GB2543206A

GB2543206A - Refrigeration cycle device

Info

Publication number: GB2543206A
Application number: GB1700157.9A
Authority: GB
Inventors: Yamashita Koji
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2014-07-31
Filing date: 2014-07-31
Publication date: 2017-04-12
Also published as: JPWO2016016999A1; GB201700157D0; WO2016016999A1

Abstract

This refrigeration cycle device (100) forms a coolant circuit by being filled with a coolant that comprises a substance having the property of causing a disproportional reaction, and a refrigerator oil that is compatible with the coolant. At least a first heat exchanger or a second heat exchanger comprises a plurality of heat-transfer pipes 43 and a header 47 or 48. The internal diameter of the header 47 or 48 is greater than the internal diameter of the heat-transfer pipe 43, and the end section on the coolant outlet side of the heat-transfer pipe 43 is disposed so as to face a pipe inner wall surface 50 of the header. The end section on the coolant outlet side of the heat-transfer pipe 43 is located at a position such that the value of L/d is less than 20 and greater than 0 if the distance from the center 45 or 46 of the end section on the coolant outlet side of the heat-transfer pipe 43 to the pipe inner wall surface 50 of the header corresponding to the center 45 or 46 is the distance L and the inner diameter or equivalent diameter at the end section on the coolant outlet side of the heat-transfer pipe 43 is the inner diameter d.

Description

DESCRIPTION Title of Invention REFRIGERATION CYCLE APPARATUS Technical Field [0001]

The present invention relates to a refrigeration cycle apparatus, such as an air-conditioning apparatus, for use as, for example, a building-use multi-air-conditioning apparatus.

Background Art [0002] A refrigeration cycle apparatus that includes a refrigerant circuit for circulating refrigerant to perform operations including air conditioning, such as a building-use multi-air-conditioning apparatus, generally uses, as refrigerant, substances containing hydrogen and carbon such as R410A, which is nonflammable, and propane, which is flammable. The life span of such substances, when the substances are discharged into the air, until they are decomposed in the air and transformed into another substance varies. However, inside a refrigeration cycle apparatus, such substances remain highly stable and thus are usable as refrigerant as long as several decades.

[0003]

Some of substances each containing hydrogen and carbon have low stability even in a refrigeration cycle apparatus and are not suitable for use as refrigerant. Examples of such substances having low stability include a substance that has a property of causing a disproportionation reaction. Disproportionation is a property with which a substance reacts with a substance of the same type and is transformed into a different substance. For example, when a strong energy is applied to refrigerant while adjacent portions of a substance in a liquid or other phase are located very close to each other, this energy causes a disproportionation reaction, in which the adjacent portions of the substance react with each other and are transformed into a different substance. When a disproportionation reaction occurs, heat is generated and temperature rises sharply, possibly causing a sharp pressure rise. For example, when a substance that has a property of causing a disproportionation reaction is used as refrigerant for a refrigeration cycle apparatus and enclosed in a pipe made of a material such as copper, the pipe may be broken as a result of a failure to bear the pressure rise of the refrigerant inside, or other accident may occur. Known examples of substances having a property of causing a disproportionation reaction include 1,1,2-trifluoroethylene (HFO-1123) and acetylene.

[0004] A heating cycle system (refrigeration cycle apparatus) that uses 1,1,2-trifluoroethylene (HFO-1123) as a heating-cycle operation medium has been developed (for example, Patent Literature 1).

Citation List Patent Literature [0005]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2014-098166 (Fig. 1 and other part)

Summary of Invention Technical Problem [0006]

Patent Literature 1 describes use of 1,1,2-trifluoroethylene (HFO-1123) as a heating-cycle operation medium in a refrigeration cycle apparatus such as a heating cycle system. 1,1,2-trifluoroethylene (HFO-1123) is a substance having a property of causing a disproportionation reaction. When 1,1,2-trifluoroethylene is used as refrigerant as it is, a disproportionation reaction may occur due to certain energy in an area inside a refrigerant circuit where a substance in a liquid state flows while adjacent portions of a substance in a liquid, two-phase, or other form are located very close to each other. When the adjacent portions of the substance cause a disproportionation reaction, the substance is transformed into a different substance and no longer serves as refrigerant. Besides, a sharp pressure rise in the refrigerant circuit may cause an accident such as a pipe burst. Thus, to use a substance having a property of causing a disproportionation reaction as refrigerant, an occurrence of a disproportionation reaction has to be prevented. To this end, a device that prevents an occurrence of a disproportionation reaction is required. However, none of documents including Patent Literature 1 describes a method for developing an apparatus or device that prevents an occurrence of a disproportionation reaction.

[0007]

The present invention is made to solve the above-described problem and to obtain a refrigeration cycle apparatus that can reduce energy that refrigerant receives from the exterior and that can safely use a substance having a property of causing a disproportionation reaction as refrigerant.

Solution to Problem [0008] A refrigeration cycle apparatus of one embodiment of the present invention includes a refrigerant circuit connecting, by a refrigerant pipe, a compressor, a first heat exchanger, an expansion device, and a second heat exchanger. The refrigerant circuit is filled with single component refrigerant constituted of a substance having a property of causing a disproportionation reaction or mixed refrigerant containing a substance having a property of causing a disproportionation reaction and refrigerating machine oil miscible with the refrigerant. At least one of the first heat exchanger and the second heat exchanger includes heat-transmitting pipes through which the refrigerant flows, and a header into which an end portion of each of the heat-transmitting pipes on a refrigerant outlet side is inserted and through which the refrigerant flows. The header has an inner diameter larger than an inner diameter of each of the heat-transmitting pipes and the end portion of each of the heat-transmitting pipes on the refrigerant outlet side is disposed to face an in-pipe wall surface of the header. The end portion of each of the heat-transmitting pipes on the refrigerant outlet side is disposed at a position at which a value L/d is under 20 and over 0, where a distance from a center of the end portion of each of the heat-transmitting pipes on the refrigerant outlet side to a portion of the in-pipe wall surface of the header facing to the center is denoted with L and the inner diameter of the end portion of each of the heat-transmitting pipes on the refrigerant outlet side or an equivalent diameter corresponding to the inner diameter is denoted with d. Advantageous Effects of Invention [0009]

In a refrigeration cycle apparatus according to one embodiment of the present invention, when a refrigerant circuit is formed and uses a substance having a property of causing a disproportionation reaction such as 1,1,2-trifluoroethylene (HFO-1123) as refrigerant, a disproportionation reaction is rendered less likely to occur by, for example, adjusting an impact imposed on an in-pipe wall surface of a header from a heat-transmitting pipe. Thus, the substance having a property of causing a disproportionation reaction is prevented from being rendered unusable as refrigerant or from causing an accident such as a pipe burst. Thus, an apparatus that can secure safe use of the substance as refrigerant can be obtained.

Brief Description of Drawings [0010] [Fig. 1] Fig. 1 is a schematic diagram of an example of how a refrigeration cycle apparatus according to Embodiment 1 of the present invention is installed.

[Fig. 2] Fig. 2 is a circuit configuration diagram of an example of a circuit configuration of the refrigeration cycle apparatus according to Embodiment 1 of the present invention.

[Fig. 3] Fig. 3 is a refrigerant circuit diagram illustrating a flow of refrigerant while the refrigeration cycle apparatus according to Embodiment 1 of the present invention is in a cooling operation mode.

[Fig. 4] Fig. 4 is a refrigerant circuit diagram illustrating a flow of refrigerant while the refrigeration cycle apparatus according to Embodiment 1 of the present invention is in a heating operation mode.

[Fig. 5] Fig. 5 is a chart of the solubility of a refrigerating machine oil in the refrigeration cycle apparatus according to Embodiment 1 of the present invention.

[Fig. 6] Fig. 6 is a schematic diagram of a configuration of a heat exchanger used as, for example, a heat-source-side heat exchanger 12 or a load-side heat exchanger 15 according to Embodiment 1 of the present invention.

[Fig. 7] Fig. 7 is a sectional view illustrating the relationship between a header 47 and a heat-transmitting pipe 43 included in the heat exchanger of the refrigeration cycle apparatus according to Embodiment 1 of the present invention.

[Fig. 8] Fig. 8 is a schematic diagram of a different configuration of a heat exchanger of the refrigeration cycle apparatus according to Embodiment 1 of the present invention.

[Fig. 9] Fig. 9 is a schematic diagram of a different configuration of a heat exchanger of the refrigeration cycle apparatus according to Embodiment 1 of the present invention.

[Fig. 10] Fig. 10 is a schematic diagram of a heat-transmitting pipe included in the heat exchanger of the refrigeration cycle apparatus according to Embodiment 1 of the present invention.

[Fig. 11] Fig. 11 is a circuit configuration diagram of a refrigeration cycle apparatus according to Embodiment 2 of the present invention.

Description of Embodiments [0011]

With reference to the drawings and other parts, a refrigeration cycle apparatus according to each embodiment of the present invention is described below. In the drawings including Fig. 1, components denoted with the same reference signs are the same or equivalent to each other and are the same throughout the embodiments described below. The form of each component described in the entirety of the description is described merely exemplarily and the present invention is not limited to the form described in the description. In particular, a combination of components is not limited to the combination in the embodiments. Components described in an embodiment are usable in a different embodiment. In some cases, multiple devices or components of the same type that are distinguished by appended characters may be denoted with signs without the appended characters when they do not particularly need to be distinguished from one another or specified. Throughout the drawings, the dimensional relationship between components may differ from the actual dimensional relationship. Whether a parameter such as temperature and pressure is high or low is not particularly determined by the relationship between the parameter and an absolute value but is relatively determined in, for example, the state or an operation of a system, a device, or an apparatus.

[0012]

Embodiment 1

With reference to the drawings, Embodiment 1 of the present invention is described below. Fig. 1 is a schematic diagram of an example of how a refrigeration cycle apparatus according to Embodiment 1 of the present invention is installed.

The refrigeration cycle apparatus illustrated in Fig. 1 includes a refrigeration circuit in which refrigerant is circulated and is capable of selecting a cooling mode or a heating mode as an operation mode with the use of a refrigeration cycle including the refrigerant. The refrigeration cycle apparatus according to Embodiment 1 is described with an example where an air-conditioning apparatus that performs air conditioning of an air-conditioned space (indoor space 7).

