EPA-600/R-97-117
October 1997
NEW CHEMICAL ALTERNATIVE FOR OZONE-DEPLETING SUBSTANCES:
HFC-236ea
By:
Theodore G. Brna, N. Dean Smith, Robert V, Hendriks, and Cynthia L. Gage
U. S. Environmental Protection Agency
National Risk Management Research Laboratory
Research Triangle Park, NC 27711
Prepared for:
U, S. Environmental Protection Agency
Office of Research and Development
Washington, DC 20460
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TECHNICAL REPORT DATA
(Please read fasiwctiora on the reverse before eom[.
nimiiiiii
PB98-1
iiiii mi
1. REPORT NO. i 2. 1
E PA - 600/R-9 7-117 [ <
IIIII 1 111
27384
4, TITLE AND SUBTITLE
New Chemical -Alternative for Ozone-Depleting
Substances: HFC-236ea
5, REPORT d4.TE
October 1997
6. PERFORMING ORGANIZATION CODE
7. author(s) Theodore G, Brna, N. Dean Smith, Robert V.
Eendriks, and Cynthia L. Gage
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
See Block 12
10, PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
NA (Inhouse)
12. SPONSORING AGENCY NAME ANO AOORESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT ANO PERIOD COVERED
Final; 11/96 - 3/97
14. SPONSORING AGENCY CODE
EPA/600/13
is. supplementary notes ^ppcD project officer is N. Dean Smith, Mail Drop 63, 919/541-
2708.
16. abstract Yhe report gives results of a preliminary evaluation of a new hydrofluoro-
carbon (HFC-236ea or 1,1,1,2, 3,3-hexafluoropropane) as a possible alternative for
chlorofluorocarbon (CFC)-114 (1, 2-dichloro-l, 1, 2, 2-tetrailuoroethane) refrigerant in
chillers and high-temperature industrial heat pumps. (NOTE; HFCs form a class of
chemicals having the potential to replace stratospheric ozone depleting substances
such as CFCs and hydrochlorofluorocarbons (HCFCs).) Evaluation tests included an
examination of the flammability, stability, thermophysical properties,. lubricant/re-
frigerant characteristics, materials compatibility, inhalation toxicity, and refriger-
ation performance. HFC~236ea was found to be an excellant alternative for CFC-114
refrigerant.
17. KEY WORDS AND DOCUMENT ANALYSIS
a, DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. cosati Field/Group
Pollution
Refrigerants
Ozone
Fluorohydrocarbons
Stratosphere
Pollution Control
Stationary Sources
Stratospheric Ozone
13 B
13 A
07B
07C
04A
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
88
20. SECURITY CLASS (This page}
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
Reproduced from aiI
best available copyr*
ii
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FOREWORD
The U. S. Environmental Protection Agency is charged by Congress with pro-
tecting the Nation's land, air, and water resources. Under a mandate of national
environmental laws, the Agency strives to formulate and implement actions lead-
ing to a compatible balance between human activities and the ability of natural
systems to support and nurture life. To meet this mandate, EPA's research
program is providing data and technical support for solving environmental pro-
blems today and building a science knowledge base necessary to manage our eco-
logical resources wisely, understand how pollutants affect our health, and pre-
vent or reduce environmental risks in the future.
The National Risk Management Research Laboratory is the Agency's center for
investigation of technological and management approaches for reducing risks
from threats to human health and the environment. The focus of the Laboratory's
research program is on methods for the prevention and control of pollution to air,
land, water, and subsurface resources; protection of water quality in public water
systems; remediation of contaminated sites and-groundwater; and prevention and
control of indoor air pollution. The goal of this research effort Is to catalyze
development and implementation of innovative, cost-effective environmental
technologies; develop scientific and engineering information needed by EPA to
support regulatory and policy decisions; and provide technical support and infor-
mation transfer to ensure effective implementation of environmental regulations
and strategies.
This publication has been produced as part of the Laboratory's strategic long-
term research plan. It is published and made available by EPA's Office of Re-
search and Development to assist the user community and to link researchers
with their clients.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
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ABSTRACT
Hydrofluorocarbons (HFCs) form a class of chemicals having the potential to replace
stratospheric ozone depleting substances such as chlorofluorocarbons (CFCs) and
hydrochlorofluorocarbons (HCFCs). This report gives results of a preliminary evaluation of a new
HFC (HFC-236ea or 1,1,1,2,3,3-hexafluoropropane) as a possible alternative for CFC-114 (1,2-
dichloro-1,1,2,2-tetrafluoroethane) refrigerant in chillers and high temperature industrial heat pumps.
Evaluation tests included an examination of the flammability, stability, thermophysical properties,
lubricant/IIFC-236ea characteristics, materials compatibility, inhalation toxicity, and refrigeration
performance. HFC-23fiea was found to be an excellent candidate to replace CFC-114 in chillers and
high temperature heat pumps.
iv
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TABLE OF CONTENTS
Page
ABSTRACT., iv
FIGURES VI
TABLES viii
LIST OF SCIENTIFIC SYMBOLS AND ABBREVIATIONS ix
ACKNOWLEDGMENTS x
1. INTRODUCTION 1
2. SUMMARY AND CONCLUSIONS 6
3. THERMOPHYSJCAL AND APPLICATION PROPERTIES OF HFC-236ea 10
SYNTHESIS OF HFC-236ea , 10
THERMOPHY SICAL PROPERTIES 10
ATMOSPHERIC LIFETIME 21
INHALATION TOXICITY 22
FLAMMABILITY 29
HFC-236ea/LUBRICANT CHARACTERISTICS 30
HEAT TRANSFER CHARACTERISTICS 47
STABILITY AND MATERIALS COMPATIBILITY 51
4. REFRIGERANT PERFORMANCE 61
THEORETICAL PERFORMANCE EVALUATION 62
CENTRIFUGAL COMPRESSOR EVALUATION 69
CONCLUSIONS 75
5. REFERENCES 76
v
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FIGURES
No. Page
Figure 1, Fourier-transform infrared spectrum of HFC-236ea 17
Figure 2. Gas chromatogram/mass spectrum of HFC-236ea 18
Figure 3. Solubility of HFC~236ea in POE lubricant 36
Figure 4. Solubility of CFC-114 in mineral oil (York C) 37
Figure 5. Absolute viscosity of mixtures of HFC-236ea (R-236ea) and POE lubricant 38
Figure 6. Absolute viscosity of mixtures of CFC-114 (R-114) and mineral oil (York C) 39
Figure 7. Kinematic viscosity of mixtures of HFC-236ea (R-236ea) and POE lubricant 40
Figure 8. Kinematic viscosity of CFC-114 (R-l 14) and mineral oil (York C) 41
Figure 9. Density of mixtures of HFC-236ea (R-236ca) and POE lubricant 42
Figure 10. Density of mixtures of CFC-114 (R-l 14) and mineral oil (York C) 43
Figure 11. Volume change of polymers in HFC-236ea 56
Figure 12. Weight change of polymers in HFC-236ea 57
Figure 13. Linear swell of polymers in HFC-236ea 58
Figure 14. Hardness change of polymers in HFC-236ea 59
Figure 15. Cycle efficiency with throttling and superheating/dry compression at Tc - 4°C for
CFC-114 alternatives 64
Figure 16. Volumetric capacity cycle with throttling and superheating/dry compression
at Tc = 4°C for CFC-114 alternatives 65
Figure 17. Theoretical volumetric capacity ratio of HFC-236ea relative to CFC-114 67
Figure 18. Theoretical COP ratio of HFC-236ea relative to CFC-114 68
Figure 19. Experimental capacity ratio of HFC-236ea relative to CFC-114 71
Figure 20. Experimental COP ratio of HFC-236ea relative to CFC-114 72
Fipre 21, Compressor volumetric efficiency ratio ofHFC-236ea relative to CFC-114 73
vi
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22, Compressor isentropic energy efficiency for HFC-236ea relative to CFC-114 .
