EPA/3G0/A-95/DH 3
Evaluation of HFC-245fa as a Potential Alternative for CFC-11
in Low Pressure Chillers
by
N. Dean Smith
Air and Energy Engineering Research Laboratory
U. S. Environmental Protection Agency
and
Angelita S. Ng, Michael W. Tufts, Ann M. Drago, and Krich Ratanaphruks
Acurex Environmental Corporation
It has been reported previously that HFC-245ca (1,1,2,2,3 -pentafluoropropane) has numerous
attributes which make it an attractive candidate alternative for CFC-11 and HCFC-123.1 In the present
paper, results of an initial evaluation of HFC-245fa (1,1,1,3,3-pentafluoropropane) are described together
with updated results of HFC-245ca testing.
HCFC-123 (l,l-dichloro-2,2,2-trifluoroethane) is currently the only alternative refrigerant for
low-pressure CFC-11 chillers. This chlorine-containing alternative is scheduled for a production cap
beginning in 1996 followed by a production phase-down through the year 2030 at the end of which
production must cease. This phaseout timeframe is expected to allow new equipment designed for use
with HCFC-123 and placed into service in the next few years to be utilized over the useful lifetime of Ihe
equipment. Meanwhile, the search for a long-term alternative continues.
Thermophysical Properties
HFC-245fa was first prepared in laboratory quantities by researchers at Clemson University in a
project sponsored by the EPA's Air and Energy Engineering Research Laboratory (AHF.RL). The
laboratory method involved hydrogenation of 1,1,1,3,3-pentafluoropropene in the presence of a
palladium/carbon catalyst:
Pd/C
CF3CH=CF2 + h2	> CF3CH2CF2H
This synthesis route resulted in production of 99.8 percent pure HFC-245fa with a 98 percent yield.
Thermophysical properties were initially determined with this material. Under the sponsorship of
AF.F.RL, work is in progress by the National Institute of Standards and Technology (NIST) to refme and
expand the thermophysical property database for HFC-245fa. Table 1 compares some of the pertinent
properties of HFC-245fa with those of HFC-245ca, CFC-11, and HCFC-123. A rather complete
compilation of the thermophysical properties of HFC-245ca is already available in the NIST REFPROP
database.^
Chiller Performance Modeling
HFC-245fa's performance as a refrigerant in low-pressure centrifugal chillers was assessed using
a computer model based on the Camahan-Starling-DeSantis-Morrison (CSDM) equation of stated This
model allowed analysis of a simple theoretical vapor compression cycle consisting of constant pressure
evaporation, isentropic compression, constant pressure condensation, and adiabatic expansion. Table 2
compares the results of chiller performance modeling for HFC-245fa, HFC-245ca, CFC-11, and HCFC-
123 at an evaporating temperature of 4.4°C (40°F), a condensing temperature of 40°C (104°F), and an
assumed compressor efficiency of 1.0. Modeling results are accurate to ± 2 percent.

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Table 1. Comparison of Thermophysical Properties for HFC-245fa, HFC-245ca, CFC-11, and HCFC-123

HFC-245fa
HFC-245ca
CFC-11
HCFC-123
Molecular weight
134.1
134.1
137.4
152.9
Normal boiling point, T^ (°C)
15.2
25.0
23.8
28.0
Heat of vaporization @ Tj, (kJ/mol)
28.0
29.2
24.8
25.7
Critical temperature (°C)
157.5
174.4
198.0
183.9
Critical pressure (kPa)
3623
3860
4409
3674
Critical density (kg/m^)
529
529
554
550
Sat'd liquid density @ 25°C (kg/m3)
1323
1386
1476
1465
Sat'd vapor density @ 25°C (kg/m^)
8.45
5.67
5.86
5.9
Vapor pressure @ 2S°C (kPa)
147
102
106
91
Table 2. Comparison of Modeled Refrigeration Performance for HFC-245fa, HFC-245ca, CFC-11, and
HCFC-123. Simulation Condition: 4.4°C - evaporating; 40°C-condensing; minimum superheat; 0.0°C
subcooling	


