FLUID COMPOSITION

This invention relates to fluid compositions containing a fluoropropene, such as pentafluoropropene or tetrafluoropropene, and other fluorinated hydrocarbons. The fluid compositions may be of use as foam blowing agents for thermoplastic or thermoset insulation foams, as well as refrigerant compositions with the potential to replace refrigerant compositions having a higher level of greenhouse warming potential (GWP).

Fluorocarbon based fluids have found widespread use in industry in a number of applications, including as refrigerants, aerosol propellants, blowing agents, heat transfer media, and gaseous dielectrics. Historically, other fluids were used for such uses, such as R-I l (trichlorofluoromethane) and other brominated and chlorinated hydrocarbons, as well as latterly fluids such as R- 134a (1,1,1,2- tetrafluoroethane). However the search is continually on for fluids which may have a less deleterious effect on the earth's atmosphere, including reduced GWP and a zero or low ozone depletion potential, as well as providing improved energy efficiency performance in the particular application in which they are used. Such fluids may beneficially replace those already in industrial usage, for the types of usage outlined above.

In the context of polymer foam preparation, it is known to prepare polymer foams such as for example polyurethane or polyisocyanurate foams using so-called blowing agents. Such foams may be open- or closed-cell, and they may typically be used for insulation. For example, US-A-4997706 describes a closed-cell rigid polymer foam prepared in the presence of a physical blowing agent comprising a C _2- 6 polyfluorocarbon compound containing no chlorine or bromine atoms. Traditionally, R-I l had been used as a liquid blowing agent in the production of thermoset insulating foams, such as rigid polyurethane, and thermoplastic insulating foams, such as polystyrene.

In the light of the Montreal Protocol, use of R-I l has been greatly reduced, and has been substituted by a number of fluids, including R- 14 Ib, R-22/R-142b mixtures, cyclopentane, R-134a, R-245fa and R-365 mfc.

Disadvantageous^, R- 14 Ib and R-22/R-142b are hydrochlorofluorocarbons, and have finite ozone depletion potential. In addition, whilst cyclopentane has essentially no ozone depletion potential, and a very short atmospheric lifetime, it is highly flammable and requires particular care in its use and handling. R-134a has essentially no ozone depletion potential but does have a GWP, relative to CO ₂ on a 100 year timescale, of around 1300. R-245fa and R-365mfc also have essentially no ozone depletion potential, but have GWP values of around 800 to 850.

In the context at least of blowing agents for foams, there remains a need to provide a blowing agent having a GWP lower than that of either R-245fa or R-365mfc, whilst essentially retaining or improving the insulation values of foams utilizing these blowing agents.

In relation to refrigerants, the sought-after benefits are similar in that it is desirable to provide a refrigerant composition having low or zero ozone depletion potential that is capable of replacing existing refrigerants with greater adverse environmental effects, and advantageously having a higher refrigeration capacity.

In a first aspect of the invention, there is provided a fluid composition comprising:

a) a fluoropropene; and b) a hydrofluorocarbon of formula CF ₃ (CHa) _n CF ₂ H wherein n = 1 or 2

Compositions of this type may be particularly suitable as foam blowing agents, for either thermosetting or thermoplastic insulation foams, and also as a refrigerant.

In a further embodiment of the invention, there is provide a fluid composition comprising:

a) a fluoropropene which is pentafluoropropene or tetrafluoropropene, or mixtures thereof; b) a pentafluoropropane or a pentrafluorobutane, or mixtures thereof.

In a preferred aspect, the pentafluoropropene may be the Z and/or E isomers of 1,2,3,3,3 pentafluoropropene (R-1225). Conveniently the R-1225 is R-1225ye. In a further preferred aspect, the tetrafluoropropene may be R- 1234, preferably 2,3 ,3 ,3 -tetrafluoropropene (R- 1234yf) .

Preferably, the pentafluoropropane is R-245fa.

Preferably, the pentafluorobutaine is R-365mfc.

Conveniently, compositions according to the invention are non-flammable.

Conveniently compositions according to the invention also have a boiling point below that of either R-245fa or R-365mc.

