15bbecomes a high-pressure liquid refrigerant while rejecting heat to the heat medium circulating through the heat medium circulation circuit B. The liquid refrigerant having flowed out of the intermediate heat exchanger15aand the intermediate heat exchanger15bis expanded at the expansion device16aand the expansion device16binto a low-temperature and low-pressure two-phase refrigerant. The two-phase refrigerant flows out of the heat medium relay unit3through the opening/closing device17band flows through the refrigerant pipe4into the outdoor unit1again. It should be noted that the opening/closing device17ais closed.

The refrigerant having flowed into the outdoor unit1flows through the check valve13cinto the heat source side heat exchanger12which acts as an evaporator. Then, the refrigerant having flowed into the heat source side heat exchanger12removes heat from the outside air and becomes a low-temperature and low-pressure gas refrigerant at the heat source side heat exchanger12. The low-temperature and low-pressure gas refrigerant having flowed out of the heat source side heat exchanger12is sucked into the compressor10again through the first refrigerant flow switching device11and the accumulator19.

Next, flow of the heat medium in the heat medium circulation circuit B will be described.

In the heating only operation mode, heating energy of the heat source side refrigerant is transmitted to the heat medium at both the intermediate heat exchanger15aand the intermediate heat exchanger15b, and the heated heat medium is moved in the pipes5by the pump21aand the pump21b. The heat medium having compressed by the pump21aand the pump21band having flowed out flows through the second heat medium flow switching device23aand the second heat medium flow switching device23binto the use side heat exchanger26aand the use side heat exchanger26b. Then, the heat medium rejects heat to the indoor air at the use side heat exchanger26aand the use side heat exchanger26b, thereby heating the indoor space7.

Then, the heat medium flows out of the use side heat exchanger26aand the use side heat exchanger26band flows into the heat medium flow control device25aand the heat medium flow control device25b. At that time, the flow rate of the heat medium is controlled by the action of the heat medium flow control device25aand the heat medium flow control device25bto a flow rate required for an air conditioning load required in the indoor, and the heat medium flows into the use side heat exchanger26aand the use side heat exchanger26b. The heat medium having flowed out of the heat medium flow control device25aand the heat medium flow control device25bflows through the first heat medium flow switching device22aand the first heat medium flow switching device22binto the intermediate heat exchanger15aand the intermediate heat exchanger15band is sucked into the pump21aand the pump21bagain.

In executing the heating only operation mode, since there is no need to flow the heat medium to the use side heat exchanger26in which there is no thermal load (including thermo-off), the flow path is closed by the heat medium flow control device25such that the heat medium does not flow to the use side heat exchanger26. InFIG. 4, the heat medium is flowing through the use side heat exchanger26aand the use side heat exchanger26bsince there are thermal loads in the use side heat exchanger26aand the use side heat exchanger26b, but there are no thermal loads in the use side heat exchanger26cand the use side heat exchanger26d, and the corresponding heat medium flow control device25cand the corresponding heat medium flow control device25dare fully closed. Then, when thermal loads are generated from the use side heat exchanger26cand the use side heat exchanger26d, the heat medium flow control device25cand the heat medium flow control device25dmay be opened to circulate the heat medium therethrough.

In addition, the heat source side refrigerant (gas refrigerant) having passed through the above pipe4also flows to the relay unit70side, passes through the solenoid valve64, rejects heat at the use side heat exchangers61, passes through the indoor expansion devices62and the expansion device66, and then returns through the pipe4to the outdoor unit1. Thus, the indoor space80is heated.

FIG. 5is a refrigerant circuit diagram showing the flow of the refrigerant during the cooling main operation mode of the air-conditioning apparatus100shown inFIG. 2. InFIG. 5, the cooling main operation mode will be described with, as an example, the case where a cooling energy load is generated at the use side heat exchanger26aand a heating energy load is generated at the use side heat exchanger26b. InFIG. 5, the pipes represented by thick lines indicate pipes through which the refrigerants (the heat source side refrigerant and the heat medium) circulate. In addition, inFIG. 5, the flow direction of the heat source side refrigerant is indicated by solid arrows, and the flow direction of the heat medium is indicated by dashed arrows.

