AU666694B2 - Compositions useful as refrigerants - Google Patents

Description

OPI DATE 03/08/93 APPLN. ID 31687/93 AOJP DATE 14/10/93 PCT NUMBER PCT/GB92/02382 I 1 1IIII Il11111 iAU9331687I I AU9331687 INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 5 (11) International Publication Number: WO 93/14173 CO9K 5/04 Al 9K 5/04 (43) International Publication Date: 22 July 1993 (22.07.93) (21) International Application Number: PCT/GB92/02382 (74) Agents: DEE, lan, Mark et al.; ICI Group Patents Services Dept., P.O. Box 6, Shire Park, Bessemer Road, (22) International Filing Date: 23 December 1992 (23.12.92) Welwyn Garden City, Hertfordshire AL7 IHD (GB).

Priority data: (81) Designated States: AU, BR, CA, JP, KR, US, European 9200521.4 10 January 1992 (10.01.92) GB patent (AT, BE, CH, DE, DK, ES, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE).

(71) Applicant (for all designated States except US): IMPERIAL CHEMICAL INDUSTRIES PLC [GB/GB]; Imperial Published Chemical House, Millbank, London SWIP 3JF With international search report.

(72) Inventors; and Inventors/Applicants (for US only) POWELL, Richard, Llewellyn [GB/GB]; 9 Sadler's Wells, Bunbury, Tarporley, Cheshire CW6 9NV MORRISON, James, David [GB/GB]; 12 Niddries Lane, Moulton, Northwich, Cheshire CW9 8QE (GB).

(54)Title: COMPOSITIONS USEFUL AS REFRIGERANTS (57) Abstract A refrigerant composition comprising a mixture of 1,1,1,2-tetrafluoroethane and at least one fluorinated ether selected from trifluoromethyl methyl ether and fluoromethyl trifluoromethyl ether is claimed.

W I WO 93/14173 PCT/GB92/02382 COMPOSITIONS USEFUL AS REFRIGERANTS.

The present invention relates generally to refrigerant compositions for cooling and heating applications and to the use of such compositions in heat transfer devices. More particularly, the present invention is concerned with refrigerant compositions which are designed to replace dichlorodifluoromethane (Refrigerant R-12).

Mechanical refrigeration systems and related heat transfer devices such as heat pumps and air-conditioning systems are well known. In such devices, a refrigerant liquid of a suitable boiling point evaporates at low pressure taking heat from a surrounding zone. The resulting vapour is then compressed and passed to a condenser where it condenses and gives off heat to a second zone, the condensate being returned through an expansion valve to the evaporator, so completing the cycle. The mechanical energy required for compressing the vapour and pumping the liquid may be provided by an electric motor or an internal combustion engine.

In addition to having a suitable boiling point and 4 a high latent heat of vaporisation, the properties preferred of a refrigerant include low toxicity, nonflammability, non-corrosivity, high stability and freedom from objectionable odour.

Hitherto, heat transfer devices have tended to use Sfully and partially halogenated chlorofluorocarbon refrigerants. Particular mention may be made of dichlorodifluoromethane (Refrigerant R-12) which possesses a suitable combination of properties and has for many years been the most widely used refrigerant.

WO 93/14173 PCT/G B92/02382 2 In recent years, however, there has been increasing international concern that the fully and partially halogenated chlorofluorocarbons may be damaging the earth's protective ozone layer and there is general agreement that their manufacture and use should be severely restricted and eventually phased out completely.

Whilst heat transfer devices of the type to which the present invention relates are essentially closed systems, loss of refrigerant to the atmosphere can occur due to leakage during operation of the equipment or during maintenance procedures. It is important, therefore, to replace fully and partially halogenated chlorofluorocarbon refrigerants by materials having substantially lower, preferably zero, ozone depletion potentials.

In addition to the possibility of ozone depletion, it has been suggested that significant concentrations of chlorofluorocarbon refrigerants in the atmosphere might contribute to global warming (the so-called greenhouse effect). It is desirable, therefore, to use refrigerants which have relatively short atmospheric lifetimes as a result of their ability to react with other atmospheric constituents such as hydroxyl radicals.

The present invention provides a refrigerant composition which may be used as a replacement for Refrigerant R-12. The composition contains refrigerant compounds which have essentially zero ozone depletion potentials and comparatively low direct global warming potentials.

Accordingly, the present invention provides a refrigerant composition comprising a mixture of 1,1.1,2-tetrafluoroethane (CF 3

CH

2 F) and at least one Wo 93/14173 PCT/GB92/02382 3 fluorinated ether selected from trifluoromethyl methyl ether (CF 3 0CH 3 and fluoromethyl trifluoromethyl ether

(CF

3

OCH

2

F).

