WO1996003472A1

WO1996003472A1 - Refrigerant compositions

Info

Publication number: WO1996003472A1
Application number: PCT/GB1995/001717
Authority: WO
Inventors: Richard Llewllyn Powell; Stuart Corr; Frederick Thomas Murphy; James David Morrison
Original assignee: Imperial Chemical Industries Plc
Priority date: 1994-06-27
Filing date: 1995-07-20
Publication date: 1996-02-08
Also published as: AU2987495A; GB9415076D0

Abstract

A refrigerant composition is described which comprises (A) at least one hydrofluorocarbon selected from the group consisting of difluoromethane (R-32) and 1,1,1-trifluoroethane (R-143a), (B) pentafluoroethane (R-125), (C) perfluoropropane (R-218), and optionally (D) at least one hydrofluorocarbon selected from the group consisting of 1,1,1,2-tetrafluoroethane (R-134a) and 1,1,2,2-tetrafluoroethane (R-134).

Description

REFRIGERANT COMPOSITIONS

This invention relates to refrigerant compositions and to the use of such compositions in heat transfer devices such as refrigeration and air conditioning systems. The invention relates, in particular, to refrigerant compositions which can be used in the air conditioning and low temperature refrigeration applications currently satisfied by chlorodifluoromethane (refrigerant R-22) and the azeotropic mixture of chlorodifluoromethane and chloropentafluoroethane (refrigerant R-l 15); the azeotrope being refrigerant R-502.

Heat transfer devices of the mechanical compression type such as refrigerators, freezers, 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 heat transfer fluid. The resulting vapour is then compressed and passes to a condenser where it condenses and gives off heat to another heat transfer fluid. The condensate is then 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 a high latent heat of vaporisation, the properties preferred for a refrigerant include low toxicity, non-flammability, non-corrosivity, high stability and freedom from objectionable odour.

Hitherto, heat transfer devices have tended to use fully and partially halogenated chlorofluorocarbon refrigerants such as trichlorofluoromethane (refrigerant R-l 1), dichlorodifluoromethane (refrigerant R-l 2), chlorodifluoromethane (refrigerant R-22) and the azeotropic mixture of chlorodifluoromethane and chloropentafluoroethane (refrigerant R-l 15); the azeotrope being refrigerant R-502. In particular, refrigerant R-22 has found widespread use in air conditioning and low temperature refrigeration applications while refrigerant R-502 has been widely used in low temperature refrigeration applications.

However, the fully and partially halogenated chlorofluorocarbons have been implicated in the destruction of the earth's protective ozone layer and as a result the use and production thereof has been limited by international agreement. 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 low or zero ozone depletion potentials.

Replacements for some of the chlorofluorocarbon refrigerants presently in use have already been developed. These replacement refrigerants tend to comprise selected hydrofluoroalkanes, i.e. compounds which contain only carbon, hydrogen and fluorine atoms in their structure. Thus, refrigerant R-l 2 is generally being replaced by 1,1,1 ,2-tetrafluoroethane (R- 134a).

Although suitable replacement refrigerants exist, there is always a need for new replacement refrigerants that have the required low or zero ozone depletion potential and, in particular, there is a need for new replacement refrigerants which can exhibit a better performance than the replacement refrigerants known in the art. The present invention provides a refrigerant composition comprising a mixture of compounds having low or zero ozone depletion potentials which can be used in the air conditioning and low temperature refrigeration applications currently satisfied by refrigerants R-22 and R-502.

According to the present invention there is provided a refrigerant composition comprising:

(A) at least one hydrofluorocarbon selected from the group consisting of difluoromethane (R-32) and 1,1,1-trifluoroethane (R-143a);

(B) pentafluoroethane (R-125);

(C) perfluoropropane (R-218); and optionally (D) at least one hydrofluorocarbon selected from the group consisting of

1,1,1 ,2-tetrafluoroethane (R- 134a) and 1 , 1 ,2,2-tetrafluoroethane (R- 134). The refrigerant composition of the invention comprises at least components A to C. Components (B) and (C) are pentafluoroethane (R-125) and perfluoropropane (R-218) respectively. Component (A) comprises at least one hydrofluorocarbon selected from the group consisting of difluoromethane (R-32) and 1,1,1-trifluoroethane (R-143a). Although component (A) may be a mixture of R-32 and R-l 43 a, it will preferably contain just one of these compounds and more preferably will contain just R-32.

