EP3193089A1

EP3193089A1 - Refrigeration cycle apparatus

Info

Publication number: EP3193089A1
Application number: EP14901661.0A
Authority: EP
Inventors: Koji Yamashita
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2014-09-08
Filing date: 2014-09-08
Publication date: 2017-07-19
Also published as: WO2016038659A1; JPWO2016038659A1

Abstract

Provided is a refrigeration cycle apparatus, including a refrigeration cycle through which refrigerant circulates, the refrigeration cycle being formed by connecting a compressor (10), a first heat exchanger (12), an expansion device (16), and a second heat exchanger (15) by a refrigerant pipe, the refrigerant including single-component refrigerant made of a substance having such a property as to cause a disproportionation reaction or a refrigerant mixture, the refrigerant pipe including a bent portion (45), one of the first heat exchanger (12) and the second heat exchanger (15) being configured to serve as a condenser and an other thereof being configured to serve as an evaporator, the bent portion (45) being provided to one or both of a passage between the condenser and the expansion device and a passage between the expansion device and the evaporator, in which a bending radius R of the bent portion (45) through which liquid refrigerant or two-phase refrigerant flows satisfies the following relationship:

R \geq (d / 2) \times [1 + \{\tan (π / 36) + cosθ\}] / [1 - \{\tan (π / 36) + cosθ\}],

where θ (rad) represents an angle formed between a center line of an inlet pipe configured to form a refrigerant inlet side of the bent portion (45) and a center line of an outlet pipe configured to form a refrigerant outlet side of the bent portion (45), R (mm) represents a bending radius of the bent portion, and d (mm) represents an inner diameter of the inlet pipe of the bent portion (45).

Description

Technical Field

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

Background Art

In a refrigeration cycle apparatus configured to form a refrigerant circuit configured to circulate refrigerant therethrough so as to perform air-conditioning and other operations, like a multi-air-conditioning apparatus for a building, R410A that is incombustible or a combustible substance containing hydrogen and carbon, such as propane, is used as the refrigerant. When being released into atmosphere, the above-mentioned substances are decomposed in the atmosphere to turn into different substances with different time lengths. In the refrigeration cycle apparatus, however, the above-mentioned substances have high stability and therefore can be used as the refrigerant for a period of time as long as to several tens of years.
In contrast, some of the substances each containing hydrogen and carbon are poor in stability even in a refrigeration cycle apparatus and hence are each hardly used as refrigerant. Those substances poor in stability are, for example, substances each having such a property as to cause a disproportionation reaction. The term "disproportionation" refers to the property by which substances of the same kind react with each other to change into another substance.
For example, when certain strong energy is applied to refrigerant under a state in which a distance between adjacent substances is extremely small, such as a liquid state, the energy causes a disproportionation reaction and hence the adjacent substances react with each other to change into another substance. When the disproportionation reaction occurs, heat generation occurs to cause an abrupt increase in temperature and hence an abrupt increase in pressure may occur. For example, when the substance having such a property as to cause a disproportionation reaction is used as the refrigerant for the refrigeration cycle apparatus and is enclosed within a pipe made of copper or the like, the pipe cannot resist a rise in internal pressure of the refrigerant present inside thereof, which may lead to a rupture of the pipe or the like. For example, 1,1,2-trifluoroethylene (HFO-1123) or acetylene has been known as the substance having such a property as to cause a disproportionation reaction.
In addition, there exists a heat cycle system (refrigeration cycle apparatus) using 1,1,2-trifluoroethylene (HFO-1123) as a working medium for a heat cycle (for example, Patent Literature 1).

Citation List

Patent Literature

Patent Literature 1: WO 2012/157764 A1 (page 3, page 12, Fig. 1, etc.)

Summary of Invention

Technical Problem

In the refrigeration cycle apparatus such as the thermal cycle system disclosed in Patent Literature 1, 1,1,2-trifluoroethylene (HFO-1123) is disclosed to be used as a working medium for a thermal cycle. Here, 1,1,2-trifluoroethylene (HFO-1123) is a substance having such a property as to cause a disproportionation reaction. When the substance having such a property as to cause a disproportionation reaction is used directly as the refrigerant, the adjacent substances may react with each other to turn into a different substance due to some energy at a location where the substance in a liquid state is present, such as a liquid or a two-phase substance, in which a distance between the adjacent substances is extremely small, failing to serve as the refrigerant. In addition, there is a possibility that pipe rupture and the like may occur due to a sudden pressure rise.
Therefore, there is a problem in that, for the use as the refrigerant, the substance having such a property as to cause a disproportionation reaction needs to be used so as not to cause the disproportionation reaction. Therefore, efforts to prevent occurrence of the disproportionation reaction are required. However, in Patent Literature 1, for example, there is no disclosure of a method for realizing an apparatus capable of preventing the occurrence of the disproportionation reaction and the like.
The present invention has been made to overcome the problem described above, and has an object to provide a refrigeration cycle apparatus capable of reducing energy received by refrigerant from outside so that a substance having such a property as to cause a disproportionation reaction can be used safely as the refrigerant.

Solution to Problem

According to one embodiment of the present invention, there is provided a refrigeration cycle apparatus, including a refrigeration cycle through which refrigerant circulates, the refrigeration cycle being formed by connecting a compressor, a first heat exchanger, an expansion device, and a second heat exchanger by a refrigerant pipe, the refrigerant including single-component refrigerant made of a substance having such a property as to cause a disproportionation reaction or a refrigerant mixture inclusive of the substance having such a property as to cause a disproportionation reaction, the refrigerant pipe including a bent portion configured to change a direction of flow of the refrigerant in the refrigerant pipe, one of the first heat exchanger and the second heat exchanger being configured to serve as a condenser and an other thereof being configured to serve as an evaporator, the bent portion being provided to one or both of a passage between the condenser and the expansion device and a passage between the expansion device and the evaporator, in which a bending radius R of the bent portion through which liquid refrigerant or two-phase refrigerant flows satisfies the following relationship: $R \geq (d / 2) \times [1 + \{\tan (π / 36) + cosθ\}] / [1 - \{\tan (π / 36) + cosθ\}],$
where θ (rad) represents an angle formed between a center line of an inlet pipe configured to form a refrigerant inlet side of the bent portion and a center line of an outlet pipe configured to form a refrigerant outlet side of the bent portion, R (mm) represents a bending radius of the bent portion, and d (mm) represents an inner diameter of the inlet pipe of the bent portion.

Advantageous Effects of Invention

The refrigeration cycle apparatus according to one embodiment of the present invention can prevent the substance having such a property as to cause a disproportionation reaction, e.g., 1, 1, 2-trifluoroethylene (HFO-1123), from causing the disproportionation reaction to result in nonuse of the substance as the refrigerant, occurrence of a pipe rupture, or the like so that the substance can be used safely as the refrigerant.

Brief Description of Drawings

[Fig. 1] Fig. 1 is a schematic view for illustrating an example of installation of a refrigeration cycle apparatus according to Embodiment 1 of the present invention.
[Fig. 2] Fig. 2 is a circuit configuration diagram for illustrating an example of a circuit configuration of the refrigeration cycle apparatus according to Embodiment 1.
[Fig. 3] Fig. 3 is a refrigerant circuit diagram for illustrating flow of refrigerant when the refrigeration cycle apparatus according to Embodiment 1 of the present invention operates in a cooling operation mode.
[Fig. 4] Fig. 4 is a refrigerant circuit diagram for illustrating flow of the refrigerant when the refrigeration cycle apparatus according to Embodiment 1 of the present invention operates in a heating operation mode.
[Fig. 5] Fig. 5 is an enlarged sectional view of a bent portion in the refrigeration cycle apparatus according to Embodiment 1 of the present invention.
[Fig. 6] Fig. 6 is an explanatory view of a configuration for relaxing collision energy generated by the refrigerant in the refrigeration cycle apparatus according to Embodiment 1 of the present invention.
[Fig. 7] Fig. 7 is a view for illustrating the bent portion when an angle between an inlet pipe and an outlet pipe of the bent portion in the refrigeration cycle apparatus according to Embodiment 1 of the present invention is θ.
[Fig. 8] Fig. 8 is a solubility diagram of refrigerating machine oil in the refrigeration cycle apparatus according to Embodiment 1 of the present invention.
[Fig. 9] Fig. 9 is a circuit configuration diagram of a refrigeration cycle apparatus according to Embodiment 2 of the present invention.

Description of Embodiments

A refrigeration cycle apparatus according to embodiments of the present invention is described referring to the drawings. In the drawings referred to below including Fig. 1, components denoted by the same reference symbols correspond to the same or equivalent components. This is common throughout the embodiments described below. Further, the forms of the components described herein are merely examples, and the components are not limited to the forms described herein. In particular, the combinations of the components are not limited to only the combinations in each embodiment, and the components described in another embodiment may be applied to still another embodiment. Further, unless otherwise necessary to be distinguished or specified, a plurality of devices of the same type or other components, which are distinguished from one another by suffixes or in another way, may be described without the suffixes. Further, in the drawings, the size relationship between the components may be different from the actual size relationship. In addition, a high-and-low relationship or other relationships of temperature, pressure, or other factors are not determined in relation to particular absolute values, but are determined in a relative manner based on a state, an operation, or other factors of systems, devices, or other conditions.