vii
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TABLES
No. Page
Table 1. Chemical codes, formulas, and boiling points of the 37 new chemicals synthesized 3
Table 2. Chemicals selected for further characterization 4
Table 3. Thermophysical properties of liquid and vapor HFC-236ea 19
Table 4. Summary of miscibility data for HFC-236ea in various lubricants 32
Table 5. Coefficients to the correlating equations for HFC-236ea/IS068 pentaerythritol
ester mixed-acid mixtures 34
Table 6. Coefficients to the correlating equations for CFC-114/IS068 naphthenic
mineral oil mixtures 35
Table 7. HFC-236ea wear tests results (unit is teeth of wear) 46
Table 8. Extreme pressure (step test) results (lb) 46
Table 9. Compatibility test matrix......... 52
Table 10. Tested elastomers and plastics 54
Table 11. Desiccant results with HFC-236ea 60
Table 12. Properties of CFC-114 and alternatives 62
Table 13. Centrifugal compressor characteristics at 4°C evaporating and 40°C
condensing temperatures 69
viii
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LIST OF SCIENTIFIC SYMBOLS AND ABBREVIATIONS
cP
centipoise
cSt
eentistokes
Cp
ideal gas heat capacity at constant pressure
Cv
ideal gas heat capacity at constant volume
COP
coefficient of performance
fpi
fins per inch
LOAEL
lowest observable adverse effect level
Ma2
Mach number
N
compressor speed (revolutions per minute)
NOAEL no observable adverse effect level
pe
evaporating pressure
Pc
condensing pressure
ppm
parts per million
Pc
critical pressure
P a
vapor pressure
Qk
compressor refrigerating capacity
R
universal gas constant
RMS
root mean square
rpm
revolutions per minute
SUS
Saybolt Universal Seconds viscosity
Tc
condensing temperature
Tc
critical temperature
Tb
boiling point
u2
compressor impeller tip speed
vs
volumetric flow rate at compressor suction
vd
volumetric flow rate at compressor discharge
Pc
critical density
PL
saturated liquid density
pv
saturated vapor density
ix
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ACKNOWLEDGMENTS
Initial synthesis of HFC-236ea and determination of its thennophysical properties were
performed by Darryl D. DesMarteau and Adolph L. Beyerlein of Clemson University with the joint
sponsorship of the U. S. Environmental Protection Agency (EPA Cooperative Agreement CR-
815134) and the Electric Power Research Institute (EPRI). Extended thennophysical property
measurements and determination of the rate constant for reaction of HFC-236ea with hydroxyl
radical were contributed by the National Institute of Standards and Technology (MIST) under EPA
sponsorship (Interagency Agreement DW13935432). Fire extinguishment testing was conducted by
the New Mexico Engineering Research Institute (NMERI) under EPA Cooperative Agreement
CR817774. Krich Ratanaphruks, Michael W. Tufts, Angelita S. Ng, and Richard Snoddv of Acurex
Environmental Corporation performed the flammability, thermal/chemical stability, materials
compatibility, lubricant irascibility, and lubricity evaluations under EPA Contract 68-D0-O141 and
68-D4-0005. Georgi Kazachki, Evren Bayoglu and Rob Delafield of Acurex Environmental
Corporation were responsible for the compressor calorimeter tests under EPA Contract 68-D0-0141
and 68-D4-0GQ5. Iowa State University performed lubricant/HFC-23 6ea solubility, density,
viscosity, and heat transfer measurements under EPA Cooperative Agreement CR820755. Toxicity
tests were supported in part by funding from the Strategic Environmental Research and Development
Program (SERDP) and were conducted by Dupont/Haskeil Laboratory under EPA Contract 68-D2-
0063.
x
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1. INTRODUCTION
Fully halogenated chlorofluorocarbons (CFCs) and their bromine-containing relatives
(halons) are recognized as primary contributors to depletion of the Earth's stratospheric ozone layer.
As early as 1978, the United States, on the basis of what was then largely theoretical evidence for
depletion of stratospheric ozone by CFCs, responded by promulgating restrictions on the use of CFCs
as propellants in aerosol products. At that time, aerosol propellants represented the single largest
commercial use of the CFCs. Only Sweden, Norway, and Canada joined the United States in
enacting measures to reduce CFC emissions at that time.
In the mid-1980's, as scientific evidence confirming stratospheric ozone depletion mounted, the
U. S. Environmental Protection Agency (EPA) began considering additional regulatory restrictions on
the use of CFCs and halons by weighing the environmental benefits against the economic and societal
consequences of such action. In the course of this study, it became apparent that few, if any,
alternative chemicals were readily available or had been proven applicable to the numerous CFC and
halon uses which had grown dramatically in the short time span following the 1978 CFC aerosol ban.
In the spring of 1987, the EPA convened a panel of international experts to assess the
likelihood of finding suitable alternative chemicals. Compounds in which one or more of the chlorine
or bromine atoms of the CFCs and halons were replaced by hydrogen atoms appeared to offer a high
probability of serving as successful alternatives. It was noted that the presence of hydrogen in the
molecules would increase the probability that the molecules would degrade in the lower atmosphere
and be dissipated before reaching the ozone layer. However, it was also noted that replacing halogen
atoms with hydrogen atoms could lead to undesirable flammability, toxicity, and/or reduced efficacy
of the compounds in certain applications. Among the findings of the expert panel was the conclusion
that governments should sponsor research to enhance knowledge of chemical substitutes, particularly
research into those chemicals that were not already under active consideration by chemical companies
(Nelson, 1988).
1
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Shortly after the landmark Montreal Protocol on Substances that Deplete the Ozone Layer
was negotiated in September, 1987 (UNEP, 1987), the EPA's Air and Energy Engineering Research
Laboratory (AEERL) * initiated a search for new chemical alternatives. This effort was undertaken
to try to provide an expanded set of candidate alternatives in the event that the few chemicals which
had then been proposed as alternatives fell short of expectations.
In 1988, AEERL and the Electric Power Research Institute (EPRI) formed a cooperative
project with the chemistry departments of Clemson University and The University of Tennessee to
synthesize a number of partially fluorinated propanes and butanes and fluoroethers which, on the
basis of molecular structure and anticipated boiling points, were thought to be possible CFC or halon
alternatives. These compounds also possessed structural features believed to enhance degradation of
the compounds in the troposphere. Over a three-year period, 37 compounds were prepared of
sufficient stability and in sufficient yield and purity to obtain a limited set of relevant property
measurements. Of the 37 chemicals synthesized, 15 were hydrofluoropropanes and butanes (HFCs),
8 were hydrofluoroethers (HFEs), 5 were fully fluorinated ethers (FEs), and 9 were
hydrochlorotluoropropanes (HCFCs). These compounds and their normal boiling points are listed in
Table 1.
AEERL selected for further study 12 of the 37 synthesized chemicals whose measured boiling
points and critical temperatures most closely matched those of CFCs-11, -12, -114, and -115 or
which might form mixtures having desirable properties. Alternatives for CFC-113, widely used as a
solvent, were not emphasized since a number of chemicals and technologies appeared to already exist
or be emerging to replace this compound. Also, compounds which possessed chlorine (HCFCs) were
ruled out for further evaluation since it was becoming clear that such compounds had non-zero ozone
depletion potentials and would also be subject to future phaseout. Table 2 presents the 12
compounds selected by AEERL for further examination.
* Recently redesignated the Air Pollution Prevention and Control Division of the National Risk
Management Research Laboratory, Research Triangle Park (NRMRL - RTP), NC.
2
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Table 1. Chemical codes, formulas, and boiling points of the 37 new chemicals synthesized.
Chemical Code
Chemical Formula
Th (°C)
HFC-227ca
CF3-CF2-CF2H
-16.3
HFC-227ea
cf3-chf-cf3
-18,3
HFC-236ca
CHF2-CF2-CHF2
JL jL> ¦£-,
12.6
HFC-236cb
CF3-CF2-CFH2
-1.4
HFC-236ea
3-^™ "vt ^2*1
6.5
HFC-236fa
CF3-CH2-CF3
-1.1
HFC-245ca
cf2h-cf2-cfh2
25.0
HFC-245cb
CF3-CF2-CH3
-18.3
HFC-245fa
cf3-ch2-cf2h
15.3
HFC-254cb
cf2h-cf2-ch3
-0.8
HFC-329mccp
CF3-CF2-CF2-CF2H
15,1
HFC-338pccq
CHI'2-CF2-CF2-CH2F
42.5
HFC-338mccq
CF3-CF2-CF2-CFH2 '
27.8
HFC-338meem
CF3-CHF-CHF-CF3
25.4
HFC-347mccs
CF3-CF2-CF2-CH3
15.1
HCFC-225ba
CF3-CFCI-CFHCI
51.9
HGFC-225da
CF3-CHCI-CF2CI
50.8
HCFC-226da
CF3-CHCI-CF3
14,1
HCFC-226ea
CF3-CHF-CF2CI
17.1
HCFC-234da
CF3-CHCI-CFHCI
70.1
HCFC-235ca
CF3-CF2-CH2CI
28.1
HCFC-243da
CF3-CIICI-CH2CI
76.7
HCFC-244ca
cf2h-cf2-ch2ci
54.8
cy-HCFC-326
cy-(CF2)3-CHCl-
38.1
(continued)
3
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Table 1. Continued
Chemical Code
Chemical Formula
Th(°C)
HFE-125
CF3-0-CF2H
-34.6
HFE-134
cf2h-o-cf2h
4.7
HFE-143
cf2h-o-cfh2
29.9d
HFE-143a
CF3-0-CH3
-24.1
HFE-227ca
cf3-o-cf2-cf2h
-3.1
HFE-124B1
CF2H-0-CF2Br
24.5
FE-115B1
CF3-0-CF2Br
-5.4
FE-116
CF3-O-CF3
-58.7
FEE-218
CF3-O-CF2-O-CF3
-9.8
cy-HFE-225
cy-CHF-CF2-0-CF2-
3.4 ¦
cy-HFE-234
cy-CH2-CF2-0-CF2-
21.2
cy-FE-216
cy-CF2-CF2-0-CF2-
-28.2
cv-FEE-216
cy-CF2-0-CF2-0-CF2-
-22.1
Note: Chemical codes for the ether compounds have not been standardized. The listed codes
are AEERL designations, "d" = decomposes.
