Working fluids for refrigeration cycles and refrigeration cycle systems

Abstract

In a working fluid for a refrigeration cycle containing fluoroolefin as a refrigerant component and a disproportionation inhibitor, the flammability of the fluid can be effectively suppressed. [Solution] The working fluid for the refrigeration cycle contains a fluoroolefin as a refrigerant component, which undergoes a disproportionation reaction, and also contains a fluoropropane having five or more hydrogen atoms and carbon dioxide (R744) as a disproportionation inhibitor to suppress the disproportionation reaction of the fluoroolefin. Examples of fluoropropane having five or more hydrogen atoms include monofluoropropane, difluoropropane, and trifluoropropane.

Description

Technical Field

[0001] The present disclosure relates to a working medium for refrigeration cycles capable of effectively suppressing or mitigating disproportionation reaction of fluoroolefins (fluoroalkenes) such as 1,1,2-trifluoroethylene, and a refrigeration cycle system using the same. Background Art

[0002] As working media for refrigeration cycles (refrigerants or heat media), HCFC (hydrochlorofluorocarbon) was conventionally used, but HCFC has a great impact on ozone layer depletion. Therefore, in recent years, HFC (hydrofluorocarbon) having an ozone depletion potential (ODP) of 0 has been used. Among such HFCs, the use of fluoroolefins with lower global warming potential (GWP), particularly hydrofluoroolefins (HFOs), has been proposed recently.

[0003] As representative HFOs, for example, 1,1,2-trifluoroethylene (HFO-1123), difluoroethylene (HFO-1132) and the like are known. Compared with conventional HFCs and the like, these HFOs have lower stability and thus are less likely to remain in the atmosphere, resulting in low ODP and GWP. Therefore, as a working medium for refrigeration cycles using such HFOs, for example, those disclosed in Patent Document 1 have been proposed.

[0004] The working medium disclosed in Patent Document 1 contains propane as a first component, at least one of 1,1,2-trifluoroethylene and (E)-1,2-difluoroethylene as a second component, and at least one selected from the group consisting of 2,3,3,3-tetrafluoro-1-propene, (E)-1,3,3,3-tetrafluoropropene, difluoromethane, CO2, CF3I, (Z)-1-chloro-2,3,3,3-tetrafluoropropene, (E)-1-chloro-2,3,3,3-tetrafluoropropene, (E)-1-chloro-3,3,3-trifluoropropene, (E)-1,1,1,4,4,4-hexafluoro-2-butene, (Z)-1,2,3,3,3-pentafluoropropene, and (E)-1,2,3,3,3-pentafluoropropene as a third component.

[0005] Here, it is known that HFO is prone to a self-polymerization reaction called disproportionation (hereinafter referred to as disproportionation reaction) due to its low stability. Disproportionation reactions are easily induced by heat generated during the use of the working fluid in the refrigeration cycle, and since the occurrence of disproportionation reactions is accompanied by a large release of heat, it is known that disproportionation reactions can occur in a chain reaction. As a result, a large amount of soot is generated, which may reduce the reliability of the refrigeration cycle system or the compressor and other components that make up this system. Patent document 1 describes that the coexistence of HFO-1123 and propane can suppress the disproportionation reaction of HFO-1123 (referred to as "polymerization by oxygen" in cited document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2023 / 100746 [Overview of the project] [Problems that the invention aims to solve]

[0007] The working fluid disclosed in Patent Document 1 contains the aforementioned first, second, and third components, and is adjusted so that its combustion heat is less than 19,000 MJ / kg, with the aim of effectively utilizing the first component, propane, as a refrigerant. However, in working fluids for refrigeration cycles that contain fluoroolefins such as HFO, there is a need to further suppress their flammability.

[0008] This disclosure is made to solve these problems, and aims to enable effective suppression of flammability in a working fluid for a refrigeration cycle that contains a fluoroolefin as a refrigerant component and a disproportionation inhibitor. [Means for solving the problem]

[0009] The working fluid for a refrigeration cycle according to this disclosure, in order to solve the above-mentioned problems, contains a fluoroolefin as a refrigerant component that undergoes a disproportionation reaction, and contains fluoropropane having five or more hydrogen atoms and carbon dioxide (R744) as a disproportionation inhibitor to suppress the disproportionation reaction of the fluoroolefin.

[0010] According to the above configuration, the working fluid for a refrigeration cycle containing a fluoroolefin that undergoes a disproportionation reaction contains fluoropropane having five or more hydrogen atoms and carbon dioxide as disproportionation inhibitors. By using such a combination of fluoropropane and carbon dioxide as a disproportionation inhibitor, it is possible to exhibit a disproportionation inhibitory effect that is as good as or better than that of saturated hydrocarbons such as propane, or fluoroalkanes having 1 to 3 carbon atoms with a boiling point of 0°C or lower. Moreover, the combination of fluoropropane having five or more hydrogen atoms and carbon dioxide can further suppress the flammability of the resulting working fluid for a refrigeration cycle. [Effects of the Invention]

[0011] This disclosure provides the effect that, with the above configuration, the flammability of a working fluid for a refrigeration cycle containing a fluoroolefin as a refrigerant component and a disproportionation inhibitor can be effectively suppressed. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows a typical example of a fluoroolefin contained in a working fluid for a refrigeration cycle according to one embodiment of the present invention. [Figure 2] This figure illustrates a fluoropropane having five or more hydrogen atoms contained in a working fluid for a refrigeration cycle according to one embodiment of the present disclosure. [Figure 3] (A) and (B) are schematic block diagrams showing an example of a refrigeration cycle system relating to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0013] The working fluid for a refrigeration cycle according to this disclosure contains a fluoroolefin as a refrigerant component, which undergoes a disproportionation reaction, and also contains fluoropropane having five or more hydrogen atoms and carbon dioxide (R744) as a disproportionation inhibitor to suppress this disproportionation reaction of the fluoroolefin. A typical embodiment of the working fluid for a refrigeration cycle according to this disclosure, as well as its typical uses, will be described in detail below.

[0014] [Refrigerant components] The working fluid for the refrigeration cycle according to this disclosure uses at least a fluoroolefin (fluoroalkene) that undergoes a disproportionation reaction as a refrigerant component.

[0015] Examples of fluoroolefins that undergo such disproportionation reactions include, for example, fluoroethylenes such as 1,1,2-trifluoroethylene (CF2=CHF,HFO-1123), trans-1,2-difluoroethylene (CHF=CHF(E),HFO-1132(E)), cis-1,2-difluoroethylene (CHF=CHF(Z),HFO-1132(Z)), 1,1-difluoroethylene (CF2=CH2,HFO-1132a), and tetrafluoroethylene (CF2=CF2,FO-1114).

[0016] Among these fluoroethylenes, as shown in Figure 1, at least one of 1,1,2-trifluoroethylene (HFO-1123), tetrafluoroethylene (FO-1114), trans-1,2-difluoroethylene (HFO-1132E), or cis-1,2-difluoroethylene (HFO-1132Z) can be suitably used as a refrigerant component. Note that one of these fluoroolefins may be used as a refrigerant component, or two or more may be used in combination.