Embodiment 1

Embodiment 1 of the present invention is described referring to the drawings. Fig. 1 is a schematic view for illustrating an example of installation of a refrigeration cycle apparatus according to Embodiment 1 of the present invention. The refrigeration cycle apparatus illustrated in Fig. 1 is configured to form a refrigerant circuit configured to circulate refrigerant therethrough to use a refrigeration cycle with the refrigerant, thereby being capable of selecting any one of a cooling mode and a heating mode as an operation mode. Here, an air-conditioning apparatus configured to air-condition an air-conditioning target space (indoor space 7) is described as an example of the refrigeration cycle apparatus according to this embodiment.
In Fig. 1, the refrigeration cycle apparatus according to this embodiment includes one outdoor unit 1 serving as a heat source apparatus, and a plurality of indoor units 2. The outdoor unit 1 and the indoor units 2 are connected to each other by extension pipes (refrigerant pipes) 4 through which the refrigerant is conveyed. Cooling energy or heating energy generated by the outdoor unit 1 is delivered to the indoor units 2.
The outdoor unit 1 is generally arranged in an outdoor space 6, which is a space outside of a construction 9 such as a building (for example, on a rooftop), and is configured to supply the cooling energy or heating energy to the indoor units 2. The indoor units 2 are arranged at positions at which temperature-conditioned air can be supplied to an indoor space 7 being a space inside the construction 9 (for example, residential room), and are configured to supply cooling air or heating air to the indoor space 7 being an air-conditioning target space.
As illustrated in Fig. 1, in the refrigeration cycle apparatus according to this embodiment, the outdoor unit 1 and each of the indoor units 2 are connected by the two extension pipes 4.
In Fig. 1, an example of a case where the indoor unit 2 is a ceiling cassette type indoor unit is illustrated, but the present invention is not limited thereto. Any types of the indoor unit such as a ceiling-concealed indoor unit or a ceiling-suspended indoor unit may be adopted as long as heating air or cooling air can be blown into the indoor space 7 directly or through a duct or other means.
In Fig. 1, an example of a case where the outdoor unit 1 is installed in the outdoor space 6 is illustrated, but the present invention is not limited thereto. For example, the outdoor unit 1 may be installed in an enclosed space such as a machine room with a ventilation port. Alternatively, the outdoor unit 1 may be installed inside the construction 9 as long as waste heat is exhaustible to the outside of the construction 9 through an exhaust duct. Further, when a water-cooled outdoor unit 1 is adopted, the outdoor unit 1 may be installed inside the construction 9. No particular problem may arise even if the outdoor unit 1 is installed at any place.
Further, the numbers of the outdoor units 1 and the indoor units 2 to be connected are not limited to the numbers as illustrated in Fig. 1, but may be determined depending on the construction 9 in which the refrigeration cycle apparatus according to this embodiment is installed.
Fig. 2 is a circuit configuration diagram for illustrating an example of a circuit configuration of the refrigeration cycle apparatus according to Embodiment 1 (hereinafter referred to as "refrigeration cycle apparatus 100"). Referring to Fig. 2, a 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 each other by the extension pipes (refrigerant pipes) 4 through which the refrigerant flows.

[Outdoor Unit 1]

In the outdoor unit 1, 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 are mounted in a serial connection by the refrigerant pipes.
The compressor 10 is configured to suck the refrigerant, and compress the refrigerant into a high-temperature and high-pressure state. For example, the compressor 10 may be a capacity-controllable inverter compressor or other components. The first refrigerant flow switching device 11 is configured to switch a flow of the refrigerant during a heating operation and a flow of the refrigerant during a cooling operation. The heat source-side heat exchanger 12 serves as an evaporator during the heating operation and serves as a condenser (or a radiator) during the cooling operation. Further, the heat source-side heat exchanger 12 serving as a first heat exchanger is configured to exchange heat between air supplied from a fan (not shown) and the refrigerant, thereby evaporating and gasifying the refrigerant or condensing and liquefying the refrigerant. The heat source-side heat exchanger 12 serves as a condenser during an operation of cooling the indoor space 7, and serves as an evaporator during an operation of heating the indoor space 7. The accumulator 19 is mounted on a suction side of the compressor 10 and configured to accumulate surplus refrigerant in the refrigerant circuit, which is generated due to a change in operation mode or the like.
The outdoor unit 1 includes the compressor 10, the first refrigerant flow switching device 11, the heat source-side heat exchanger 12, the accumulator 19, a high-pressure detection device 37, a low-pressure detection device 38, and a controller 60. Further, as the compressor 10, for example, a compressor having a low-pressure shell structure including a compression chamber defined inside a hermetic container placed under a low-refrigerant pressure atmosphere so as to suck and compress low-pressure refrigerant in the hermetic container or a compressor having a high-pressure shell structure including a hermetic container having inside placed under a high-refrigerant pressure atmosphere so as to discharge high-pressure refrigerant compressed in a compression chamber into the sealed container is used.
Further, the outdoor unit 1 includes the controller 60 configured to control the devices based on information detected by various detection devices, an instruction from a remote controller, and the like. For example, a driving frequency of the compressor 10, a rotation speed (including ON/OFF) of a fan, switching of the first refrigerant flow switching device 11 are controlled to execute each of the operation modes described later. Here, the controller 60 according to this embodiment is, for example, a microcomputer including a control arithmetic processing unit such as a central processing unit (CPU). Further, the controller 60 includes a storage unit (not shown) having data containing, as programs, a processing procedure relating to the control and other operations. Then, the control arithmetic processing unit executes the processing based on the data of the program to realize the control.

[Indoor Unit 2]

Each of the indoor units 2 includes a load-side heat exchanger 15 mounted therein, serving as a second heat exchanger. The load-side heat exchanger 15 is connected to the outdoor unit 1 by the extension pipes 4. The load-side heat exchanger 15 is configured to exchange heat between air supplied from a fan (not shown) and the refrigerant so that heating air or cooling air to be supplied to the indoor space 7 is generated. The load-side heat exchangers 15 serve as condensers during the operation of heating the indoor space 7. Further, the load-side heat exchangers 15 serve as evaporators during the operation of cooling the indoor space 7.
In Fig. 2, an example of a case where four indoor units 2 are connected is illustrated, and the four indoor units are illustrated as an indoor unit 2a, an indoor unit 2b, an indoor unit 2c, and an indoor unit 2d, respectively, in the stated order from the bottom of the drawing sheet. Further, corresponding to the indoor units 2a to 2d, the respective load-side heat exchangers 15 are 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 the stated order from the bottom of the drawing sheet as well. Similarly to Fig. 1, the number of the indoor units 2 to be connected is not limited to four as illustrated in Fig. 2.
Each of the operation modes to be executed by the refrigeration cycle apparatus 100 is described. The refrigeration cycle apparatus 100 is configured to determine the operation mode of the outdoor unit 1 as any one of a cooling operation mode and a heating operation mode based on an instruction from each indoor unit 2. That is, the refrigeration cycle apparatus 100 is capable of performing the same operation (cooling operation or heating operation) among all the indoor units 2 to adjust the indoor temperature. Operating and not operating of each indoor unit 2 may be switched freely in any of the cooling operation mode and the heating operation mode.
The operation modes to be executed by the refrigeration cycle apparatus 100 include the cooling operation mode in which all running indoor units 2 are executable of the cooling operation (irrespective of whether they are actually executing the cooling operation), and the heating operation mode in which all the running indoor units 2 are executable of the heating operation (irrespective of whether they are actually executing the cooling operation). Hereafter, each of the operation modes is described with the flows of the refrigerant.