Refrigerant composi-4ons in accordance with the present invention typictily contain from 5 to 95Z by weight of 1,1,1,2-tetrafluoroethane and from 95 to by weight of the ether. Additionally, the refrigerant compositions of the invention may contain other refrigerant compounds which have low and preferably zero ozone depletion potentials, for example other hydrofluoroalkanes and/or other fluorinated ethers containing residual hydrogen atoms. Examples of other hydrofluoroalkanes which may be incorporated in the refrigerant compositions of the invention include difluoromethane 1,1,1-trifluoroethane (R-143a), 1,1,2,2-tetrafluoroethane (R-134), pentafluoroethane (R-125) and 1,1-difluoroethane (R-152a). Examples of other fluorinated ethers which may be included in the refrigerant compositions of the invention are the fluorinated dimethyl ethers containing residual hydrogen atoms.

Although the refrigerant compositions of the invention may comprise other refrigerant compounds, the preferred refrigerant compositions of the invention consist essentially of 1.1,1,2-tetrafluoroethane and at least one fluorinated ether selected from trifluoromethyl methyl ether and fluoromethyl trifluoromethyl ether.

Although the refrigerant compositions of the invention may be zeotropic they are preferably azeotropic or azeotrope-like.

In one embodiment of the present invention, the refrigerant composition comprises a mixture of 1,1,1,2-tetrafluoroethane and fluoromethyl WO 93/14173 PCT/GB92/02382 4 trifluoromethyl ether. A specific composition of this type is one which consists essentially of the stated components. Such compositions will typically comprise from 25 to 75 Z by weight of 1,1,1,2-tetrafluoroethane and from 75 to 25 Z by weight of fluoromethyl trifluoromethyl ether. Refrigerant compositions of the invention comprising 1,1,1,2-tetrafluoroethane and fluoromethyl trifluoromethyl ether as essential components may suitably replace Refrigerant R-12 in many applications. However, such compositions may be particularly useful as a replacement for R-12 in heat pumps and automotive air conditioners. Heat pumps and automotive air conditioners operate with high discharge temperatures, typically around 80 OC, which tends to result in fairly high pressures in the condenser. By using blends of 1,1,1,2-tetrafluoroethane and fluoromethyl trifluoromethyl ether as the working fluid in such systems, it is possible to achieve lower condenser pressures at these high discharge temperatures than is possible when Refrigerant R-12 or 1,1,1,2-tetrafluoroethane (the generally accepted replacement for Refrigerant R-12) are used. Our research indicates that at a discharge temperature of 80 0 C a condenser pressure of around 17.7 bar is attainable when using a refrigerant composition comprising 25 Z by weight of 1,1,1,2-tetrafluoroethane and 75 Z by weight of fluoromethyl trifluoromethyl ether.

Table 1 shows the performance of a number of refrigerant compositions of the invention comprising 1,1,1,2-tetrafluoroethane (R-134a in the Table) and fluoromethyl trifluoromethyl ether (E-134a in the Table). The percentage by weight of each component in the refrigerant compositions evaluated is given in the hA WO 93/14173 PCT/GB92/02382 5 second row of the Table. Thus, refrigerant compositions respectively comprising 75 Z by weight of 1,1,1,2-tetrafluoroethane and 25 Z by weight of fluoromethyl trifluoromethyl ether; 50 Z by weight of 1,1,1,2-tetrafluoroethane and 50 Z by weight of fluoromethyl trifluoromethyl ether; and 25 Z by weight of 1,1,1,2-tetrafluoroethane and 75 Z by weight of fluoromethyl trifluoromethyl ether were evaluated. The operating conditions which were selected for the evaluation are representative of those existing in a domestic refrigeration system. Specifically, these conditions were as follows: Evaporator Temperature: -25 0

C

Condenser Temperature: 40 0

C

Superheat: 45 0

C

Subcooling: 10 0

C

Cooling Duty: 1 KW Isentropic Compressor Efficiency: 75 Z The performance parameters of the refrigerant compositions which are presented in the Table, i.e.

condenser pressure, evaporator pressure, discharge temperature, return gas temper'ture, volumetric flow, system efficiency (coefficient of performance, by which is meant the ratio of cooling duty achieved to mechanical energy supplied to the compressor), refrigeration capacity (cooling duty per unit swept volume of the compressor), and the glide in the evaporator (the temperature range over which the refrigerant composition boils in the evaporator), are all art recognised parameters.

