JP2005283098A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating device for circulating refrigerant, to which an odorant having compatibility with the refrigerant and refrigerating machine oil and not reacting with a material of a refrigeration circuit and the refrigerating machine oil is added, in the refrigeration circuit. <P>SOLUTION: This refrigerating device circulates the refrigerant, which is mainly composed of 1-4C hydrocarbon or combustible fluorinated hydrocarbon obtained by substituting part of hydrogen atoms of the hydrocarbon with fluorine atoms and which contains tetrahydrothiophene as the odorant, in the refrigeration circuit comprising a compressor, a radiator, an expanding mechanism and an evaporator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a refrigeration apparatus using a combustible refrigerant.

  In refrigerators, vending machines, and showcase refrigerators, chlorofluorocarbon refrigerants such as dichlorodifluoromethane (CFC-12) and hydrochlorofluorocarbon refrigerants such as chlorodifluoromethane (HCFC-22) are widely used as conventional refrigerants. It was. When these refrigerants are released into the atmosphere and reach the ozone layer over the earth, there is a problem of destroying the ozone layer. Therefore, chlorofluorocarbon-based fluorocarbons and hydrochlorofluorocarbons that have been used in refrigerators so far are used. Fluorocarbon fluorocarbons are being banned or regulated.

For this reason, hydrofluorocarbons such as CH ₂ FCF ₃ (HFC-134a) have come to be used as an alternative to the above refrigerant. However, even the HFC refrigerant has a problem that the influence on global warming, which is another problem of the global environmental problem, is almost the same as that of the conventional HCFC refrigerant HCFC-22 (CHClF ₂ ).

  In order to avoid these problems, recently, the use of a hydrocarbon refrigerant (HC), such as propane or isobutane, has been put to practical use as the refrigerant of the refrigeration apparatus. However, since HC refrigerant is flammable, there is a risk of fire or explosion when it leaks from the refrigeration circuit. Especially in the case of household refrigerators, since there are often various heat sources nearby, leakage of flammable refrigerant can lead to serious accidents.

  In view of this problem, it has been proposed to detect leakage of refrigerant gas by adding an odorant to the refrigerant in a refrigeration apparatus using a combustible gas refrigerant. For example, Patent Document 1 shows that methyl mercaptan is added to an HC refrigerant as an odorant made of a sulfur-containing organic substance. However, methyl mercaptan has a reactivity with copper, which is a material used in a refrigeration circuit. The copper surface is greatly transformed (corroded) to shorten its life. In addition, methyl mercaptan is highly reactive with refrigerating machine oil and produces a reaction product insoluble in refrigerant or refrigerating machine oil, and there is a risk that the insoluble reaction product may clog the capillary tube of the refrigerating circuit when operated for a long period of time.

  Patent Document 2 discloses that dimethyl sulfide is added as an odorant to the combustible HFC refrigerant in addition to mercaptan (methyl mercaptan, ethyl mercaptan). However, dimethyl sulfide does not have a particularly unusual odor (onion-like odor), and since this alone is not sufficient as an odorant for a flammable refrigerant, other odorants such as mercaptans are used. Usually used in combination with

  As described above, a flammable refrigerant to which an odorant is added, and a refrigerant containing an odorant that does not react with copper or refrigeration oil, which are materials for a refrigeration circuit, has not been obtained yet.

  Odorants generally require properties such as giving off unusual odors, being chemically stable, non-toxic and harmless to humans, and odorants are added. Various characteristics are required depending on the object. Therefore, even if it is known as an odorant, it is generally difficult to divert it immediately to other uses.

For example, the addition of tetrahydrothiophene (THT) as an odorant to a combustion gas such as city gas has already been put into practical use ("fragrance" No. 146 June 1985). In addition to the characteristics required for odorants, the odorant added to the combustion gas is safe and odorless and non-hazardous after combustion. Specific characteristics are required for the combustion gas, such as being not adsorbed by the gas. Addition of the THT to the combustion gas and the addition of the refrigerant to the refrigerant used in the refrigeration circuit are different dimensions, and no attention has been paid to using THT as the refrigerant.
JP-A-8-14675 JP-A-8-245952

  The present invention has been made in view of the above-mentioned problems, and the object thereof is a refrigerant to which an odorant that has compatibility with a refrigerant and refrigeration oil and does not react with the material of the refrigeration circuit and the refrigeration oil is added. And providing a refrigeration apparatus in which the refrigerant circulates in a refrigeration circuit.

  The above object of the present invention is solved by providing the following refrigeration apparatus.

