Refrigeration cycle equipment

Abstract

A refrigeration cycle device is provided that takes into consideration the reduction of a sulfur-based odorant depending on the operating conditions and enables refrigerant leakage to be detected by the sense of smell. The refrigeration cycle device according to the present disclosure includes a refrigerant circuit including a compressor, and a refrigerant is sealed inside the refrigerant circuit. The refrigerant includes hydrocarbons having 1 to 4 carbon atoms and a sulfur-based odorant. The compressor is filled with refrigeration oil. The initial concentration of the sulfur-based odorant in the refrigerant is [Odo]0 (ppm by mass), the outside air temperature in the installation environment is T (K), and the amount of refrigerant sealed is M ref (g), the amount of refrigerant oil filled is M oil (g), the molecular weight of the hydrocarbon is MW ref , the molecular weight of the sulfur-based odorant is MW odo The olfactory threshold of sulfur-based odorants is [Odo] min (ppm by volume), the lower explosive limit concentration of hydrocarbons is [Ref] LHL When the initial concentration of the sulfur-based odorant in the refrigerant is expressed as (volume %), the initial concentration of the sulfur-based odorant in the refrigerant satisfies the following mathematical formula 1, A given by mathematical formula 1 satisfies mathematical formula 2, D satisfies mathematical formula 3, F satisfies mathematical formula 4, C given by mathematical formula 3 satisfies mathematical formula 5, and E given by mathematical formula 4 satisfies mathematical formula 6.

Description

[Technical Field]

[0001] The present disclosure relates to a refrigeration cycle device. [Background technology]

[0002] Currently, refrigerants used in refrigeration cycle devices are regulated by, for example, the Fluorocarbons Emission Control Act (enforced in April 2015). Specifically, an upper limit is set on the global warming potential (GWP) value of the refrigerants used. For this reason, there is a need to use refrigerants with lower GWP.

[0003] In recent years, hydrocarbons with 1 to 4 carbon atoms, such as R-290 (propane), R-1270 (propylene), R-600 (butane), and R-600a (isobutane), have been considered as refrigerants with low GWP values. Hydrocarbons with 1 to 4 carbon atoms have even lower GWP values ​​than saturated fluorocarbon compounds (hydrofluorocarbons), which are refrigerants with relatively low GWP values.

[0004] However, hydrocarbons with one to four carbon atoms are more flammable than hydrofluorocarbons. For example, in the international standard ISO-817, which defines the safety grades of refrigerants, R-32 (difluoromethane), a type of hydrofluorocarbon, is registered as slightly flammable (Class 2L), while R-290, R-1270, R-600, and R-600a are registered as highly flammable (Class 3).

[0005] When a highly flammable refrigerant such as a hydrocarbon having 1 to 4 carbon atoms is used as the refrigerant for the refrigeration cycle device, it is preferable to take measures to make the refrigerant olfactory or visually recognizable.

[0006] As a measure to make it possible to detect refrigerant by olfaction, a method is known in which a sulfur-based odorant is mixed into the refrigerant and refrigerant leakage is detected by an unpleasant odor.When a highly polar refrigerating machine oil is used, the sulfur-based odorant dissolves in the refrigerating machine oil inside the compressor. For example, Patent Document 1 discloses a refrigeration cycle device that suppresses the dissolution of the sulfur-based odorant into the refrigerating machine oil and makes it possible to detect refrigerant leakage by olfaction. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2023 / 079738 Summary of the Invention [Problem to be solved by the invention]

[0008] In the above-described refrigeration cycle device, the concentration of the sulfur-based odorant in the refrigerant is adjusted taking into consideration dissolution in the refrigeration oil and dilution after leakage, thereby making it possible to recognize the refrigerant by olfactory sense.

[0009] However, the inventors discovered that the amount of sulfur-based odorant dissolved in the refrigeration oil changes depending on the operating conditions of the refrigeration cycle device. When the amount of sulfur-based odorant dissolved in the refrigeration oil increases, the amount of sulfur-based odorant circulating in the refrigerant circuit together with the refrigerant decreases, and even when the refrigerant is released from the refrigeration cycle device, it becomes difficult to detect the refrigerant by olfactory sense.

[0010] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a refrigeration cycle device that takes into account the reduction of sulfur-based odorants depending on operating conditions and makes it possible to detect refrigerant leakage through the sense of smell. [Means for solving the problem]

[0011] The refrigeration cycle device according to the present disclosure includes a refrigerant circuit including a compressor, and a refrigerant is sealed inside the refrigerant circuit. The refrigerant includes hydrocarbons having 1 to 4 carbon atoms and a sulfur-based odorant. The compressor is filled with refrigeration oil. The initial concentration of the sulfur-based odorant in the refrigerant is [Odo]0 (ppm by mass), the outside air temperature in the installation environment is T (K), and the amount of refrigerant sealed is M ref (g), the amount of refrigerant oil filled is M oil (g), the molecular weight of the hydrocarbon is MW ref , the molecular weight of the sulfur-based odorant is MW odo The olfactory threshold of sulfur-based odorants is [Odo] min (ppm by volume), the lower flammable limit of hydrocarbons is [Ref] LFL When the initial concentration of the sulfur-based odorant in the refrigerant is expressed as (volume %), the initial concentration of the sulfur-based odorant in the refrigerant satisfies the following mathematical formula 1, A given by mathematical formula 1 satisfies mathematical formula 2, D satisfies mathematical formula 3, F satisfies mathematical formula 4, C given by mathematical formula 3 satisfies mathematical formula 5, and E given by mathematical formula 4 satisfies mathematical formula 6.

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[0018] According to the present disclosure, it is possible to provide a refrigeration cycle device that takes into consideration the reduction of sulfur-based odorants depending on operating conditions and allows refrigerant leakage to be detected by the sense of smell. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic configuration diagram showing an example of a refrigeration cycle device according to a first embodiment. [Figure 2] 1 is a cross-sectional schematic view showing an example of a compressor of a refrigeration cycle device according to a first embodiment. [Figure 3] 1 is a graph showing the relationship between the outside air temperature and the concentration of tetrahydrothiophene in the recovered refrigerant gas. [Figure 4] 1 is a graph showing the relationship between the mass fraction of refrigerant relative to refrigerating machine oil and the concentration of tetrahydrothiophene in recovered refrigerant gas. [Figure 5] 1 is a graph showing the relationship between the concentration of THT in the enclosed refrigerant gas and the concentration of tetrahydrothiophene in the recovered refrigerant gas. [Figure 6] 16 is a graph showing a comparison of the predicted results using Equation 16 with the experimental results for the concentration of tetrahydrothiophene in the recovered refrigerant gas. [Figure 7] 1 is a graph showing the change over time in the concentration of tetrahydrothiophene in the recovered refrigerant gas. [Figure 8] 10 is a graph showing the relationship between the natural logarithm of τ0.3 mass ppm and the reciprocal of the average value of the discharge temperature. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for clarity and simplification of the drawings, and do not represent actual dimensional relationships. In the drawings, the same or corresponding parts are designated by the same reference numerals, and their descriptions will not be repeated.

[0021] Embodiment 1 First, a brief overview of the refrigeration cycle device of this embodiment will be described. Fig. 1 is a schematic diagram showing an example of a refrigeration cycle device according to embodiment 1. The outdoor unit 1 includes a compressor 3, a condenser 4, an outdoor blower 5, etc., and the compressor 3 and the condenser 4 are connected by piping. The indoor unit 2 includes an expansion valve 6, an evaporator 7, an indoor blower 8, etc., and the expansion valve 6 and the evaporator 7 are connected by piping.