[Cooling Operation Mode]

Fig. 3 is a refrigerant circuit diagram for illustrating the flow of the refrigerant during the cooling operation mode of the refrigeration cycle apparatus according to Embodiment 1 of the present invention. In Fig. 3, the cooling operation mode is described taking as an example a case where a cooling load is generated in all the load-side heat exchangers 15. In Fig. 3, the pipes indicated by the thick lines are the pipes through which the refrigerant flows. A direction of the flow of the refrigerant is indicated by the solid arrows.
In the case of the cooling operation mode illustrated in Fig. 3, the first refrigerant flow switching device 11 in the outdoor unit 1 is switched so that the refrigerant discharged from the compressor 10 flows into the heat source-side heat exchanger 12. Low-temperature and low-pressure refrigerant is compressed by the compressor 10 and discharged as high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows into the heat source-side heat exchanger 12 through the first refrigerant flow switching device 11. Then, after the refrigerant flowing into the heat source-side heat exchanger 12 is condensed and liquefied into high-pressure liquid refrigerant in the heat source-side heat exchanger 12 while rejecting heat to the outdoor air, the high-pressure liquid refrigerant flows out of the outdoor unit 1.
The high-pressure liquid refrigerant flowing out of the outdoor unit 1 passes through the extension pipe 4 to flow into each of the indoor units 2 (2a to 2d). The high-pressure liquid refrigerant flowing into the indoor unit 2 (2a to 2d) flows into an expansion device 16 (16a to 16d) to be expanded and depressurized into low-temperature and low-pressure two-phase refrigerant by the expansion device 16 (16a to 16d). Further, the low-temperature and low-pressure two-phase refrigerant flows into each of the load-side heat exchangers 15 (15a to 15d) functioning as an evaporator. The refrigerant flowing into the load-side heat exchanger 15 takes away heat from air flowing around the load-side heat exchanger 15 to turn into low-temperature and low-pressure gas refrigerant. Then, the low-temperature and low-pressure gas refrigerant flows out of the indoor unit 2 (2a to 2d), and passes through the extension pipe 4 to flow into the outdoor unit 1 again. Then, the refrigerant passes through the first refrigerant flow switching device 11, and is then sucked into the compressor 10 again through the accumulator 19.
At this time, an opening degree (opening area) of each of the expansion devices 16a to 16d is controlled so that a temperature difference (degree of superheat) between a temperature detected by a load-side heat exchanger gas refrigerant temperature detection device 28 and an evaporation temperature transmitted from the controller 60 of the outdoor unit 1 to a controller (not shown) of each of the indoor units 2 becomes close to a target value.
When the cooling operation mode is executed, the refrigerant is not required to be controlled to flow into the load-side heat exchanger 15 without a heat load (including a thermostat-off state), and hence the operation is stopped. At this time, the expansion device 16 corresponding to the idle indoor unit 2 is fully closed or set at a small opening degree for preventing the flow of refrigerant.

[Heating Operation Mode]

Fig. 4 is a refrigerant circuit diagram for illustrating a flow of refrigerant during the heating operation mode of the refrigeration cycle apparatus according to Embodiment 1 of the present invention. In Fig. 4, the heating operation mode is described taking as an example a case where a heating load is generated in all of the load-side heat exchangers 15. In Fig. 4, the pipes indicated by the thick lines are the pipes through which the refrigerant flows, and directions of the flows of refrigerant are indicated by the solid arrows.
In the case of the heating operation mode illustrated in Fig. 4, the first refrigerant flow switching device 11 in the outdoor unit 1 is switched so that the refrigerant discharged from the compressor 10 flows into the indoor unit 2 without passing through the heat source-side heat exchanger 12. Low-temperature and low-pressure refrigerant is compressed into high-temperature and high-pressure gas refrigerant by the compressor 10 to be discharged from the compressor 10. The high-temperature and high-pressure gas refrigerant passes through the first refrigerant flow switching device 11 to flow out of the outdoor unit 1. The high-temperature and high-pressure gas refrigerant flowing out of the outdoor unit 1 passes through the extension pipe 4 to flow into each of the indoor units 2 (2a to 2d).
The high-temperature and high-pressure gas refrigerant flowing into the indoor unit 2 (2a to 2d) flows into each of the load-side heat exchangers 15 (15a to 15d), and is condensed and liquefied into high-temperature and high-pressure liquid refrigerant while rejecting heat to air flowing around the load-side heat exchanger 15 (15a to 15d). The high-temperature and 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) to be expanded and depressurized into low-temperature and low-pressure two-phase refrigerant by the expansion device 16 (16a to 16d), and flows out of the indoor unit 2 (2a to 2d). The low-temperature and low-pressure two-phase refrigerant flowing out of the indoor unit 2 passes through the extension pipe 4 to flow into the outdoor unit 1 again.
At this time, the opening degree (opening area) of each of the expansion devices 16a to 16d is controlled so that a temperature difference (degree of subcooling) between a condensing temperature transmitted from the controller 60 of the outdoor unit 1 to a controller (not shown) of each of the indoor units 2 and a temperature detected by a load-side heat exchanger liquid refrigerant temperature detection device 27 approximates a target value.
The low-temperature and low-pressure two-phase refrigerant flowing into the outdoor unit 1 flows into the heat source-side heat exchanger 12 and takes away heat from air flowing around the heat source-side heat exchanger 12 to be evaporated into low-temperature and low-pressure gas refrigerant or low-temperature and low-pressure two-phase refrigerant with high quality. The low-temperature and low-pressure gas refrigerant or two-phase refrigerant is sucked into the compressor 10 again through the first refrigerant flow switching device 11 and the accumulator 19.
When the heating operation mode is executed, the refrigerant is not required to be controlled to flow into the load-side heat exchanger 15 without a heat load (including a thermostat-off state). When the expansion device 16 corresponding to the load-side heat exchanger 15 without a heating load is fully closed or is set to a small opening degree for preventing the flow of refrigerant in the heating operation mode, however, the refrigerant is cooled and condensed inside the idle load-side heat exchanger 15 by ambient air so that the refrigerant may stagnate, resulting in shortage of refrigerant in the entire refrigerant circuit. Therefore, during the heating operation, the opening degree (opening area) of the expansion device 16 corresponding to the load-side heat exchanger 15 without a heat load is set to a large opening degree, for example, is fully opened, thereby preventing the stagnation of refrigerant.
Further, a four-way valve is generally used for the first refrigerant flow switching device 11. However, the refrigerant flow switching device 11 is not limited thereto. A plurality of two-way passage switching valves or a plurality of three-way passage switching valves may be used so that the refrigerant flows in the same way.
Further, although the case where the accumulator 19 configured to accumulate the surplus refrigerant is included in the refrigerant circuit is described herein, the accumulator 19 is not required to be provided because the amount of surplus refrigerant is small in a case where the extension pipes 4 are short, the number of indoor units 2 is one, or other cases.
As described above, in the refrigeration cycle apparatus 100, while the indoor units 2 are performing the cooling operation, the heat source-side heat exchanger 12 serve as the condenser. The high-temperature and high-pressure gas refrigerant flows into the heat source-side heat exchanger 12 to be condensed, and is liquefied via a two-phase region to turn into the high-temperature and high-pressure liquid refrigerant to flow out thereof. Further, while the indoor units 2 are performing the heating operation, the load-side heat exchangers 15 (15a to 15d) serve as the condensers. The high-temperature and high-pressure gas refrigerant flows into the load-side heat exchangers 15 (15a to 15d) to be condensed, and is liquefied via the two-phase region to turn into the high-temperature and high-pressure liquid refrigerant to flow out thereof.

[Kinds of Refrigerant]

When a substance generally used as the refrigerant, such as R32 or R410A, is used as the refrigerant to be used in the refrigeration cycle apparatus 100, the substance may be used as it is without efforts to improve stability of the refrigerant inside the refrigerant circuit. However, herein, a single-component refrigerant consisting of a substance having such a property as to cause a disproportionation reaction, such as 1,1,2-trifluoroethylene (HFO-1123) represented by C2H1F3 and having one double bond in a molecular structure thereof, or a refrigerant mixture obtained by mixing the substance having such a property as to cause a disproportionation reaction and another substance is used as the refrigerant. The refrigerant used in this example is not limited to HFO-1123, and any refrigerant containing the substance having such a property as to cause a disproportionation reaction may be used.
For example, a tetrafluoropropene represented by C₃H₂F₄ (such as HFO-1234yf that is 2,3,3,3-tetrafluoropropene represented by CF₃CF=CH₂ or HFO-1234ze that is 1,3,3,3-tetrafluoro-1-propene represented by CF₃CH=CHF) or difluoromethane (HFC-32) represented by a chemical formula CH₂F₂ is used as the substance to be mixed with the substance having such a property as to cause a disproportionation reaction for producing the refrigerant mixture. However, the substance to be mixed with the substance having such a property as to cause a disproportionation reaction is not limited thereto and HC-290 (propane) or the like may be mixed. Any substance may be used as long as the substance has such thermal performance as to be capable of being used as the refrigerant of the refrigeration cycle apparatus 100, and further, any mixing ratio may be adopted at that time.
When the substance having such a property as to cause a disproportionation reaction is used directly as the refrigerant, the following problem occurs. Specifically, when some strong energy is applied at a location where the substance in
a liquid state is present, such as a liquid or a two-phase substance, in which a distance between the adjacent substances is extremely small, the adjacent substances react with each other to turn into a different substance, failing to serve as the refrigerant. In addition, there is a possibility of occurrence of a pipe rupture or the like due to a sudden pressure rise caused by heat generation. Therefore, for the use of the substance having such a property as to cause a disproportionation reaction as the refrigerant, efforts to prevent the occurrence of the disproportionation reaction are needed in a liquid portion or a two-phase portion in a mixed state of gas and liquid. Collision energy generated when the refrigerant and a structure collide against each other also becomes a factor of causing the disproportionation reaction of the refrigerant. Therefore, when a component of the refrigerant circuit is provided with a structure configured to enable reduction of the collision energy, the disproportionation reaction becomes unlikely to occur.