The performance of Refrigerant R-12 and l1,1,2-tetrafluoroethane, which is the generally WO 93/14173 PCT/GB92/02382 6 accepted replacement for Refrigerant R-12, under identical operating conditions are also shown in Table 1 by way of comparison.

From Table 1, it is apparent that refrigerant compositions according to the invention comprising 1,1,1,2-tetrafluoroethane and fluoromethyl trifluoromethyl ether can exhibit a performance in a refrigeration system which is not too far removed from that of Refrigerant R-12. Furthermore, the glide in the evaporator was only 0.2 0 C for all the mixed refrigerant compositions evaluated showing that such compositions are azeotrope like.

In a preferred embodiment of the present invention, the refrigerant composition comprises a mixture of 1,1,1,2-tetrafluoroethane and trifluoromethyl methyl ether, optionally together with fluoromethyl trifluoromethyl ether and/or at least one other fluorinated ether containing residual hydrogen atoms and/or at least one other hydrofluoroalkane.

Particularly preferred refrigerant compositions are mixtures consisting essentially of 1,1,1,2-tetrafluoroethane and trifluoromethyl methyl ether.

Refrigerant compositions comprising a mixture of 1,1,1,2-tetrafluoroethane and trifluoromethyl methyl ether have been found to exhibit a similar performance to Refrigerant R-12 in a refrigeration cycle. In consequence, such compositions may be used in place of Refrigerant R-12 which is at present widely used as a working fluid in refrigeration systems and related heat transfer devices. Furthermore, compositions comprising 1,1,1,2-tetrafluoroethane and trifluoromethyl methyl ether benefit from the particularly short atmospheric lifetime of trifluoromethyl methyl ether (ca 3.6 years) WO 93/1'4173 PCT/GB92/02382 7and, thus, can exhibit a low direct global warming potential.

Preferred ref3igerant compositions based on 1,1,1,2-tetrafluoroethane and trifluoromethyl methyl ether comprise from 5 to 75 Z by weight of 1,1,1,2-tetrafluoroethane and from 95 to 25 Z by weight of trifluoromethyl methyl ether. Particularly preferred refrigerant compositions of this type comprise from to 60 Z by weight of 1,1,1,2-tetrafluoroethane and from to 40 Z by weight of trifluoromethyl methyl ether, with compositions comprising from 25 to 50 Z by weight of 1,1,1,2-tetrafluoroethane and from 75 to 50 Z by weight of trifluoromethyl methyl ether being especially preferred. The preferred compositions are therefore characterised by the presence of a substantial amount of trifluoromethyl methyl ether which confers on the composition a lower direct global warming potential.

However, surprisingly such compositions also exhibit a performance in a refrigeration system which is comparable to Refrigerant R-12.

Trifluoromethyl methyl ether is slightly flammable and our research suggests that mixed refrigerant compositions comprising in excess of 40 Z by weight of 25 this ether and less than 60 Z by weight of 1,1,1,2-tetrafluoroethane may also be flammable. It is believed that the potential flammability of such refrigerant compositions may not be a problem in practice, bearing in mind that heat transfer devices are essentially closed systems and that certain devices, such as domestic refrigeration systems, only contain small quantities of the refrigerant. Moreover, the benefit of using a refrigerant composition comprising a large amount of trifluoromethyl methyl ether opposite reduced global warming potential may WO 93/14173 PCT/GB92/02382 -8 outweigh any possible disadvantage opposite flammability. However, if flammability is a concern, then compositions containing from 70 to 95 Z by weight of 1,1,1,2-tetrafluoroethane and from 30 to 5 Z by weight of trifluoromethyl methyl ether are preferred, with compositions containing from 70 to 85 Z by weight of 1,1,1,2-tetrafluoroathane and from 30 to 15 Z by weight of trifluoromethyl methyl ether being particularly preferred, in view of their non-flammability.

Table 2 shows the performance of a number of refrigerant compositions of the invention comprising 1,1,1,2-tetrafluoroethane (R-134a in the Table) and trifluoromethyl methyl ether (E-143a in the Table). The percentage by weight of each component in the refrigerant compositions evaluated is given in the second row of the Table. Thus, refrigerant compositions respectively comprising 75 Z by weight of 1,1,1,2-tetrafluoroethane and 25 Z by weight of trifluoromethyl methyl ether; 50 Z by weight of 1,1,1,2-tetrafluoroethane and 50 Z by weight of trifluoromethyl methyl ether: and 25 Z by weight of 1,1,1,2-tetrafluoroethane and 75 Z by weight of trifluoromethyl methyl ether were evaluated. The operating conditions which were selected for the evaluation are representative of those existing in a domestic refrigeration system. Specifically, these conditions were as follows: Evaporator Temperature: -25 0