[0017] These fluoroolefins have a chemical structure in which they possess an ethylene structure as their backbone, i.e., a double bond between two carbon atoms, and at least one of the two hydrogen atoms bonded to one carbon atom is replaced by a fluorine atom, or at least one of the two hydrogen atoms bonded to both carbon atoms is replaced by a fluorine atom. In addition, in fluoroolefins, some of the hydrogen atoms may be replaced by other atoms or other substituents.

[0018] For example, 1,1,2-trifluoroethylene has a structure in which both hydrogen atoms bonded to one carbon atom (the carbon atom at position 1) of the ethylene structure are replaced by fluorine atoms, and one of the two hydrogen atoms bonded to the other carbon atom (the carbon atom at position 2) is replaced by a fluorine atom.

[0019] Alternatively, trans-1,2-difluoroethylene has a structure in which one of the two hydrogen atoms bonded to the carbon atom at position 1 of the ethylene structure is substituted with a fluorine atom, and among the two hydrogen atoms bonded to the carbon atom at position 2, only the hydrogen atom located at a position opposite to the carbon atom at position 1 across the double bond, rather than at an adjacent position, is substituted with a fluorine atom.

[0020] As described above, such a fluoroolefin contains an ethylene skeleton, that is, a carbon-carbon double bond, so this double bond is easily decomposed. Specifically, ozone in the atmosphere generates hydroxyl radicals (OH radicals) through a photochemical reaction, and these hydroxyl radicals can cause an addition reaction to the double bond, thus making the fluoroolefin easily decomposed. Therefore, fluoroolefins have little impact on ozone layer depletion and global warming.

[0021] The working fluid for refrigeration cycles according to the present disclosure may contain other refrigerant components in addition to fluoroolefins as refrigerant components. In this case, if the fluoroolefin is defined as the "main component (main refrigerant component)" of the refrigerant components in the working fluid for refrigeration cycles according to the present disclosure, the other refrigerant components are positioned as the "sub-components (auxiliary refrigerant components)" of the refrigerant components in the working fluid for refrigeration cycles according to the present disclosure.

[0022] Refrigerant components that can be used as a secondary refrigerant component in the working medium for a refrigeration cycle according to the present disclosure are not particularly limited, and various known refrigerant components can be cited. Representative examples include: fluoromethanes such as tetrafluoromethane (FC-14), trifluoromethane (HFC-23), difluoromethane (HFC-32, R32); fluoroethanes such as fluoroethane (HFC-161), pentafluoroethane (HFC-125), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1-difluoroethane (HFC-152a), 1,2-difluoroethane (HFC-152), 1,1,1-trifluoroethane (HFC-143a), 1,1,2-trifluoroethane (HFC-143); fluoropropanes having 4 or less hydrogen atoms such as 1,1,1,2,2-pentafluoropropane (HFC-245cb), 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea); monofluoroethylene (HFO-1141); fluoropropenes such as hexafluoropropene (FC-1216), 2,3,3,3-tetrafluoropropene (HFO-1234yf), trans-1,3,3,3-tetrafluoropropene [(E)-HFO-1234ze], 1,2,3,3,3-pentafluoropropene (HFO-1225ye), 3,3,3-trifluoropropene (HFO-1243zf); fluoroalkanes or fluoroalkenes having a halogen substituent other than a fluoro group, such as 2-chloro-1,1-difluoroethylene (HCFC-1122), 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124), 2-chloro-1,1,2-trifluoroethylene (CFC-1113), trifluoroiodomethane; alkanes or alkenes having 4 or less carbon atoms, such as propane (HC-290, R290), isobutane (HC-600a, R600a), propylene, cyclopropane, isobutylene; ammonia; and the like.

[0023] These auxiliary refrigerant components are known to have little impact on ozone depletion and global warming, and therefore can be used in combination with the aforementioned fluoroolefin (main refrigerant component) as a refrigerant component. The aforementioned auxiliary refrigerant components may be used in combination with fluoroolefin by one type only, or two or more types may be used in combination with fluoroolefin as appropriate.

[0024] These auxiliary refrigerant components are known to have little impact on ozone depletion and global warming, and therefore can be used in combination with fluoroolefins as refrigerant components. These auxiliary refrigerant components may be used individually or in combination of two or more as appropriate.

[0025] Here, fluoroolefins are also known to cause rapid disproportionation reactions due to their good decomposition properties, as mentioned above. As a typical example of a fluoroolefin, let's take 1,1,2-trifluoroethylene as an example. In this disproportionation reaction, a self-decomposition reaction occurs in which the 1,1,2-trifluoroethylene molecules decompose, and following this self-decomposition reaction, a polymerization reaction occurs in which the carbon produced by the decomposition polymerizes to form soot. When active radicals are generated due to heat or other factors under high temperature and high pressure conditions, these active radicals react with 1,1,2-trifluoroethylene to cause the aforementioned disproportionation reaction. Since this disproportionation reaction is exothermic, this heat generates active radicals, which in turn induce further disproportionation reactions. In this way, the generation of active radicals and the occurrence of disproportionation reactions proceed in a chain reaction, causing the disproportionation reaction to proceed rapidly.

[0026] The applicant of this application previously found that disproportionation reactions of fluoroolefins can be effectively suppressed by using fluoroalkanes with a boiling point of 0°C or lower, specifically at least one of fluoroethane with 2 carbon atoms and fluoropropane with 3 carbon atoms (Reference 1: Japanese Patent Application Publication No. 2024-022268).

[0027] Fluoroalkanes with 1 to 3 carbon atoms and a boiling point below 0°C have traditionally been considered unsuitable as disproportionation inhibitors. However, it has become clear that such fluoroalkanes can exhibit good disproportionation inhibitory effects similar to those of saturated hydrocarbons such as propane. Furthermore, it has been found that these fluoroalkanes not only have lower flammability than saturated hydrocarbons, but their relatively low combustion rate also allows for effective suppression of flammability in the resulting working fluid for refrigeration cycles.

[0028] As a result of further intensive research by the inventors, they have uniquely discovered that using fluoropropane, which has five or more hydrogen atoms, among fluoroalkanes with 1 to 3 carbon atoms and a boiling point of 0°C or lower, and combining such fluoropropane with carbon dioxide (R744), not only can the disproportionation reaction be suppressed even more effectively, but the flammability of the resulting working fluid for refrigeration cycles can also be effectively suppressed.

[0029] [Disproportionation inhibitor] The working fluid for a refrigeration cycle according to this disclosure contains fluoropropane having five or more hydrogen atoms and carbon dioxide (R744) as disproportionation inhibitors to suppress the disproportionation reaction of fluoroolefin, which is the main refrigerant component. Since propane has 3 carbon atoms and 8 hydrogen atoms (C3H8), fluoropropane having five or more hydrogen atoms can be said to be fluoropropane in which 1 to 3 of the 8 hydrogen atoms in the propane molecular structure are replaced with fluorine.

