AU6977696A

AU6977696A - Hydrofluorocarbon refrigerants

Info

Publication number: AU6977696A
Application number: AU69776/96A
Authority: AU
Inventors: Ian Robert Shanklnd; Rajiv Ratna Singh; David Paul Wilson
Original assignee: AlliedSignal Inc
Current assignee: Honeywell International Inc
Priority date: 1995-09-14
Filing date: 1996-09-13
Publication date: 1997-04-01
Also published as: JPH10511135A; CA2231111A1; EP0850286A1; WO1997010312A1

Description

HYDROFLUOROCARBON REFRIGERAJNTS

Field ofthe Invention

This invention relates to hydrofluorocarbons useful in refrigeration and heat pump applications as well as foam blowing agents. More specifically, the invention provides hydrofluorocarbons that are environmentally desirable replacements for chlorofluorocarbons and hydrochlorofluorocarbons in refrigeration applications, such as centrifugal chillers, and foam blowing agent applications.

Background ofthe Invention Fluorocarbon based fluids have found widespread use in industry for refrigeration applications such as air conditioning and heat pump applications. Vapor compression is one type of refrigeration. In its simplest form, vapor compression involves changing the refrigerant from the liquid to the vapor phase through heat absorption at a low pressure and then from the vapor to the liquid phase through heat removal at an elevated pressure.

While the primary purpose of refrigeration is to remove energy at low temperature, the primary purpose ofa heat pump is to add energy at higher temperature. Heat pumps are considered reverse cycle systems because, for heating, the operation ofthe condenser is interchanged with that ofthe refrigeration evaporator.

The art is continually seeking new fluorocarbon based refrigerants and blowing agents that offer alternatives to fluids currently in use. Of particular interest as alternatives are fluorocarbon based compositions that are considered to be environmentally safe substitutes

Ideally, replacement refrigerant compositions possess those properties unique to the composition being replaced including chemical stability, low toxicity, non-flammability, and efficiency-in-use. The latter characteristic is important in refrigeration and air-conditioning applications especially where a loss in refrigerant thermodynamic performance or energy efficiency may have secondary environmental impacts through increased fossil fuel usage arising from an increased demand for electrical energy. Furthermore, the ideal substitute would not require major engineering changes to conventional equipment currently used.

Previously, 1,1,2,2,3-pentafluoropropane, HFC-245ca, has been proposed as an alternative to l,l-dichloro-2,2,2-trifluoroethane, R-123, and trichlorofluoromethane, R- 11. See N.D. Smith et al., "R-245ca: A Potential Far Term Alternative For R-11", 35 ASHRAE J. 19 -23 (1993). The present invention provides additional compounds and compositions that are suitable replacements for R-11 and, in addition, may be used as foam blowing agents.

Description ofthe Invention

In accordance with the invention, it has been discovered that the compounds 1, 1, 1,2,3-pentafluoropropane ("HFC-245eb"), 1, 1, 1,3,3- pentafluoropropane ("HFC-245fa"), 1,1,2,3,3-pentafluoropropane ("HFC- 245ea"), and mixtures thereof are useful as refrigerants, heat transfer fluids, and blowing agents. More specifically it has been discovered that these compounds and mixtures meet the need for a nonflammable refrigerant which has a low ozone depletion potential and is a negligible contributor to green-house global warming compared with currently used refrigerants, such as R-11 and 123. Further, it has been discovered that these compounds and mixtures have COP's and capacities that render them suitable for use in refrigeration applications, including in centrifugal chillers. Also, the compounds and mixtures ofthe invention exhibit low compressor discharge temperatures.

For purposes ofthe invention, by centrifugal chillers is meant refrigeration equipment that uses centrifugal compression to compress the refrigerant.

