EPA/600/A-92/128
PREDICTIONS OF AZEOTROPES FORMED
FROM FLUORINATED ETHERS, ETHANES, AND PROFANES
Cynthia L. Gage
U.S. Environmental Protection Agency
Air and Energy Engineering Research Laboratory
Georgi S. KazaehM
Aeurex Environmental Corporation
ABSTRACT
The synthesis of new non-chlorinated refrigerants expands the base of alternatives for
replacing ozone-depleting ehlorofluorocarbons (CFCs) and their first-generation replacements,
hydrochlorofluorcarbons (HCFCs). Besides the direct use of these refrigerants, there is also the
potential to combine them with other compounds to form blends. In this work, the potential for
azeotrope formation and performance was evaluated for fluorinated ethers, ethanes, and propanes.
Azeotrope formation was predicted using an interaction parameter for the mixture which
was based on the dipole moments and volumes of the components. Dipole moments for the new
compounds were predicted from the molecular structure. Of 20 fluorinated ether and hydrocarbon
pairs tested, seven were found to form azeotropes. Results from this work predicted azeotropes
with boiling points between -46°C (~52°F) and -19°C (~2°F), indicating potential replacements
for CFC-12 and R-502, an azeotrope of HCFC-22 and CFC-115. Azeotrope performance in vapor-
compression cycles was then evaluated.
INTRODUCTION
Ozone depletion has inspired intensive research to identify chemicals to replace the CFCs
which break down in the stratosphere and deplete ozone. This research begins with the
identification of replacement chemicals through property analysis and ends with the optimization of
systems to use these chemicals. Early on, the Environmental Protection Agency (EPA) and the
Electric Power Research Institute (EPRJQ recognized that at the time there were not many chemical
options to choose from, and thus, they jointly funded work at two universities to synthesize new
fluorinated ethers and propanes (1). This work identified 39 compounds for which some property
data were collected. The work presented in this paper extends the use of the new chemicals through
identification and evaluation of potential azeotropes formed from these chemicals and other known
alternatives. Since it is expected that all chlorine containing refrigerants will be banned from
production, only azeotropes without chlorine are discussed.
BACKGROUND AND OBJECTIVES
Synthesis of the new chemicals has expanded the choices to replace the ozone-depleting
CFCs and HCFCs. Table 1 lists the existing chlorine-free hydrofluorocarbons (HFCs) and some
hydrocarbons (HCs) with their normal boiling points. Also shown are the newly synthesized
refrigerants, HFCs and hydrofluoroethers (HFEs) which are being evaluated by EPA. This table
only contains compounds which have boiling points in the range from -52°C (-62°F) to 25°C
(77°F). This range covers the boiling points of the following chlorine-containing compounds:
HCFC-22, CFC-12, HCFC-124, HCFC-142b, CFC-114, CFC-11, HCFC-123, and the
azeotrope refrigerants, R-500 and R-502. Compounds which are known to be flammable are
indicated by italics. Hammability tests on the new chemicals are being performed by EPA. Based
on the ratio of hydrogen to fluorine in these chemicals, most are expected to be nonflammable.

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Table 1: Non-Chlorinated Refrigerant Options and Their Normal Boiling Points, Tnbp
(Italics indicate compounds known to be flammable.)
Existing Chemical
T^pX-CEl
New Chemical
HFC-32
-52
(-62)

HFC-125
-49
(-56)

HFC-143a
-48
(-54)

HC-290 (.Propane)
-42
(-44)


-35
(-31)
HFE-125
HC-270 (Cyclopropane}
-33
(-27)

HFC-134a
-26
(-15)

HFC-152 a
-24
(-11)
HFE-143a
HFC-134
-20
(-4)


-18
(0)
HFC-245cb

-16
(3)
IIFC-227ca

-15
(5)
RFC-227ea
HC-600a (Isobutane}
- 6
(21)

HC-600 (Butane)
- 1
(30)
HFC~236cb, HFC-236fa, HFC-254cb
HFC-143
5
(41)


