Compositions

Abstract

To provide non-flammable refrigerant mixtures comprising difluoromethane (R-32) and CO2, which retain the non-flammability of pure CO2.SOLUTION: The invention provides a composition comprising (a) carbon dioxide (R-744, CO2); (b) difluoromethane (R-32); and (c) a third component selected from 1,1,1,2-tetrafluoroethane (R-134a), trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)), 2,3,3,3-tetrafluoropropene (R-1234yf), 1,1,1,2,3,3,3-heptafluoropropane (R-227ea) and mixtures thereof.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to compositions suitable for use as working fluids in air conditioning and refrigeration applications. The compositions disclosed herein are particularly useful in heat pump water heaters, air conditioning systems for trains, buses, automobiles and trucks, commercial refrigeration systems including supermarket display systems and refrigeration rooms (such as walk-in refrigerators and freezers), and transportation refrigeration systems. [Background technology]

[0002] The listing or discussion of a prior-published document or any background art in this specification should not necessarily be taken as an acknowledgement that the document or background art is part of the state of the art or is common general knowledge.

[0003] Carbon dioxide (CO2, R-744) is favored as a low global warming potential (GWP) refrigerant for applications requiring non-flammability of the refrigerant. These applications include air conditioning systems for trains, buses, cars, and trucks, heat pump-water heater systems, commercial refrigeration systems including supermarket display systems and cold rooms, and transportation refrigeration systems installed in refrigerated shipping containers or trucks.

[0004] CO2 has two major disadvantages compared to other fluorocarbon refrigerants for use in the same applications: First, it suffers from low energy efficiency at ambient temperatures above about 25-30°C, and second, its operating pressures are much higher than those of traditional fluorocarbon-based systems.

[0005] Non-flammable refrigerant mixtures containing difluoromethane (R-32) and CO2 have been proposed (see Adams et al. (J. Chem. Eng. Data 16 (1971) 146-149) and US 7,238,299 B, the contents of which are incorporated herein by reference in their entirety). Such non-flammable compositions may contain up to about 60% by weight of R-32.

[0006] However, such a binary refrigerant composition, although nonflammable as blended, is still considered flammable according to ASHRAE Standard 34 (2019). This is because the mixture is nonazeotropic. ASHRAE Standard 34 requires that the results of a series of vapor leak experiments at temperatures ranging from -40°C to 60°C be considered to identify whether a leak could produce a composition more flammable than the "as blended" composition. When this is performed on a nonflammable binary mixture of R-32 with CO2, a vapor leak at -40°C results in the production of a flammable composition because the more volatile CO2 is preferentially removed from the system, causing fractionation of the remaining material, which consequently contains more than 60% R-32.

[0007] It is therefore desirable to identify refrigerant compositions that address these issues, preferably while retaining the non-flammability of pure CO. Such compositions should also preferably have a low GWP. In particular, a GWP of about 150 or less is required under the European Union's F-gas regulations for certain applications, such as air conditioning systems in passenger vehicles or freestanding refrigeration appliances. DISCLOSURE OF THE INVENTION

[0008] The present invention addresses these and other deficiencies, and the needs described above, by providing a composition comprising carbon dioxide (CO2, R-744), difluoromethane (R-32), and a third component selected from 1,1,1,2-tetrafluoroethane (R-134a), trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)), 2,3,3,3-tetrafluoropropene (R-1234yf), 1,1,1,2,3,3,3-heptafluoropropane (R-227ea), and mixtures thereof.

[0009] Such compositions are hereinafter referred to as compositions of the invention.

[0010] The inventors have discovered that relatively small amounts of other components (especially R-134a) can be added to CO2 and R-32 to ensure that the resulting mixture does not fractionate into a flammable composition when analyzed according to the ASHRAE Standard 34 protocol. Additionally, small amounts of flammable species (e.g., R-1132a) can also be added to the mixtures of the present invention without producing a flammable composition.

[0011] The compositions of the present invention are believed to be particularly useful in heat transfer systems (e.g., refrigeration, air conditioning, and heat pump systems) that utilize a transcritical refrigeration cycle. The basic transcritical cycle consists of the following steps: (a) Vaporization of a liquid refrigerant at low pressure to remove heat from a low-temperature source fluid (such as air), (b) Compression of the resulting refrigerant vapor in a compressor to produce a hot high-pressure gas; (c) Cooling of a high pressure gas by heat exchange with a sink fluid at a temperature higher than the source to produce a cooler, denser refrigerant gas at high pressure. This gas is said to be a "supercritical" fluid because it is above its critical temperature; and (d) Expansion of the supercritical fluid through an expansion valve or other restriction device to produce a two-phase mixture of liquid refrigerant with vaporized refrigerant vapor at low pressure, which mixture is then fed back to the evaporator stage (a) to complete the cycle.