In the case of the cooling main operation mode shown inFIG. 5, in the outdoor unit1, the first refrigerant flow switching device11is switched such that the heat source side refrigerant having discharged from the compressor10flows into the heat source side heat exchanger12. In the heat medium relay unit3, the pump21aand the pump21bare activated, the heat medium flow control device25aand the heat medium flow control device25bare opened, and the heat medium flow control device25cand the heat medium flow control device25dare fully closed, whereby the heat medium circulates between the intermediate heat exchanger15aand the use side heat exchanger26aand between the intermediate heat exchanger15band the use side heat exchanger26b.

First, flow of the heat source side refrigerant in the refrigerant circulation circuit A will be described. The low-temperature and low-pressure refrigerant is compressed by the compressor10into a high-temperature and high-pressure gas refrigerant, and is discharged therefrom. The high-temperature and high-pressure gas refrigerant having discharged from the compressor10flows through the first refrigerant flow switching device11into the heat source side heat exchanger12. Then, the gas refrigerant becomes a liquid refrigerant while rejecting heat to the outside air at the heat source side heat exchanger12. The refrigerant having flowed out of the heat source side heat exchanger12flows out of the outdoor unit1and flows through the check valve13aand the refrigerant pipe4into the heat medium relay unit3. The refrigerant having flowed into the heat medium relay unit3flows through the second refrigerant flow switching device18binto the intermediate heat exchanger15bwhich acts as a condenser.

The refrigerant having flowed into the intermediate heat exchanger15bbecomes a refrigerant having a further decreased temperature, while rejecting heat to the heat medium circulating through the heat medium circulation circuit B. The refrigerant having flowed out of the intermediate heat exchanger15bis expanded at the expansion device16binto a low-pressure two-phase refrigerant. The low-pressure two-phase refrigerant flows through the expansion device16ainto the intermediate heat exchanger15awhich acts as an evaporator. The low-pressure two-phase refrigerant having flowed into the intermediate heat exchanger15abecomes a low-pressure gas refrigerant while cooling the heat medium by removing heat from the heat medium circulating the heat medium circulation circuit B. The gas refrigerant flows out of the intermediate heat exchanger15a, flows out of the heat medium relay unit3through the second refrigerant flow switching device18a, and flows through the refrigerant pipe4into the outdoor unit1again. The refrigerant having flowed into the outdoor unit1is sucked into the compressor10again through the check valve13d, the first refrigerant flow switching device11, and the accumulator19.

Next, flow of the heat medium in the heat medium circulation circuit B will be described.

In the cooling main operation mode, heating energy of the heat source side refrigerant is transmitted to the heat medium at the intermediate heat exchanger15b, and the heated heat medium is moved in the pipe5by the pump21b. In addition, in the cooling main operation mode, cooling energy of the heat source side refrigerant is transmitted to the heat medium at the intermediate heat exchanger15a, and the cooled heat medium is moved in the pipe5by the pump21a. The heated heat medium having compressed by the pump21band having flowed out flows through the second heat medium flow switching device23binto the use side heat exchanger26b. The cooled heat medium having compressed by the pump21aand having flowed out flows through the second heat medium flow switching device23ainto the use side heat exchanger26a.

At the use side heat exchanger26b, the heat medium rejects heat to the indoor air, thereby heating the indoor space7. In addition, at the use side heat exchanger26a, the heat medium removes heat from the indoor air, thereby cooling the indoor space7. At that time, the flow rate of the heat medium is controlled by the action of the heat medium flow control device25aand the heat medium flow control device25bto a flow rate required for an air conditioning load required in the indoor, and the heat medium flows into the use side heat exchanger26aand the use side heat exchanger26b. The heat medium having passed through the use side heat exchanger26band having a slightly decreased temperature flows through the heat medium flow control device25band the first heat medium flow switching device22binto the intermediate heat exchanger15band is sucked into the pump21bagain. On the other hand, the heat medium having passed through the use side heat exchanger26aand having a slightly increased temperature flows through the heat medium flow control device25aand the first heat medium flow switching device22ainto the intermediate heat exchanger15aand is sucked into the pump21aagain.

In executing the cooling main operation mode, since there is no need to flow the heat medium to the use side heat exchanger26in which there is no thermal load (including thermo-off), the flow path is closed by the heat medium flow control device25such that the heat medium does not flow to the use side heat exchanger26. InFIG. 5, the heat medium is flowing through the use side heat exchanger26aand the use side heat exchanger26bsince there are thermal loads in the use side heat exchanger26aand the use side heat exchanger26b, but there are no thermal loads in the use side heat exchanger26cand the use side heat exchanger26d, and the corresponding heat medium flow control device25cand the corresponding heat medium flow control device25dare fully closed. Then, when thermal loads are generated from the use side heat exchanger26cand the use side heat exchanger26d, the heat medium flow control device25cand the heat medium flow control device25dmay be opened to circulate the heat medium therethrough.