7
(45)
HFC-236ea

15
(59)
HFC-245fa

25
(77)
HFC-245ca
Many of the theoretical evaluations which have been performed on the alternative
refrigerants use the Camahan-Starlmg-DeSantis (CSD) equation-of-state (2). This work has
resulted in several cycle codes which use this equation-of-state and many of the associated
subroutines for the calculation of refrigerant properties. These codes involve various levels of
simulation complexity from the simple cycle at saturated conditions to systems which incoiporate
some equipment details (3-6).
For mixtures, the use of the CSD equation requires the specification of an interaction
parameter which is specific to the refrigerant pair. This parameter accounts for the interaction of
the pure component's molecules in the mixture. In the studies mentioned above which evaluated
mixtures, the unknown interaction parameters of the mixtures were set at the same value.
Interaction parameters have been measured for several of the CFC refrigerant pairs (2).
However, the parameters for most combinations, especially for the alternative refrigerants, have
been neither measured nor estimated. The lack of reliable data for the interaction parameter has
been a hindrance to the research. In the search for alternative compounds, the initial steps involve
preliminary thermodynamic evaluations in order to prescreen the options. Without interaction
parameters it is impossible to evaluate mixtures to perform this prescreening. This implies that it
would be necessary to test all possible combinations in order to gather the interaction parameters
for use in screening. This would be a sizeable task and would in the end yield data for
combinations which may not be pursued because of poor performance predicted during the
prescreening. Therefore, it became clear that a method of estimating the interaction parameter was
needed.
This work addresses the search for better alternative refrigerants in terms of capacity,
efficiency, and flammability. The objectives include the development of a method for predicting
interaction parameters, the prediction of azeotropes from the non-chlorinated refrigerants included
in Table 1, and the evaluation of these azeotropes in vapor-compression cycles.
2

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METHOD OF PREDICTION
Using the data from measured interaction parameters, an empirical correlation was
developed based on the nature of molecular interactions in mixtures. This correlation expresses the
interaction parameter as a function of dipole moments and volumes for the refrigerant pair. These
variables were chosen based on several considerations. In the mixing of real fluids, the properties
of the mixtures are affected by the ability of the molecules to form weak links. In this case, the
bonds of interest are those that occur from dipole-dipole attractions. For dipole-dipole interactions,
the force varies with the difference in the dipole moments and 1/r3, where r is the distance between
the molecules. Since this force operates in three dimensions (i.e., within a volume), it indicates
; that a correlation which is inversely proportional to molecular volume can be expected. The CSD
equadon-of-state uses a parameter, b, which represents the average closest approach of the
molecules and has units of volume (2). Although the prediction method is not tied to the CSD
equation-of-state, this equation is widely used and, therefore, the parameter "b" can be chosen as
the representative volume. The following equation shows the general correlation which was
assumed to express the interaction parameter:
f12 =A+B(ADP) -rC(ADP)2 + D/(V!V2)
where
ADP = (dipole moment of the low boiler) - (dipole moment of the high boiler),
V] = molecular volume for the low boiler, and
V2 = molecular volume for the high boiler.
It should be noted that this expression neglects any dependence on the temperature, while
earlier work indicates that for a few compounds there may be a temperature dependence of the
interaction parameter (2).
Interaction parameters for 22 refrigerant pairs were used to regress the coefficients of the
interaction parameter expression. Four of these refrigerant pairs are azeotropes. The values of ail
measured interaction parameters ranged from -0.014 to 0.12. For the molecular volumes, the
individual "b" parameters calculated from the CSD equation-of-state were used as the
representative volumes. These parameters lead to the following values for the coefficients:
The expression for fu has been used to calculate the interaction parameter for more than
100 refrigerant pairs. It has been noted that For a few pairs, which include a compound with a zero
dipole moment, the correlation predicts an interaction parameter which falls significantly out of the
range of observed values. Therefore, when the correlation predicted values much greater than
0.12, a value for fj2 of 0.12 has been used.
The correlation shown above between the dipole moments, volumes, and the interaction
parameter was successfully used in 1990 to predict the formation of an azeotrope between HFC-32
and HFC-125 (7). The existence of this azeotrope was later confirmed by Allied-Signal (8). In
this work, the correlation was used to predict azeotropes of recently synthesized fluorinated
compounds.
A = -0.0105822
C =0.033164561
B = 0.1988274
D = 0.000102909
AZEOTROPE PREDICTION
3

