COMPOSITIONS

Abstract

According to the present invention, a composition is provided for use as a coolant in a thermal management system of an electric vehicle, wherein the composition comprises: (a) trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)); (b) difluoromethane (R-32); and (c) 1,1-difluoroethane (R-152a).

Description

[0001] COMPOSITIONS

[0002] The present invention reiates to the use of compositions as refrigerants in thermal management systems of electric vehicles, particularly those comprising liquid chiller systems.

[0003] The listing or discussion of a prior-published document or any background in the specification should not necessarily be taken as an acknowledgement that a document or background is part of the state of the art or is common general knowledge.

[0004] In new internal combustion engine (ICE) vehicles, comfort heating of the passenger cabin is typically accomplished via direct heat exchange between waste heat from the combustion engine and passenger air. ICE vehicles also typically include an air- conditioning system, the sole function of which is to provide comfort cooling and dehumidification of air in passenger cabin.

[0005] In contrast, most electric vehicles (EVs, whether purely electric or hybrid vehicles) have no source of waste heat at a temperature high enough to deliver comfort heating of cabin air by direct heat exchange. Although the battery, power electronics and electric motors may act as sources of heat in EVs, they typically yield heat at too low a temperature to be directly used for heating of cabin air. In addition, a considerable amount of battery energy is used for thermal management of the battery itself. As there is no high-temperature waste heat available, using battery energy to provide passenger cabin heating and battery thermal management can significantly reduce EV range in winter conditions.

[0006] To address this, most EV designs have now incorporated heat pumping into the function of air-conditioning and require a refrigeration cycle not just for air-conditioning but to be integrated into the vehicle's "thermal management system", whose function is to move heat into, around or out of the vehicle as necessary to simultaneously maintain passenger comfort, battery thermal condition and component cooling. There are two main design types of thermal management systems of EVs, namely air-to-air and fiuid-to-fluid architectures (hereinafter 'chiller architectures').

[0007] Typical air-to-air architectures comprise heat exchangers where heat transfer occurs predominantly in crossflow, with air flowing perpendicular to one or more rows of refrigerant tubes. By contrast, chiller architectures comprise a refrigeration cycle that is integrated into circuits of hot / cold heat transfer fluid, such as water. The purpose of the refrigeration cycle is to move heat from the cold loop to the hot loop.

[0008] Propane (R-290) has been successfully tested for application in chiller systems. However, propane is considered as a Volatile Organic Chemical (VOC) and a precursor to photochemical smog generation which is environmentally undesirable. In addition, propane's ability to operate in a heat pump cycle will be limited to external temperatures of about -30°C, which is typically insufficient for extremely low temperature winter conditions.

[0009] 1,1-difluoroethane (R-152a) has been proposed for use in chiller architectures. It is relatively low cost, has acceptable Global Warming Potential (GWP) of 124 and is efficient as an air-conditioning refrigerant. However, its flammability (ASHRAE Class 2) precludes its use in direct heat exchange with cabin air; and its normal boiling point is higher than that of R-1234yf, meaning that its performance in heat pump mode will be poor and limited to temperatures above -15°C making it inefficient for cold ambient heat pumps.

[0010] 2,3,3,3-tetrafluoropropene (R-1234yf) is currently used in automobile air-conditioning systems. R-1234yf is weakly flammable (class "2L" as per ASHRAE SSPC34). This degree of flammability has been accepted by the automotive industry following extensive risk assessment processes as sufficiently low to allow safe engineering design to mitigate its hazards. It would be desirable to identify alternative refrigerants that may give better performance in EV thermal management applications while maintaining acceptably low flammability, like that of R-1234yf.

[0011] Refrigerants such as R-454C (R-32 / R-1234yf 21.5% / 78.5%) and R-474A (R-1132(E) / R- 1234yf 23% / 77%) have GWP lower than 150 and a higher vapour pressure than that of R-1234yf. However, they are formulated using R-1234yf. Even though R-1234yf has certain desirable performance characteristics, it has been found to break down rapidly in the environment with 100% molar yield to form trifluoroacetic acid (TFA). TFA is toxic and is very resistant to environmental degradation. The large-scale implementation of R- 1234yf or blends comprising this compound in EV systems would lead to an increase in levels of TFA in groundwater. Therefore, there exists a need for new refrigerants that will generate less TFA on release to the environment than R-1234yf.

[0012] In summary, there is a need to provide alternative refrigerants for use in EV thermal management systems, such as those employing chiller architectures, said refrigerants having improved properties such as iow GWP (so as to reduce the environmental impact of refrigerant leakage), yet possessing acceptable refrigeration performance, flammability characteristics and toxicology in the event of an accidental release into the passenger space.