[0013]

In Fig. 1, the refrigeration cycle apparatus according to Embodiment 1 includes an outdoor unit 1, which is a heat source device, and multiple indoor units 2. The outdoor unit 1 and each of the indoor units 2 are connected to each other with an extension pipe (refrigerant pipe) 4 that allows refrigerant to flow through the extension pipe 4. Cooling energy or heating energy generated in the outdoor unit 1 is delivered to the indoor units 2 through the extension pipes 4.

[0014]

The outdoor unit 1 is usually installed in an outdoor space 6, which is a space (such as a rooftop) outside a structure 9 such as a building, and supplies cooling energy or heating energy to the indoor units 2. The indoor units 2 supply cooling air or heating air to an indoor space 7, which is a space (such as a living room) inside the structure 9 and which is an air-conditioned space, and are installed at positions at which they can supply temperature-conditioned air to the indoor space 7.

[0015]

As illustrated in Fig. 1, in the refrigeration cycle apparatus according to Embodiment 1, the outdoor unit 1 and indoor units 2 are connected together using two extension pipes 4.

[0016]

Fig. 1 illustrates a case where the indoor unit 2 is a ceiling cassette unit as an example; however, the indoor unit 2 is not limited to a ceiling cassette unit. The indoor unit 2 may be of any type including a ceiling embedded unit and a ceiling suspended unit as long as it can blow heating air or cooling air into the indoor space 7 directly or through ducts or other members.

[0017]

Fig. 1 illustrates a case where the outdoor unit 1 is installed in the outdoor space 6 as an example; however, the outdoor unit 1 is not limited to be installed in the outdoor space 6. For example, the outdoor unit 1 may be installed in an enclosed space, such as a machine room having a ventilation hole. Alternatively, the outdoor unit 1 may be installed inside the structure 9 as long as waste heat can be discharged to the outside of the structure 9 through a ventilation duct. Still alternatively, when a water-cooled outdoor unit is used as the outdoor unit 1, the outdoor unit 1 may be installed inside the structure 9. Wherever the outdoor unit 1 is installed, particular problems do not occur.

[0018]

The number of outdoor units 1 and the number of indoor units 2 connected to one another are not limited to the numbers illustrated in Fig. 1. Each number of units may be determined depending on the structure 9 in which the refrigeration cycle apparatus according to Embodiment 1 is installed.

[0019]

Fig. 2 is a circuit configuration diagram of an example of a refrigerant circuit configuration of the refrigeration cycle apparatus (hereinafter referred to as a refrigeration cycle apparatus 100) according to Embodiment 1. With reference to Fig. 2, the detailed configuration of the refrigeration cycle apparatus 100 is described. As illustrated in Fig. 2, the outdoor unit 1 and the indoor units 2 are connected to one another with the extension pipes (refrigerant pipes) 4 through which refrigerant flows.

[0020] [Outdoor Unit 1]

The outdoor unit 1 includes a compressor 10, a first refrigerant-flow switching device 11, such as a four-way valve, a heat-source-side heat exchanger 12, and an accumulator 19, which are connected together in series with refrigerant pipes.

[0021]

The compressor 10 sucks and compresses refrigerant into high-temperature high-pressure refrigerant, and discharges the refrigerant.

For example, a low-pressure shell construction or a high-pressure shell construction is used as the compressor 10. The low-pressure shell construction includes a tightly-closed container having a compression chamber and the inside of the tightly-closed container is in a low-pressure refrigerant-pressure atmosphere.

The low-pressure shell construction is for sucking and compressing low-pressure refrigerant in the tightly-closed container. The high-pressure shell construction includes a tightly-closed container, the inside of which is in a high-pressure refrigerant-pressure atmosphere. The high-pressure shell construction is for discharging high-pressure refrigerant compressed in a compression chamber into the tightly-closed container. The compressor 10 according to Embodiment 1 may be preferably, for example, an inverter compressor whose capacity is controllable. The first refrigerant-flow switching device 11 switches a flow of refrigerant between a flow of refrigerant in a heating operation and a flow of refrigerant in a cooling operation. The heat-source-side heat exchanger 12, which is a first heat exchanger, serves as an evaporator during the heating operation and serves as a condenser (or a radiator) during the cooling operation. The heat-source-side heat exchanger 12 causes air fed from a fan (not illustrated) and the refrigerant to exchange heat between each other and evaporates and gasifies or condenses and liquefies the refrigerant. The heat-source-side heat exchanger 12 serves as a condenser during an operation of cooling the indoor space 7. The heat-source-side heat exchanger 12 serves as an evaporator during an operation of heating the indoor space 7. The accumulator 19 is disposed on a suction side of the compressor 10. The accumulator 19 accumulates an excess of the refrigerant in the refrigerant circuit resulting from, for example, a change of the operation mode.

[0022]

The outdoor unit 1 also includes a high-pressure detecting device 37, a low-pressure detecting device 38, and a controller 60. The controller 60 controls devices on the basis of, for example, information detected by each detecting device or commands from a remote controller. For example, the controller 60 controls the driving frequency of the compressor 10, the rotation speed (including on-off control) of the fan, switching of the first refrigerant-flow switching device 11, and other operations to perform each operation mode, described below. The controller 60 according to Embodiment 1 is formed from, for example, a microcomputer including a control processing unit such as a central processing unit (CPU). The controller 60 also includes a storage device (not illustrated) that contains data of a procedure related to, for example, controlling as a program. The control processing unit performs controlling by executing processing based on the program data. The high-pressure detecting device 37 is disposed, in the refrigerant circuit, on a pipe on the discharge side of the compressor 10 that has a high pressure. The low-pressure detecting device 38 is disposed, in the refrigerant circuit, on a pipe on the refrigerant inflow side of the accumulator 19 that has a low pressure. The high-pressure detecting device 37 and the low-pressure detecting device 38 each transmit a signal based on the detected pressure to the controller 60. The controller 60 processes the transmitted signal and controls each device of the outdoor unit 1 on the basis of the detected pressure.

[0023] [Indoor Unit 2]

Each indoor unit 2 includes a load-side heat exchanger 15, which is a second heat exchanger. The load-side heat exchanger 15 is connected to the outdoor unit 1 through the extension pipe 4. The load-side heat exchanger 15 causes air fed from a fan (not illustrated) and the refrigerant to exchange heat between each other to generate heating air or cooling air that is to be supplied to the indoor space 7. The load-side heat exchanger 15 serves as a condenser in the operation of heating the indoor space 7. The load-side heat exchanger 15 serves as an evaporator in the operation of cooling the indoor space 7. Although the illustration is omitted, each indoor unit 2 includes a controller that controls each device in the indoor unit 2.

[0024]

Fig. 2 illustrates a case where four indoor units 2 are connected to the outdoor unit 1 as an example and the four indoor units 2 are illustrated as an indoor unit 2a, an indoor unit 2b, an indoor unit 2c, and an indoor unit 2d in order from the lower side of Fig. 2. Corresponding to the indoor unit 2a to the indoor unit 2d, the load-side heat exchangers 15 are also illustrated as a load-side heat exchanger 15a, a load-side heat exchanger 15b, a load-side heat exchanger 15c, and a load-side heat exchanger 15d in order from the lower side of Fig. 2. As in the case of Fig. 1, the number of indoor units 2 connected is not limited to four, illustrated in Fig. 2.

[0025]

Each operation mode performed by the refrigeration cycle apparatus 100 is described below. On the basis of a command from each indoor unit 2, the refrigeration cycle apparatus 100 determines the operation mode of the outdoor unit 1 as a cooling operation mode or a heating operation mode. Specifically, the refrigeration cycle apparatus 100 is capable of operating all the indoor units 2 in the same operation (either the cooling operation or the heating operation) to adjust the temperature in the indoor space. In any of the cooling operation mode and the heating operation mode, each indoor unit 2 can be freely operated or stopped.

[0026]

The operation mode that the refrigeration cycle apparatus 100 performs includes a cooling operation mode, in which all the indoor units 2 in active perform (or stop) the cooling operation, and a heating operation mode, in which all the indoor units 2 in active perform (or stop) the heating operation. Each operation mode and its flow of refrigerant are described below.

[0027] [Cooling Operation Mode]

Fig. 3 is a refrigerant circuit diagram illustrating a flow of refrigerant while the refrigeration cycle apparatus 100 is in the cooling operation mode. The cooling operation mode is described with an example where a cooling energy load is generated in all the load-side heat exchangers 15 in Fig. 3. In Fig. 3, pipes drawn with bold lines represent pipes through which refrigerant flows and the directions in which the refrigerant flows are represented with solid arrows.

[0028]

When the operation is to be performed in the cooling operation mode as illustrated in Fig. 3, the controller 60 in the outdoor unit 1 switches the first refrigerant-flow switching device 11 so that the refrigerant discharged from the compressor 10 flows into the heat-source-side heat exchanger 12. Then, the low-temperature low-pressure refrigerant is compressed by the compressor 10 and transformed into high-temperature high-pressure gaseous refrigerant, and the high-temperature high-pressure gaseous refrigerant is then discharged. The high-temperature high-pressure gaseous refrigerant discharged from the compressor 10 flows through the first refrigerant-flow switching device 11 and then into the heat-source-side heat exchanger 12. Then, the refrigerant flowing into the heat-source-side heat exchanger 12 is condensed and liquefied in the heat-source-side heat exchanger 12 while radiating heat to the outdoor air. The refrigerant is then transformed into high-pressure liquid refrigerant and flows out of the outdoor unit 1.

[0029]

The high-pressure liquid refrigerant flowing out of the outdoor unit 1 flows through the extension pipe 4 and into each of the indoor units 2 (2a to 2d). The high-pressure liquid refrigerant flowing into each of the indoor units 2 (2a to 2d) flows into an expansion device 16 (16a to 16d) and is then throttled by the expansion device 16 (16a to 16d). Thus, the pressure of the refrigerant is reduced and the refrigerant is transformed into low-temperature low-pressure two-phase refrigerant and flows out. The refrigerant passing through the expansion device 16 (16a to 16d) flows into the corresponding load-side heat exchanger 15 (15a to 15d) serving as an evaporator, receives heat from the air circulating around the load-side heat exchanger 15, and is transformed into low-temperature low-pressure gaseous refrigerant. The low-temperature low-pressure gaseous refrigerant flows out from the indoor unit 2 (2a to 2d), flows into the outdoor unit 1 again through the extension pipe 4, passes through the first refrigerant-flow switching device 11, and is then sucked again into the compressor 10 through the accumulator 19.