In one embodiment, the invention provides a method for producing refrigeration using a compound selected from HFC-245eb, HFC-245fa, HFC- 245ea, and mixtures thereof. In still another embodiment, a method for producing refrigeration using a centrifugal chiller is provided using a compound selected from

HFC-245eb, HFC-245fa, HFC-245ea, and mixtures thereof. In another embodiment ofthe invention, a method for producing heating is provided using a compound selected from HFC-245eb, HFC-245fa, HFC-245ea, and mixtures thereof. For purposes of this invention, by mixtures is meant both nonazeotropic and azeotrope-like compositions of at least two ofthe compounds.

Thus, in yet another embodiment, this invention provides azeotrope-like compositions comprising effective amounts of at least two compounds selected from HFC-245eb, HFC -245fa, and HFC-245ea. By effective amount is meant an amount of each component that, when combined with the other component, results in the formation of an azeotrope or azeotrope-like mixture. Preferably, the invention provides azeotrope-like compositions comprising from about 10 to about 90 weight percent 245fa and from about 90 to about 10 weight percent 245ea, the compositions having a boiling point 25° C ±7° C at 760 mm Hg. More preferably, the composition comprises from about 30 to about 70 weight percent HFC-245fa and from about 70 to about 30 weight percent HFC-245ea, more preferably about 50 weight percent HFC-245fa and about 50 weight percent HFC-245ea.

For purposes of this invention, azeotrope-like compositions are compositions that behave like azeotropic mixtures. From fundamental principles, the thermodynamic state of a fluid is defined by pressure, temperature, liquid composition, and vapor composition. An azeotropic mixture is a system of two or more components in which the liquid composition and vapor composition are equal at the state pressure and temperature. In practice, this means that the components of an azeotropic mixture are constant boiling and cannot be separated during a phase change.

Azeotrope-like compositions behave like azeotropic mixtures, e_^, or are constant boiling or essentially constant boiling. In other words, for azeotrope-like compositions, the composition ofthe vapor formed during boiling or evaporation is identical, or substantially identical, to the original liquid composition Thus, with boiling or evaporation, the liquid composition changes, if at all, only to a minimal or negligible extent. This is to be contrasted with nonazeotrope-like compositions in which, during boiling or evaporation, the liquid composition changes to a substantial degree.

The compounds and mixtures ofthe invention may be used in a method for producing refrigeration that comprises condensing a refrigerant and thereafter evaporating the refrigerant in the vicinity ofa body to be cooled. Alternatively, the compounds and mixtures ofthe invention may be used in a method for producing heating which comprises condensing a refrigerant in the vicinity ofa body to be heated and thereafter evaporating the refrigerant.

In yet another embodiment, the compounds and mixtures ofthe invention may be used in a method for producing refrigeration using a centrifugal chiller that comprises compressing the compound or mixture ofthe invention by centrifugal compression and evaporating the refrigerant in the vicinity of a body to be cooled.

In still another embodiment, the compounds and mixtures ofthe present invention may be used in a method for producing foam comprising blending a heat plasticized resin with a volatile blowing agent comprising the fluids ofthe present invention and introducing the resin/volatile blowing agent blend into a zone of lower pressure to cause foaming.

In yet another embodiment the compounds and mixtures ofthe present invention may also be used in a method of dissolving contaminants or removing contaminants from the surface ofa substrate which comprises the step of contacting the substrate with the compositions ofthe present invention. In another embodiment, the compounds and mixtures ofthe present invention may also be used as fire extinguishing agents. The compounds and mixtures ofthe present invention are known materials. Preferably, the materials should be used in sufficiently high purity so as to avoid the introduction of adverse influences upon the cooling or heating properties, constant-boiling properties, or blowing agent properties ofthe system.

Additional components may be added to the compounds and compositions of this invention to tailor their properties according to the need. For example, in the art, propane may be added to refrigerant compositions to aid oil solubility and may be added to the fluids ofthe present invention. Nitromethane may also be added as a stabilizer. Similar materials may be added to the present compositions.

The present invention is more fully illustrated by the following non-limiting examples.

EXAMPLE 1

The critical temperature of HFC-245ea was measured by measuring the temperature where the meniscus between the liquid and vapor phase disappeared and was found to be 193.0° C.