[0030] Examples of fluoropropanes having five or more hydrogen atoms include monofluoropropane, difluoropropane, and trifluoropropane, as shown in Figure 2.

[0031] Examples of monofluoropropanes include 1-fluoropropane and 2-fluoropropane. Examples of difluoropropanes include 1,1-difluoropropane, 2,2-difluoropropane, 1,2-difluoropropane, and 1,3-difluoropropane. Examples of trifluoropropanes include 1,1,1-trifluoropropane, 1,1,2-trifluoropropane, 1,2,3-trifluoropropane, 1,2,2-trifluoropropane, and 1,1,3-trifluoropropane.

[0032] Among these fluoropropanes, more preferred are 1-fluoropropane, 2-fluoropropane, 1,1-difluoropropane, 2,2-difluoropropane, 1,1,1-trifluoropropane, 1,1,2-trifluoropropane, and 1,2,2-trifluoropropane, and even more preferred are 2-fluoropropane, 2,2-difluoropropane, and 1,1,1-trifluoropropane. These fluoropropanes may be used individually as disproportionation inhibitors, or two or more may be used in appropriate combinations.

[0033] In the working fluid for refrigeration cycles according to this disclosure, these fluoropropanes are used as disproportionation inhibitors in combination with carbon dioxide (R744). Carbon dioxide has been conventionally known as a natural refrigerant. By combining carbon dioxide with fluoropropane having five or more hydrogen atoms, the disproportionation reaction of fluoroolefins can be effectively suppressed, and the flammability of the resulting working fluid for refrigeration cycles can be effectively suppressed.

[0034] In the examples described later, 2-fluoropropane (Examples 1 and 2) and 2,2-difluoropropane (Example 3) were used as fluoropropanes having five or more hydrogen atoms.

[0035] [Content of disproportionation inhibitors and auxiliary refrigerant components] Next, the content (amount added) of the disproportionation inhibitor mentioned above will be explained in detail. In the working fluid for refrigeration cycles according to this disclosure, as described above, a combination of fluoropropane having five or more hydrogen atoms and carbon dioxide is used as the disproportionation inhibitor. Furthermore, in the working fluid for refrigeration cycles according to this disclosure, as described above, the refrigerant component only needs to contain at least fluoroolefin, which is the main refrigerant component, but a combination of secondary refrigerant components can also be used with this main refrigerant component.

[0036] Here, for convenience, the total amount of refrigerant components and disproportionation inhibitors is referred to as "total amount of refrigerant-related components," and when this total amount of refrigerant-related components is set to 100% by mass, the upper limit of the content (amount added) of fluoropropane having 5 or more hydrogen atoms in the working fluid for the refrigeration cycle according to this disclosure is not particularly limited, but may be 30% by mass or less of the total amount of refrigerant-related components, 25% by mass or less, 20% by mass or less, 18% by mass or less, or 15% by mass or less.

[0037] If the content of fluoropropane containing five or more hydrogen atoms exceeds 30% by mass of the total amount of refrigerant components, the fluoropropane content may become too high when viewed as a working fluid for a refrigeration cycle, potentially preventing it from exhibiting good physical properties as a "refrigerant." Of course, depending on the composition of the working fluid for a refrigeration cycle, it goes without saying that it is acceptable to add fluoropropane containing five or more hydrogen atoms at a concentration of 30% by mass or more of the total amount of refrigerant components.

[0038] Furthermore, the upper limit of the carbon dioxide content (amount added) in the working fluid for the refrigeration cycle according to this disclosure is not particularly limited, but may be 20% by mass or less of the total amount of refrigerant-related components, 17% by mass or less, 15% by mass or less, or 10% by mass or less.

[0039] If the carbon dioxide content exceeds 20% by mass of the total amount of refrigerant components, the carbon dioxide content becomes too high when viewed as a working fluid for a refrigeration cycle, potentially preventing it from exhibiting good physical properties as a "refrigerant." Of course, depending on the composition of the working fluid for a refrigeration cycle, it goes without saying that adding more than 20% by mass of carbon dioxide to the total amount of refrigerant components is acceptable.

[0040] Furthermore, there are no particular limitations on the lower limits of the content of fluoropropane and carbon dioxide as disproportionation inhibitors. Typical lower limits include 1% by mass or more of either fluoropropane or carbon dioxide relative to the total amount of refrigerant components. Under various conditions, it is possible to obtain effects such as suppression of disproportionation reactions even if the content of either fluoropropane or carbon dioxide is less than 1% by mass. However, if the content of either fluoropropane or carbon dioxide is 1% by mass or more, the effects such as suppression of disproportionation reactions can be more favorably achieved.

[0041] Furthermore, generally speaking, in working fluids for refrigeration cycles, the amount of impurities contained in the refrigerant component is often 2-3% by mass or less. For example, commercially available 1,1,2-trifluoroethylene, a typical fluoroolefin, is known to have a purity of about 97% by mass. Impurities contained in this commercially available product include residues or by-products of the synthesis raw materials, and these impurities are contained in amounts of less than 3% by mass. In this disclosure, the lower limit of the content of fluoropropane and carbon dioxide, which are disproportionation inhibitors, may be equal to or greater than the impurity content of commercially available products, i.e., 3% by mass or more.

[0042] Furthermore, as shown in the examples described later, when fluoropropane and carbon dioxide are used in combination, the effect of suppressing disproportionation reactions and flammability is obtained with a content of 4.5% by mass (Example 4). Therefore, the lower limit of the carbon dioxide content in this disclosure can be, for example, 4.5% by mass or more.

[0043] Furthermore, the amount (content) of fluoropropane and carbon dioxide, which are disproportionation inhibitors, can be adjusted according to various conditions and therefore cannot necessarily be specified. For this reason, the upper and lower limits of fluoropropane and carbon dioxide content mentioned above are merely representative and preferred examples.

[0044] The content of auxiliary refrigerant components in the working fluid for the refrigeration cycle is not particularly limited. As stated above, in this disclosure, fluoroolefin is the main refrigerant component, so in the working fluid for the refrigeration cycle according to this disclosure, it is sufficient that the content of fluoroolefin is greater than the content of auxiliary refrigerant components. The specific upper limit of the content of auxiliary refrigerant components is not particularly limited, but typically it can be 30% by mass or less of the total amount of refrigerant-related components, and may also be 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less.

[0045] In the working fluid for refrigeration cycles according to this disclosure, it is important to minimize the GWP (Gross Wavelength). Specifically, a GWP of 200 or less is desirable (GWP ≤ 200), and a GWP of 150 or less is more desirable (GWP ≤ 150). If the refrigerant component is only fluoroolefin, which is the main refrigerant component, it is easy to keep the GWP at 200 or less. However, when a secondary refrigerant component is used in combination with the main refrigerant component, depending on the type of secondary refrigerant component, it becomes easier to adjust the GWP of the working fluid for refrigeration cycles to 200 or less by keeping it at 30% by mass or less.