[Bent Portions 45]

During the cooling operation illustrated in Fig. 3, the heat source-side heat exchanger 12 serves as the condenser. The liquid refrigerant flows from an outlet of the heat source-side heat exchanger 12 to inlets of the expansion devices 16 (16a to 16d). In this portion, bent portions 45 (45a, 45b) configured to change a direction of flow of the refrigerant in the refrigerant pipes are present.
Fig. 5 is an enlarged sectional view of the bent portion in the refrigeration cycle apparatus according to Embodiment 1 of the present invention. When a pipe inner diameter is d and a bending radius at a center of the pipe is R in the bent portion 45, a bending radius of the bent portion 45 on an inner side of the pipe is R-d/2 and a bending radius on an outer side of the pipe is R+d/2. In Fig. 5, the bent portion 45 includes an inlet pipe 46 on a refrigerant inlet side, an outlet pipe 47 on a refrigerant outlet side, and a bent pipe 48 between the inlet pipe 46 and the outlet pipe 47.
Here, a point O and points A to F in Fig. 5 respectively indicate the following positions.

Point O: center of the bending radius R of the bent portion 45
Point A: intersection farther from the point O among two intersections between a straight line 46b drawn in a normal direction perpendicular to a center line 46a of the inlet pipe 46 to pass through the point O, and inner surfaces of the pipe
Point B: intersection farther from the point O among two intersections between a straight line 47b drawn in a normal direction perpendicular to a center line 47a of the outlet pipe 47 to pass through the point O, and the inner surfaces of the pipe
Point C: intersection closer to the point O among the two intersections between the straight line 46b drawn in the normal direction perpendicular to the center line 46a of the inlet pipe 46 to pass through the point O, and the inner surfaces of the pipe
Point D: intersection closer to the point O among the two intersections between the straight line 47b drawn in the normal direction perpendicular to the center line 47a of the outlet pipe 47 to pass through the point O, and the inner surfaces of the pipe
Point E: intersection between a straight line along a farther one of inner surfaces of the inlet pipe 46 from the point O and a straight line along a farther one of inner surfaces of the outlet pipe 47 from the point O
Point F: intersection between a straight line connecting the point O and the point E and a farther one of inner surfaces of the pipe from the point O

It is assumed that the points A, B, C, D, E, F, and O are all present on the same plane.
Here, collision energy generated when the refrigerant flows into the bent portion 45 to collide against a facing surface, i.e., a curved surface A-F-B is obtained by Expression (1).
[Math. 1] $\begin{array}{l} COLLISION ENERGY = MASS OF REFRIGERANT \times CHANGE IN SPEED OF REFRIGERANT \\ = (MASS FLOW RATE OF REFRIGERANT \times UNIT TIME) \times CHANGE IN SPEED OF REFRIGERANT \end{array}$
Relaxation of the collision energy is now described below. Although an actual pipe has a three-dimensional cylindrical shape, a description is given herein for a two-dimensional cross section illustrated in Fig. 5. Therefore, although an actual relaxation amount of the collision energy and a relaxation amount of the collision energy described below have slightly different values, the relaxation amounts have the same tendency. Thus, the relaxation amount can be treated two dimensionally without causing any serious problem.
In Fig. 5, the surface facing the refrigerant flowing from the inlet pipe 46 into the bent portion 45 is the curved surface having a curvature (R+d/2). Under effects thereof, the collision energy generated by the refrigerant is dispersed and relaxed. At this time, the larger the bending radius R of the bent portion 45 (bent pipe 48), the larger the curvature of the facing surface so that the relaxation amount of the collision energy generated by the refrigerant is large. Specifically, the larger the bending radius R of the bent portion 45, the smaller the collision energy is and hence the disproportionation reaction is less likely to occur. Then, when (R+d/2), which is a length of a line segment B-E, is larger than that of a portion against which the refrigerant flowing from the inlet pipe 46 collides, the refrigerant flowing into the inlet pipe 46 entirely collides against the curved surface A-F-B. Therefore, the collision energy generated by the refrigerant is relaxed.
Meanwhile, (R+d/2), which is the length of the line segment B-E, is smaller than that of the portion against which the refrigerant flowing into the inlet pipe 46 collides, a part of the refrigerant flowing into the inlet pipe 46 collides against the curved surface A-F-B and a remaining part of the refrigerant collides against the outlet pipe 47. The inner surface of the outlet pipe 47 is oriented in the normal direction of the inner surface of the inlet pipe 46. Therefore, the part of the refrigerant flowing into the inlet pipe 46, which collides against the outlet pipe 47, collides against the inner surface of the outlet pipe 47 orthogonally. Thus, the collision energy generated between the refrigerant and the inner surface of the pipe is not relaxed, and hence large collision energy is generated, resulting in a possibility of occurrence of the disproportionation reaction of the refrigerant. Thus, in order to relax the collision energy generated by the refrigerant so as to prevent the occurrence of the disproportionation reaction of the refrigerant, the refrigerant flowing into the inlet pipe 46 is required to entirely collide against the curved surface A-F-B.
When a fluid is ejected into a space, the fluid is diffused while spreading peripherally. An angle of spread at this time is regarded generally as about 5 degrees. A configuration for relaxing the collision energy generated by the refrigerant is examined below in view of the angle of spread.
Fig. 6 is an explanatory view of a configuration for relaxing the collision energy generated by the refrigerant in the refrigeration cycle apparatus according to Embodiment 1 of the present invention.
The refrigerant flowing into the inlet pipe 46 passes through a plane having a line segment A-C as a cross section, and is spread therefrom in accordance with the angle of spread of the jet to collide against the facing surface. The refrigerant does not come into contact with a solid wall surface only on the outlet pipe 47 side. A distance over which the refrigerant travels is a length of a line segment O-B, i.e., (R+d/2). Thus, in order to cause the refrigerant flowing into the inlet pipe 46 to entirely collide against the curved surface A-F-B so as to relax the collision energy generated by the refrigerant, Expression (2) is required to be satisfied.
[Math. 2] $R + d / 2 \geq d + (R + d / 2) \times \tan (5 \times π / 180)$
Expression (2) is rewritten into Expression (3). When this expression is satisfied, the collision energy generated by the refrigerant at the bent portion 45 is relaxed. As a result, the disproportionation of the refrigerant is unlikely to occur.
[Math. 3] $R \geq \frac{d}{2} \times \frac{1 + \tan (π / 36)}{1 - \tan (π / 36)}$
For example, when an outer diameter of the inlet pipe 46 of the bent portion 45 is 1/4 inch (6.35 mm), a thickness of the pipe is about 0.6 mm and an inner diameter is 5.15 mm. When the bending radius is 3.0688 mm or larger, the disproportionation reaction of the refrigerant is unlikely to occur. Therefore, when the outer diameter of the inlet pipe 46 of the bent portion 45 is small, the same effect is obtained with a smaller bending radius. Therefore, when the outer diameter of the inlet pipe 46 of the bent portion 45 is 1/4 inch or smaller, the disproportionation reaction is unlikely to occur by setting the bending radius to 3.0688 mm or larger.
Further, when, for example, the outer diameter of the inlet pipe 46 of the bent portion 45 is 3/8 inch (9.52 mm), the thickness of the pipe is about 0.7 mm and the inner diameter is 8.12 mm. When the bending radius is 4.8385 mm or larger, the disproportionation reaction of the refrigerant is unlikely to occur. Therefore, when the outer diameter of the inlet pipe 46 of the bent portion 45 is 1/4 inch or larger and 3/8 inch or smaller, the disproportionation reaction is unlikely to occur by setting the bending radius to 4.8385 mm or larger.
Still further, when, for example, the outer diameter of the inlet pipe 46 of the bent portion 45 is 1/2 inch (12.7 mm), the thickness of the pipe is about 0.8 mm and the inner diameter is 11.1 mm. When the bending radius is 6.6142 mm or larger, the disproportionation reaction of the refrigerant is unlikely to occur. Therefore, when the outer diameter of the inlet pipe 46 of the bent portion 45 is 3/8 inch or larger and 1/2 inch or smaller, the disproportionation reaction is unlikely to occur by setting the bending radius to 6.6142 mm or larger.
Still further, when, for example, the outer diameter of the inlet pipe 46 of the bent portion 45 is 5/8 inch (15.88 mm), the thickness of the pipe is about 0.9 mm and the inner diameter is 14.08 mm. When the bending radius is 8.3899 mm or larger, the disproportionation reaction of the refrigerant is unlikely to occur. Therefore, when the outer diameter of the inlet pipe 46 of the bent portion 45 is 1/2 inch or larger and 5/8 inch or smaller, the disproportionation reaction is unlikely to occur by setting the bending radius to 8.3899 mm or larger.
Still further, when, for example, the outer diameter of the inlet pipe 46 of the bent portion 45 is 3/4 inch (19.05 mm), the thickness of the pipe is about 1 mm and the inner diameter is 17.05 mm. When the bending radius is 10.1597 mm or larger, the disproportionation reaction of the refrigerant is unlikely to occur. Therefore, when the outer diameter of the inlet pipe 46 of the bent portion 45 is 5/8 inch or larger and 3/4 inch or smaller, the disproportionation reaction is unlikely to occur by setting the bending radius to 10.1597 mm or larger.
Still further, when, for example, the outer diameter of the inlet pipe 46 of the bent portion 45 is 7/8 inch (22.2 mm), the thickness of the pipe is from about 1 mm to 1.2 mm and the inner diameter is from 19.8 mm to 20.2 mm. When the bending radius is 12.0367 mm or larger, which is a value calculated for 20. 2 mm corresponding to a large dimension thereof, the disproportionation reaction of the refrigerant is unlikely to occur. Therefore, when the outer diameter of the inlet pipe 46 of the bent portion 45 is 3/4 inch or larger and 7/8 inch or smaller, the disproportionation reaction is unlikely to occur by setting the bending radius to 12.0367 mm or larger.
Still further, when, for example, the outer diameter of the inlet pipe 46 of the bent portion 45 is 1 inch (25.4 mm), the thickness of the pipe is from about 1 mm to 1.3 mm and the inner diameter is from 22.8 mm to 23.4 mm. When the bending radius is 13.9435 mm or larger, which is a value calculated for 23. 4 mm corresponding to a large dimension thereof, the disproportionation reaction of the refrigerant is unlikely to occur. Therefore, when the outer diameter of the inlet pipe 46 of the bent portion 45 is 7/8 inch or larger and 1 inch or smaller, the disproportionation reaction is unlikely to occur by setting the bending radius to 13.9435 mm or larger.
In Fig. 5, there is illustrated the case where the outlet pipe 47 of the bent portion 45 is oriented in the normal direction of the inlet pipe 46, specifically, the case where the angle between the inlet pipe 46 and the outlet pipe 47 is 90 degrees. The collision energy generated when the angle between the inlet pipe 46 and the outlet pipe 47 is θ is now examined below.
Fig. 7 is a view for illustrating the bent portion when the angle between the inlet pipe and the outlet pipe of the bent portion is θ in the refrigeration cycle apparatus according to Embodiment 1 of the present invention.
In this case, the refrigerant flowing into the inlet pipe 46 only needs to entirely collide against the curved surface A-F-B in consideration of an inclination of the inlet pipe 46. When Expression (4), specifically, Expression (5) obtained by developing Expression (4) is satisfied, an impact force is relaxed. As a result, the disproportionation of the refrigerant is unlikely to occur. Expression (2) and Expression (3) express a case where θ is 90 degrees in Expression (4) and Expression (5).
[Math. 4] $R + d / 2 \geq d + (R + d / 2) \times \{\tan (5 \times π / 180) + cosθ\}$