[0012] Optionally, in such a cycle, an internal heat exchange process occurs between the warm high-pressure gas leaving the gas cooler and the cold vapor flowing from the evaporator to the compressor. This process takes place in an "internal heat exchanger" ("IHX") and has the effect of increasing the cooling capacity and efficiency of the cycle.

[0013] Advantageously, such a transcritical refrigeration cycle may also include a liquid accumulator located after the evaporator (and before the IHX, if one is used), which serves to maintain an excess charge of refrigerant when the external ambient temperature is such that the gas cooler pressure is reduced.

[0014] The compositions of the present invention have also been found to be suitable for use in such cycles, whether or not they incorporate IHX or accumulator features.

[0015] The compositions of the present invention will now be described in detail.

[0016] According to the present invention, there is provided a composition comprising CO2, R-32, and a third component selected from 1,1,1,2-tetrafluoroethane (R-134a), trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)), 2,3,3,3-tetrafluoropropene (R-1234yf), 1,1,1,2,3,3,3-heptafluoropropane (R-227ea), and mixtures thereof.

[0017] In one embodiment of the invention, the third component is R-134a and one or more of R-1234yf, R-1234ze(E), and R-227ea.

[0018] In another aspect of the invention, the third component is R-134a, with the proviso that the composition does not include 86%±1% by weight CO2, 7%±1% by weight R-32, and 7%±1% by weight R-134a.

[0019] In a further aspect of the invention, the third component is one or more of R-1234yf or R-1234ze(E).

[0020] In yet another embodiment of the invention, the third component is one or more of R-1234yf, R-1234ze(E), and R-227ea.

[0021] Typically, the compositions of the present invention comprise about 62 or about 65 to about 98 wt. % CO2, for example, about 69 or about 71 to about 97 wt. %, for example, about 74 or about 77 to about 96 wt. % or about 81 to about 96 wt. %, optionally about 81 or about 84 to about 95 wt. % CO2.

[0022] Typically, the compositions of the present invention comprise from about 1 to about 25 wt. % R-32, for example, from about 2 to about 22 wt. %, for example, from about 3 to about 19 wt. %, optionally from about 4 wt. % to about 15 or about 13 wt. % or from about 5 wt. % to about 11 wt. % R-32.

[0023] Advantageously, the compositions of the present invention comprise from about 1 to about 20% by weight, for example, from about 2 or from about 3 to about 15% by weight, for example, from about 4 to about 13% by weight, optionally from about 5 to about 11% by weight, of the third component.

[0024] In one embodiment, the compositions of the present invention comprise, and optionally consist essentially of, about 65 to about 95 wt. % CO2, about 5 to about 15 wt. % R-32, and about 2 to about 20 wt. % R-134a.

[0025] In such compositions, CO2 is preferably present in an amount of about 70 to about 91 wt%, R-32 is present in an amount of about 6 to about 14 wt%, and R-134a is present in an amount of about 3 to about 16 wt%. For example, in such compositions, CO2 is present in an amount of about 72 to about 88 wt%, R-32 is present in an amount of about 8 to about 13 wt%, and R-134a is present in an amount of about 4 to about 15 wt%.

[0026] The compositions of the present invention may further comprise 1,1-difluoroethylene (R-1132a).

[0027] When present, the compositions of the present invention comprise from about 1 to about 20% by weight, such as from about 2 to about 15% by weight, such as from about 3 to about 12% by weight, or from about 4 or about 5 to about 10% by weight of R-1132a.

[0028] The compositions of the present invention typically do not contain 1,1,2-trifluoroethylene (R-1123). Various refrigerant compositions containing R-1123 are known in the art. One advantage of using R-1123 in such compositions is that it provides similar performance to R-32 while at the same time having negligible GWP, but it can only be safely used as a diluted component in many refrigerant compositions. It is believed that the inclusion of R-1123 in the compositions of the present invention may cause problems with the stability of the composition and therefore lead to safety concerns regarding the use of such compositions.