C

Condenser Temperature: 40 0

C

Superheat: 45 0

C

Subcooling: 10 0

C

Cooling Duty: 1 KW WO93/14173 PCT/GB92/02382 9 Isentropic Compressor Efficiency: 75 Z The performance parameters of the refrigerant compositions which are presented in the Table, i.e.

condenser pressure, evaporator pressure, discharge temperature, return gas temperature, volumetric flow, system efficiency (coefficient of performance, by which is meant the ratio of cooling duty achieved to mechanical energy supplied to the compressor), refrigeration capacicy (cooling duty per unit swept volume of the compressor), and the glide in the evaporator (the temperature range over which the refrigerant composition boils in the evaporator), are all art recognised parameters.

The performance of Refrigerant R-12 and 1,1,1,2-tetrafluoroethane, which is the generally accepted replacement for Refrigerane R-12, under identical operating conditions are also shown in Table 2 by way of comparison.

From Table 2, it is apparent that refrigerant compositions according to the invention comprising 1,1,1,2-tetrafluoroethane and trifluoromethyl methyl ether can exhibit a performance in a refrigeration system which is comparable to that of Refrigerant R-12.

Furthermore, the glide in the evaporator was essentially zero for all the mixed refrigerant compositions tested showing that such compositions are 1 azeotrope like.

The refrigerant compositions of the invention may be prepared by a simple mixing process.

The compositions are useful in all types of compression cycle heat transfer devices. Thus, they may be used to provide cooling by a method involving condensing the refrigerant composition and thereafter WO 93/14173 PCT/GB92/02382 10 evaporating it in a heat exchange relationship with a body to be cooled. They may also be used to provide heating by a method involving condensing the efrigerant composition in a heat exchange relationship with a body to be heated and thereafter evaporating it.

The compositions of the invention provide a good compromise between capacity and efficiency combined with low atmospheric lifetime and essentially zero ozone depletion. They are especially suitable for applications currently satisfied by Refrigerant R-12, for example domestic refrigeration, automobile air-conditioning and refrigerated food transport.

i .i i i WO 93/14173 PCT/GB92/02382 11 TABLE 1 REFRIGERANT R-12 R-134a R-134a/E-134a 2 BY WEIGHT 100 100 75/25 50/50 25/75

CONDENSER

PRESSURE (Bar) 9.60 10.10 9.04 8.07 7.28

EVAPORATOR

PRESSURE (Bar) 1.23 1.07 1.01 0.94 0.88

DISCHARGE

TEMPERATURE (OC) 120.8 110.9 106.5 100.8 96.2 RETURN GAS TEMPERATURE (OC) 20.0 20.0 20.1 20.1 20.1

VOLUMETRIC

FLOW (M 3 /s x 102) 0.140 0.150 0.169 0.187 0.206 COOLING DUTY PER UNIT SWEPT VOLUME (KW/m 3 714 667 592 534 485 COEFFICIENT OF PERFORMANCE 1.90 1.86 1.87 1.86 83 BOILING BP* -29.8 -26.2 -25.31 -23.91 POINT (OC) DP** -29.8 -26.2 -25.07 -23.51 -22.26 GLIDE IN EVAPORATOR (OC) 0 0 0.2 0.2 0.2 BP Bubble Point DP Dew Point

-A

lllll~ l~ ll:i WO 93/14173 PCT/GB92/02382 12 TABLE 2 REFRIGERANT R-12 R-134a R-134a/E-143a Z BY WEIGHT 100 100 75/25 50/50 25/75

CONDENSER

PRESSURE (Bar) 9.60 10.10 9.58 9.20 8.85

EVAPORATOR

PRESSURE (Bar) 1.23 1.07 1.02 1.00 0.97

DISCHARGE

TEMPERATURE (OC) 120.8 110.9 110.0 107.5 105.1 RETURN GAS TEMPERATURE (OC) 20.0 20.0 20.0 20.0 20.0

VOLUMETRIC

FLOW (M 3 /s x 102) 0.140 0.150 0.162 0.170 0.176 COOLING DUTY PER UNIT SWEPT VOLUME (KW/m 3 714 667 617 588 568 COEFFICIENT OF PERFORMANCE 1.90 1.86 1.85 1.85 1.85 BOILING BP* -29.8 -26.2 -25.61 -24.94 -24.45 POINT (OC) DP** -29.8 -26.2 -25.54 -24.88 -24.42 LIDE IN EVAPORATOR 0 0 0 0 0 BP Bubble Point DP Dew Point Ls

Claims (7)

1. A refrigerant composition including a mixture of 1,1,1,2-tetrafluoroethane and fluoromethyl trifluoromethyl ether.

2. A refrigerant composition as claimed in claim 1, including from 5 to 95% by weight of 1,1,1,2-tetrafluoroethane and from 95 to 5% by weight of fluoromethyl trifluoromethyl ether.