[Math. 5] $R \geq \frac{d}{2} \times \frac{1 + \{\tan (π / 36) + \cos\}}{1 - \{\tan (π / 36) + cosθ\}}$
Shapes of the inlet pipe 46, a portion containing the curved surface A-F-B, and the outlet pipe 47 of the bent portion 45 may be any shape. Although the shapes and the portion are illustrated as circular pipes in this case, a rectangular pipe, an elliptical pipe, and a pipe of other shapes may be used, thereby providing the same effects.
Further, during the heating operation illustrated in Fig. 4, the load-side heat exchangers 15 (15a to 15d) serve as the condensers. The liquid refrigerant flows from outlets of the load-side heat exchangers 15 (15a to 15d) to inlets of the expansion devices 16 (16a to 16d). When the bent portion 45 of the pipe is present in this portion, the same effects are obtained by providing the same structure as described above to the bent portion 45. Further, in Fig. 4, the heat source-side heat exchanger 12 serves as the evaporator. The two-phase refrigerant containing a mixture of the liquid refrigerant and the gas refrigerant flows from outlets of the expansion devices 16 (16a to 16d) to inlets of the evaporators. When the bend portion 45 of the pipe is present in the portion through which the two-phase refrigerant flows, the same effects are obtained by providing the same structure as described above to the bent portion 45. Further, when the bent portion 45 is present in an other portion through which the liquid refrigerant or the two-phase refrigerant flows in each of the operation modes, the same effects are obtained by providing the same structure.

[Refrigerating Machine Oil]

The refrigerating machine oil that fills the refrigerant circuit is based mainly on any one of polyol ester and polyvinyl ether. A part of the refrigerating machine oil filling the compressor 10 circulates in the refrigerant circuit together with the refrigerant. Polyol ester and polyvinyl ether are both refrigerating machine oil having miscibility with solubility to refrigerant having one double bond in a molecular structure. When the refrigerating machine oil and HFO1123 that is the refrigerant are mixed with each other, HFO-1123 is dissolved in the refrigerating machine oil to some extent. As described above, when the bent portion 45 is constructed as described above for the refrigerant having such a property as to cause the disproportionation reaction, the collision energy generated by the refrigerant is relaxed so that the disproportionation of the refrigerant is unlikely to occur. Further, when the refrigeration cycle is filled with the refrigerating machine oil having high miscibility, the disproportionation reaction of the refrigerant is further unlikely to occur as compared with a case where the refrigeration cycle is filled with refrigerating machine oil having low miscibility or refrigerating machine oil having immiscibility.
Fig. 8 is a solubility diagram of the refrigerating machine oil for the refrigeration cycle apparatus according to Embodiment 1 of the present invention. A large solubility means that a large amount of refrigerant is dissolved in the refrigerating machine oil, whereas a small solubility means that only a small amount of refrigerant is dissolved in the refrigerating machine oil. In Fig. 8, a relationship between the solubility and a pressure is shown for each of refrigerant temperatures T1, T2, and T3. In Fig 8, T1, T2, and T3 are different temperatures, and Expression (6) is satisfied.
[Math. 6] $T 1 < T 2 < T 3$
As shown in Fig. 8, under the same pressure condition, the solubility increases as the refrigerant temperature increases. Under the same temperature condition, the solubility increases as a refrigerant pressure increases. When the refrigerant is dissolved in the refrigerating machine oil, molecules of the refrigeration machine oil are dissolved and present between molecules of the refrigerant. Specifically, when the solubility of the refrigerant is large for the refrigerating machine oil, the refrigerating machine oil is present between a large number of molecules of the refrigerant. As described above, the disproportionation reaction of the refrigerant is a phenomenon in which the adjacent molecules of the refrigerant react with each other. Therefore, when the refrigerating machine oil having miscibility with the refrigerant is used, the disproportionation reaction of the refrigerant is unlikely to occur because of the presence of the molecules of the refrigerating machine oil between the molecules of the refrigerant. The refrigerating machine oil is not limited thereto and an other kind of oil may be used as long as the oil has miscibility with the refrigerant.
In order to suppress the disproportionation reaction of the refrigerant, a greater effect is obtained when the refrigerant has a larger solubility to the refrigerating machine oil. In practical use, when the solubility is 50 wt% (% by weight) or larger, a large amount of the refrigerant is dissolved in the refrigerating machine oil. Therefore, the disproportionation reaction can be suppressed.
In general, in a multi-air conditioning apparatus for a building or other apparatus, a condensing temperature being the temperature of the refrigerant inside the condenser is controlled to about 50 degrees Celsius by controlling a frequency of the compressor 10 or a rotation speed of an air-sending device (not shown) auxiliary to the heat source-side heat exchanger 12. Further, a degree of subcooling of the refrigerant at an outlet of the condenser is controlled to about 10 degrees Celsius by controlling the expansion device 16. Specifically, when the condensing temperature is about 50 degrees Celsius, the refrigerant at the outlet of each of the condensers is controlled at about 40 degrees Celsius and then flows out of the condenser. Thus, the refrigerant present between each of the condenser and the expansion device 16 is under a state in which the temperature is about 40 degrees Celsius and the pressure is a saturated pressure at 50 degrees Celsius.
In consideration of control performance (transient property) in each of the expansion devices 16, the refrigerant flowing between the condenser and the expansion device 16 is under a state in which the temperature is a temperature between about 40 degrees Celsius and 50 degrees Celsius and the pressure is a saturated pressure at 50 degrees Celsius. Thus, when a solubility of the refrigerant to the refrigerating machine oil is large under the state at these temperature and pressure, the disproportionation reaction of the refrigerant is unlikely to occur. In practical use, when the refrigerant has a solubility of 50 wt% (% by weight) or larger to the refrigerating machine oil under the state at these temperature and pressure, a large amount of the refrigerant is dissolved in the refrigerating machine oil. Thus, the disproportionation reaction can be made further unlikely to occur.