EXAMPLE 2

The liquid density of material HFC-245ea was measured, as a function of temperature, using glass flotation beads of precisely known densities. The following data were obtained:

Table

Temperature (C) Density (g/cc)

191.10 0.69887

185.86 0.79875

175.99 0 89868

161.26 0.99867

140.05 1.09876

113.75 1.19895

81.00 1.29928

42.74 1.39974

-0.27 1.50033

EXAMPLE 3 The vapor pressure of HFC-245ea was measured by loading a sample of the material in a stainless steel cylinder and placing the cylinder in a temperature controlled bath. The cylinder was connected to a pressure transducer. The following data were obtained:

Table 2

Temperature (C) Pressure (psia)

0.00 2.50

12.06 4.60

22.08 6.80

26.10 8.30

39.16 14.10

42.13 16.20

58.92 28.30

76.55 48.50

91.53 74.30

EXAMPLE 4 The critical temperature of HFC-245eb was measured by measuring the temperature where the meniscus between the Liquid and vapor phase disappeared and was found to be 164.90° C. EXAMPLE 5 The liquid density of material HFC-245eb was measured, as a function of temperature, using glass flotation beads of precisely known densities. The following data were obtained:

Table 3

Temperature (C) Density (g cc)

-27.36 1.50073

14.19 1.40012

51 67 1.29964

84.02 1.19930

1 10.40 1.09908

131.59 0.99896

146.66 0.89893

156.95 0.79897

162.40 0.69906

EXAMPLE 6 The vapor pressure of HFC-245eb was measured by loading a sample of the material in a stainless steel cylinder and placing the cylinder in a temperature controlled bath. The cylinder was connected to a pressure transducer. The following data were obtained:

Table 4

Temperature (C) Pressure (psia)

-20.85 1.90

-14.89 2.60

0.00 5.50

6.11 7 40

9.66 8.60

15.08 10.90

20.34 13.50

21.13 13.90

23.86 15.30

39 38 27.20

54.69 44.80

67.79 66.30

33.65 22.30

33.57 22.20

40.26 27.80

40.25 27.80

123.68 239.50

140.54 330.00

155.56 419.30

EXAMPLE 7 The vapor pressure of HFC-245fa was measured by loading a sample of the material in a stainless steel cylinder and placing the cylinder in a temperature controlled bath. The cylinder was connected to a pressure transducer. The following data were obtained: Table 5

Temperature (C) Pressure (psia)

-29.10 1.83

-20.84 2.85

-10.09 4.81

0.01 7.88

12.05 13.02

12.05 13.13

14.05 14.22

14.06 14.27

14.60 14.58

16.34 15.62

20.47 18.30

Example 8 This example shows that HFC-245ea, HFC-245fa and HFC-245eb have certain advantages when compared to other refrigerants which are currently used in certain refrigeration cycles.

The theoretical performance ofa refrigerant at specific operating conditions can be estimated from the thermodynamic properties ofthe refrigerant using standard refrigeration cycle analysis techniques as described, for example, in RC Downing, Fluorocarbon Refrigerants Handbook. Chapter 3, Prentice-Hall, 1988 The coefficient of performance, COP is a universally accepted measure, especially useful in representing the relative thermodynamic efficiency ofa refrigerant in a specific heating or cooling cycle involving evaporation or condensation ofthe refrigerant. In refrigeration engineering, this term expresses the ratio of useful refrigeration to the energy applied by the compressor in compressing the vapor. The capacity ofa refrigerant represents the volumetric efficiency ofthe refrigerant. To a compressor engineer, this value expresses the capability ofa compressor to pump quantities of heat for a given volumetric flow rate of refrigerant. In other words, given a specific compressor, a refrigerant with a higher capacity will deliver more cooling or heating power. We have performed this type of calculation for a water chiller refrigeration cycle where the condenser temperature is typically 100° F and the evaporator temperature is typically 30° F. We have further assumed compression efficiency of 80 % in a saturated cycle. The compressor has a displacement of 1000 cubic feet per hour. Such calculations were performed for HFC-245ea, HFC-245eb and HFC-245fa and for R-123. R-123 is presently being used as an alternative for R- 11 in centrifugal chillers. Table 6 lists the COP, discharge temperature and capacity ofthe various refrigerants.