[0029] Furthermore, during the development process, the inventors have found that including R-1123 in the compositions of the present invention reduces the energy efficiency of the compositions, while providing similar performance compared to using an equivalent molar amount of R-32. Considering the overall environmental impact of systems using these compositions (which is a combination of the effects of refrigerant leakage ("direct emissions" of greenhouse gases) and the energy efficiency of refrigerants that lead to CO2 emissions from fuel or energy use ("indirect emissions" of greenhouse gases)), the slight reduction in GWP that can be obtained from the use of R-1123 is more than offset by the reduced energy efficiency. Therefore, R-1123 is preferably not included in the compositions of the present invention.

[0030] Thus, in one embodiment, the compositions of the present invention are substantially free of R-1123. For example, the compositions of the present invention do not contain readily detectable R-1123. In a preferred embodiment, such compositions are free of R-1123.

[0031] In one embodiment, the compositions of the present invention contain less than 80% by weight of CO2. For example, when a composition of the present invention contains 1 to 15% by weight of R-32, 1 to 15% by weight of R-227ea, and 5 to 75% by weight of either R-1234yf or R-1234ze (e.g., trans-R-1234ze), the composition does not contain 80% by weight of CO2. Preferably, such compositions contain more than 80% by weight of CO2, e.g., more than 81 or 82% by weight of CO2.

[0032] In one embodiment, the composition of the present invention consists essentially of the listed components. The term "consisting essentially of" means that the composition of the present invention is substantially free of other components, particularly additional (hydro)(fluoro) compounds (e.g., (hydro)(fluoro)alkanes or (hydro)(fluoro)alkenes) that are known to be used in heat transfer compositions. The term "consisting of" is included in the meaning of "consisting essentially of."

[0033] In one embodiment, the compositions of the present invention are substantially free of any components (other than those specified) that have heat transfer properties. For example, the compositions of the present invention may be substantially free of any other hydrofluorocarbon compounds.

[0034] "Substantially no" and "substantially free of" include the meaning that the compositions of the present invention contain no more than 0.5% by weight of the recited ingredient, based on the total weight of the composition, preferably no more than 0.4%, 0.3%, 0.2%, or 0.1%.

[0035] As used herein, all percentage amounts referred to for compositions herein, including the claims, are by weight based on the total weight of the composition, unless otherwise specified.

[0036] The term "about" when used in connection with numerical values of component amounts in weight percent includes ±0.5 weight percent, for example ±0.2 weight percent.

[0037] For the avoidance of doubt, it is to be understood that the upper and lower limits set forth in the ranges of amounts of ingredients in the compositions of the invention described herein can be interchanged in any manner so long as the resulting range falls within the broadest scope of the invention.

[0038] The compositions of the present invention have an ozone depletion potential of zero.

[0039] Typically, the compositions of the present invention have a global warming potential (GWP) of less than about 300, such as less than about 240, for example less than about 200, for example less than about 160 or less than about 150, preferably less than about 145.

[0040] Advantageously, the compositions of the present invention exhibit reduced flammability hazards when compared to R-1132a.

[0041] Flammability may be determined in accordance with ASHRAE Standard 34 (e.g., ASHRAE Standard 34:2019), the entire contents of which are incorporated herein by reference.

[0042] In one embodiment, the composition has one or more of: (a) a higher lower flammability limit; (b) a higher ignition energy; (c) a higher autoignition temperature; or (d) a lower burn rate compared to R-1132a alone.

[0043] Preferably, the compositions of the present invention have reduced flammability compared to R-1132a in one or more of the following: lower flammability limit at 23°C, lower flammability limit at 60°C, width of flammable range at 23°C or 60°C, autoignition temperature (thermal decomposition temperature), minimum ignition energy in dry air, or burning rate. The flammability limit and burning rate are determined according to the method specified in ASHRAE-34, and the autoignition temperature is determined in a 500 ml glass flask according to the method of ASTM E659-78.

[0044] In preferred embodiments, the compositions of the present invention are non-flammable both as formulated and under the separation scenarios of ASHRAE Standard 34:2019. For example, both the compositions of the present invention and preferably their "worst-case formulations for flammability" are non-flammable at a test temperature of 60°C using the ASHRAE-34 method. Advantageously, vapor mixtures in equilibrium with the compositions of the present invention are also non-flammable at any temperature between about -20°C and 60°C.