[0022] The compressor 3 of the outdoor unit 1 and the evaporator 7 of the indoor unit 2 are connected by a gas pipe 10. The condenser 4 of the outdoor unit 1 and the expansion valve 6 of the indoor unit 2 are connected by a liquid pipe 9.

[0023] The refrigerant circuit 100 is formed by the above-described configuration of the refrigeration cycle device, and the refrigerant circulates within the refrigerant circuit 100 via the liquid pipe 9 and the gas pipe 10 .

[0024] The compressor 3 compresses the gaseous refrigerant in the gas pipe 10. The condenser 4 cools the gaseous refrigerant compressed by the compressor 3 to form a high-pressure liquid refrigerant or a two-phase gas-liquid refrigerant. The expansion valve 6 reduces the pressure of the high-pressure liquid refrigerant or the two-phase gas-liquid refrigerant. The evaporator 7 heats the reduced-pressure refrigerant to form a low-pressure gaseous refrigerant. The compressor 3 draws in the refrigerant that has been reduced to a low-pressure gaseous state by the evaporator 7 and compresses it again.

[0025] The outdoor fan 5 is a component that sends air to the condenser 4, and is provided to promote heat exchange between the refrigerant flowing through the condenser 4 and the air, thereby absorbing or releasing heat. The indoor fan 8 is a component that sends air to the evaporator 7, and is provided to promote heat exchange between the refrigerant flowing through the evaporator 7 and the air, thereby absorbing or releasing heat.

[0026] In this embodiment, a configuration for performing heat exchange between the condenser 4 and the evaporator 7 and air is described, but this is not limited to this, and for example, the configuration may be such that heat exchange is performed with a liquid such as water instead of air.

[0027] Furthermore, in this embodiment, a configuration in which the evaporator 7 is provided inside the indoor unit 2 is described, but this is not limited to this, and for example, the condenser 4 may be arranged indoors and the evaporator 7 may be arranged outdoors.

[0028] The outdoor unit 1 as described above may be provided with, for example, a four-way valve or a combination of multiple valves, and a switching mechanism for switching between the suction pipe and the discharge pipe of the compressor 3. By providing a switching mechanism, the heat exchanger in the outdoor unit 1 functions as the evaporator 7, and the heat exchanger in the indoor unit 2 functions as the condenser 4, making it possible to use heat from outside the room to heat the room.

[0029] The refrigeration cycle device may be, for example, a device capable of both cooling and heating, a device capable of only cooling, or a device capable of only heating. The use of the refrigeration cycle device according to the present embodiment is not limited to air conditioning, but may also be for freezing, refrigeration, hot water supply, etc.

[0030] In the present embodiment, a configuration in which the expansion valve 6 is provided in the indoor unit 2 has been described, but the present invention is not limited to this, and for example, the expansion valve 6 may be provided in the outdoor unit 1. Also, for example, the expansion valve 6 may be provided in both the outdoor unit 1 and the indoor unit 2. Furthermore, for example, a plurality of indoor units 2 may be provided in the refrigerant circuit 100, and a plurality of outdoor units 1 may be provided.

[0031] <Refrigerant> Next, the refrigerant sealed inside the refrigerant circuit in this embodiment will be described. The refrigerant contains a main component that functions as a refrigerant, and further contains a sulfur-based odorant for detecting refrigerant leakage.

[0032] Here, the "main component" refers to the components of the refrigerant excluding sulfur-based odorants and impurities (such as air, moisture, and by-products that may be mixed in during the synthesis and refinement of refrigerant compounds). The main component of the refrigerant may be a single refrigerant or a mixture of multiple refrigerants. The content of the main component in the refrigerant exceeds 50% by mass, preferably 90% by mass or more, and more preferably 95% by mass or more.

[0033] The main component that functions as a refrigerant is a hydrocarbon having 1 to 4 carbon atoms. Examples of hydrocarbons having 1 to 4 carbon atoms include R-290 (propane), R-1270 (propylene), R-600 (butane), and R-600a (isobutane). The hydrocarbon having 1 to 4 carbon atoms is preferably propane, propylene, or a mixture thereof, as these have operating pressures suitable for use in refrigeration cycle devices. From the viewpoint of oxidation stability, propane is more preferable. According to the IPCC Sixth Assessment Report, propane has an extremely low GWP value of 0.02 and high cooling performance, which can contribute to reducing the environmental impact during the manufacture and operation of refrigeration cycle devices.

[0034] The refrigerant may further contain a halogenated hydrocarbon. Examples of halogenated hydrocarbons include chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, hydrofluoroolefins, hydrochlorofluoroolefins, and fluoroiodocarbons. Halogenated hydrocarbons have lower flammability than hydrocarbons due to the substitution of hydrogen atoms with halogen atoms, and mixing them can reduce the flammability of the refrigerant. The halogenated hydrocarbon may be mixed with a hydrocarbon having 1 to 4 carbon atoms and charged into the refrigerant circuit, or a refrigerant circuit that is already charged with a halogenated hydrocarbon or has a small amount of halogenated hydrocarbon remaining therein may be charged with an additional hydrocarbon having 1 to 4 carbon atoms.

[0035] The halogenated hydrocarbon preferably has an operating pressure similar to that of hydrocarbons having 1 to 4 carbon atoms. This increases the azeotropic property with the hydrocarbons having 1 to 4 carbon atoms, which are the main components of the refrigerant, and enables high cooling performance to be obtained. Such halogenated hydrocarbons are halogenated hydrocarbons having 1 to 4 carbon atoms, and more preferably halogenated hydrocarbons having 1 to 3 carbon atoms. This is because the halogenated hydrocarbons have larger molecules than hydrocarbons, resulting in a lower operating pressure compared to hydrocarbons with the same carbon number. Examples of halogenated hydrocarbons having 1 to 3 carbon atoms include HFC-23, HFC-32, HFC-41, HFC-125, HFC-134, HFC-134a, HFC-143, HFC-143a, HFC-152, HFC-152a, HFC-161, HFO-1141, HFO-1132a, HFO-1132(E), HFO-1132(Z), HFO-1123, and HFO- Examples of suitable hydrocarbons include HFO-1225ye(Z), HFO-1225ye(E), HFO-1225zc, HFO-1234yf, HFO-1234ze(E), HFO-1234ze(Z), HFO-1234ye(Z), HFO-1234ye(E), HFO-1243zf, HFO-1252zf, HFO-1261yf, FIC-13I1(CF3I), HCFC-22, and CFC-12.

[0036] The refrigerant may also contain carbon dioxide (R-744). Carbon dioxide has a low GWP of 1, which can contribute to reducing the environmental impact during the manufacture of refrigeration cycle devices. In addition, carbon dioxide is non-flammable, so mixing it can reduce the flammability of the refrigerant.

[0037] If air is contained in the refrigerant, it may accelerate deterioration of the refrigerant, sulfur-based odorants, refrigerating machine oil (described later), materials inside the compressor 3, etc., so it is preferable to remove the air from inside the refrigerant circuit before filling the refrigerant circuit with the refrigerant.