[0030]

At this time, the opening degree (open area) of each of the expansion devices 16a to 16d is so controlled that a temperature difference (degree of superheat) between the temperature detected by a load-side-heat-exchanger gaseous-refrigerant-temperature detecting device 28 and an evaporating temperature transmitted via telecommunication from the controller 60 of the outdoor unit 1 to the controller (not illustrated) of the corresponding indoor unit 2 is approximated to a target value.

[0031]

In the above-described case, all the indoor units 2 are assumed to perform the cooling operation. However, when the cooling operation mode is performed and one or more of the load-side heat exchangers 15 have no heat load (including one or more in a thermo-off state), the refrigerant does not have to be caused to flow to the one or more of the load-side heat exchangers 15 having no heat load. Thus, the corresponding indoor unit 2 stops its operation. At this time, the expansion device 16 corresponding to the inactive indoor unit 2 is entirely closed or closed to such an opening degree as not to allow the refrigerant to flow through the indoor unit 2.

[0032] [Heating Operation Mode]

Fig. 4 is a refrigerant circuit diagram illustrating a flow of refrigerant while the refrigeration cycle apparatus 100 is in the heating operation mode. The heating operation mode is described with an example where a heating energy load is generated in all the load-side heat exchangers 15 in Fig. 4. In Fig. 4, pipes drawn with bold lines represent pipes through which refrigerant flows and the directions in which the refrigerant flows are represented with solid arrows.

[0033]

When the operation is to be performed in the heating operation mode as illustrated in Fig. 4, the controller 60 in the outdoor unit 1 switches the first refrigerant-flow switching device 11 so that the refrigerant discharged from the compressor 10 flows into each indoor unit 2 without passing through the heat-source-side heat exchanger 12. The low-temperature low-pressure refrigerant is compressed by the compressor 10 and is then discharged as high-temperature high-pressure gaseous refrigerant. Then, the high-temperature high-pressure gaseous refrigerant passes through the first refrigerant-flow switching device 11 and flows out of the outdoor unit 1. The high-temperature high-pressure gaseous refrigerant flowing out of the outdoor unit 1 flows into each indoor unit 2 (2a to 2d) through the extension pipe 4. The high-temperature high-pressure gaseous refrigerant flowing into each indoor unit 2 (2a to 2d) flows into the corresponding load-side heat exchanger 15 (15a to 15d), is condensed and liquefied while radiating heat to the air circulating around the load-side heat exchanger 15 (15a to 15d) and transformed into high-temperature high-pressure liquid refrigerant. The high-temperature high-pressure liquid refrigerant flowing out of the load-side heat exchanger 15 (15a to 15d) flows into the expansion device 16 (16a to 16d) and is then throttled by the expansion device 16 (16a to 16d). Thus, the pressure of the refrigerant is reduced and the refrigerant is transformed into low-temperature low-pressure two-phase refrigerant and flows out of the indoor unit 2 (2a to 2d). The low-temperature low-pressure two-phase refrigerant flowing out of the indoor unit 2 flows into the outdoor unit 1 again through the extension pipe 4.

[0034]

At this time, the opening degree (open area) of each of the expansion devices 16a to 16d is so controlled that a temperature difference (degree of subcooling) between a condensing temperature transmitted via telecommunication from the controller 60 of the outdoor unit 1 to the controller (not illustrated) of the corresponding indoor unit 2 and the temperature detected by a load-side-heat-exchanger liquid-refrigerant-temperature detecting device 27 is approximated to a target value.

[0035]

The low-temperature low-pressure two-phase refrigerant flowing into the outdoor unit 1 flows into the heat-source-side heat exchanger 12, receives heat from the air flowing around the heat-source-side heat exchanger 12, evaporates, and is transformed into low-temperature low-pressure gaseous refrigerant or low-temperature low-pressure two-phase refrigerant having a high quality (dryness). The low-temperature low-pressure gaseous refrigerant or two-phase refrigerant is sucked again into the compressor 10 via the first refrigerant-flow switching device 11 and the accumulator 19.

[0036]

When the heating operation mode is performed and one or more of the load-side heat exchangers 15 have no heat load (including one or more in a thermo-off state), the refrigerant does not have to be caused to flow to the one or more of the load-side heat exchangers 15 having no heat load. If, however, in the heating operation mode, the expansion device 16 corresponding to the load-side heat exchanger 15 having no heat load is entirely closed or closed to such an opening degree as not to allow the refrigerant to flow through the load-side heat exchanger 15, the refrigerant may be cooled by the ambient air and accumulated inside the load-side heat exchanger 15 of the inactive indoor unit 2, and the refrigerant circuit may be short of the refrigerant as a whole. Thus, in the heating operation, the opening degree (open area) of the expansion device 16 corresponding to the load-side heat exchanger 15 having no heat load is determined to be a full opening degree or an opening degree large enough to prevent accumulation of the refrigerant.

[0037]

As described above, in the refrigeration cycle apparatus 100, the heat-source-side heat exchanger 12 serves as a condenser when the indoor units 2 perform the cooling operation. At this time, high-temperature high-pressure gaseous refrigerant flows into the heat-source-side heat exchanger 12, and is condensed into two-phase refrigerant. Subsequently, the refrigerant is liquefied, and then flows out in the form of high-temperature high-pressure liquid refrigerant. On the other hand, the load-side heat exchangers 15 (15a to 15d) serve as condensers when the indoor units 2 perform the heating operation. At this time, high-temperature high-pressure gaseous refrigerant flows into each load-side heat exchanger 15 (15a to 15d), and is condensed into two-phase refrigerant. Subsequently, the refrigerant is liquefied, and then flows out in the form of high-temperature high-pressure liquid refrigerant.

[0038] [Types of Refrigerant]

In the case where a substance typically used as refrigerant, such as R32 and R410A, is used as refrigerant in the refrigeration cycle apparatus 100, the substance may be normally used as it is without taking a measure to improve the stability of the refrigerant inside the refrigerant circuit. However, in this case, single component refrigerant constituted of a substance having a property of causing a disproportionation reaction, such as 1,1,2-trifluoroethylene (HFO-1123) expressed as C2H1F3 and having one double bond in its molecular structure, or mixed refrigerant in which a different substance is mixed into the substance having a property of causing a disproportionation reaction is used as refrigerant. The refrigerant containing HFO-1123 is not the only possible refrigerant. Any refrigerant containing a substance having a property of causing a disproportionation reaction can be refrigerant that is to be used in the refrigeration cycle apparatus according the invention.

[0039]

Examples of a substance that is to be mixed into the substance having a property of causing a disproportionation reaction to form mixed refrigerant include tetrafluoropropene expressed by the chemical formula of C3H2F4 (such as HFO- 1234yf, which is 2,3,3,3-tetrafluoropropene expressed as CF3CF=CH2, and HFO-1234ze, which is 1,3,3,3-tetrafluoro-1-propene expressed as CF3CH=CHF) and difluoromethane (HFC-32) expressed by the chemical formula of CH2F2. A substance that is to be mixed into the substance having a property of causing a disproportionation reaction is not limited to these examples. For example, HC-290 (propane) or other substance may be mixed. Any substance that has a thermal property usable as refrigerant of the refrigeration cycle apparatus 100 may be used. The mixture ratio may be any mixture ratio.

[0040]

When the substance having a property of causing a disproportionation reaction is used as refrigerant as it is, the following problem would occur. For example, when a strong energy is applied to a portion at which a liquid substance exists, for example, in a liquid phase or in two phases and in which adjacent portions of the substance are located at a very short distance, the adjacent portions of the substance react with each other and are transformed into a different substance, so that the substance no longer serves as refrigerant. Besides, a sharp pressure rise due to heat generation may cause an accident such as a pipe burst. Thus, to use the substance having a property of causing a disproportionation reaction usable as refrigerant, a measure has to be taken against an occurrence of a disproportionation reaction in a liquid area in the refrigerant circuit, in which liquid refrigerant in liquid form flows, or in a two-phase area in the refrigerant circuit, in which two-phase gas-liquid refrigerant, which is a mixture of gaseous refrigerant and liquid refrigerant, flows. Collision energy at the time when the refrigerant and a structure collide against each other can be a cause of a disproportionation reaction of the refrigerant. A disproportionation reaction can thus be rendered less likely to occur when components of the refrigerant circuit are formed into a structure that reduces the collision energy.

[0041] [Refrigerating Machine Oil]

Refrigerating machine oil with which the refrigerant circuit is filled is mainly composed of either polyol ester or polyvinyl ether. The refrigerating machine oil is inserted into the compressor 10 and part of the refrigerating machine oil circulates in the refrigerant circuit together with the refrigerant. Each of polyol ester and polyvinyl ether is refrigerating machine oil having one double bond in its molecular structure and that is miscible with refrigerant. When this refrigerating machine oil and HFO-1123, serving as refrigerant, are mixed together, HFO-1123 dissolves in the refrigerating machine oil to some extent. The refrigerating machine oil is not limited to the above-described refrigerating machine oil and another type of oil may be used as long as it is miscible with refrigerant.

[0042]

Fig. 5 is a chart of the solubility of a refrigerating machine oil in the refrigeration cycle apparatus according to Embodiment 1 of the present invention. High solubility means that a large amount of refrigerant dissolves in the refrigerating machine oil and low solubility means that only a small amount of refrigerant dissolves in the refrigerating machine oil. In Fig. 5, the relationship between the solubility and the pressure is illustrated for each of refrigerant temperatures T1, T2, and T3. In Fig. 5, T1, T2, and T3 denote different temperatures and satisfy Formula (1): [0043] [Math 1] T1 <T2 <T3 ... (1) [0044]

As illustrated in Fig. 5, under the same pressure condition, refrigerant having a lower temperature has higher solubility. Under the same temperature condition, refrigerant having a higher pressure has higher solubility. When the refrigerant dissolves into the refrigerating machine oil, each molecule of the refrigerating machine oil dissolves and is interposed between molecules of the refrigerant. Thus, in the case where the refrigerant is highly soluble in the refrigerating machine oil, the refrigerating machine oil is interposed between a large number of molecules of the refrigerant. As described above, a disproportionation reaction of refrigerant is a phenomenon in which adjacent molecules of the refrigerant react with each other. Thus, by using the refrigerating machine oil that is miscible with refrigerant, a disproportionation reaction of refrigerant is rendered less likely to occur, because a molecule of the refrigerating machine oil is present between the molecules of the refrigerant.

