Non-azeotropic refrigerant compositions containing carbon dioxide

The present invention provides refrigerant blends which are replacements for chlorodifluoromethane(HCFC-22). The present blends have refrigeration characteristics which are similar to HCFC-22. The blends comprise from about 10 to about 90 weight percent of a first component selected from the group consisting of 1,1,1-trifluoroethane, difluoromethane, propane, and mixtures thereof; from about 1 to about 50 weight percent of a second component selected from the group consisting of hydrofluorocarbon having 1 to 3 carbon atoms, fluorocarbon having 1 to 3 carbon atoms, inorganic compound, and mixtures thereof having a boiling point at atmospheric pressure in the range from about -90 degrees C. to less than -50 degrees C.; and from about 1 to about 50 weight percent of a third component which is hydrofluorocarbon having 1 to 3 carbon atoms, other than 1,1,1-trifluoroethane, having a boiling point at atmospheric pressure in the range from about -50 degrees C. to about -10 degrees C. The refrigerant compositions have a vapor pressure substantially equal to the vapor pressure of HCFC-22.

FIELD OF THE INVENTION 
This invention relates to novel nonazeotropic compositions containing 
difluoromethane; 1,1,1-trifluoroethane; or propane. These mixtures have 
improved efficiency and capacity as refrigerants for heating and cooling. 
BACKGROUND OF THE INVENTION 
Fluorocarbon based fluids have found widespread use in industry for 
refrigeration, air conditioning and heat pump applications. Vapor 
compressions cycles are one form of refrigeration. In its simplest form, 
the vapor compression cycle 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. First, the refrigerant is vaporized in the evaporator 
which is in contact with the body to be cooled. The pressure in the 
evaporator is such that the boiling point of the refrigerant is below the 
temperature of the body to be cooled. Thus, heat flows from the body to 
the refrigerant and causes the refrigerant to vaporize. The formed vapor 
is then removed by means of a compressor in order to maintain the low 
pressure in the evaporator. The temperature and pressure of the vapor are 
then raised through the addition of mechanical energy by the compressor. 
The high pressure vapor then passes to the condenser whereupon heat 
exchange with a cooler medium, the sensible and latent heats are removed 
with subsequent condensation. The hot liquid refrigerant then passes to 
the expansion valve and is ready to cycle again. 
While the primary purpose of refrigeration is to remove energy at low 
temperature, the primary purpose of a heat pump is to add energy at higher 
temperature. Heat pumps are considered reverse cycle systems because for 
heating, the operation of the condenser is interchanged with that of the 
refrigeration evaporator. 
Certain chlorofluorocarbons have gained widespread use in refrigeration 
applications including air conditioning and heat pump applications owing 
to their unique combination of chemical and physical properties. The 
majority of refrigerants utilized in vapor compression systems are either 
single component fluids or azeotropic mixtures. 
The majority of refrigerants utilized in vapor compression systems are 
either single component fluids or azeotropic mixtures. The latter are 
binary mixtures, but for all refrigeration purposes behave as single 
component fluids. Nonazeotropic mixtures have been disclosed as 
refrigerants for example in U.S. Pat. Nos. 4,303,536 and 4,810,403 but 
have not yet found widespread use in commercial applications. 
The condensation and evaporation temperatures of single component fluids 
are defined clearly. If we ignore the small pressure drops in the 
refrigerant lines, the condensation or evaporation occurs at a single 
temperature corresponding to the condenser or evaporation pressure. For 
mixtures being employed as refrigerants, there is no single phase change 
temperature but a range of temperatures. This range is governed by the 
vapor-liquid equilibrium behavior of the mixture. This property of 
mixtures is responsible for the fact that when nonazeotropic mixtures are 
used in the refrigeration cycle, the temperature in the condenser or the 
evaporator has no longer a single uniform value, even if the pressure drop 
effect is ignored. Instead, the temperature varies across the equipment, 
regardless of the pressure drop. In the art, this variation in the 
temperature across an equipment is known as temperature glide. 