[0046] Furthermore, there are no particular limitations on the lower limit of the content of auxiliary refrigerant components. In the working fluid for refrigeration cycles according to this disclosure, the refrigerant component only needs to contain fluoroolefin, which is the main refrigerant component, and does not need to contain auxiliary refrigerant components. Therefore, the lower limit of the content of auxiliary refrigerant components is 0% by mass or more.

[0047] Furthermore, the content of fluoroolefin, the main refrigerant component, is the remainder after subtracting the content of the disproportionation inhibitor (the content of fluoropropane and carbon dioxide having five or more hydrogen atoms) from the total amount of refrigerant-related components. If a secondary refrigerant component is present, the content of the main refrigerant component is the remainder after subtracting the content of the disproportionation inhibitor and the secondary refrigerant component from the total amount of refrigerant-related components.

[0048] [Other ingredients that can be used in combination] The working medium for refrigeration cycles according to this disclosure is used in a refrigeration cycle system and can therefore be used in combination with lubricating oil (refrigeration oil) that lubricates the compressor of the refrigeration cycle system.

[0049] As described above, the working fluid for a refrigeration cycle according to this disclosure may use a combination of fluoroolefins (e.g., 1,1,2-trifluoroethylene, etc.) and difluoromethane as refrigerant components that undergo disproportionation reactions, and at least a fluoroalkane as a disproportionation inhibitor. Furthermore, when the working fluid for a refrigeration cycle is used in combination with lubricating oil, the working fluid-containing composition can be considered to consist of a refrigerant component, a disproportionation inhibitor, a lubricating oil component, and other components. In the working fluid for a refrigeration cycle according to this disclosure, the disproportionation inhibitor is usually mixed with the refrigerant component, but may be mixed with the lubricating oil component depending on the circumstances.

[0050] The lubricating oil component contained in the working fluid-containing composition (used in combination with the working fluid for the refrigeration cycle) can suitably use various lubricating oils known for refrigeration cycle systems. Specific examples of lubricating oils include, but are not limited to, ester-based lubricating oils, ether-based lubricating oils, glycol-based lubricating oils, alkylbenzene-based lubricating oils, fluorine-based lubricating oils, mineral oils, hydrocarbon-based synthetic oils, etc. These lubricating oils may be used individually or in appropriate combinations of two or more types.

[0051] Furthermore, various known additives other than disproportionation inhibitors may be added to the working fluid-containing composition. Specific examples of additives include, but are not limited to, antioxidants, moisture scavengers, metal deactivators, anti-wear agents, and defoamers. Antioxidants are used to improve the thermal stability, oxidation resistance, and chemical stability of the refrigerant component or lubricating oil. Moisture scavengers are used to remove moisture that has entered the refrigeration cycle system, and in particular to suppress changes in the properties of the lubricating oil. Metal deactivators are used to suppress or prevent chemical reactions caused by the catalytic action of metal components. Anti-wear agents are used to reduce wear on sliding parts in the compressor, especially wear during high-pressure operation. Defoamers are used to suppress the generation of bubbles in the lubricating oil.

[0052] The specific types of these additives are not particularly limited, and known compounds can be suitably used depending on the conditions. Furthermore, only one type of compound may be used as an additive, or two or more types of compounds may be used in appropriate combination. Moreover, the amount of these additives added is not particularly limited, and they can be added within a known range as long as the properties of the refrigeration cycle working medium according to this disclosure, or the working medium-containing composition containing it, are not impaired.

[0053] Furthermore, the working fluid for refrigeration cycles according to this disclosure may not contain other components. For example, in Examples 1 to 3 described later, only 1,1,2-trifluoroethylene from the fluoroolefins, which are the main refrigerant components, is used as the refrigerant component, and a combination of 2-fluoropropane and carbon dioxide, or a combination of 2,2-difluoropropane and carbon dioxide, is used as the disproportionation inhibitor. The working fluids for refrigeration cycles according to Examples 1 to 3 consist only of fluoroolefins, fluoropropane having five or more hydrogen atoms, and carbon dioxide, and do not contain other components including secondary refrigerant components.

[0054] [Example of a refrigeration cycle system configuration] Next, an example of a refrigeration cycle system configured using the working fluid for refrigeration cycles related to this disclosure will be described with reference to Figures 3(A) and 3(B).

[0055] The specific configuration of the refrigeration cycle system relating to this disclosure is not particularly limited, and any configuration in which components such as a compressor, condenser, expansion means, and evaporator are connected by piping is acceptable. Specific application examples of the refrigeration cycle system relating to this disclosure are also not particularly limited, and examples include air conditioners, refrigerators (household and commercial), dehumidifiers, display cases, ice makers, heat pump water heaters, heat pump washer-dryers, vending machines, etc.

[0056] As a typical application example of the refrigeration cycle system according to this disclosure, an air conditioning system will be described. Specifically, as schematically shown in the block diagram of Figure 3(A), the air conditioning system 10 according to this embodiment comprises an indoor unit 11 and an outdoor unit 12, and piping 13 connecting them. The indoor unit 11 is equipped with a heat exchanger 14, and the outdoor unit 12 is equipped with a heat exchanger 15, a compressor 16, and a pressure reducing device 17.

[0057] The heat exchanger 14 of the indoor unit 11 and the heat exchanger 15 of the outdoor unit 12 are connected in a ring by piping 13, thereby forming a refrigeration cycle. Specifically, the heat exchanger 14 of the indoor unit 11, the compressor 16, the heat exchanger 15 of the outdoor unit 12, and the pressure reducing device 17 are connected in a ring by piping 13 in that order. In addition, a four-way valve 18 for switching between heating and cooling is provided in the piping 13 connecting the heat exchanger 14, the compressor 16, and the heat exchanger 15. The indoor unit 11 is equipped with a blower fan, temperature sensor, control panel, etc. (not shown), and the outdoor unit 12 is equipped with a blower, accumulator, etc. (not shown). Furthermore, various valve devices (including the four-way valve 18), strainers, etc. (not shown) are provided in the piping 13.

[0058] The heat exchanger 14 in the indoor unit 11 performs heat exchange between indoor air drawn into the indoor unit 11 by a blower fan and the refrigerant flowing inside the heat exchanger 14. When heating, the indoor unit 11 blows air heated by heat exchange into the room, and when cooling, it blows air cooled by heat exchange into the room. The heat exchanger 15 in the outdoor unit 12 performs heat exchange between outside air drawn into the outdoor unit 12 by a blower and the refrigerant flowing inside the heat exchanger 15.

[0059] The specific configurations of the indoor unit 11 and the outdoor unit 12, or the specific configurations of the heat exchanger 14 or heat exchanger 15, compressor 16, pressure reducing device 17, four-way valve 18, blower fan, temperature sensor, control unit, blower, accumulator, other valve devices, strainer, etc., are not particularly limited, and known configurations can be suitably used.