Conveniently, compositions according to the invention have a reduced GWP compared to either R-245fa or R-265mfc.

Preferably, the composition has a GWP of below 800 over 100 years relative to CO ₂ , more preferably less than 750, even more preferably less than 700.

Compositions according to the invention may provide superior blowing agents for use in foam blowing. The addition of fluoropropene to the composition acts to increase the vapour pressure of the composition when it is used as a blowing agent at relatively low temperatures, thus ensuring that in the subsequently blown foam an adequate insulating gas vapour pressure is maintained in the cells. This increased vapour pressure acts to reduce the likelihood of foam cell collapse,

under partial vacuum, and to retain a relatively high foam insulation performance, as reflected in a higher foam insulation factor (R-value). Additionally, the fluoropropenes in the compositions have good gas heat capacities. The ideal-gas heat capacity of R-1225ye(E) isomer at 25°C is estimated as 110.2 J/mol.K using "Hyperchem" molecular modelling software; the ideal-gas heat capacity of

R1225ye(Z) isomer is estimated as 109.9 J/mol.K using the same technique; the heat capacity of R-1234yf was measured as 90.3 J/mol.K by means of determination of the speed of sound of the gas using a resonator apparatus. These heat capacities relatively closely resemble those of e.g. R-245a (115.47 J/mol.K) and R-365mfc (138.37 J/mol.K). These relatively low levels of heat capacity provide a reduced level of heat capacity, which is expected to result in improved insulation performance in the resultant blown foam.

According to a further aspect of the invention, there is provided a polymer foam prepared from a foam-fluid forming composition comprising a physical blowing agent comprising a fluid composition as herein described. Conveniently, the foam comprises up to about 20% by weight of the fluid composition.

The usefulness of foamed plastics materials in a variety of applications is well known. For example, polyurethanes and polyisocyanurate foams are widely used as insulators. Conveniently, such foams (as preferred foams made using the fluid composition of the invention) are closed cell polymer foams, since the closed cells in the foam promote good insulating properties in the resulting foam. These insulating properties can be further enhanced if the gas mixture in the foam cells has a high thermal resistance or a low thermal conductivity.

Generally, polyurethane and polyisocyanurate foams are prepared by reacting an organic polyisocyanate with an active hydrogen-containing compound in the presence of a blowing agent or agents. Generally, such blowing agents are inert organic compounds which do not decompose or react during the polymerization reaction and which as a result of the exothermic reaction if not already in the gaseous phase become converted to a gaseous phase. The gas becomes encapsulated in the liquid phase of the polymerizing reaction mixture resulting in

the formation of cells, causing the reaction mixture to expand and form a foam which subsequently cures to become a rigid closed-cell foam.

In one aspect, the invention provides a polymer foam prepared from a foam- forming composition containing a physical blowing agent which is the fluid composition present at up to about 20% by weight, based on the total weight of the compositions. Conveniently the resultant foam comprises at least 0.01% of the fluid composition of the invention as the blowing agent.

The foam-forming composition used to prepare the foam of this invention may be a thermoplastic composition comprising, for example, a thermoplastic polyethylene or a polystyrene polymer or the like. However, preferred foam- forming compositions are those which lead to the preparation of thermoset polymers, especially polyurethane and polyisocyanurate polymers. Such thermoset foam-forming compositions are preferred because of the ability to prepare fine-celled polymers by foam-in-place procedures. To provide for optimum physical foam properties including thermal insulation, advantageously the average cell size of the foam is less than about 0.5, preferably less than about 0.45, and more preferably less than about 0.4 mm.

The foam-forming composition contains the physical blowing agent in a quantity sufficient to provide a foam having an overally density of from about 10 to about 200, preferably from 10 to about 100, more preferably from about 15 to about 80 and most preferably from about 18 to about 60 kg/m ³ .

To provide for such foam densities, the physical blowing agent advantageously is present in quantities up to and including 20% weight based on the total weight of the foam-forming composition, including physical blowing agent present. Foams having the higher densities are prepared in the presence of lower quantities of the physical blowing agent. When blowing agent precursor compounds are present in the composition the total quantity of physical blowing agent required to produce foams of the desired densities will be reduced accordingly.

