GB2557240A

GB2557240A - Heat transfer fluid

Info

Publication number: GB2557240A
Application number: GB1620421.6A
Authority: GB
Inventors: Robinson Lloyd
Original assignee: Trio Gas Products Ltd
Current assignee: Trio Gas Products Ltd
Priority date: 2016-12-01
Filing date: 2016-12-01
Publication date: 2018-06-20
Also published as: GB201620421D0

Abstract

A heat transfer fluid comprises a first component comprising (a) a C1-C6 tetrafluoroalkane and (b) a C1-C6 tetrafluoroalkene; and a second component comprising (c) a C1-C6 difluoroalkane and (d) a C2-C6 pentafluoroalkane. The heat transfer fluid is for use in air conditioning units and the like and makes use of particular compounds which do not significantly promote ozone damage or global warming, but which show comparable heat transfer properties to CFCs at similar pressures to those systems previously utilising CFCs. Specifically, the heat transfer fluid may comprise tetrafluoroethane and tetrafluoropropene used in conjunction with difluoromethane and pentafluoroethane.

Description

(54) Title of the Invention: Heat transfer fluid Abstract Title: Heat transfer fluids (57) A heat transfer fluid comprises a first component comprising (a) a Ci-C₆ tetrafluoroalkane and (b) a Ci-C₆tetrafluoroalkene; and a second component comprising (c) a Ci-C₆ difluoroalkane and (d) a C₂-C₆pentafluoroalkane. The heat transfer fluid is for use in air conditioning units and the like and makes use of particular compounds which do not significantly promote ozone damage or global warming, but which show comparable heat transfer properties to CFCs at similar pressures to those systems previously utilising CFCs. Specifically, the heat transfer fluid may comprise tetrafluoroethane and tetrafluoropropene used in conjunction with difluoromethane and pentafluoroethane.

HEAT TRANSFER FLUID

FIELD OF THE INVENTION

The invention relates to a heat transfer fluid, in particular; a fluid for use in heat transfer applications, such as cooling; use of said fluid in heat transfer applications; and heat transfer devices comprising said fluid.

BACKGROUND OF THE INVENTION

An air conditioner (or air conditioning unit or air con or AC, as it is often referred to) is an example of a heat transfer device used to modify the conditions of an atmosphere, typically where the air in an environment is cooled and optionally dehumidified. The apparatus can be integral to a given environment (e.g. forming part of the ventilation system of a building or the climate controls of a vehicle) or may be a self-contained unit which can be deployed to a particular environment. Heat transfer devices of this kind process the air of an environment, typically cooling the air (though in some applications can provide heating) by bringing incoming air into thermal communication with a heat transfer fluid system. The heat transfer fluid, once it has absorbed the heat from the incoming air, is then moved to a heat sink where the heat is released.

A number of different heat transfer fluids have been used over the years in air conditioning and refrigeration systems. Of particular note are chlorofluorocarbons sometimes referred to as CFCs. As is well-known, CFCs are very damaging to the earth's ozone layer and contribute to global warming. Therefore, CFCs have been gradually phased out of use in countries around the world. Accordingly, various substitute fluids have been developed, without the negative environmental side-effects, as replacement for CFCs. A common fluid mixture that has been used to replace traditional CFCs is a mixture of difluoromethane (CH2F2, often in the industry referred to as R32) and pentafluoroethane (CHF2CF3, often in the industry referred to as R125). This particular gas mixture (often referred to in the industry as R410A) performs well as a heat transfer fluid and is less damaging to the environment. However, in order to achieve comparable properties to their CFC counterparts, it is often the case that heat transfer devices using CFC replacement fluids, must be operated at higher pressures. For instance, R410A is conventionally used in systems at pressures approximately 35% higher than those of an equivalent system using CFCs.

This is disadvantageous for a number of reasons. Firstly, operating systems at higher pressure requires more energy and therefore reduces the overall efficiency of a heat transfer device. Higher pressures also place greater demands on the structural integrity of a heat transfer device and increase the rate of wear and tear. Furthermore, operating systems at high pressures often leads to an increase in the amount of leakage from a system, which wastes heat transfer fluid. In addition, retrofitting older heat transfer devices with new (more environmentally friendly) heat transfer fluids often requires the incorporation of a compressor which increases the cost of recycling older equipment.