[0060] An example of the operation of the air conditioning system 10 shown in Figure 3(A) will be explained in detail. First, in cooling or dehumidifying operation, the compressor 16 of the outdoor unit 12 compresses and discharges the gaseous refrigerant, which is then sent to the heat exchanger 15 of the outdoor unit 12 via the four-way valve 18. The heat exchanger 15 exchanges heat with the outside air, so the gaseous refrigerant condenses and liquefies. The liquefied liquid refrigerant is depressurized by the depressurizing device 17 and sent to the heat exchanger 14 of the indoor unit 11. In the heat exchanger 14, the liquid refrigerant evaporates due to heat exchange with the indoor air and becomes gaseous refrigerant. This gaseous refrigerant returns to the compressor 16 of the outdoor unit 12 via the four-way valve 18. The compressor 16 compresses the gaseous refrigerant and discharges it again to the heat exchanger 15 via the four-way valve 18.

[0061] In addition, during heating operation, the compressor 16 of the outdoor unit 12 compresses and discharges the gaseous refrigerant, which is then sent to the heat exchanger 14 of the indoor unit 11 via the four-way valve 18. In the heat exchanger 14, the gaseous refrigerant condenses and liquefies through heat exchange with the indoor air. The liquefied liquid refrigerant is then depressurized by the depressurization device 17 to become a gaseous two-phase refrigerant, which is then sent to the heat exchanger 15 of the outdoor unit 12. The heat exchanger 15 exchanges heat between the outside air and the gaseous two-phase refrigerant, so the gaseous two-phase refrigerant evaporates and becomes a gaseous refrigerant, which returns to the compressor 16. The compressor 16 compresses the gaseous refrigerant and discharges it again to the heat exchanger 14 of the indoor unit 11 via the four-way valve 18.

[0062] Furthermore, as another typical application example of the refrigeration cycle system according to this disclosure, a refrigerator will be used as an example. Specifically, for example, as schematically shown in the block diagram of Figure 3(B), the refrigerator 20 according to this embodiment includes a compressor 21, a condenser 22, a pressure reducing device 23, an evaporator 24, and piping 25, etc. The refrigerator 20 also includes a main body housing, a blower, an operating unit, a control unit, etc., although these are not shown.

[0063] The compressor 21 compresses the refrigerant gas into a high-temperature, high-pressure gaseous refrigerant. The condenser 22 cools the refrigerant and liquefies it. The pressure reducing device 23, for example, is composed of a capillary tube and reduces the pressure of the liquefied refrigerant (liquid refrigerant). The evaporator 24 evaporates the refrigerant into a low-temperature, low-pressure gaseous refrigerant. The compressor 21, condenser 22, pressure reducing device 23, and evaporator 24 are connected in this order in a ring by piping 25 through which the refrigerant gas flows, thereby forming a refrigeration cycle.

[0064] The configuration of the compressor 21, condenser 22, pressure reducing device 23, evaporator 24, piping 25, main body housing, blower, operating unit, control unit, etc., is not particularly limited, and known configurations can be suitably used. Furthermore, the refrigerator 20 may also have other known configurations.

[0065] An example of the operation of the refrigerator 20 shown in Figure 3(B) will be explained in detail. The compressor 21 compresses the gaseous refrigerant and discharges it to the condenser 22. The condenser 22 cools the gaseous refrigerant to liquid refrigerant. The liquid refrigerant is depressurized by passing through the depressurization device 23 and sent to the evaporator 24. In the evaporator 24, the liquid refrigerant vaporizes by absorbing heat from the surroundings, becoming gaseous refrigerant and returning to the compressor 21. The compressor 21 compresses the gaseous refrigerant and discharges it again to the condenser 22.

[0066] Such an air conditioner 10 or refrigerator 20 is a refrigeration cycle system configured using the aforementioned refrigeration cycle working fluid. The refrigeration cycle working fluid according to this disclosure uses fluoroolefin as the main refrigerant component, and this fluoroolefin has good properties as a refrigerant component and has low ODP and GWP. Moreover, the refrigeration cycle working fluid according to this disclosure uses fluoropropane having five or more hydrogen atoms and carbon dioxide (R744) in combination as disproportionation inhibitors.

[0067] As a result, the working fluid for the refrigeration cycle according to this disclosure can exhibit a disproportionation suppression effect similar to or better than that of saturated hydrocarbons such as propane, or fluoroalkanes with 1 to 3 carbon atoms and a boiling point of 0°C or lower. Moreover, the combination of fluoropropane having five or more hydrogen atoms and carbon dioxide can further suppress the flammability of the resulting working fluid for the refrigeration cycle. As a result, the refrigeration cycle system according to this disclosure can have a smaller impact on the environment, be more efficient, and be more practical. [Examples]

[0068] This disclosure will be described more specifically with reference to examples, comparative examples, and reference examples, but is not limited thereto. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of this disclosure.

[0069] (Evaluation of the suppression of disproportionation reactions) A pressure sensor for measuring the internal pressure, a thermocouple for measuring the internal temperature, and a discharge device for generating a discharge within a sealed pressure vessel (internal volume 50 mL) were attached to the vessel.

[0070] Furthermore, as the main refrigerant component, fluoroolefin, a gas cylinder containing 1,1,2-trifluoroethylene (with 5% limonene (liquid phase) as a stabilizer) (HFO-1123 gas cylinder) was connected to a pressure-resistant container in a way that allowed for pressure adjustment. In addition, in the examples or comparative examples described later, a gas cylinder containing a disproportionation inhibitor was also connected to the pressure-resistant container in a way that allowed for pressure adjustment, along with the HFO-1123 gas cylinder.

[0071] To heat the entire pressure vessel to which these gas cylinders were connected, two mantle heaters were installed, and a ribbon heater was also installed to heat the piping. The pressure sensor and thermometer attached to the pressure vessel were connected to a data logger. This established an experimental system for the disproportionation reaction.

[0072] Using this disproportionation reaction experimental system, the suppression of disproportionation reactions was evaluated for working fluids for refrigeration cycles related to the reference example, comparative example, or example. As conditions to induce the disproportionation reaction of 1,1,2-trifluoroethylene, we adopted either [Disproportionation Condition 1] a high-temperature and high-pressure condition with an internal temperature of 150°C and an internal pressure of 2 MPa under which a discharge was generated by a discharge device at a discharge voltage of 100 V, or [Disproportionation Condition 2] a high-temperature and high-pressure condition with an internal temperature of 150°C and an internal pressure of 6 MPa under which a discharge was generated by a discharge device at a discharge voltage of 300 V.