Preferably, the fluid compositions of the invention exhibits relative ozone depletion potentials, as currently recognized, of less than about 0.15, preferably less than about 0.05, more preferably less than 0.01 and most preferably zero.

The fluid compositions of the invention are further characterized by advantageously having a boiling point at standard atmospheric pressure of less than about 65°C, preferably less than about 45°C, more preferably less than about 25°C and most preferably less than about 0 ⁰ C. Use of fluid compositions having a boiling point above 65 ⁰ C may not be desirable if resulting foams are to exhibit good low temperature dimensional stability. To allow for convenient handling and foaming of the composition, advantageously the fluid composition preferably has a boiling point of at least -60 ⁰ C, preferably at least -4O ⁰ C and more preferably at least -3O ⁰ C. Preferably when used as a refrigerant the fluid composition has a boiling point at standard atmospheric pressure of about -50 ⁰ C to +25 ⁰ C.

In a preferred embodiment, the polymer foam may be made in the presence of a blowing agent precursor. A blowing agent precursor is a substance which reacts chemically with the polymerizing reaction mixture or decomposes thermally as a result of exposure to, for example, the reaction exotherm, generating in situ a gas. This generated gas functions as an additional blowing agent in preparing the foam. A known and preferred blowing agent precursor is water, which when reacted with isocyanate provides gases carbon dioxide. Other carbon dioxide generating blowing agent precursor compounds include the amine/carbon dioxide complexes described in US-A-4735970 and US-A-4500656, which are hereby in the relevant part incorporated by reference.

Conveniently, the resultant foam may contain sufficient blowing agent precursor (e.g. water) to generate a level of carbon dioxide in the resultant foam of 0.01% to 5% by weight.

In a preferred embodiment of the invention, especially when the rigid polymer foam is a polyurethane or polyisocyanurate polymer, prepared in the presence of a

blowing agent precursor such as for example water, providing carbon dioxide gas, the initial gas composition within the cells of the foam comprises:

a) from about 1 to about 60 mole percent, based on the combined mole quantities of (a) and (b) present, of the fluid composition; and b) from about 40 to about 99 mole percent, based on the combined quantities of (a) and (b) present, carbon dioxide.

Conveniently, the initial cell gas composition comprises the fluid composition from about 5 to about 55, more preferably from about 10 to abut 55 and most preferably from about 15 to about 50 mole percent, whilst the same mixture comprises the carbon dioxide preferably from about 45 to abut 95, more preferably from about 45 to about 90, and most preferably from about 50 to about 85 mole percent.

A preferred process according to the invention is characterized in that an isocyanate-containing compound is mixed and allowed to react with an active hydrogen-containing compound in the presence of up to about 20 weight percent, based on total combined weights of isocyanate-containing and active hydrogen- containing compound present, of a physical blowing agent comprising the fluid composition of the invention.

In a preferred process, advantageously the fluid composition component of the physical blowing agent is present in from about 5.0 to about 17, preferably from about 1.0 to about 10, and more preferably in from about 1.5 to about 8.0 weight percent based on the combined weights of isocyanate-containing material and active hydrogen-containing compound present. Suitable and preferred fluid compositions for use in the process are as herein described.

Isocyanate-containing compounds suitable for use in the process of this invention are organic polyisocyanate compounds typically having an average isocyanate content of from about 20 to about 50, and preferably from about 25 to about 35 weight percent.

Polyisocyanates suitable for use in the process of this invention include aromatic, aliphatic and cycloaliphatic polyisocyanates and combinations thereof.

Representative of these types are diisocyanates such as m- or p-phenylene diisocyanate, toluene-2,4-diisocyanate, tolune-2,6-diisocyanate, hexamethylene-

1 ,6-diisocyanate, tetram ethylene- 1 ,4-diisocyanate, cyclohexane- 1 ,4-diisocyanate, hexahydrotoluene diisocyanate (and isomers), naphthylene-l,5-diisocyanate, 1- methylphenyl-2,4-phenyldiisocyanate, diphenylmethane-4,4 '-diisocyanate, diphenylmethane-2,4 '-diisocyanate, 4,4'-biphenylene diisocyanate, 3,3 '- dimethoxy-4,4'-diphenylenediisocyanate and 3,3 '-dimethyldiphenylpropane-4,4'- diisocyanate; triisocyanates such as toluene-2,4,6-triisocyanate and polyisocyanates such as 4, 4'-dimethyldiphenylmeth ane-2,2 ',5 ',5 '- tetraisocyanate, and the diverse polymethylene polyphenyl polyisocyanates.