3. A refrigerant composition as claimed in claim 2, including from 25 to by weight of 1,1,1,2-tetrafluoroethane and from 75 to 25% by weight of fluoromethyl trifluoromethyl ether.

4. A heat transfer device containing a refrigerant composition as claimed in any one of claims 1 to 3. A method for providing cooling which includes condensing the refrigerant composition claimed in any one of claims 1 to 3 and thereafter evaporating it in a heat exchange relationship with a body to be cooled.

6. A method for providing heating which includes condensing the refrigerant composition claimed in any one of claims 1 to 3 in a heat exchange relationship with a body to be heated and thereafter evaporating it.

7. The use of a refrigerant composition as claimed in any one of claims 1 to 3 as a replacement for refrigerant R-12 in a heat transfer device. S 20 8. A refrigerant compositior according to claim 1 substantially as hereinbefore described with reference to any one of the Examples. DATED: 18 December, 1995 PHILLIPS ORMONDE FITZPATRICK Attorneys For: IMPERIAL CHEMICAL INDUSTRIES PLC C 208 erieatcmosto acodn ocai usanilya ab C:WINWORD\ANfDREARLIER31I687CL,DOC INTERNATIONAL SEARCH REPORT InternatIDna Application No PCT/GB 92/02382 1. CLASSIFICATION OF SUBJECT MATT'E (if several classificatin symabols apply, Indicate all)' According to Intosnational Patent Classification (IPC) or to both National Classification and IPC Int.C1. 5 CO9K5/04 II. FIELDS SEAChED Minimum Documentation Searched 7 Classification System Classification Symbols Int.C1. 5 C09K Documentation Searched other than Minimum Documentation to the Extent that such Documents are Included In the Fields Searchedl III. DOCUMENTS CONSIDERED TO BE RELEVANT9 category 0 Citation of Document, 11 with Indication, where appropriate, of the relevant passages' RZIelevant to Claim No.0 A WO,A,9 113 968 (DU PONT DE NEMOURS) 1-14 19 September 1991 see the whole document A EP,A,0 385 737 (W.R.GRACE &CO) 1,2,4, September 1990 10,13,14 see the whole document P,A DATABASE WPIL 1,11,12 Week 9221, Derwent Publications Ltd., London, GB; AN 92-172537 JP,A,4 110 386 (DAIKIN KOGYO) 10 April 1992 see abstract aSpecial categories of cited documents later document published after the International filing date docurment defining the generai state of the art wich isntctdto understand the principie or theory undrynth considered to be of particuiar emo@nc Isnvenrtpioniydt n o ncnlctwt h plcto u oEo earlier documaent but published on or after the International document of particlar relevance; the claimed invention f'lung date cannot be considered novel or cannot be considered to 'V document which may throw doubts on priority claim(s) or Involve an inventive step wbich Is cted to establish the publication date of ante 'Y document of particular relevance; the claimed Invention citation or other specil reason (as specified) cannot be considered to Invoive an inventive step when the 0' document referring to an oral disclosure, use, exhibition or document Is combined with one or more other such docu- other means ments, such combination being obvious to a person skilled 'p document published prior to the International filing date but In the a&t later than the priority date dlaimed W. document member of the same patent family IV. CERTIFICATION Date of the Actual Completion of the International Search Date of Mailing of this International Search Report: 08 MARCH 1993

230._ Inteonational Searching Authority Signature of Authorized Officer EUROPEAN PATENT OFFICE PUETZ C. Fern PCTIISAzao ("Cewied (Janar 1 9"WS ANNEX TO THE INTERNATIONAL SEARCH REPORT ON INTERNATIONAL PATENT APPLICATION NO. 9202382 68124 This annex fists the patent family members relating to the patent doczuents cited in the above-mentioned international search rMOMt The members are as contained in the European Patent Office EDP file on The European Patent Office is in no way liable for then particulars which are merely given for dhe purpose of information. 08/03/93 Patent document Publication Pritent family Publication cited in search report dIt member(s) Idate WO-A-9113968 19-09-91 EP-A- 0519948 30-12-92 EP-A-0385737 05-09-90 US-A- 4961321 09-10-90 AU-B- 614215 22-08-91 AU-A- 4929990 06-09-90 CA-A- 2008862 3 1-08-90 JP-A- 2248490 04-10-90 1*9 For more details about this annex sewe Official Journal of the European Patent Office, No. 12182