[0045] In some applications, it may not be necessary to classify a formulation as nonflammable by the ASHRAE-34 method. For example, if it is physically impossible to leak the charge of a cooling system into the environment and create a flammable mixture, it is possible to develop a fluid whose flammability limit in air is sufficiently reduced to make it safe for use in that application. A preferred example of such a scenario is one in which a composition is formulated to be nonflammable, but application of the Standard 34 fractionation method results in the creation of a "worst-case flammable formulation" that is flammable, but the scenario is not considered relevant to the application. Similarly, a preferred composition would be one that is classified by the ISO 817 classification standard as nonflammable as formulated but weakly flammable under fractionation (flammability class 1 / 2L).

[0046] The compositions of the present invention are believed to exhibit an entirely unexpected combination of low flammability / non-flammability, low GWP, improved lubricant compatibility, and improved performance characteristics when used in refrigeration systems, particularly air conditioning systems, some of which are described in more detail below.

[0047] Typically, the compositions of the present invention have a critical temperature that is about equal to or higher than the critical temperature of CO2, for example, greater than about 40°C.

[0048] Advantageously, the compositions of the present invention have a volumetric cooling capacity that is within at least about 75%, such as within at least about 80%, such as within at least about 90% of the volumetric cooling capacity of CO2.

[0049] Advantageously, the compositions of the present invention have a coefficient of performance (COP) that is about equal to or higher than that of CO2.

[0050] Typically, the compositions of the present invention have operating pressures in gas coolers and evaporators that are lower than the operating pressure of CO. Reducing the operating pressure can benefit the efficiency and durability of the compressor, for example, by reducing the absolute pressure differential across the compressor (which reduces the load on the mechanical bearings). Furthermore, this reduction in pressure differential can benefit the volumetric efficiency of the compressor.

[0051] Advantageously, the compositions of the present invention have a temperature glide in the evaporator (defined as the difference between the dew point and the inlet temperature) of less than about 12 K, for example less than about 10 K, for example less than about 8 K, preferably less than about 6 K.

[0052] The compositions of the present invention are typically suitable for use in existing designs of equipment and are compatible with all types of lubricants currently used with established HFC refrigerants and R-744. They may optionally be stabilized or compatibilized with mineral oils by the use of appropriate additives.

[0053] Preferably, the lubricant is selected from mineral oil, silicone oil, polyalkylbenzene (PAB), polyol ester (POE), polyalkylene glycol (PAG), polyalkylene glycol ester (PAG ester), polyvinyl ether (PVE), poly(alpha-olefin) and combinations thereof, preferably, the lubricant is selected from PAG, POE, PVE and combinations thereof.

[0054] Compositions comprising a lubricant and a composition of the present invention typically exhibit improved miscibility compared to CO2 and the same lubricant.

[0055] Advantageously, the stabilizer is selected from diene-based compounds, phosphates, phenolic compounds and epoxides, and mixtures thereof.

[0056] In another aspect of the present invention, there is provided the use of the composition of the present invention as a working fluid in a heat transfer system.

[0057] Typically, the heat transfer system is a refrigeration, heat pump or air conditioning system.

[0058] Preferably, the refrigeration system comprises a commercial refrigeration system (such as a supermarket display refrigeration system, a beverage cooler refrigeration system, a warehouse refrigeration system or a cold room refrigeration system) or a transport refrigeration system (e.g. a refrigeration system mounted in a refrigerated shipping container or a refrigeration system mounted in a vehicle).

[0059] Conveniently, the heat pump system comprises a water heater heat pump system.

[0060] Preferably, the air conditioning system comprises a mobile or transport air conditioning system, such as an air conditioning system for a bus, car, train or truck.

[0061] Advantageously, the heat transfer (eg, refrigeration, heat pump and / or air conditioning) system defined above operates as a transcritical heat transfer system during at least part of the year.

[0062] In some applications of transcritical cycle technology, the vapor compression cycle used is a single compression cycle, as is typical in mobile air conditioning applications. In other applications, gas compression is performed in two stages, allowing efficient operation over large temperature differences between the heat source and heat sink. The compositions of the present invention are believed to be suitable for use in single and dual compression stage cycles.

[0063] One aspect of the present invention provides the use of the compositions of the present invention as a replacement for existing working fluids in heat transfer devices, including new heat transfer devices designed to meet the same application requirements.

[0064] Advantageously, the existing working fluid is R-410A or R-407C.

[0065] In another aspect of the present invention, there is provided a heat transfer device comprising the composition of the present invention.