[0038] (Sulfur-based odorant) The sulfur-based odorant blended into the refrigerant is an odorant containing elemental sulfur. Examples of sulfur-based odorants include mercaptans, sulfides, and thiophenes. Examples of mercaptans include methyl mercaptan (MM), ethyl mercaptan (EM), normal propyl mercaptan (NPM), isopropyl mercaptan (IPM), and tertiary butyl mercaptan (TBM). Examples of sulfides include dimethyl sulfide (DMS), diethyl sulfide (DES), and methyl ethyl sulfide (MES). Examples of thiophenes include tetrahydrothiophene (THT). These sulfur-based odorants are compounds that have been used in fuel gases and have an unpleasant odor. These sulfur-based odorants may be used alone or in combination of two or more.

[0039] The sulfur-based odorant is preferably EM, NPM, IPM, TBM, DMS, MES, THT, or a mixture thereof, which are also used in fuel gas for home use. By mixing a sulfur-based odorant used in fuel gas for home use with the refrigerant, refrigerant leaks can be easily detected by the unpleasant odor that is unique to sulfur-based odorants.

[0040] The initial concentration of the sulfur-based odorant in the refrigerant is such that refrigerant leakage from the refrigerant circuit can be easily detected and the odor is not excessively unpleasant. Here, the initial concentration of the sulfur-based odorant in the refrigerant is a concentration calculated from the ratio of the mass of the sulfur-based odorant to the mass of the refrigerant charged in the refrigerant circuit. The sulfur-based odorant dissolves in the refrigerant oil (described later) inside the compressor 3. The amount of sulfur-based odorant dissolved in the refrigerant oil varies depending on the operating conditions of the refrigeration cycle device, such as the outside air temperature in the installation environment and the mass fraction of the refrigerant relative to the refrigerant oil. Therefore, the initial concentration of the sulfur-based odorant in the refrigerant is determined taking into account the reduction of the sulfur-based odorant depending on the operating conditions of the refrigeration cycle device. Details of the initial concentration of the sulfur-based odorant in the refrigerant will be described later.

[0041] Of the sulfur-based odorants, THT is more preferable. THT is chemically stable compared to mercaptans and sulfides, and is less likely to cause decomposition or corrosion reactions within the refrigerant circuit. Furthermore, its melting point is low at -96°C, making it less likely to solidify within the refrigerant circuit.

[0042] The sulfur-based odorant may be a compound that is not used as an odorant for fuel gas, as long as it contains sulfur element. For example, hydrogen sulfide, carbonyl sulfide, etc. have a distinctive unpleasant odor similar to the above-mentioned sulfur-based odorants, and can easily detect refrigerant leaks.

[0043] The refrigerant may further contain a sulfur-free odorant. This is because, like THT, sulfur-free odorants are less likely to cause metal corrosion reactions in the refrigerant circuit. Examples of sulfur-free odorants include cyclohexene, acrylic esters, ammonia, amines, pyrazines, and norbornenes. In addition to these sulfur-free odorants, the refrigerant may further contain a compound with a unique odor as an odorant.

[0044] <Compressor> In this embodiment, the refrigeration cycle device includes a compressor 3. A refrigerant passes through the inside of the compressor 3. The inside of the compressor 3 is filled with refrigeration oil. The refrigeration oil contains a base oil.

[0045] Fig. 2 is a cross-sectional schematic diagram showing an example of a compressor 3 of a refrigeration cycle apparatus according to this embodiment. As shown in Fig. 2, compressor 3 includes a shell 11. Shell 11 includes a compression mechanism 12 therein and an electric motor 13 that drives compression mechanism 12. In addition, shell 11 is connected to a suction pipe 14 for allowing refrigerant to flow into the interior and a discharge pipe 15 for allowing refrigerant to flow out to the exterior. Connected to the upstream side of suction pipe 14 is an accumulator 16 that separates gas and liquid in the refrigerant and sends the vapor to suction pipe 14.

[0046] The refrigerant that has passed through accumulator 16 flows into compression mechanism 12 in shell 11 through suction pipe 14. The refrigerant that has flowed into compression mechanism 12 is compressed to a high temperature and high pressure, and is then discharged from discharge pipe 15. In other words, compression mechanism 12 is configured to compress the refrigerant that has flowed into shell 11 from suction pipe 14 and discharge it from discharge pipe 15.

[0047] The compression mechanism 12 is a rotary type compression mechanism made up of a combination of a rolling piston 17, a vane (not shown), etc. The eccentric rotation of the rolling piston 17 changes the volume of the space surrounded by the inner circumferential surface of the cylinder chamber 19 of the cylinder 18, the outer circumferential surface of the rolling piston 17, and the vane (not shown), thereby compressing the refrigerant.

[0048] The compressed refrigerant is discharged from discharge hole 21 of upper bearing 20 into muffler space 22, and then from discharge hole 24 of discharge muffler 23 into shell 11. The discharged refrigerant passes through gaps in motor 13 (gaps between motor rotor 25 and motor stator 26, grooves provided on the outer peripheral surface of motor stator 26, etc.), and then is discharged from discharge pipe 15 to the downstream side of refrigerant circuit 100.

[0049] The compressor 3 has sliding parts inside the compression mechanism 12. To lubricate the sliding parts, refrigeration oil is stored in an oil reservoir 27 located below the compressor 3. The refrigeration oil stored in the oil reservoir 27 is supplied to the sliding parts inside the compression mechanism 12 by pump action through an oil supply hole (not shown) provided in the shaft of the drive shaft 28. The refrigeration oil comes into contact with the refrigerant inside the compressor 3, and therefore part of the refrigerant dissolves in the refrigeration oil.

[0050] <Refrigerating machine oil> Next, in this embodiment, the refrigeration oil filled to lubricate the inside of the compressor 3 will be described. The refrigeration oil contains a base oil. The base oil is at least one oil selected from the group consisting of oxygen-containing oils and hydrocarbon oils. Examples of oxygen-containing oils include polyalkylene glycol (PAG), polyol ester (POE), polyvinyl ether (PVE), etc. Examples of hydrocarbon oils include polyalphaolefin (PAO), alkylbenzene (AB), alkylnaphthalene (AN), mineral oil, etc.

[0051] Here, the base oil is a component that lubricates the inside of the compressor 3 due to the kinematic viscosity of the material. The base oil is preferably a material that has a kinematic viscosity higher than that of the refrigerant, and the kinematic viscosity at 40°C is preferably 5 mm 2 / s or more 250mm 2 / s or less is more preferable. When the base oil has a kinematic viscosity higher than that of the refrigerant, the kinematic viscosity of the base oil is sufficient to lubricate the sliding parts of the compressor 3 and not significantly reduce the cooling efficiency of the refrigeration cycle device. The kinematic viscosity of the base oil can be adjusted to fall within the above range by changing the molecular structure or degree of polymerization of each base oil.

[0052] (oil additives) The refrigerating machine oil may also contain, as oil additives, an antioxidant, an acid scavenger, and an extreme pressure agent (antiwear agent).

[0053] Examples of antioxidants include phenolic antioxidants such as 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and 2,2'-methylenebis(4-methyl-6-tert-butylphenol), and amine antioxidants such as phenyl-α-naphthylamine and N,N'-di-phenyl-p-phenylenediamine. Antioxidants not only inhibit the deterioration of refrigerating machine oils, but also have the effect of inhibiting the oxidative deterioration of sulfur-based odorants.

[0054] The content of the antioxidant in the refrigerating machine oil is preferably 0.05% by mass to 2% by mass, and more preferably 0.2% by mass to 1% by mass. If the content of the antioxidant in the refrigerating machine oil is less than 0.05% by mass, the antioxidant may not be effective. If the content of the antioxidant in the refrigerating machine oil is more than 2% by mass, the kinematic viscosity of the refrigerating machine oil may decrease, or the antioxidant may deteriorate and block the refrigerant circuit as an impurity.