[0073] These disproportionation conditions induced a disproportionation reaction of 1,1,2-trifluoroethylene in the working fluid for the refrigeration cycle within the pressure vessel in the experimental system. If a significant increase in pressure and temperature was observed within the pressure vessel, and soot was found to be generated inside the pressure vessel, it was evaluated that the disproportionation reaction was not suppressed (×). Conversely, if no significant increase in pressure or temperature was observed, and no soot was found inside the pressure vessel, it was evaluated that the disproportionation reaction was suppressed (○).

[0074] (Evaluation of flammability) Based on the combustion rate evaluation method (Schlieren method) described in paragraphs 0079 and 0080 of Japanese Patent Publication No. 6879411 (Reference 2), the combustion rates of the working fluids for refrigeration cycles in the comparative examples and examples were evaluated. If the flammability class was 2L (slightly flammable) or less according to ISO 817:2014, it was evaluated as having low flammability and being usable (○). If the flammability class was 2L or higher, it was evaluated as having high flammability and being unusable (×).

[0075] (Reference example) In the experimental setup described above, 1,1,2-trifluoroethylene was introduced into the pressure vessel solely from an HFO-1123 gas cylinder. This prepared the working fluid for the refrigeration cycle described in the reference example in a heat-resistant container. The composition of this working fluid for the refrigeration cycle is 100% by mass of 1,1,2-trifluoroethylene, as shown in Table 1.

[0076] As mentioned above, the suppression of the disproportionation reaction was evaluated for the working fluid for the refrigeration cycle in this reference example using disproportionation condition 1. The results are shown in Table 1. Note that the combustion rate was not evaluated in this reference example.

[0077] (Comparative Example 1) In the experimental setup described above, a 2-fluoropropane gas cylinder was connected to a pressure-resistant container along with an HFO-1123 gas cylinder to allow for pressure adjustment. 1,1,2-trifluoroethylene was introduced into the pressure-resistant container from the HFO-1123 gas cylinder, and the amount of 2-fluoropropane introduced as a disproportionation inhibitor was adjusted to a content of 20% by mass.

[0078] This allowed the working fluid for the refrigeration cycle according to Comparative Example 1 to be prepared in a heat-resistant container. The composition of this working fluid for the refrigeration cycle is 80% by mass of 1,1,2-trifluoroethylene and 20% by mass of 2-fluoropropane, as shown in Table 1.

[0079] As described above, the suppression of the disproportionation reaction and the flammability of the working fluid for the refrigeration cycle in Comparative Example 1 were evaluated under disproportionation conditions 1 and 2. The results are shown in Table 1.

[0080] (Comparative Example 2) In the experimental setup described above, a propane (R290) gas cylinder was connected to a pressure-resistant container along with an HFO-1123 gas cylinder to allow for pressure adjustment. 1,1,2-trifluoroethylene was introduced into the pressure-resistant container from the HFO-1123 gas cylinder, and the amount of propane introduced as a disproportionation inhibitor was adjusted to a content of 10% by mass, while the amount of carbon dioxide introduced was also adjusted to a content of 10% by mass.

[0081] This allowed us to prepare the working fluid for the refrigeration cycle according to Comparative Example 2 in a heat-resistant container. The composition of this working fluid for the refrigeration cycle is as shown in Table 1: 80% by mass of 1,1,2-trifluoroethylene, 10% by mass of olopropane, and 10% by mass of carbon dioxide.

[0082] As described above, the suppression of the disproportionation reaction and the flammability of the working fluid for the refrigeration cycle in Comparative Example 2 were evaluated under disproportionation conditions 1 and 2. The results are shown in Table 1.

[0083] (Example 1) In the experimental setup described above, a 2-fluoropropane gas cylinder and a carbon dioxide (R744) gas cylinder were connected to a pressure-resistant container in a manner that allowed for pressure adjustment, along with an HFO-1123 gas cylinder. 1,1,2-trifluoroethylene was introduced into the pressure-resistant container from the HFO-1123 gas cylinder, and the amount of 2-fluoropropane introduced was adjusted to a 10% by mass content as a disproportionation inhibitor, while the amount of carbon dioxide introduced was also adjusted to a 10% by mass content.

[0084] This allowed the working fluid for the refrigeration cycle according to Example 1 to be prepared in a heat-resistant container. The composition of this working fluid for the refrigeration cycle is as shown in Table 1: 80% by mass of 1,1,2-trifluoroethylene, 10% by mass of 2-fluoropropane, and 10% by mass of carbon dioxide.

[0085] As described above, the suppression of the disproportionation reaction and the flammability of the working fluid for the refrigeration cycle according to this Example 1 were evaluated using disproportionation conditions 1 and 2. The results are shown in Table 1.

[0086] (Example 2) In the experimental setup described above, a 2-fluoropropane gas cylinder and a carbon dioxide (R744) gas cylinder were connected to a pressure-resistant container in a manner that allowed for pressure adjustment, along with an HFO-1123 gas cylinder. 1,1,2-trifluoroethylene was introduced into the pressure-resistant container from the HFO-1123 gas cylinder, and the amount of 2-fluoropropane introduced was adjusted to a content of 13.5% by mass, while the amount of carbon dioxide introduced was adjusted to a content of 10% by mass, as disproportionation inhibitors.

[0087] This allowed the refrigeration cycle working fluid according to Example 2 to be prepared in a heat-resistant container. As shown in Table 1, the composition of this refrigeration cycle working fluid is 76.5% by mass of 1,1,2-trifluoroethylene, 13.5% by mass of 2-fluoropropane, and 10% by mass of carbon dioxide. The 13.5% by mass content of 2-fluoropropane in Example 2 was adjusted to be approximately the same molar ratio as the propane (R290) content (10% by mass) in Comparative Example 2.

[0088] As described above, the suppression of the disproportionation reaction and the flammability of the working fluid for the refrigeration cycle according to this Example 2 were evaluated using disproportionation conditions 1 and 2. The results are shown in Table 1.

[0089] (Example 3) In the experimental setup described above, a 2,2-difluoropropane gas cylinder and a carbon dioxide (R744) gas cylinder were connected to a pressure-resistant container in a manner that allowed for pressure adjustment, along with an HFO-1123 gas cylinder. 1,1,2-trifluoroethylene was introduced into the pressure-resistant container from the HFO-1123 gas cylinder, and the amount of 2,2-difluoropropane introduced was adjusted to a content of 17% by mass, while the amount of carbon dioxide introduced was adjusted to a content of 9% by mass, as disproportionation inhibitors.

[0090] This allowed the refrigeration cycle working medium according to Example 3 to be prepared in a heat-resistant container. As shown in Table 1, the composition of this refrigeration cycle working medium is 74% by mass of 1,1,2-trifluoroethylene, 17% by mass of 2,2-difluoropropane, and 9% by mass of carbon dioxide. The 17% by mass content of 2,2-difluoropropane in Example 3 was adjusted to be approximately the same molar ratio as the propane (R290) content (10% by mass) in Comparative Example 2, or the 2-fluoropropane content (13.5% by mass) in Example 2.