[0066] Preferably, the heat transfer device is a transcritical heat transfer device, such as a transcritical refrigeration, heat pump or air conditioning device.

[0067] Optionally, the transcritical heat transfer device comprises an internal heat exchanger (IHX) system.

[0068] The transcritical heat transfer device may also include a liquid accumulator located after the evaporator or, if an IHX is present, between the evaporator and the IHX.

[0069] According to another aspect of the present invention, there is provided a method of producing heat comprising condensing or cooling a composition of the present invention in the vicinity of a body to be heated.

[0070] According to another aspect of the present invention, there is provided a method of producing cooling comprising evaporating a composition of the present invention in the vicinity of a body to be cooled.

[0071] All chemicals described herein are commercially available, for example, fluorochemicals can be purchased from Apollo Scientific (UK).

[0072] The compositions of the present invention can be prepared by simply mixing CO2, R-32, and a third component (and optional components, such as R-1132a and / or lubricants) in the desired ratios. The composition can then be added to a heat transfer device or used in any other manner described herein.

[0073] The invention is illustrated by the following non-limiting examples. [Example]

[0074] The vapor-liquid equilibrium behavior of CO2 with R-32 and R-134a at specific temperatures has been described in the academic literature. The vapor-liquid equilibrium behavior of CO2 with R134a and R-1132a with CO2, R-32, and R-134a was experimentally studied over the temperature range of -40 °C to +70 °C using a constant-volume equilibrium apparatus. The resulting data were used to fit binary interaction parameters for each binary pair for use in the NIST REFPROP9.1 and REFLEAK5.1 software codes. The measurement principle for this experimental work was the determination of vapor pressures for a series of known compositions over a range of temperatures, followed by regression to a thermodynamic model to minimize the difference between the calculated and observed pressures across the data set.

[0075] A series of ternary compositions of CO2 / R-32 / R-134a were subsequently subjected to fractional evaluation using the REFPROP property library for modeling refrigerant behavior, following the outline provided in ASHRAE Standard 34. The "worst-case scenario" was an isothermal vapor leak at -40°C from a cylinder initially filled with 90% of the maximum allowable charge of material. Leakage was modeled to simulate a 95% loss of initial mass. The maximum allowable charge was determined using calculated liquid densities at temperatures specified in the standard to model fluids with critical temperatures below 54.4°C.

[0076] FIG. 1 shows the maximum content of R-32 that can be included in the composition without fractionation resulting in a flammable composition as a function of the R-134a content (0-15 wt %).

[0077] Standard refrigeration cycle modeling techniques were then used to estimate the performance of selected compositions of the present invention with R-134a in the range of about 4 to about 14 wt. %. The R-32 content was selected according to Figure 1 to result in a composition that remained non-flammable under fractionation.

[0078] The cycle modeled was a transcritical cycle using an internal heat exchanger (IHX) to exchange heat between the gas exiting the gas cooler and the low pressure vapor exiting the evaporator.

[0079] The performance of CO2 was also calculated as a comparative example. The cycle conditions were selected to ensure that CO2 operated as a transcritical refrigerant in the cycle. The gas cooler pressure in the cycle was optimized to maximize the coefficient of performance (COP) of the mixture.

[0080] The following conditions were assumed for modeling purposes: [Table 1]

[0081] The results are shown in Table 2.

[0082] Performance data shows that the modeled ternary composition has superior energy efficiency and reduced operating pressure compared to CO. Additionally, the GWP of the composition is less than about 300.

[0083] Furthermore, it is found that adding more than about 15 wt. % R-134a to these compositions is undesirable, since the temperature glide in the evaporator will exceed 11 K.

[0084] The ternary compositions of the present invention can be further enhanced by the addition of R-1132a, for example, by replacing a portion of the CO2 content with R-1132a so that the R-1132a content is between 1% and 15% by weight without producing a flammable composition during fractionation. The addition of R-1132a reduces the compressor discharge temperature and reduces temperature glide in the evaporator. Modeling results for selected R-1132a-containing compositions are shown in Table 3 below. [Table 2] [Table 3]