[Extension Pipes 4]

As described above, the refrigeration cycle apparatus 100 according to this embodiment has some operation modes. In those operation modes, the refrigerant flows through the extension pipes 4 configured to connect the outdoor unit 1 and the indoor units 2 to each other.
Although the high-pressure detection device 37 and the low-pressure detection device 38 are installed so as to control a high pressure and a low pressure in the refrigeration cycle to target values, a temperature detection device configured to detect the saturation temperature may be provided instead.
Further, the fans are generally mounted on the heat source-side heat exchanger 12 and the load-side heat exchangers 15a to 15d, and the condensation or evaporation is promoted by sending air in many cases, but the present invention is not limited thereto. For example, panel heaters utilizing radiation or other such devices may be used as the load-side heat exchangers 15a to 15d, and a water-cooled device for transferring heat with water or an antifreeze solution may also be used as the heat source-side heat exchanger 12. Any heat exchangers may be used as long as the heat exchangers have a structure capable of rejecting or taking away heat.
The heat source-side heat exchanger 12 or each of the load-side heat exchangers 15a to 15d generally includes the fins 44 so as to improve heat transfer performance. However, when sufficient heat transfer performance is obtained only with the heat transfer tubes 43, the fins 44 are not required to be provided.
Further, although the case where the number of load-side heat exchangers 15a to 15d is four is described as an example, any number of load-side heat exchangers may be connected. In addition, a plurality of the indoor units 1 may be connected to form a single refrigeration cycle.
Further, although the refrigeration cycle apparatus 100 of the type for switching the cooling and the heating in which the indoor units 2 perform any one of the cooling operation and the heating operation is described as an example, the refrigeration cycle apparatus is not limited thereto. For example, the present invention is also applicable to a refrigeration cycle apparatus including the indoor units 2, each capable of arbitrarily selecting any one of the cooling operation and the heating operation, so that a mixed operation with the indoor unit 2 performing the cooling operation and the indoor unit 2 performing the heating operation can be performed as the entire system, and the same effects are obtained thereby.
Further, the present invention is also applicable to an air-conditioning apparatus such as a room air-conditioning apparatus to which only one indoor unit 2 can be connected, a refrigeration apparatus to which a showcase or a unit cooler is connected, and other apparatus. The same effects can be obtained as long as the refrigeration cycle apparatus uses the refrigeration cycle.

Embodiment 2

Embodiment 2 of the present invention is described referring to the drawings. Embodiment 2 is described below mainly for portions different from Embodiment 1. A variation applied in a constituent part of Embodiment 1 may be used in the same manner in the same constituent part of Embodiment 2.
Fig. 9 is a circuit diagram of a refrigeration cycle apparatus according to Embodiment 2 of the present invention.
The refrigeration cycle apparatus 100 illustrated in Fig. 9 includes a refrigerant circulating circuit A formed by connecting the outdoor unit 1 and a heat medium relay unit 3 serving as a relay device (3) by the extended pipes 4 to circulate the refrigerant therethrough. Further, the refrigeration cycle apparatus 100 includes a heat medium circulating circuit B formed by connecting the heat medium relay unit 3 and the indoor units 2 by pipes (heat-medium pipes) 5 to circulate a heat medium such as water or brine therethrough. The heat-medium relay unit 3 includes the refrigerant circulating through the refrigerant circulating circuit A, and the load-side heat exchanger 15a and the load-side heat exchanger 15b, each performing heat exchange with the heat medium circulating through the heat-medium circulating circuit B.
The heat medium relay unit 3 is separate from the outdoor unit 1 and the indoor units 2 and is installed at a position away therefrom, e.g., roof space (hereinafter referred to simply as "space 8") that is a space inside the building 9 but different from the indoor space 7. Besides, the heat-medium relay unit 3 can also be installed in a shared space, for example, in which an elevator or the like is provided.

[Kinds of Refrigerant]

In the refrigeration cycle apparatus 100, the same refrigerant as that of Embodiment 1 can be used, and the same effects are obtained thereby.
Operation modes executed by the refrigeration cycle apparatus 100 include a cooling only operation mode in which all the driven indoor units 2 perform the cooling operation and a heating only operation mode in which all the driven indoor units 2 perform the heating operation. Further, the operation modes also include a cooling main operation mode executed when a cooling load is larger and a heating main operation mode executed when a heating load is larger.

[Cooling Only Operation Mode]

In the case of the cooling only operation mode, high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows into the heat source-side heat exchanger 12 through the first refrigerant flow switching device 11, is condensed and liquefied into high-pressure liquid refrigerant while rejecting heat to circumambient air, and passes through a check valve 13a to flow out of the outdoor unit 1. Then, the high-pressure liquid refrigerant passes through the expansion pipe 4 to flow into the heat medium relay unit 3. The refrigerant flowing into the heat medium relay unit 3 passes through an opening and closing device 17a and is expanded by the expansion devices 16a and 16b into low-temperature and low-pressure two-phase refrigerant. The two-phase refrigerant flows into each of the load-side heat exchanger 15a and the load-side heat exchanger 15b, acting as the evaporator, to take away heat from the heat medium circulating through a heat medium circulation circuit B to turn into low-temperature and low-pressure gas refrigerant. The gas refrigerant flows out of the heat medium relay unit 3 through a second refrigerant flow switching device 18a and a second refrigerant flow switching device 18b. Then, the gas refrigerant passes through the extension pipe 4 to flow into the outdoor unit 1 again. The refrigerant flowing into the outdoor unit 1 passes through a check valve 13d to be sucked into the compressor 10 again through the first refrigerant flow switching device 11 and the accumulator 19.
In the heat medium circulation circuit B, the heat medium is cooled with the refrigerant in both the load-side heat exchanger 15a and the load-side heat exchanger 15b. The cooled heat medium is caused to flow inside pipes 5 by pumps 21 a and 21 b. The heat medium flowing into use-side heat exchangers 26a to 26d through second heat medium flow switching devices 23a to 23d takes away heat from indoor air. The indoor air is cooled to cool the indoor space 7. The refrigerant flowing out of the use-side heat exchangers 26a to 26d flows into heat medium flow control devices 25a to 25d, passes through first heat medium flow switching devices 22a to 22d to flow into the load-side heat exchanger 15a and the load-side heat exchanger 15b so as to be cooled, and is sucked into the pumps 21 a and 21 b again. The heat medium flow control devices 25a to 25d corresponding to the use-side heat exchangers 26a to 26d without a heat load are fully closed. Further, the opening degree of the heat medium flow control devices 25a to 25d corresponding to the use-side heat exchangers 26a to 26d without a heat load is adjusted so as to control the heat load in the use-side heat exchangers 26a to 26d.

[Heating Only Operation Mode]

In the case of the heating only operation mode, the high-temperature and high-pressure gas refrigerant discharged from the compressor 10 passes through the first connecting pipe 4a and a check valve 13b through the first refrigerant flow switching device 11 to flow out of the indoor unit 1. Then, the refrigerant flowing out of the indoor unit 1 passes through the extension pipe 4 to flow into the heat medium relay unit 3. 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 to flow into each of the load-side heat exchanger 15a and the load-side heat exchanger 15b to turn into high-pressure liquid refrigerant while rejecting heat to the heat medium circulating through the heat medium circulation circuit B. The high-pressure liquid refrigerant is expanded by the expansion devices 16a and 16b into low-temperature and low-pressure two-phase refrigerant, which then passes through an opening and closing device 17b to flow out of the heat medium relay unit 3.
Then, the refrigerant flowing out of the heat medium relay unit 3 passes through the extension pipe 4 to flow into the outdoor unit 1 again. The refrigerant flowing into the outdoor unit 1 passes through a second connecting pipe 4b and a check valve 13c to flow into the heat source-side heat exchanger 12 acting as the evaporator to turn into low-temperature and low-pressure gas refrigerant while taking away heat from the circumambient air. The gas refrigerant is sucked into the compressor 10 again through the first refrigerant flow switching device 11 and the accumulator 19. An operation of the heat medium in the heat medium circulation circuit B is the same as that in the cooling only operation mode. In the heating only operation mode, the heat medium is heated with the refrigerant in the load-side heat exchanger 15a and the load-side heat exchanger 15b and rejects heat to the indoor air in the use-side heat exchanger 26a and the use-side heat exchanger 26b so as to heat the indoor space 7.