The refrigerant composition of the invention may also contain a fourth component (component (D)) which comprises at least one hydrofluorocarbon selected from the group consisting of 1,1,1,2-tetrafluoroethane (R-134a) and 1,1,2,2-tetrafluoroethane (R-134). Although component (D) may be a mixture of R-134a and R-134, it will preferably contain just one of these compounds and more preferably will contain just R-l 34a.

The amounts of the various components in the refrigerant composition may be varied within wide limits, but typically the refrigerant composition will comprise from 5 to 60 % by weight of component (A), from 2 to 70 % by weight of component (B), from 5 to 80 % by weight of component (C) and from 0 to 60 % by weight (for example, from 2 to 60 % by weight) of component (D).

Refrigerant compositions of the invention which do not include the optional component (D) may be used as a replacement for refrigerant R-22 and will preferably comprise from 20 to 60 % by weight, more preferably from 30 to 55 % by weight, of component (A), from 20 to 60 % by weight, more preferably from 30 to 55 % by weight, of component (B) and from 5 to 25 % by weight, more preferably from 5 to 20 % by weight, of component (C). Refrigerant compositions of the invention which include the optional component

(D), particularly compositions which include R-l 34a, may be usefully employed as a replacement for refrigerant R-502 and will preferably comprise from 10 to 40 % by weight, more preferably from 15 to 35 % by weight, of component (A), from 2 to 30 % by weight, more preferably from 2 to 25 % by weight, of component (B), from 15 to 45 % by weight, more preferably from 20 to 40 % by weight, of component (C) and from 20 to 50 % by weight, more preferably from 25 to 45 % by weight, of component (D). An especially preferred refrigerant composition of the invention for replacing R-502 is one comprising from 20 to 30 % by weight R-32, from 5 to 20 % by weight R-125, from 25 to 35 % by weight R-218 and from 30 to 40 % by weight R-l 34a. The refrigerant composition of the invention may also be combined with one or more hydrocarbon compounds in an amount which is sufficient to allow the composition to transport a mineral oil or al yl 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 use with the refrigerant compositions of the invention are those containing from 2 to 6 carbon atoms, with hydrocarbons containing from 3 to 5 carbon atoms being preferred. Propane and pentane are particularly preferred hydrocarbons, with pentane being especially preferred.

Where a hydrocarbon is combined with the refrigerant composition of the invention, it will preferably be present in an amount of from 1 to 10 % by weight on the total weight of the refrigerant 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 hydroxyl 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 C5-8, particularly the C5-7, linear alkanoic acids and the C5-10, particularly the C5-9, 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 refrigerant composition of the present invention may be used to provide the desired cooling in heat transfer devices such as air conditioning and low temperature refrigeration systems by a method which involves condensing the refrigerant composition and thereafter evaporating it in a heat exchange relationship with a heat transfer fluid to be cooled. The refrigerant composition of the invention may be employed as a replacement for refrigerant R-22 in air conditioning and low temperature refrigeration applications or, more particularly, as a replacement for R-502 in low temperature refrigeration applications.

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

Example 1

The performance of four refrigerant compositions of the invention in a low temperature refrigeration cycle was investigated using standard refrigeration cycle analysis techniques in order to assess the suitability thereof as a replacement for R-502. The following refrigerant compositions were subjected to the cycle analysis:

(1) A composition comprising 20 % by weight R-32, 10 % by weight R-125, 30 % by weight R-218 and 40 % by weight R-l 34a.

