Working fluids, refrigerators, and refrigerator oils

Abstract

A working fluid containing a refrigerant and a refrigeration oil, the working fluid being filled into a refrigerant circulating system having a compressor, a condenser, an expansion mechanism, an evaporator, and a reservoir, the refrigerant comprising a hydrocarbon refrigerant having a carbon number of 2 to 4, the refrigeration oil having a mixed amine point of 20°C or higher and 50°C or lower, the refrigeration oil having a viscosity index of 110 or higher, the refrigerant solubility in the working fluid being 40% by mass or less under conditions of a temperature of 80°C and an absolute pressure of 2.8 MPa, and the refrigeration oil having a kinematic viscosity at -10°C of 200 mm 2 / s or higher and 3000 mm 2 / s or lower.

Description

TECHNICAL FIELD

[0001] The present application relates to a working fluid, a refrigerator, and a refrigerator oil. BACKGROUND

[0002] A refrigerator is provided with a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, an evaporator, and a liquid accumulator. In the refrigerant circulation system, a cycle including compression and temperature increase of the vaporized refrigerant in the compressor, liquefaction of the refrigerant due to heat radiation condensation in the condenser, decompression expansion in the expansion mechanism, and vaporization of the refrigerant in the evaporator is repeated using the phenomenon that heat is taken from the surroundings when a liquid is vaporized. In addition, the liquid accumulator is a device that temporarily accumulates liquid refrigerant returned from the evaporator of the system to the compressor, and prevents or mitigates suction of the liquid refrigerant into the compressor. In order to prevent, mitigate, or the like, rapid dilution of the refrigerator oil in the compressor, shortage of the refrigerator oil supply due to reduction of the oil level, or damage to sliding parts or the like due to occurrence of liquid compression, the refrigerant circulation system is desired to be provided with the liquid accumulator.

[0003] As a refrigerant used in a refrigerator in recent years, research is being conducted on replacement of HFC refrigerants such as R134a, R410A, with HFC refrigerants having lower GWP, i.e., R32, and HFO refrigerants having lower GWP such as R1234yf, mixed refrigerants thereof, or natural refrigerants such as hydrocarbons, carbon dioxide, and the like.

[0004] Among these refrigerants, in the case of using a hydrocarbon refrigerant such as R290, R600a, use of a hydrocarbon-based refrigerator oil such as mineral oil, alkylbenzene, an ether-based refrigerator oil such as polyalkylene glycol, polyvinyl ether, and an ester-based refrigerator oil such as monoester, diester, polyol ester, and the like has been researched in the past. It is known that these refrigerator oils have good compatibility with the refrigerants such as R290, R600a, and the like, and that reduction in kinematic viscosity at the time of refrigerant dissolution (refrigerant dissolution viscosity) is significant, and thus, problems such as poor lubrication in the refrigerator, sticking, increase in the amount of wear, and the like can occur (for example, Patent Document 1). Such reduction in refrigerant dissolution viscosity is likely to occur under conditions of high temperature and high pressure (for example, high temperature of around 80°C and high pressure of around 2.8 MPa).

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: Japanese Patent Application Publication No. 2002-235664 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] An object of one aspect of the present application is to ensure refrigerant dissolution viscosity under high temperature and high pressure conditions.

[0010] Solution to problem

[0011] The present application relates to a refrigerant composition, a refrigeration machine, and a refrigeration machine oil. The refrigerant composition contains a refrigerant and a refrigeration machine oil, and is filled into a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, an evaporator, and a reservoir. The refrigerant contains a hydrocarbon refrigerant having a carbon number of 2 to 4. The refrigeration machine oil has a mixed amine point of 20°C or higher and 50°C or lower, and a viscosity index of 110 or higher. The refrigerant solubility in the working fluid is 40% by mass or lower under the conditions of a temperature of 80°C and an absolute pressure of 2.8 MPa. The kinematic viscosity of the refrigeration machine oil at -10°C is 200 mm 2 / s or higher and 3000 mm 2 / s or lower.

[0012] The kinematic viscosity of the refrigeration machine oil at -20°C can be 10000 mm 2 / s or lower. The flash point of the refrigeration machine oil can be 250°C or higher. The refrigeration machine oil can contain a phosphorus-containing anti-wear agent. The refrigerant solubility in the working fluid can be 15% by mass or lower under the conditions of a temperature of 40°C and an absolute pressure of 0.7 MPa.

[0013] Another aspect of the present application relates to a refrigeration machine having a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, an evaporator, and a reservoir. The refrigerant circulation system is filled with a working fluid containing a refrigerant and a refrigeration machine oil. The refrigerant contains a hydrocarbon refrigerant having a carbon number of 2 to 4. The refrigeration machine oil has a mixed amine point of 20°C or higher and 50°C or lower, and a viscosity index of 110 or higher. The refrigerant solubility in the working fluid is 40% by mass or lower under the conditions of a temperature of 80°C and an absolute pressure of 2.8 MPa. The kinematic viscosity of the refrigeration machine oil at -10°C is 200 mm 2 / s or higher and 3000 mm 2 / s or lower.

