Composition

Abstract

The present 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.

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, cars 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 where non-flammability of the refrigerant is required. 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. 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 US7238299B, 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 non-flammable when blended, is still considered flammable according to ASHRAE Standard 34 (2019). This is because the mixture is non-azeotropic. ASHRAE Standard 34 requires that the results of a series of vapor leakage experiments at temperatures ranging from -40°C to 60°C be considered to identify whether a leakage could produce a composition that is more flammable than the "as blended" composition. If this is done for a non-flammable binary mixture of R-32 with CO2, a vapor leakage at -40°C would result in the production of a flammable composition because the more volatile CO2 would be preferentially removed from the system, causing fractionation of the remaining material, which would then contain 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 CO2. 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 cooling appliances. DISCLOSURE OF THEINVENTION

[0008] The present invention addresses these and other deficiencies, as well as 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 found that relatively small amounts of other components, particularly R-134a, may 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) may 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) The evaporation of a liquid refrigerant at low pressure to remove heat from a low-temperature source fluid (such as air); (b) compressing 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 higher temperature 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 the 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 steam 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). This serves to hold 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% CO2 by weight, 7% ± 1% R-32 by weight, and 7% ± 1% R-134a by weight.

[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 invention comprise from about 62 or about 65 to about 98% by weight CO2, such as from about 69 or about 71 to about 97% by weight, such as from about 74 or about 77 to about 96% by weight or from about 81 to about 96% by weight, optionally from about 81 or about 84 to about 95% by weight CO2.

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

[0023] Advantageously, the compositions of the present invention comprise from about 1 to about 20% by weight, 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 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, preferably, CO2 is present in an amount of about 70 to about 91% by weight, R-32 is present in an amount of about 6 to about 14% by weight, and R-134a is present in an amount of about 3 to about 16% by weight. For example, in such compositions, CO2 is present in an amount of about 72 to about 88% by weight, R-32 is present in an amount of about 8 to about 13% by weight, and R-134a is present in an amount of about 4 to about 15% by weight.

[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 composition of the present invention typically does 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 capacity to R-32 and at the same time has 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 composition of the present invention may cause problems with the stability of the composition, thus leading to safety concerns regarding the use of such compositions.

[0029] Furthermore, in the course of development, 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.When considering the overall environmental impact of the systems using these compositions (which is a combination of the effect of refrigerant leakage (greenhouse gas "direct emission") and the energy efficiency of the refrigerant that leads to CO2 emissions from fuel or energy use (greenhouse gas "indirect emission")), the slight reduction in GWP that can be obtained from the use of R-1123 is more than offset by the reduction in energy efficiency.Therefore, R-1123 is preferably not included in the compositions of the present invention.

[0030] Thus, in one embodiment, the composition of the present invention is substantially free of R-1123. For example, the composition of the present invention does not contain easily detectable R-1123. In a preferred embodiment, such a composition does not contain R-1123.

[0031] In one embodiment, the composition of the present invention does not contain 80% by weight of CO2. For example, when the composition of the present invention contains 1-15% by weight of R-32, 1-15% by weight of R-227ea, and 5-75% 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 a composition contains 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 recited components. The term "consisting essentially of" refers to the composition of the present invention being 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. Ma 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, preferably no more than 0.4%, 0.3%, 0.2%, or 0.1% of the recited component based on the total weight of the composition.

[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 the meaning of ±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 the 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, such as less than about 200, such as 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 are less flammable than R-1132a in one or more of the lower flammability limit at 23° C., the lower flammability limit at 60° C., the width of the flammable range at 23° C. or 60° C., the spontaneous ignition temperature (thermal decomposition temperature), the minimum ignition energy in dry air, or the burning rate. The flammability limit and burning rate are determined according to the method specified in ASHRAE-34, and the spontaneous ignition temperature is determined in a 500 ml glass flask by the method of ASTM E659-78.