[0013] The present invention addresses the above and other deficiencies / needs by providing the use of a composition as a refrigerant in a thermal management system of an electric vehicle, wherein the composition comprises trans-l,3,3,3-tetrafluoropropene (R- 1234ze(E)), difluoromethane (R-32) and 1,1-difluoroethane (R-152a).

[0014] The compositions of the invention have been surprisingly found to exhibit similar or improved performance to that of R~1234yf when used in EV thermal management systems, such as those employing chiller architectures. Similarly, the compositions of the invention have been found to exhibit better environmental characteristics compared to propane or R”1234yf. Surprisingly, the compositions of the invention have also been found to exhibit a temperature glide in evaporation or condensation that is close to typical temperature changes of heat transfer fluids (such as water, glycol or fluorinated fluids) used in EV thermal management systems employing chiller architectures. This enables improvements in capacity and energy efficiency of such thermal management systems.

[0015] The compositions of the invention typically contain from about 55 to about 95% by weight R-1234ze(E). Conveniently, the compositions of the invention comprise from about 55 to about 90% by weight R-1234ze(E) or from about 60 to about 95% by weight R-1234ze(E), for example from about 65 to about 93% by weight, such as from about 70 to about 92% by weight, preferably from about 75 to about 90% by weight.

[0016] The compositions of the invention may comprise from about 1 to about 30% by weight R- 32. Conveniently, the compositions comprise from about 2 to about 25% by weight R-32, for example from about 3 to about 25% by weight, such as from about 3 or about 4 to about 22% by weight, preferably from about 5 or 8 to about 20% by weight.

[0017] The compositions of the invention typically contain from about 1 to about 40% by weight R-152a. Conveniently, the compositions comprise from about 1 or about 2 to about 35% by weight R-152a, such as from about 3 to about 25% by weight, for example from about 4 to about 15 or 20% by weight. In one aspect, the compositions contain from about 2 to about 10% by weight R-152a. Thus, the present invention provides a composition comprising from about 55 to about 95% by weight R-1234ze(E), from about 1 to about 30% by weight R-32 and from about

[0018] 1 to about 30% by weight R-152a.

[0019] For exampie, the compositions of the invention may comprise from about 60 to about 95% by weight R-1234ze(E), from about 2 to about 25% by weight R-32 and from about 1 to about 25% by weight R-152a.

[0020] Conveniently, the compositions of the invention comprise from about 65 to about 93% by weight R-1234ze(E), from about 3 to about 25% by weight R-32 and from about 2 to about 20% by weight R-152a.

[0021] Advantageously, the compositions of the invention may comprise from about 70 to about 92% by weight R-1234ze(E), from about 3 to about 22% by weight R-32 and from about

[0022] 2 to about 15% by weight R~152a.

[0023] Preferably, the compositions of the invention comprise from about 75 to about 90% by weight R~1234ze(E), from about 5 to about 20% by weight R-32 and from about 2 to about 10% by weight R-152a.

[0024] Certain preferred compositions of the invention comprise, optionally consist essentially of, from about 80 to about 86% by weight R-1234ze(E), from about 9 to about 15% by weight R-32 and from about 2 to about 8% by weight R-152a or from about 81 to about 85% by weight R-1234ze(E), from about 10 to about 14% by weight R-32 and from about 3 to about 7% by weight R-152a.

[0025] One preferred composition of the invention comprises, optionally consists essentially of, about 83% by weight R-1234ze(E), about 12% by weight R-32 and about 5% by weight R-152a.

[0026] Any of the above-described compositions may further contain one or more compound(s) selected from the group consisting of carbon dioxide (CO2), trans-l,2-difluoroethylene (R- 1132(E), 1,1,1,2-tetrafluoroethane (R-134a), butane (R-600), isobutane (R-600a), propane (R-290), octafluoropropane (R-218), 1,1,1,2,3,3,3-heptafluoropropane (R- 227ea), trifluoroethylene (R-1123), fluoromethane (R-41), 3,3,3-trifluoropropene (R- 1243zf) and / or fluoroethane (R-161), preferably CO2, R-1132(E), R-600a and / or R-290. Typically, the compositions of the invention contain from about 1 to about 15% by weight of the one or more compound(s), such as from about 1 to about 10% by weight, preferably from about 1 to about 5% by weight.

[0027] The compositions of the invention may further comprise 2,3,3,3-tetrafiuoropropene (R- 1234yf), preferably in an amount less than R-1234ze(E). Typically, the R-1234yf is present in an amount of from 0 to about 30, about 40 or about 50 % by weight R-1234yf, preferably from 0 to about 15 or 20% by weight 2,3,3,3-tetrafiuoropropene (R-1234yf), such as from 0 to about 10% by weight, for example from 0 to about 5% by weight or from 0 to about 1% by weight.