A typical example of a gas used to replace CFCs is 1,1,1,2-tetrafluoroethane (CF3CFH2 often referred to in the industry as R134A). CF3CFH2 is primarily used as a hightemperature refrigerant for domestic refrigeration and previously in automobile air conditioners. CF3CFH2 is a replacement for dichlorodifluoromethane (often referred to in the industry as R.12 or Freon 12). CF3CFH2 works at low vapour pressures which limits the refrigeration capacity of these compounds alone. Another gas which has been proposed as a replacement for CFCs is the hydrofluoroolefin 2,3,3,3 tetrafluoropropene (CH₂=CFCF₃, often referred to in the industry as R1234ze). This colourless gas has been proposed as a replacement for CF3CFH2 as a refrigerant in automobile air conditioners as it has been shown to have minimal environmental impact, having a global warming potential (GWP) rating one 335th that of CF3CFH2 and an atmospheric lifetime of about 400 times shorter. That said, such gases still must be pressurized in order to provide optimal heat transfer properties.

Accordingly, what is desired is an effective heat transfer fluid which can be used in heat transfer devices at low pressures and without the negative environmental properties of CFCs.

The invention is intended to overcome or at least ameliorate the above problems.

SUMMARY OF THE INVENTION

There is provided in the first aspect of the invention, a heat transfer fluid comprising: a first component, present in an amount greater than 85% wt., comprising; (a) a C1-C6 tetrafluoroalkane, and (b) a C1-C6 tetrafluoroalkene; and a second component, present in an amount less than 15% wt., comprising; (c) a C1-C6 difluoroalkane, and (d) a C2-C6 pentafluoroalkane.

The inventors have surprisingly found that making use of a two-component system containing the above claimed components leads to a surprising improvement in the efficiency of a heat transfer system. In particular, when a small amount of the second component is introduced into the first component, excellent heat transfer properties are achieved at pressures similar to those of CFC alternatives. The net result of this is that more efficient heating results. The magnitude of improvement is particularly surprising as the observed performance results in cost savings of up to 62% with the addition of only a relatively small amount of second component to first component when compared with existing industry standards.

The term heat transfer fluid is intended to refer to a liquid or gas which is used to absorb or dissipate heat. Such fluids are typically used to absorb heat from a first region of a system and dissipate heat from a second region of the system. A classic example of this would be, for instance, a refrigerator in which the heat transfer fluid passes through the fluid circuit, in thermal communication with a heat sink and chilled internal cabinet, in such a way as to extract heat from within the cabinet (where food is kept) and release heat to a heat sink. Whether or not the heat transfer fluid is a liquid or gas depends largely on the temperatures involved and the pressures at which the system is operated. It is conceivable that the fluid could be a combination of both liquid and gas depending on how a particular heat transfer device is operated. However, it is typically the case that the heat transfer fluid is a gas.

It is typically the case that component (a) is tetrafluoroethane, in particular 1,1,1,2tetrafluoroethane (CF3CFH2). Furthermore, it is also the case that element (b) is tetrafluoropropene, in particular 2,3,3,3-tetrafluoropropene (CH2=CFCF3). The inventors have found that these two components function well as ingredients of the first component of the heat transfer fluid.

Typically, the ratio of (a) to (b) is in the range of 1:2 to 2:5 by weight. It is often the case that the ratio of (a) to (b) is in the range of 1:2.2 to 1:2.3 by weight.

It is typically the case that (a) is present in an amount in the range of 30 wt.% to 40 wt.%. Further, it is often the case that (b) is present in an amount in the range of 50 wt.% to 60 wt.%. Unless otherwise stated herein, references to the percentage of the component of the composition is intended to refer to the weight percentage of the total composition.

Turning to the second component of the invention, (c) is typically difluoromethane (CF2H2). In addition, it is often the case that (d) is pentafluoroethane (CF3CF2H). The inventors have found that making use of these compounds as elements (c) and (d) results in a surprising improvement in the properties of the heat transfer fluid as compared to those currently prevalent in industry.