[Cooling Main Operation Mode]

In the case of the cooling main operation mode, the high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows into the heat source-side heat exchanger 12 through the first refrigerant flow switching device 11 and is condensed into the two-phase refrigerant while rejecting heat to the circumambient air, which then passes through the check valve 13a to flow out of the outdoor unit 1. Then, the refrigerant flowing out of the outdoor unit 1 passes through the extension pipe 4 to flow into the heat medium relay unit 3. The refrigerant flowing into the heat medium relay unit 3 passes through the second refrigerant switching device 18b to flow into the load-side heat exchanger 15b acting as the condenser to turn into high-pressure liquid refrigerant while rejecting heat to the heat medium circulating through the heat medium circulation circuit B.
The high-pressure liquid refrigerant is expanded by the expansion device 16b into low-temperature and low-pressure two-phase refrigerant. The two-phase refrigerant flows into the load-side heat exchanger 15a acting as the evaporator through the expansion device 16a to turn into low-pressure gas refrigerant while taking away heat from the heat medium circulating through the heat medium circulation circuit B, which then flows out of the heat medium relay unit 3 through the second refrigerant flow switching device 18a. Then, the refrigerant flowing out of the heat medium relay unit 3 passes through the extension pipe 4 to flow into the outdoor unit 1 again. The refrigerant flowing into the outdoor unit 1 passes through the check valve 13d to be sucked into the compressor 10 again through the first refrigerant flow switching device 11 and the accumulator 19.
In the heat medium circulation circuit B, heating energy of the refrigerant is transferred to the heat medium in the load-side heat exchanger 15b. Then, the heated heat medium is caused to flow inside the pipes 5 by the pump 21 b. The heat medium is caused to flow into the use-side heat exchangers 26a to 26d, for which a heating request is made, by operating the first heat medium flow switching devices 22a to 22d and the second heat medium flow switching devices 23a to 23d, and rejects heat to the indoor air. The indoor air is heated to heat the indoor space 7. Meanwhile, cooling energy of the refrigerant is transferred to the heat medium in the load-side heat exchanger 15a.
Then, the cooled heat medium is caused to flow through the pipes 5 by the pump 21 a. The heat medium is caused to flow into the use-side heat exchangers 26a to 26d, for which a cooling request is made, by operating the first heat medium flow switching devices 22a to 22d and the second heat medium flow switching devices 23a to 23d, and takes away heat from the indoor air. The indoor air is cooled to cool the indoor space 7. The heat medium flow control devices 25a to 25d corresponding to the use-side heat exchangers 26a to 26d without a heat load are fully closed. Further, the opening degree of the heat medium flow control devices 25a to 25d corresponding to the use-side heat exchangers 26a to 26d with a heat load is adjusted so as to control a heat load in the use-side heat exchangers 26a to 26d.

[Heating Main Operation Mode]

In the case of the heating main operation mode, the high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows through the first refrigerant flow switching device 11 and then passes through the first connecting pipe 4a and the check valve 13b to flow out of the outdoor unit 1. Then, the refrigerant flowing out of the outdoor unit 1 passes through the extension pipe 4 to flow into the heat medium relay unit 3. The refrigerant flowing into the heat medium relay unit 3 passes through the second refrigerant switching device 18b to flow into the load-side heat exchanger 15b acting as the condenser to turn into high-pressure liquid refrigerant while rejecting heat to the heat medium circulating through the heat medium circulation circuit B. The high-pressure liquid refrigerant is expanded by the expansion device 16b into low-temperature and low-pressure two-phase refrigerant. The two-phase refrigerant flows into the load-side heat exchanger 15a acting as the evaporator through the expansion device 16a to take away heat from the heat medium circulating through the heat medium circulation circuit B, and then flows out of the heat medium relay unit 3 through the second refrigerant flow switching device 18a.
Then, the two-phase refrigerant passes through the extension pipe 4 to flow into the outdoor unit 1 again. The refrigerant flowing into the outdoor unit 1 passes through the second connecting pipe 4b and the check valve 13c to flow into the heat-source side heat exchanger 12 acting as the evaporator to turn into low-temperature and low-pressure gas refrigerant while taking away heat from the circumambient air. The gas refrigerant is sucked into the compressor 10 again through the first refrigerant flow switching device 11 and the accumulator 19. An operation of the heat medium in the heat medium circulation circuit B and 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 switching devices 25a to 25d, and the use-side heat exchangers 26a to 26d are the same as those in the cooling main operation mode.

[Bent Portion 45]

In Fig. 9, in the cooling only operation mode or the cooling main operation mode in which the heat source-side heat exchanger 12 is caused to serve as the condenser, the bent portion 45a, the bent portion 45b, and a bent portion 45c are installed in a portion from the outlet of the condenser to the inlets of the expansion devices 16 in which the liquid refrigerant or the two-phase refrigerant flows. When the bent portions are constructed so as to satisfy Expression (3) or Expression (5) described in Embodiment 1, the collision energy generated by the refrigerant is relaxed. As a result, the disproportionation of the refrigerant is unlikely to occur. Further, in the heating only operation mode or the heating main operation mode in which the heat source-side heat exchanger 12 is caused to serve as the evaporator, the two-phase refrigerant containing the mixture of the liquid refrigerant and the gas refrigerant flows from the outlets of the expansion devices 16 (16a to 16d) to the inlet of the condenser. When the bent portion 45 of the pipe is present in the portion in which the two-phase refrigerant flows, the same effects are obtained by providing the same structure as that described above to the bent portion 45. Further, when the bent portion 45 is present in an other portion through which the liquid refrigerant or the two-phase refrigerant flows in each of the operation modes, the same effects are obtained by providing the same structure.

[Extension Pipe 4 and Pipe 5]

In each of the operation modes according to this embodiment, the refrigerant flows through the extension pipes 4 configured to connect the outdoor unit 1 and the heat medium relay unit 3, whereas the heat medium such as water or the antifreeze solution flows through the pipes 5 configured to connect the heat medium relay unit 3 and the indoor units 2.
When the heating load and the cooling load are generated in a mixed manner in the use-side heat exchangers 26, the first heat medium flow switching device 22 and the second heat medium switching device 23 corresponding to the use-side heat exchanger 26 performing the heating operation is switched to a flow connected to the load-side heat exchanger 15b used for heating. Further, the first heat medium flow switching device 22 and the second heat medium flow switching device 23 corresponding to the use-side heat exchanger 26 performing the cooing operation is switched to a flow connected to the load-side heat exchanger 15a used for cooling. Therefore, each of the indoor units 2 can freely perform the heating operation or the cooling operation.
The first heat medium flow switching devices 22 and the second heat medium flow switching devices 23 may be any heating medium flow switching devices such as a three-way valve capable of switching a three-way passage or a combination of two opening and closing valves capable of opening and closing a two-way passage as long as the flow can be switched. Further, a switching device such as a stepping-motor driven mixing valve capable of changing a flow rate of the three-way passage, a combination of two switching devices such as electronic expansion valves, each capable of changing a flow rate of the two-way passage, or the like may be used as the first heat medium flow switching devices 22 and the second head medium flow switching devices 23.
Further, the heat medium flow control devices 25 may be control valves other than the two-way valves, each having a three-way passage, so as to be installed together with a bypass pipe configured to bypass the use-side heat exchangers 26. Further, the heat medium flow control devices 25 are preferably of stepping motor driven type capable of controlling the flow rate through the passage, and may be any of two-way valves and three-way valves having one closed end. Further, as the heat medium flow control devices 25, those configured to open and close the two-way passage, such as opening and closing valves, may be used to repeat ON/OFF so as to control an average flow rate.
Further, although each of the first refrigerant flow switching device 11 and the second refrigerant flow switching devices 18 is described as the four-way valve, those devices are not limited thereto. A plurality of two-way switching valves or three-way switching valves may be used so that the refrigerant flows in the same manner.
Further, it is apparent that the same effects are obtained even when only one use-side heat exchanger 26 and only one heat medium flow control device 25 are connected. Further, it is apparent that no problem arises even when a plurality of the load-side heat exchangers 15 performing the same operation and a plurality of the expansion devices 16 performing the same operation are installed. Further, although the case where the heat medium flow control devices 25 are built in the heat medium relay unit 3 is described, the heat medium flow control devices 25 are not limited thereto. The heat medium flow control devices 25 may be built in the indoor units 2, and the heat medium relay unit 3 and the indoor units 2 may be formed independently of each other.
Further, when one or both of the heat medium flow switching devices 22 and the heat medium flow switching devices 23 is configured to have a function of regulating a flow rate of the heat medium, the heat medium flow control devices 25 are not required to be provided.
As the heating medium, for example, brine (antifreeze solution), water, a mixed liquid of brine and water, a mixed liquid of an additive having a high anticorrosion effect in regard of water, or the like can be used. Therefore, in the refrigeration cycle apparatus 100, even when the heat medium leaks into the indoor space 7 through the indoor units 2, the heat medium having high safety is used, which therefore contributes to improvement of safety.
Further, the fans are generally mounted on the heat source-side heat exchanger 12 and the use-side heat exchangers 26a to 26d, and the condensation or evaporation is promoted by sending air in many cases, but the present invention is not limited thereto. For example, panel heaters utilizing radiation or other such devices may be used as the use-side heat exchangers 26a to 26d. Further, a water-cooled device for transferring heat with water or an antifreeze solution may also be used as the heat source-side heat exchanger 12. Any heat exchangers may be used as long as the heat exchangers have a structure capable of rejecting or taking away heat.
Further, although the case where the number of use-side heat exchangers 26a to 26d is four is described as an example, any number of use-side heat exchangers may be connected. In addition, a plurality of the indoor units 1 may be connected to form a single refrigeration cycle.
Further, although the case where the number of the load- side heat exchangers 15a and 15b is two is described, it is apparent that the number of load-side heat exchangers is not limited thereto. Any number of load-side heat exchangers may be installed as long as the heat medium can be cooled or heated.
Further, although a plate-type heat exchanger is generally used as each of the load-side heat exchangers 15, any types of heat exchangers may be used as long as heat can be exchanged between the refrigerant and the heat medium even when the heat exchangers are not of plate type.
The number of each of the pumps 21 a and 21 b is not limited to one. A plurality of pumps having a small capacity may be arranged in parallel.
Further, for the system in which 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 exchangers 26 configured to exchange heat between the air in the air-conditioning target space and the refrigerant are respectively accommodated in the indoor units 2, the load-side heat exchangers 15 and the expansion devices 16 are accommodated in the heat medium relay unit 3, the outdoor unit 1 and the heat medium relay unit 3 are connected by the extension pipes 4 to circulate the refrigerant therethrough, each of the indoor units 2 and the heat medium relay unit 3 are connected by a set of the two pipes 5 to circulate the heat medium therethrough, and heat is exchanged between the refrigerant and the heat medium in the load-side heat exchangers 15, the system capable of performing the mixed operation by the indoor unit 2 performing the cooling operation and the indoor unit 2 performing the heating operation is described as an example. However, the system is not limited thereto. For example, the present invention is also applicable to a system in which the outdoor unit 1 described in Embodiment 1 and the heat medium relay unit 3 are combined so that the indoor units 2 perform only the cooling operation or the heating operation, and the same effects are obtained thereby.