[0028] In one embodiment, the compositions of the invention contain substantially no R-1234yf. The exclusion of R-1234yf or its inclusion at iow amounts ensures that the total generation potential of TFA from unit mass of the composition of the invention is significantly lower than that of the same quantity of other refrigerants which are formulated using R-1234yf, at the same time optionally allowing for the compositions of the invention to exploit advantageous properties of R-1234yf.

[0029] In an embodiment, the compositions may consist essentially of the stated components. By the term "consist essentially of", we include the meaning that the compositions of the invention contain substantially no other components, particularly no further (hydro)(fluoro)compounds (e.g. (hydro)(fluoro)alkanes or (hydro)(fluoro)alkenes) known to be used in heat transfer compositions. The term "consist of" is included within the meaning of "consist essentially of".

[0030] In a preferred embodiment, the compositions of the invention comprise substantially no 1,1-difluoroethylene (R-1132a). Preferably, the compositions of the invention comprise no (readily detectable) R-1132a. It has been found that that excluding R-1132a from the compositions of the invention has advantages in terms of flammability and temperature glide. By having (substantially) no R-1132a in the compositions, it is easier to achieve "2L" flammability. It also typically reduces temperature glide, which is an advantage in many heat transfer systems whose heat exchangers are noy designed to allow for presence of any significant glide.

[0031] Advantageously, the compositions of the invention consist essentially of R-1234ze(E), R- 32 and R-152a, wherein the compositions comprise no (readily detectable) R-1132a. Conveniently, the compositions of the invention comprise substantially no trifluoroethyiene (R-1123). Surprisingly, it has been found that such compositions have improved lifetime and chemical stability when used in thermal management systems of EVs.

[0032] In an embodiment, the compositions of the invention are substantially free of any component that has heat transfer properties other than the components specified. For instance, the compositions of the invention may be substantially free of any other hydrofluorocarbon compound.

[0033] By "substantially no" and "substantially free of", we include the meaning that the compositions of the invention contain 0.5% by weight or less of the stated component, preferably 0.4%, 0.3%, 0.2% or 0.1% or less, based on the total weight of the composition.

[0034] In one embodiment, the compositions contain substantially no trifluoroiodomethane (CF3I).

[0035] All of the chemicals herein described are commercially available. For example, the fluorochemicals may be obtained from Apollo Scientific (UK) and carbon dioxide may be obtained from liquefied gas suppliers such as Linde AG.

[0036] As used herein, all % amounts mentioned in compositions herein, including in the claims, are by weight based on the total weight of the compositions, unless otherwise stated.

[0037] By the term "about", as used in connection with numerical values of amounts of components in % by weight, we include the meaning of ± 0.5 % by weight, for example ± 0.1 % by weight.

[0038] For the avoidance of doubt, it is to be understood that the stated upper and lower values for ranges of amounts of components in the compositions of the invention described herein may be interchanged in any way, provided that the resulting ranges fall within the broadest scope of the invention.

[0039] The compositions of the invention have zero ozone depletion potential.

[0040] Typically, the compositions of the invention have Global Warming Potential (GWP) of less than 300. Conveniently, the compositions of the invention a GWP of less than 250, for example less than 200, such as less than 175, preferably less than 150. The compositions of the invention are of reduced flammability hazard when compared to R-1132a and 1,2-difiuoroethylene (R-1132(E)) aione.

[0041] Flammability may be determined in accordance with ASHRAE Standard 34 incorporating the ASTM Standard E-681 with test methodology as per Addendum 34p dated 2004, the entire content of which is incorporated herein by reference.

[0042] In one aspect, the compositions have one or more of (a) a higher lower flammable limit; (b) a higher ignition energy (sometimes referred to as auto ignition energy or pyrolysis); or (c) a lower flame velocity compared to R-1132a and R-1132(E) alone. Preferably, the compositions of the invention are less flammable compared to R-1132a and R-1132(E) in one or more of the following respects: lower flammable limit at 23°C; lower flammable limit at 60°C; breadth of flammable range at 23°C or 6Q°C; auto-ignition temperature (thermal decomposition temperature); minimum ignition energy in dry air or flame speed. The flammable limits being determined according to the methods specified in ASHRAE-34 and the auto-ignition temperature being determined in a 500ml glass flask by the method of ASTM E659-78.

