Patent Description:
Refrigerants with very low global warming potential (GWP < <NUM>) are needed to meet regulatory requirements for various applications and market segments. Several alternatives have been developed, to replace conventional high GWP refrigerants, such as R-404A. Many of the low GWP refrigerants suggested for this replacement, such as R-457A, exhibit higher discharge temperatures than the high GWP refrigerants, such as R-404A which they replace. This can limit their effectiveness by reducing a compressor's operating envelope. This can be particularly critical for low back pressure (LBP) hermetic reciprocating compressors, used in low temperature refrigeration, as many of these models do not employ an active discharge temperature control system, such as liquid or vapor injection. Left unchecked, the higher discharge temperatures generated in these LBP applications could potentially reduce compressor longevity. Without the ability to actively mitigate discharge temperatures, use of these compressors may be limited to applications with higher evaporator temperatures and/or lower condensing temperatures. Marek Zgliczynski et al: Thermal Profile of a reciprocating compressor using low GWP refrigerants, International Engineering conference, <NUM> July <NUM>, XP055713035 describes refrigerant R-457A (HFC-<NUM>, HFO-1234yf, HFC-152a in a weight ratio <NUM>/<NUM>/<NUM>) and R-454C (HFC-<NUM>, HFO-1234yf in a weight ratio <NUM>/<NUM>).

In an exemplary embodiment, a refrigeration system including a low back pressure (LBP) hermetic reciprocating compressor and a refrigerant composition, wherein the refrigerant composition includes difluoromethane (R-<NUM>) and <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf) in the amounts defined in claim <NUM>, or wherein the refrigerant composition includes <NUM>,<NUM>-difluoroethane (R-152a), difluoromethane (R-<NUM>) and <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf) in the amounts defined in claim <NUM>.

In another exemplary embodiment, a method of replacing a first refrigerant composition comprising R-404A, R-457A, R-<NUM>, or R-454C with a second refrigerant composition comprising <NUM> to <NUM> weight percent <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene and <NUM> weight percent to <NUM> weight percent difluoromethane. The replacing is performed in a refrigeration system including a low back pressure (LBP) hermetic reciprocating compressor.

In another exemplary embodiment, a method of operating a low back pressure (LBP) hermetic reciprocating compressor as part of a refrigeration system. The method includes the steps of receiving by a low back pressure (LBP) hermetic reciprocating compressor a refrigerant composition as defined in claim <NUM> including difluoromethane (R-<NUM>), and <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf) and compressing by low back pressure (LBP) hermetic reciprocating compressor the refrigerant composition. The discharge temperature of the compressor is between <NUM> and <NUM>.

Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment which illustrates, by way of example, the principles of the invention.

Provided are low global warming potential (GWP) refrigerant compositions exhibiting low discharge temperatures and high heat capacity. The refrigerant compositions are suitable for use in low back pressure (LBP) hermetic reciprocating compressors, used in low temperature refrigeration applications.

An embodiment of a refrigeration system <NUM> is shown in <FIG>. In the embodiment of <FIG> the refrigeration system <NUM> includes a receiving tank <NUM>. The receiving tank <NUM> contains a refrigerant composition and supplies the refrigerant composition to the other components of the refrigeration system <NUM> during operation.

The refrigerant composition may be selected from materials having a low global warming potential (GWP). In some embodiments, the refrigerant composition exhibits a GWP of less than <NUM>, less than <NUM>, and/or less than <NUM>. In some embodiments, the refrigerant composition may be selected to replace a refrigerant composition having a high GWP. In some embodiments, the refrigerant composition may be selected to replace refrigerant compositions such as R-404A, R-<NUM>, R-454C, R-457A, and R-507A. Replacement compositions desirably provide similar or improved properties to as compared to R-404A. Similar properties may include flammability, discharge temperature, and heat transport capacity.

Suitable refrigerant compositions for the replacement of R-404A refrigerants include difluoromethane (R-<NUM>), and <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf) in amounts as defined in claim <NUM> or <NUM>. In some embodiments, the refrigerant compositions may further include <NUM>,<NUM>-difluoroethane (R-152a) in amounts as defined in claim <NUM> or <NUM>. In some embodiments, the refrigerant composition may be a non-azeotropic refrigerant composition.