It has been pointed out in the past that for non-isothermal heat sources 
and heat sinks, this temperature glide in mixtures can be utilized to 
provide better efficiencies. However in order to benefit from this effect, 
the conventional refrigeration cycle has to be redesigned, see for example 
T. Atwood, "NARBs-The Promise and the Problem", paper 86-WA/HT-61 American 
Society of Mechancial Engineers. In most existing designs of refrigeration 
equipment, a temperature glide is a cause of concern. Therefore, 
nonazeotropic refrigerant mixtures have not found wide use. An 
environmentally acceptable nonazeotropic mixture with a small temperature 
glide and with an advantage in refrigeration capacity over other known 
pure fluids will have a general commercial interest. 
Chlorodifluoromethane (HCFC-22) is a currently used refrigerant. Although 
HCFC-22 is only partially halogenated, it still contains chlorine and 
hence has a propensity for ozone depletion. What is needed in the 
refrigerant art is a replacement for HCFC-22 which has similar 
refrigeration characteristics, is nonflammable, has low temperature 
guides, and contains no ozone-depleting chlorine atoms. 
U.S. Pat. No. 4,810,403 teaches ternary or higher blends of halocarbon 
refrigerants which are substitutes for dichlorodifluoromethane (CFC-12). 
The blends have a first component which has a boiling point at atmospheric 
pressure in the range of -50 degrees C. to -30 degrees C., a second 
component which has a boiling point at atmospheric pressure in the range 
of -30 degrees C. to -5 degrees C., and a third component which has a 
boiling point at atmospheric pressure in the range of -15 degrees C. to 30 
degrees C. The preferred blend contains chlorodifluoromethane (HCFC-22), 
1,1-difluoroethane (HFC-152a), and 1,2-dichloro-1,1,2,2-tetrafluoroethane 
(CFC-114). As the reference lists HCFC-22 as a possible refrigerant 
component, the reference is not teaching refrigerant substitutes for 
HCFC-22. 
As such, the art is seeking new fluorocarbon based mixtures which offer 
alternatives for HCFC-22 in refrigeration and heat pump applications. 
Currently, of particular interest, are fluorocarbon based mixtures which 
are considered to be environmentally acceptable substitutes for the 
presently used hydrochlorofluorocarbons which are suspected of causing 
environmental problems in connection with the earth's protective ozone 
layer. Mathematical models have substantiated that hydrofluorocarbons, 
such as 1,1,1-trifluoroethane (HFC-143a) or difluoromethane (HFC-32) will 
not adversely affect atmospheric chemistry, being negligible contributors 
to stratospheric ozone depletion and global warming. 
The substitute materials must also possess those properties unique to the 
CFC's including chemical stability, low toxicity, non-flammability, and 
efficiency in-use. The latter characteristic is important, for example, in 
air conditioning and refrigeration 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. 
The aforementioned environmentally acceptable refrigerants HFC-32 and 
HFC-143a are flammable which may limit their general use. These 
refrigerants are generally regarded as too low boiling fluids to directly 
replace chlorodifluoromethane (HCFC-22). 
In order to overcome the flammability of HFC-32, we blended HFC-32 with 
1,1,1,2-tetrafluoroethane (HFC-134a) and the result was zero ozone 
depletion potential compositions which are useful substitutes for HCFC-22. 
At high amounts of HFC-32 though, compositions of HFC-32 and HFC-134a are 
flammable. In order to completely eliminate the flammability of such 
compositions, we decided to add a third nonflammable component. In adding 
a third component, we wanted the resulting ternary composition to have a 
zero ozone depletion potential and have a boiling point comparable to that 
of HCFC-22. One member from the list of compounds having zero ozone 
depletion potential and boiling points at atmospheric pressure in the 
range of -90 degrees C. to -60 degrees C. is trifluoromethane (HFC-23) 
which has a low critical temperature; as those skilled in the art know, 
compounds having low critical temperatures are not used as refrigerants 
because they do not condense at room temperature and in a refrigerant 
blend, would be expected to substantially reduce the refrigeration 
efficiency and capacity of the blend. We were pleasantly surprised to find 
that in addition to being nonflammable, a blend of HFC-32, HFC-134a, and 
HFC-23 has refrigeration efficiency and capacity substantially the same as 
a blend of HFC-32 and HFC-134a. 