[0085] The present invention includes the following aspects. [Aspect 1] (a) Carbon dioxide (R-744, CO2) and (b) difluoromethane (R-32), (c) a third component selected from 1,1,1,2-tetrafluoroethane (R-134a), trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)), 2,3,3,3-tetrafluoropropene (R-1234yf), 1,1,1,2,3,3,3-heptafluoropropane (R-227ea), and mixtures thereof. [Aspect 2] 2. The composition of embodiment 1, wherein the third component is R-134a, and one or more of R-1234yf, R-1234ze(E), and R-227ea. [Aspect 3] 2. The composition of embodiment 1, wherein the third component is R-134a, with the proviso that the composition does not comprise 86%±1% by weight of CO2, 7%±1% by weight of R-32, and 7%±1% by weight of R-134a. [Aspect 4] 2. The composition of embodiment 1, wherein the third component is one or more of R-1234yf or R-1234ze(E). [Aspect 5] 2. The composition of embodiment 1, wherein the third component is one or more of R-1234yf, R-1234ze(E), and R-227ea. [Aspect 6] 6. The composition of any one of the preceding embodiments, comprising about 62 or about 65 to about 98 wt. % CO2, e.g., about 69 or about 71 to about 97 wt. %, e.g., about 74 or about 77 to about 96 wt. % or about 81 to about 96 wt. %, optionally about 81 or about 84 to about 95 wt. % CO2. [Aspect 7] 10. The composition of any one of the preceding embodiments, comprising about 1 to about 25 wt. %, e.g., about 2 to about 22 wt. %, e.g., about 3 to about 19 wt. %, optionally about 4 wt. % to about 15 or about 13 wt. %, or about 5 wt. % to about 11 wt. % R-32. [Aspect 8] The composition of any one of the preceding aspects, comprising about 1 to about 20 wt. % of the third component, e.g., about 2 or about 3 to about 15 wt. %, e.g., about 4 to about 13 wt. %, optionally about 5 to about 11 wt. %. [Aspect 9] 4. The composition of embodiment 3, comprising, optionally consisting essentially of, about 65 to about 95 wt. % CO2, about 5 to about 15 wt. % R-32, and about 2 to about 20 wt. % R-134a. [Aspect 10] 10. The composition of claim 9, wherein the CO2 is present in an amount of about 70 to about 91 wt. %, the R-32 is present in an amount of about 6 to about 14 wt. %, and the R-134a is present in an amount of about 3 to about 16 wt. %, and preferably, the CO2 is present in an amount of about 72 to about 88 wt. %, the R-32 is present in an amount of about 8 to about 13 wt. %, and the R-134a is present in an amount of about 4 to about 15 wt. %. [Aspect 11] The composition of any one of the preceding aspects, wherein the composition further comprises 1,1-difluoroethylene (R-1132a). [Aspect 12] 12. The composition of claim 11, comprising about 1 to about 20 wt. %, e.g., about 2 to about 15 wt. %, e.g., about 3 to about 12 wt. %, or about 4 or about 5 to about 10 wt. % R-1132a. [Aspect 13] 10. The composition of any one of the preceding aspects, wherein the composition is substantially free of 1,1,2-trifluoroethylene (R-1123). [Aspect 14] 10. The composition of any preceding aspect, consisting essentially of the recited components. [Aspect 15]

[0023] The composition of any one of the preceding aspects, wherein the composition, when formulated, is non-flammable, e.g., the composition is not flammable as determined according to ASHRAE Standard 34:2019. [Aspect 16] 2. The composition of any one of the preceding embodiments, having a Global Warming Potential (GWP) of less than about 300, such as less than about 240, such as less than about 200, such as less than about 160 or less than about 150, preferably less than about 145. [Aspect 17]

[0023] The composition of any one of the preceding embodiments, having a critical temperature about equal to or higher than the critical temperature of CO2, e.g., greater than about 40°C. [Aspect 18] 10. The composition of any one of the preceding embodiments, wherein the composition has a volumetric cooling capacity that is at least within about 75%, e.g., at least within about 80%, e.g., at least within about 90%, of the volumetric cooling capacity of CO2. [Aspect 19]