Table 2. Chemicals selected for further characterization
Alternatives
Chemical
Chemical
Chemical
for:
Code
Formula
Name
CFC-1 l/HCFC-123
HFC-245ca
CF7H-CF7-CFH9
1,1,2,2,3-pentafluoropropane
HFC-245&
CF3-CH2-CF2H
1,1J ,3,3-pentafluoropropane
HFC-338mccq
CF3-CF2-CF2-CFH2
1,1,1,2.2,3,3,4-octafluorobutane
CFC-12
HFC-227ca
CF3-CF7-CF5H
1,1,1.2,2,3,3-heptafiuoropropane
HFC-227ea
CF3-CHF-CF3
1,1,1,2,3,3,3-heptafluoropropane
HFC-245cb
CF3-CF2-CH3
1,1,1,2,2 -pcr.ta fl uoropropai5C
HFE-143a
CF3-O-CH3
1,1,1 -tritluorodimethvi ether
CFC-114
HFC-236cb
CFvCl'VCFH?
1,1,1,2,2,3-hexafluoropropane
HFC-236ea
CF3-CFH-CF2H
1,1,1,2,3,3 -hexafluoropropaae
HFC-236fa
CF3-CII2-CF3
1,1,1,3,3,3-hexafluoropropane
HFC-254eb
CF2H-CF2-CH3
1,1,2,2-tetrafluoropropane
CFC-115
HFE-125
CFvO-CF7H
pentafluorodimethyl ether
4
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Extended evaluation of these 12 candidates was undertaken by AEF.RL with emphasis on
their potential use as refrigerants. Expanded evaluation included determination of atmospheric
lifetimes, inhalation toxicities, chemical stabilities, material compatibilities, vapor thermal
conductivity, refrigerant/lubricant properties, and refrigeration performance.
This report summarizes results obtained for one of the candidates, HFC-236ea (1,1,1,2,3,3-
hexafluoropropane), as a potential alternative refrigerant for CFC-114 in chillers.
5
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2. SUMMARY AND CONCLUSIONS
HFC-236ea contains no chlorine or bromine atoms and therefore cannot contribute to
depletion of stratospheric ozone. Its measured reaction rate with hydroxy 1 radical (the primary
reaction for removal of pollutants from the atmosphere) is 0,66 x 10"14 cm3 molecule"1 sec"1 at 298 K
which translates to an estimated atmospheric lifetime of 10 years.
Extensive toxicity tests were performed for HFC-236ea including acute inhalation, cardiac
sensitization, genetic toxicity, developmental inhalation, and 90-day subchronic inhalation tests.
Acute inhalation toxicity of the chemical in male rats was investigated and found to be very low.
Lethal concentrations in air were not determined since no rats died during or after exposure to 85000
ppm of HFC-236ea for 4 hours.
In the 2-week inhalation study using rats, the only notable compound-related effect was a
diminished response or lack of response to an alerting stimulus during the first week of exposure.
Most of the animals, however, exhibited normal alerting responses (response to sound stimulus during
exposure) during the second week. A 90-day inhalation study with rats exposed to HFC-236ea at
concentrations up to 50000 ppm showed that the compound had no effect on food consumption, food
efficiency, or body weights, produced no ophthaimological aberrations, and did not induce hepatic
peroxisome proliferation. Other than a slight increase in urinary fluoride concentrations in the 50000
ppm group of test animals, there were no effects in clinical pathological parameters attributable to the
HFC-236ea. There was a diminution or absence of an alerting response at concentrations of 20000
and 50000 ppm, but this effect was transient and not apparent 30 to 50 minutes after cessation of
exposure.
No evidence of mutagenic activity was detected in either of two independent tests in E. coli and
salmonella typhimurium mutagenicity trials. Mouse bone marrow micronucleus assay was conducted
to determine if HFC-236ea induces an increase in the frequency of micronucleated polychromatic
6
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erythrocytes. Under the conditions of this study, HFC-236ea was negative; i.e., did not elevate the
level of micronuclei in bone marrow cells. A developmental toxicity study performed on female rats
showed no compound-related effects on any reproductive parameter and no fetal abnormalities.
Cardiac sensitization , an increased propensity to develop irregular heartbeat with exposure to
certain chemicals, is a toxic effect of high-level exposure to many low-molecular weight organic
compounds, including many CFCs and HFCs. In a cardiac sensitization test with male beagle dogs,
two dogs (out of 5) showed cardiac arrythmias and subsequently died during exposure at 100000
ppm HFC-236ea and another dog died (out of 5) during exposure at 50000 ppm. There were no
gross necropsy findings in the dogs that died which could be ascribed to the test chemical. Based on
these results, the cardiac sensitization no-observable-adverse-effects-level (NOAEL) was 25000 ppm
with a lowest-observable-adverse-effect-level (LOAEL) of 35000 ppm.
HFC-236ea was found to be nonflammable at all concentrations in air up to at least 50 "C. It
is likely that the chemical is nonflammable at even higher temperature but tests above 50 °C were not
performed. Extinguishment of an n-hcptanc flame in a laboratory cup-burner was achieved with a
concentration of 6.6 volume percent HFC-236ea in air, indicating that the compound is not only
nonflammable but could also be considered to be an effective fire suppressant.
HFC-236ea was completely miscible in a polyolester (POE) oil over the temperature range of
-40 to 90"C. In contrast, a naphthenic mineral oil and an alkylbenzene oil were found to be
unsuitable as lubricants with HFC-236ea due to immiscibility within this temperature range. A
complete set of solubility, viscosity, and density data covering a wide range of temperatures were
obtained for the I IFC-236ea in the POE oil.
Stability and materials compatibility tests were performed with HFC-236ea in combination
with various metals, elastomers, and desiccants both in the presence and absence of the POE oil.
Fluoropolymers, in particular, exhibited marked absorption of HFC-236ea resulting in excessive
swelling of the test coupons. A butyl nitrile rubber and natural rubber exhibited excessive swelling in
the presence of the POE oil. Chloroprene rubber became brittle and shrank in volume in the presence
7
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of HFC-236ea. There was 110 evidence of degradation of the refrigerant In combination with any of
the test materials with the possible exception of one of the four molecular sieve desiccants tested,
A theoretical thermodynamic analysis was performed comparing the refrigeration performance
of HFC-236ea to CFC-114 in a simple vapor-compression cycle. This analysis showed a close match
(±6 percent) between the specific volumetric refrigerating capacities of the two refrigerants over the
entire range of temperatures (0 to 35°C evaporating and 40 to 107°C condensing temperatures) with
the exception of the 107°C condensing temperature. The exception at 107°C resulted from the
greater proximity of the HFC-236ea critical temperature (141.1°C) than the CFC-114 critical
temperature (147.5°C) to this condensing temperature. In general, the HFC-236ea volumetric
capacity was lower than that of CFC-114 at lower evaporating temperatures. The predicted increase
in the volumetric capacity with increasing evaporating temperature could be related to the slightly
higher boiling point of HFC-236ea compared to CFC-114 (6.57°C vs. 3.61°C, respectively). Up to
80°C the HFC-236ea coefficient of performance (COP) was within ±1 percent of that of CFC-114
and decreased up to 10 percent lower than the COP of CFC-114 at higher temperatures. The primary
factor in lowering the performance of HFC-236ea relative to CFC-114 at the higher temperatures was
the lower critical temperature of HFC-236ea.
Comparative evaluations of HFC-236ea and CFC-114 were conducted in a compressor
calorimeter test rig with a semihermetic compressor. These tests showed that at condensing
temperatures of approximately 40 to 70°C and at evaporating temperatures higher than 20°C the
cooling capacity of HFC-236ea was within 5 percent of CFC-114. At condensing temperatures up to
65°C, the COP of HFC-236ea was within 5 percent of CFC-114 over most of the evaporating
temperatures. At condensing temperatures higher than 65 °C, the COP dropped significantly below
that of CFC-114.