In a refrigeration circuit including a compressor, a radiator, an expansion mechanism, and an evaporator, a hydrocarbon having 1 to 4 carbon atoms and a purity of 99.0% by volume or more, a viscosity at 40 ° C. of 5 to 300 cSt, and a volume resistivity A refrigeration oil of 10 ¹⁰ Ω · cm or more, 10 wt ppm to 0.5 wt% of tetrahydrothiophene, and 0.1 to 0.5 wt% of an antioxidant with respect to the refrigeration oil. .

  As described above, since the refrigerant of the present invention contains tetrahydrothiophene as an odorant, it is possible to easily detect that the refrigerant leaks from the refrigeration apparatus due to the odor, and the refrigerant and refrigerating machine oil The compatibility with is good. In particular, it does not corrode the surface by reacting with copper, which is the material of the refrigeration circuit, and it does not react with refrigeration oil, so there is no danger of clogging the refrigeration circuit without generating insoluble reaction products even after long-term operation. There is no.

  The refrigerant of the present invention contains, as a main component, a hydrocarbon having 1 to 4 carbon atoms or a combustible fluorinated hydrocarbon in which some of hydrogen atoms of the hydrocarbon are substituted with fluorine atoms. These are so-called combustible refrigerants. Examples of the hydrocarbon having 1 to 4 carbon atoms include propane, isobutane and the like, and examples of the flammable fluorinated hydrocarbon include those in which a part of the hydrocarbon having 1 to 3 carbon atoms is substituted with a fluorine atom. Difluoromethane, difluoroethane (1,1- or 1,2-difluoroethane), trifluoroethane (1,1,1- or 1,1,2-trifluoroethane), tetrafluoroethane (1,1, 1,2- or 1,1,2,2-tetrafluoroethane), pentafluoroethane, pentafluoropropane (1,1,2,2,3- or 1,1,1,3,3-pentafluoropropane Etc.), hexafluoropropane (1,1,2,2,3,3- or 1,1,1,2,3,3-hexafluoropropane, etc.), heptafluoropropane (1,1,1,2, etc.) 2,3,3- or 1,1,1,2,3,3,3-heptafluoropropane, etc.).

  The hydrocarbon preferably has a purity of 99.0% by volume or more, an unsaturated hydrocarbon content of 0.01% by weight or less, and a sulfur content of 0.1% by weight or less. If the purity of the hydrocarbon or combustible fluorinated hydrocarbon is lower than 99.0% by volume, impurities may be affected. Further, if the unsaturated hydrocarbon content exceeds 0.01% by weight, the unsaturated hydrocarbon content tends to react with refrigerating machine oil and materials in the refrigeration circuit and cause deterioration. Furthermore, if the total sulfur content exceeds 0.1 ppm by weight, the reaction with copper as the piping exceeds the allowable amount, which is not preferable.

  Next, the odorant used in the present invention will be described. Odorants for refrigerants are generally necessary for odorants, such as giving off unusual odors, being stable, non-toxic and harmless to humans. It is necessary not to react with circuit materials, particularly copper, to be compatible with the refrigerant, to be compatible with the refrigeration oil mixed with the refrigerant and circulated in the refrigeration circuit, and not to react with the refrigeration oil. . In addition to these characteristics, it is necessary to have an appropriate boiling point and freezing point. If the boiling point is too high, it will not evaporate and will not function as an odorant. On the other hand, if the freezing point is too high, it will solidify in the refrigerant and cause clogging of the refrigeration circuit.

  The odorant used in the refrigerant of the present invention is tetrahydrothiophene (hereinafter sometimes referred to as “THT”). THT has a peculiar odor (coal gas odor), is a liquid substance at room temperature having a boiling point of 122 ° C. and a freezing point of −96 ° C. Therefore, it functions sufficiently as an odorant when the refrigerant leaks, and does not coagulate even when used with the refrigerant, so that problems such as clogging of the refrigeration circuit do not occur. Moreover, THT has good compatibility with the above-mentioned hydrocarbons or combustible fluorinated hydrocarbons, and also has good compatibility with the refrigerating machine oil described later. More importantly, THT does not react with refrigeration circuit materials, particularly copper or copper alloys, and therefore does not corrode the copper piping, heat exchangers, etc. of the refrigeration circuit. Further, since THT does not react with refrigerating machine oil, there is no danger of clogging the refrigeration circuit with insoluble reaction products even when operated for a long time.

  The content of the odorant in the refrigerant is suitably in the range of 10 ppm by weight to 0.5% by weight. If it is lower than 10 ppm by weight, it is difficult to detect when the refrigerant leaks, and if it exceeds 0.5% by weight, the odor becomes stronger than necessary, and when the refrigerant is filled in the refrigeration circuit or when the refrigerant is recovered. The above range is appropriate because of difficulty in handling.