[0055] Examples of acid scavengers include epoxy compounds such as phenyl glycidyl ether, alkyl glycidyl ester, alkyl glycidyl ether, alkylene glycol glycidyl ether, cyclohexene oxide, α-olefin oxide, and epoxidized soybean oil. Preferred acid scavengers are alkyl glycidyl ester, alkyl glycidyl ether, and α-olefin oxide. Acid scavengers capture acids generated by deterioration of refrigerating machine oil and organic materials (insulating films, sealing materials, etc.) present in the refrigerant circuit, and thus have the effect of suppressing deterioration of sulfur-based odorants due to acids.

[0056] The content of the acid scavenger in the refrigerating machine oil is preferably 0.05% by mass to 10% by mass, and more preferably 0.1% by mass to 10% by mass. If the content of the acid scavenger in the refrigerating machine oil is less than 0.05% by mass, the acid scavenger may not be effective. If the content of the acid scavenger in the refrigerating machine oil is more than 10% by mass, the kinematic viscosity of the refrigerating machine oil may decrease, or the acid scavenger may deteriorate and block the refrigerant circuit as an impurity.

[0057] Examples of extreme pressure agents (antiwear agents) include phosphorus-based extreme pressure agents such as phosphate esters, thiophosphate esters, acid phosphate esters, phosphites, acid phosphites, and their amine salts. Phosphate esters, thiophosphate esters, or mixtures thereof are preferred as extreme pressure agents (antiwear agents). Specifically, tricresyl phosphate (O=P-(OC7H7)3), triphenyl phosphorothioate (S=P-(OC6H5)3), triphenyl phosphate (O=P-(OC6H5)3), derivatives thereof, or mixtures thereof are preferred. Extreme pressure agents reduce friction in the sliding parts of the compressor 3, thereby suppressing the deterioration of sulfur-based odorants due to frictional heat.

[0058] The content of the extreme pressure agent in the refrigerating machine oil is preferably 0.05% by mass or more and 5% by mass or less, and more preferably 0.1% by mass or more and 4% by mass or less. If the content of the extreme pressure agent in the refrigerating machine oil is less than 0.05% by mass, the effect of the extreme pressure agent may not be obtained. If the content of the extreme pressure agent in the refrigerating machine oil is more than 5% by mass, the extreme pressure agent may corrode metals, reduce the kinematic viscosity of the refrigerating machine oil, or deteriorate and act as impurities to clog the refrigerant circuit.

[0059] The refrigerating machine oil may also contain an oxygen scavenger. Examples of oxygen scavengers include sulfur-containing aromatic compounds such as 4,4'-thiobis(3-methyl-6-tert-butylphenol), diphenyl sulfide, dioctyldiphenyl sulfide, dialkyldiphenylene sulfide, benzothiophene, dibenzothiophene, phenothiazine, benzothiapyran, thiapyran, thianthrene, dibenzothiapyran, and diphenylene disulfide; aliphatic unsaturated compounds such as various olefins, dienes, and trienes; and cyclic terpenes having unsaturated bonds such as α-pinene, β-pinene, limonene, and phellandrene. Preferred oxygen scavengers include aliphatic unsaturated compounds and cyclic terpenes having unsaturated bonds. The oxygen scavenger not only inhibits oxidative degradation of the refrigerating machine oil but also inhibits oxidative degradation of sulfur-based odorants.

[0060] The content of the oxygen scavenger in the refrigerating machine oil is preferably 0.05% by mass or more and 5% by mass or less, and more preferably 0.1% by mass or more and 3% by mass or less. If the content of the oxygen scavenger in the refrigerating machine oil is less than 0.05% by mass, the effect of the oxygen scavenger may not be obtained. If the content of the oxygen scavenger in the refrigerating machine oil is more than 5% by mass, the kinematic viscosity of the refrigerating machine oil may decrease, or the oxygen scavenger may deteriorate and block the refrigerant circuit as an impurity.

[0061] (others) The refrigerating machine oil may contain a fluorescent agent, a coloring agent, etc., so that the refrigerant and the refrigerating machine oil can be visually detected. The fluorescent agent and the coloring agent are preferably added in an amount equal to or less than the saturated solubility of the refrigerating machine oil, so as to prevent precipitation at low temperatures.

[0062] If the refrigeration oil contains moisture, it may accelerate the deterioration of the refrigerant, the refrigeration oil, metals in the refrigerant circuit, organic materials (polyester, etc.) in the refrigerant circuit, etc., so the moisture content of the refrigeration oil to be filled must be controlled to 300 ppm by mass or less, preferably 100 ppm by mass or less.

[0063] <Initial concentration of sulfur-based odorant> As mentioned above, sulfur-based odorants dissolve in refrigeration oil. If the amount of sulfur-based odorants circulating in the refrigerant circuit along with the refrigerant decreases due to dissolution in the refrigeration oil, it becomes difficult to detect refrigerant leaks by olfactory sense.

[0064] Furthermore, the amount of sulfur-based odorant dissolved in refrigerating machine oil varies depending on the operating conditions of the refrigeration cycle device, for example, the outside air temperature in the installation environment and the mass fraction of the refrigerant relative to the refrigerating machine oil. Specifically, as will be shown in (Evaluation Test 1) below, the lower the outside air temperature in the installation environment, the greater the amount of sulfur-based odorant dissolved in refrigerating machine oil, making it more difficult to detect refrigerant leakage by olfaction. Furthermore, as will be shown in (Evaluation Test 2) below, the smaller the mass fraction of the refrigerant relative to the refrigerating machine oil, the greater the amount of sulfur-based odorant dissolved in refrigerating machine oil, making it more difficult to detect refrigerant leakage by olfaction. Therefore, the initial concentration of the sulfur-based odorant in the refrigerant is determined as described below, taking into consideration the amount of reduction of the sulfur-based odorant that changes depending on the operating conditions of the refrigeration cycle device.

[0065] The initial concentration of the sulfur-based odorant in the refrigerant satisfies the following formula 1. A given by formula 1 satisfies the following formula 2, D satisfies formula 3, and F satisfies formula 4, C given by formula 3 satisfies formula 5, and E given by formula 4 satisfies formula 6. Here, the initial concentration of the sulfur-based odorant in the refrigerant is [Odo]0 (ppm by mass), the outside air temperature in the installation environment is T (K), and the amount of refrigerant charged is M ref (g), the amount of refrigerant oil filled is M oil (g), the molecular weight of the hydrocarbon is MW ref , the molecular weight of the sulfur-based odorant is MW odo The olfactory threshold of sulfur-based odorants is [Odo] min (ppm by volume), the lower flammable limit of hydrocarbons is [Ref] LFL (volume %).