8
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Conclusions
Both theoretical analysis and experimental evaluation in a semihermetic compressor confirmed
that HFC-236ea can he considered as a replacement refrigerant for CFC-114. At the operating
conditions characteristics of typical CFC-114 chillers (2 to 13°C) evaporating and 40 to 50°C
condensing temperatures), the COP of HFC-236ea is very close to that of CFC-114. At the same
conditions, the cooling capacities of HFC-236ea are 20 to 12 percent lower than those of CFC-114.
The evaluations also indicate that HFC-236ea is an acceptable CFC-114 replacement in high
temperature heat pumps (0 to 35°C evaporating and 40 to 110°C condensing temperatures). There is
some decline in performance of HFC-236ea at condensing temperatures higher than 70°C and
evaporation temperatures lower than 20°C.
Evaluation of the properties of HFC-236ea show that it is nonflammable, has very low
toxicity, has zero ozone depletion potential and an atmospheric lifetime sufficiently short (10 years)
to give an acceptable global wanning potential, and is compatible with commercial polyolestcr
lubricants and other engineering materials commonly used in refrigeration equipment.
9
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3, THERMOPHYSICAL AND APPLICATION PROPERTIES OF IIFC-236ea
SYNTHESIS OF HFC-236ea
HFC-236ea was prepared in laboratory quantities (ca. 100 g) by catalytic hydrogenation of
hexafluoropropene (CF,CF=CF2) on palladium/carbon at 25°C according to the generalized reaction
scheme:
H2
(CF3CF=CF2) -> cf3-chf-cf2h
Pd/C
25 °C
Product obtained from this reaction was characterized by gas chromatography (GC), infrared
19 1
(IR) spectrophotometry, mass spectrometry (MS), and F and H nuclear magnetic resonance (NMR)
spectrometry. Purity of the HFC-236ea thus prepared was 99,5 percent This laboratory-scale
synthesis effort and preliminary thermophysica! property measurements were performed by Clemson
University under joint sponsorship of the EPA and EPRI.
Larger (kilogram) quantities of the compound needed for laboratory scale performance,
stability, compatibility and other tests were procured from PGR, Inc. in Gainesville, FL. Individual
lots of the compound delivered to AEERL for testing were subjected upon receipt to GC/MS and
Fourier transform infrared (FTIR) purity assay and found to be 99.9 percent pure. Figures 1 and 2
present FTIR and mass spectra for HFC-236ea, respectively. Quantities of several thousand
kilograms of HFC-236ea required for toxicity tests were supplied by the DuPont company.
THERMOPHYSICAL PROPERTIES
Table 3 gives experimental thermophysical property data for HFC-236ea as determined by the
National Institute of Standards and Technology (NIST). The properties are based on measurements
of the vapor pressure, the density of the compressed liquid, the refractive index of the saturated liquid
and vapor, the critical temperature, and the speed of sound in the vapor phase. From these data, the
ideal-gas-heat-capacity, the saturated liquid densities, the equation of state of the vapor phase, and
10
-------
estimates of the critical pressure and density were deduced. The data determined the coefficients for
a Camahan-Starling-DeSantis (CSD) equation of state.
Sample purity and boiling point
The purity of HFC-236ea sample was verified by gas chromatography. In most cases, aliquots
from the sample were loaded from the sample in the apparatuses without additional purification.
Because the speed of sound is extremely sensitive to the presence of impurities, some of the specd-of-
sound measurements were performed on a small sample that had been purified in a preparative gas
chromatograph. This highly purified sample was 99.99 percent pure. The measured normal boiling
point was 6.50 ± 0.01 °C.
Vapor pressure
Four different ebulliometer apparatuses were used for the measurements of vapor pressures.
Two were comparative apparatuses and two were direct pressure measurement apparatuses. A series
of 156 saturated vapor pressures were collected, 62 pressures from the comparative apparatuses and
90 pressures from the single boiler apparatuses. The comparative glass ebulliometer ranged in a
pressure from 23.7 kPa to 253.8 kPa. The comparative steel apparatus spanned the pressure range of
118 kPa to 1025 kPa which overlaps the range of glass apparatus. The stainless-steel single boiler
apparatus was used between 120 kPa and 1299 kPa and the sapphire apparatus was used from 598
kPa to 1498 kPa. The combined data sets were fitted by the following equation:
In P — Ic [A, t + A2 t15 + A3 t13 + A4r]
Pc T
Ai = -8.5565596 Tc = 412.45 K
A2 = 3.6250584 Pc = 3501.98 kPa
A3 =-5.0448508
A4 = -1.2100293
11
-------
In regression, Tc was fixed at 412,45 K. The equation yields a critical pressure of 3501.98
kPa. Experience in fitting other functional forms to similar data that the uncertainty in Pc is
approximately 0,4 percent or 15 kPa.
Compressed liquid density and saturated liquid density
A commercially manufactured vibrating tube densimeter was used to measure compressed
liquid densities. Compressed-liquid-density measurements were made along isotherms between 243 K
and 372 K at pressures from 0.5 MPa to 6.5 MPa. The densities range from 7.4 moI/L to 10.46
mol/L. The PpT relation for the compressed liquid surface was represented by an equation of the
form:
2 7
P = a, (T)p + I a, (Tip2""1
n®2
The temperature dependence of the coefficients is given by:
b, = 0.16031230264109
b2 = -54960694.515694
b3= 18431125617.2680
b4 = 2112216.98250781
b5 = -122460538187.40
b6 = -59957.234900733
b7 =-4491486.1728306
b8 = 1194.27552020731
b9 - 81605074.7318785
bw = -8.552540210375
a, = RT + big!
T
a2=bj + bj
""pS
a3=b4 + b5
T2 f1
a4=bs + l>7
qp3
as^ bg + bg
12
-------
a^bio + bn bn = -4749.907410069
•j£ ^3
b[2 - 0.0865312283548
3-t~ bn + bn + bj4 bi3 = 9.5720897363277
rjp2 <2^3 rj*4
bi4 = -2141.589582844
The equation yields the pressure in bar (1 bar = 105 Pa.) when the values R = 0.0831445 bar-L/mol-K
and pG = 3.70302 mol/L are used. This is a correlation of the compressed liquid density data only.
The terms in the equation are a subset of the terms in the widely used modified Benedict-Webb-Rubin
(mBWR) equation of state, and can reproduce the measured liquid densities with a standard deviation
of +0.01 percent.
Saturated liquid densities were generated by evaluating the mBWR equation at vapor pressures
determined from the vapor pressure correlation at temperatures where isotherms of compressed liquid
were studied. The extrapolation of the mBWR from the data to the vapor pressure is short; thus, it is
not believed that it contributes a significant uncertainty to the results of the saturated liquid densities.
Speed of sound
The speed of sound was measured in a gaseous HFC-236ea using a cylindrical acoustic
resonator constructed entirely of stainless steel, nickel, and gold. The speed of sound was measured
in the high purity (99.99 percent) sample for temperatures between 267 K and 321 K and in the as-
received (99.93 percent) samples between 321 K and 377 K. The speed of sound in the as-received
samples was corrected for the presence of impurities by a comparison of the measurement in the two
samples at 321 K. From the speed of sound measurements, ideal-gas-heat-capacities and acoustic
virial coefficients were deduced. From the zero pressure limit of the speed of sound of HFC~236ea,
the ideal gas heat capacity C°p was determined with a precision of ±0.1 percent. However, the
13
-------
relative uncertainty C°p was approximately ±0.2 percent because of the unknown impurities in the
HFC-236ea sample. The results for the C°p are represented by;
C°p /J mol4 K'1 = 5.30694 + 0.03973 T - 1.859 x 10"5 T2
The coefficients for the virial equation of state were obtained from fitting the speed of sound
data as a function of temperature and pressure to the virial equation of state. The temperature
dependencies of the second, third, and fourth acoustic virial coefficients were chosen to be those of
square-well intermolecular potentials. The corresponding expressions for second, third, and fourth
density virial coefficients are given by:
B (T) = b0 [1- (X3 -1) A]
where, b0 = 284.46 cm3/mol
1.3458
e = 384.57 K
B (T) = 1 b\ (5 - d A- c2 A2- c3 A3)
ct = Xs- 18X4 + 32X3-15
c2 = 2X6 - 36a4 + 32X3 + 18X2 -16
C3 = 6XS - 18X4+ 18X2- 6
A =6^-1
where bo = 483.09 cm3 mol"1
A = 1.0381
s = 999.31 K
B (T) = b3„ (0.2869 + 1.634A - 23.29A2 + 54.65A3 + 70.76A4 - 168.2A5 - 12.74A6)
14
-------
A = ec1cbT-l
where b0 = 2.706 cm3 mol"1
e = 700.3 K
The imprecision of the speed-of-sound data was ±0.01 percent comparable to the results
obtained for other candidate replacement refrigerants. However, it is difficult to directly translate this
imprecision into either the uncertainties in the value of B (T), C (T) and D (T) deduced from the data
or into the uncertainties in the vapor densities deduced from the data.