[0045]

The refrigerant that is more soluble in the refrigerating machine oil is more effective in preventing a disproportionation reaction of the refrigerant. In practical use, a large amount of refrigerant dissolves in the refrigerating machine oil when the refrigerant has a solubility of 50 wt% (weight %) or higher, so that a disproportionation reaction can be prevented.

[0046] [Heat-source-side Heat Exchanger 12 or Load-side Heat Exchanger 15 (15a to 15d)]

Fig. 6 is a schematic diagram of a configuration of a plate-finned-tube heat exchanger used as, for example, the heat-source-side heat exchanger 12 or the load-side heat exchanger 15 (15a to 15d) according to Embodiment 1 of the present invention. In Fig. 6, the plate-finned-tube heat-source-side heat exchanger 12 or the load-side heat exchanger 15 (referred to as the heat exchanger 12 or 15, in this description) includes a first connecting pipe 41, a second connecting pipe 42, heat-transmitting pipes 43 causing an ambient heat medium such as air, and refrigerant inside the heat-transmitting pipes 43 to exchange heat between each other, fins 44, a first header 47, and a second header 48.

[0047]

The configuration of the heat exchanger 12 or 15 is described further in detail. The heat exchanger 12 or 15 has a configuration in which multiple fins 44 are disposed and spaced apart from one another and multiple heat-transmitting pipes 43 are disposed to extend through these multiple fins 44. One of two ends of each of the heat-transmitting pipes 43 is connected to the first header 47 and the other end of each of the heat-transmitting pipes 43 is connected to the second header 48. The first connecting pipe 41 and the second connecting pipe 42, which serve as an inlet and an outlet of refrigerant from and to a device outside the refrigerant circuit, are respectively connected to the first header 47 and the second header 48.

[0048]

The first header 47 or the second header 48 distributes refrigerant flowing in from the first connecting pipe 41 or the second connecting pipe 42 to each heat-transmitting pipe 43. The first header 47 or the second header 48 is also configured to cause parts of the refrigerant flowing in from different heat-transmitting pipes 43 to merge with one another. Fig. 6 shows the configuration including one first header 47 and one second header 48 and the same number of heat-transmitting pipes 43 are connected to the first header 47 and the second header 48.

[0049]

In Fig. 6, solid arrows represent the directions in which the refrigerant flows when the heat exchanger 12 or 15 serves as a condenser and dashed arrows represent the directions in which the refrigerant flows when the heat exchanger 12 or 15 serves as an evaporator. The directions represented by the arrows are the same in Fig. 8 and Fig. 9, described below.

[0050]

When the heat exchanger 12 or 15 serves as a condenser, high-temperature high-pressure gaseous refrigerant flows into the heat exchanger 12 or 15. The high-temperature high-pressure gaseous refrigerant flowing into the heat exchanger 12 or 15 from the first connecting pipe 41 is distributed by the first header 47 and flows into each heat-transmitting pipe 43. The refrigerant exchanges heat with, for example, ambient air with the effects of the heat-transmitting pipes 43 and the fins 44. The refrigerant is then condensed, transformed into refrigerant of the two-phase state, in which gas and liquid are mixed, and liquefied. Then, the refrigerant transformed into high-temperature high-pressure liquid refrigerant, flows out of the heat-transmitting pipes 43, merges in the second header 48, and flows out to the second connecting pipe 42.

[0051]

On the other hand, when the heat exchanger 12 or 15 serves as an evaporator, low-temperature low-pressure two-phase refrigerant flows into the heat exchanger 12 or 15. The low-temperature low-pressure two-phase refrigerant flowing into the heat exchanger 12 or 15 from the second connecting pipe 42 is distributed by the second header 48 and flows into each heat-transmitting pipe 43. The refrigerant exchanges heat with, for example, ambient air with the effects of the heat-transmitting pipes 43 and the fins 44 and evaporates. The two-phase refrigerant increases in quality and is transformed into low-temperature low-pressure two-phase refrigerant or gaseous refrigerant having a high quality. The refrigerant then flows out of the heat-transmitting pipes 43, merges in the first header 47, and flows out to the first connecting pipe 41.

[0052]

When the flow rate of the refrigerant flowing through the heat-transmitting pipes 43 in the heat exchanger 12 or 15 increases to an excessive level, a pressure loss of the refrigerant in the heat-transmitting pipes 43 increases to an excessive level. An allowable flow rate of the refrigerant for each inner diameter of one heat-transmitting pipe 43 is limitative. When the heat-transmitting pipes 43 are thin, the number of heat-transmitting pipes 43 thus needs to be increased to cause the refrigerant to flow at the same flow rate as that in the case where the heat-transmitting pipes 43 are thick. The heat exchanger 12 or 15 including thinner heat-transmitting pipes 43 has higher performance because the heat-transmitting pipes 43 have a larger heat transfer area for each flow rate of refrigerant flowing through the heat exchanger 12 or 15. Thus, the heat exchanger 12 or 15 usually includes heat-transmitting pipes 43 having as a small outer diameter as, for example, 7 mm or 5 mm. When thin heat-transmitting pipes 43 are used, the heat exchanger 12 or 15 needs to include multiple heat-transmitting pipes 43 and to distribute the refrigerant flowing from the first connecting pipe 41 or the second connecting pipe 42 (in this description, referred to as the connecting pipe 41 or 42) to the multiple heat-transmitting pipes 43 or to cause the refrigerant to merge. Although several ways are conceivable to distribute the refrigerant or cause the refrigerant to merge, a commonly used way is to use the first header 47 or the second header 48 (in this description, referred to as the header 47 or 48) because this configuration produces a small pressure loss and is formed at low cost. The header 47 or 48 is connected to the multiple heat-transmitting pipes 43 to distribute the refrigerant or cause the refrigerant to merge. The header 47 or 48 is usually formed of a cylindrical pipe thicker than the heat-transmitting pipes 43. However, the header 47 or 48 may have any structure as long as it can distribute the refrigerant to the multiple heat-transmitting pipes 43 or cause the refrigerant to merge. For example, the header 47 or 48 may have a rectangular or elliptical cross section. The header 47 or 48 may be made of a material such as copper and aluminium.

Any header 47 or 48 suffices as long as it is strong enough to bear the pressure imposed when the refrigerant flows in and out.

[0053]

Fig. 7 is a cross-sectional view illustrating the relationship between the header 47 or 48 and the heat-transmitting pipes 43 used in a heat exchanger of the refrigeration cycle apparatus according to Embodiment 1 of the present invention. Multiple heat-transmitting pipes 43 are inserted into the header 47 or 48. Since Fig. 7 is a cross-sectional view, the heat-transmitting pipes 43 seem to be a single pipe, but the heat-transmitting pipes 43 are superposed in a direction perpendicular to the plane of Fig. 7. Actually, multiple heat-transmitting pipes 43 are connected to the single header 47 or 48.

[0054]

As described above, high-pressure liquid-state refrigerant flows into the second header 48 when the heat exchanger 12 or 15 serves as a condenser. On the other hand, low-pressure two-phase-state refrigerant may flow into the first header 47 when the heat exchanger 12 or 15 serves as an evaporator. The inner diameter of the header 47 or 48 is larger than the outer diameter of each heat-transmitting pipe 43. Holes are bored in the side surface of the header 47 or 48 and the heat-transmitting pipes 43 are inserted into the holes. The header 47 or 48 and the heat-transmitting pipes 43 are then fastened to each other by, for example, soldering. The refrigerant flowing into the header 47 or 48 has an inertial force. Thus, the refrigerant collides against a portion of an in-pipe wall surface (inner surface) 50 of the header 47 or 48, opposing to a center 45 or 46 of an outlet (refrigerant outlet port) of each heat-transmitting pipe 43, so that the direction in which the refrigerant flows is changed into directions approximately perpendicular to the original direction. If the refrigerant flowing into the header 47 or 48 has large collision energy when the refrigerant collides against the inner surface 50 of the header 47 or 48, the collision energy may cause a disproportionation reaction of a substance having a property of causing a disproportionation reaction. Thus, in Embodiment 1, the range of refrigerants that are to be used is limited (refrigerating machine oil having miscibility is used) to minimize a disproportionation reaction.

[0055]

The collision energy generated when the refrigerant and the inner surface 50 of the header 47 or 48 collide against each other is calculated by Formula (2): [0056] [Math 2]

Collision energy = mass of refrigerant x speed change of refrigerant = (mass flow rate of refrigerant χ unit time) χ speed change of refrigerant... (2) [0057]

As described above, a disproportionation reaction is a property in which portions of a substance react with each other and are transformed into a different substance. A disproportionation reaction is likely to occur when adjacent portions of the substance, such as liquid components of the liquid state or two-phase state, are located at a very short distance and receive a strong energy from the outside. On the other hand, the distance between molecules of the refrigerant in the gaseous state is much longer than that in the case where the refrigerant is in the liquid state. Thus, in the gaseous state, the refrigerant is less likely to cause a disproportionation reaction even when the refrigerant contains a large amount of HFO-1123, which is a substance having a property of causing a disproportionation reaction.

[0058]

The behavior of a jet of the refrigerant that flows into the header 47 or 48 from the pipe is studied below. In fluid dynamics, the following is generally known, when the length of the inner diameter of the pipe is denoted by d (mm) and the distance from the outlet of the pipe to the collision surface against which the jet that flows out of the outlet collides is denoted by L (mm). For example, when a value obtained by dividing the distance L by the inner diameter d (L/d) is under a predetermined value, the jet has a large turbulence component. When the value (L/d) is larger than or equal to the predetermined value, the jet has no turbulence component and flows completely stably. The predetermined value is also widely known to be from 20 to 30. Thus, when the value (L/d) is under 20, the jet still has turbulence. When the inner diameter d and the distance L are applied to the heat-transmitting pipe 43 and the portion of the inner surface 50 of the header 47 or 48 opposing to each heat-transmitting pipe 43, the inner diameter d denotes the inner diameter of the heat-transmitting pipe 43, as illustrated in Fig. 7. The distance L denotes the distance from the center 45 or 46 of the outlet of each heat-transmitting pipe 43 to the portion of the inner surface 50 of the header 47 or 48, opposing to the center 45 or 46 of the outlet of the heat-transmitting pipe 43.