[0066] The value A in Equation 2 is derived from the evaluation tests 1, 2, and 3 described below, and is determined by the ambient temperature T in the installation environment, the mass fraction M of the refrigerant relative to the refrigerating machine oil, and ref / (M ref +M oil) is used to predict the concentration of the sulfur-based odorant that decreases depending on the refrigerant's flammability. C shown in Equation 5 is the minimum volume ppm concentration of the sulfur-based odorant required to recognize the refrigerant by olfactory sense when the refrigerant diffuses in the air and the concentration of the hydrocarbons contained in the refrigerant becomes 0.2 times the lower flammability limit. E shown in Equation 6 is the volume ppm concentration of the sulfur-based odorant when the refrigerant diffuses in the air and the concentration of the hydrocarbons contained in the refrigerant becomes 0.2 times the lower flammability limit, and the odor index of the refrigerant exceeds 18, which is the upper limit of "easily detectable odors." Equations 3 and 4 are used to convert the volume ppm concentrations C and E of the sulfur-based odorant shown in Equation 5 and Equation 6 into mass ppm concentrations D and F, respectively. The reason why an odorant is mixed in to enable the refrigerant to be detected by the sense of smell when the refrigerant diffuses in the air and the concentration of hydrocarbons contained in the refrigerant reaches 0.2 times the lower flammable limit is that standards for fuel gases such as ISO 13734 and NFPA 58 require that the mixing of an odorant be made possible so that the refrigerant can be detected by the sense of smell at 0.2 times the lower flammable limit.

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[0073] When the initial concentration [Odo]0 of the sulfur-based odorant in the refrigerant is within the range that satisfies the above formula 1, the amount of sulfur-based odorant circulating in the refrigerant circuit with the refrigerant is determined by the outside air temperature T and the mass fraction M of the refrigerant relative to the refrigeration oil. ref / (M ref +M oil Even when the odor concentration of the sulfur-based odorant in the refrigerant is reduced depending on the operating conditions of the refrigeration cycle device, including the condition of (1), the odor is still detectable by olfactory sense and is not excessively unpleasant. In other words, when the initial concentration [Odo]0 of the sulfur-based odorant in the refrigerant is within the range that satisfies the above mathematical formula 1, the reduction of the sulfur-based odorant due to dissolution into the refrigerating machine oil is taken into consideration depending on the operating conditions, and the refrigerant leakage can be detected by olfactory sense.

[0074] Furthermore, the sulfur-based odorant circulating through the refrigerant circuit together with the refrigerant decreases due to deterioration, making it difficult to detect refrigerant leakage by olfaction. Specifically, as will be shown in (Evaluation Test 4) described later, the higher the refrigerant discharge temperature during operation of the refrigeration cycle device and the longer the operation time of the refrigeration cycle device, the more the sulfur-based odorant circulating through the refrigerant circuit together with the refrigerant is thermally decomposed, making it difficult to detect refrigerant leakage by olfaction. Therefore, it is more preferable to determine the initial concentration of the sulfur-based odorant in the refrigerant as described below, taking into consideration the amount of reduction of the sulfur-based odorant, which changes depending on the operating conditions of the refrigeration cycle device, including the outside air temperature in the installation environment, the mass fraction of the refrigerant relative to the refrigeration oil, as well as the discharge temperature of the refrigerant and the operating time.

[0075] It is more preferable that the initial concentration of the sulfur-based odorant in the refrigerant satisfies the following formula 7. G given by formula 7 satisfies the following formula 8. Here, the average discharge temperature of the refrigerant is T d (K), the operating time of the refrigeration cycle device is t (hr).

[0076] Note that G in Equation 8 is derived from (Evaluation Test 4) described later, and is the average discharge temperature T dThe purpose of this is to predict the concentration of the sulfur-based odorant that decreases depending on the operating time t of the refrigeration cycle device.

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[0079] When the initial concentration [Odo]0 of the sulfur-based odorant in the refrigerant is within the range that satisfies the above formula 7, the amount of sulfur-based odorant circulating in the refrigerant circuit with the refrigerant is determined by the outside air temperature T and the mass fraction M of the refrigerant relative to the refrigeration oil. ref / (M ref +M oil ) plus the average refrigerant discharge temperature T d Even when the odor is reduced depending on the operating conditions of the refrigeration cycle device, including the operating time t of the refrigeration cycle device, the odor is still detectable by olfactory sense and is not excessively unpleasant. In other words, when the initial concentration [Odo]0 of the sulfur-based odorant in the refrigerant is within the range that satisfies the above formula 7, the reduction of the sulfur-based odorant due to dissolution into the refrigeration oil and deterioration is taken into consideration depending on the operating conditions, and the refrigerant leakage can be detected by olfactory sense.

[0080] Next, the initial concentration [Odo]0 of the sulfur-based odorant in the refrigerant when the refrigerant is propane and the sulfur-based odorant is THT will be explained. As described above, it is desirable to use propane as the refrigerant and THT as the sulfur-based odorant. When the refrigeration cycle device is used under the operating conditions shown in Table 1 with the refrigerant being propane and the sulfur-based odorant being THT, it is desirable that the initial concentration [Odo]0 of the sulfur-based odorant in the refrigerant satisfy the following mathematical formula 9. Equation 9 is an equation obtained by applying the operating conditions listed in Table 1 to Equation 7. The operating conditions listed in Table 1 are examples of operating conditions under which the sulfur-based odorant is likely to be reduced. Specifically, examples of operating conditions under which the amount of sulfur-based odorant dissolved in the refrigerating machine oil increases include a relatively low outside air temperature and a relatively small mass fraction of refrigerant to the refrigerating machine oil, and examples of conditions under which the amount of sulfur-based odorant reduced increases include a relatively high discharge temperature and a relatively long operating time.

[0081] [Table 1]

[0082]

number

[0083] When the refrigerant is propane, the sulfur-based odorant is THT, and the initial concentration [Odo]0 of the sulfur-based odorant (THT) in the refrigerant is within a range that satisfies the above-mentioned formula 9, it is possible to detect a refrigerant leak by olfactory sense when the refrigerant is diluted to 0.2 times the lower flammability limit concentration of propane, even under operating conditions where the sulfur-based odorant (THT) is likely to decrease. Furthermore, when the refrigerant is propane, the sulfur-based odorant is THT, and the initial concentration [Odo]0 of the sulfur-based odorant (THT) in the refrigerant is within a range that satisfies the above-mentioned formula 9, the refrigerant becomes an odor that is not excessively unpleasant when the refrigerant is diluted to 0.2 times the lower flammability limit concentration of propane.

[0084] Here, when THT dissolves in refrigerating machine oil, it reduces the viscosity of the refrigerating machine oil. Refrigerating machine oil is required to have a certain viscosity in order to lubricate sliding parts, so when the refrigerant is propane and the sulfur-based odorant is THT, it is more preferable that the initial concentration of the sulfur-based odorant (THT) in the refrigerant be 10,000 (ppm by mass) or less. In other words, when the refrigerant is propane and the sulfur-based odorant is THT, it is preferable that the initial concentration of the sulfur-based odorant (THT) in the refrigerant satisfy the following mathematical formula 12: When the refrigerant is propane and the sulfur-based odorant is THT, the initial concentration of the sulfur-based odorant (THT) in the refrigerant is preferably less than 10,000 (ppm by mass). In other words, when the refrigerant is propane and the sulfur-based odorant is THT, the initial concentration of the sulfur-based odorant (THT) in the refrigerant preferably satisfies the following formula 10.

number

[0085] When the refrigerant is propane, the sulfur-based odorant is THT, and the initial concentration [Odo]0 of the sulfur-based odorant (THT) in the refrigerant is within a range that satisfies the above formula 10, even under operating conditions in which the sulfur-based odorant (THT) is likely to decrease, when the refrigerant is diluted to 0.2 times the lower flammability limit concentration of propane, it is possible to detect a refrigerant leak by olfactory sense, and the reliability of the lubricating function of sliding parts, which is the role of refrigeration oil, can be ensured.