SUMMARY OF THE INVENTION 
Thus, we have discovered refrigerant blends which are substitutes for 
HCFC-22. These nonazeotropic refrigerant compositions comprise from about 
10 to about 90 weight percent of a first component selected from the group 
consisting of 1,1,1-trifluoroethane (HFC-143a), difluoromethane (HFC-32), 
propane, and mixtures thereof; from about 1 to about 50 weight percent of 
a second component selected from the group consisting of hydrofluorocarbon 
having 1 to 3 carbon atoms, fluorocarbon having 1 to 3 carbon atoms, 
inorganic compound, and mixtures thereof having a boiling point at 
atmospheric pressure in the range from about -90 degrees C. to less than 
-50 degrees C.; and from about 1 to about 50 weight percent of a third 
component which is hydrofluorocarbon having 1 to 3 carbon atoms, other 
than 1,1,1-trifluoroethane, having a boiling point at atmospheric pressure 
in the range from about -50 degrees C. to about -10 degrees C. The 
refrigerant compositions have a vapor pressure substantially equal to the 
vapor pressure of HCFC-22. 
The term "hydrofluorocarbon" as used herein means a compound having carbon, 
hydrogen, and fluorine atoms. The term "fluorocarbon" as used herein means 
a compound having carbon and fluorine atoms. For the second component, any 
hydrofluorocarbon having 1 to 3 carbon atoms, fluorocarbon having 1 to 3 
carbon atoms, or inorganic compound having a boiling point at atmospheric 
pressure in the range from about -90 degrees C. to less than -50 degrees 
C. may be used in the present invention. For the third component, any 
hydrofluorocarbon having 1 to 3 carbon atoms, other than 
1,1,1-trifluoroethane, having a boiling point at atmospheric pressure in 
the range from about -50 degrees C. to about -10 degrees C. may be used in 
the present invention. 
The preferred first component is difluoromethane. 
Preferably, the second component is selected from the group consisting of: 
trifluoromethane (HFC-23), hexafluoroethane (FC-116), carbon dioxide or 
sulphur hexafluoride. The preferred second component is trifluoromethane. 
All members listed for the second component are nonflammable and generally 
boil at a temperature below that of HFC-32 or HFC-143a. 
Preferably, the third component is selected from the group consisting of: 
pentafluoroethane (HFC-125), 1,1,2,2-tetrafluoroethane (HFC-134), 
1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1,2,3,3,3-heptafluoropropane 
(HFC-227ea), 1,1,1,2,2,3,3-heptafluoropropane (HFC-227ca), or 
1,1,1,2,2-pentafluoropropane (HFC-245cb). The preferred third component is 
1,1,1,2-tetrafluoroethane. All members listed for the third component are 
nonflammable and generally boil at a temperature above that of HFC-32 or 
HFC-143a. 
Small quantities of HFC-227ea, HFC-227ca, and HFC-245cb are available from 
PCR and Halocarbon Products. All other components of the present invention 
are available in commercial quantities. Also, HFC-227ea, HFC-227ca, and 
HFC-245cb may be prepared according to known methods such as those 
disclosed in International Publication Number WO 90/08754. For example, 
HFC-227ca may be prepared by reacting 
1,1,1,3,3-pentachloro-2,2-difluoropropane with niobium pentachloride at 
120 degrees C. HFC-245cb may be prepared by reacting 
1,1,1,2,2-pentachloropropane with tantalum pentafluoride at 120 degrees C. 
By "vapor pressure substantially equal to the vapor pressure of 
chlorodifluoromethane" or "similar refrigeration characteristics" is meant 
a vapor pressure which is plus or minus 30 percent of the vapor pressure 
of HCFC-22 at the same temperature over the temperature range of about 0 
degrees C. to about 100 degrees C. 
Additional components may be added to the mixture to tailor the properties 
of the mixture according to the need.

DETAILED DESCRIPTION OF THE INVENTION 
The properties of the preferred components of the present invention are 
listed in Table 1 below. BP in Table 1 stands for Boiling Point while CT 
stands for Critical Temperature. The * in Table 1 means sublimes at one 
atm pressure and the boiling point is the triple point. 
TABLE 1 
______________________________________ 
No. Formula BP (degrees C.) 
CT (degrees C.) 