  The present invention also relates to a refrigeration apparatus for circulating the refrigerant in a refrigeration circuit including a compressor, a radiator, an expansion mechanism, and an evaporator.

  FIG. 1 is a conceptual diagram illustrating an example of a refrigeration circuit in the refrigeration apparatus of the present invention. In FIG. 1, 100 is a compressor, 120 is a radiator, 140 is an expansion mechanism (capillary tube), 160 is a cooler, 180 is a four-way valve, and 200 is a drying device. An arrow indicates a direction in which the refrigerant flows, a solid line indicates a case where normal cooling is performed, and a broken line indicates a case where defrosting is performed. Although FIG. 1 shows an example in which the drying apparatus 200 is provided between the expansion mechanism 140 and the radiator 120, the drying apparatus 200 may be provided not only at this position but also at a low pressure position.

  For example, when the interior is cooled, the high-temperature and high-pressure refrigerant gas compressed by the compressor 100 passes through the four-way valve 180 and is cooled by the radiator 120 to become a low-temperature and high-pressure refrigerant liquid. This refrigerant liquid is decompressed by an expansion mechanism 140 (for example, a capillary tube, a temperature expansion valve, etc.), becomes a low-temperature and low-pressure liquid containing a slight amount of gas, reaches the cooler 160, and evaporates by obtaining heat from indoor air. Then, again through the four-way valve 180, the compressor 100 is reached and the interior is cooled. In the case of defrosting the cooler, the refrigerant flow is changed in the reverse direction by the four-way valve 180, and the refrigerant frost is melted using the refrigerant condenser. If the radiator is an outdoor heat exchanger and the cooler is an indoor heat exchanger, it can be applied to a cooling / heating type air conditioner.

  The refrigerating machine oil used in the compressor is a lubricating oil sealed in the compressor, and a mixture of the refrigerant and a small amount of the refrigerating machine oil is circulated throughout the system in the refrigerating circuit. Odorants also come into contact with refrigeration oil. Therefore, as described above, it is necessary that the odorant has compatibility with the refrigerating machine oil and does not react with the refrigerating machine oil.

  In addition, the low temperature characteristics of the refrigerating machine oil and the miscibility with the refrigerant are important factors for the performance of the cooling system. The mixture of refrigerant and refrigerating machine oil must be stable (eg, hydrolysis resistant) at the operating temperature in the refrigeration system, and has a detrimental effect on materials used in refrigeration circuits, including compressors (eg, (Corrosion, insulation degradation)

  A part of the refrigerating machine oil is mixed in the compressed refrigerant gas, circulates in the refrigerating circuit of the refrigerating machine together with the refrigerant, and flows into the evaporator through an expansion mechanism such as a capillary tube or an expansion valve. In the low temperature part of the refrigeration circuit, the refrigeration oil moved from the compressor tends to lose its fluidity and easily stay there. If the refrigerating machine oil does not return from the evaporator to the compressor, the oil level is lowered in the compressor, and galling or seizure occurs.

  Therefore, the viscosity of the refrigerating machine oil at 40 ° C. is preferably 5 to 300 cSt. If the viscosity is 300 cSt or more, the fluidity is not sufficient, and the fluidity tends to be lost particularly at low temperatures. On the other hand, if it is smaller than 5 cSt, the oil film strength is insufficient on the lubricating surface and the sealing effect on the compression mechanism tends to be insufficient.

Furthermore, the volume resistivity of the refrigerating machine oil in the refrigerating apparatus of the present invention is preferably 10 ¹⁰ Ω · cm or more.

  As the refrigerating machine oil used in the refrigerating apparatus of the present invention, general mineral oil-based oils, ether-based synthetic oils, ester-based synthetic oils, fluorine-based synthetic oils, and the like are used. As the mineral oil-based oil, paraffin oil, naphthenic oil or the like is used. Moreover, polyvinyl ether and polyalkylene glycol are used as the ether synthetic oil. Examples of the ester synthetic oil include polyol ester oil and carbonate ester.

  Polyesters from polyhydric alcohols and polycarboxylic acids are preferably used as the ester-based synthetic oil, and among them, polyhydric alcohols selected from pentaerythritol (PET), trimethylolpropane (TMP), and neopentyl glycol (NPG). A polyol ester oil synthesized from a fatty acid and a fatty acid is preferably used.