[0014] Another aspect of the present application relates to a refrigeration machine oil that is filled together with a refrigerant into a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, an evaporator, and a reservoir. The refrigerant contains a hydrocarbon refrigerant having a carbon number of 2 to 4. The refrigeration machine oil has a mixed amine point of 20°C or higher and 50°C or lower, and a viscosity index of 110 or higher. The refrigerant solubility in a working fluid containing the refrigerant and the refrigeration machine oil is 40% by mass or lower under the conditions of a temperature of 80°C and an absolute pressure of 2.8 MPa. The kinematic viscosity of the refrigeration machine oil at -10°C is 200 mm 2 / s or higher and 3000 mm 2 / s or lower.

[0015] Among the above aspects, by using a refrigerant oil having a specific mixed aniline point (20°C or higher and 50°C or lower) and a viscosity index (110 or higher) in the presence of a hydrocarbon refrigerant, refrigerant solubility viscosity under high-temperature high-pressure conditions can be ensured compared to a case where a refrigerant oil not having such a specific mixed aniline point and a viscosity index is used. Note that the refrigerant solubility amount under conditions of a temperature of 80°C and an absolute pressure of 2.8 MPa and the kinematic viscosity of the refrigerant oil at -10°C are not necessarily constitutions for ensuring refrigerant solubility viscosity under high-temperature high-pressure conditions, but according to these constitutions, more suitable properties can be exhibited in terms of lubricity, low-temperature fluidity, oil returnability, and the like.

[0016] Effects of the Invention

[0017] According to one aspect of the present application, refrigerant solubility viscosity under high-temperature high-pressure conditions can be ensured. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A schematic view showing one embodiment of a refrigerator. DETAILED DESCRIPTION

[0019] Embodiments of the present application will be described below in detail with appropriate reference to the accompanying drawings.

[0020] Figure 1 A schematic view showing one embodiment of a refrigerator. As shown in Figure 1 The refrigerator 10 has at least a refrigerant circulation system 6 in which a compressor (refrigerant compressor) 1, a condenser (gas cooler) 2, an expansion mechanism 3 (capillary, expansion valve, or the like), and an evaporator (heat exchanger) 4 are connected in series through a flow path 5. In order to suppress or prevent a case where liquid refrigerant directly flows into the compressor 1, the refrigerant circulation system 6 has a liquid accumulator 7 between the evaporator 4 and the compressor 1 (on the side of the compressor 1).

[0021] In the refrigerant circulation system 6, first, high-temperature (typically 70 to 120°C) refrigerant discharged from the compressor 1 into the flow path 5 becomes a high-density fluid (supercritical fluid or the like) in the condenser 2. Then, the refrigerant is liquefied by passing through a narrow flow path of the expansion mechanism 3, and further vaporized in the evaporator 4 to become low-temperature (typically -40 to 0°C). The cooling device of the refrigerator 10 utilizes the phenomenon that the refrigerant vaporized in the evaporator 4 takes heat from the surroundings.

[0022] In the compressor 1, a small amount of refrigerant coexists with a large amount of refrigerant oil under high-temperature (typically 70 to 120°C) conditions. The refrigerant discharged from the compressor 1 into the flow path 5 is in a gaseous state, and contains a small amount (typically 1 to 10% by volume) of refrigerant oil in the form of mist, but a small amount of refrigerant is dissolved in the refrigerant oil in the form of mist Figure 1Point a in the middle).

[0023] Inside condenser 2, the gaseous refrigerant is compressed into a high-density fluid. Under relatively high temperature conditions (typically 40–80°C), a large amount of refrigerant coexists with a small amount of refrigeration oil. Figure 1 Point b in the text). In addition, a mixture of a large amount of refrigerant and a small amount of refrigeration oil is sequentially fed into the expansion unit 3 and the evaporator 4, rapidly reducing the temperature to a low level (typically -40 to 0°C). Figure 1 Points c and d in the diagram return to compressor 1.

[0024] When the compressor 1 is under high pressure, there is a possibility that liquid refrigerant may flow directly into the compressor 1. To suppress and prevent this, as described above, a liquid receiver 7 is provided between the evaporator 4 and the compressor 1 (on the side of the compressor 1). Sometimes, a large amount of liquid refrigerant may exist in the compressor 1 when it is stationary, and sometimes the viscosity of the refrigeration oil may decrease sharply during startup, resulting in insufficient lubrication. Even when the liquid refrigerant has dissolved, it is necessary to maintain an appropriate viscosity.