______________________________________ 
HFC-32 CH.sub.2 F.sub.2 
-51.7 78.4 
HFC-143a CF.sub.3 CH.sub.3 
-47.6 73.1 
Propane C.sub.3 H.sub.8 
-42.1 96.7 
HFC-23 CHF.sub.3 -82.1 25.9 
FC-116 C.sub.2 F.sub.6 
-78.1 24.3 
-- CO.sub.2 * -78.5 31.3 
-- SF.sub.6 -64.0 45.5 
HFC-125 C.sub.2 HF.sub.5 
-48.5 66.3 
HFC-134 CHF.sub.2 CHF.sub.2 
-19.7 118.9 
HFC-134a CF.sub.3 CH.sub.2 F 
-26.5 101.1 
HFC-227ea 
CF.sub.3 CFHCF.sub.3 
-16.5 102.0 
HFC-227ca 
CF.sub.3 CF.sub.2 CHF.sub.2 
-15.6 104.7 
HFC-245cb 
CF.sub.3 CF.sub.2 CH.sub.3 
-17.5 107.0 
______________________________________ 
The most preferred composition comprises difluoromethane, trifluoromethane, 
and 1,1,1,2-tetrafluoroethane. 
In a preferred embodiment of the invention, the compositions comprise from 
about 20 to about 80 weight percent of the first component, from about 2 
to about 40 weight percent of the second component, and from about 2 to 
about 40 weight percent of the third component. 
In one process embodiment of the invention, the compositions of the 
invention may be used in a method for producing refrigeration which 
involves condensing a refrigerant comprising the compositions and 
thereafter evaporating the refrigerant in the vicinity of the body to be 
cooled. 
In another process embodiment of the invention, the compositions of the 
invention may be used in a method for producing heating which involves 
condensing a refrigerant comprising the compositions in the vicinity of 
the body to be heated and thereafter evaporating the refrigerant. 
Preferably the components used should be of sufficiently high purity so as 
to avoid the introduction of adverse influences upon the properties of the 
system. 
As mentioned above, when a refrigerant composition contains a flammable 
component like HFC-32, HFC-143a, or propane, the possibility of either the 
leaking vapor or the remaining liquid becoming flammable is a very 
undesirable hazard. We have discovered that the claimed compositions of 
the refrigerant blends containing either HFC-32, HFC-143a, or propane can 
be so formulated with the components from the two nonflammable groups that 
the original composition is nonflammable and the leaking vapor as well as 
the remaining liquid never become flammable. 
The present invention comprises ternary and higher blends based either on 
HFC-32, HFC-143a, or propane that have a vapor pressure substantially the 
same as the vapor pressure of HCFC-22 and which retain this relationship 
even after substantial evaporation losses, e.g. up to 50 percent by 
weight. A vapor pressure temperature relationship similar to HCFC-22 is 
especially desirable because it will need minimum amount of modifications 
in the present refrigeration equipment which is designed around the vapor 
pressure temperature relationship of the HCFC-22. 
It should be understood that the present compositions may include 
additional components so as to form new compositions. Any such 
compositions are considered to be within the scope of the present 
invention as long as the compositions have essentially the same 
characteristics and contain all the essential components described herein. 
The present invention is more fully illustrated by the following 
non-limiting Examples. 
EXAMPLES 1-72 
The compositions in Table 2 below are made and exhibit refrigeration 
characteristics similar to HCFC-22, have low temperature guides, and 
contain no chlorine atoms. Comp 1 stands for the first component, Comp 2 
stands for the second component, and Comp 3 stands for the third 
component. 