  When the refrigerant uses a hydrocarbon, mineral oil is preferably used as the refrigerating machine oil, and when the refrigerant is a combustible fluorinated hydrocarbon, an ether-based synthetic oil such as polyvinyl ether is preferably used. Moreover, as said refrigerating machine oil, you may mix 1 type, or 2 or more types of refrigerating machine oil.

  In the refrigerating machine oil, additives such as antifoaming agents, antioxidants, moisture and / or acid scavengers, extreme pressure additives or antiwear agents, metal deactivators, particularly copper deactivators, etc. It is preferable to prevent denaturation (decomposition, oxidation degradation, sludge generation, etc.) of the refrigerating machine oil and denaturation (corrosion) of the material of the refrigeration circuit. In addition to these, a heat resistance improver, a corrosion inhibitor, a rust inhibitor, and the like may be added as appropriate.

  The additive for the refrigerating machine oil not only exerts a specific effect on the refrigerating machine oil itself, but also exhibits an effect on the sliding portion of the compressor, the insulating material, and the pipe metal as a result. These additives can be used alone or in combination of two or more. In addition, since the mixture of the refrigerant and a small amount of refrigerating machine oil circulates in the refrigerating circuit as described above, refrigerating machine oil to which the additive is added should not have a harmful effect on the material used in the refrigerating circuit. Is also necessary.

  As the antifoaming agent, dimethylpolysiloxane oil, trifluoropropylmethyl silicone oil, phenylmethyl silicone oil and the like are preferably used.

  The addition amount of the antifoaming agent is preferably 1 to 50 ppm by weight with respect to the refrigerating machine oil. If the amount is less than 1 ppm by weight, the effect as an antifoaming agent is not sufficient, and even if added over 50 ppm by weight, the effect as an antifoaming agent does not increase, so the above range is preferable.

  By adding an antifoaming agent, when the refrigerant compressor and the air in the circuit are deaerated before the refrigerant is filled, the amount of bubbles generated from the refrigerating machine oil can be reduced and mixing of bubbles into the deaerator can be prevented. In addition, it is possible to prevent foaming when degassing the gas dissolved in the refrigerating machine oil.

Examples of the antioxidant include ditertiary butyl paracresol (DBPC), 2,6-di-t-butyl-4-methylphenol, 4,4′-meretin bis (2,6-di-butylphenol), 2, Hindered phenolic antioxidants such as 2'-thiobis (4-methyl-6-t-butylphenol), p, p'-dioctyldiphenylamine, 3,7-dioctylphenothiazine, phenyl-α-naphthylamine, di (alkylphenyl) Amine (alkyl group has 4 to 20 carbon atoms), phenyl-α-naphthylamine, alkyldiphenylamine (alkyl group has 4 to 20 carbon atoms), N-nitrosodiphenylamine, phenothiazine, N, N′-dinaphthyl-p-phenylenediamine, Acridine, N-methylphenothiazine, N-ethylpheno Azine, Jibirujiruamin, diphenylamine, phenolamine, 2,6-di -t- butyl--α- dimethylamino para amine antioxidants of cresol, and sulfur system such as alkyl disulfides may be used.
Of these, DBPC is particularly preferably used. The addition amount of the antioxidant is preferably 0.1 to 0.5% by weight with respect to the refrigerating machine oil. If the amount is less than 0.1% by weight, the effect as an antioxidant is not sufficient, and even if added over 0.5% by weight, the effect as an antioxidant cannot be obtained any more, so the above range is preferable.

  The residual oxygen in the refrigeration circuit is preferably 0.1% by volume or less with respect to the internal volume of the refrigeration circuit.

  It is preferable to add moisture and / or an acid scavenger to the refrigerating machine oil. Water and acidic substances cause corrosion of metals used in the compressor, and when ester oil is used as a refrigerating machine oil, it causes hydrolysis and liberates fatty acid components. This also causes corrosion and metal soap. There is a concern that it may cause a clogging phenomenon due to generation, and further cause hydrolysis of an ester insulating material.

 As the moisture and / or acid scavenger, an epoxy compound, a carbodiimide compound, or the like is used. Epoxy compounds can also scavenge radicals. Examples of the epoxy compound include glycidyl ester and glycidyl ether. For example, a phenyl glycidyl ether type epoxy compound and an epoxidized fatty acid monoester can be used. For example, phenyl glycidyl ether and alkyl phenyl glycidyl ether can be used, and the alkyl phenyl glycidyl ether has 1 to 3 alkyl groups having 1 to 13 carbon atoms. And an ester of an epoxidized fatty acid having 12 to 20 carbon atoms and an alcohol or phenol or alkylphenol having 1 to 8 carbon atoms. Particularly preferred are epoxy stearic acid butyl, hexyl, benzyl, cyclohexyl, methoxyethyl, octyl and phenyl.