[0025] Examples of such refrigeration units 10 include cooling devices used in automotive air conditioners, dehumidifiers, refrigerators, cold storage warehouses, vending machines, display cases, chemical plants, residential air conditioning units, packaging air conditioning units, and heating pumps for hot water supply equipment.

[0026] The refrigerant circulation system 6 (refrigeration unit 10) is filled with a working fluid containing refrigerant and refrigeration oil. The refrigerant comprises a hydrocarbon refrigerant with 2 to 4 carbon atoms. Examples of hydrocarbon refrigerants with 2 to 4 carbon atoms include ethylene, ethane, propane (R290), propylene, cyclopropane, n-butane, isobutane (R600a), cyclobutane, and methylcyclopropane, or a mixture of two or more of these. Propane (R290) or isobutane (R600a) is preferred among the hydrocarbon refrigerants with 2 to 4 carbon atoms, and propane (R290) is more preferred.

[0027] The refrigerant may consist solely of hydrocarbon refrigerants with 2 to 4 carbon atoms, or it may contain other refrigerants in addition to hydrocarbon refrigerants with 2 to 4 carbon atoms. Examples of such other refrigerants include, for instance, saturated fluorinated hydrocarbon (HFC) refrigerants such as R32, R134a, R125, R143a, and R152a; unsaturated fluorinated hydrocarbon (HFO) refrigerants such as R1234yf and R1234ze; fluorinated ether refrigerants such as perfluoroether; bis(trifluoromethyl) sulfide refrigerants; methane trifluoride iodide refrigerants; and any one or a mixture of two or more of the following natural refrigerants: ammonia (R717) and carbon dioxide (R744).

[0028] The content of the hydrocarbon refrigerant having 2 to 4 carbon atoms can be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, based on the total amount of the refrigerant.

[0029] The refrigerant oil has a viscosity index of 110 or more, and from the viewpoint of further ensuring the refrigerant solubility viscosity under high-temperature and high-pressure conditions, can be 140 or more, 150 or more, 160 or more, or 170 or more, and is preferably 300 or less, and can be 250 or less or 220 or less. The viscosity index is the viscosity index measured in accordance with JIS K2283:2000.

[0030] The refrigerant oil has a mixed amine point of 20°C or more and 50°C or less, and from the viewpoint of further ensuring the refrigerant solubility viscosity under high-temperature and high-pressure conditions, can be 25°C or more or 30°C or more, and can be 45°C or less or 40°C or less. The mixed amine point refers to the mixed amine point specified in JIS K2256:2013 "Petroleum Products - Test Methods for Amine Point and Mixed Amine Point". The refrigerant oil having a mixed amine point within the above range exhibits intermediate properties to polyol ester-based refrigerant oils and hydrocarbon-based refrigerant oils that are typically used as refrigerant oils, and exhibits a unique property of suppressing the refrigerant solubility amount for a hydrocarbon refrigerant having 2 to 4 carbon atoms such as R290 and can maintain the refrigerant solubility viscosity under high-temperature and high-pressure conditions of 80°C and 2.8 MPa at a relatively high level, as compared to either of them. In addition, with respect to the two-layer separation temperature for a hydrocarbon refrigerant having 2 to 4 carbon atoms such as R290 (for example, the mass ratio of the refrigerant oil to the refrigerant in the working fluid (refrigerant oil / refrigerant) is 1 / 9 to 9 / 1), in the case of using a polyol ester-based refrigerant oil or a hydrocarbon-based refrigerant oil that is typically used as a refrigerant oil, there is a tendency for the two-layer separation temperature to be lower than -70°C and to be too miscible, whereas in the case of using a refrigerant oil having a mixed amine point within the above range, the two-layer separation temperature can be -70°C or more, -60°C or more, or -50°C or more.

[0031] The refrigerant oil has a specific kinematic viscosity at low temperatures. The kinematic viscosity of the refrigerant oil at -10°C is 200 mm 2 / s or more, preferably 250 mm 2 / s or more, more preferably 300 mm 2 / s or more, further preferably 400 mm 2 / s or more. The kinematic viscosity of the refrigerant oil at -10°C is 3000 mm 2 / s or less, preferably 2500 mm 2 / s or less, more preferably 2000 mm 2 / s or less, further preferably 1500 mm 2 / s or less, particularly preferably 1000 mm2 / s or less. The kinematic viscosity at -10°C refers to the kinematic viscosity (hereinafter the same) measured according to JIS K2283:2000. It is considered that the kinematic viscosity at -10°C of the refrigerant oil is within the range, thereby maintaining the necessary lubricating viscosity while being a refrigerant oil monomer, and exhibiting particularly excellent low-temperature fluidity when the refrigerant is dissolved, the oil return property of the evaporator and the like becomes good, and the heat exchange efficiency is improved.