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Table 2: Pure Component Parameters for Compounds Which Formed Azeotropes
Compound	Dipote Moment Reference
Volume
(debeye)
(rrfVkmol) (ft3/lbmol)
HFC-134a
'HFC-134
HFC-152a
HC-270
HFE-143a
HFE-125
HFC-245cb
HFC-227ea
2.058
0.991
2.262
0
2.45
2.55
2.44
2.05
(11)
(11)
(11)
(12)
(10)
(10)
(10)
(10)
0.0873	(1.400)
0.0873	(1.400)
0.0795	(1.275)
0.0721	(1.156)
0.0810	(1.299)
0.0987	(1.582)
0.1192	(1.911)
0.1244	(1.994)
Since dipole moments have not been measured for the new chemicals, it was necessary to
estimate their values. Dipole moments were calculated using the Modified Neglected Differential
Overlaps method (9). Using known dipole moments for nine carbon-fluorine molecules, the C-F
bondlengths were optimized to give a fit to the known compounds with an average deviation of
about 4 percent (10). The 'optimized' bondlengths were then used to calculate the dipole moments
of the new chemicals. The predicted dipole moments as well as the dipole moments of the other
components of the azeotropes are shown in Table 2. Also shown are the volumes calculated at
298K (537°R) using the temperature dependence expression for the CSD parameter, b. For some
compounds, dipole moments are a function of temperature (11). When this occurs, the value
reported for 298K (537°R) has been used in the prediction of the interaction parameter.
Once die interaction parameters were estimated, potential azeotropes containing the new
chemicals were evaluated. Using up to 10 degrees difference in normal boiling points as pairing
criteria, 20 refrigerant pairs were initially selected for screening. Applying the CSD refrigerant
property routines, dew points and bubble points were calculated for each refrigerant pair between
-40°C (~40°F) and +20°C (68°F) and across the composition range. An azeotrope was identified
when both the vapor composition at the bubble point and the liquid composition at the dew point
matched the specified composition. Of the more than 20 pairs which were screened, seven
indicated azeotropic formations. Table 3 lists these compounds along with their estimated
interaction parameters, compositions, normal boiling points, Tnbp, and critical temperatures, Tc.
Critical temperatures were estimated using the correlation of Li which was shown to predict the
critical temperatures of 10 other refrigerant azeotropes within 3°C (5.4°F) (13). The pressure
dependence of the azeotrope compositions is shown in Figure 1. Here the pressure is represented
by the saturation temperature. In the future, the existence of these azeotropes will be tested in the
EPA laboratory.
Two of the azeotropes, HFE-143a/HFC-152a and IIFE-125/HC-270, contain known
flammable components. It would be hoped that the formation of the azeotrope would suppress the
flammable characteristics. This is true for the R-500 azeotrope which is formed from 26 percent
HFC-152a and 74 percent CFG-12 (13). The potential, fiammability of these mixtures will also be
evaluated in the EPA laboratory.
EVALUATION OF THE PREDICTED AZEOTROPES AS REFRIGERANTS
The boiling points of the seven predicted azeotropes indicate potential replacements for
CFC-12,11CFC-22, and R-502. The cycle efficiency, volumetric capacity, and the temperature at
the end of isentropic compression were compared to evaluate the potential performance of the
4

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Table 3: Predicted Azeotropes and Their Critical Temperatures
Azeotrope Pair Mass Ratio Si2-	__Inbp		T^