(2) A composition comprising 30 % by weight R-32, 5 % by weight R-125, 30 % by weight R-218 and 35 % by weight R-l 34a. (3) A composition comprising 20 % by weight R-32, 20 % by weight R-125, 30 % by weight R-218 and 30 % by weight R-l 34a. (4) A composition comprising 25 % by weight R-32, 5 % by weight R-125, 30 % by weight R-218 and 40 % by weight R-l 34a.

The following operating conditions were used in the cycle analysis. Mean Evaporator Temperature: -45°C

Mean Condenser Temperature: 55°C

Amount of Superheat : 10°C Amount of Subcooling: 5°C

Isentropic Compressor Efficiency: 100 %

Cooling Duty: 1 kW

The results of analysing the performance of the four refrigerant compositions in a low temperature refrigeration cycle using these operating conditions are given in Table 1. 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 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-502 under the same operating conditions is also shown in Table 1 by way of comparison. It is apparent from Table 1 that the refrigerant compositions tested exhibited a performance in a low temperature refrigeration cycle which could make them an acceptable replacement for refrigerant R-502.

Claims

Claims:

1. A refrigerant composition comprising:

(A) at least one hydrofluorocarbon selected from the group consisting of difluoromethane and 1,1,1 -trifluoroethane; (B) pentafluoroethane; and (C) perfluoropropane.

2. A refrigerant composition as claimed in claim 1 wherein component (A) is difluoromethane.

3. A refrigerant composition as claimed in claim 1 or claim 2 which comprises from 20 to 60 % by weight of component (A), from 20 to 60 % by weight of component (B) and from 5 to 25 % by weight of component (C).

4. A refrigerant composition as claimed in claim 3 which comprises from 30 to 55 % by weight of component (A), from 30 to 55 % by weight of component (B) and from 5 to 20 % by weight of component (C).

5. A refrigerant composition comprising:

(A) at least one hydrofluorocarbon selected from the group consisting of difluoromethane and 1,1,1 -trifluoroethane;

(B) pentafluoroethane;

(C) perfluoropropane; and optionally (D) at least one hydrofluorocarbon selected from the group consisting of 1,1,1 ,2-tetrafluoroethane and 1 , 1 ,2,2-tetrafluoroethane.

6. A refrigerant composition as claimed in claim 5 wherein component (A) is difluoromethane.

7. A refrigerant composition as claimed in claim 5 or claim 6 which comprises from 5 to 60 % by weight of component (A), from 2 to 70 % by weight of component (B), from 5 to 80 % by weight of component (C) and from 0 to 60 % by weight of component (D).

8. A refrigerant composition as claimed in claim 5 or claim 6 which comprises the optional component (D).

9. A refrigerant composition as claimed in claim 7 which comprises the optional component (D) in an amount of from 2 to 60 % by weight on the total weight of the refrigerant composition.

10. A refrigerant composition as claimed in claim 8 which comprises from 10 to 40 % by weight of component (A), from 2 to 30 % by weight of component (B), from 15 to 45 % by weight of component (C) and from 20 to 50 % by weight of component

(D).

11. A refrigerant composition as claimed in claim 10 which comprises from 15 to 35 % by weight of component (A), from 2 to 25 % by weight of component (B), from 20 to 40 % by weight of component (C) and from 25 to 45 % by weight of component

(D).

12. A refrigerant composition as claimed in any one of claims 8 to 1 1 wherein component (D) is 1,1,1,2-tetrafluoroethane.

13. A refrigerant composition comprising from 20 to 30 % by weight difluoromethane, from 5 to 20 % by weight pentafluoroethane, from 25 to 35 % by weight perfluoropropane and from 30 to 40 % by weight 1,1,1,2-tetrafluoroethane.

14. A refrigeration or air conditioning system containing a refrigerant composition as claimed in any one of claims 1 to 13.

15. The use in a refrigeration or air conditioning system of a refrigerant composition as claimed in any one of claims 1 to 13.

16. A method for providing cooling which comprises condensing a refrigerant composition as claimed in any one of claims 1 to 13 and thereafter evaporating it in a heat exchange relationship with a fluid to be cooled.