[0044] In a preferred embodiment, 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, mixtures of vapors 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 non-flammable by the ASHRAE-34 method. For example, if it is physically impossible to leak a cooling system charge 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 the application. A preferred example of such a scenario is one in which a composition is formulated to be non-flammable, but application of the Standard 34 fractionation method results in the creation of a "worst case formulation for flammability" that is flammable, but the scenario is not considered relevant for the application. Similarly, a preferred composition is one that is classified by the ISO 817 classification criteria as non-flammable when formulated but weakly flammable under fractionation (flammability class 1 / 2L).

[0046] The compositions of the present invention are believed to exhibit a completely unexpected combination of low flammability / non-flammability, low GWP, improved lubricant compatibility and improved performance properties 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, e.g., greater than about 40°C.

[0048] Advantageously, the compositions of the present invention have 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 CO2.

[0049] Advantageously, the compositions of the present invention have a coefficient of performance (COP) that is about equal to or higher than the COP 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 CO2. The reduction in 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 machine's 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 (defined as the difference between the dew point and the inlet temperature) in the evaporator that is less than about 12K, such as less than about 10K, for example less than about 8K, preferably less than about 6K.

[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 in use 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 the 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 invention there is provided the use of the composition of the 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 cooling system comprises a commercial cooling system (such as a supermarket display cooling system, a beverage cooler cooling system, a warehouse cooling system or a cold room cooling system) or a transportation cooling system (e.g. a cooling system mounted in a refrigerated shipping container or a cooling 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 transportation 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 is operated as a transcritical heat transfer system during at least a portion 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 temperatures. 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 invention provides for the use of the compositions of the invention as a replacement for existing working fluids in heat transfer devices, such as 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 invention, there is provided a heat transfer device comprising the composition of the invention.

[0066] Preferably the heat transfer device is a transcritical heat transfer device, such as a transcritical cooling, 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 disposed after the evaporator or, if an IHX is present, between the evaporator and the IHX.

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

[0070] According to another aspect of the invention, there is provided a method of producing cooling comprising evaporating a composition of the 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 the CO2, R-32 and the third component (as well as 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. EXAMPLES

[0074] The vapor-liquid equilibrium behavior of CO2 with R-32 and with R-134a at specific temperatures has been described in the academic literature. The vapor-liquid equilibrium behavior of CO2 with R134a, and of 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 data obtained were used to fit binary interaction parameters for each binary pair for use in the NIST REFPROP9.1 and REFLEAK5.1 software codes. The principle of measurement 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 over 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 as outlined in ASHRAE Standard 34. The "worst case scenario" was leakage of isothermal vapor at -40°C from a cylinder initially filled with 90% of the maximum allowable charge of material. Leakage was modeled to simulate a loss of 95% of the 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 content of R-134a (0-15% by weight).

[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 remains 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 CO2. Additionally, the GWP of the composition is less than about 300.

[0083] Furthermore, it is found that adding more than about 15% by weight R-134a to these compositions is undesirable since the temperature glide in the evaporator can 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 such 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 the temperature glide in the evaporator. Modeling results for selected R-1132a-containing compositions are shown in Table 3 below. [Table 2] [Table 3] [Brief description of the drawings]

[0085] [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 content of R-134a (0-15% by weight).

Claims

1. Use of a composition as a replacement for an existing working fluid in a heat transfer system, said composition comprising: (a) 62 to 98% by weight 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; The existing working fluid is R-410A or R-407C; The use, further comprising: said composition further comprising 0.5% by weight or less of 1,1,2-trifluoroethylene (R-1123); or said composition further comprising no R-1123.

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

3. 2. The use of claim 1, wherein the third component is one or more of R-1234yf or R-1234ze(E).