°C
(°F)
°C
(°F)
HFE-125/HC-27Q
0.77/0.22
0.1200
-46.5
(-51.7)
66
(151)
HFE-125/HFC-l 34a
0.81/0.19
0.0681
-39.1
(-38.3)
75.
(167)
HFE-143a/HFC~134
0.55/0.45
0.1025
-30.3
(-22.6)
91"
(196)
HFC- 134a/HFE- 143a
0.66/0.34
0.0174
-26.7
(-16.1)
101
(214)
HFE-143a/HFC-152a
0.56/0.44
0.0067
-24.9
(-12.8)
107
(225)
HFC-134/HFC-245cb
0.53/0.47
0.0390
-23.2
(-9.7)
99
(210)
HFC-245cb/HFC-227ca
0.30/0.70
0.0092
-19.4
(-2.9)
100
(212)
azeotropes in vapor-compression cycles against their pure component constituents and against the
existing chemicals which they could replace. Here, the cycle efficiency is CQP/COPc, where COP
is defined as the cooling capacity divided by the work of compression, and COPc is (Tc-Te)/Te.
The simple cycle is defined by saturated liquid exiting the condenser, isenthalpic expansion,
saturated vapor exiting the evaporator, and isentropie compression. However, real systems do not
operate at these conditions. Domestic refrigerator/freezers (R/Fs) and supermarket systems are two
applications which have additional subcooling and superheating: R/Fs through suction-line heat
exchange, and supermarkets through mechanical subcooling and the unavoidable heat gains
occurring in the long lines between the evaporator and the compressor. Recent work has shown
that the losses associated with expansion and compression superheating are strongly dependant on
the refrigerant's properties (14,15). This has significant implications when making comparisons
for real systems where additional subcooling and superheating may occur because of internal heat
exchange, ambient heat gains or losses, or direct addition of subcooling. A more detailed
thermodynamic analysis of the azeotropes across a wider range of operating conditions has also
been performed (16).
For this analysis, the applications of supermarkets and domestic R/Fs are of interest. The
two low-boiling ether azeotropes were evaluated at operating conditions chosen to simulate
supermarket systems. These conditions include 43°C (11G°F) condensing temperature,
5C°(9F°) condenser subcooling, mechanical subcooling of the liquid to 12.8°C (55°F),
5C°(9F°) evaporator superheating, and ambient heat gains to bring the suction vapor temperature
to 18.3°C (65°F). A range of evaporating temperatures was chosen to include conditions for ice
cream cases and frozen foods. For these conditions, supermarkets presently use either R-502 or
HCFC-22.
Figures 2 to 4 show the predicted results for the HFE-125 azeotropes, their pure
components, R-502, and HCFC-22. In Figure 2, which shows the efficiency of the cycle relative
to Camot, the performances of both azeotropes are between the performances of their pure
components. This figure indicates that the efficiencies of both ether azeotropes are very close to
that of R-502. Figure 3 indicates that the volumetric capacity of the HFE-125/HC-270 azeotrope is
also very similar to those of R-502 and HCFC-22, while the HFE- 125/HFC-l 34a azeotrope and
the pure components have much lower capacities. Figure 4 shows that both azeotropes have lower
compressor discharge temperatures than R-502 and HCFC-22. Another important parameter to
consider in low temperature systems is the suction pressure. The only compounds which operated
above atmospheric pressure at all evaporating temperatures were R-502, HCFC-22, and
HFE-125/HC-270.
The remaining five azeotropes were evaluated as replacements for CFC-12. The operating
conditions were 43°C (110°F) condensing temperature with internal heat exchange applied to
5

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increase the suction vapor temperature to 18.3°C (65°F). A range of evaporating temperatures
were chosen to include conditions for domestic R/Fs and supermarket cases for dairy products,
produce, and frozen meats. The performance results are shown in Figure 5, and the volumetric
capacities are shown in Figure 6.
Figure 5 shows that only one azeotrope, HFE-143a/HFC-152a, outperforms CFC-12.
This is an azeotrope whose pure components also outperform CFC-12. Two other azeotropes
have performances close to CFC-12. Figure 5 indicates that for two of the azeotropes,
HFC-134a/IIFF.-143a and HFE-143a/HFC-134, the pure components outperformed their
respective mixtures. The evaporator inlet qualities for these azeotropes were higher than those for
their pure components, where the quality is defined as the mass of vapor ratioed to the total mass.
For the other three azeotropes, whose performances were between the pure components, the
qualities were also between those of their pure components. Higher evaporator inlet qualities are
indicators of higher throttling losses. It has been shown previously that refrigerants which have
high throttling losses will be those which can gain the most from additional internal heat exchange
(15). It was also demonstrated in the same work that it is important to compare refrigerants not in
the same cycle but rather between cycles which have been tailored to the refrigerant properties.
Thus this comparison should be performed before any refrigerant is rejected from further
consideration.
Figure 6 shows the volumetric capacities for the azeotropes and their pure components.
Here the IIFE-143a/HFC-152a azeotrope is seen to have lower capacity than CFC-12, while the
capacity of the HFC-134a/HFE- 143a azeotrope is close to those of both CFC-12 and HFC-134a.
The suction pressures of three of the azeotropes were high enough that they could be expected to
operate above atmospheric pressure at R/F conditions. Two azeotropes, HFC-134/HFC-245cb
and HFC-245cb/HFE-227ea, would probably operate under vacuum at these conditions.
Discharge temperatures for all of the azeotropes were found to be lower than that for CFC-12.
CONCLUSIONS
1.	A method was developed for evaluating interaction parameters of mixtures as a function of
dipole moments and molecular volume.
2.	Seven new, non-chlorinated azeotropes were identified in the boiling point range of -46°C
(~52°F) to -19°C (-2°F).
3.	At operating conditions appropriate to supermarkets, two low-temperature ether azeotropes
(HFE-125/HFC- 134a and I IFE- 125/HC-270) have performance efficiencies near that of R-502,
and one azeotrope, HFE- 125/HC-270, has a volumetric capacity which also matches that of
R-502. Therefore, this azeotrope can be considered as an alternative and eventual replacement for
R-502.
4.	Three azeotropes (HFE-143a/HFC-152a, HFE-143a/IIl;C-134, and HFC-134a/HFE-143a)
have boiling points which would make them acceptable replacements for CFC-12. However, at
operating conditions close to those of refrigerator/freezers, none matched both performance and
volumetric capacity.
6