[0023] The composition of any one of the preceding aspects, wherein the composition has a coefficient of performance (COP) that is about equal to or higher than the COP of CO. [Aspect 20] 10. The composition of any one of the preceding embodiments, wherein the composition has an operating pressure in a gas cooler or evaporator that is lower than an operating pressure of CO. [Aspect 21] The composition of any one of the preceding embodiments, wherein the composition has a temperature glide in an evaporator or condenser that is less than about 12 K, such as less than about 10 K, for example, less than about 8 K, preferably less than about 6 K. [Aspect 22] 10. A composition comprising a lubricant and the composition of any one of the preceding aspects, wherein preferably the lubricant is selected from mineral oil, silicone oil, polyalkylbenzene (PAB), polyol ester (POE), polyalkylene glycol (PAG), polyalkylene glycol ester (PAG ester), polyvinyl ether (PVE), poly(alpha-olefin), and combinations thereof. [Aspect 23] 23. The composition of embodiment 22, wherein the lubricant is selected from PAG, POE, PVE, and combinations thereof. [Aspect 24] 13. Use of the composition according to any one of the preceding aspects as a working fluid in a heat transfer system, such as a refrigeration, heat pump or air conditioning system. [Aspect 25] 25. The use according to embodiment 24, wherein the refrigeration system comprises a commercial refrigeration system, such as a supermarket display refrigeration system, a beverage cooler refrigeration system, a warehouse refrigeration system or a cold room refrigeration system. [Aspect 26] 25. The use according to embodiment 24, wherein the refrigeration system comprises a transport refrigeration system, such as a refrigeration system mounted on a refrigerated shipping container or a refrigeration system mounted on a vehicle. [Aspect 27] 25. The use of embodiment 24, wherein the heat pump system comprises a water heater heat pump system. [Aspect 28] 25. The use according to embodiment 24, wherein the air conditioning system comprises a mobile or transport air conditioning system, such as an air conditioning system for a bus, car, train or truck. [Aspect 29] 29. The use of any one of aspects 24 to 28, wherein the heat transfer system operates as a transcritical heat transfer system for at least part of the year. [Aspect 30] A heat transfer device comprising the composition of any one of embodiments 1 to 23. [Aspect 31] 31. The heat transfer device of embodiment 30, wherein the heat transfer device is a transcritical heat transfer device, such as a transcritical refrigeration, heat pump, or air conditioner. [Aspect 32] 24. Use of the composition of any one of aspects 1-23 as a replacement for an existing working fluid in a heat transfer system. [Aspect 33] 33. The use of aspect 32, wherein the existing working fluid is R-410A or R-407C. [Aspect 34] A method for cooling an article, the method comprising condensing the composition of any one of embodiments 1-23 and then evaporating the composition in the vicinity of the article to be cooled. [Aspect 35] A method for heating an article, the method comprising: condensing the composition of any one of embodiments 1-23 near the article to be heated; and then evaporating the composition. [Brief explanation of the drawings]

[0086] [Figure 1] 1 shows the maximum content of R-32 that can be included in the composition without fractionation resulting in a flammable composition as a function of the R-134a content (0-15 wt%).

Claims

1. (a) Carbon dioxide (R-744, CO ２ )and, (b) difluoromethane (R-32), (c) a third component selected from 1,1,1,2-tetrafluoroethane (R-134a), trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)), 2,3,3,3-tetrafluoropropene (R-1234yf), 1,1,1,2,3,3,3-heptafluoropropane (R-227ea), and mixtures thereof.

2. 10. The composition of claim 1, wherein the third component is R-134a and one or more of R-1234yf, R-1234ze(E), and R-227ea.

3. the third component is R-134a, provided that the composition contains 86% by weight ±1% by weight of CO ２ 7% by weight ±1% by weight of R-32 and 7% by weight ±1% by weight of R-134a.

4. 10. The composition of claim 1, wherein the third component is one or more of R-1234yf or R-1234ze(E).

5. 10. The composition of claim 1, wherein the third component is one or more of R-1234yf, R-1234ze(E), and R-227ea.

6. about 62 or about 65 to about 98 wt. %, for example, about 69 or about 71 to about 97 wt. %, for example, about 74 or about 77 to about 96 wt. % or about 81 to about 96 wt. %, optionally about 81 or about 84 to about 95 wt. % CO ２ 10. The composition of any one of the preceding claims, comprising:

7. 10. The composition of any one of the preceding claims, comprising from about 1 to about 25 wt. %, e.g., from about 2 to about 22 wt. %, e.g., from about 3 to about 19 wt. %, optionally from about 4 wt. % to about 15 or about 13 wt. %, or from about 5 wt. % to about 11 wt. % of R-32.

8. 10. The composition of any one of the preceding claims, comprising from about 1 to about 20% by weight of the third component, such as from about 2 or about 3 to about 15% by weight, for example from about 4 to about 13% by weight, optionally from about 5 to about 11% by weight.

9. About 65 to about 95 wt. % CO ２ 4. The composition of claim 3, comprising, and optionally consisting essentially of, about 5 to about 15 wt. % R-32 and about 2 to about 20 wt. % R-134a.