[0043] In one embodiment, the compositions of the invention have a flammability classifiable as 2L according to the ASHRAE Standard 34 classification method, indicating a weakly flammable fluid with flame speed lower than 10 cm / s.

[0044] The flammability of a refrigerant composition is classified by ASHRAE SSPC34 and ISO817 by a complex assessment process. Two compositions are considered: the "Worst Case Formulation" (WCF) and the "Worst Case Formulation for Flammability" (WCFF). The WCF is the composition that has the maximum permitted level of the most flammable species in the blend according to the manufacturing tolerances specified by the blend designer during the application process. The WCFF is the most flammable composition that can arise during vapour leakage of refrigerant from a cylinder or system at any temperature between -40°C and +60°C.

[0045] Typically, at least the WCF of the compositions of the invention has flammability classified as '2L' by ASHRAE-34 assessment process. Preferably, both WCF and WCFF of the compositions have flammability classified as '2L' by ASHRAE-34 assessment process.

[0046] The compositions of the invention exhibit an unexpected combination of low- / non- fiam inability, low GWP, improved lubricant miscibility and improved refrigeration performance properties. Some of these refrigeration performance properties are explained in more detail below.

[0047] The compositions of the invention typically have a coefficient of performance COP (whether cooling and / or heating COP) that is within 15% of that of R-1234yf. Advantageously, the compositions of the invention have a COP that is within about 10% of that of R-1234yf, such as within about 7%, for example within about 5%, preferably equivalent or higher than that of R-1234yf.

[0048] Typically, the compositions of the invention have a volumetric refrigeration capacity (whether cooling and / or heating capacity) that is within about 15% of that of R-1234yf. Conveniently, the compositions of the invention have a volumetric refrigeration capacity that is within about 10% of that of R-1234yf, for example within about 5%. More preferably, the volumetric refrigeration capacity is greater than or equal to that of R- 1234yf.

[0049] The compositions of the invention typically have a temperature glide in an evaporator or condenser of from about 25K to about 3K, conveniently from about 20K to about 5K, preferably from about 15K to about 5K. Such temperature glides are particularly suitable in thermal management systems employing chiller architectures, such as those using water / ethylene glycol or triacetin / carbon dioxide.

[0050] The compositions of the invention typically have a bubble point at atmospheric pressure of below about -35 °C. Preferably, the compositions have a bubble point at atmospheric pressure of below about -42 °C, preferably below about -50 °C. Alternatively or additionally, it is preferred that the compositions of the invention have a vapour pressure greater than 1 bar at -40°C.

[0051] Conveniently, the compositions of the invention have a burning velocity of less than about 10 cm / s as measured by ASHRAE Standard 34.

[0052] Conveniently, the total generation potential of TFA from unit mass of the composition pf the invention is less than that of the equivalent mass of R-1234yf, such as 10% or less, advantageously 5% or less, preferably 2% or less or even 1% or less.

[0053] The compositions of the invention are typically suitable for use in existing designs of equipment and are compatible with ail classes of lubricant currently used with established HFC refrigerants. They may be optionally stabilised or compatibilised with mineral oils (e.g. lubricants) by the use of appropriate additives such as polyol esters (POEs), for example POEs with a viscosity of about 7 to 32 cSt at about 40 °C.

[0054] Therefore, in one aspect, the composition of the invention is combined with a lubricant, particularly when used in heat transfer equipment. Thus, the invention provides the use of a composition comprising a lubricant and the composition of the invention in a thermal management system of an electric vehicle.

[0055] Conveniently, the lubricant is selected from the group consisting of mineral oil, silicone oil, polyaikyi benzenes (PABs), polyol esters (POEs), polyalkylene glycols (PAGs, also known as polyethers), polyalkylene glycol esters (PAG esters), polyvinyl ethers (PVEs), poly (alpha-olefins) and combinations thereof. PAGs and POEs are currently preferred lubricants for the compositions of the invention.

[0056] Advantageously, the lubricant further comprises a stabiliser. In a similar aspect, the composition of the invention may be combined with a stabiliser.

[0057] Preferably, the stabiliser is selected from the group consisting of diene-based compounds, phosphates, phenol compounds (such as 2,6-Di“tert-butyl“4-methylphenol) and epoxides, and mixtures thereof.

[0058] Conveniently, the composition of the invention may be combined with a flame retardant.

[0059] Advantageously, the flame retardant is selected from the group consisting of tri-(2- chloroethylj-phosphate, (chloropropyl) phosphate, tri-(2,3-dibromopropyl)-phosphate, tri- (l,3-dichloropropyl)-phosphate, diammonium phosphate, various halogenated aromatic compounds, antimony oxide, aluminium trihydrate, polyvinyl chloride, a fluorinated iodocarbon, a fluorinated bromocarbon, trifluoro iodomethane, perfluoroalkyl amines, bromo-fluoroalkyl amines and mixtures thereof.