The isocyanate is advantageously used in a quantity sufficient to provide for a well cross-linked rigid foam. Advantageously the isocyanate index, the ratio of isocyanate moieties to active hydrogen atoms present in the foam-forming composition, is from about 0.9 to about 5.0, preferably about 0.9 to about 3.0, more preferably about 1.0 to about 2.0 and most preferably from about 1.0 to about 1.6.

Active hydrogen-containing compounds which are useful in this present invention include those materials having two or more groups which contain an active hydrogen atom that will react with an isocyanate, such as described in US-A- 4394491 and incorporated herein by reference. Preferred among such compounds are materials having hydroxyl, primary or secondary amine, carboxylic acid, or thiol groups. Polyols, i.e. compounds having at least two hydroxyl groups per molecule, are especially preferred due to their desirable reactivity with polyisocyanates.

Suitable active hydrogen-containing compounds for preparing rigid polyisocyanate-based foams include those having an equivalent weight of about 50 to about 700, preferably from about 70 to about 300, more preferably from

about 90 to about 200. Such active hydrogen-containing compounds advantageously have at least 2, preferable from about 3, and advantageously up to about 16 and preferably up to about 8 active hydrogen atoms per molecule. The number of active hydrogen atoms may also be referred to as "functionality". Active hydrogen-containing compounds which have functionalities and equivalent weighs outside these limits may also be used, but the resulting foam properties may not be desirable for a rigid application.

Suitable additional isocyanate-reactive materials include polyether polyols, polyester polyols, polyhydroxyl-teπninated acetyl resins, hydroxy! -terminated amines and polyamines, and the like. Examples of these and other suitable isocyanate-reactive materials are described more fully in US-A-4394491, particularly in columns 3-5 thereof. Most preferred for preparing rigid foams, on the basis of performance, availability and cost, is a polyol prepared by adding an alkylene oxide to an initiator having from about 2 to about 8, preferably from about 3 to about 8 active hydrogen atoms. Exemplary of such polyether polyols include those commercially available under the trademark VORANOL, and include VORANOL 202, VORANOL 360, VORANOL 370, VORANOL 446,

VORANOL 490, VORANOL 575, VORANOL 800, all sold by the Dow Chemical Company, and Pluracol 824, sold by BASF Wyandotte.

Other most preferred polyols include alkylene oxide derivatives of Mannich condensate as taught in, for example US-A-3297597; 4137265 and 4383102 and incorporated herein by reference, and amino-alkylpiperazine-initiated polyether polyols as described in US-A-4704410 and 4704411 also incorporated herein by reference.

In addition to the foregoing critical components, it is optional but often desirable to employ certain other ingredients in preparing polyisocyanate-based foams. Among these additional ingredients are secondary physical blowing agents and blowing agent precursor compounds, catalysts, surfactants, flame retardants, preservatives, colorants, antioxidants, reinforcing agents, fillers, antistatic agents and the like.

One or more catalysts for the reaction of the active hydrogen-containing compound with the polyisoyanate are advantageously present. Any suitable urethane catalyst may be used, including tertiary amine compounds and organometallic compounds. Exemplary tertiary amine compounds include triethylenediamine, N-methylmorpholine, pentamethyldiethylenetriamine, tetramethylethylenediamine, 1 -methyl-4-dimethylaminoethylpiperazine, 3- methoxy-N-dimethylpropylamine, N-ethylmorpholine, diethylethanolamine, N- cocomorpholine, N,N-dimethyl-N ',N '-dimethylisopropylpropylenediamine, N ₅ N- dimethyl-3-diethylaminopropylamine, dimethylbenzylamine and the like. Exemplary organometallic catalysts include organomercury, organolead, organoferric and organotin catalysts, with organotin catalysts being preferred among these. Suitable tin catalysts include stannous chloride, tin salts of carboxylic acids such as dibutyltin di-2-ethyl hexanoate, as well as other organometallic compounds such as are disclosed in US-A-2846408. A catalyst for the trimerization of polyisocyanates and formation of polyisocyanurate polymers, such as an alkali metal alkoxide, alali metal carboxylate, or quaternary amine compound, may also optionally be employed.