In addition, the refrigerant having passed through the above pipe4also flows to the relay unit70side, and a portion of the refrigerant having flowed therein enters the indoor unit71ethrough the solenoid valve64e, rejects heat at the use side heat exchanger61e, then is reduced in pressure at the expansion device62e, and flows into the relay unit70again. The refrigerant having flowed therein again joins the refrigerant having passed through the expansion device65, flows through the indoor expansion devices62fto62h, then removes heat and evaporates at the use side heat exchangers61fto61h, flows through the solenoid valve63, and returns to the outdoor unit1.

FIG. 6is a refrigerant circuit diagram showing the flow of the refrigerant during the heating main operation mode of the air-conditioning apparatus100shown inFIG. 2. InFIG. 6, the heating main operation mode will be described with, as an example, the case where a heating energy load is generated at the use side heat exchanger26aand a cooling energy load is generated at the use side heat exchanger26b. InFIG. 6, the pipes represented by thick lines indicate pipes through which the refrigerants (the heat source side refrigerant and the heat medium) circulate. In addition, inFIG. 6, the flow direction of the heat source side refrigerant is indicated by solid arrows, and the flow direction of the heat medium is indicated by dashed arrows.

In the case of the heating main operation mode shown inFIG. 6, in the outdoor unit1, the first refrigerant flow switching device11is switched such that the heat source side refrigerant having discharged from the compressor10flows into the heat medium relay unit3without passing through the heat source side heat exchanger12. In the heat medium relay unit3, the pump21aand the pump21bare activated, the heat medium flow control device25aand the heat medium flow control device25bare opened, and the heat medium flow control device25cand the heat medium flow control device25dare fully closed, whereby the heat medium circulates between the intermediate heat exchanger15aand the use side heat exchanger26band between the intermediate heat exchanger15band the use side heat exchanger26a.

First, flow of the heat source side refrigerant in the refrigerant circulation circuit A will be described. The low-temperature and low-pressure refrigerant is compressed by the compressor10into a high-temperature and high-pressure gas refrigerant, and is discharged therefrom. The high-temperature and high-pressure gas refrigerant having discharged from the compressor10passes through the first refrigerant flow switching device11and the check valve13band flows out of the outdoor unit1. The high-temperature and high-pressure gas refrigerant having flowed from the outdoor unit1flows through the refrigerant pipe4into the heat medium relay unit3. The high-temperature and high-pressure gas refrigerant having flowed into the heat medium relay unit3flows through the second refrigerant flow switching device18binto the intermediate heat exchanger15bwhich acts as a condenser.

The gas refrigerant having flowed into the intermediate heat exchanger15bbecomes a liquid refrigerant while rejecting heat to the heat medium circulating through the heat medium circulation circuit B. The refrigerant having flowed out of the intermediate heat exchanger15bis expanded at the expansion device16binto a low-pressure two-phase refrigerant. The low-pressure two-phase refrigerant flows through the expansion device16ainto the intermediate heat exchanger15awhich acts as an evaporator. The low-pressure two-phase refrigerant having flowed into the intermediate heat exchanger15aevaporates by removing heat from the heat medium circulating through the heat medium circulation circuit B, thereby cooling the heat medium. The low-pressure two-phase refrigerant flows out of the intermediate heat exchanger15aand flows out of the heat medium relay unit3through the second refrigerant flow switching device18a, and flows into the outdoor unit1again.

The refrigerant having flowed into the outdoor unit1flows through the check valve13cinto the heat source side heat exchanger12which acts as an evaporator. Then, the refrigerant having flowed into the heat source side heat exchanger12removes heat from the outside air and becomes a low-temperature and low-pressure gas refrigerant at the heat source side heat exchanger12. The low-temperature and low-pressure gas refrigerant having flowed out of the heat source side heat exchanger12is sucked into the compressor10again through the first refrigerant flow switching device11and the accumulator19.

Next, flow of the heat medium in the heat medium circulation circuit B will be described.