TABLE 2 
______________________________________ 
EX COMP 1 COMP 2 COMP 3 
______________________________________ 
1 HFC-143a HFC-23 HFC-125 
2 HFC-143a FC-116 HFC-125 
3 HFC-143a CO.sub.2 HFC-125 
4 HFC-143a SF.sub.6 HFC-125 
5 HFC-143a HFC-23 HFC-134 
6 HFC-143a FC-116 HFC-134 
7 HFC-143a CO.sub.2 HFC-134 
8 HFC-143a SF.sub.6 HFC-134 
9 HFC-143a HFC-23 HFC-134a 
10 HFC-143a FC-116 HFC-134a 
11 HFC-143a CO.sub.2 HFC-134a 
12 HFC-143a SF.sub.6 HFC-134a 
13 HFC-143a HFC-23 HFC-227ea 
14 HFC-143a FC-116 HFC-227ea 
15 HFC-143a CO.sub.2 HFC-227ea 
16 HFC-143a SF.sub.6 HFC-227ea 
17 HFC-143a HFC-23 HFC-227ca 
18 HFC-143a FC-116 HFC-227ca 
19 HFC-143a CO.sub.2 HFC-227ca 
20 HFC-143a SF.sub.6 HFC-227ca 
21 HFC-143a HFC-23 HFC-245cb 
22 HFC-143a FC-116 HFC-245cb 
23 HFC-143a CO.sub.2 HFC-245cb 
24 HFC-143a SF.sub.6 HFC-245cb 
25 HFC-32 HFC-23 HFC-125 
26 HFC-32 FC-116 HFC-125 
27 HFC-32 CO.sub.2 HFC-125 
28 HFC-32 SF.sub.6 HFC-125 
29 HFC-32 HFC-23 HFC-134 
30 HFC-32 FC-116 HFC-134 
31 HFC-32 CO.sub.2 HFC-134 
32 HFC-32 SF.sub.6 HFC-134 
33 HFC-32 HFC-23 HFC-134a 
34 HFC-32 FC-116 HFC-134a 
35 HFC-32 CO.sub.2 HFC-134a 
36 HFC-32 SF.sub.6 HFC-134a 
37 HFC-32 HFC-23 HFC-227ea 
38 HFC-32 FC-116 HFC-227ea 
39 HFC-32 CO.sub.2 HFC-227ea 
40 HFC-32 SF.sub.6 HFC-227ea 
41 HFC-32 HFC-23 HFC-227ca 
42 HFC-32 FC-116 HFC-227ca 
43 HFC-32 CO.sub.2 HFC-227ca 
44 HFC-32 SF.sub.6 HFC-227ca 
45 HFC-32 HFC-23 HFC-245cb 
46 HFC-32 FC-116 HFC-245cb 
47 HFC-32 CO.sub.2 HFC-245cb 
48 HFC-32 SF.sub.6 HFC-245cb 
49 Propane HFC-23 HFC-125 
50 Propane FC-116 HFC-125 
51 Propane CO.sub.2 HFC-125 
52 Propane SF.sub.6 HFC-125 
53 Propane HFC-23 HFC-134 
54 Propane FC-116 HFC-134 
55 Propane CO.sub.2 HFC-134 
56 Propane SF.sub.6 HFC-134 
57 Propane HFC-23 HFC-134a 
58 Propane FC-116 HFC-134a 
59 Propane CO.sub.2 HFC-134a 
60 Propane SF.sub.6 HFC-134a 
61 Propane HFC-23 HFC-227ea 
62 Propane FC-116 HFC-227ea 
63 Propane CO.sub.2 HFC-227ea 
64 Propane SF.sub.6 HFC-227ea 
65 Propane HFC-23 HFC-227ca 
66 Propane FC-116 HFC-227ca 
67 Propane CO.sub.2 HFC-227ca 
68 Propane SF.sub.6 HFC-227ca 
69 Propane HFC-23 HFC-245cb 
70 Propane FC-116 HFC-245cb 
71 Propane CO.sub.2 HFC-245cb 
72 Propane SF.sub.6 HFC-245cb 
______________________________________ 
EXAMPLE 73 
The example shows that it is possible to calculate the thermodynamic 
properties of a ternary mixture from using equation of state techniques. 
These are important for estimating theoretical performance of a 
refrigerant as discussed in Example 75. The equation of state package used 
was based on the NIST Mixture Properties formalism (DDMIX) available from 
the National Institute of Standards and Technology, Gaithersberg, Md. 
20899. An example of measured and calculated bubble pressures of a 48.1 wt 
% HFC-23, 19.3 wt % HFC-32, and 32.6 wt % HFC-134a ternary nonazeotropic 
blend is shown in Table 3. The very good agreement shows the high degree 
of confidence that may be placed in the results of the experiments and the 
theory. 
TABLE 3 
______________________________________ 
Bubble Pressure 
Bubble Pressure 
Temperature/.degree.K. 