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ACKNOWLEDGEMENTS
The property determinations for the new chemicals were jointly funded with the Electric
Power Research Institute. The authors thank N. Dean Smith of EPA for providing supporting
information for this work, and they thank James A. Register IH of EPA for Ms participation in the
computer simulations.
REFERENCES
1.	Bare, J.C., N.D. Smith, and J.L. Adcock "New Chemical Alternatives to Chlorofluorocarbons
and Halons," Proceedings of 82nd Annual Meeting of Air and Waste Management Association.
Anaheim, 1989.
2.	Morrison, G, and M. O. McLinden, "Application of a Hard Sphere Equation of State to
Refrigerants and Refrigerant Mixtures," NBS Tech. Note 1226. National Bureau of Standards,
1986.
3.	Jung, D.S. and R. Radermacher, "Performance Simulation of Single-Evaporator Domestic
Refrigerators Charged with Pure and Mixed Refrigerants," Int. J. of Refrig..Vol. 14. No.4, 1991.
4.	Rice, C. K. and J.R. Sand, "Initial Parametric Results using Cyclez-An LMTD-Specified.
Lorenz-Meutzner Cycle Refrigerator/Freezer Model," Proceedings of the 1990 USNC/IIR-Purdue
Refrigeration Conference. West Lafayette, IN, July 17-20,1990.
5.	Jung, D.S. and R. Radenmacher, "Performance Simulation of Two-Evaporator Refrigerator-
Freezer Charged with Pure and Mixed Refrigerants," Int. J. of Refrig..VoI. 14. No.5,1991.
6.	Domanski, P.A. and M.O. McLinden, "A Simplified Cycle Simulation Model for the
Performance Rating of Refrigerants and Refrigerant Mixtures," Proceedings of the 1990
USNC/IIR-Purdue Refrigeration Conference. West Lafayette, IN, 1990.
7.	Gage, C.L. "Potential Refrigerant Alternatives for Supermarkets: Modeling Results,"
presentation at 1990 Int. CFC and Halons Alternatives Conference. Baltimore, 1990.
8.	ShanMand, I.R. and E.A.E. Lund, "Azeotrope-like Compositions of Pentafluoropropane and
Difluoromethane," U.S. Patent 4,987,467, Dec. 1990.
9.	Dewar, M.J. and W. Thiel, "MNDO Calculations for Fluorine Bonds," J. Am. Che. Soc,. Vol.
199, 1977.
10.	Private communication with K. Ratanaphunks, Acurex Environmental, RTP, NC (1991).
11.	Meyers, C. W. and G. Morrison, "Dipole Moments of Seven Partially Halogenated Ethane
Refrigerants". J. Phvs. Chem. Vol. 95. 1991.
12.	Reid, R.C., J.M. Prausnitz, and T.K. Sherwood, The Properties of Gases and Liquids.
McGraw Hill, New York, 1977.
13- Downing, R.C., Fluorocarhon Refrigerants Handbook. Prentice Hall, Inc, Englewood Cliffs,
NJ, 1988.
14.	Kazachki, G.S. "Derivation of Dimensionless Parameters for Thermodynamic Evaluation of
Refrigerants in Vapor Compression Cycles," Proceedings of the 18th International Congress of
Refrigeration. Commission B2, Montreal, 1991.
15.	Kazachki, G.S. and C.L. Gage, "Thermodynamic Evaluation of Five Alternative Refrigerants
in Vapor-Compression Cycles," Proceedings of the 18th International Congress of Refrigeration.
Commission B2, Montreal, August 1991.
16.	Kazachki, G.S. and C.L. Gage, "Thermodynamic Evaluation of Predicted Fluorinated Ether,
Ethane, and Propane Azeotropes," Proceedings of the 1992 USNC/IIR-Purdue Refrigeration
Conference. West Lafayette, IN, 1992.
7

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3®.
S-
R245cb/R227ea
R134/R245cb
«r— E125/R134a
Q.
£-10-
E125/RC270
E143a/R134
E143a/R152a
¦>— R134a/E143a
-20
-30
j r.
-40
' 1 '	1	• » » » ^ « I j ngir ,—Y—£—. —» .	^ ^	.
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Mass Fraction of First Component
-0.1
Figure 1; Dependence of Azeotrope Composition
on Temperature.
8