When employed, the quantity of catalyst used is sufficient to increase the rate of polymerization reaction. Precise quantities must be determined experimentally, but generally will range from about 0.001 to about 3.0 parts by weight per 100 parts active hydrogen-containing compound depending on the type and activity of the catalyst.

It is generally highly preferred to employ a minor amount of a surfactant to stabilize the foaming reaction mixture until it cures. Such surfactants advantageously comprise a liquid or solid organosilicone surfactant. Other less preferred surfactants include polyethylene glycol ethers of long chain alcohols, tertiary amine or alkonolamine salts of long chain alkyl acid sulfate esters, alkyl sulfonate esters and alkyl arylsulfonic acids. Such surfactants are employed in amounts sufficient to stabilize the foaming reaction mixture against collapse and

the information of large, uneven cells. Typically, about 0.2 to about 5 parts of the surfactant per 100 parts by weight are sufficient for this purpose.

In the process of making a polyisocyanate-based foam, the polyol(s), polyisocyanate and other components are contacted thoroughly, mixed and permitted to expand and cure into a cellular polymer. The particulate mixing apparatus is not critical, and various types of mixing head and spray apparatus are conveniently used. It is often convenient, but not necessary, to pre-blend certain of the raw materials prior to reacting the polyisocyanate and active hydrogen- containing components. For example, it is often useful to blend the polyol(s), blowing agent, surfactants, catalysts and other components except for polyisocyanates, and then contact this mixture with the polyisocyanate. Alternatively, all components can be introduced individually to the mixing zone where the polyisocyanate and polyol(s) are concerned. It is also possible to pre- react all or a portion of the polyol(s) with the polyisocyanate to form a prepolymer.

In a further aspect of the invention, the fluid composition may be used as a refrigerant.

Historically, heat transfer devices such as refrigerators, freezers, heat pump and air conditioning systems are known which utilize refrigerant compositions. Such devices have tended initially to use halogenated chlorofluorocarbon refrigerants such as R-12B1, R-I l, R-12, R-22 and R-502. However, such refrigerants are destructive to the earth's ozone layer, and may also contribute to global warming. Although replacements have been developed in the form of 1,1,1,2 tetrafluoroethane (R- 134a), there is a need for refrigerants which have an even lower GWP, and provide good refrigerant performance.

Thus, according to a further aspect of the invention, there is provided a heat transfer device comprising an evaporator, a condenser, a compressor and an expansion valve, in which there is a refrigerant comprising:

(i) a fluoropropene; and (ii) a hydrocarbon of formula CF ₃ (CH ₂ ) _π CF ₂ H, wherein n=l or 2

Compositions according to the invention have a suitable boiling point and high latent heat of evaporation, low toxicity, non-flammability, non-corrosivity, high stability and freedom from objectionable odour. In certain embodiments, component (i) may have an appreciably lower boiling point than that of component (ii), which may mean that the composition of the invention is capable of boiling and condensing over a relatively wide temperature range. This may provide the benefit that the coefficient of performance of the composition is relatively high, and it can exhibit a wide temperature glide in both the evaporator and condenser.

When the composition of the invention is to be used as a refrigerant, it may be combined with one or more hydrocarbons in an amount which is sufficient to allow the composition to transport a mineral oil or alkyl benzene type lubricant around a refrigeration circuit and return it to the compressor. In this way, inexpensive lubricants based on mineral oils or alkyl benzenes may be used to lubricate the compressor.