[0032] The kinematic viscosity at -20°C of the refrigerant oil is preferably 10000 mm 2 / s or less, more preferably 7000 mm 2 / s or less, further preferably 3000 mm 2 / s or less, particularly preferably 2500 mm 2 / s or less, preferably 200 mm 2 / s or more, more preferably 500 mm 2 / s or more, further preferably 1000 mm 2 / s or more.

[0033] The kinematic viscosity at 40°C of the refrigerant oil is preferably 2 mm 2 / s or more, 20 mm 2 / s or more, 30 mm 2 / s or more, or 40 mm 2 / s or more, preferably 400 mm 2 / s or less, 250 mm 2 / s or less, 150 mm 2 / s or less, 100 mm 2 / s or less, or 60 mm 2 / s or less.

[0034] The kinematic viscosity at 100°C of the refrigerant oil is not particularly limited as long as the kinematic viscosity at -10°C satisfies the above, and is preferably 4 mm 2 / s or more, 6 mm 2 / s or more, 8 mm 2 / s or more, or 9 mm 2 / s or more, preferably 40 mm 2 / s or less, 25 mm 2 / s or less, 15 mm 2 / s or less, 12 mm 2 / s or less, or 10 mm 2 / s or less.

[0035] The flash point of the refrigerant oil is preferably 250°C or higher, more preferably 270°C or higher, and further preferably 290°C or higher, and can be 350°C or lower, from the viewpoint of improving safety even when a strong flammable refrigerant is used. The flash point refers to the flash point measured according to JIS K2265-4:2007 (Cleveland Open Cup (COC) method).

[0036] The pour point of the refrigerant oil is preferably -10°C or lower, and can be more preferably -20°C or lower. The pour point refers to the pour point measured according to JIS K2269:1987.

[0037] The refrigerant oil contains a lubricating oil base oil and additives as needed. As the lubricating oil base oil, an appropriate lubricating oil base oil is selected so as to become a refrigerant oil having the above-described characteristics, and in addition, so as to become a working fluid having the characteristics described later.

[0038] The lubricating oil base oil can be, for example, a hydrocarbon oil or an oxygen-containing oil. As the hydrocarbon oil, mineral oil, olefin polymer, naphthalene compound, alkylbenzene, and the like can be given. As the oxygen-containing oil, esters such as monoester (ester of monohydric alcohol), polyhydric alcohol ester (ester of polyhydric alcohol having 2 or more hydroxyl groups), complex ester, polyalkylene glycol, polyvinyl ether, polyphenyl ether, perfluoro ether, and the like can be given.

[0039] The lubricating oil base oil is preferably selected from at least one of ester, polyalkylene glycol, and polyvinyl ether, is preferably selected from at least one of polyhydric alcohol ester, complex ester, and polyalkylene glycol, is further preferably selected from at least one of polyhydric alcohol ester and complex ester, and is particularly preferably a mixture of two or more kinds of polyhydric alcohol esters, from the viewpoint of being particularly suitable for obtaining a refrigerant oil having the above-described characteristics and a working fluid having the characteristics described later.

[0040] The mixture of two or more kinds of polyhydric alcohol esters contains, for example, two or more kinds of polyhydric alcohol esters selected from one or two or more kinds of polyhydric alcohols selected from neopentyl glycol, trimethylolpropane, and pentaerythritol and one or two or more kinds of fatty acids selected from fatty acids having a carbon number of 14 to 18. As the fatty acid, a fatty acid in which an unsaturated fatty acid is a main component is particularly preferable, and as the unsaturated fatty acid, one or two or more kinds of unsaturated fatty acids selected from oleic acid, palmitoleic acid, linoleic acid, and linolenic acid are preferable.

[0041] The fatty acid having a carbon number of 14 to 18 constituting the polyol ester (mixture) can include a saturated fatty acid. The ratio of the unsaturated fatty acid in the fatty acid having a carbon number of 14 to 18 is preferably 70% by mass or more, can be 75% by mass or more, 80% by mass or more, or 84% by mass or more, and can be 100% by mass or less, 98% by mass or less, or 96% by mass or less. The ratio of the saturated fatty acid in the fatty acid having a carbon number of 14 to 18 is preferably 0% by mass or more, can be 2% by mass or more, or 4% by mass or more, and can be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 16% by mass or less.

[0042] The polyol esters can be polyol esters obtained using a plurality of the aforementioned polyols or the aforementioned fatty acids as raw materials, or can be obtained by mixing two or more polyol esters obtained from one of the aforementioned polyols and one of the aforementioned fatty acids. In addition, the polyol esters can be partial esters in which a part of two or more of the hydroxyl groups in the polyol is esterified, or can be total esters in which all of the hydroxyl groups are esterified. The mixture can include two or more partial esters, two or more total esters, one or more partial esters, and one or more total esters.