CSD Equation of State
Coefficients for the Carnahan-Starling-DeSantis (CSD) equation of state were deduced to
approximately describe the thermodynamic properties of HFC-236ea over the temperature range of
243 K to 373 K. The CSD equation of state is
PV/RT = 1 + y + y - y a
(1-y) RT(V+b)
where y = b/4V
Coefficients a and b for HFC-236ea have the temperature-dependent representation:
a/(kJ m3 kmol"2) = 5611.9106 exp (-2.4948509 x 10"3T - 1.7370031 x lO V)
b/(m3 kmol"1) = 0.19314696 - 1.8123708 x 10^ - 1.3230688 x 10"7T2
Here T = in Kelvin
R = 8.314471 J mol"1 K"1 (universal gas constant)
The parameters for the CSD equation were chosen to approximately reproduce the measured
vapor pressures and the saturated liquid densities as well as the estimates of the saturated vapor
densities. The CSD equation reproduces the saturation properties of HFC-236ea within ±1 percent
throughout the temperature range of 240 to 380 K.
15
-------
It is well known that the CSD does not represent the critical region adequately. From the data
obtained in this work, the critical parameters for HFC-236ea are estimated to be:
Tc - 412.44 + 0.02 K
Pc = 3501 ± 15kPa
pc = 563 ± 3 kg m"3
16
-------
120
loo
8
4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400
Wavenumber (cm-1)
Figure I. Fourier-transform infrared spectrum of HFC-236ea
-------
Abundance
5000000
4500000
4000000
3500000
3000000
2500000
2000000
1500000
1000000
500000
0
m/z—>
12 19
69
82
133
93 101
—|.—r—,
100
113
X
T—I J T
120
151
' I 1
140
Figure 2. Gas
chromatogram/mass spectrum of HFC-236ea
-------
Table 3. Thennophysical properties of liquid and vapor I IFC-236ea
T(°C)
P(kPa)
Density
(lvg/ni3)
Volume
(m3 /ka)
Entropy
(IvJ/lcg K)
Enthalpy
(kJ/kg K)
% .af.
Cv I Cp
(kJ/ka K) I (kl/kg K>
vapor
liquid
vapor
liquid
vapor
liquid
vapor | liquid
vapor
liquid vapor
liquid
-45
7.194
0.5797
1623
1,725
6.2E-04
0.5895
-0.2243
128.7
-56.9
0.6362
0.9586
0.6920
1.043
•40
9,904
0.7821
1610
1.279
6.2E-04
0.5869
-0.2016
132.2
-51.7
0,6464
0.9699
0.7025
1.055
-35
13.42
1.039
1597
0,9620
6.3E-04
0.5851
-0.1791
135.6
-46,4
0.6564
0.9811
0.7130
1.067
-30
17.91
1.362
1584
0.7341
6.3E-04
0.5839
-0.1568
139.1
-41.0
0.6665
0.9921
0.7236
1.079
-25
23.59
1.762
1571
0.5675
6.4E-04
0,5833
-0.1347
142.6
-35,6
0.6765
1.003
0.7342
1.091
-20
30.66
2.252
1558
0.4440
6.4E-04
0,5833
-0.1128
146,1
-30,1
0.6864
1.014
0.7450
1.103
-15
39.37
2.847
1544
0.3513
0,5838
-0,0912
149.7
-24.5
0.6964
1.024
0.7558
1.115
-10
50.00
3.561
1531
0.2808
6.5E-04
0.5847
-0.0697
153.2
-18.9
0.7062
1.035
0.7668
1.127
- 5
62.83
4.413
1517
0.2266
6.6E-04
0.5860
-0.0484
156.8
-13.3
0,7161
1.045
0.7779
1.139
0
78.18
5.419
1503
0.1845
6.7E-04
0.5877
-0.0272
160,4
-7.5
0.7259
1.055
0.7893
1.151
5
96,39
6.601
1488
0.1515
6.7E-04
0.5897
-0.0063
164.0
-1.7
0.7358
1.065
0.8009
1.164
10
117.8
7.980
1474
0.1253
6.8E-04
0.5920
0.0146
167.6
4.1
0.7456
1.075
0.8127
1.176
15
142.9
9.579
1459
0.1044
6.9E-04
0.5945
0.0352
171,2
10.0
0.7554
1.084
0.8249
1.189
20
171.9
11,42
1443
0.0875
6.9E-04
0.5973
0,0557
174,8
16.0
0.7653
1.093
0.8375
1.202
25
205.4
13.54
1428
0.0738
7.0E-04
0.6003
0.0761
178.3
22.1
0.7752
1.102
0.8505
1.215
30
243.7
15.96
1412
0.0625
7.1E-04
0.6034
0.0964
181.9
28.2
0.7851
1.111
0,8641
i ::x
35
287.4
18.72
1395
0.0534
7.2E-04
0.6066
0.1165
185.4
34.4
0.7951
1.120
0.8782
1.242
40
336.8
21,85
1378
0.0458
7.3E-04
0.6100
0.1365
188.9
40.6
0.8052
1.128
0.8931
1.256
45
392.6
25.39
1361
0.0394
7.4E-04
0.6134
0.1564
192.3
46.9
0.8154
1.136
0.9088
1.271
50
455,2
29.38
1343
0.0340
7.4E-04
0.6169
0.1762
195.7
53.3
0.8256
1.144
0.9255
1.286
55
525.2
33.89
1325
0.0295
7.6E-04
0.6204
0.1959
199.1
59,8
0.8360
1.152
0.9433
1.302
60
603.0
38.95
1305
0.0257
7.7E-04
0.6239
0.2155
202.4
66.3
0.8465
1.159
0.9625
1.319
65
689,3
44.63
1286
0.0224
7.8E-04
0.6274
0.2351
205.6
73.0
0.8573
1,166
0.9832
1.337
70
784.6
51.01
1265
0.0196
7.9E-04
0.6308
0.2546
208.8
79.7
0.8682
1.173
1.006
1.357
75
889.5
58.16
1243
0,0172
8.0E-04
0.6342
0.2740
211.9
86.5
0.8793
1.180
1.031
1,378
(continued)
-------
Table 3. Continued
T(°C)
P(bPa)
Dt
Cki
snsity
»/rri3)
Volume
(m3/kg)
Entropy
(kJ/kg K)
Enthalpy
(kJ/teK)
c
(kJ/k
V
eK)
Cp
vapor
liquid
vapor
liquid
vapor
liquid
vapor
liquid
vapor
liquid
vapor
liquid
80
1005
1221
66.18
0.0151
8.2E-04
0.6374
0.2935
214.9
93.4
0.8907
1.186
1.059
1.059
85
1130
1198
75.18
0.0133
8.4E-04
0.6405
0.3129
217.8
100.4
0.9024
1.191
1.090
1.090
90
1268
1173
85.28
0.0117
8.5E-04
0.6435
0.3323
220.5
107.5
0.9144
1.197
1.126
1. 126
95
1417
1147
96.64
0.0104
8.7E-04
0.6462
0.3517
223.2
114.8
0.9269
1.201
1.168
1. 168
100
1579
1120
109.5
0.0091
8.9E-04
0.6488
0.3712
225.7
122.1
0.9397
1.206
1.217
1.217
105
1754
1091
124.0
0.0081
9.2E-04
0.6510
0.3908
228.0
129.7
0.9532
1.209
1.276
1.276
110
1943
1060
140.4
0.0071
9.4E-04
0.6529
0.4106
230.2
137.4
0.9672
1.213
1.349
1.349
115
2146
1026
159.3
0.0063
9.7E-04
0.6543
0.4306
232.1
145.3
0.9820
1.215
1.441
1.441
120
2365
989.5
181.1
0.0055
1.01E-03
0.6552
0.4509
233.7
153.4
0.9977
1.216
1.563
1.563
125
2600
949.4
206.6
0.0048
1.05E-03
0.6554
0.4716
235.0
161.9
1.015
1.217
1.734
1.734
-------
A complete set of thermophysical properties for HFC-236ea is also available from the N1ST
database REFPROP Version 5.0 (N1ST, 1996).
ATMOSPHERIC LIFETIME
Compounds such as HFC-236ea which do not contain chlorine or bromine atoms are not
capable of destroying stratospheric ozone. However, the presence of carbon-fluorine bonds in the
molecule can render the chemical a strong absorber of infrared radiation. Therefore, it is of interest
to ascertain the atmospheric lifetime of the compound to gauge its global warming potential (GWP).