  The amount of moisture and / or acid scavenger added is preferably 0.1 to 0.5% by weight based on the refrigerating machine oil. When the amount is less than 0.1% by weight, the effect as a scavenger is not sufficient, and when the amount exceeds 0.5% by weight, a polymer is easily formed, so the above range is preferable.

  The residual moisture is preferably 500 ppm by weight or less, and more preferably 200 ppm by weight or less based on the total of the refrigerant and the refrigerating machine oil. By using the moisture scavenger as described above, the equilibrium moisture in the refrigeration circuit represented by the following formula can be reduced to 200 ppm by weight or less in the initial operation state. If the water content exceeds 500 ppm by weight, it tends to freeze in the capillary tube, and the hydrolysis that occurs when a polyester-based oil is used as the refrigerating machine oil, as well as the generation of metal soap sludge. Can be suppressed.

Formula 1
[(Residual moisture in the refrigeration circuit) / (Filling oil amount + Filling refrigerant amount)] × 10 ⁶ weight PPM
As the extreme pressure additive, for example, a tertiary phosphate-based phosphorus compound such as thermally stable triphenyl phosphate (TPP) or tricresyl phosphate (TCP) is used. Of these, TCP is particularly preferably used.

  The addition amount of the extreme pressure additive is preferably 0.1 to 2% by weight with respect to the refrigerating machine oil. If it is less than 0.1% by weight, the effect as an extreme pressure agent is not sufficient. In addition, the above range is preferred because the effect is not increased even if it exceeds 2 wt%.

  As the metal deactivator, particularly copper deactivator, for example, benzotriazole (BTA), triazole, triazole derivative, thiadiazole, thiadiazole derivative, dithiocarbamate, alizanin, quinizarin, etc. are used, among which BTA is preferable. used.

  The addition amount of the metal deactivator is preferably 1 to 100 ppm by weight with respect to the refrigerating machine oil. If the amount is less than 1 ppm by weight, the effect as a metal deactivator is not sufficient, and even if added over 100 ppm by weight, no further effect can be obtained, so the above range is preferable.

  As the desiccant, synthetic zeolite and the like are preferably used, and among them, sodium A type synthetic zeolite and potassium A type synthetic zeolite are preferable. In addition, the particle diameter (effective diameter) of the zeolite is preferably in the range of 3 to 6 mm in order to effectively capture moisture in the refrigerant circuit.

  As a drying apparatus used in the refrigeration apparatus, a desiccant may be accommodated in a container and connected to a refrigerant circuit by piping.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
Example 1
Using the refrigeration circuit shown in FIG. 1, a refrigeration apparatus was assembled using the following materials.
Refrigerant: Isobutane (purity 99.7% by volume, unsaturated hydrocarbon 0.001% by weight,
Sulfur content 0.05 ppm by weight)
Odorant: Tetrahydrothiophene (0.1% by weight added to refrigerant)
Refrigerator oil: Paraffin mineral oil Viscosity (40 ° C.) ¹⁵ cSt, Volume resistivity 10 ¹⁵ Ω · cm,
Refrigerating machine oil additive (addition amount is weight ratio to refrigerating machine oil)
Antifoaming agent: Silicone antifoaming agent (10 ppm)
Antioxidant: DBPC (0.3%)
Moisture and / or acid scavenger: epoxy compound (0.25%)
Extreme pressure additive: TCP (1%)
Copper deactivator: BTA (5 ppm)
Desiccant: Synthetic zeolite (effective diameter 3mm)
The refrigerant had a peculiar smell (coal gas odor) and could be easily detected even when a small amount of refrigerant leaked. Further, after the refrigerator was operated for 2000 hours, the surface condition of the inner surface of the copper pipe of the refrigeration circuit and the inner surface of the capillary tube was inspected, and no surface corrosion was observed.

It is a conceptual diagram which shows an example of the freezing circuit in this invention.

Explanation of symbols

100 Compressor 120 Radiator 140 Expansion mechanism (capillary tube)
160 Cooler 200 Drying device

Claims (1)

In a refrigeration circuit including a compressor, a radiator, an expansion mechanism, and an evaporator, a hydrocarbon having 1 to 4 carbon atoms and a purity of 99.0% by volume or more, a viscosity at 40 ° C. of 5 to 300 cSt, and a volume resistivity A refrigeration oil of 10 ¹⁰ Ω · cm or more, 10 wt ppm to 0.5 wt% of tetrahydrothiophene, and 0.1 to 0.5 wt% of an antioxidant with respect to the refrigeration oil. Refrigeration equipment.