[0060] In one aspect of the invention, the thermal management system of an electric vehicle comprises or is a liquid chiller system, further wherein the liquid chiller system comprises at least one counter-flow heat exchanger for exchanging heat between the refrigerant and the liquid.

[0061] Such a chiller architecture can be used in conjunction with an air-to-air architecture. For example, a chiller architecture can be used for managing the temperature of the battery of an tV, while air-to-air architecture can be used for air-conditioning of the passenger cabin.

[0062] Typically, the liquid employed in the liquid chiller system as disclosed above is selected from water, brine, glycol, a synthetic hydrocarbon fluid, a silicone-based fluid or wholly or partially fluorinated organic fluid (for example a fluorinated ether or ketone), fluid blends with freeze point or viscosity reduction additives (such as Triacetin, Diacetin, acetone and / or carbon dioxide, for example acetone with carbon dioxide) and mixtures thereof. Preferably, the liquid chiller system is a water chiller system, a water / glycol chiller system or a chiller system employing a wholly or partially fluorinated organic fluid.

[0063] The counter-flow heat exchanger is adapted such that the refrigerant and the liquid flow in a counter-current flow (including quasi-counter-current flow) relative to each other when the refrigerant and the liquid pass through the counter-flow heat exchanger. In such an arrangement, the refrigerant condensation temperature need only be higher than the temperature of coolant entering the condenser; and the highest refrigerant evaporation temperature need only be lower than the heat source inlet temperature. Thus, temperature glide may allow the refrigerant to operate over a lower temperature range than a fluid with no glide and, consequently, to gain in relative capacity and energy efficiency.

[0064] Typically, the liquid chiller system is a liquid chiller system adapted for heating and / or cooling a battery and / or a passenger cabin of an electric vehicle. For example, the liquid chiller system may be adapted for cooling and / or heating the passenger cabin of an electric vehicle and may be adapted for cooling the battery of an electric vehicle. Alternatively or additionally, the liquid chiller system may be adapted for cooling other sources of potentially useful waste heat such as power electronics, instrument displays or braking systems.

[0065] The thermal management system of an electric vehicle typically contains a heat pump and / or air-conditioning system.

[0066] The invention also provides the use of a composition of the invention as a replacement for an existing refrigerant in a thermal management system of an electric vehicle, preferably wherein the existing refrigerant is or comprises propane and / or R-1234yf, such wherein the existing refrigerant is propane or R-1234yf, preferably R-1234yf. Preferably, the thermal management system comprises or is a liquid chiller system as disclosed above. Also provided is a method of retrofitting a thermal management system of an electric vehicle comprising the step of removing an existing heat transfer composition, and introducing a composition of the invention. Advantageously, the existing heat transfer composition is propane (R-290) or 2,3,3,3-tetrafiuoropropene (R-1234yf), preferably R- 1234yf. Preferably, the thermal management system comprises or is a liquid chiller system as disclosed above.

[0067] In a related aspect of the invention, there is provided a thermal management system of an electric vehicle comprising a composition of the invention, such as wherein the thermal management system comprises or is a liquid chiller system as disclosed above.

[0068] In a related aspect of the invention, there is provided a heat transfer device comprising a refrigerant, wherein the refrigerant is a composition of the invention, further wherein the heat transfer device comprises a heat sink fluid or heat source and at least one counterflow heat exchanger for exchanging heat between the refrigerant and the heat sink fluid or heat source. The invention also provides the use of a composition of the invention in such a heat transfer device as herein described.

[0069] The counter-flow heat exchanger is adapted such that the refrigerant and the liquid flow in a counter-current flow (including quasi-counter-current flow) relative to each other when the refrigerant and the liquid pass through the counter-flow heat exchanger.

[0070] In such a heat transfer device, the heat sink fluid or heat source may be selected from water, brine, glycol, a synthetic hydrocarbon fluid, a silicone-based fluid or wholly or partially fluorinated organic fluid (for example a fluorinated ether or ketone), fluid blends with freeze point or viscosity reduction additives (such as Triacetin, Diacetin, acetone and / or carbon dioxide, for example acetone with carbon dioxide) and mixtures thereof.