[0059]

As described above, when the refrigerant having a property of causing a disproportionation reaction and refrigerating machine oil miscible with the refrigerant are mixed with each other, a molecule of the refrigerating machine oil is interposed between molecules of the refrigerant, so that a disproportionation reaction is less likely to occur. Thus, in the case where the heat exchanger 12 or 15 serves as a condenser, even when the refrigerant in the liquid state flowing out of each heat-transmitting pipe 43 collides against the inner surface 50 of the second header 48 and the refrigerant colliding against the inner surface 50 has turbulence, the collision is less likely to cause a disproportionation reaction. Also in the case where the heat exchanger 12 or 15 serves as an evaporator, a disproportionation reaction is similarly less likely to occur even when the refrigerant in the two-phase state flowing out of each heat-transmitting pipe 43 collides against the inner surface 50 of the first header 47. Thus, when the refrigerant circuit is filled with the refrigerating machine oil having miscibility, the liquid refrigerant or the two-phase refrigerant is less likely to cause a disproportionation reaction as a result of collision against the inner surface 50 even when the center 45 or 46 of each outlet of the heat-transmitting pipe 43 is located at the position at which a jet has turbulence, such as a position of the inner surface 50 of the header 47 or 48 at which the value (L/d) is under 20 and over 0.

[0060]

For example, a case is assumed where the header 47 or 48 has an inner diameter of 17.05 mm, each heat-transmitting pipe 43 has an inner diameter of 7.44 mm, and the center 45 or 46 of the outlet of each heat-transmitting pipe 43 is connected to a position at which it comes into contact with the inner surface of the header 47 or 48. In this case, the distance L denotes the inner diameter of the header 47 or 48, d denotes the inner diameter of the heat-transmitting pipe 43, and the value (L/d) is 2.3. Thus, the value is far smaller than 20 to 30 and the refrigerant still has a remarkably large turbulence component.

[0061]

Apparatuses such as a building-use multi-air-conditioning apparatus usually control the frequency of the compressor 10 or the rotation speed of a fan (not illustrated) attached to the heat-source-side heat exchanger 12 to control the condensing temperature, which is the temperature of the refrigerant inside the condenser, to be approximately 50 degrees C. Apparatuses also control the expansion device 16 so that the degree of subcooling of the refrigerant at the outlet of the condenser is approximately 10 degrees C. When the condensing temperature is approximately 50 degrees C, the refrigerant of approximately 40 degrees C flows out from the outlet of the condenser. The refrigerant that flows into the second header 48 thus has a temperature of approximately 40 degrees C and a pressure of a saturation pressure at 50 degrees C.

[0062]

When the control performance (transient characteristic) of the expansion device 16 is also considered, the refrigerant that flows into the second header 48 has a temperature within the range of approximately 40 to 50 degrees C and a pressure of a saturation pressure at 50 degrees C. When the refrigerant has the above-described temperature and pressure and the refrigerant has high solubility in the refrigerating machine oil, the refrigerant is less likely to cause a disproportionation reaction. In practice, when the refrigerant has the above-described temperature and pressure and the solubility of the refrigerant in the refrigerating machine oil is higher than or equal to 50 wt% (weight percent), a large amount of refrigerant is dissolved in the refrigerating machine oil, so that a disproportionation reaction can be minimized.

In other words, in the state where the refrigerant that flows into the second header 48 is dissolved in the refrigerating machine oil at a solubility, in the refrigerating machine oil, of higher than or equal to 50 wt% (weight percent), a disproportionation reaction is less likely to occur even when the refrigerant is ejected from a remarkably close position, such as a position at which the value of (L/d) is under 10, and collides against the inner surface 50 of the second header 48.

[0063]

The case where the refrigerant that flows into the second header 48 is liquid refrigerant is described above as an example. However, in the case, for example, where the amount of refrigerant with which the refrigerant circuit is filled is small, two-phase refrigerant having, for example, a quality of larger than 0 and smaller than or equal to 0.2 may flow into the second header 48. Also in this case, the same effects are exerted.

[0064] A disproportionation reaction of the refrigerant is more likely to occur in the state where the distance between adjacent portions of a substance such as liquid refrigerant and two-phase refrigerant is very short. The case where the heat exchanger 12 or 15 serves as a condenser and liquid refrigerant or two-phase refrigerant flows into the second header 48 disposed closer to the outlet of the heat exchanger 12 or 15 has been described above. In the case where the heat-source-side heat exchanger 12 serves as an evaporator in the heating operation, two-phase refrigerant flows out from the heat-transmitting pipes 43 and the two-phase refrigerant flows into the first header 47. Also in such a case, a disproportionation reaction of the refrigerant is more likely to occur. Thus, by changing the structure of the first header 47 and each heat-transmitting pipe 43 to be similar to the above-described structure of the second header 48 and each heat-transmitting pipe 43, a disproportionation reaction can be rendered to be less likely to occur. Also in the case where the load-side heat exchanger 15 serves as an evaporator in the cooling operation, the two-phase refrigerant may flow out from the load-side heat exchanger 15 to the first header 47. Also in this case, preferably, the structure of the load-side heat exchanger 15 is changed to be similar to the structure of the heat-source-side heat exchanger 12.

[0065]

Apparatuses such as a building-use multi-air-conditioning apparatus usually control, for example, the driving frequency of the compressor 10 or the rotation speed of a fan (not illustrated) attached to the heat-source-side heat exchanger 12 to control an evaporating temperature, which is the temperature of the refrigerant inside the evaporator, to be approximately 0 degrees C. Apparatuses also control, for example, the expansion device 16 so that the degree of superheat of the refrigerant at the outlet of the evaporator is approximately 0 to 5 degrees C. Thus, the refrigerant that flows into the first header 47 from the heat-transmitting pipes 43 has a temperature of approximately 0 degrees C and a pressure of a saturation pressure at approximately 0 degrees C. In this state, when the refrigerant has a solubility, in the refrigerating machine oil, of higher than or equal to 50 wt% (weight percent), a large amount of refrigerant is dissolved in the refrigerating machine oil, so that a disproportionation reaction can be minimized. Thus, in the state where the refrigerant that flows into the first header 47 is dissolved in the refrigerating machine oil at a solubility, in the refrigerating machine oil, of higher than or equal to 50 wt% (weight percent), a disproportionation reaction is less likely to occur even when the refrigerant is ejected from a remarkably close position, such as a position at which the value of (L/d) is under 10, and collides against the inner surface 50 of the first header 47.

[0066]

In this case, two-phase refrigerant having, for example, a quality of higher than or equal to 0.8 and lower than or equal to 0.99 flows into the first header 47.

[0067]

Fig. 7 illustrates that the center 45 or 46 of the outlet of each heat-transmitting pipe 43 is directed in a direction normal to the inner surface 50 of the header 47 or 48. However, the direction is not limited to this direction. The outlet of each heat-transmitting pipe 43 may be connected to be inclined to the inner surface 50 of the header 47 or 48. This configuration also has the same effects.

[0068]

The shape of the outlet of each heat-transmitting pipe 43 is not limited to a particular shape and may be any shape. In the description above, the outlet is illustrated to be a circular pipe. However, the outlet of each heat-transmitting pipe 43 may be in a long-hole shape obtained by cutting the heat-transmitting pipe 43 obliquely to the pipe axis or may be in other shape. This configuration also has the same effects. The equivalent diameter of each heat-transmitting pipe 43 corresponds to the inner diameter d.

[0069]

As described above, holes are bored in the side surface of the header 47 or 48 and the heat-transmitting pipes 43 are inserted into the holes. The header 47 or 48 and the heat-transmitting pipes 43 are then fastened to each other by, for example, soldering. In this case, the center 45 or 46 of the outlet of each heat-transmitting pipe 43 is usually arranged to protrude inward beyond the position at which the outlet comes into contact with the inner surface of the header 47 or 48. The distance by which the center 45 or 46 protrudes is usually smaller than or equal to 1/3 of the inner diameter of the header 47 or 48. In other words, the distance L is usually smaller than the inner diameter of the header 47 or 48 and larger than 2/3 of the inner diameter of the header 47 or 48.

[0070]

The heat exchanger 12 or 15 of Fig. 6 has four separate paths and the four heat-transmitting pipes 43 are connected to the header 47 or 48. However, the number of heat-transmitting pipes 43 is not limited to four.

[0071]

Fig. 8 is a schematic diagram of another configuration of a heat exchanger of the refrigeration cycle apparatus according to Embodiment 1 of the present invention. The heat exchanger 12 or 15 illustrated in Fig. 8 includes multiple headers on each of the refrigerant inflow side and the refrigerant outflow side. Specifically, the heat exchanger 12 or 15 includes two first headers 47a and 47b at one end. A first connecting pipe 41 is a branch pipe branched into sections, the number of which is the same (two, in this case) as the number of headers. One of the sections of the branched pipe is connected to the first header 47a and the other section of the pipe is connected to the first header 47b. Each of the first header 47a and the first header 47b is connected to two heat-transmitting pipes 43.

[0072]

The heat exchanger 12 or 15 also includes two second headers 48a and 48b at the other end. A second connecting pipe 42 is branched into two sections, the number of which is the same as the number of headers. One of the sections of the pipe is connected to the second header 48a and the other section of the pipe is connected to the second header 48b. Each of the second header 48a and the second header 48b is connected to two heat-transmitting pipes 43.

[0073]

As illustrated in the configuration illustrated in Fig. 8, the heat exchanger structure in which the connecting pipe 41 or 42 is a branch pipe and connected to multiple (two, in this case) headers 47 or 48 also has similar effects.

[0074]

Fig. 9 is a schematic diagram of another configuration of a heat exchanger of the refrigeration cycle apparatus according to Embodiment 1 of the present invention. The heat exchanger 12 or 15 illustrated in Fig. 9 is a heat exchanger having a 1-2 path, in which the number of paths (the number of flow paths) is changed in the middle of the flow path. In Fig. 9, the first connecting pipe 41 is connected to the first header 47. The first header 47 is branched into six paths and each pair of two paths merges on the way, so that the number of paths is halved. The second connecting pipe 42 is connected to the second header 48 and the second header 48 is connected to three heat-transmitting pipes 43. Thus, the number of heat-transmitting pipes 43 connected to the first connecting pipe 41 via the first header 47 is six and the number of heat-transmitting pipes 43 connected to the second connecting pipe 42 via the second header 48 is three.

[0075]

As in the above-described configuration, the heat exchanger structure in which the number of heat-transmitting pipes 43 connected to the first header 47 and the number of heat-transmitting pipes 43 connected to the second header 48 differ from each other also has the same effects.

The configuration of the 1 -2 path, the number of pipes, or other factors is not limited to this example.