[0086] In the above formulas 1 and 7, the lower limit of the initial concentration [Odo]0 of the sulfur-based odorant in the refrigerant is set as the olfactory threshold [Odo] of the sulfur-based odorant. min The olfactory threshold of sulfur-based odorants [Odo] is determined based on the following: min is the minimum concentration that can be detected by the human sense of smell, and is a value determined for each chemical substance through olfactory measurements. There are two olfactory thresholds: the detection threshold, which is the minimum concentration at which you can detect an odor without knowing what it is, and the recognition threshold, which is the minimum concentration at which you can detect what the odor is. It is empirically known that the detection threshold is about 10 times the detection threshold. Based on this, in order to ensure that the average person can detect a refrigerant leak by smell, the lower limit of the initial concentration [Odo]0 of sulfur-based odorants is empirically set to the olfactory threshold [Odo]. min Therefore, in order to ensure that an ordinary person can detect a refrigerant leak by smell, the initial concentration [Odo]0 of the sulfur-based odorant in the refrigerant may be set to satisfy the following formula 11.

[0087]

number

[0088] Furthermore, in order to more reliably detect a refrigerant leak by olfaction, the lower limit of the initial concentration [Odo]0 of the sulfur-based odorant may be set to twice that of Formula 11. In other words, in order to more reliably detect a refrigerant leak by olfaction, the initial concentration [Odo]0 of the sulfur-based odorant may be set to satisfy the following Formula 12. This is because, according to the Weber-Fechner law, which states that the relationship between the concentration of an odorant and the intensity of the odor has a logarithmic correlation, doubling the concentration has the effect of moderately increasing the intensity of the odor to a degree that is less than double.

[0089]

number

[0090] In the above-described refrigeration cycle device, a rotary compressor is used as the compressor 3, but this is not limited to this. For example, a low-pressure shell type or high-pressure shell type scroll compressor or screw compressor may be used as the compressor 3. [Example]

[0091] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to these examples.

[0092] <Formula 1> First, in order to explain Equation 1, (Evaluation Test 1), (Evaluation Test 2), and (Evaluation Test 3) will be explained.

[0093] (Evaluation Test 1) In order to evaluate the effect of the outside air temperature T in the installation environment on the amount of sulfur-based odorant circulating in the refrigerant circuit together with the refrigerant, a refrigerant gas mixture of refrigerant, sulfur-based odorant, and refrigeration oil was prepared under the conditions shown in Table 2.

[0094] [Table 2]

[0095] The refrigerant gas was sealed in a test container and stirred by shaking. The container was then placed in a small environmental test chamber (SH-221, manufactured by Espec Corporation) and the temperature was adjusted. After the temperature of the test container was stabilized at the value shown in Table 3, a pressure gauge was connected to measure the internal pressure of the container. The refrigerant gas was then collected in a Tedlar bag (1-2711-05, manufactured by AS ONE Corporation). The concentration of THT in the collected refrigerant gas was analyzed using a gas chromatograph mass spectrometer (JMS-K9, manufactured by JEOL Ltd.).

[0096] Table 3 shows the temperature of the test vessel (outside air temperature T in the installation environment), vessel internal pressure P, and the THT concentration [Odo] in the recovered refrigerant gas, while Figure 3 shows the relationship between the outside air temperature T in the installation environment and the THT concentration [Odo] in the recovered refrigerant gas. The correlation between the outside air temperature T and the THT concentration [Odo] in the recovered refrigerant gas is thought to represent the vapor pressure of THT at a certain temperature and a certain refrigeration oil mixture ratio. Therefore, based on the Clausius-Clapeyron equation, which shows the relationship between temperature and vapor pressure, the relationship between the outside air temperature T and the THT concentration [Odo] in the recovered refrigerant gas was formulated as shown in Equation 13 below.

[0097] [Table 3]

[0098]

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[0099] As shown in Figure 3, the concentration of THT in the recovered refrigerant gas [Odo] decreased as the outside air temperature T decreased. This is thought to be because as the outside air temperature T decreased, the temperature of the refrigerant gas decreased, which reduced the vapor pressure of THT and increased the amount of THT dissolved in the refrigerating machine oil.

[0100] As described above, it was confirmed that the lower the outside air temperature T in the installation environment, the less THT circulating in the refrigerant circuit along with the propane, and that even when the refrigerant is released from the refrigeration cycle device, it becomes more difficult to detect by olfactory sense.

[0101] While the above evaluation evaluated the effect of the outside air temperature T on the amount of sulfur-based odorants dissolved in refrigerating machine oil when THT was used, it is believed that similar results would be obtained when using sulfur-based odorants other than THT. Sulfur-based odorants are polar due to the presence of sulfur atoms, and like THT, they dissolve easily in refrigerating machine oil, causing a drop in vapor pressure due to the influence of refrigerating machine oil. For this reason, it is believed that the lower the outside air temperature T, the lower the vapor pressure of the sulfur-based odorants, and the greater the amount of sulfur-based odorants dissolved in refrigerating machine oil. Furthermore, when refrigerating machine oils other than PAG are used, the amount of dissolution decreases because they are not as polar as PAG, but it is also believed that the lower the temperature, the less circulating the sulfur-based odorants become.

[0102] (Evaluation Test 2) Mass fraction M of refrigerant to refrigerating machine oil ref / (M ref +M oil In order to evaluate the effect of the sulfur-based odorant circulating in the refrigerant circuit together with the refrigerant, a refrigerant gas mixture containing a refrigerant, a sulfur-based odorant, and refrigeration oil was prepared under the conditions shown in Table 4.

[0103] [Table 4]

[0104] The refrigerant gas was sealed in a test container, stirred by shaking, and then allowed to stand at 25°C. After 24 hours of standing, the refrigerant gas was collected in a Tedlar bag (AS ONE Corporation, 1-2711-05). The THT concentration in the collected refrigerant gas was analyzed using a gas chromatograph mass spectrometer (JEOL Ltd., JMS-K9).

[0105] The temperature of the test container (outside air temperature T in the installation environment), the amount of refrigerant charged M ref, refrigerant oil filling amount M oil , the mass fraction of refrigerant to refrigerating machine oil M ref / (M ref +M oil ), and the concentration of THT in the recovered refrigerant gas [Odo] are shown in Table 5, and the mass fraction of the refrigerant relative to the refrigerant oil, M ref / (M ref +M oil The relationship between the concentration of THT in the recovered refrigerant gas [Odo] and the temperature [°C] is shown in Figure 4. As shown in Figure 4, the mass fraction M ref / (M ref +M oil A proportional relationship was obtained between the temperature (T) of the refrigerant oil and the concentration of THT in the recovered refrigerant gas [Odo], as shown in the following formula 14. This indicates that under the conditions of constant outside air temperature T and constant amount of charged THT, when the amount of charged refrigerant oil decreases, the amount of THT dissolved in the refrigerant oil and present in the liquid phase decreases, and the amount of THT in the gas phase increases.

[0106] [Table 5]

[0107]

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[0108] As described above, the mass fraction M of the refrigerant to the refrigerating machine oil ref / (M ref +M oil ) decreases, that is, the more refrigerant oil there is relative to the refrigerant, the less THT circulating in the refrigerant circuit along with the propane, and it was confirmed that the refrigerant becomes difficult to detect by olfactory sense even when released from the refrigeration cycle device.