Volumetric
Suction
Discharge
Minimum

Coeff. of
Capacity
Pressure
Pressure
Superheat
Refrigerant
Perform.
(kJ/m3)
(kPa)
(kPa)
(°C)
HFC-245fa
6.7
594
62.7
246
1.4
HFC-245ca
6.6
403
42.0
173
3.8
CFC-11
7.0
463
48.7
175
0.0
HCFC-123
6.9
386
39.9
155
1.0
This analysis indicates a 4 to 5 percent lower efficiency for HFC-245fa compared to CFC-11 in a
centrifugal chiller operating at these conditions. By comparison, HFC-245ca shows an efficiency loss of 5
to 6 percent and HCFC-123 an energy penalty of 1 to 2 percent relative to CFC-11. For all alternatives,
the thermodynamic analysis indicates the possibility of wet compression; that is, refrigerant leaving the
compressor would be in both vapor and liquid states. HFC-245fa is predicted to require 2.4 degrees less
superheat than HFC-245ca to avoid wet compression. In actual practice, inefficiencies in compressor
operation are likely to result in sufficient superheating to avoid wet compression. Another advantage of
HFC-245fa is its volumetric capacity which is the highest of the four refrigerants compared. However, the
slightly higher discharge pressure of HFC-245fa compared to the other refrigerants suggests the need for
pressure-coded vessels when using this refrigerant
Flammahilitv
HFC-245fa can exhibit weakly flammable behavior in ASTM E681-85 or ASHRAE Standard
34-1992 flammability tests. As indicated in Figure 1, HFC-245fa is less flammable at room temperature
than even HFC-245ca, but like HFC-245ca, the flammability of the "fa" isomer is markedly dependent on
humidity. The dashed line in Figure 1 indicates the point at which the refrigerant/air mixture just
achieves the flammable limit with a spark ignition source as defined by the ASTM standard method.
2

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Figure 1. Effect of Moisture on Flammability of
HFC-245ca and HFC-245fa
§
as
CQ
E
HFC-24Sca
HPC-24Sfa
10 20 30 40 50 60 70
Relative Humidity (%)
80
90
100
A plausible explanation of the observed humidity effect for these and other weakly flammable
HFC refrigerants having a hydrogen-to-fluorine atom ratio less than unity is that such refrigerants require
an additional source of hydrogen atoms in order to combust completely to carbon dioxide and hydrogen
fluoride. The most likely source of additional hydrogen atoms in a combustion scenario is water vapor.
In the absence of water vapor or at low humidities, an alternate but less thermodynamically favored
combustion reaction is possible yielding carbonyl fluoride as one of the products. Balanced chemical
equations and associated free energies of combustion for the alternative combustion reactions of both
HFC-245fa and HFC-245ca are shown below. Free energies of combustion were calculated using free
energies of formation of HFC-245fa and HFC-245ca estimated by the method of Domalski and Hearing.^
As the moisture level increases in the refrigerant/air mixture, the more thermodynamically favored
combustion reaction (i.e., the reaction with the more negative free energy change, A G) can occur and the
HFC exhibits greater flammability.
HFC-245fa
CF3-CH2-CF2H + 5/202 + H20 —> 3C02 + 5HF
CF3-CH2-CF2H + 5/202 —> 2C02 + 3HF + COF2
AG =-1,297 kJmol"1
A G = -1,148 kJ mol"1
HFC-24ta
CF2H-CF2-CFH2 + 5/202 + H20 —> 3C02 + 5HF
CF2H-CF2-CFH2 + 5/202 —> 2C02 + 3HF + COF2
AG =-1,355 kJmol"1
AG=-1,207 kJmol"1
Smaller combustion free energies for HFC-245fa compared to HFC-245ca are indicative of a
lesser tendency for HFC-245fa to burn, a fact which is borne out by the results of the ASTM or ASHRAE
flammability tests. At a relative humidity of approximately 50 percent at room temperature (25 to 30 °C),
HFC-245fa was found to exhibit a flammable range of 8.9 to 11.2 volume percent in air.
Miseihilitv. Stability, and Materials Compatibility
Sealed tube samples were prepared containing 10,20, and 30 weight percent HFC-245fa in a
fully formulated, commercially available, polyolester lubricant of nominal 68 centistokes viscosity and
containing 50 ppm water. These samples were subjected to a gradual temperature change over the range
3