[0076]

Fig. 10 is a schematic diagram of another heat-transmitting pipe used in a heat exchanger of the refrigeration cycle apparatus according to Embodiment 1 of the present invention. The case where each heat-transmitting pipe 43 is a circular pipe has been described above as an assumption. However, the shape of each heat-transmitting pipe 43 is not limited to a circular pipe. For example, Fig. 10 illustrates a flat pipe having a flat flow-path structure in which the inside is divided into multiple (four, in this case) flow paths (microchannels) 49. In the case, for example, where such a flat pipe is to be used as each heat-transmitting pipe 43, the total cross-sectional area obtained by adding together the cross-sectional areas of the flow paths 49 inside one heat-transmitting pipe 43 is regarded as the inner cross-sectional area of one heat-transmitting pipe 43 to find the above-described configuration that is less likely to cause a disproportionation reaction. Specific examples are described below.

[0077]

As illustrated in Fig. 10, a case where the heat exchanger 12 or 15 illustrated in Fig. 6 includes the heat-transmitting pipes 43 each having the inside divided into four flow paths 49 is described below. In the heat exchanger 12 or 15 illustrated in Fig. 6, four heat-transmitting pipes 43 are connected to the first connecting pipe 41 via the first header 47 and four heat-transmitting pipes 43 are connected to the second connecting pipe 42 via the second header 48. Thus, in the case where all the flow paths 49 in the heat-transmitting pipe 43 have the same inner cross-sectional area, the value obtained by multiplying the number (four, in this case) of flow paths 49 in one heat-transmitting pipe 43 by the inner cross-sectional area of each flow path 49 is regarded as the total inner cross-sectional area. Then, a value obtained by conversion into the equivalent diameter on the basis of the total area of inner cross-sectional areas is regarded as the inner diameter d. When the relationship between the distance L and the inner diameter d is adjusted to that described above, the heat exchanger 12 or 15 (refrigeration cycle apparatus) in which a disproportionation reaction is less likely to occur can be formed.

[0078]

The case where all the flow paths 49 in the heat-transmitting pipe 43 have the same inner cross-sectional area has been described above as an example.

However, the flow paths 49 are not limited to the example. Some of flow paths 49 may have a different inner cross-sectional area. For example, in Fig. 10, two of the four flow paths 49 at both ends may have an inner cross-sectional area different from the inner cross-sectional area of the other flow paths 49. The number of the flow paths 49 of the heat-transmitting pipe 43 is not limited to four.

[0079]

In the case where each heat-transmitting pipe 43 has a flat-pipe shape and the heat-transmitting pipe 43 is connected to the header 47 or 48, holes having a flat-pipe shape may be bored in the header 47 or 48 and the heat-transmitting pipes 43 may be directly connected to the header 47 or 48. Alternatively, circular holes may be bored in the header 47 or 48 and the heat-transmitting pipes 43 may be connected to the header 47 or 48 via joints each changing the shape from the flat-pipe shape to the circular-pipe shape.

[0080] [Extension Pipe 4]

As described above, the refrigeration cycle apparatus 100 according to Embodiment 1 has several operation modes. In these operation modes, the refrigerant flows through the extension pipes 4 that connect the outdoor unit 1 and the indoor units 2 together.

[0081]

In this example, the high-pressure detecting device 37 and the low-pressure detecting device 38 are disposed to control the refrigeration cycle high pressure and low pressure to be at the target values. Alternatively, the high-pressure detecting device 37 and the low-pressure detecting device 38 may be temperature detecting devices that detect saturation temperatures.

[0082]

The first refrigerant-flow switching device 11 has been described as being a four-way valve, but the first refrigerant-flow switching device 11 is not limited to a fourway valve. Multiple two-way passage switching valves or three-way passage switching valves may be used, instead, to cause the refrigerant to flow in the same manner.

[0083] A fan is usually attached to each of the heat-source-side heat exchanger 12 and the load-side heat exchangers 15a to 15d to accelerate condensation or evaporation using an air blast, but the configuration is not limited to this example.

For example, a device such as a panel heater using radiation is usable as each of the load-side heat exchangers 15a to 15d. A water-cooled device that transfers heat using water or an antifreeze fluid is usable as the heat-source-side heat exchanger 12. Any heat exchanger having a structure capable of radiating or receiving heat is usable.

[0084]

The heat-source-side heat exchanger 12 or the load-side heat exchangers 15a to 15d usually include fins 44 for improving the heat transfer performance. When, however, the heat transfer performance is sufficient with the presence of the heat-transmitting pipes 43 alone, the fins 44 may be excluded.

[0085]

The case where four load-side heat exchangers 15a to 15d are included has been described above as an example, but any number of load-side heat exchangers may be connected. In addition, multiple outdoor units 1 may be connected to constitute one refrigeration cycle.

[0086]

In Embodiment 1, the refrigeration cycle apparatus 100 of a cooling-heating switchable type in which the indoor units 2 perform either the cooling operation or the heating operation has been described as an example, but the configuration is not limited to this example. For example, the invention is applicable to a refrigeration cycle apparatus in which each indoor unit 2 is capable of appropriately selecting either the cooling operation or the heating operation, so that the entire system can intermixedly operate an indoor unit 2 that performs the cooling operation and an indoor unit 2 that performs the heating operation together. This configuration also has the same effects.

[0087]

The present invention is also applicable to, for example, an air-conditioning apparatus in which only one indoor unit 2 is connectable, such as a room air-conditioning apparatus, or a refrigerator to which a showcase and a unit cooler are connected. Any refrigeration cycle apparatus that includes a refrigerant circuit and supplies heat using the refrigeration cycle has the same effects.

[0088]

The case where the first header 47 and the second header 48 are connected to both ends of the heat-source-side heat exchanger 12 or each of the load-side heat exchangers 15a to 15d has been described as an example, but the configuration is not limited to this example. For example, a distributor and a capillary pipe for the refrigerant may be connected to one end of the heat-source-side heat exchanger 12 or each of the load-side heat exchangers 15a to 15d and the header may be connected to the other end of the heat-source-side heat exchanger 12 or each of the load-side heat exchangers 15a to 15d. The refrigerant that flows into the heat- source-side heat exchanger 12 or the load-side heat exchangers 15a to 15d may be distributed using any other different configuration.

[0089]

Embodiment 2

Embodiment 2 of the present invention is described with reference to the drawings. Points in Embodiment 2 that differ from Embodiment 1 are mainly described below. Modification examples applied to components in Embodiment 1 are similarly applied to similar components in Embodiment 2.

[0090]

Fig. 11 is a circuit configuration diagram of a refrigeration cycle apparatus according to Embodiment 2 of the present invention. A refrigeration cycle apparatus 100 illustrated in Fig. 11 includes a refrigerant circuit A that connects the outdoor unit 1 and a heat medium relay unit 3, which is a relay device, together using extension pipes 4 to circulate refrigerant. The refrigeration cycle apparatus 100 also includes a heat-medium circuit B that connects the heat medium relay unit 3 and the indoor units 2 together using pipes (heat medium pipes) 5 to circulate a heat medium such as water and brine. The heat medium relay unit 3 includes a load-side heat exchanger 15a and a load-side heat exchanger 15b that cause the refrigerant circulating in the refrigerant circuit A and the heat medium circulating in the heat-medium circuit B to exchange heat between each other.

[0091]

The heat medium relay unit 3 is separate from the outdoor unit 1 and the indoor units 2 and disposed at a position away from the outdoor unit 1 and the indoor units 2, for example, in a space inside the structure 9 but different from the indoor space 7 (simply referred to as a space 8, below), such as a space above a ceiling, as illustrated in Fig. 1. The heat medium relay unit 3 may be disposed in other places, such as a common space in which an elevator and other devices are disposed.

[0092] [Type of Refrigerant, Fleat Exchanger (12 or 15)]

This refrigeration cycle apparatus 100 is capable of using refrigerant of the same type as the refrigerant according to Embodiment 1 and has the same effects. The header 47 or 48 described in Embodiment 1 is used as the heat-source-side heat exchanger 12.

[0093]

Operation modes that the refrigeration cycle apparatus 100 performs include a cooling only operation mode, in which all the indoor units 2 in active perform the cooling operation, and a heating only operation mode, in which all the indoor units 2 in active perform the heating operation. The operation modes also include a cooling main operation mode, performed when a cooling load is larger, and a heating main operation mode, performed when a heating load is larger.

[0094] [Cooling Only Operation Mode]

In the cooling only operation mode, high-temperature high-pressure gaseous refrigerant discharged from the compressor 10 flows into the heat-source-side heat exchanger 12 via the first refrigerant-flow switching device 11, transfers heat to ambient air, condenses and liquefies to be transformed into high-pressure liquid refrigerant, and flows out from the outdoor unit 1 through a check valve 13a. The refrigerant then flows into the heat medium relay unit 3 through the extension pipe 4. The refrigerant flowing into the heat medium relay unit 3 passes through an openingclosing device 17a and expands in the expansion device 16a and the expansion device 16b to be transformed into low-temperature low-pressure two-phase refrigerant. The two-phase refrigerant flows into the load-side heat exchanger 15a and the load-side heat exchanger 15b serving as evaporators, and receives heat from the heat medium circulating in the heat-medium circuit B to be transformed into low-temperature low-pressure gaseous refrigerant. The gaseous refrigerant flows out from the heat medium relay unit 3 via a second refrigerant-flow switching device 18a and a second refrigerant-flow switching device 18b. The refrigerant then flows into the outdoor unit 1 again through the extension pipe 4. The refrigerant flowing into the outdoor unit 1 passes through a check valve 13d and is sucked again into the compressor 10 via the first refrigerant-flow switching device 11 and the accumulator 19.

[0095]

In the heat-medium circuit B, the heat medium is cooled by both of the load-side heat exchanger 15a and the load-side heat exchanger 15b using the refrigerant. The cooled heat medium is caused to flow through the pipes 5 by pumps 21a and 21 b. The heat medium flowing into use-side heat exchangers 26a to 26d via second heat-medium-flow switching devices 23a to 23d receives heat from indoor air.

Indoor air is cooled so that the indoor space 7 is cooled. The refrigerant flowing out from the use-side heat exchangers 26a to 26d flows into heat medium flow control devices 25a to 25d, flows into the load-side heat exchanger 15a and the load-side heat exchanger 15b through first heat-medium-flow switching devices 22a to 22d to be cooled, and then is sucked again into the pumps 21a and 21b. When one or more of the use-side heat exchangers 26a to 26d have no heat load, one or more of the heat medium flow control devices 25a to 25d corresponding to the one or more of the use-side heat exchangers 26a to 26d having no heat load are tightly closed.