[0109] (Evaluation Test 3) In order to evaluate the influence of the initial concentration of sulfur-based odorants in the refrigerant on the concentration of sulfur-based odorants circulating through the refrigerant circuit together with the refrigerant, a commercially available residential room air conditioner with a refrigerant circuit (manufactured by Mitsubishi Electric Corporation, indoor unit model number MSZ-RW35VG-E1 / outdoor unit model number MUZ-RW35VGHZ-E1) was used, and the refrigerant gas released from the refrigerant circuit was collected. The refrigerant gas to be sealed in the refrigerant circuit was prepared under the conditions shown in Table 6.

[0110] [Table 6]

[0111] The household room air conditioner was operated for one hour and then stopped. When the temperature of the discharge pipe 15 of the compressor 3 was 60°C, the refrigerant gas was released from between the evaporator 7 and the compressor 3 and collected in a Tedlar bag (1-2711-05, manufactured by AS ONE Corporation). The concentration of THT in the collected refrigerant gas was analyzed using a gas chromatograph mass spectrometer (JMS-K9, manufactured by JEOL Ltd.).

[0112] The concentration [Odo]0 of THT in the charged refrigerant gas and the concentration [Odo] of THT in the recovered refrigerant gas are shown in Table 7, and the relationship between the concentration [Odo]0 of THT in the charged refrigerant gas and the concentration [Odo] of THT in the recovered refrigerant gas is shown in Figure 5. The concentration [Odo]0 of THT in the charged refrigerant gas is, in other words, the initial concentration of the sulfur-based odorant in the refrigerant.

[0113] As shown in Figure 5, a proportional relationship was obtained between the THT concentration [Odo]0 in the charged refrigerant gas and the THT concentration [Odo] in the recovered refrigerant gas, as shown in the following formula 15. This is because there is a proportional relationship between the amount of THT charged and the vapor pressure of THT in the refrigerant circuit. Because the amount of THT is very small compared to the amount of refrigeration oil used as a solvent, Henry's law holds true, and the partial pressure of the sulfur-based odorant is proportional to the amount of sulfur-based odorant charged.

[0114] [Table 7]

[0115]

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[0116] As described above, it was confirmed that there is a proportional relationship between the initial concentration [Odo]0 of the sulfur-based odorant in the refrigerant and the concentration [Odo] of the sulfur-based odorant circulating in the refrigerant circuit, and that the concentration [Odo] of the sulfur-based odorant circulating in the refrigerant circuit increases as the initial concentration [Odo]0 of the sulfur-based odorant in the refrigerant increases.

[0117] (Derivation of Equation 1) Equation 1 is derived based on Equations 13, 14, and 15, which are derived from the above-described (Evaluation Test 1), (Evaluation Test 2), and (Evaluation Test 3).

[0118] Equation 13 shows the dependence of the concentration [Odo] of the sulfur-based odorant circulating in the refrigerant circuit on the outside air temperature T, and is based on the characteristic that the sulfur-based odorant does not evaporate from the refrigerating machine oil to the gas phase as the temperature drops. Therefore, the outside air temperature T is proportional to the mass fraction M of the refrigerant to the refrigerating machine oil. ref / (M ref +M oil ) and affects the concentration [Odo] of the sulfur-based odorant circulating in the refrigerant circuit, regardless of the amount of the sulfur-based odorant enclosed. That is, Equation 13 is established independently of Equation 14 and Equation 15. Equation 15 is an equation that shows the relationship between the initial concentration [Odo]0 of the sulfur-based odorant in the refrigerant and the concentration [Odo] of the sulfur-based odorant circulating in the refrigerant circuit, which is established by Henry's law. Therefore, the relationship between the initial concentration [Odo]0 of the sulfur-based odorant sealed inside the refrigerant circuit and the concentration [Odo] of the sulfur-based odorant circulating in the refrigerant circuit is determined by the outside air temperature T and the mass fraction M of the refrigerant relative to the refrigerating machine oil. ref / (M ref +M oil ) holds true as long as the amount of refrigerating machine oil filled is small relative to the amount of sulfur-based odorant enclosed. That is, Equation 14 holds true independently of Equation 15. From the above, Equation 13, Equation 14, and Equation 15 are each independently established, and by multiplying Equation 13, Equation 14, and Equation 15, the outside air temperature T and the mass fraction M of the refrigerant relative to the refrigerating machine oil can be calculated. ref / (M ref +M oil ) the concentration [Odo] of sulfur-based odorant circulating in the refrigerant circuit can be predicted.

[0119] Here, Equation 13 and Equation 15 are ref =10, (M ref +M oil ) = 20 and [Odo]0 = 640 (ppm by volume). Therefore, the concentration [Odo] of the sulfur-based odorant circulating in the refrigerant circuit can be predicted by the following Equation 16. For confirmation, Fig. 6 shows the comparison results between the [Odo] predicted using Equation 16 and the [Odo] measured by experiment. At this time, the experiment was carried out under the condition that [Odo]0 in Equation 16 was 640 ppm by mass. It was confirmed that the prediction using Equation 16 was able to reproduce the experimental results.

[0120]

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[0121] The concentration [Odo] of the sulfur-based odorant circulating through the refrigerant circuit is required to be equal to or greater than the minimum sulfur-based odorant concentration required for the refrigerant to be olfactory-detectable when the refrigerant diffuses in the air and the concentration of hydrocarbons contained in the refrigerant reaches 0.2 times the lower flammability limit, and to be within a range where the odor is not too strong. Here, let D be the mass ppm concentration of the sulfur-based odorant required for the refrigerant to be olfactory-detectable when the refrigerant diffuses in the air and the concentration of hydrocarbons contained in the refrigerant reaches 0.2 times the lower flammability limit, and F be the mass ppm concentration of the sulfur-based odorant at which the refrigerant's odor index exceeds 18, the upper limit of "easily detectable odors," when the refrigerant diffuses in the air and the concentration of hydrocarbons contained in the refrigerant reaches 0.2 times the lower flammability limit. The concentration [Odo] of the sulfur-based odorant circulating through the refrigerant circuit is required to satisfy the following formula 17:

[0122]

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[0123] Note that D and F shown in Equation 17 are expressed by Equation 3 and Equation 4, respectively. The odor index is a numerical representation of the level of odor using the human sense of smell, and is the value obtained by multiplying the common logarithm of the odor concentration of an odor component (the concentration of an odor component when diluted with air until the odor is no longer detectable by the human sense of smell) by 10. The odor index has a relationship with odor intensity in the 6-level odor intensity rating system, as shown in Table 8. [Table 8]

[0124] To recognize a refrigerant through olfaction, it is necessary to recognize the presence of a sulfur-based odorant contained in the refrigerant. That is, the odor intensity of the refrigerant is preferably 2 (a weak odor that can be identified), and more preferably 3 (an odor that can be easily detected). Furthermore, the odor must not be too strong. That is, the odor intensity of the refrigerant must be less than 5 (a strong odor), and it is desirable that the odor intensity of the refrigerant be within the range of 3 (an odor that can be easily detected). Therefore, in Equation 17, the upper limit is set to F, which is the mass ppm concentration of the sulfur-based odorant when the refrigerant diffuses in the air and the concentration of hydrocarbons contained in the refrigerant becomes 0.2 times the lower flammability limit, causing the refrigerant's odor index to exceed 18, the upper limit for an "easily detectable odor."

[0125] From Formula 16 and Formula 17, the initial concentration [Odo]0 of the sulfur-based odorant filled in the refrigerant circuit is expressed by the following Formula 18.

[0126]

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[0127] By modifying the above formula 18, formula 1 can be derived.

[0128] <Formula 7> Next, in order to explain Equation 7, (Evaluation Test 4) will be explained.