It can be seen that, compared to the existing alternatives to R-11, such as R-123, HFC-245fa and 245eb have higher refrigeration capacity. HFC-245fa and 245eb have lower compression ratios which ratios are advantageous from the point of increased reliability of mechanical machinery in which these refrigerants are likely to be employed. Also, HFC-245ea exhibits higher energy efficiency in comparison to the other fluids.

EXAMPLE 9

Approximately 10 g HFC-245fa were added to the reference and sample arms ofa differential ebulliometer to obtain boiling point measurements. See W. Swietoslawski, Ebulϋometric Measurements (1945). The system was brought to total reflux by gently heating the lower part ofthe ebulliometer. The temperature ofthe boiling liquid was measured with reference to pure HFC-245fa using a PC17US96/14736

11 matched pair of thermistors precise to ± 0.01° C. Boiling points were recorded after steady state was attained. Aliquots of HFC-245ea were added to the sample side and the change in boiling temperature noted. Data was obtained up to approximately 42 weight percent of HFC-245ea and indicated that the two components formed a constant boiling composition over a range of compositions ofthe two components. The boiling point at 760 mm Hg was constant within 2° C from about 1 to about 27 weight percent HFC-245ea and from about 99 to about

73 weight percent HFC-245fa.

Table 7

Weight Percent 245ea BP (°C) Weight Percent 245ea BP (^βC)

0 145 97 160

04 146 100 160

07 147 103 160

11 147 106 160

14 148 109 161

18 149 111 161

21 149 114 162

24 150 117 162

28 150 120 162

31 151 123 162

35 151 128 163

38 152 139 164

41 152 150 165

44 153 174 168

48 153 198 170

51 154 220 172

54 154 242 174

57 155 262 176

61 155 262 176

64 156 281 178

67 156 299 179

70 156 316 181

73 157 332 183

76 157 348 186

79 157 363 192

82 158 377 197

85 158 391 199

88 159 404 199

91 159 416 201

94 160 428 204

The data from Table 7 may be compared to the boiling point ofthe HFC- 245fa/HFC-245ea mixture obtained according to Raoult's Law The comparison, illustrated on Table 8, shows that the actual boiling point does not change as much on the addition of HFC-245ea as is predicted and the mixture, therefore, is unexpectedly constant boiling.

Table 8

Wt % 245fa Actual BP (° C) Raoult's Law BP (° C)

1 14.5 14.6

5 15.3 15.4

10 16.0 16.3

20 17.0 18.1

30 17.9 20

40 19.8 22.1

50 23.2^' 24.4 • Extrapolated value.

Example 10 From the data of Example 9,- the theoretical performance of mixtures of

30/70 weight percent, 50/50 weight percent, and 70/30 weight percent HFC- 245fa HFC-245ea are calculated using the method of Example 8. The calculation is performed for a water chiller refrigeration cycle in which the condenser temperature is typically 100° F and the evaporator temperature is 30° F.

Compression efficiency of 80 % in a saturated cycle is assumed. The compressor displacement is 1000 cubic feet per hour. The results are that the compositions have refrigeration capacities closer to R-11 than either ofthe two components singly and, thus, are suitable replacements for those environmentally undesirable refrigerants currently used in chiller applications.

Claims

What is claimed is:

1. A method for producing refrigeration comprising condensing a refrigerant selected from the group consisting of 1, 1, 1,2,3-pentafluoropropane, 1, 1, 1,3,3- pentafluoropropane, 1, 1,2,3, 3 -pentafluoropropane, and mixtures thereof, and thereafter evaporating the refrigerant in the vicinity ofa body to be cooled.