In the heating main operation mode, heating energy of the heat source side refrigerant is transmitted to the heat medium at the intermediate heat exchanger15b, and the heated heat medium is moved in the pipe5by the pump21b. In addition, in the heating main operation mode, cooling energy of the heat source side refrigerant is transmitted to the heat medium at the intermediate heat exchanger15a, and the cooled heat medium is moved in the pipe5by the pump21a. The heated heat medium having compressed by the pump21band having flowed out flows through the second heat medium flow switching device23ainto the use side heat exchanger26a. The cooled heat medium having compressed by the pump21aand having flowed out flows through the second heat medium flow switching device23binto the use side heat exchanger26b.

At the use side heat exchanger26b, the heat medium removes heat from the indoor air, thereby cooling the indoor space7. In addition, at the use side heat exchanger26a, the heat medium rejects heat to the indoor air, thereby heating the indoor space7. At that time, the flow rate of the heat medium is controlled by the action of the heat medium flow control device25aand the heat medium flow control device25bto a flow rate required for an air conditioning load required in the indoor, and the heat medium flows into the use side heat exchanger26aand the use side heat exchanger26b. The heat medium having passed through the use side heat exchanger26band having a slightly increased temperature flows through the heat medium flow control device25band the first heat medium flow switching device22binto the intermediate heat exchanger15aand is sucked into the pump21aagain. The heat medium having pass through the use side heat exchanger26aand having a slightly decreased temperature flows through the heat medium flow control device25aand the first heat medium flow switching device22ainto the intermediate heat exchanger15band is sucked into the pump21bagain.

In executing the heating main operation mode, since there is no need to flow the heat medium to the use side heat exchanger26in which there is no thermal load (including thermo-off), the flow path is closed by the heat medium flow control device25such that the heat medium does not flow to the use side heat exchanger26. InFIG. 6, the heat medium is flowing through the use side heat exchanger26aand the use side heat exchanger26bsince there are thermal loads in the use side heat exchanger26aand the use side heat exchanger26b, but there are no thermal loads in the use side heat exchanger26cand the use side heat exchanger26d, and the corresponding heat medium flow control device25cand the corresponding heat medium flow control device25dare fully closed. Then, when thermal loads are generated from the use side heat exchanger26cand the use side heat exchanger26d, the heat medium flow control device25cand the heat medium flow control device25dmay be opened to circulate the heat medium therethrough.

In addition, the gas refrigerant having passed through the above pipe4also flows into the relay unit70side, and a portion of the refrigerant having flowed therein enters the solenoid valves64eto64g. The refrigerant having passed through the solenoid valves64eto64enters the indoor units71eto71g, rejects heat at the use side heat exchangers61eto61g, then is reduced in pressure at the expansion devices62eto62g, flows into the relay unit70again, and joins the refrigerant having passed through the expansion device65. A portion of the joined refrigerant passes through the expansion device62h, rejects heat and then evaporates at the use side heat exchanger61h, and enters the solenoid valve63h. Then, the refrigerant having flowed out of the solenoid valve63hjoins again the refrigerant having separated after the above joining and having passed through the expansion device66, and returns to the outdoor unit1.

As described above, the air-conditioning apparatus100according to the embodiment includes several operation modes. In these operation modes, the heat source side refrigerant flows through the refrigerant pipes4connecting the outdoor unit1to the heat medium relay unit3or the relay unit70.

In each of the operation modes executed by the air-conditioning apparatus100according to the embodiment, the heat medium such as water or an antifreezing solution flows through the pipes5connecting the heat medium relay unit3to the indoor units2.

For example, a brine (antifreezing solution), water, a mixed solution of a brine and water, a mixed solution of water and an additive exhibiting a high anti-corrosion effect, or the like may be used as the heat medium. Therefore, even when the heat medium leaks through the indoor unit2to the indoor space7, the air-conditioning apparatus100contributes to improvement of safety since a highly safe medium is used as the heat medium in the air-conditioning apparatus100.

Next, a method for selecting a medium for heating or cooling which circulates through each indoor unit in installing the indoor unit for the air-conditioning apparatus100will be described.

FIG. 7is an example of a space which is air-conditioned by the air-conditioning apparatus100including indoor units A to F. The heat medium relay unit3, the relay unit70, and the indoor unit F are installed in a space such as a path, and the five indoor units A to E are set to air-condition five air-conditioned spaces (or rooms). Here, the volume of the space for the indoor unit A is 800 m3; the volume of the space for the indoor unit B is 80 m3; the volume of the space for the indoor unit C is 120 m3; the volume of the space for the indoor unit D is 120 m3; and the volume of the space for the indoor unit E is 60 m3. The distance from the relay unit70to each indoor unit is shorter in order of the indoor units A, B, C, D, and E. It should be noted that the signs for the indoor units A to E are signs defined separately from the signs for the indoor units2and71shown inFIGS. 1 to 6.