In an embodiment, the refrigeration system <NUM> may be a direct expansion refrigeration system. During operation of the refrigeration system <NUM>, the refrigerant composition circulates throughout the refrigeration system <NUM> as part of the heat transfer processes. In the example of <FIG>, the receiving tank <NUM> is operably coupled to an evaporator <NUM> via an expansion device <NUM> such as an orifice tube, capillary tube, thermal expansion valve or electronic expansion valve. The expansion device <NUM>, supplies the refrigerant composition to the evaporator <NUM>. In some embodiments, the receiving tank <NUM> is optional. In such embodiments, the refrigerant is provided directly to the evaporator <NUM> without a receiver. In an embodiment, the refrigerant composition is transported between the receiving tank <NUM> and evaporator <NUM> via the expansion device <NUM>. In some embodiments, the evaporator <NUM> may be operated in a low temperature mode. For the purposes described herein low temperature evaporator operation is between - <NUM> and -<NUM>. In some embodiments, the evaporator <NUM> may be operated in a medium temperature mode. For the purposes described herein medium temperature evaporator operation is between -<NUM> and -<NUM>.

The evaporator <NUM> is operably connected to a compressor <NUM> via a suction line <NUM>. The compressor <NUM> increases the pressure of the vaporous refrigerant entering the compressor <NUM>. In some embodiments, the compressor <NUM> may be a low back pressure (LBP) hermetic reciprocating compressor. In an embodiment, the refrigerant composition is a non-azeotropic composition including difluoromethane (R-<NUM>), and <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf). In another embodiment, the refrigerant composition is a non-azeotropic composition including difluoromethane (R-<NUM>), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf), and <NUM>,<NUM>-difluoroethane (R-152a). In some embodiments, the discharge temperature of the low back pressure (LBP) hermetic reciprocating compressor is between <NUM> and <NUM>, between <NUM> and <NUM>, between <NUM> and <NUM> and combinations thereof.

The compressor <NUM> is operably connected to a condenser <NUM>. The condenser <NUM> receives the pressurized vapor refrigerant and allows the pressurized vapor evaporator to transfer heat to an external medium and condense to the liquid state.

The condenser <NUM> is operably connected to the receiving tank <NUM>. The liquid refrigerant returns to the receiving tank <NUM> and is again available to absorb heat by again being provided to the evaporator <NUM>.

In compositions intended to replace conventional high GWP refrigerant, it is desirable that the replacement refrigerant composition exhibit a low GWP as well as similar or improved refrigerant properties compared to the refrigerant it is replacing. In some embodiments, the refrigerant composition is intended to replace R-457A. In an embodiment, the refrigerant composition includes difluoromethane (R-<NUM>) in an amount of <NUM> to <NUM> weight percent based on the weight of the refrigerant composition and <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf) in an amount of <NUM> to <NUM> weight percent based on the weight of the refrigerant composition. In one embodiment, the refrigerant composition includes difluoromethane (R-<NUM>) in an amount of <NUM> weight percent based on the weight of the refrigerant composition and <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf) in an amount of <NUM> weight percent based on the weight of the refrigerant composition.

In an embodiment, the refrigerant composition is a non-azeotropic composition including difluoromethane (R-<NUM>), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf), and <NUM>, <NUM> -difluoroethane (R-152a), wherein the refrigerant composition includes difluoromethane (R-<NUM>) in an amount of <NUM> to <NUM> weight percent, and/or about <NUM> weight percent based on the weight of the refrigerant composition, <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf) in an amount of <NUM> to <NUM> weight percent based on the weight of the refrigerant composition, and <NUM>,<NUM>-difluoroethane (R-152a) in an amount of <NUM> to <NUM> weight percent based on the weight of the refrigerant composition.

In some embodiments, the refrigerant composition is intended to replace R-457A. In an embodiment, the refrigerant composition includes difluoromethane (R-<NUM>) in an amount of <NUM> weight percent based on the weight of the refrigerant composition, <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf) in an amount of <NUM> to <NUM> weight percent based on the weight of the refrigerant composition, and <NUM>,<NUM>-difluoroethane (R-152a) in an amount of <NUM> to <NUM> weight percent based on the weight of the refrigerant composition. In one embodiment, the refrigerant composition includes difluoromethane (R-<NUM>) in an amount of <NUM> weight percent based on the weight of the refrigerant composition and <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf) in an amount of <NUM> weight percent based on the weight of the refrigerant composition.

The refrigerant compositions may further comprise one or more optional non-refrigerant components selected from the group consisting of lubricants, dyes (including UV dyes), solubilizing agents, compatibilizers, stabilizers, tracers, antiwear agents, extreme pressure agents, corrosion and oxidation inhibitors, metal surface energy reducers, metal surface deactivators, free radical scavengers, foam control agents, viscosity index improvers, pour point depressants, detergents, viscosity adjusters, and mixtures thereof. In some embodiments, the optional non-refrigerant components may be referred to as additives. Indeed, many of these optional non-refrigerant components fit into one or more of these categories and may have qualities that lend themselves to achieve one or more performance characteristic.