[0043] The content of the lubricating oil base oil can be 80% by mass or more, 90% by mass or more, or 95% by mass or more, based on the total amount of the refrigerant oil.

[0044] As the additives, acid scavengers such as epoxy compounds, carbodiimide compounds, antioxidants such as phenol compounds, amine compounds, anti-wear agents such as phosphorus compounds, sulfur compounds, oiliness agents such as ester compounds, antifoaming agents such as silicone compounds, metal deactivators such as benzotriazole compounds, viscosity index improvers such as poly(meth)acrylate compounds, and the like can be given. The content of the additives is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and can be 5% by mass or less, or 2% by mass or less, based on the total amount of the refrigerant oil.

[0045] From the viewpoint of high responsiveness in terms of wear resistance, the refrigerant oil preferably contains a phosphorus-containing anti-wear agent. As the phosphorus-containing anti-wear agent, primary phosphoric acid esters such as trimethyl phosphate, triphenyl phosphate, trialkyl phosphate, and tris(alkylphenyl) phosphate, phosphorous acid esters such as trialkyl phosphite, and thiophosphoric acid esters such as triphenyl phosphite can be given. The content of the phosphorus-containing anti-wear agent can be preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and can be 5% by mass or less, or 2% by mass or less, based on the total amount of the refrigerant oil.

[0046] The content of the refrigerant oil in the working fluid can be 1 part by mass or more, or 2 parts by mass or more, and can be 500 parts by mass or less, or 400 parts by mass or less, with respect to 100 parts by mass of the refrigerant.

[0047] The working fluid is one in which the refrigerant solubility is 40 mass% or less at 80°C and 2.8 MPa. The refrigerant solubility is preferably 35 mass% or less, and more preferably 32 mass% or less or 30 mass% or less. The lower limit of the refrigerant solubility in the working fluid at 80°C and 2.8 MPa is not particularly limited as long as there is some degree of solubility, and is preferably 5 mass% or more, more preferably 15 mass% or more, further preferably 20 mass% or more, and particularly preferably 25 mass% or more. When R290 is used as the refrigerant, it is preferable to set the refrigerant solubility under the above conditions within the above range, and particularly by setting the refrigerant solubility under the above conditions to 20 mass% or more and 35 mass% or less, the miscibility with the refrigerant and the refrigerant solubility viscosity can be maintained in good balance.

[0048] The refrigerant solubility in the working fluid at 40°C and 0.7 MPa is preferably 20 mass% or less, more preferably 15 mass% or less, and preferably 5 mass% or more. When R290 is used as the refrigerant, it is preferable to set the refrigerant solubility under the above conditions within the above range. In this less severe condition than the more severe condition of 80°C and 2.8 MPa, by setting the refrigerant solubility to 5 mass% or more and 15 mass% or less, the miscibility with the refrigerant and the refrigerant solubility viscosity can be maintained in good balance.

[0049] The refrigerant solubility S (mass%) of the working fluid is represented by the amount of refrigerant (g) in the working fluid / (the amount of refrigerant (g) + the amount of refrigerant oil (g)) x 100, and is measured according to the following procedure.

[0050] First, in a pressure-resistant container (for example, 200 to 500 cm 3 ) equipped with a vibration or rotary viscometer, a thermometer, and a pressure gauge, refrigerant oil is filled, and after vacuum degassing in the pressure-resistant container, refrigerant is filled so as to adjust the temperature and the pressure in the pressure-resistant container to the conditions of 80°C and 2.8 MPa or 40°C and 0.7 MPa. The refrigerant solubility S (mass%) is calculated from the amounts of refrigerant oil and refrigerant filled at this time, and the volume and the refrigerant vapor density of the refrigerant vapor portion in the pressure-resistant container, according to the following formula.

[0051] S = (Rf - Vv x Dv) x 100 / ((Rf - Vv x Dv) + Of)

[0052] S: refrigerant solubility of the working fluid (mass%)

[0053] Rf: amount of refrigerant filled in the pressure-resistant container (g)

[0054] Vv: volume of refrigerant vapor portion in pressure-resistant container (cm 3 )(= volume of pressure-resistant container V - working fluid volume Vmix)

[0055] Dv: refrigerant vapor density (g / cm 3 )

[0056] Of: filling amount of refrigeration oil to pressure-resistant container (g)

[0057] The working fluid is passed through the above-mentioned specific refrigeration oil, whereby refrigerant solubility viscosity can be ensured under high-temperature high-pressure conditions. Specifically, refrigerant solubility viscosity of the working fluid under conditions of a temperature of 80°C and an absolute pressure of 2.8 MPa is ensured to be, for example, 1.0 mm 2 / s or more, and 1.2 mm 2 / s or more, and 1.5 mm 2 / s or more can be preferred. The refrigerant solubility viscosity can be preferably 5.0 mm 2 / s or less, and 4.0 mm 2 / s or less, and 3.0 mm 2 / s or less. When R290 is used as the refrigerant, for example, it is particularly preferable that the refrigerant solubility viscosity of the working fluid be in the above-mentioned range.