Carbon-hydrogen bonds in the molecule subject the chemical to degradation bv reaction with
atmospheric hydroxyl (OH) radicals. Therefore, atmospheric stability of a chemical containing C-H
bonds is usually determined by measuring the reaction rate of the chemical with OH radical.
Atmospheric lifetimes are then calculated by comparing the measured rate constant with that of
methyl chloroform (9.9 x 1045 cm3 molecule"1 sec4) whose OH atmospheric lifetime (6.6 years) is
independently known.
Kinetic experiments for the HFC-236ea/OH reaction were performed for the EPA by N1ST
using the technique of resonance fluorescence spectrometry. This technique is based on the rate of
disappearance of OH radical in the presence of a great excess of the stable substrate. While the
method has some advantages over other approaches, it is very sensitive to the presence of even trace
amounts of reactive impurities. By this method, the reaction rate constant for abstraction of a
hydrogen atom from HFC-236ea with OH was determined to be 8.51 x 10"15 cm3 molecule"1 sec*1 at
298 K. In 1994, an international panel arrived at a consensus value for the rate constant of
6.6 x 1045 cm3 molecule4 sec4 at 298 K and a corresponding tropospheric lifetime of 10.0 years
(JPL, 1994).
21
-------
INHALATION TOXICITY
With SERDP cofunding from the U. S. Navy, the EPA undertook a rigorous evaluation of the
inhalation toxicity of HFC-236ea. Included in this battery of toxicity tests were a 5-day acute
inhalation test, genetic toxicity screening, cardiac sensitization, 2-week inhalation, a 90-day
subchronic study and developmental toxicity. A brief synopsis of test protocols and results follows.
Acute Inhalation Toxicity of HFC-236ea in Rats
The acute inhalation toxicity of HFC-236ea in male rats was investigated and was found to be
of very low acute toxicity. Lethal concentrations in air were not determined since no rats died during
or after exposure. The highest concentration tested for HFC-236ea was approximately 85000 ppm
for four hours. HFC-236ea caused symptoms of narcosis at concentrations of 24000 ppm or greater.
Rats recovered quickly (within an hour) after the cessation of exposure and no delayed effects were
seen in a 1 to 4-day recovery period.
2-Week Inhalation Toxicity Study with HFC-236ea in Rats
Four groups of 5 male and 5 female Crl: CD®BR rats were exposed by inhalation for six hours
a day, five days a week for two weeks for a total of 10 exposures. Three test groups per sex were
exposed to target concentrations of 5000, 20000, or 50000 ppm of HFC-236ea in air. The control
group was exposed to air only. The rats were weighed prior to exposure each day and were observed
for clinical signs both prior to and following each exposure. The response to an alerting stimulus was
determined during and after exposures. Clinical pathology evaluations were conducted prior to the
aid of the study. Immediately following the last exposure, rats were sacrificed and necropsied. All
rats were examined for gross and microscopic pathological changes, and liver tissue was evaluated
for peroxisomal P-oxidation activity.
The analytically determined mean concentrations ± standard error of the mean (SEM) of HFC-
236ea in the exposure chambers targeted to 5000, 20000, or 50000 ppm were 5000 ± 26.1, 2000 ±
261 and 49700 ± 352 ppm for the 10 exposures.
22
-------
Rats exposed to HFC-236ea had no body weight effects and no abnormal clinical observations.
The one notable compound-related effect was a diminished response or lack of response (narcosis) to
an alerting stimulus during exposure. Although rats in the 50000 ppm group were generally non-
responsive and rats in the 20000 ppm group had a diminished response during the first week of
exposure, most of these rats exhibited normal alerting responses during the second week. All rats
exposed to 5000 ppm behaved normally during exposure and were responsive to a stimulus following
exposure.
There were no compound-related effects noted during clinical pathology evaluations. No
abnormalities were seen during gross pathology examinations or microscopic evaluation of tissues.
The hepatic p-oxidation data indicated that HFC-236ea did not induce hepatic peroxisomes.
However, a slightly statistically significant decrease in hepatic P-oxidation activity occurred in female
rats exposed to 50000 ppm. This decrease was considered compound-related but not biologically
adverse since the change was not accompanied by relevant clinical pathologic, organ weight, or
microscopic changes.
Under the conditions of this study, the no-observable-adverse-effects-level (NOAEL) was 5000
ppm HFC-236ea, based on the lack of response to an alerting stimulus during exposure to
concentrations greater than or equal to 20000 ppm. This effect was completely reversible upon
cessation of exposure.
Mutagenicity Testing of HFC-236ea in the Salmonella tvphimurium and Eschirichia coli Plate
Incorporation Assays
HFC-236ea was evaluated for mutagenicity in Salmonella tvphimurium strains TA100,
TA1535, TA97, and TA98 and in Eschirichia coli WP2uvrA (pKMlOl) with and without an
exogenous metabolic activation system (S9), The maximum concentration tested was an atmosphere
of 100 percent of HFC-236ea. Lower concentrations of 0, 20, 40, 60, 70, 80 percent HFC-236ea in
air were also evaluated. No evidence of mutagenic activity was detected in either assay of the two
23
-------
systems in either of the two independent trials. A testing protocol established by the EPA's Office of
Toxic Substances (EPA, 1985) was followed.
Mouse Bone Marrow Micronucleus Assay of HFC-236ea. hv Inhalation
Mouse bone marrow micronucleus assay by inhalation was conducted to determine if HFC-
236ea induces an increase in the frequency of micronucleated polychromatic erythrocytes. In this
study, groups of male and female Crl:CD®-l (ICR) BR mice were placed in inhalation exposure
chambers and exposed (whole-body) to HFC-236ea at target concentrations of 0, 5000, 25000, and
50000 ppm for six hours/day for two consecutive days. Bone marrow smears were prepared
approximately 24 and 48 hours after the second exposure, and two thousand polychromatic
erythrocytes per animal were evaluated for the presence of micronuclei.
No statistically significant increases in micronucleated polychromatic erythrocytes were
observed in the animals at any HFC-236ea concentration tested. In addition, no significant decreases
in the ratio of young polychromatic erythrocytes to mature normochromatic erythrocytes were
observed. Under the conditions of this study, HFC-236ea did not induce micronuclei in bone marrow
cells.
In-vitro Assay of HFC-236ea for Chromosome Aberrations in Human Lymphocytes
HFC-236ea was evaluated for ability to cause visible damage to the genetic material in human
lymphocytes in-vitro following 3-hr treatments, with and without metabolic activation (S9), Two
independent trials were conducted. In both trials, concentrations of approximately 0,40, 80, and 100
percent HFC-236fa in air were evaluated. No statistically significant increases in the percent of
chromosomally abnormal cells occurred at any HFC-236ea concentration evaluated, and no
concentration-related trends in chromosome aberration induction were observed. HFC-236ea was not
clastogenic (breaking chromosomes) in this assay.
90-Dav Inhalation Toxicity Study with HFC-236ea in Rats
Four groups of 10 male and 10 female Crl:CD®BR rats were exposed by inhalation for six
hours a day, five days a week, over a 14-week period (65 exposures) to concentrations targeted at 0,
24
-------
5000, 20000, and 50000 ppm (one concentration per group). Rats were weighed weekly and were
observed for clinical signs at weighing and following each exposure. Response to an alerting
stimulus was determined during the exposures. Ophthalmologics! examinations were performed prior
to commencement of the study and at the end of the study. Clinical pathology evaluations were
conducted near the midpoint and at the end of the study. The day following the last exposure, the rats
were sacrificed and necropsied. All rats were examined for gross and microscopic pathological
changes and liver tissue was evaluated for peroxisomal p-oxidation activity.
HFC-236ea had no effect on food consumption, food efficiency, or body weights, produced no
ophthaimological aberrations, and did not induce hepatic peroxisome proliferation at any tested
concentration. During exposure, there was a transient diminution or absence of an alerting response
at concentrations of 20000 and 50000 ppm. Although this effect was considered adverse, it was
transient and not apparent 30 to 50 minutes after cessation of exposure.
Other than a slight increase in urinary fluoride concentrations in the 50000 ppm group at the
end of the exposure period, there were no effects in clinical pathological parameters attributable to
the test compound. The increased urinary fluoride was suggestive of possible metabolism of the test
compound and was not considered an adverse effect.
At the end of the 90-day exposure period, male rats exposed to 50000 ppm showed increased
testicular weights, increased testes to brain weight ratios, and dilatation of the seminiferous tubules.
There were no effects on either germ cells or Sertoli cells and the epididymides appeared unaffected
with apparently normal quantities of sperm. No testicular effects were observed in rats exposed at
5000 or 20000 ppm."
Under the conditions of this study, the NOAEL for male and female rats exposed to HFC-
236ea for 90 days was 5000 ppm, based on the reduced or absent response to an alerting stimulus
during exposures at 20000 and 50000 ppm, and the testicular effects observed at 50000 ppm.