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

5. The composition comprising 69 or 71 to 97% by weight of CO ２ The use according to any one of claims 1 to 4, comprising:

6. The use according to claim 5, wherein the composition comprises 74 or 77-96% by weight of CO 2 .

7. The use according to claim 6, wherein the composition comprises 81 or 84-95% by weight of CO 2 .

8. The use according to any one of claims 1 to 7, wherein the composition comprises 1 to 25% by weight of R-32.

9. The use according to claim 8, wherein the composition comprises 3 to 19% by weight of R-32.

10. The use according to claim 9, wherein the composition comprises from 4% to 15 or 13% by weight of R-32.

11. The use according to claim 10, wherein the composition comprises 5% to 11% by weight of R-32.

12. The use described in any one of claims 1 to 11, wherein the composition comprises 1 to 20 weight % of the third component.

13. The use described in claim 12, wherein the composition contains 2 or 3 to 15 weight % of the third component.

14. The use described in claim 13, wherein the composition contains 5 to 11 weight % of the third component.

15. The composition comprising 65 to 95% by weight of CO ２ %, 5 to 15% by weight of R-32 and 2 to 20% by weight of R-134a.

16. The CO ２ is present in an amount of 70 to 91% by weight, said R-32 is present in an amount of 6 to 14% by weight, and said R-134a is present in an amount of 3 to 16% by weight.

17. The use according to any one of claims 1 to 16, wherein the composition further comprises 1,1-difluoroethylene (R-1132a).

18. The use according to claim 17, wherein the composition comprises 1 to 20% by weight of R-1132a.

19. The use according to claim 18, wherein the composition comprises 2 to 15% by weight of R-1132a.

20. The use according to claim 19, wherein the composition comprises 4 or 5 to 10% by weight of R-1132a.

21. The use of any one of claims 1 to 20, wherein the composition consists essentially of the components listed.

22. The use according to any one of claims 1 to 21, wherein the composition when formulated is non-flammable.

23. The use of any one of claims 1 to 22, wherein the composition has a global warming potential (GWP) of less than 300.

24. The use of claim 23, wherein the composition has a GWP of less than 240.

25. The use of claim 24, wherein the composition has a GWP of less than 200.

26. The composition comprising: ２ 26. The use according to any one of claims 1 to 25, wherein the critical temperature of said compound is equal to or higher than the critical temperature of said compound.

27. The composition comprises CO ２ 27. Use according to any one of claims 1 to 26, having a volumetric cooling capacity which is at least within 75% of the volumetric cooling capacity of 28. The use of claim 27, wherein the composition has a volumetric cooling capacity that is at least 80% or less of the volumetric cooling capacity of CO2.

29. The composition comprises CO ２ 29. The use according to any one of claims 1 to 28, having a coefficient of performance (COP) equal to or higher than 0.1% by weight of ...

30. The composition comprises CO ２ 30. The use according to any one of claims 1 to 29, wherein the operating pressure in the gas cooler or evaporator is lower than the operating pressure of

31. Use according to any one of claims 1 to 30, wherein the composition has a temperature glide in an evaporator or condenser that is less than 12K.

32. The use of claim 31, wherein the composition has a temperature glide in an evaporator or condenser that is less than 8K.

33. The use of any one of claims 1 to 32, wherein the composition further comprises a lubricant, the lubricant being 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.

34. 34. The use of claim 33, wherein the lubricant is selected from PAG, POE, PVE and combinations thereof.

35. The use of any one of claims 1 to 34, wherein the heat transfer system is a cooling, heat pump or air conditioning system.

36. 36. The use of claim 35, wherein the cooling system comprises a commercial cooling system, the commercial cooling system being a supermarket display cooling system, a beverage cooler cooling system, a warehouse cooling system or a cold room cooling system.

37. 36. The use of claim 35, wherein the cooling system comprises a transport cooling system, the transport cooling system being a cooling system mounted on a refrigerated shipping container or a cooling system mounted on a vehicle.

38. 36. The use of claim 35, wherein the heat pump system comprises a water heater heat pump system.

39. 36. The use of claim 35, wherein the air conditioning system comprises a mobile or transport air conditioning system, the mobile or transport air conditioning system being an air conditioning system for a bus, car, train or truck.

40. Use according to any one of claims 35 to 39, wherein the heat transfer system operates as a transcritical heat transfer system for at least a part of the year.

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