[0058] The refrigerant solubility viscosity of the working fluid under conditions of a temperature of 40°C and an absolute pressure of 0.7 MPa is preferably 4.0 mm 2 / s or more, and 5.0 mm 2 / s or more, and 8 mm 2 / s or more, or 12 mm 2 / s or more, and 30 mm 2 / s or less, and 25 mm 2 / s or less, or 20 mm 2 / s or less. When R290 is used as the refrigerant, for example, it is particularly preferable that the refrigerant solubility viscosity of the working fluid be in the above-mentioned range.

[0059] The refrigerant solubility viscosity (mm 2 / s) of the working fluid is measured according to the following procedure.

[0060] The absolute viscosity (mPa-s) of the working fluid is measured using a vibration-type or rotation-type viscometer under the conditions described in the above-mentioned refrigerant solubility amount S measurement method. The refrigerant solubility viscosity R-VIS (mm 2 / s) of the working fluid is the absolute viscosity P (mPa-s) measured divided by the working fluid density Dw (g / cm 3) and the P / Dw is calculated. Here, the working fluid density Dw (g / cm 3 ) is calculated according to the following formula.

[0061] Dw= (Rf - Vv x Dv + Of) / Vmix

[0062] Dw: Working fluid density (g / cm 3 )

[0063] Rf: Filling amount of refrigerant to pressure-resistant container (g)

[0064] Vv: Volume occupied by refrigerant vapor in pressure-resistant container (cm 3 )

[0065] Dv: Refrigerant vapor density (g / cm 3 )

[0066] Of: Filling amount of refrigerant oil to pressure-resistant container (g)

[0067] Vmix: Working fluid volume (cm 3 )

[0068] The kinematic viscosity of the working fluid at -20°C is preferably 1000 mm 2 / s or less, more preferably 700 mm 2 / s or less, further preferably 300 mm 2 / s or less, particularly preferably 200 mm 2 / s or less, preferably 20 mm 2 / s or more, 50 mm 2 / s or more, further preferably 100 mm 2 / s or more.

[0069] The kinematic viscosity of the working fluid at -10°C is preferably 20 mm 2 / s or more, more preferably 30 mm 2 / s or more, further preferably 40 mm 2 / s or more, preferably 300 mm 2 / s or less, more preferably 250 mm 2 / s or less, further preferably 200 mm 2 / s or less, particularly preferably 150 mm 2 / s or less, most preferably 100 mm 2 / s or less.

[0070] The low-temperature-side two-layer separation temperature of the working fluid preferably has a phase solubility region of preferably -10°C or lower, more preferably -20°C or lower, further preferably -30°C or lower, particularly preferably -40°C or lower. In addition, if the refrigerant and the refrigeration oil are excessively dissolved, there is a tendency for the viscosity of the refrigerant to decrease, and therefore, the low-temperature-side two-layer separation temperature of the working fluid preferably has a phase solubility region of preferably -70°C or higher, more preferably -60°C or higher, further preferably -50°C or higher. Particularly when the mass ratio of the refrigeration oil to the refrigerant in the working fluid (refrigeration oil / refrigerant) is 1 / 9 to 4 / 6, the low-temperature-side two-layer separation temperature of the working fluid can be -10°C or lower, -20°C or lower, -30°C or lower, or -40°C or lower, and can be -70°C or higher, -60°C or higher, or -50°C or higher. When the mass ratio of the refrigeration oil to the refrigerant in the working fluid (refrigeration oil / refrigerant) is 6 / 4 to 9 / 1, particularly 6 / 4 to 7 / 3, the low-temperature-side two-layer separation temperature of the working fluid can be -10°C or lower, -20°C or lower, -30°C or lower, or -40°C or lower, and can be -70°C or higher, -60°C or higher, or -50°C or higher.

[0071] The refrigeration machine 10 and the working fluid described above use a refrigeration oil having a specific mixed amine point (20°C or higher and 50°C or lower) and a viscosity index (110 or higher) in the presence of a hydrocarbon refrigerant, and therefore, compared to a case in which a refrigeration oil not having such a specific mixed amine point and a viscosity index is used, the refrigerant solubility viscosity under high-temperature high-pressure conditions can be ensured. In addition, in an embodiment, sufficient viscosity characteristics are ensured, lubricity of sliding portions such as bearings is maintained, and flowability under low temperatures is improved, oil return from an evaporator and an accumulator is ensured, and the reliability and efficiency of the refrigeration machine can be improved.