[0091] As described above, the suppression of the disproportionation reaction and the flammability of the working fluid for the refrigeration cycle according to this Example 3 were evaluated using disproportionation conditions 1 and 2. The results are shown in Table 1.

[0092] (Example 4) In the experimental setup described above, a gas cylinder containing 1,1,1-trifluoropropane and a gas cylinder containing carbon dioxide (R744) were connected to a pressure-resistant container along with an HFO-1123 gas cylinder to allow for pressure adjustment. 1,1,2-trifluoroethylene was introduced into the pressure-resistant container from the HFO-1123 gas cylinder, and the amount of 1,1,1-trifluoropropane introduced was adjusted to a content of 20% by mass, while the amount of carbon dioxide introduced was adjusted to a content of 4.5% by mass, as a disproportionation inhibitor.

[0093] This allowed the refrigeration cycle working medium according to Example 4 to be prepared in a heat-resistant container. As shown in Table 1, the composition of this refrigeration cycle working medium is 75.5% by mass of 1,1,2-trifluoroethylene, 20% by mass of 1,1,1-trifluoropropane, and 4.5% by mass of carbon dioxide. The 20% by mass content of 1,1,1-trifluoropropane in Example 4 was adjusted to have approximately the same molar ratio as the propane (R290) content (10% by mass) in Comparative Example 2 and the 2-fluoropropane content (13.5% by mass) in Example 2.

[0094] As described above, the suppression of the disproportionation reaction and the flammability of the working fluid for the refrigeration cycle according to this Example 4 were evaluated using disproportionation conditions 1 and 2. The results are shown in Table 1.

[0095] (Example 5) The refrigeration cycle working medium according to Example 5 was prepared in a heat-resistant container in the same manner as in Example 4, except that the amount of each gas introduced was adjusted to increase the carbon dioxide content to 7% by mass while maintaining 20% ​​by mass of 1,1,1-trifluoropropane. The composition of this refrigeration cycle working medium is as shown in Table 1: 73% by mass of 1,1,2-trifluoroethylene, 20% by mass of 1,1,1-trifluoropropane, and 7% by mass of carbon dioxide.

[0096] As described above, the suppression of the disproportionation reaction and the flammability of the working fluid for the refrigeration cycle in this Example 5 were evaluated using disproportionation conditions 1 and 2. The results are shown in Table 1.

[0097] (Example 6) The refrigeration cycle working medium according to Example 6 was prepared in a heat-resistant container in the same manner as in Example 4, except that the amount of each gas introduced was adjusted to increase the carbon dioxide content to 9% by mass while maintaining 20% ​​by mass of 1,1,1-trifluoropropane. The composition of this refrigeration cycle working medium is as shown in Table 1: 71% by mass of 1,1,2-trifluoroethylene, 20% by mass of 1,1,1-trifluoropropane, and 9% by mass of carbon dioxide.

[0098] As described above, the suppression of the disproportionation reaction and the flammability of the working fluid for the refrigeration cycle according to this Example 6 were evaluated using disproportionation conditions 1 and 2. The results are shown in Table 1.

[0099] [Table 1]

[0100] (Comparison of Examples and Comparative Examples) As is clear from the comparison between Example 1 and Comparative Example 1, when the mass ratio of 1,1,2-trifluoroethylene is adjusted to be the same, the disproportionation reaction can be similarly suppressed under disproportionation condition 1, whether the disproportionation inhibitor is 2-fluoropropane only (Comparative Example 1) or 2-fluoropropane and carbon dioxide used in combination as disproportionation inhibitors (Example 1).

[0101] Furthermore, it was found that when 2-fluoropropane alone was used (Comparative Example 1), the flammability was high, whereas when 2-fluoropropane and carbon dioxide were used in combination as disproportionation inhibitors (Example 1), the flammability could be reduced.

[0102] Furthermore, in Example 2, the molar ratio of the main refrigerant component (1,1,2-trifluoroethylene) and the disproportionation inhibitor (2-fluoropropane and carbon dioxide) was adjusted to be the same as in Comparative Example 1. In Example 1, the disproportionation reaction could be suppressed under disproportionation condition 1, but it could not be sufficiently suppressed under the more severe condition of disproportionation condition 2. In contrast, in Example 2, the disproportionation reaction could be well suppressed under both disproportionation condition 1 and disproportionation condition 2, and the flammability could be reduced in the same way as in Example 1.

[0103] In other words, when the molar ratio is adjusted to be the same, it can be seen that using 2-fluoropropane and carbon dioxide together as disproportionation inhibitors suppresses the disproportionation reaction more effectively than using 2-fluoropropane alone, and also reduces flammability.

[0104] In Comparative Example 1, only 2-fluoropropane was used as a disproportionation inhibitor, while in Comparative Example 2, propane (R290) and carbon dioxide were used in combination as disproportionation inhibitors. In Comparative Example 2, the disproportionation reaction was well suppressed under both disproportionation condition 1 and disproportionation condition 2, but the flammability was high due to the use of propane. In contrast, in Example 2, the content of 2-fluoropropane among the disproportionation inhibitors was adjusted to be the same as the content of propane in molar ratio, compared to Comparative Example 2. In Example 2, the disproportionation reaction was well suppressed under both disproportionation condition 1 and disproportionation condition 2, similar to Comparative Example 2, and the flammability was lower compared to Comparative Example 2.

[0105] In other words, when comparing the case where propane and carbon dioxide are used together as disproportionation inhibitors (Comparative Example 2) with the case where 2-fluoropropane and carbon dioxide are used together (Example 2), it can be seen that under conditions where the molar ratio of propane or 2-fluoropropane is approximately the same, both can suppress the disproportionation reaction well, but the case using 2-fluoropropane (Example 2) can reduce flammability more effectively.

[0106] Furthermore, in Example 3, 2,2-difluoropropane was used as the disproportionation inhibitor in almost the same molar ratio as 2-fluoropropane (monofluoropropane) used in Example 2. Therefore, the molar ratio of 2,2-difluoropropane in Example 3 is almost the same as the molar ratio of propane (R290) in Comparative Example 2. Thus, even when difluoropropane is used in combination with carbon dioxide instead of monofluoropropane as a disproportionation inhibitor (Example 3), the disproportionation reaction can be effectively suppressed under both disproportionation condition 1 and disproportionation condition 2, similar to Example 2, and the flammability can be reduced compared to Comparative Example 2.

[0107] In Examples 4-6, 1,1,1-trifluoropropane was used as the disproportionation inhibitor in approximately the same molar ratio as 2-fluoropropane (Example 2) or 2,2-difluoropropane (Example 3). Therefore, the molar ratio of 1,1,1-trifluoropropane in Examples 4-6 is approximately the same as the molar ratio of propane (R290) in Comparative Example 2. Thus, even when trifluoropropane is used in combination with carbon dioxide as a disproportionation inhibitor instead of monofluoropropane or difluoropropane (Examples 4-6), it can be seen that the disproportionation reaction can be effectively suppressed, at least under disproportionation condition 1, as in Example 1 or Example 2, and the flammability can be reduced compared to Comparative Example 1 or Comparative Example 2.