exptl., psia 
calcd., psia 
______________________________________ 
263.54 154.2 151.8 
268.49 176.4 174.8 
278.38 230.0 228.2 
288.09 293.4 290.9 
298.08 367.9 366.9 
308.09 453.4 455.3 
318.12 550.7 556.1 
______________________________________ 
EXAMPLE 74 
By preparing various compositions of HFC-134a/HFC-32/HFC-23 in air and 
determining their flammability, it is possible to map out the region of 
compositions in air that are flammable. See, e.g. P. A. Sanders, The 
Handbook of Aerosol Technology at 146 (2d ed. 1979). The maximum amount of 
HFC-32 that can be blended with HFC-134a and HFC-23 and remain 
nonflammable in all proportions in air, can be determined from such a 
plot. Table 4 summaries the maximum or critical composition of HFC-32 
attainable with HFC-134a and a higher pressure component (e.g. HFC-23, 
HF-116, SF.sub.6, and CO.sub.2) for the binary mixtures. The CFR is the 
critical flammability ratio: which is the maximum amount of HFC-32 that a 
mixture of HFC-32/X can contain and still be nonflammable in all 
proportions in air. X represents the higher pressure components listed in 
Table 4. These binary flammability data can be used to predict the 
flammability of the more complex ternary mixture plus air. This complex 
mixture of three components and air does not lend itself to simple ternary 
diagrams. Therefore, air is not included so that we are able to show the 
data graphically. The air proportion itself is not important just whether 
or not the mixture is flammable in some proportion with air. FIG. 1 shows 
a composition of HCFC-134a, HFC-32, and HFC-23. Above the line A-B(more 
HFC-32), mixtures of those compositions are flammable in some proportion 
in air while below line A-B(less HFC-32), mixtures of those compositions 
are not flammable in air at any proportion of air. Further this diagram 
depicts compositions that will remain nonflammable in the event of a vapor 
leak. If the leak is from the liquid phase, some liquid will vaporize to 
fill the space vacated by the leaking liquid. Because the vapor is 1/25th 
as dense as the liquid, and very little vaporization occurs, therefore, 
very little fractionation occurs. In contrast, when the vapor phase is 
removed, all the liquid is eventually vaporized, producing a dramatic 
amount of fractionation. Liquid leaks produce only minor changes in the 
composition of the mixture. As such, a liquid leak is not problematic and 
only the case of a vapor leak must be considered. 
Shifts in the compositions of the vapor and liquid phases during leaking 
were calculated using ideal solution behavior. These types of calculations 
were used to determine what starting compositions would remain 
nonflammable on evaporation. Line D-C in FIG. 1 separates those 
compositions that could have flammable liquid phase compositions from 
those compositions that would remain nonflammable. Compositions rich in 
HFC-134a (right of the line) would have liquid phase compositions that 
remain nonflammable on evaporation. Line C-E separates composition that 
would fractionate given vapors that are flammable from those that would 
not produce flammable vapors. Compositions having more, HFC-23 (left of 
the line) would remain nonflammable vapors on segregation. Therefore, 
compositions below line D-C-E would not fractionate to produce either 
liquid or vapor phases that could be flammable. 
TABLE 4 
______________________________________ 
Maximum HFC-32 Compo 
% air at CFR 
Gas in HFC-32 
(mole or volume %) 
(mole or volume %) 
______________________________________ 
HFC-134a 72.9 20 
HFC-23 75.3 19 
HFC-116 88.1 20 
SF.sub.6 87.9 21 
CO.sub.2 55.2 29 
______________________________________ 
EXAMPLE 75 
This example shows that a HFC-32 containing blend has a performance similar 
to HCFC-22, yet is nonflammable even after substantial vapor leakage. 
The theoretical performance of a refrigerant at specific operating 
conditions can be estimated from the thermodynamic properties of the 
refrigerant using standard refrigeration cycle analysis techniques, see 
for example, "Fluorocarbons Refrigerants Handbook", Ch. 3, Prentice-Hall, 
(1988), by R. C. Downing. The coefficient of performance, COP, is a 
universally accepted measure, especially useful in representing the 
relative thermodynamic efficiency of a refrigerant in a specific heating 
or cooling cycle involving evaporation or condensation of 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 of a refrigerant represents the volumetric efficiency 
of the refrigerant. To a compressor engineer, this value expresses the 
capability of a 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. A similar calculation can also be performed for 
nonazeotropic refrigerant blends. 
We have performed this type of calculation for packaged air conditioning 
cycle where the condenser temperature is typically 115.degree. F. and the 
evaporator temperature is typically 40.degree. F. We have further assumed 
isentropic compression and a compressor inlet temperature of 60.degree. F. 
Such calculations were performed for a 0.72/28.71/70.57 by weight blend of 
HFC-23, HFC-32, and HFC-134a. The temperature glide in typical HCFC-22 
application in no case exceeded 15.degree. F. The coefficient of 
performance (COP), a measure of energy efficiency of the fluid, was found 
to be 5.36 as compared to 5.51 found for HCFC-22 in the same conditions. 