Any mixture of elements (c) and (d) may be possible in the second component of the composition. However, the ratio of (c) to (d) is typically in the range of 2:3 to 3:2 by weight. However, it is often the case that this ratio is in the range 4:5 to 5:4 by weight and typically, the ratio of (c) to (d) is often 1:1 by weight. In one preferred embodiment, the second component comprises a mixture of 40 wt.% to 60 wt.% difluoromethane and from 60 wt.% to 40 wt.% pentafluoroethane. More typically, the mixture comprises from 45 wt.% to 55 wt.% difluoromethane and from 55 wt.% to 45 wt.% pentafluoroethane.

In the heat transfer fluid of the invention, it is typically the case that (c) is present in an amount in the range of 2.5 wt.% to 10 wt.%, more typically 3 wt.% to 8 wt.%, and even more typically, 3.5 wt.% to 5 wt.%.

In the heat transfer fluid of the invention, it is typically the case that (d) is present in an amount in the range of 2.5 wt.% to 10 wt.%, more typically, 3 wt.% to 8 wt.%, and even more typically, 3.5 wt.% to 5 wt.%. The inventors have found that these particular ratios and absolute quantities of the described compounds of the second component result in significant improvements in the heat transfer properties of the fluid as compared to those currently prevalent in the industry.

It is typically the case that the first component of the heat transfer fluid is present in an amount greater than 90 wt.% by weight of the total composition of the gas. Further, it is also the case that the second component is typically present in an amount of less than 10 wt.% by weight with respect to the total mass of the heat transfer fluid.

The heat transfer fluid of the invention may include further additives. For instance, inert odorous fluids may be incorporated into the heat transfer fluid of the invention in order to aid in the detection of leaks. The fluid of the invention may further comprise one or more dyes. There is no particular restriction on the choice of additive, provided that the additive does not (or at least negligibly does) adversely interfere with the action of the heat transfer fluid. Catalysts and other additives that promote the heat transfer properties of the fluid of the invention may also be used. Antimicrobial or cleaning agents may also be introduced into the fluid.

There is also provided in a second aspect of the invention, a heat transfer device comprising the fluid according to the first aspect of the invention.

The term heat transfer device is intended to refer to any device adapted to heating or cooling a particular environment, using a cyclable fluid circuit. There is no particular restriction on the types of heat transfer device with which the fluid of the first aspect of the invention may be used. However, typical examples include refrigerators, air conditioning units, heat pumps, centrifugal chillers and combinations thereof. Most typically, the heat transfer device is an air conditioning system.

The heat transfer device may include a compressor. There is no particular restriction on the type of compressor with which the heat transfer fluid of the invention is compatible. However, typically the compressor is an inverter compressor, on/off compressor or screw I screw-inverter type compressors. Most often the compressor will be an inverter compressor as theses have been found to provide optimal efficiency with the heat transfer fluid of the invention.

Also provided in a further aspect of the invention is a use of the fluid according to the first aspect of the invention, as heat transfer fluid. It is often the case that the heat transfer fluid is used as a coolant. Also provided is a process for treating an atmosphere or environment using a heat transfer device comprising the heat transfer fluid according to the first aspect of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In an experiment, to a first mixture comprising 35% to 39.9% tetrafluorethane and 52.5% to 55.1% tetrafluoropropene (making up about 95 wt. % the total weight of the final mixture) there was added a second mixture comprising about 2.5 wt. % of difluoromethane and about 2.5 wt. % of pentafluoroethane (making up about 5 wt. % the total weight of the final mixture). The resulting mixture experienced a pressure increase of 2.5 - 3.5 bars. This pressure is sufficient to obtain a good cooling/heating effects results in a heat transfer fluid with excellent energy efficiency. By increasing the content of the second mixture to a total content of 7.5 wt. %, the pressure increases dramatically. As the total content of the second mixture exceeds 10%, efficiency savings become less dramatic. If the total content of difluoromethane and pentafluoroethane is less than 2.5 wt. % the gas composition becomes less suitable for heat pump and air conditioner applications.