In order to facilitate the operation and extend the service life of the compressor <NUM> a lubricant may be included in the refrigerant composition. Solubility and miscibility of the lubricant with the refrigerant composition may improve the performance of the lubricant and extend the service life of the compressor <NUM>. In some embodiments, the lubricant may include mineral oil, alkylbenzene, polyol esters, polyalkylene glycols, polyvinyl ethers, polycarbonates, perfluoropolyethers, silicones, silicate esters, phosphate esters, paraffins, naphthenes, polyalpha-olefins, and combinations thereof. In one embodiment, the lubricant includes a polyol ester.

An optional non-refrigerant component used with the refrigerant compositions may be a stabilizer selected from the group consisting of hindered phenols, thiophosphates, butylated triphenylphosphorothionates, organo phosphates, or phosphites, aryl alkyl ethers, terpenes, terpenoids, epoxides, fluorinated epoxides, oxetanes, ascorbic acid, thiols, lactones, thioethers, amines, nitromethane, alkylsilanes, benzophenone derivatives, aryl sulfides, divinyl terephthalic acid, diphenyl terephthalic acid, ionic liquids, and mixtures thereof, meaning mixtures of any of the stabilizers disclosed in this paragraph.

The stabilizer may be selected from the group consisting of tocopherol; hydroquinone; t-butyl hydroquinone; monothiophosphates; and dithiophosphates, commercially available from Ciba Specialty Chemicals, Basel, Switzerland, hereinafter "Ciba", under the trademark Irgalube® <NUM>; dialkylthiophosphate esters, commercially available from Ciba under the trademarks Irgalube® <NUM> and Irgalube® <NUM>, respectively; butylated triphenylphosphorothionates, commercially available from Ciba under the trademark Irgalube® <NUM>; amine phosphates, commercially available from Ciba under the trademark Irgalube® <NUM> (Ciba); hindered phosphites, commercially available from Ciba as Irgafos® <NUM> and Tris-(di-tert-butylphenyl)phosphite, commercially available from Ciba under the trademark Irgafos® OPH; (Di-n-octyl phosphite); and iso-decyl diphenyl phosphite, commercially available from Ciba under the trademark Irgafos® DDPP; trialkyl phosphates, such as trimethyl phosphate, triethylphosphate, tributyl phosphate, trioctyl phosphate, and tri(<NUM>-ethylhexyl)phosphate; triaryl phosphates including triphenyl phosphate, tricresyl phosphate, and trixylenyl phosphate; and mixed alkyl-aryl phosphates including isopropylphenyl phosphate (IPPP), and bis(t-butylphenyl)phenyl phosphate (TBPP); butylated triphenyl phosphates, such as those commercially available under the trademark Syn-O-Ad® including Syn-O-Ad® <NUM>; tert-butylated triphenyl phosphates such as those commercially available under the trademark Durad®<NUM>; isopropylated triphenyl phosphates such as those commercially available under the trademarks Durad® <NUM> and Durad®<NUM>; anisole; <NUM>,<NUM>-dimethoxybenzene; <NUM>,<NUM>-diethoxybenzene; <NUM>,<NUM>,<NUM>-trimethoxybenzene; myrcene, alloocimene, limonene (in particular, d-limonene); retinal; pinene (α or β forms); menthol; geraniol; farnesol; farnesene (α or β forms); phytol; Vitamin A; terpinene; delta-<NUM>-carene; terpinolene; phellandrene; fenchene; dipentene; caratenoids, such as lycopene, beta carotene, and xanthophylls, such as zeaxanthin; retinoids, such as hepaxanthin and isotretinoin; bornane; <NUM>,<NUM>-propylene oxide; <NUM>,<NUM>-butylene oxide; n-butyl glycidyl ether; trifluoromethyloxirane; <NUM>,<NUM>-bis(trifluoromethyl)oxirane; <NUM>-ethyl-<NUM>-hydroxymethyl-oxetane, such as OXT-<NUM> (Toagosei Co. , Ltd); <NUM>-ethyl-<NUM>-((phenoxy)methyl)-oxetane, such as OXT-<NUM> (Toagosei Co. , Ltd); <NUM>-ethyl-<NUM>-((<NUM>-ethyl-hexyloxy)methyl)-oxetane, such as OXT-<NUM> (Toagosei Co. , Ltd); ascorbic acid; methanethiol (methyl mercaptan); ethanethiol (ethyl mercaptan); Coenzyme A; dimercaptosuccinic acid (DMSA); grapefruit mercaptan ((R)-<NUM>-(<NUM>-methylcyclohex-<NUM>-enyl)propane-<NUM>-thiol)); cysteine ((R)-<NUM>-amino-<NUM>-sulfanyl-propanoic acid); lipoamide (<NUM>,<NUM>-dithiolane-<NUM>-pentanamide); <NUM>,<NUM>-bis(<NUM>,<NUM>-dimethylethyl)-<NUM>-[<NUM>,<NUM>(or <NUM>,<NUM>)-dimethylphenyl]-<NUM>(<NUM>)-benzofuranone, commercially available from Ciba under the trademark Irganox® HP-<NUM>; benzyl phenyl sulfide; diphenyl sulfide; diisopropylamine; dioctadecyl <NUM>,<NUM>'-thiodipropionate, commercially available from Ciba under the trademark Irganox® PS <NUM> (Ciba); didodecyl <NUM>,<NUM>'-thiopropionate, commercially available from Ciba under the trademark Irganox® PS <NUM>; di-(<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>-piperidyl)sebacate, commercially available from Ciba under the trademark Tinuvin® <NUM>; poly-(N-hydroxyethyl-<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>-hydroxy-piperidyl succinate, commercially available from Ciba under the trademark Tinuvin® 622LD (Ciba); methyl bis tallow amine; bis tallow amine; phenol-alpha-naphthylamine; bis(dimethylamino)methylsilane (DMAMS); tris(trimethylsilyl)silane (TTMSS); vinyltriethoxysilane; vinyltrimethoxysilane; <NUM>,<NUM>-difluorobenzophenone; <NUM>',<NUM>'-dihydroxyacetophenone; <NUM>-aminobenzophenone; <NUM>-chlorobenzophenone; benzyl phenyl sulfide; diphenyl sulfide; dibenzyl sulfide; ionic liquids; and mixtures and combinations thereof.