Suitable hydrocarbons for inclusion in the refrigerant composition of the invention are those containing from 2 to 6 carbon atoms, with hydrocarbons containing from 3 to 5 carbon atoms being preferred. Hydrocarbons that will not significantly alter the thermophysical properties of the refrigerant at the level at which they provide for oil transport, such as the linear and branched isomers of butane and pentane are particularly preferred, with pentane being especially preferred.

When a hydrocarbon is included, it will preferably be present in an amount of from 1 % to 10 % by weight on the total weight of the composition.

The refrigerant composition of the invention may also be used in combination with the types of lubricants which have been specially developed for use with

hydrofluorocarbon based refrigerants. Such lubricants include those comprising a polyoxyalkylene glycol base oil. Suitable polyoxyalkylene glycols include hydroxy! group initiated polyoxyalkylene glycols, e.g. ethylene and/or propylene oxide oligomers/polymers initiated on mono- or polyhydric alcohols such as methanol, butanol, pentaerythritol and glycerol. Such polyoxyalkylene glycols may also be end-capped with suitable terminal groups such as alkyl, e.g. methyl groups.

Another class of lubricants which have been developed for use with hydrofluorocarbon based refrigerants and which may be used in combination with the present refrigerant compositions are those comprising a neopentyl polyol ester base oil derived from the reaction of at least one neopentyl polyol and at least one aliphatic carboxylic acid or an esterifiable derivative thereof. Suitable neopentyl polyols for the formation of the ester base oil include pentaerythritol, polypentaerythritols such as di- and tripentaerythritol, trimethylol alkanes such as trimethylol ethane and trimethylol propane, and neopentyl glycol. The esters may be formed with linear and/or branched aliphatic carboxylic acids, such as linear and/or branched alkanoic acids. Preferred acids are selected from the Cs _-8 , particularly the C _5-7 , linear alkanoic acids and the C _5-10 , particularly the Cs _-9 , branched alkanoic acids. A minor proportion of an aliphatic polycarboxylic acid, e.g. an aliphatic dicarboxylic acid, may also be used in the synthesis of the ester in order to increase the viscosity thereof. Usually, the amount of the carboxylic acid(s) which is used in the synthesis will be sufficient to esterify all of the hydroxyl groups contained in the polyol, although residual hydroxyl functionality may be acceptable.

The single component refrigerants and azeotropic refrigerant blends which are used in conventional heat transfer devices boil at a constant temperature in the evaporator under constant pressure conditions, and so produce an essentially constant temperature profile across the evaporator. The temperature of the heat transfer fluid being cooled, which may be air or water for example, drops fairly rapidly on first contacting the cold surfaces provided by the refrigerant evaporating in the* evaporator, owing to the large difference in temperature

between that fluid and the evaporating refrigerant. However, since the temperature of the heat transfer fluid is progressively reduced as it passes along the length of the evaporator, there is a progressive reduction in the temperature differential between the fluid and the evaporating refrigerant, and a consequent reduction in the heat transfer or cooling rate.

In contrast, the refrigerant composition of the invention may be a non-azeotropic (zeotropic) composition which tends to boil over a wide temperature range under constant pressure conditions so as to create a temperature glide in the evaporator which can be exploited to reduce the energy required to operate the heat transfer device, e.g. by making use of the Lorentz cycle. One technique for exploiting the temperature glide involves the use of a heat transfer device equipped with a counter current flow evaporator and/or condenser in which the refrigerant and the heat transfer fluid are caused to flow counter currently to each other. With such an arrangement, it is possible to minimise the temperature difference between the evaporating and condensing refrigerant whilst maintaining a sufficiently high temperature difference between the refrigerant and the external fluid(s) to cause the required heat transfer to take place.

The consequence of minimising the temperature difference between the evaporating and condensing refrigerant in the same system is that the pressure difference is also minimised. As a result, the overall energy efficiency of the system is improved as less energy is consumed to bring about the refrigerant pressure rise from evaporator to condenser conditions.

This increase in the energy efficiency can be optimised by using a zeotropic refrigerant composition which boils and condenses over a temperature range which is equal or approximately equal to the temperature change to which the heat transfer fluid is to be subjected as it flows through the evaporator and condenser.