[0071] In another aspect, there is provided the use of the composition of the invention as a refrigerant in a thermal management system of an electric vehicle, wherein the thermal management system comprises an air-to-air architecture. The invention also provides such a thermal management system comprising a composition of the invention. It has now been surprisingly found that these compositions can be used in air-to-air designs without little or no modification of the existing design architecture. In these aspects, the thermal management system typically comprises a heat pump and / or an air-conditioning system, preferably a heat pump adapted to perform air-conditioning. The EV thermal management systems of this aspect may also incorporate a chiller loop for cooling heat generating components of the electric vehicle, such as battery, power electronics and / or electric motors.

[0072] Further in this aspect, when hot air is passed in crossflow (near) perpendicularly over rows of refrigerant the tubes of the evaporator, the air is cooled while the refrigerant evaporates inside the tubes of the evaporator. Similarly, heat is rejected by flowing external air in crossflow over the tubes of the condenser and condensing the refrigerant inside the tubes. For the heat exchange to occur in the condenser of the refrigerant circuit, the lowest refrigerant condensation temperature must be higher than the temperature of air leaving the condenser. Similarly, in the evaporator, the highest refrigerant evaporation temperature must be lower than the temperature of air leaving the evaporator.

[0073] If a refrigerant undergoes temperature glide during evaporation or condensation, the crossflow arrangement tends to reduce the effective temperature difference between air and refrigerant compared to a single-component refrigerant with no glide thus decreasing the efficiency of the heat exchanger. This has the effect of penalizing the performance of the refrigerant relative to a fluid with no glide. For this reason, it is generally desirable when using crossflow heat exchangers for the refrigerant glide to be kept low.

[0074] In another aspect of the invention, there is provided a method of producing cooling which method comprises evaporating a composition of the invention in the vicinity of a body to be cooled. Preferably, the method is a method for producing cooling in an electric vehicle.

[0075] According to a further aspect of the invention, there is provided a method for producing heating which method comprises condensing a composition of the invention in the vicinity of a body to be heated. Preferably, the method is a method for producing heating in an electric vehicle.

[0076] The compositions of the invention may also be prepared simply by mixing the R-32, R- 152a and R-1234ze(E) (and optional components such as R-1132(E), CO2, a lubricant, a stabiliser or an additional flame retardant) in the desired proportions. The compositions can then be added to a heat transfer device (or used in any other way as defined herein).

[0077] The invention will now be described with reference to the following, non-limiting examples.

[0078] Examples A thermodynamic property model was constructed using the NIST REFPROP9.1 software package. This was used to model refrigeration cycle performance for an idealised vapour compression cycle with known heat exchanger sizes, using the performance of R-1234yf as a reference fluid.

[0079] The heat exchangers were modelled as being arranged in counter-current flow. The sizes of heat exchangers required were determined firstly based on using R~1234yf as refrigerant, with specified temperature changes of heat source and heat sink fluids and specified minimum temperature difference between refrigerant and external fluid. Then, the performance of selected refrigerant blends of the invention was evaluated by adjusting condensation and evaporation pressures of the refrigerant so that the same cooling or heating capacity was achieved with the same size of heat exchanger. This approach is known as "UA Cycle" modelling as described in Chapter 3 of "Vapor Compression Heat Pumps With Refrigerant Mixtures", R. Radermacher, Y. Hwang, pub. CRC Press (Taylor & Francis) 2005, which is incorporated herein by reference.

[0080] The cycle conditions assumed for this modelling for simulation of a cooling or heating cycle were:

[0081] Tables 1 to 4 show the performance of R-1234yf and selected compositions of R-32, R- 152a and R-1234ze(E) at these conditions. The first composition shown is R-444A, which is a blend of 83% by weight R-1234ze(E), 12% by weight R-32 and 5% by weight R-152a.

[0082] Tables 5 and 6 show the performance of selected compositions of R-32, R-152a, R~1234yf and R-1234ze(E) at these conditions compared to R-1234yf, R-444A and a ternary blend of 12% by weight R-32, 10% by weight R-152a and 78% by weight R-1234yf. Table 1 - Performance of blends of R-32 (10 to 12 wt%), R-152a (5 to 35 and R-1234ze(E) (55 to 85 wt%) in Cooling Mode

[0083] Tabie 2 - Performance of blends of R--32 (15 to 18 wt%), R-152a (5 to 30 wt%) and R-1234zefE) (55 to 80 wt%) in Coohng Mode

[0084] Table 3 - Performance of blends of R-32 (10 to 12 wt%), R-152a (5 to 35 wt%) and R-1234ze(E) (55 to 85 wt%) in Heating Mode

[0085] Table 4 - Performance of blends of R-32 (15 to 18 wt%), R-152a (5 to 30 and R-1234ze(E) (55 to 80 wt%) in Heating Mode

[0086] Table 5 - Performance of blends of R-32 (12 wt%), R-152a (5 to 10 wt%). R-1234ze(E) (0 to 83 wt%) and R-1234vf (0 to 83 wt%) in Cooling Mode

[0087] Table 6 - Performance of blends of R-32 (12 wt%), R-152a (5 to 10 wt%). R-1234ze(E) (0 to 83 wt%) and R-1234vf (0 to 83 wt%) in Heating Mode

[0088] The compositions tabulated have GWP values less than 150 and are believed also to have burning velocities of less than lOcm / s, which would result in their classification by ISO / ASHRAE methodology as flammability class "2L". The operating pressures for R.-444A and the other compositions are very close to R-1234yf in both cooling and heating modes.