The optional non-refrigerant component which is used with compositions of the present invention may alternatively be a tracer. The tracer may be a single compound or two or more tracer compounds from the same class of compounds or from different classes of compounds. In some embodiments, the tracer is present in the compositions at a total concentration of about <NUM> part per million by weight (ppm) to about <NUM> ppm, based on the weight of the total composition. In other embodiments, the tracer is present at a total concentration of about <NUM> ppm to about <NUM> ppm. In other embodiments, the tracer is present at a total concentration of about <NUM> ppm to about <NUM> ppm. In other embodiments, the tracer is present at a total concentration of about <NUM> ppm to about <NUM> ppm. In other embodiments, the tracer is present at a total concentration of about <NUM> ppm to about <NUM> ppm. Alternatively, the tracer is present at a total concentration of about <NUM> ppm to about <NUM> ppm.

The tracer may be selected from the group consisting of hydrofluorocarbons (HFCs), deuterated hydrofluorocarbons, chlorofluororcarbons (CFCs), hydrofluorochlorocarbons (HCFCs), hydrofluoroolefins (HFOs), chlorocarbons, perfluorocarbons, fluoroethers, brominated compounds, iodated compounds, alcohols, aldehydes and ketones, nitrous oxide and combinations thereof. Alternatively, the tracer may be selected from the group consisting of trifluoromethane (HFC-<NUM>), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (HFO-1234ze, cis or trans), <NUM>,<NUM>,<NUM>-trifluoropropene (HFO-1243zt), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>-pentafluoropropene (HFO-1225ye, E or Z isomer), dichlorodifluoromethane (CFC-<NUM>), chlorodifluoromethane HCFC-<NUM>), methyl chloride (R-<NUM>), chlorofluoromethane (HCFC-<NUM>), fluoroethane (HFC-<NUM>), <NUM>,<NUM>,<NUM>-trifluoroethane (HFC-143a), chloropentafluoroethane (CFC-<NUM>), <NUM>,<NUM>-dichloro-<NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane (CFC-<NUM>), <NUM>,<NUM>-dichloro-<NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane (CFC-114a), <NUM>-chloro-<NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane (HCFC-<NUM>), pentafluoroethane (HFC-<NUM>), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane (HFC-<NUM>), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane (HFC-134a), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-hexafluoropropane (HFC-236fa), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-heptafluoropropane (HFC-227ea), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>- heptafluoropropane (HFC-227ea), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>-pentafluoropropane(HFC-245fa), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>-pentafluoropropane (HFC-245cb), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>-pentafluoropropane (HFC-245eb), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropane (HFC-254cb), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropane (HFC-254eb), <NUM>,<NUM>,<NUM>-trifluoropropane (HFC-263fb), <NUM>,<NUM>-difluoro-<NUM>-chloroethylene (HCFC-<NUM>), <NUM>-chloro-<NUM>,<NUM>,<NUM>-trifluoroethylene (CFC-<NUM>), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>-pentafluorobutane (HFC-365mfc), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-decafluoropentane (HFC-<NUM>-10mee), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-tetradecafluoroheptane, hexafluorobutadiene, <NUM>,<NUM>,<NUM>-trifluoropropyne, iodotrifluoromethane, deuterated hydrocarbons, deuterated hydrofluorocarbons, perfluorocarbons, fluoroethers, brominated compounds, iodated compounds, alcohols, aldehydes, ketones, nitrous oxide (N<NUM>O) and mixtures thereof. In some embodiments, the tracer is a blend containing two or more hydrofluorocarbons, or one hydrofluorocarbon in combination with one or more perfluorocarbons. In other embodiments, the tracer is a blend of at least one CFC and at least one HCFC, HFC, or PFC.