Reference Signs List

1 heat source apparatus (outdoor unit) 2, 2a, 2b, 2c, 2d indoor unit 3 heat medium relay unit (relay device (3)) 4 extension pipe 4a first connection pipe 4b second connection pipe 5 pipe (heat-medium pipe) 6 outdoor space 7 indoor space 8 space other than outdoor space or indoor space, e.g., roof space 9 construction 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 and closing device18, 18a, 18b second refrigerant flow switching device 19 accumulator 21 a, 21 b pump
22, 22a, 22b, 22c, 22d first heat medium flow switching device23, 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 detection device 28 load-side heat exchanger gas refrigerant temperature detection device 37 high-pressure detection device 38 low-pressure detection device 43 heat- transfer tube 45a, 45b, 45c bent portion 46 inlet pipe
47 outlet pipe 49 passage 60 controller 100 refrigerant cycle apparatus A refrigerant circulation circuit B heat medium circulation circuit

Claims

A refrigeration cycle apparatus, comprising a refrigeration cycle through which refrigerant circulates, the refrigeration cycle being formed by connecting a compressor, a first heat exchanger, an expansion device, and a second heat exchanger by a refrigerant pipe,
the refrigerant comprising single-component refrigerant comprising a substance having such a property as to cause a disproportionation reaction or a refrigerant mixture inclusive of a substance having such a property as to cause a disproportionation reaction,
the refrigerant pipe comprising a bent portion configured to change a direction of flow of the refrigerant in the refrigerant pipe,
one of the first heat exchanger and the second heat exchanger being configured to serve as a condenser and an other thereof being configured to serve as an evaporator,
the bent portion being provided to one or both of a passage between the condenser and the expansion device and a passage between the expansion device and the evaporator,
wherein a bending radius R of the bent portion through which liquid refrigerant or two-phase refrigerant flows satisfies the following relationship: $R \geq (d / 2) \times [1 + \{\tan (π / 36) + cosθ\}] / [1 - \{\tan (π / 36) + cosθ\}],$
where θ (rad) represents an angle formed between a center line of an inlet pipe configured to form a refrigerant inlet side of the bent portion and a center line of an outlet pipe configured to form a refrigerant outlet side of the bent portion, R (mm) represents a bending radius of the bent portion, and d (mm) represents an inner diameter of the inlet pipe of the bent portion.
The refrigeration cycle apparatus of claim 1, wherein the angle θ is 90 degrees.
The refrigeration cycle apparatus of claim 1 or 2, wherein an outer diameter of the inlet pipe of the bent portion is 1/4 inch or smaller, and the bending radius of the bent portion is 3.0688 mm or larger.
The refrigeration cycle apparatus of claim 1 or 2, wherein an outer diameter of the inlet pipe of the bent portion is larger than 1/4 inch and equal to or smaller than 3/8 inch, and the bending radius of the bent portion is 4.8385 mm or larger.
The refrigeration cycle apparatus of claim 1 or 2, wherein an outer diameter of the inlet pipe of the bent portion is larger than 3/8 inch and equal to or smaller than 1/2 inch, and the bending radius of the bent portion is 6.6412 mm or larger.
The refrigeration cycle apparatus of claim 1 or 2, wherein an outer diameter of the inlet pipe of the bent portion is larger than 1/2 inch and equal to or smaller than 5/8 inch, and the bending radius of the bent portion is 8.3899 mm or larger.
The refrigeration cycle apparatus of claim 1 or 2, wherein an outer diameter of the inlet pipe of the bent portion is larger than 5/8 inch and equal to or smaller than 3/4 inch, and the bending radius of the bent portion is 10.1597 mm or larger.
The refrigeration cycle apparatus of claim 1 or 2, wherein an outer diameter of the inlet pipe of the bent portion is larger than 3/4 inch and equal to or smaller than 7/8 inch, and the bending radius of the bent portion is 12.0367 mm or larger.
The refrigeration cycle apparatus of claim 1 or 2, wherein an outer diameter of the inlet pipe of the bent portion is larger than 7/8 inch and equal to or smaller than 1 inch, and the bending radius of the bent portion is 13.9435 mm or larger.
The refrigeration cycle apparatus of any one of claims 1 to 9, wherein the refrigerant has a solubility of 50% by weight or larger to refrigerating machine oil to fill the refrigeration cycle under a state in which a temperature of the refrigerant is 50 degrees Celsius and a pressure of the refrigerant is a saturated pressure at 50 degrees Celsius.
The refrigeration cycle apparatus of any one of claims 1 to 9, wherein the refrigerant has a solubility of 50% by weight or larger to refrigerating machine oil to fill the refrigeration cycle under a state in which a temperature of the refrigerant is 40 degrees Celsius and a pressure of the refrigerant is a saturated pressure at 50 degrees Celsius.
The refrigeration cycle apparatus of any one of claims 1 to 11, further comprising:
an outdoor unit configured to accommodate therein one of the first heat exchanger and the second heat exchanger; and

an indoor unit configured to accommodate therein an other of the first heat exchanger and the second heat exchanger.
The refrigeration cycle apparatus of any one of claims 1 to 11, further comprising:
an outdoor unit configured to accommodate therein one of the first heat exchanger and the second heat exchanger, and

a relay device configured to accommodate therein an other of the first heat exchanger and the second heat exchanger, the relay device being separate from the outdoor unit and an indoor unit and installable at a position away from the outdoor unit and the indoor unit.
The refrigeration cycle apparatus of claim 13, wherein the first heat exchanger or the second heat exchanger accommodated in the relay device comprises a heat exchanger configured to allow heat exchange between the refrigerant and a heat medium.
The refrigeration cycle apparatus of any one of claims 12 to 14, wherein the first heat exchanger or the second heat exchanger accommodated in the outdoor unit comprises a heat exchanger configured to allow heat exchange between the refrigerant and a heat medium.
The refrigeration cycle apparatus of any one of claims 12 to 15, further comprising one or a plurality of the outdoor units and one or a plurality of the indoor units, the refrigeration cycle apparatus being configured to supply air temperature-conditioned in each of the one or the plurality of the indoor units to an indoor space.
The refrigeration cycle apparatus of any one of claims 1 to 16, further comprising a refrigerant flow switching device configured to switch a passage of the refrigerant, the refrigeration cycle apparatus being configured to be operable in
a first operation mode being a mode in which one of the first heat exchanger and the second heat exchanger is caused to serve as the condenser and an other of the first heat exchanger and the second heat exchanger is caused to serve as the evaporator, and

a second operation mode being a mode in which the one of the first heat exchanger and the second heat exchanger is caused to serve as the evaporator and the other of the first heat exchanger and the second heat exchanger is caused to serve as the condenser.
The refrigeration cycle apparatus of any one of claims 1 to 17, wherein the substance having such a property as to cause a disproportionation reaction comprises 1, 1, 2-trifluoroethylene.