[0089] The results in Tables 1 to 4 surprisingly demonstrate that R-444A displays improved performance relative to R~1234yf in terms of energy efficiency and capacity in both cooling and heating modes when used in a chiller architecture.

[0090] The results in Tables 5 and 6 show that inclusion of R-1234yf in the compositions of the invention generally (and favourably) increases capacity, decreases glide slightly and reduces compressor exit temperature (which can be good for higher R-32 content). This advantages are at the expense of lower energy efficiency (COP) and higher cost (R-1234yf more expensive than R-1234ze(E)).

[0091] The invention is defined in the following claims.

Claims

CLAIMS1. Use of a composition as a refrigerant in a thermal management system of an electric vehicle, wherein the composition comprises:(a) trans-l,3,3,3-tetrafluoropropene (R~1234ze(E));(b) difluoromethane (R-32); and(c) 1,1-difluoroethane (R-152a).

2. The use according to claim 1, wherein the composition is substantially free of 1,1- difiuoroethylene (R-1132a), preferably wherein the composition comprises no R- 1132a.

3. The use according to claim 1 or 2, wherein the composition comprises from about 55 to about 95% by weight R-1234ze(E), such as from about 60 to about 95% by weight or from about 55 to 90% by weight, for example from about 65 to about 93% by weight, optionally from about 70 to about 92% by weight, preferably from about 75 to about 90% by weight.

4. The use according to any of claims 1 to 3, wherein the composition comprises from about 1 to about 30% by weight R-32, such as from about 2 to about 25% by weight, for example from about 3 to about 25% by weight, optionally from about 3 or about 4 to about 22% by weight, preferably from about 5 or 8 to about 20% by weight.

5. The use according to any of the preceding claims, wherein the composition comprises from about 1 to about 40% by weight R-152a, such as from about 1 or about 2 to about 35% by weight R-152a, for example from about 2 to about 30% by weight, optionally from about 3 to about 25% by weight, preferably from about 4 to about 15 or 20% by weight.

6. The use according to any of the preceding claims, wherein the composition comprises from about 55 to about 95% by weight R-1234ze(E), from about 1 to about 30% by weight R-32 and from about 1 to about 30% by weight R-152a.

7. The use according to claim 6, wherein the composition comprises from about 60 to about 95% by weight R-1234ze(E), from about 2 to about 25% by weight R-32 and from about 1 to about 25% by weight R-152a, such as from about 65 to about 93% by weight R-1234ze(E), from about 3 to about 25% by weight R-32 and from about2 to about 20% by weight R-152a; or from about 70 to about 92% by weight R- 1234ze(E), from about 3 to about 22% by weight R-32 and from about 2 to about 15% by weight R-152a, preferably from about 75 to about 90% by weight R- 1234ze(E), from about 5 to about 20% by weight R-32 and from about 2 to about 10% by weight R-152a.

8. The use according to any of the preceding claims, wherein the composition comprises from about 80 to about 86% by weight R-1234ze(E), from about 9 to about 15% by weight R-32 and from about 2 to about 8% by weight R-152a, preferably from about 81 to about 85% by weight R-1234ze(E), from about 10 to about 14% by weight R-32 and from about 3 to about 7% by weight R-152a.

9. The use according to any of the preceding claims, wherein the composition comprises from 0 to about 40% by weight 2,3,3,3-tetrafluoropropene (R-1234yf), such as from 0 to about 20% by weight, preferably from 0 to about 10% by weight.

10. The use according to any of the preceding claims, wherein the composition consists essentially of the stated components.

11. The use according to any of the preceding claims, wherein the composition has a Global Warming Potential (GWP) of less than 250, for example less than 200, such as less than 175, preferably less than 150.

12. A composition according to any of the preceding claims, wherein the composition has: a. a higher flammable limit' b. a higher ignition energy; and / or c. a lower flame velocity compared to R-1132a and / or R-1132(E) alone, preferably wherein the composition is nonflammable.