One or more of the heat medium flow control devices 25a to 25d corresponding to one or more of the use-side heat exchangers 26a to 26d having a heat load controls the opening degree to adjust the heat load of the one or more of the use-side heat exchangers 26a to 26d.

[0096] [Heating Only Operation Mode]

In the heating only operation mode, high-temperature high-pressure gaseous refrigerant discharged from the compressor 10 passes through a first connection pipe 4a and a check valve 13b through the first refrigerant-flow switching device 11 and flows out from the outdoor unit 1. The refrigerant then flows into the heat medium relay unit 3 through the extension pipe 4. The refrigerant flowing into the heat medium relay unit 3 passes through the second refrigerant-flow switching device 18a and the second refrigerant-flow switching device 18b, flows into the load-side heat exchanger 15a and the load-side heat exchanger 15b, and transfers heat to the heat medium circulating in the heat-medium circuit B to be transformed into high-pressure liquid refrigerant. The high-pressure liquid refrigerant expands in the expansion device 16a and the expansion device 16b to be transformed into low-temperature low-pressure two-phase refrigerant, passes through an opening-closing device 17b, and flows out from the heat medium relay unit 3. The refrigerant then flows into the outdoor unit 1 again through the extension pipe 4. The refrigerant flowing into the outdoor unit 1 passes through a second connection pipe 4b and a check valve 13c, flows into the heat-source-side heat exchanger 12 serving as an evaporator, and receives heat from ambient air to be transformed into low-temperature low-pressure gaseous refrigerant. The gaseous refrigerant is sucked again into the compressor 10 via the first refrigerant-flow switching device 11 and the accumulator 19. The heat medium in the heat-medium circuit B behaves in the same manner as in the case of the cooling only operation mode. In the heating only operation mode, the heat medium is heated by the refrigerant in the load-side heat exchanger 15a and the load-side heat exchanger 15b and transfers heat to the indoor air in the use-side heat exchanger 26a and the use-side heat exchanger 26b to heat the indoor space 7.

[0097] [Cooling Main Operation Mode]

In the cooling main operation mode, the high-temperature high-pressure gaseous refrigerant discharged from the compressor 10 flows into the heat-source-side heat exchanger 12 via the first refrigerant-flow switching device 11, transfers heat to ambient air, condenses to be transformed into two-phase refrigerant, passes through the check valve 13a, and flows out from the outdoor unit 1. The refrigerant then flows into the heat medium relay unit 3 through the extension pipe 4. The refrigerant flowing into the heat medium relay unit 3 flows into the load-side heat exchanger 15b serving as a condenser through the second refrigerant-flow switching device 18b and transfers heat to the heat medium circulating in the heat-medium circuit B to be transformed into high-pressure liquid refrigerant. The high-pressure liquid refrigerant expands in the expansion device 16b to be transformed into low-temperature low-pressure two-phase refrigerant. The two-phase refrigerant flows into the load-side heat exchanger 15a serving as an evaporator via the expansion device 16a, receives heat from the heat medium circulating in the heat-medium circuit B to be transformed into low-pressure gaseous refrigerant, and flows out from the heat medium relay unit 3 via the second refrigerant-flow switching device 18a. The refrigerant then flows into the outdoor unit 1 again through the extension pipe 4. The refrigerant flowing into the outdoor unit 1 passes through the check valve 13d and is sucked again into the compressor 10 via the first refrigerant-flow switching device 11 and the accumulator 19.

[0098]

In the heat-medium circuit B, the heating energy of the refrigerant is transferred to the heat medium in the load-side heat exchanger 15b. The heated heat medium is then caused to flow through the pipes 5 by the pump 21 b. The heat medium flowing into at least one of the use-side heat exchangers 26a to 26d requiring heating, with the corresponding one of the first heat-medium-flow switching devices 22a to 22d and the corresponding one of the second heat-medium-flow switching devices 23a to 23d operated, transfers heat to the indoor air. Indoor air is heated so that the indoor space 7 is heated. On the other hand, the cooling energy of the refrigerant is transferred to the heat medium in the load-side heat exchanger 15a. The cooled heat medium is caused to flow through the pipes 5 by the pump 21a. The heat medium flowing into at least one of the use-side heat exchangers 26a to 26d requiring cooling, with the corresponding one of the first heat-medium-flow switching devices 22a to 22d and the corresponding one of the second heat-medium-flow switching devices 23a to 23d operated, receives heat from the indoor air. The indoor air is cooled so that the indoor space 7 is cooled. When one or more of the use-side heat exchangers 26a to 26d have no heat load, one or more of the heat medium flow control devices 25a to 25d corresponding to the one or more of the use-side heat exchangers 26a to 26d having no heat load are tightly closed. One or more of the heat medium flow control devices 25a to 25d corresponding to one or more of the use-side heat exchangers 26a to 26d having a heat load controls the opening degree to adjust the heat load of the one or more of the use-side heat exchangers 26a to 26d.

[0099] [Heating Main Operation Mode]

In the heating main operation mode, high-temperature high-pressure gaseous refrigerant discharged from the compressor 10 passes through the first connection pipe 4a and the check valve 13b via the first refrigerant-flow switching device 11 and flows out of the outdoor unit 1. The refrigerant then flows into the heat medium relay unit 3 through the extension pipe 4. The refrigerant flowing into the heat medium relay unit 3 flows into the load-side heat exchanger 15b serving as a condenser through the second refrigerant-flow switching device 18b and transfers heat to the heat medium circulating in the heat-medium circuit B to be transformed into high-pressure liquid refrigerant. The high-pressure liquid refrigerant expands in the expansion device 16b to be transformed into low-temperature low-pressure two-phase refrigerant. The two-phase refrigerant flows into the load-side heat exchanger 15a serving as an evaporator via the expansion device 16a, receives heat from the heat medium circulating in the heat-medium circuit B, and flows out from the heat medium relay unit 3 via the second refrigerant-flow switching device 18a. The refrigerant then flows again into the outdoor unit 1 through the extension pipe 4. The refrigerant flowing into the outdoor unit 1 flows into the heat-source-side heat exchanger 12 serving as an evaporator through the second connection pipe 4b and the check valve 13c and receives heat from ambient air to be transformed into low-temperature low-pressure gaseous refrigerant. The gaseous refrigerant is sucked into the compressor 10 again via the first refrigerant-flow switching device 11 and the accumulator 19. The behavior of the heat medium in the heat-medium circuit B and the operations of the first heat-medium-flow switching devices 22a to 22d, the second heat-medium-flow switching devices 23a to 23d, the heat medium flow control devices 25a to 25d, and the use-side heat exchangers 26a to 26d are the same as those in the case of the cooling main operation mode.

[0100] [Extension Pipes 4 and Pipes 5]

In each operation mode of Embodiment 2, the refrigerant flows through the extension pipes 4 that connect the outdoor unit 1 and the heat medium relay unit 3 to each other, whereas the heat medium such as water and antifreeze fluid flows through the pipes 5 that connect the heat medium relay unit 3 and the indoor units 2 to each other.

[0101]

In the case where both heating load and cooling load are mixedly generated in use-side heat exchangers 26, a first heat-medium-flow switching device 22 and a second heat-medium-flow switching device 23 corresponding to at least one use-side heat exchanger 26 performing the heating operation are switched to the flow paths connected to the load-side heat exchanger 15b for heating. In addition, the first heat-medium-flow switching device 22 and the second heat-medium-flow switching device 23 corresponding to at least one use-side heat exchanger 26 performing the cooling operation are switched to the flow paths connected to the load-side heat exchanger 15a for cooling. Thus, each indoor unit 2 can freely perform the heating operation and the cooling operation.

[0102]

Each first heat-medium-flow switching device 22 and each second heat-medium-flow switching device 23 may be any device that can switch the flow paths from one to another, including a device that switches a three-way passage, such as a three-way valve, and a device obtained by combining two devices that open and close a two-way passage, such as an on-off valve. Alternatively, a device obtained by, for example, combining two devices capable of changing the flow rate of the three-way passage, such as a stepping-motor-driven mixing valves, or combining two devices capable of changing the flow rate of the two-way passage, such as an electronic expansion valves, may be used as each of the first heat-medium-flow switching devices 22 and the second heat-medium-flow switching devices 23. In addition, each heat medium flow control device 25 may be, instead of the two-way valve, a control valve including a three-way passage and may be disposed together with a bypass pipe that bypasses the use-side heat exchanger 26. A stepping motor-driven valve capable of controlling the flow rate of a flow flowing through a flow path is preferred to be used as each heat medium flow control device 25.

Alternatively, the heat medium flow control device 25 may be either a two-way valve or a three-way valve having one end closed. A device that opens and closes a two-way passage, such as an on-off valve, may be used as each heat medium flow control device 25 to control the average flow rate by repeating on-off control.

[0103]

The first refrigerant-flow switching device 11 and a second refrigerant-flow switching device 18 have been illustrated as being four-way valves, but are not limited to four-way valves. Multiple two-way passage switching valves or three-way passage switching valves may be used to cause the refrigerant to flow in the same manner.

[0104]

The same holds true naturally also in the case where only one use-side heat exchanger 26 and only one heat medium flow control device 25 are connected. Moreover, no problem occurs naturally also in the case where multiple devices that operate similarly are disposed as the load-side heat exchangers 15 and the expansion devices 16. The case where each heat medium flow control device 25 is built in the heat medium relay unit 3 has been described above as an example, but the configuration is not limited to this example. Each heat medium flow control device 25 may be built in the indoor unit 2 or may be disposed separately from the heat medium relay unit 3 and the indoor unit 2.

[0105]

Alternatively, each heat medium flow control device 25 may be omitted when at least one of each first heat-medium-flow switching device 22 and each second heat-medium-flow switching device 23 is configured to adjust the flow rate of the heat medium.

[0106]

Examples usable as a heat medium include brine (antifreeze fluid), water, a mixed solution of brine and water, and a mixed solution of water and an additive having a high anti-corrosive effect. Thus, the refrigeration cycle apparatus 100 is effective in improving the safety even if the heat medium leaks to the indoor space 7 via the indoor unit 2 because a highly safe heat medium is used.