2. The method of claim 1 wherein the refrigerant is a mixture which is an azeotrope-like composition consisting essentially of at least two compounds selected from the group consisting essentially of 1 , 1 , 1 ,2,3-pentafluoropropane, 1,1, 1,3, 3 -pentafluoropropane, and 1,1,2,3,3-pentafluoropropane.

3. The method of claim 1 wherein the refrigerant is a mixture which is a nonazeotropic composition comprising 1,1, 1,2,3-pentaflupropropane and 1,1, 1,3, 3 -pentafluoropropane.

4. The method of claim 1 wherein the refrigerant is a mixture which is an azeotrope-like composition consisting essentially of 1,1, 1,2,3-pentafluoropropane and 1,1,1,3,3-pentafluoropropane.

5. The method of claim 1 wherein the refrigerant is a mixture which is an azeotrope-like composition consisting essentially of 1, 1, 1,2, 3 -pentafluoropropane and 1,1,2,3,3-pentafluoropropane.

6. The method of claims 1 or 2 wherein the refrigerant is a mixture which is an azeotrope-like composition consisting essentially of 1,1,1,3,3- pentafluoropropane and 1,1, 2,3, 3 -pentafluoropropane.

7 A method for producing refrigeration using a centrifugal chiller comprising compressing a refrigerant selected from the group consisting of 1, 1, 1,2,3- pentafluoropropane, 1, 1,1 ,3 , 3-pentafluoropropane, 1,1,2,3,3 -pentafluoropropane, and mixtures thereof, and thereafter evaporating the refrigerant in the vicinity of a body to be cooled.

8. The method of claim 7 wherein the refrigerant is 1,1,1,3,3- pentafluoropropane .

9. The method of claim 7 wherein the refrigerant is 1, 1,2,3,3- pentafluoropropane.

10. The method of claim 7 wherein the refrigerant is a mixture which is a nonazeotropic composition comprising at least two compounds selected from the group consisting essentially of 1,1,1,2,3-pentafluoropropane, 1,1,1,3,3- pentafluoropropane, and 1, 1,2,3,3-pentafluoropropane.

11. The method of claim 7 wherein the refrigerant is a mixture which is an azeotrope-like composition consisting essentially of at least two compounds selected from the group consisting essentially of 1 , 1 , 1 ,2,3-pentafluoropropane, 1,1, 1,3, 3 -pentafluoropropane, and 1,1,2,3,3-pentafluoropropane.

12. The method of claim 7 wherein the refrigerant is a mixture which is a nonazeotropic composition comprising 1,1, 1,2, 3 -pentafluoropropane and 1,1,1,3,3-pentafluoropropane.

13. The method of claim 7 wherein the refrigerant is a mixture which is an azeotrope-like composition consisting essentially of 1, 1,1,2,3-pentafluoropropane and 1, 1,1,3,3-pentafluoropropane.

14. The method of claim 7 wherein the refrigerant is a mixture which is a nonazeotropic composition comprising 1,1,1,2,3-pentafluoropropane and 1,1,2,3,3 -pentafluoropropane.

15. The method of claim 7 wherein the refrigerant is a mixture which is an azeotrope-like composition consisting essentially of 1, 1,1,2,3-pentafluoropropane and 1,1,2,3,3-pentafluoropropane.

16 The method of claim 7 wherein the refrigerant is a mixture which is a nonazeotropic composition comprising 1, 1, 1,3, 3 -pentafluoropropane and 1, 1,2,3,3-pentafluoropropane.

17. The method of claim 7 wherein the refrigerant is a mixture which is an azeotrope-like composition consisting essentially of 1, 1,1,3,3 -pentafluoropropane and 1,1,2,3,3-ρentafluoropropane.

18. The azeotrope-like composition consisting essentially of effective amounts of 1,1, 1,3, 3 -pentafluoropropane and 1, 1, 2, 3, 3 -pentafluoropropane which composition boils at 25° C ± 7° at 760 mm Hg