-------
0.85
o
CL

o

o
0.8
CL

o

o

II

>*
o
0.75
c

©

o

3=

lii

o
0.7
o



Mechanical Subeoollng
to 12.8°C
Return Gas at 18.3°C
0.85
-35	-30	-25	-20	-15
Evaporating Temperature (°C)
Figure 2; Performance of Low Temperature
Refrigerants at 43°C Condensing.
9

-------
2600
R22
O— R502
E125/R134a
E125/RC270
2400-
2200
E125
2000-
R134a
RC270
1800-
1600
m" 1400
¦z 1200
5 1000
800
600
400
Mechanical SubcooSing
to 12.8°C
Return Gas at 18.3°C
200
-35
-30
-25
-20
-15
-10
-40
Evaporating Temperature (°C)
Figure 3: Volumetric Capacity of Low Temperature
Refrigerants at 43°C Condensing.
10

-------
160
R22
R502
150
E125/RC270
140
E125
P.134a
RC27G
130
Q.
£ 120
100
CL
70-
MschanScal Subcooling
to 12.8°C
Return Gas at 18.3°C
-30
Evaporating Temperature (°C)
-25
-20
-40
-35
Figure 4: Compressor Discharge Temperature
at 43°C Condensing.
ii

-------
0.86
CL
o
o
£
o
o
II
>>
o
c
©
O
E
LU
O
o
>
O
-D- Hi 2
R134a/E143a
R245cb/R227ea
E143a/R134
E143a/R152a
R134/R245cb
R134a
R152a
R134
E143a
R245cfa
R227ea
Evaporating Temperature (°C)
Figure 5: Efficiency of Cycle with Internal Heat Exchange
at 43°C Condensing. Vapor Heated to 18,3°C,
12

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2500
R12
R134a/E143a
—s— R245eb/R227ea
E143a/R134
2000
E143a/R152a
R134/R245cb
R134a
R152a
R134
E143a
0.
R245cb
R227ea
1000
500
-30
-20	-15	-10	-5
Evaporating Temperature (°C)
-25
Figure 6: Volumetric Capacity with Internal Heat Exchange
at 43°C Condensing. Vapor Heated to 18.3°C.
13

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rtT:lT_,_,T nno TECHNICAL REPORT DATA
_A .Hi Hi-Ll J_(~ ir — y U O (Please read Instructions on the reverse before compter
1. REPORT NO. 2.
EPA/600/A-92/128
3.
4. TITLE AND SUBTITLE
Predictions of Azeotropes Formed from Fluorinated
Ethers, Ethanes, and Propanes
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
C. L. Gage (EPA/AEERL) and G. S. Kazachki
(A cur ex)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
A cur ex Environmental Corporation
P. O. Box 13109
Research Triangle Park, North Carolina 27709
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-D0-0141, Task 92-063
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air and Energy Engineering Research Laboratory
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Presented paper; 1-3/92
14. SPONSORING AGENCY CODE
EPA/600/13
is. supplementary notes AEERL project officer is Cynthia L. Gage, Mail Drop 62B, 919/
541-0590. Presented at 1992 Purdue Refrigeration Conference, W. Lafayette, IN,
7/20-23/92.
is. abstractpaper discusses an evaluation of the potential for azeotrope formation
and performance for fluorinated ethers, ethanes, and propanes. (NOTE: The synthe-
sis of new non~chlorinated refrigerants expands the base of alternatives for repla-
cing ozone-depleting chlorofluorocarbons (CFCs) and their first-generation replace-
ments, hydrochlorofluorocarbons (HCFCs). Besides the direct use of these refriger-
ants, there is also the potential to combine them with other compounds to form
blends.) Azeotrope formation was predicted using an interaction parameter for the
mixture which was based on the dipole moments and volumes of the components. Di-
pole moments for the new compounds were predicted from the molecular structure.
Of 20 fluoronated ether and hydrocarbon pairs tested, seven were found to form
azeotropes. Results from this work predicted azeotropes with boiling points between
-40 and -19 C (-52 and -2 F), indicating potential replacements for CFC-12 and R-
502, an azeotrope of HCFC-22 and CFC-115. Azeotrope performance in vapor-
compression cycles was then evaluated.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. cos ATI Field/Group
Pollution Refrigerants
Azeotropes Halohydrocarbons
Fluorohydrocarbons
Ethers
Ethane
Propane
Pollution Control
Stationary Sources
13 B 13 A
07D
07C
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)'
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)

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