FIG. 8is a flowchart showing a method for selecting, based on distance, the medium which circulates through the indoor unit disposed in each space inFIG. 7according to one embodiment of the present invention.

Power required for each of the spaces in which the respective indoor units A to E is selected. In addition, at that time, an indoor unit excluded from automatic selection is selected. For example, in the case of installation at a shared floor like the indoor unit F, water is not used and a refrigerant is used as a medium. It should be noted that if refrigerant sound is noisy, water may be selected as a medium. It should be noted that inFIG. 8, for convenience, a chlorofluorocarbon refrigerant is used as a refrigerant.

The total refrigerant amount in the air-conditioning apparatus100when each of the media of the indoor units (here, A to E) other than the indoor unit excluded in step 1 is the refrigerant is calculated. For example, here, the total refrigerant amount is 25 kg.

A concentration of the refrigerant when the total refrigerant amount in the air-conditioning apparatus100leaks to one air-conditioned space is calculated for each air-conditioned space. For example, for the space for the indoor unit B, 25 kg÷80 m3=0.31 kg/m3; and for the space for the indoor unit E, 25 kg÷60 m3=0.416 kg/m3.

It is determined whether as a result of the calculation in step 3, there is an air-conditioned space for which the refrigerant concentration exceeds a limit concentration. For example, when the limit concentration is set at 0.3 kg/m3, the air-conditioned spaces for the indoor unit B (0.31 kg/m3) and the indoor unit E (0.416 kg/m3) exceed the limit concentration.

Of the air-conditioned spaces exceeding the limit concentration in step 4, the medium of the use side heat exchanger of the indoor unit71farthest from the relay unit70is changed from the refrigerant to water. In this example, regarding the above distance, the indoor unit E is farther than the indoor unit B, and thus water is used as the medium for the indoor unit E. It should be noted that the above “indoor unit71farthest from the relay unit70” corresponds to the fact that the refrigerant circuit length from the relay unit70to the indoor unit71is longest. For this, it is considered that the longer the refrigerant circuit from the relay unit70to the indoor unit71is, the more the leak amount of the refrigerant is.

The total refrigerant amount in the air-conditioning apparatus100is calculated again, and the processing returns to step 3.

When there is no air-conditioned space exceeding the limit concentration in step 4, the consideration is completed and the media of the indoor units are determined.

According to the flow inFIG. 8, it is automatically determined to circulate the refrigerant through the indoor units A to D and to circulate water through the indoor unit E. Therefore, the indoor units71shown inFIGS. 1 to 6are used as the indoor units A to D, and the indoor unit2shown inFIGS. 1 to 6is used as the indoor unit E.

FIG. 9is a flowchart showing a method for selecting, based on amount, the medium which circulates through the indoor unit disposed in each space ofFIG. 7according to another embodiment of the present invention. The difference betweenFIG. 9andFIG. 8is only step 5. In other words, in the example ofFIG. 9, of the air-conditioned spaces exceeding the limit concentration, the circulation medium corresponding to the indoor unit that makes the total refrigerant amount in the air-conditioning apparatus100to be minimum (i.e., the indoor unit that makes the reduction of the total refrigerant amount to be maximum) is changed to water.

FIG. 10is a flowchart showing a method for selecting, based on indoor volume, the medium which circulates through the indoor unit disposed in each space ofFIG. 7according to another embodiment of the present invention. The difference betweenFIG. 10andFIG. 8is only step 5. In other words, in the example ofFIG. 10, of the air-conditioned spaces exceeding the limit concentration, the circulation medium of the indoor unit corresponding to the air-conditioned space having a smallest volume is changed to water.

It should be noted that in step 5, regardless of the limit concentration, the circulation media of “the indoor unit farthest from the relay unit”, “the indoor unit that makes the reduction of the total refrigerant amount to be maximum”, and “the indoor unit corresponding to the air-conditioned space having a smallest volume” may simply be determined as water.

By using the methods as shown inFIGS. 8 to 10, it is possible to automatically determine how to selectively use a heat medium (refrigerant, water, brine, etc.) circulating through an indoor unit in installing the system, shown inFIGS. 1 to 6, in which air-conditioning with a refrigerant and air-conditioning with water or brine are performed. Thus, an effect is provided that it is possible to prevent leak of the refrigerant exceeding an allowable limit in any of the air-conditioned spaces.