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of -40 to + 10Q°C to test for refrigerant/lubricant miscibility. HFC-24Sfa and HFC-245ca were found to
be completely miscible in the polyolester lubricant over this temperature range.
To test its temperature and hydroiytic stability, HFC-245fa was sealed in glass tubes alone, with
added polyolester lubricant, and with added water (0.001 ppm) in the absence and in the presence of
aluminum, steel, and copper. These samples were then subjected to sustained heating at 175°C for 14
days. Following the heating period, the samples were analyzed for possible degradation of the HFC-245fa
using a combination of gas chromatography, Fourier-transform infrared spectrometry, and mass
spectrometry. Chromatograms and spectra of the aged refrigerant and lubricant were identical to those of
the imaged materials indicating no degradation of the HFC-245fa or polyolester.
A large matrix of elastomeric and plastic materials were tested for compatibility with HFC-245fa
with and without the polyolester lubricant Materials tested for compatibility included 13 elastomers, 4
desiccants, and 5 metals. A complete list of these materials is presented in Table 3.
Table 3. Materials tested for Compatibility with HFC-245fa at 125°C
Brass
Bronze
Stainless steel
HNBR (hydrogenated nitrile butyl rubber)
Hypalon1" (chlorosulfonated polyethylene)
Natural rubber (isoprene polymer)
Thiokol™ (dicholorodiethylformal + alkali polysulfide)
Geolastm (nitrile/polypropylene 701-70)
NBRS (butadiene styrene copolymer)
E-70 (ethylene propylene diene methylene rubber)
S-70 (silicone rubber)
Neoprene™ (chloroprene)
Buna-N™ (nilrile)
Kalrez Cm (perfluoroelastomer)
Viton™ (fluoroelastomer)
Tenon1"
Desiccant 4 AXH-5
Desiecant 4 AXH-6
Desiccant XH-7
Desiccant XH-9
Again, no evidence was found for degradation of either the refrigerant or lubricant with any of these
materials. Several of the elastomers, however, were found to be incompatible with HFC-245fa. Figures 2-
4 present the elastomer results graphically. Thiokol results are not shown for the volume and linear swell
measurements due to the brittleness of the aged material which made it difficult to obtain data.
4

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Figure 2: Average Percent Volume Change of Elastomers
gp
X!
u

~ without oil
with oil
Figure 3: Average Percent Linear Swell of Elastomers
30.0
25.0
$ 20.0
% 15.0
cr>
U
.a
-j
10.0
5.0
0.0
-5.0





H without oil
¦ with oil












ec
ea
z
X
a
a
¦a
o.
s
•O
5
«
a
c«
06
es
z,
o
I
w
o
i
ID
c
0>
u
cu
s
Z
as
a
a
CQ
s
a>
CQ
a
©
a
c
c
a>
H
V)
JX
*©
a»
5

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Figure 4: Average Percent Hardness Change of Elastomers
20.0
1S.0
* 10.0
& 5.0
1 o.o
-5.0
% -10.0
| -15.0
a -20.0
-25.0
-30.0
Based on acceptable criteria being a volume increase of not greater than 20 percent, a linear swell
of not greater than 5 percent, no shrinkage, and a change in hardness of not more than +10 percent, only a
few elastomers were judged to be compatible. Table 4 summarizes the compatibility test results.
Table 4. Compatibility Summary of Elastomers Exposed to HFC-245fa and Lubricant