[0108] In Example 4, the carbon dioxide content was 4.5% by mass, and under disproportionation condition 1, the disproportionation reaction was suppressed and flammability was also reduced. However, in Example 4, similar to Example 1, the disproportionation reaction was not sufficiently suppressed under the more severe condition of disproportionation condition 2. In contrast, in Examples 5 (7% by mass) and 6 (9% by mass), in which the carbon dioxide content was increased, the disproportionation reaction was well suppressed under both disproportionation condition 1 and disproportionation condition 2, and flammability was reduced, similar to Example 4.

[0109] Furthermore, comparing Examples 2, 3, 5, and 6, it can be seen that if monofluoropropane, difluoropropane, and trifluoropropane are present in almost the same molar ratio as disproportionation inhibitors, and the carbon dioxide content is also approximately the same, then in all cases, the disproportionation reaction can be effectively suppressed, and the flammability can be kept low.

[0110] (Note) Based on the descriptions of the embodiments described above, the following technologies are disclosed in this specification. (Technology 1) A working fluid for a refrigeration cycle, comprising a fluoroolefin as a refrigerant component that undergoes a disproportionation reaction, and a fluoropropane having five or more hydrogen atoms and carbon dioxide (R744) as disproportionation inhibitors that suppress the disproportionation reaction of the fluoroolefin.

[0111] According to the above configuration, the working fluid for a refrigeration cycle containing a fluoroolefin that undergoes a disproportionation reaction contains fluoropropane having five or more hydrogen atoms and carbon dioxide as disproportionation inhibitors. By using such a combination of fluoropropane and carbon dioxide as a disproportionation inhibitor, it is possible to exhibit a disproportionation inhibitory effect that is as good as or better than that of saturated hydrocarbons such as propane, or fluoroalkanes having 1 to 3 carbon atoms with a boiling point of 0°C or lower. Moreover, the combination of fluoropropane having five or more hydrogen atoms and carbon dioxide can further suppress the flammability of the resulting working fluid for a refrigeration cycle.

[0112] (Technical 2) The fluoroolefin is at least one of 1,1,2-trifluoroethylene (HFO-1123), tetrafluoroethylene (FO-1114), trans-1,2-difluoroethylene (HFO-1132E), and cis-1,2-difluoroethylene (HFO-1132Z), the working fluid for a refrigeration cycle according to Technical 1.

[0113] (Technical 3) The working medium for a refrigeration cycle according to Technical 1 or Technical 2, wherein the fluoropropane is at least one of monofluoropropane, difluoropropane, and trifluoropropane.

[0114] (Technical 4) A working fluid for a refrigeration cycle according to any one of Technical 1 to 3, wherein the fluoroolefin is used as the main refrigerant component, and the refrigerant component further contains at least one secondary refrigerant component selected from the group consisting of fluoromethane, fluoroethane, fluoropropane having four or fewer hydrogen atoms, fluoropropene, fluoroalkane or fluoroalkene having halogen substituents other than a fluoro group, alkane or alkene having four or fewer carbon atoms, and ammonia.

[0115] (Technical 5) A working fluid for a refrigeration cycle according to any one of Technical 1 to Technical 4, wherein the content of fluoropropane is 30% by mass or less when the total amount of the refrigerant component and the disproportionation inhibitor is 100% by mass.

[0116] (Technical 6) A working fluid for a refrigeration cycle according to any one of Technical 1 to Technical 5, wherein the carbon dioxide content is 20% by mass or less when the total amount of the refrigerant component and the disproportionation inhibitor is 100% by mass.

[0117] (Technical 7) A working fluid for a refrigeration cycle according to any one of Technical 4 to Technical 6, wherein when the total amount of the refrigerant component and the disproportionation inhibitor is 100% by mass, the content of the auxiliary refrigerant component is 30% by mass or less.

[0118] (Technology 8) A refrigeration cycle system configured using a working fluid for a refrigeration cycle described in any one of Technology 1 to Technology 7.

[0119] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Therefore, embodiments obtained by appropriately combining the technical means disclosed in different embodiments or multiple modifications are also included in the technical scope of this disclosure. [Industrial applicability]

[0120] This disclosure can be suitably used in the field of working media used in refrigeration cycles, and can also be broadly and suitably used in the field of refrigeration cycle systems such as air conditioners, refrigerators (household and commercial), dehumidifiers, display cases, ice makers, heat pump water heaters, heat pump washer-dryers, vending machines, etc. [Explanation of Symbols]

[0121] 10: Air conditioning system (refrigeration cycle system) 11: Indoor unit 12:Outdoor unit 13: Piping 14: Heat exchanger 15: Heat exchanger 16: Compressor 17: Pressure reducing device 18: Four-way valve 20: Refrigerator (freezing cycle system) 21: Compressor 22: Condenser 23: Decompression device 24: Evaporator 25: Piping

Claims

1. The refrigerant component contains a fluoroolefin that undergoes a disproportionation reaction, The disproportionation inhibitor for suppressing the disproportionation reaction of the fluoroolefin is characterized by containing fluoropropane having five or more hydrogen atoms and carbon dioxide (R744). Working fluid for refrigeration cycles.

2. The fluoroolefin is at least one of 1,1,2-trifluoroethylene (HFO-1123), tetrafluoroethylene (FO-1114), trans-1,2-difluoroethylene (HFO-1132E), or cis-1,2-difluoroethylene (HFO-1132Z). The working medium for a refrigeration cycle according to claim 1.

3. The fluoropropane is at least one of monofluoropropane, difluoropropane, and trifluoropropane. The working medium for a refrigeration cycle according to claim 1.

4. When the fluoroolefin is used as the main refrigerant component, the refrigerant component further contains at least one secondary refrigerant component selected from the group consisting of fluoromethane, fluoroethane, fluoropropane with four or fewer hydrogen atoms, fluoropropene, fluoroalkane or fluoroalkene having halogen substituents other than a fluoro group, alkane or alkene having four or fewer carbon atoms, and ammonia. The working medium for a refrigeration cycle according to claim 1.

5. When the total amount of the refrigerant component and the disproportionation inhibitor is set to 100% by mass, the content of fluoropropane is 30% by mass or less. The working medium for a refrigeration cycle according to claim 1 or 4.

6. When the total amount of the refrigerant component and the disproportionation inhibitor is set to 100% by mass, the carbon dioxide content is 20% by mass or less. The working medium for a refrigeration cycle according to claim 1 or 4.

7. When the total amount of the refrigerant component and the disproportionation inhibitor is set to 100% by mass, the content of the auxiliary refrigerant component is 30% by mass or less. The working medium for a refrigeration cycle according to claim 4.

8. A refrigeration cycle system configured using the working fluid for a refrigeration cycle described in any one of claims 1 to 4.

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