According to the known art (D. A. Didion and D. M. Bivens "The Role of 
Refrigerant Mixtures as Alternatives" in CFC's: Today's Options . . . 
Tomorrow's Solutions, NIST, 1990), the temperature glides of the order of 
10.degree. F. are minor enough for the mixture to be termed 
Near-Azeotropic. Therefore, the temperature glide of the mixture 
composition claimed is small enough and does not pose a problem for 
conventional refrigeration units. As can be seen from the attached FIG. 1, 
which gives the flammability limits of the three component blend of 
HFC-23, HFC-32, and HFC-134a measured by an ASTM 681 apparatus, the blend 
is nonflammable. Its vapor pressure is 11.37 bars at 25.degree. C. within 
10 percent of the HCFC-22 vapor pressure. The refrigeration capacity is 
about 95% of the HCFC-22. After 50 weight percent of the refrigerant is 
lost through the leakage of the vapor, the vapor pressure of the blend is 
9.44 bars, still within 10% of the HCFC-22 value. The refrigeration 
capacity has decreased to only 83% of the HCFC-22 value. The COP of the 
remaining fluid remained substantially the same at 5.37. Both the vapor at 
46 volume percent HFC-32 and the liquid at 28 volume percent HFC-32 has 
remained nonflammable as seen from FIG. 1. 
EXAMPLE 76 
We have performed another calculation of the type given in Example 75 for 
packaged air conditioning cycle where the condenser temperature is 
typically 115.degree. F. and the evaporator temperature is typically 
40.degree. F. We have further assumed isentropic compression and a 
compressor inlet temperature of 60.degree. F. This time such calculations 
were performed for a 77.56 gram blend of 0.0384 moles of HFC-23, 0.4648 
moles of HFC-32, and 0.4968 moles of HFC-134a. The temperature glide in 
typical HCFC-22 application in no case exceeded 17.degree. F. As can be 
seen from the attached FIG. 1, which gives the flammability limits of the 
three component blend of HFC-23, HFC-32, and HFC-134a measured by an ASTM 
681 apparatus, the blend is nonflammable. Its vapor pressure is 12.43 bars 
at 25.degree. C. within 25 percent of the HCFC-22 vapor pressure. The 
refrigeration capacity is substantially the same as the HCFC-22. The COP 
was 5.13. After 50 weight percent of the refrigerant is lost through the 
leakage of the vapor, the vapor pressure of the blend is 10.08 bars, 
within 2% of the HCFC-22 value. The refrigeration capacity has decreased 
to only 87% of the HCFC-22 value. The COP has increased marginally to 
5.35. Both the vapor at 51 volume percent HFC-32 and the liquid at 33 
volume percent HFC-32 has remained nonflammable as seen from FIG. 1. 
EXAMPLE 77 
We have performed another calculation of the type given in Examples 75 and 
76 under the conditions given earlier. This time such calculations were 
performed for a 75.62 gram blend of 0.0651 moles of HFC-23, 0.4865 moles 
of HFC-32, and 0.4484 moles of HFC-134a. The temperature glide in typical 
HCFC-22 application in no case exceeded 20.degree. F. As can be seen from 
the attached FIG. 1, which gives the flammability limits of the three 
component blend of HFC-23, HFC-32, and HFC-134a measured by an ASTM 681 
apparatus, the blend is nonflammable. Its vapor pressure is 13.38 bars at 
25.degree. C. within 30 percent of the HCFC-22 vapor pressure. The 
refrigeration capacity is substantially the same as the HCFC-22. The COP 
is 5.02. After 50 weight percent of the refrigerant is lost through the 
leakage of the vapor, the vapor pressure of the blend is 10.78 bars, 
within 4% of the HCFC-22 value. The refrigeration capacity has decreased 
to only 91% of the HCFC-22 value. The COP is now 5.31. Both the vapor at 
54 volume percent HFC-32 and the liquid at 37 volume percent HFC-32 has 
remained nonflammable as seen from FIG. 1. 
Having described the invention in detail and by reference to preferred 
embodiments thereof, it will be apparent that modifications and variations 
are possible without departing from the scope of the invention defined by 
the claims.