13. A composition according to any of the preceding claims, wherein the composition has a coefficient of performance (COP) that is within about 10% of that of R-1234yf, such as within about 7%, for example within about 5%, preferably wherein the COP is equivalent or higher than that of R-1234yf.

14. A composition according to any of the preceding claims, wherein the composition has a volumetric refrigeration capacity that is within about 15% of that of R-1234yf, such as within about 10%, for example within about 5%, preferably wherein the volumetric refrigeration capacity is greater than or equal to that of R~1234yf.

15. A composition according to any of the preceding claims wherein the composition has a temperature glide in an evaporator or condenser of from about 20K to about 5K, preferably from about 15K to about 5K.

16. A composition according to any of the preceding claims, wherein the composition has a burning velocity of less than about 10 cm / s as measured by ASHR.AE Standard 34.

17. A composition according to any of the preceding claims, wherein the composition has a bubble point at atmospheric pressure of below about -42 °C, preferably below about -50 °C.

18. A composition according to any of the preceding claims, wherein the composition has a total generation potential of TFA from unit mass of the composition which is less than that of the equivalent mass of R-1234yf, such as 15% or less, for example 2% or less, preferably 1% or less.

19. The use of a composition comprising a lubricant and a composition as defined in any of claims 1 to 17 in a thermal management system of an electric vehicle, wherein the lubricant is selected from mineral oil, silicone oil, polyalkyl benzenes (PABs), polyol esters (POEs), polyalkyiene glycols (PAGs), polyalkylene glycol esters (PAG esters), polyvinyl ethers (PVEs), poly (alpha-olefins) and combinations thereof, preferably wherein the lubricant is selected from PAGs or POEs.

20. The use of a composition comprising a stabilizer and a composition as defined in any of claims 1 to 17 in a thermal management system of an electric vehicle, preferably wherein the stabiliser is selected from diene-based compounds, phosphates, phenol compounds (such as 2,6-Di-tert-butyl-4-methylphenol) and epoxides, and mixtures thereof.

21. The use of a composition comprising a flame retardant and a composition as defined in any of claims 1 to 18 in a thermal management system of an electric vehicle, preferably wherein the flame retardant is selected from the group consisting of tri- (2-chloroethyi)-phosphate, (chloropropyl) phosphate, tri-(2,3-dibromopropyl)-phosphate, tri-(l,3-dichloropropyl)-phosphate, diammonium phosphate, various halogenated aromatic compounds, antimony oxide, aluminium trihydrate, polyvinyl chloride, a fluorinated iodocarbon, a fluorinated bromocarbon, trifluoro iodomethane, perfluoroalkyl amines, bromo-fluoroalky I amines and mixtures thereof.

22. Use of a composition according to any of claims 1 to 18 as a replacement for an existing refrigerant in a thermal management system of an electric vehicle.

23. The use according to claim 22, wherein the existing refrigerant is or comprises propane and / or 2,3,3,3-tetrafluoropropene (R-1234yf), such as wherein the existing refrigerant is R-1234yf.

24. The use according to any of claims 19 to 23, wherein the thermal management system comprises or is a liquid chiller system, further wherein the liquid chiller system comprises at least one counter-flow heat exchanger for exchanging heat between the refrigerant and the liquid.

25. The use according to claim 24, wherein the system is adapted for cooling and / or heating the passenger cabin and / or for cooling the battery of an electric vehicle.

26. The use according to claim 24 or 25, wherein the system is adapted for cooling power electronics, instrument displays and / or braking systems27. The use according to any of claims 24 to 26, wherein the liquid is selected from water, brine, glycol, a synthetic hydrocarbon fluid, a silicone-based fluid or wholly or partially fluorinated organic fluid (for example a fluorinated ether or ketone), fluid blends with freeze point or viscosity reduction additives (such as Triacetin, Diacetin, acetone and / or carbon dioxide) and mixtures thereof.

28. The use according to any of claims 19 to 27, wherein the thermal management system comprises a heat pump and / or an air-conditioning system, preferably a heat pump adapted to perform air-conditioning.

29. A method of producing cooling which method comprises evaporating a composition as defined in any of Claims 1 to 18 in the vicinity of a body to be cooled.

30. A method for producing heating which method comprises condensing a composition as defined in any of Claims 1 to 18 in the vicinity of a body to be heated.

31. A thermal management system of an electric vehicle comprising a composition as defined in any of Claims 1 to 18.

32. The thermal management system according to claim 31, wherein the thermal management system is or comprises a liquid chiller system.

33. The thermal management system according to claim 31 or 32, wherein the thermal management system comprises a heat pump and / or an air-conditioning system, preferably a heat pump adapted to perform air-conditioning.