[0072] Example

[0073] The present application is further specifically described below based on examples, but the present application is not limited to the examples.

[0074] (Example 1)

[0075] A mixed ester of neopentyl glycol and mono- and di-esters of fatty acids having 14 to 18 carbons and a mixed ester of pentaerythritol and tri- and tetra-esters of fatty acids having 14 to 18 carbons were mixed at a mass ratio of 3 / 7 (= mixed ester A / mixed ester B) to prepare the refrigerant oil of Example 1. Note that the fatty acids having 14 to 18 carbons that constitute the above polyol ester (mixture) contain unsaturated fatty acids (containing unsaturated fatty acids having 16 carbons and unsaturated fatty acids having 18 carbons as main components) and saturated fatty acids (containing saturated fatty acids having 14 carbons, saturated fatty acids having 16 carbons, and saturated fatty acids having 18 carbons as main components) at a mass ratio of 94 / 6 (= unsaturated fatty acids / saturated fatty acids).

[0076] (Example 2)

[0077] A mixed ester of trimethylolpropane and di- and tri-esters of fatty acids having 14 to 18 carbons and a tetra-ester of pentaerythritol and branched saturated acids having 18 carbons were mixed at a mass ratio of 9 / 1 (= mixed ester 2A / tetra-ester 2B) to prepare the refrigerant oil of Example 2. Note that the fatty acids having 14 to 18 carbons that constitute the above polyol ester (mixture) contain unsaturated fatty acids (containing unsaturated fatty acids having 16 carbons and unsaturated fatty acids having 18 carbons as main components) and saturated fatty acids (containing saturated fatty acids having 14 carbons, saturated fatty acids having 16 carbons, and saturated fatty acids having 18 carbons as main components) at a mass ratio of 85 / 15 (= unsaturated fatty acids / saturated fatty acids).

[0078] (Example 3)

[0079] A complex ester of neopentyl glycol / 1,4-butanediol / 3,5,5-trimethylhexanol / adipic acid (= 1 / 0.3 / 2.5 / 2.4 (molar ratio)) and a mixed ester of neopentyl glycol and mono- and di-esters of fatty acids having 14 to 18 carbons were mixed at a mass ratio of 7 / 3 (= complex ester / mixed ester) to prepare the refrigerant oil of Example 3. Note that the above fatty acids having 14 to 18 carbons contain unsaturated fatty acids (containing unsaturated fatty acids having 16 carbons and unsaturated fatty acids having 18 carbons as main components) and saturated fatty acids (containing saturated fatty acids having 14 carbons, saturated fatty acids having 16 carbons, and saturated fatty acids having 18 carbons as main components) at a mass ratio of 94 / 6 (= unsaturated fatty acids / saturated fatty acids).

[0080] (Comparative Example 1)

[0081] A tetra-ester of pentaerythritol and 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid (= 1 / 1 (molar ratio)) was used to prepare the refrigerant oil of Comparative Example 1.

[0082] (Comparative Example 2)

[0083] A refrigeration machine oil of Comparative Example 2 was prepared using a paraffin-based highly purified mineral oil.

[0084] The properties of each of the refrigeration machine oils prepared are shown in Table 1. In addition, with respect to the working fluid when each of the refrigeration machine oils and propane (R290) as the refrigerant were used, the two-layer separation temperature of each oil / refrigerant ratio (mass ratio), the kinematic viscosity at -10°C and -20°C each, the refrigerant solubility amount in the working fluid at a temperature of 80°C and an absolute pressure of 2.8 MPa, and the refrigerant solubility viscosity at a temperature of 80°C and an absolute pressure of 2.8 MPa are shown in Table 1. Note that the kinematic viscosity of the working fluid at -10°C and -20°C each is a calculated value assuming a 90% reduction from the kinematic viscosity of the refrigeration machine oil itself.

[0085] [Table 1]

[0086]

[0087] BRIEF DESCRIPTION OF DRAWINGS

[0088] 1... compressor, 2... condenser, 3... expansion mechanism, 4... evaporator, 5... flow path, 6... refrigerant circulation system, 7... liquid accumulator, 10... refrigeration machine.