The composition of the present invention may be used to provide the desired cooling in heat transfer devices such as chillers by a method which involves condensing the composition and thereafter evaporating it in a heat exchange

relationship with a heat transfer fluid to be cooled. In particular, the composition of the invention may be employed as a replacement for refrigerant R-I l in chillers.

Preferably, the compositions according to the invention comprises 1% to 9% by weight component (a) (i.e. fluoropropene) and 99% to 1% by weight component (b) (i.e. a hydrocarbon of formula CF ₃ (CH ₂ ) _n CF ₂ H with n = 1 or 2), more preferably 1% to 50% component (a) and 99% to 50% component (b), more preferably 1% to 20% component (a) and 99% to 80% component (b), even more preferably 1% to 10% component (a) and 99% to 90% component (b).

In all instances the composition may optionally and preferably comprise 0.01% to 5% CO ₂ .

The present invention is now illustrated but not limited with reference to the following examples.

EXAMPLES

Example 1

Figure 1 shows how the boiling point varies of a mixture of R-1225 and R-245fa with a varying mass fraction of R-245fa, and demonstrates the ability of the fluid composition to meet the boiling point requirements identified.

Example 2

Table 1 shows the thermophysical properties of components and mixtures of fluids.

The performance of refrigerant compositions of the invention in a refrigeration cycle was evaluated using standard refrigeration cycle analysis techniques in order to assess the suitability thereof as a refrigerant, especially in relation to R245fa on its own. The operating conditions which were used for the analysis were chosen as being typical of those conditions which are found in a chiller or air conditioning

system, and counter current flow at the heat exchangers was assumed, in order to benefit from refrigerant glide.

The evaluation involved first defining the inlet and outlet temperatures of the heat transfer fluid, which could be air or water for example, at each heat exchanger (evaporator and condenser). The temperatures in the evaporator and condenser, assuming that a pure (single component) refrigerant was used in the cycle, were then chosen and these temperatures together with the inlet and outlet temperatures of the heat transfer fluid referred to above were used to determine a target log mean temperature difference for each heat exchanger. In the cycle analysis itself, the refrigerant inlet and outlet temperatures at both the evaporator and condenser were adjusted until the target log mean temperature difference was achieved for each heat exchanger. When the target log mean temperature difference for each heat exchanger was achieved, the various properties of the refrigerant composition in the cycle were recorded.

The following operating conditions were used in the cycle analysis.

Evaporator

Evaporator Temperature 5 ⁰ C

Inlet Temperature of Heat Transfer Fluid 2O ⁰ C

Outlet Temperature of Heat Transfer Fluid 12°C

Log Mean Temperature Difference for Evaporator 10.5 ⁰ C

Condenser

Condenser Temperature: 32 ⁰ C

Inlet Temperature of Heat Transfer Fluid 20 ⁰ C Outlet Temperature of Heat Transfer Fluid 3O ⁰ C

Log Mean Temperature Difference for Condenser 5.58°C

Amount of Superheat: 5 ⁰ C

Amount of Subcooling: 5°C

Isentropic Compressor Efficiency: 75%

Volumetric Flow through Compressor 1 m /s

The results of analysing the performance of the refrigerants compositions in a refrigeration cycle using these operating conditions are given in Table 1 in relation to R-245fa, which is provided by way of comparison.

The performance parameters of the refrigerant compositions which are presented in Table 1, i.e. condenser pressure, evaporator pressure, discharge temperature, refrigeration capacity (by which is meant the cooling duty achieved per unit swept volume of the compressor), coefficient of performance (COP) (by which is meant the ratio of cooling duty achieved to mechanical energy supplied to the compressor), and the glides in the evaporator and condenser (the temperature range over which the refrigerant composition boils in the evaporator and condenses in the condenser), are all art recognised parameters.

It is apparent from Table 1 that refrigerant compositions of the invention boil over a wide temperature range in the evaporator and condense over a wide temperature range in the condenser, i.e. they exhibit wide glide behaviour in both heat exchangers, and that this property can enhance the energy efficiency of the refrigeration process as is evident from the higher values recorded for the coefficient of performance for most of the refrigerant compositions of the invention as compared to R-245fa alone.

TABLEl