25
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Inhalation Developmental Toxicity Study of HFC-236ea in Rats
A study was conducted at 0, 5000, 20000, and 50000 ppm IIFC-236ea in rats. HFC-236ea
was administered by inhalation to 4 groups of 25 Crl:CD®BR female rats on days 7 -16 of gestation
(Days 7 - 16 G) at daily concentrations of 0, 5000, 20000, or 50000 ppm (one concentration per
group). Observations for morbidity and mortality were made daily. Weights of rats and feed
consumed were measured at regular intervals during the study. Response to an alerting stimulus was
determined during exposures.
Results indicated a diminished to absent alerting response at 50000 ppm. The majority of rats
in this group were generally non-responsive. Some of the rats exposed to 20000 ppm also lad absent
or diminished responses. However, the majority of rats in the 20000 ppm chamber appeared to
respond normally. Normal reactions occurred in rats in the 5000 ppm group each day and in rats
from all groups when they were tested 10 to 20 minutes after the generation of test material ceased.
The abnormal alerting responses were reversible, compound-related effects, since they occurred only
during exposures. Under the conditions of this pilot study, maternal toxicity, characterized by
diminished alerting response during exposure was observed at concentrations of 20000 and 50000
ppm. No fetotoxicity was observed at any concentration level.
Based on these results, exposure levels of 0, 5000, 20000, and 50000 ppm HFC-236ea were
chosen for the main developmental study in rats.
All females survived to scheduled sacrifice on Day 22G. Maternal body weight changes were
significantly reduced at 50000 ppm over Days 7 - 9G and when averaged over the entire dosing
period (Days 7 - 16G). No effects on maternal weight changes were seen at 20000 or 5000 ppm.
Absolute maternal body weights, maternal adjusted body weights (final body weight minus the
products of conception), and weight changes calculated using the adjusted body weight were
comparable across all dose groups.
26
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Maternal food consumption was significantly reduced at 50000 ppm over Days 7 - 9, 9 - 11,
11 - 13G, and when averaged over the entire dosing period (Days 7 - 16G). Maternal food
consumption was unaffected at 5000 and 20000 ppm.
There were no compound-related effects on either morning or afternoon clinical observations.
However, while in the inhalation exposure chambers, diminished alerting responses were reported for
some of the rats at concentrations of 20000, arid 50000 ppm. These observations are compound-
related and are considered adverse.
No compound-related effects were detected during postmortem examinations. No compound-
related effects on any reproductive parameter (pregnancy rate, incidence of dams with total
resorptions or that delivered early, mean number of corpora lutea, mean number of implantations,
mean number of live fetuses per litter, and mean sex ratio) were detected.
Fetal findings showed that there were no compound-related effects on the incidence of early,
late, or total resorptions detected. There were no dead fetuses. No compound-related effects on mean
fetal weight were detected. The values for mean fetal weight were comparable across the control and
exposures.
No compound-related effect on the incidence of fetal malformations were detected. However,
there was a statistically significant increase in the incidence of retarded sternebral ossification at
20000 and 50000 ppm. Increases were not dose related in that the finding was more prevalent at
20000 than at 50000 ppm. These statistically significant increases are not believed to be compound-
related but rather the result of a low control group value (8 fetuses from 5 litters). Historically, the
incidence of this finding from control groups has been variable. Further, the incidence of this finding
appears to be increasing with time.
Under the conditions of this study, maternal toxicity was demonstrated at a daily exposure
concentration of 50000 ppm. The maternal NOAEL was 5000 ppm. Developmental toxicity was not
detected at any exposure level. The developmental NOAEL was 50000 ppm. Thus, HFC-236ea is
not uniquely toxic to the rat conceptus.
-------
Acute Cardiac Sensitization Study of HFC-236ea in Does hv Tnhalatinn
The cardiac sensitization potential of HFC-236ea was evaluated in beagle dogs. Each animal
was exposed individually using a nose-only exposure apparatus. There was one group of eight beagle
males. The first epinephrine dose (appropriate dose level selected during prestudy) was administered
following two minutes of exposure to air (Minute 2). Five minutes later (Minute 7), exposure to the
gas was initiated. The challenge epinephrine dose was administered following five minutes of
exposure to HFC-236ea (Minute 12). Exposure to the test gas was terminated after an additional
(maximum) five minutes (Minute 17). Electrocardiographic data were recorded continuously
throughout the aforementioned procedures (Minutes 0 to 17). Concentrations tested were 12500,
25000, 35000, 50000, and 100000 ppm. At least five dogs were exposed at each concentration.
Detailed physical examinations were performed and body weights were recorded for all dogs on the
day prior to the first day of exposures and on the completion of all exposures. Electrocardiogram
(ECG) recordings taken after the challenge epinephrine dose (during test gas exposure) were
compared to the ECG recordings taken after the first epinephrine dose (during air exposure) and
inspected for responses indicative of cardiac sensitization. Positive responses were considered to
consist primarily of multiple fibrillation or other serious arrhythmic events. Complete necropsies
were performed on animals that died. At study termination, surviving animals were returned to the
stock colony.
Two dogs (out of 5) died during exposure at 100000 ppm HFC-236ea and another dog (out of
5) died during exposure at 50000 ppm HFC-236ea. There were no gross necropsy findings in the
dogs that died which could be ascribed to the test article.
All other animals survived to study termination. No adverse effects on body weights were,
apparent
All animals responded positively for cardiac sensitization at 100000 ppm, the first level tested,
and a decreasing incidence of positive responders was observed at the subsequently tested lower
28
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concentrations. Based on protocol criteria, there were 0/5, 0/5, 1/5, 4/6, and 5/5 positive respondent
at the 15000,25000,35000,50000 and 100000 ppm, respectively.
Based on these results, the no-observable-adverse-effects-level (NOAEL) was 25000 ppm. with
a lowest-observable-adverse-effect-level (LOAEL) of 35000 ppm; an LCJ0 of approximately 40000
ppm was calculated by probit analysis.
FLAMMABILITY
Flammability of HFC-236ea was evaluated by means of the American Society for Testing and
Materials E681-94 standard method for determination of flammability limits (ASTM, 1994). Tests
were conducted at room temperature (300K) and 50"C (323K) using a 5-liter glass test vessel and a
0.1 second AC spark generated by a 15 kV, 30 mA power supply as the ignition source. HFC-
236ea/air mixtures covering the range of 4.8 to 80 percent HFC~236ea by volume and averaging 64
percent relative humidity were found to be nonflammable. This is in agreement with the axiom that
fluorocarbons having a C-F/(C-H + C-C) bond ratio >1 are not flammable. Calculated standard
enthalpies of combustion (298.15 K, 101.3 kPa) for the two possible overall combustion reactions for
HFC-236ea (with all reactants and products in the vapor state) are (Smith and Tufts, 1996):
C3H2F6 + 202 + H20 3C02 + 6HF AH° =-975.1 kJ/mol'1
C3H2F6 + 202 C02 + 2HF + 2COF2 AH° =-815.6 kj/mol-l
Because of its high nonreactivity, HFC-236ea was among several chemicals examined by the
EPA as possible alternatives for ozone depleting fire extinguishing agents such as the halons. This
work was conducted by the New Mexico Engineering Research Institute (NMERI) under EPA
Cooperative Agreement No. CR817774. Laboratory scale suppression of an n-hcptanc flame was
measured using the cup-burner technique (Skaggs et al., 1995). The concentration of HFC-236ea in
air found to just extinguish the flame was 6.6 volume percent This is 2.3 times the concentration of
halon-1301 (CF3Br) needed to extinguish the same flame under the same conditions (2.9 percent).
29
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Taking into account the difference in the liquid densities of HFC-236ea and haIon-1301, the volume
of liquefied HFC-236ea which would have to be available to extinguish a fire is 2.45 times the
volume of liquefied halon-1301. The greater fire extinguishment effectiveness of halon-1301 is due
to the presence of bromine atoms in the molecule. Bromine atoms have been found to be very
effective scavengers of reactive combustion radicals, thereby allowing combustion chain reactions to
be terminated.
HFC-236ea/LUBRICANT CHARACTERISTICS
Development of acceptable alternative refrigerants requires the identification of compatible
lubricants so that refrigeration systems will operate properly. A desirable attribute of a compatible
refrigerant is that it be miseible with the refrigerant over the operating temperatures of the system.
Certain refrigeration systems require a miseible refrigerant/lubricant mixture for compressor
lubrication to prevent accumulation in the evaporator, and for proper lubricant return to the
compressor.