[0129] (Evaluation Test 4) To evaluate the amount of odorant reduction due to long-term operation of the refrigeration cycle device, a commercially available residential room air conditioner with a refrigerant circuit (manufactured by Mitsubishi Electric Corporation, indoor unit model number MSZ-RW35VG-E1 / outdoor unit model number MUZ-RW35VGHZ-E1) was used, and the refrigerant gas released from the refrigerant circuit was collected. Two types of refrigerant gas were prepared under the conditions shown in Table 9 to be filled into the refrigerant circuit.

[0130] [Table 9]

[0131] The household room air conditioner was operated for one hour and then stopped. When the temperature of the discharge pipe 15 of the compressor 3 was 60°C, the refrigerant gas was released from between the evaporator 7 and the compressor 3 and collected in a Tedlar bag (1-2711-05, manufactured by AS ONE Corporation). The concentration of THT in the collected refrigerant gas was analyzed using a gas chromatograph mass spectrometer (JMS-K9, manufactured by JEOL Ltd.).

[0132] Figure 7 shows the time change in the THT concentration [Odo] in the recovered refrigerant gas when the average discharge temperature is 102°C and when the average discharge temperature is 66°C. As shown in Figure 7, the higher the average discharge temperature Td and the longer the time that has passed, the more the THT concentration [Odo] in the recovered refrigerant gas decreases. This is because the longer the time exposed to high temperatures, the more easily THT deteriorates and decomposes.

[0133] The time change of [Odo] shown in Figure 7 was approximated by an exponential function, and based on the Arrhenius equation, the relationship between the average discharge temperature Td and the decreasing tendency of the THT concentration [Odo] in the recovered refrigerant gas was formulated as shown in the following Equation 17. Here, t in Equation 19 is the time until the THT concentration [Odo] reaches a certain value. Also, [Odo] shown in Equation 19 0hris A shown in Equation 1.

[0134]

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[0135] Here, we will explain how to derive Equation 19. As shown in Figure 7, the decreasing trend of [Odo] can be approximated by an exponential function, which shows that this reaction is a first-order reaction that depends on [Odo]. In the case of a first-order reaction, [Odo] is proportional to [Odo]. 0hr , reaction rate constant k, and time t, and is expressed as follows:

[0136]

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[0137] The reaction rate constant k is calculated from the Arrhenius equation by subtracting the frequency factor k a , the activation energy of the reaction E a , gas constant R, and temperature T, Equation 21 can be expressed as follows: Equation 21 can be transformed into Equation 22 by taking the natural logarithm of both sides.

[0138]

number

[0139]

number

[0140] When the time it takes for a chemical reaction to change from an initial value to a certain value is τ, the reaction rate constant k is proportional to 1 / τ, so Equation 22 can be expressed as Equation 23 below.

[0141]

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[0142] Here, for the two exponential functions shown in Figure 7, the time it takes for [Odo] to reach 0.3 ppm by mass is τ 0.3質量ppm From Equation 23, when the average discharge temperature is 102°C and 66°C, τ 0.3質量ppm are calculated as 15270hr and 122839hr, respectively. 0.3質量ppm The relationship between the natural logarithm of THT and the reciprocal of the average discharge temperature is shown in Figure 8. From the equation obtained by linear approximation, the decrease in THT is a / R=7369. a From / R and the exponential function in Figure 7, the frequency factor k a is calculated as 171702.

[0143] According to the above-derived formula 19, the average discharge temperature T d and the amount of sulfur-based odorant that decreases depending on the operating time t of the refrigeration cycle device. As described above, the initial concentration of the sulfur-based odorant expressed by Equation 19 is required to be equal to or greater than the minimum concentration of the sulfur-based odorant required to recognize the refrigerant by olfactory sense when the refrigerant diffuses in the air and the concentration of hydrocarbons contained in the refrigerant becomes 0.2 times the lower flammability limit concentration, and to be within a range where the odor is not too strong. Therefore, Equation 7 can be derived from Equation 17 and Equation 19.

[0144] Although the present disclosure has been described above based on the embodiments, the present disclosure is not limited to the embodiments. Furthermore, appropriate combinations, modifications, omissions, etc. of the embodiments are also included within the scope of the technical idea of ​​the present disclosure. [Explanation of symbols]

[0145] 1 Outdoor unit 2 Indoor unit 3. Compressor 4. Condenser 5 Outdoor blower 6 Expansion valve 7. Evaporator 8 Indoor fan 9 Liquid pipe 10 Gas Pipes 11 Shell 12 Compression mechanism 13 Electric motor 14 Suction pipe 15 Discharge pipe 16 Accumulator 17 Rolling Piston 18 cylinders 19 Cylinder chamber 20 Upper bearing 21 Discharge hole 22 Muffler space 23 Discharge muffler 24 Discharge hole 25 Electric motor rotor 26 Electric motor stator 27 Oil sump 28 Drive shaft 100 Refrigerant circuit

Claims

1. a refrigerant circuit including a compressor; A refrigerant is sealed inside the refrigerant circuit, The refrigerant contains a hydrocarbon having 1 to 4 carbon atoms and a sulfur-based odorant, The compressor is filled with refrigerating machine oil, The initial concentration of the sulfur-based odorant in the refrigerant is [Odo] ０ (mass ppm), The outside air temperature in the installation environment is T (K), The amount of the refrigerant charged is M ｒｅｆ (g), The amount of refrigerating machine oil filled is M ｏｉｌ (g), The molecular weight of the hydrocarbon is MW ｒｅｆ , The molecular weight of the sulfur-based odorant is MW ｏｄｏ , The olfactory threshold of the sulfur-based odorant is [Odo] ｍｉｎ (ppm by volume), The lower flammable limit concentration of the hydrocarbon is [Ref] ＬＦＬ (volume%), A refrigeration cycle device in which an initial concentration of the sulfur-based odorant in the refrigerant satisfies the following mathematical formula 1, A given by mathematical formula 1 satisfies mathematical formula 2, D satisfies mathematical formula 3, F satisfies mathematical formula 4, C given by mathematical formula 3 satisfies mathematical formula 5, and E given by mathematical formula 4 satisfies mathematical formula 6. [Equation 1] [Equation 2] [Equation 3] [Equation 4] [Equation 5] [Equation 6]

2. The average discharge temperature of the refrigerating machine oil is T ｄ (K), When the operation time is t (hr), The initial concentration of the sulfur-based odorant in the refrigerant satisfies the following formula 7, and G given by formula 7 satisfies formula 8: The refrigeration cycle device according to claim 1. [Equation 7] [Equation 8]

3. the hydrocarbon is propane; The sulfur-based odorant is tetrahydrothiophene, The refrigerating machine oil is a polyalkylene glycol, The initial concentration of the sulfur-based odorant in the refrigerant satisfies the following Equation 9: The refrigeration cycle device according to claim 2. [Equation 9]

4. the hydrocarbon is propane; The sulfur-based odorant is tetrahydrothiophene, The refrigerating machine oil is a polyalkylene glycol, The initial concentration of the sulfur-based odorant in the refrigerant satisfies the following formula 10: The refrigeration cycle device according to claim 3. [Equation 10]

5. The initial concentration of the sulfur-based odorant in the refrigerant satisfies the following formula 11: The refrigeration cycle device according to claim 2. [0011]

6. The initial concentration of the sulfur-based odorant in the refrigerant satisfies the following formula 12: The refrigeration cycle device according to claim 2. [0012]

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