[0107] A fan is usually attached to the heat-source-side heat exchanger 12 and the use-side heat exchangers 26a to 26d to accelerate condensation or evaporation using an air blast, but the configuration is not limited to this example. For example, a device such as a panel heater using radiation is usable as each of the use-side heat exchangers 26a to 26d. A water-cooled device that transfers heat using water or an antifreeze fluid is usable as the heat-source-side heat exchanger 12. Any heat exchanger having a structure capable of radiating or absorbing heat is usable.

[0108]

The case where four use-side heat exchangers 26a to 26d are disposed has been described above as an example, but any number of use-side heat exchangers may be connected. In addition, multiple outdoor units 1 may be connected to constitute one refrigeration cycle.

[0109]

The case where two load-side heat exchangers 15a and 15b are disposed has been described above as an example, but the configuration is not limited to this example, naturally. Any number of load-side heat exchangers may be disposed as long as the configuration enables cooling and or heating of the heat medium.

[0110] A plate-form heat exchanger is typically used as each load-side heat exchanger 15. Instead of a plate-form heat exchanger, any heat exchanger capable of causing the refrigerant and the heat medium to exchange heat may be used.

[0111]

The number of each of pumps 21a and 21b is not limited to one. Multiple pumps of a small capacity may be arranged in a row.

[0112]

In the refrigeration cycle apparatus according to Embodiment 2, the compressor 10, the four-way valve (first refrigerant-flow switching device) 11, and the heat-source-side heat exchanger 12 are accommodated in the outdoor unit 1, the use-side heat exchanger 26 that causes the air in the air-conditioned space and the refrigerant to exchange heat between each other is accommodated in each indoor unit 2, and the load-side heat exchangers 15 and the expansion devices 16 are accommodated in the heat medium relay unit 3. In addition, in the refrigeration cycle apparatus, the outdoor unit 1 and the heat medium relay unit 3 are connected to each other using the extension pipes 4 to circulate the refrigerant, each indoor unit 2 and the heat medium relay unit 3 are connected to each other using a pair of pipes 5 to circulate the heat medium, and the load-side heat exchangers 15 cause the refrigerant and the heat medium to exchange heat between each other. In Embodiment 2, a system capable of intermixedly operating at least one indoor unit 2 performing the cooling operation and at least one indoor unit 2 performing the heating operation together has been described as an example of the above-described apparatus. However, the configuration is not limited to this example. For example, the present invention is also applicable to a system in which the outdoor unit 1 and the heat medium relay unit 3 described in Embodiment 1 are combined together and the indoor units 2 only perform either the cooling operation or the heating operation. This configuration also has the same effects.

[0113]

Embodiment 3

As described in Embodiment 1 and Embodiment 2, a four-way valve is usually used as the first refrigerant-flow switching device 11, but the first refrigerant-flow switching device 11 is not limited to a four-way valve. For example, multiple two-way passage switching valves or multiple three-way passage switching valves may be used to form a configuration in which the refrigerant flows in the same manner as in the configuration including the four-way valve.

[0114]

In Embodiment 1 and Embodiment 2, the case where the accumulator 19 that accumulates excess refrigerant is disposed in the refrigerant circuit has been described, but the configuration is not limited to this example. In the case, for example, where the extension pipes 4 are short or the number of indoor unit 2 is one, an omission of the accumulator 19 causes no problem because the amount of excess refrigerant in the refrigerant circuit is small.

Reference Signs List [0115] 1 heat source device (outdoor unit) 2, 2a, 2b, 2c, 2d indoor unit 3 heat medium relay unit (relay device) 4 extension pipe (refrigerant pipe)4a first connection pipe 4b second connection pipe 5 pipe (heat medium pipe) 6 outdoor space 7 indoor space 8 space separate from outdoor space and indoor space such as space above ceiling 9 structure such as building 10 compressor 11 first refrigerant-flow switching device (four-way valve) 12 heat-source-side heat exchanger (first heat exchanger) 13a, 13b, 13c, 13d check valve 15, 15a, 15b, 15c, 15d load- side heat exchanger (second heat exchanger) 16, 16a, 16b, 16c, 16d expansion device 17a, 17b opening-closing device 18, 18a, 18bsecond refrigerant-flow switching device 19 accumulator 21 a, 21b pump 22, 22a, 22b, 22c, 22d first heat-medium-flow switching device 23, 23a, 23b, 23c, 23d second heat-medium-flow switching device 25, 25a, 25b, 25c, 25d heat medium flow control device 26, 26a, 26b, 26c, 26d use-side heat exchanger 27 load-side-heat-exchanger liquid-refrigerant-temperature detecting device 28 load-side-heat-exchanger gaseous-refrigerant-temperature detecting device 37 high-pressure detecting device 38 low-pressure detecting device 41 first connecting pipe 42 second connecting pipe 43 heat- transmitting pipe 44 fin 45 center (of outlet of heat-transmitting pipe 43 at one end) 46 center (of outlet of heat-transmitting pipe 43 at the other end) 47, 47a, 47bfirst header 48, 48a, 48bsecond header 49 flow path 50 inner surface 60 controller 100 refrigeration cycle apparatus A refrigerant circuit B heat-medium circuit

Claims

CLAIMS [Claim 1] A refrigeration cycle apparatus, comprising a refrigerant circuit connecting, by a refrigerant pipe, a compressor, a first heat exchanger, an expansion device, and a second heat exchanger, the refrigerant circuit being filled with single component refrigerant or mixed refrigerant and refrigerating machine oil miscible with the refrigerant, the single component refrigerant constituted of a substance having a property of causing a disproportionation reaction, the mixed refrigerant containing a substance having a property of causing a disproportionation reaction, at least one of the first heat exchanger and the second heat exchanger including heat-transmitting pipes through which the refrigerant flows, and a header into which an end portion of each of the heat-transmitting pipes on a refrigerant outlet side is inserted and through which the refrigerant flows, the header having an inner diameter larger than an inner diameter of each of the heat-transmitting pipes and the end portion of each of the heat-transmitting pipes on the refrigerant outlet side being disposed to face an in-pipe wall surface of the header, the end portion of each of the heat-transmitting pipes on the refrigerant outlet side being disposed at a position at which a value L/d is under 20 and over 0, where a distance from a center of the end portion of each of the heat-transmitting pipes on the refrigerant outlet side to a portion of the in-pipe wall surface of the header facing to the center is denoted with L and the inner diameter of the end portion of each of the heat-transmitting pipes on the refrigerant outlet side or an equivalent diameter corresponding to the inner diameter is denoted with d. [Claim 2] The refrigeration cycle apparatus of Claim 1, wherein the refrigerant circuit contains the refrigerating machine oil in which the refrigerant is soluble at a solubility of higher than or equal to 50 weight percent when the refrigerant has a temperature of 50 degrees C and a pressure of a saturation pressure at 50 degrees C, and an outlet of each of the heat-transmitting pipes is disposed at a position at which the value L/d is under 10 and over 0. [Claim 3] The refrigeration cycle apparatus of Claim 1 or 2, wherein the refrigerant circuit contains the refrigerating machine oil in which the refrigerant is soluble at a solubility of higher than or equal to 50 weight percent when the refrigerant has a temperature of 40 degrees C and a pressure of a saturation pressure at 50 degrees C, and an outlet of each of the heat-transmitting pipes is disposed at a position at which the value L/d is under 10 and over 0. [Claim 4] The refrigeration cycle apparatus of any one of Claims 1 to 3, wherein circulation of the refrigerant is so controlled that the refrigerant in a two-phase state and having a quality of over 0 and smaller than or equal to 0.2 flows to the header. [Claim 5] The refrigeration cycle apparatus of Claim 1, wherein the refrigerant circuit contains the refrigerating machine oil in which the refrigerant is soluble at a solubility of higher than or equal to 50 weight percent when the refrigerant has a temperature of 0 degrees C and a pressure of a saturation pressure at 0 degrees C, and an outlet of each of the heat-transmitting pipes is disposed at a position at which the value L/d is under 10 and over 0. [Claim 6] The refrigeration cycle apparatus of Claim 1 or 5, wherein circulation of the refrigerant is so controlled that the refrigerant in a two-phase state and having a quality higher than or equal to 0.8 and lower than or equal to 0.99 flows to the header. [Claim 7] The refrigeration cycle apparatus of any one of Claims 1 to 6, wherein the distance L is smaller than the inner diameter of the header and is larger than 2/3 of the inner diameter of the header. [Claim 8] The refrigeration cycle apparatus of any one of Claims 1 to 7, further comprising: an outdoor unit accommodating one of the first heat exchanger and the second heat exchanger; and an indoor unit accommodating an other one of the first heat exchanger and the second heat exchanger. [Claim 9] The refrigeration cycle apparatus of any one of Claims 1 to 8, further comprising: an outdoor unit accommodating one of the first heat exchanger and the second heat exchanger; an indoor unit configured to supply heat to a load; and a relay device accommodating an other one of the first heat exchanger and the second heat exchanger, the relay device being separate from the outdoor unit and the indoor unit and disposed at a position away from the outdoor unit and the indoor unit. [Claim 10] The refrigeration cycle apparatus of Claim 9, wherein the first heat exchanger or the second heat exchanger accommodated in the relay device is configured to cause the refrigerant and a heat medium different from the refrigerant to exchange heat between each other. [Claim 11] The refrigeration cycle apparatus of any one of Claims 8 to 10, wherein the first heat exchanger or the second heat exchanger accommodated in the outdoor unit is configured to cause the refrigerant and a heat medium to exchange heat between each other. [Claim 12] The refrigeration cycle apparatus of any one of Claims 8 to 11, further comprising one or more of the outdoor units and one or more of the indoor units, each of the one or more of the indoor units being configured to supply a load with air having exchanged heat with the refrigerant. [Claim 13] The refrigeration cycle apparatus of any one of Claims 1 to 12, further comprising a refrigerant-flow switching device configured to switch flow paths of the refrigerant, wherein the refrigeration cycle apparatus has a first operation mode, in which one of the first heat exchanger and the second heat exchanger is caused to serve as a condenser and an other one of the first heat exchanger and the second heat exchanger is caused to serve as an evaporator, and a second operation mode, in which one of the first heat exchanger and the second heat exchanger is caused to serve as an evaporator and an other one of the first heat exchanger and the second heat exchanger is caused to serve as a condenser. [Claim 14] The refrigeration cycle apparatus of any one of Claims 1 to 13, wherein the substance having a property of causing a disproportionation reaction is 1,1,2-trifluoroethylene.