Claims

1. A working fluid comprising a refrigerant and refrigeration oil, said working fluid being filled into a refrigerant circulation system having a compressor, a condenser, an expander, an evaporator, and a receiver. The refrigerant contains only hydrocarbon refrigerants with 2 to 4 carbon atoms. The refrigeration oil contains a lubricating oil base oil, which is selected from at least one of esters, polyalkylene glycols, and polyvinyl ethers. The esters contain only polyol esters, and the polyol esters contain two or more polyols selected from neopentyl glycol, trimethylolpropane, and pentaerythritol, and polyol esters of one or more fatty acids selected from fatty acids having carbon numbers from 14 to 18. The mixing aniline point of the refrigeration oil is above 20°C and below 50°C, and the viscosity index of the refrigeration oil is above 150. The working fluid has a low-temperature side layer separation temperature below -10°C when the mass ratio of refrigeration oil to refrigerant is 1 / 9 to 4 / 6. Under conditions of 80°C and 2.8 MPa absolute pressure, the refrigerant dissolved in the working fluid is less than 40% by mass. The kinematic viscosity of the refrigeration oil at -10°C is 200 mmHg. 2 / s or higher and 3000mm 2 / s or less.

2. The working fluid according to claim 1, wherein, The kinematic viscosity of the refrigeration oil at -20°C is 10000 mm³ / s. 2 / s or less.

3. The working fluid according to claim 2, wherein, The refrigeration oil has a mixing aniline point above 25°C and below 50°C, and a kinematic viscosity of 200 mmHg at -10°C. 2 / s or higher and 2500mm 2 The kinematic viscosity of the refrigeration oil is below / s, or the kinematic viscosity at -20°C is 7000 mm³ / s. 2 / s or less.

4. The working fluid according to any one of claims 1 to 3, wherein, The flash point of the refrigeration oil is above 250°C.

5. The working fluid according to any one of claims 1 to 3, wherein, The refrigeration oil contains phosphorus-containing anti-wear agents.

6. The working fluid according to claim 4, wherein, The refrigeration oil contains phosphorus-containing anti-wear agents.

7. The working fluid according to any one of claims 1 to 3, wherein, Under conditions of 40°C and 0.7 MPa absolute pressure, the amount of refrigerant dissolved in the working fluid is less than 15% by mass.

8. The working fluid according to claim 4, wherein, Under conditions of 40°C and 0.7 MPa absolute pressure, the amount of refrigerant dissolved in the working fluid is less than 15% by mass.

9. The working fluid according to claim 5, wherein, Under conditions of 40°C and 0.7 MPa absolute pressure, the amount of refrigerant dissolved in the working fluid is less than 15% by mass.

10. The working fluid according to claim 6, wherein, Under conditions of 40°C and 0.7 MPa absolute pressure, the amount of refrigerant dissolved in the working fluid is less than 15% by mass.

11. A refrigeration unit comprising a refrigerant circulation system having a compressor, a condenser, an expansion mechanism, an evaporator, and a liquid receiver. The refrigerant circulation system is filled with a working fluid containing refrigerant and refrigeration oil. The refrigerant contains only hydrocarbon refrigerants with 2 to 4 carbon atoms. The refrigeration oil contains a lubricating oil base oil, which is selected from at least one of esters, polyalkylene glycols, and polyvinyl ethers. The esters contain only polyol esters, and the polyol esters contain two or more polyols selected from neopentyl glycol, trimethylolpropane, and pentaerythritol, and polyol esters of one or more fatty acids selected from fatty acids having carbon numbers from 14 to 18. The mixing aniline point of the refrigeration oil is above 20°C and below 50°C, and the viscosity index of the refrigeration oil is above 150. Under conditions of 80°C and 2.8 MPa absolute pressure, the refrigerant dissolved in the working fluid is less than 40% by mass. The working fluid has a low-temperature side layer separation temperature below -10°C when the mass ratio of refrigeration oil to refrigerant is 1 / 9 to 4 / 6. The kinematic viscosity of the refrigeration oil at -10°C is 200 mmHg. 2 / s or higher and 3000mm 2 / s or less.

12. A refrigeration oil, which is a refrigeration oil filled together with refrigerant in a refrigerant circulation system having a compressor, condenser, expansion mechanism, evaporator and receiver. The refrigerant contains only hydrocarbon refrigerants with 2 to 4 carbon atoms. The refrigeration oil contains a lubricating oil base oil, which is selected from at least one of esters, polyalkylene glycols, and polyvinyl ethers. The esters contain only polyol esters, and the polyol esters contain two or more polyols selected from neopentyl glycol, trimethylolpropane, and pentaerythritol, and polyol esters of one or more fatty acids selected from fatty acids having carbon numbers from 14 to 18. The mixing aniline point of the refrigeration oil is above 20°C and below 50°C, and the viscosity index of the refrigeration oil is above 150. Under conditions of 80°C and 2.8 MPa absolute pressure, the refrigerant dissolved in the working fluid containing the refrigerant and the refrigeration oil is less than 40% by mass. The working fluid has a low-temperature side layer separation temperature below -10°C when the mass ratio of refrigeration oil to refrigerant is 1 / 9 to 4 / 6. The kinematic viscosity of the refrigeration oil at -10°C is 200 mmHg. 2 / s or higher and 3000mm 2 / s or less.

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