The basic components are readily available from existing manufacturers. The gas composition according to the invention provides exceptional performance and cost savings well in excess up to of 62% of existing inverter compressors (DC) available on the market today.

The gas composition of the invention is more ozone friendly than the existing alternatives and was found to have a global warming potential (GWP) approximately 650, which is much lower than the conventional heat transfer fluids used in industry.

EXPERIMENTAL

A comparative test was conducted between a 50:50 mixture of difluoromethane and pentafluoroethane (often referred to in the industry as R410A) and the gas composition according to the invention (referred to herein as Composition A) which has a composition as outlined below:

Gas	Amount / wt. %
difluoromethane	2.5
pentafluoroethane	2.5
2,3,3,3-tetrafluoropropene	55.1
1,1,1,2-tetrafluoroethane	39.9

TABLE 1. Composition of one embodiment of the invention

Measurements were performed on an air conditioning apparatus from Gree Electronic 2400BTU (British Thermal Unit) and Toshiba 12000BTU. Below average data are registered during a 15 minutes run. The measurements were made on two different days, and thus, there are some differences on some of the parameters such as the outdoor temperature.

Composition

R410A

Measurement Area

Consumed electrical power / A	3.9	1.7
Incoming air temperature to evaporator / °C	26.8	27.5
Outgoing air temperature to evaporator (average) / °C	18.5	18.5
Incoming air temperature to condenser / °C	27.2	30.0
Outgoing air temperature to condenser (average) / °C	34.0	34.5
Air speed through evaporator / m s'¹	3.5	4.5
Air speed through condenser / m s'¹	5.1	5.8
Relative air humidity inside device	79.0	79.4
Pressure / bar	8.9	3.4

TABLE 2. Power measurements of the tested gas composition versus R410A.

In addition a simple test to examine the heat effect of the fluid of the invention was performed. It was heated to about 42°C outside, from about 23°C inside. Outside temperature was about the same as cooling. Energy consumption was 1.2 A at a pressure of 10.5 bars.

Claims

1. A heat transfer fluid comprising:

a first component, present in an amount greater than 85% wt., comprising (a) a C1-C6 tetrafluoroalkane and (b) a C1-C6 tetrafluoroalkene; and a second component, present in an amount less than 15% wt., comprising (c) a C1-C6 difluoroalkane and (d) a C2-C6 pentafluoroalkane.

2. A fluid according to claim 1, wherein (a) is tetrafluoroethane.

3. A fluid according to claim 1 or 2, wherein (b) is tetrafluoropropene.

4. A fluid according to ant of claims 1 to 3, wherein the ratio of (a) to (b) is in the range 1:2 to 2:5 by weight.

5. A fluid according to any preceding claim, wherein (a) is present in an amount in the range 30 wt.% to 40 wt.%.

6. A fluid according to any preceding claim, wherein (b) is present in an amount in the range 50 wt.% to 60 wt.%.

7. A fluid according to any preceding claim, wherein (c) is difluoromethane.

8. A fluid according to any preceding claim, wherein (d) is pentafluoroethane.

9. A fluid according to any preceding claim, wherein the ratio of (c) to (d) is in the range 2:3 to 3:2 by weight.

10. A fluid according to any preceding claim, wherein (c) is present in an amount in the range 2.5 wt.% to 10 wt.%.

11. A fluid according to any preceding claim, wherein (d) is present in an amount in the range 2.5 wt.% to 10 wt.%.

12. A fluid according to any preceding claim, wherein the first component is present in an amount greater than 90 wt.%.

13. A fluid according to any preceding claim, wherein the second component is present in an amount less than 10 wt.%.

14. A heat transfer device comprising the fluid according to any preceding claim.

15. A heat transfer device according to any preceding claim, wherein the device is selected from: air conditioning units, refrigeration units, heat pumps, centrifugal chillers or a combination thereof.

10

16. Use of a fluid according to any preceding claim as a heat transfer fluid.

17. A fluid, device or use as described herein with reference to the accompanying description, examples and drawings.

Intellectual

Property

Office

GB 1620421.6

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