10. The CO ２ is present in an amount of about 70 to about 91 wt %, the R-32 is present in an amount of about 6 to about 14 wt %, the R-134a is present in an amount of about 3 to about 16 wt %, and preferably ２ is present in an amount of about 72 to about 88 wt %, said R-32 is present in an amount of about 8 to about 13 wt %, and said R-134a is present in an amount of about 4 to about 15 wt %.

11. 10. The composition of any one of the preceding claims, wherein the composition further comprises 1,1-difluoroethylene (R-1132a).

12. 12. The composition of claim 11, comprising about 1 to about 20 wt. %, e.g., about 2 to about 15 wt. %, e.g., about 3 to about 12 wt. %, or about 4 or about 5 to about 10 wt. % R-1132a.

13. 10. The composition of any one of the preceding claims, wherein the composition is substantially free of 1,1,2-trifluoroethylene (R-1123).

14. 10. A composition according to any preceding claim, consisting essentially of the components set forth.

15. 10. The composition of any one of the preceding claims, wherein the composition when formulated is non-flammable, e.g., the composition is not flammable as determined according to ASHRAE Standard 34:2019.

16. 10. The composition of any one of the preceding claims, having a Global Warming Potential (GWP) of less than about 300, such as less than about 240, for example less than about 200, such as less than about 160 or less than about 150, preferably less than about 145.

17. CO ２ 10. The composition of claim 9, wherein the critical temperature is about equal to or higher than the critical temperature of 0.15 wt %, for example higher than about 40°C.

18. The composition comprises CO ２ 10. The composition of any one of the preceding claims, having a volumetric cooling capacity that is at least within about 75%, such as at least within about 80%, such as at least within about 90% of the volumetric cooling capacity of

19. The composition comprises CO ２ 10. The composition of any one of the preceding claims, having a coefficient of performance (COP) about equal to or higher than

20. The composition comprises CO ２ 10. The composition of claim 9, wherein the composition has an operating pressure in the gas cooler or evaporator lower than the operating pressure of

21. 10. The composition of any one of the preceding claims, wherein the composition has a temperature glide in an evaporator or condenser that is less than about 12K, such as less than about 10K, for example less than about 8K, preferably less than about 6K.

22. 10. A composition comprising a lubricant and the composition of any one of the preceding claims, preferably wherein the lubricant is selected from mineral oil, silicone oil, polyalkylbenzene (PAB), polyol ester (POE), polyalkylene glycol (PAG), polyalkylene glycol ester (PAG ester), polyvinyl ether (PVE), poly(alpha-olefin), and combinations thereof.

23. 23. The composition of claim 22, wherein the lubricant is selected from PAG, POE, PVE, and combinations thereof.

24. 10. Use of a composition according to any one of the preceding claims as a working fluid in a heat transfer system, such as a refrigeration, heat pump or air conditioning system.

25. 25. The use of claim 24, wherein the refrigeration system comprises a commercial refrigeration system, such as a supermarket display refrigeration system, a beverage cooler refrigeration system, a warehouse refrigeration system or a cold room refrigeration system.

26. 25. The use of claim 24, wherein the refrigeration system comprises a transport refrigeration system, such as a refrigeration system mounted on a refrigerated shipping container or a refrigeration system mounted on a vehicle.

27. 25. The use of claim 24, wherein the heat pump system comprises a water heater heat pump system.

28. 25. The use according to claim 24, wherein the air conditioning system comprises a mobile or transport air conditioning system, such as an air conditioning system for a bus, car, train or truck.

29. Use according to any one of claims 24 to 28, wherein the heat transfer system operates as a transcritical heat transfer system for at least part of the year.

30. A heat transfer device comprising the composition of any one of claims 1 to 23.

31. 31. The heat transfer device of claim 30, wherein the heat transfer device is a transcritical heat transfer device, such as a transcritical refrigeration, heat pump, or air conditioner.

32. Use of a composition according to any one of claims 1 to 23 as a replacement for an existing working fluid in a heat transfer system.

33. The use according to claim 32, wherein the existing working fluid is R-410A or R-407C.

34. 24. A method for cooling an article, comprising condensing a composition according to any one of claims 1 to 23 and then evaporating the composition in the vicinity of the article to be cooled.

35. 24. A method for heating an article, comprising condensing a composition according to any one of claims 1 to 23 in the vicinity of the article to be heated and thereafter evaporating the composition.

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