Linear Swell
Volume Change

Hardness Change

without oil
with oil
without oil
with oil
without oil with oil
HNBR
pass
fail
pass
pass
pass
pass
Hypalon
fail
pass
fail
pass
pass
pass
Nat. rubber
fail
fail
fail
fail
pass
fail
Thiokol
fail
fail
fail
fail
fail
fail
NBRS
fail
fail
fail
pass
pass
pass
E-70
fail
pass
fail
pass
pass
pass
S-70
fail
pass
fail
fail
pass
pass
Neoprene
fail
fail
pass
fail
pass
pass
Buna-N
pass
pass
pass
fail
pass
fail
Kalrez C
fail
fail
fail
pass
fail
fail
Viton
fail
fail
pass
pass
pass
fail
Teflon
fail
fail
pass
pass
n/a
n/a
Geolast
pass
pass
pass
pass
pass
pass
n/a = not applicable
Geolast passed the volume, linear swell, and hardness tests in the presence of refrigerant alone
and in the presence of combined refrigerant/lubricant HNBR and Buna-N passed all three compatibility
criteria in the presence of refrigerant alone but failed at least one test in the presence of lubricant.
Hypalon and E-70 passed all three compatibility criteria in the presence of combined refrigerant/lubricant
but failed at least one test in the presence of refrigerant alone. Pass/fail criteria used here are somewhat
arbitrary; therefore, some elastomers which may have failed one or more of the criteria used here may in
fact be suitable for a specific application. Note, for example, that elastomer E-70 exceeded the volume
change criterion only in the absence of the lubricant and then by exhibiting a volume decrease of only
0.61 percent.
~ without oil
¦ with oil
a
X
a
©
®
o
Z
V
A
a
©
6

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Based on visual observations, there was no indication of any deterioration of the desiccants or
copper plating on the metals.
Atmospheric Stability and Global Warming Potential
Although HFC-245fa has zero ozone depletion potential, it was of interest to estimate its
atmospheric lifetime as an indication of the global warming potential of the refrigerant. To this end, the
reaction rate constant was determined for the reaction of HFC-245fa with hydroxy 1 (OH) radical. This
work was performed by NIST under the sponsorship of AEERL. The measured OH rate constant was
determined to be 5.3 x 10"^ cm^ molecule"* sec"' at 277 K. Comparing this rate constant to that of
methyl chloroform (6.5 x 10"*^ cm^ molecule"* sec"*), whose tropospheric lifetime due solely to OH
removal is known to be 7.0 years, gives an estimated tropospheric lifetime for HFC-245fa of 8.6 years.
This is slightly longer than the 6.3 year lifetime of HFC-245ca previously determined by NIST.^ Both
HFC-245ca and HFC-245fa have tropospheric lifetimes which compare favorably with that of HFC-134a
(15.5 years) and suggest a halocarbon global warming potential (HGWP) for both HFC-245 isomers,
roughly 50 percent that of HFC- 134a.
Summary and Conclusions
HFC-245fa has been shown in laboratory testing and modeling performed to date to be a good
potential long-term replacement refrigerant for CFC-11 or HCFC-123 in low pressure chillers. Computer
modeling of chiller systems using HFC-245fa indicates that reduced energy efficiencies on the order of 4
to 5 percent may occur relative to CFC-11.
On the basis of testing with a single polyolester lubricant, such lubricants appear to afford
excellent compatibility and miscibility with HFC-245fa. Of the 13 different elastomeric materials tested,
3 gave acceptable compatibility in the presence of combined refrigerant/lubricant and 3 gave acceptable
compatibility in the presence of the refrigerant alone. HFC-245fa was found to be thermally and
hydrolytically stable under all test conditions.
Flammability testing of HFC-245fa showed the refrigerant to be weakly flammable at room
temperature and then only at relative humidities above approximately 50 percent. Upper and lower
flammability limits at room temperature and 50 percent relative humidity were found to be 8.9 and 11.2
volume percent HFC-245fa in air, respectively, using a spark as the ignition source.
HFC-245fa has zero potential to deplete stratospheric ozone. Its atmospheric lifetime, estimated
from its measured reaction rate with OH radical, is 8.6 years. This lifetime corresponds to a halocarbon
global warming potential roughly 50 percent that of refrigerant HFC-134a.
Due to limited supplies of HFC-245fa available for testing, essentially no toxicological
information is known for the refrigerant. However, based on its molecular structure and on toxicity
information known for isomers of other HFCs, it is believed that HFC-245fa will exhibit lower toxicities
than HFC-245ca. The latter refrigerant was previously tested for acute inhalation toxicity on rats using a
4-hour exposure at 993 ppm and was found to yield no ill effects.
References
1.	Smith, N. D„ K. Ratanaphruks, M.W. Tufts and A. S. Ng,R-245ca: A Potential Far-Term
Alternative for R-ll, ASHRAE Journal, Vol. 35, No. 2, pp. 19-23, February 1993.
2.	NIST Standard Reference Database 23, Thermodynamic Properties of Refrigerants and Refrigerant
Mixtures (REFPROP), National Institute of Standards and Technology, 1994,Gaithersburg, MD 20899.
7