The tracer may be added to the compositions of the present invention in predetermined quantities to allow detection of any dilution, contamination or other alteration of the composition. Additionally, the tracers may allow detection of product that infringes existing patent rights, by identification of the patent owner's product versus competitive infringing product. Further, in one embodiment, the tracer compounds may allow detection of a manufacturing process by which a product is produced.

In some embodiments, an optional surge tank or accumulator <NUM> may be inserted between the evaporator <NUM> and compressor <NUM> to prevent liquid refrigerant and/or lubricant from entering the compressor <NUM>. The surge tank <NUM>, if present, may return any accumulated liquids to the evaporator <NUM>.

In an alternate embodiment, the refrigeration system may be a flooded evaporator refrigeration system <NUM>. <FIG> illustrates a flooded evaporator refrigeration system <NUM>. In the example of <FIG>, the elements of the system are the same as described above for the direct expansion refrigeration system <NUM> except that the capillary tube <NUM> is not present and an optional pump <NUM> may be present to assist the transfer of refrigerant from the receiving tank <NUM> to a flooded evaporator <NUM>. The surge tank <NUM>, if present, may return any accumulated liquids to the receiving tank <NUM> to again be provided to the evaporator <NUM>. The operable connection from the condenser <NUM> to the receiving tank <NUM> further includes an expansion valve <NUM>.

The performance of the inventive refrigerant compositions, as compared to R-457A, is presented in Tables <NUM> to <NUM> below.

Refrigeration performance of compositions of the present invention were compared to R-404A (a mixture of <NUM> weight percent HFC-<NUM> (pentafluoroethane), <NUM> weight percent HFC-143a (<NUM>,<NUM>,<NUM>-trifluoroethane), and <NUM> weight percent HFC-134a (<NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane)), R-<NUM> (propane), R-454C (a mixture containing <NUM> weight percent HFC-<NUM> and <NUM> weight percent HFO-1234yf) and R-457A (a mixture containing <NUM> weight percent HFC-<NUM>, <NUM> weight percent HFO-1234yf, and <NUM> weight percent HFC-152a (<NUM>,<NUM>-difluoroethane). Performance was determined at both low and medium temperature refrigeration conditions.

Results show compositions of the present invention exhibit compressor discharge temperatures lower than R-454C and R-457A. They also have capacities and energy efficiency (COP) comparable to the incumbent refrigerants, and R-457A in particular.

Claim 1:
A refrigeration system, comprising:
a low back pressure (LBP) hermetic reciprocating compressor;
and a refrigerant composition;
wherein the refrigerant composition comprises:
difluoromethane (R-<NUM>), and <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf),
and
wherein the difluoromethane (R-<NUM>) is present in an amount of <NUM> to <NUM> weight percent based on the weight of the refrigerant composition and the <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf) is present in an amount of <NUM> to <NUM> weight percent based on the weight of the refrigerant composition; or
wherein the refrigerant composition further comprises <NUM>,<NUM>-difluoroethane (R-152a) and the difluoromethane (R-<NUM>) is present in an amount of <NUM> to 19weight percent based on the weight of the refrigerant composition, the <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf) is present in an amount of <NUM> to <NUM> weight percent based on the weight of the refrigerant composition, and the <NUM>,<NUM>-difluoroethane is present in an amount of <NUM> to <NUM> weight percent based on the weight of the refrigerant composition.