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3.	Kazachki, G. S. and C. L. Gage, Thermodynamic Evaluation and Compressor Characteristics of HFC-
236ea and HFC-245ca as CFC-114 and CFC-11 Replacements in Chillers, International CFC and Halon
Alternatives Conference, Washington, DC, October 20-22,1993.
4.	Domalski, E. S. and E. D. Hearing, Estimation of the Thermodynamic Properties of C-H-N-O-S-
Halogen Compounds at 298.15 K, J. Phys. Chem. Ref. Data, Vol. 22, No. 4, pp. 805-1159,1993.
5.	Zhang, Z. et al., Reactions of Hydroxyl Radicals with Several Hydrofluorocarbons: The Temperature
Dependencies of the Rate Constants for CHF2CF2CH2F (HFC-245ca), CF3CHFCHF2 (HFC-236ea),
CF3CHFCF3 (HFC-227ea), and CF3CH2CH2CF3 (HFC-356ffa), J. Phys. Chem., Vol. 98, No. 16,
pp.4312-4315, April 1994.
8

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„ TECHNICAL REPORT DATA
A E ER1P-1213 (Please read inslruetions on the reverse before complclti
1, REPORT no. 2.
EPA/600/A-95/013
3, R
4. title and subtitle
Evaluation of HFC-245fa as a Potential Alternative
for CFC-11 in Low Pressure Chillers
S, REPORT DATE
6. PERFORMING ORGANIZATION CODE
7 autmoris! N< Smith (EPA/AEERL) and A. Ng, M. Tufts,
A.Drago, and K. Ratanaphruks (Acurex)
8. PERFORMING ORGANIZATION REPORT NO,
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Acurex Environmental Corporation
P. 0. Box 13109
Research Triangle Park, North Carolina 27 709
10. PROGRAM ELEMENT NO.
11- CONTRACT/GRANT NO.
68-D4-0005
12- SPONSORING AGENCV NAME AND ADDRESS
EPA, Office of Research and Development
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
13. TYPE Of REPORT AND PERIOD COVERED
Published paper; 11/93-8/94
14. SPONSORING AGENCY COOE
EPA/600/13
15. supplementary notes ^EERL project officer is N. Dean Smith, Mail Drop 62B, 919''541-
2708. Presented at 1994 International CFC and Halon Alternatives Conference, Wash-
ington, DC, 10/24-26/94.
16. ABSTRACT
¦The paper reports results of an evaluation of HFC~245fa as a potential alternative
for CFC-11 in low pressure chillers.—(NOTE; It was reported previously that HFC-
245ca (1,1, 2, 2, 3-pentafluoropropane) has many attributes that make it an attractive
candidate alternative for CFC-11 and HCFC-123.)- This paper gives results of an ini-
tial evaluation of HFC-245fa (1,1,1, 3, 3-pentafluoropropane) and updated results of
HFC-245ca testing. HCFC-123 (1, l-dichloro-2, 2, 2~ trifluoroethane) is currently the
only alternative refrigerant for low pressure CFC chillers. This chlorine-containing
alternative is scheduled for a production cap beginning in 1996, followed by a produc-
tion phase-down through the year 2030, at the end of which production must cease.
This phaseout timeframe is expected to allow new equipment designed for use with
HCFC-123 and placed into service in the next few years to be utilized over the useful
lifetime of the equipment. Meanwhile, the search for a long-term alternative con-
tinues. '
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c, cosati Field/Group
Pollution
Coolers
Refrigerants
Halohydrocarbons
Substitutes
Pollution Control
Stationary Sources
Chillers
Alternatives
13 B
13 A
07 C
14G
IB. DISTRIBUTION STATEMENT
Release to Public
19, SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)

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