To satisfy these needs, miscibility data were taken in a study performed for the EPA and the
U. S. Navy by Iowa State University. Obtaining miscibility data requires that one visually observe
and record the physical conditions of a refrigerant/lubricant mixture at a specific temperature. The
procedure is repeated for desired ranges of temperatures and refrigerant concentrations. Visual
inspection of the mixture allows for determination of whether or not the mixture showed signs of
cloudiness, floe or precipitate formation, and the formation of a second liquid phase.
In addition to miscibility data, equipment designers also require accurate and extensive data on
the solubility, density, and viscosity of the alternative refrigerant and lubricant mixtures. To support
the design of equipment using HFC-236ea, these data were also taken on lubricant/HFC-236ea
mixtures at various pressures and temperatures.
The scope of work consisted of a miscibility study of various refrigerant/lubricant
concentrations and then a study of solubility and viscosity for the lubricants which demonstrated
-------
miscibility with HFC-236ea. Initial miscibility tests were performed on HFC-236ea/lubricant
mixtures for refrigerant concentrations of 25 and 50 percent fay weight. Additional tests were
performed for refrigerant concentrations of 75 and 95 percent if the initial tests showed complete
miscibility (that is. miscible over the entire test temperature range).
In addition, solubility and viscosity tests were conducted on HFC-236ea/IS068 pentaerythritol
ester (POE) mixed-acid mixtures and CFC-114/IS068 naphthenic mineral oil mixtures, with the
latter used for comparison purposes.
Miscibility of HFC-236ea and Lubricant Mixtures
The miscibility test facility included test cells capable of withstanding high pressures and the
extreme temperatures encountered in the study of refrigerant/lubricant mixtures. The facility was
designed for the purpose of determining the miscibility characteristics of refrigerant/lubricant
mixtures over the temperature range of -50 to 90°C (-58 to 194°F) and for pressures up to 3.5 MPa
(500 psia). Test cells were immersed in one of two constant temperature baths and had glass
viewports so that the miscibility characteristics of the mixture could be observed and recorded.
These tests were performed by keeping the refrigerant/lubricant mixture visible at all times, by
controlling temperatures to ±1°C (±1,8°F), and by agitating the test cells to ensure uniform mixture.
Each refrigerant/lubricant combination was tested for miscibility in I0°C (18°F) increments over the
test range of -40 to 90C° (-40 to 194F0),
When a refrigerant/lubricant mixture is miscible, it appears as one homogeneous transparent
solution. However, when a refrigerant/lubricant mixture is immiscible, either cloudiness (evidence of
particles dispersed throughout the mixture) or two liquid phases can be seen in the cell. The presence
of two liquid phases was the only form of immiscibility encountered in this study. Results of the
measurements of HFC-236ea in each lubricant are presented in Table 4.
31
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Table 4. Summary of miscibility data for HFC-236ea in various lubricants
H.FC-236ea mass
fraction
Observations
ISO68 Naphthenic Mineral Oil
0.25
immiscible from -40 to 90 °C
0,48
immiscible from -40 to 90 °C
IS068 Alkylbenzene Lubricant
0,22
miscible from -40 to 50 °C
immiscible from 50 to 90 °C
0.48
immiscible from -40 to 90 °C
IS068 Pentaerythritol Ester Mixed-Acid
Lubricant (POE)
0.21
miscible from -40 to 90 °C
0.44
miscible from -40 to 90 °C
0.77
miscible from -40 to 90 °C
0.95
miscible from -40 to 90 °C
For every refrigerant/lubricant combination investigated, the data set consists of the
concentration, temperature, and visual characteristics of the contents of the cell. The above table
summarizes the data for each lubricant and HFC-236ea pair. Additional data were taken at 75 and
95 percent refrigerant for the POE lubricant since the 25 and 50 percent mixtures showed complete
miscibility.
Based on the observations, the naphthenic mineral oil and the alkylbenzene lubricant would.be
unsuitable as lubricants in refrigeration and air-conditioning equipment operating with HFC-236ea
because of the lack of miscibility. In contrast, the POE oil is completely miscible at all temperatures
and is recommended for use with HFC-236ea.
Solubility, Density, and Viscosity of Refrigerant/Lubricant Mixtures
The test facility utilized in this study was used for measuring the solubility, viscosity, density,
and miscibility of lubricant/refrigerant mixtures (Zoz and Pate, 1996). The test facility consisted of a
pressure vessel used for preparing the refrigerant/lubricant combinations, a commercially available
viscometer, and windows for observation of the contents. The viscosity measurement range was from
1 to 200 cP, but this range could be easily extended. Precise and convenient charging of mixtures
with refrigerant compositions ranging from 0 to 100 percent was provided. Operating temperature
32
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and pressure ranges for the test facility were 20 to 150°C (70 to 300UF), and 0 to 3.5 MPa (0 to 500
psia), respectively.
Data were collected for HFC-236ea/IS068 POE oil and CFC-114/IS068 naphthenic mineral
oil mixtures. These tests provided solubility, density, and viscosity information for temperatures as
high as 100 °C and for pressures up to 1.4 MPa. From the experimental data equations for viscosity,
pressure (solubility), and density as functions of temperature and concentration were derived. These
equations which are shown below, can be used to reproduce the raw data, graphically plot results,
and interpolate results at intermediate states for which raw data were not directly obtained.
Logtofi* = Ao + A,C + A2T* + A3CT* + A4C2 + A5C2T* + A*CT*2 + A7T*2 + ASC2T*2 (1)
P = B0 + B,C + B2T*+ B3CT* + BX2 + B.sC2T* + B6C r2 + ByT2 + B8C2T*2 (2)
p = D0 + D,C + D,T" + D3CT* + D4C2 + D5C2T* + D6CT*2 + D7T"2 + D8C2T*2 (3)
where
A;, B;, D; = set of coefficients in Eqs. 1-3 (units vary depending on term)
jx* = nondimensional absolute viscosity (viscosity in centipoise divided by one centipoise)
P = the absolute pressure, MPa
p = the density of the liquid, g/mL
C = the mass fraction of refrigerant in the liquid
T* = nondimensional temperature (temperature in K divided by a reference temperature of
The above equations are nonlinear, but are linearized using the following variable substitutions:
After these substitutions, the equations are linear in the eight variables Xi through X8. For
example,
293.15K).
X3 = cr
x4=c2
x, = c
X2 = T'
x5 = c2t
x6 = cr2
x7=t*2 ¦
xs = c2r2
33
-------
P = Bo + BjXi + B2X2 + B3X3 + B4X4 + B5X5 + BsX6 + B7X7 + BgXg
The set of coefficients (A;, Bj, Di> for the equations were obtained by a linear regression
analysis of the data using the commercially available statistical program "Statistical Analysis
System" (SAS, 1993). 8AS provides statistical information about the significance of each of the
coefficients in the above equations and calculates regression coefficients as an indication of the
overall goodness-of-fit of each equation. Coefficients used in the correlating equations for the HFC-
236ea/POE lubricant and for the CFC-114/mincral oil are given in Tables 5 and 6,
It should be noted that when using the correlations in Eeu of the graphs, care must be taken to
avoid extrapolation beyond the limits of applicability. These limits of applicability are given along
with the coefficients in Table 5 and Table 6.
Table 5. Coefficients to the correlating equations for HFC-236ea/IS068 pentaerythritol ester
mixed-acid mixtures
Term
Viscosity
Pressure
Density
Intercept
Ao= 17.6225
Bo = 0.0
Do = 1.1766
C
At = -19.7445
Bt= 27.6499
Di = 0.36572
r
A2 = -23.4289
O
O
II
PQ
D2-- 0.20101
CT*
Aj= 26.9284
B3 = -56.6801
Jh= 0.0
C2
£
11
O
O
B4 = - 9.6043
d4= 0.0
c2r
>
II
0
0
B5= 20.2567
Lh= 0.64247
CT2 •
Ae = -10.0516
B« = 29.4792
D« = - 0.04168
T*2
Ai= 8,0674
B?= 0.0
D7= 0.0
C2T"2
A8= 0.13??
Bg=-10.9266
D« = - 0.51191
Note: Limits of applicability of the correlating equations (Eqs. 1 through 3) are:
Concentration (C): 0 to 50 percent refrigerant
Temperature: 20 to 100 °C (68 to 212 °F)
Pressure: 0 to 1.4 MPa (0 to 200 psia)
34
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Table 6, Coefficients to the correlating equations for CFC-114/IS068 naphthcnic mineral oil
mixtures
Term
Viscosity
Pressure
Density
Intercept
An = 22.6390
DO
i!
o
o
Do = 1.0900
C
A, = -51.3833
B] = 13.0045
I); = 0.36493
T*
A, = -32.0444
B2 = 0.0
D2 = - 0.17660
CT*
Aj = 77.4782
Bj = -31.1820
O
o
li
Q
c2
A, = 42.6780
B4 = 8.5821
D4 = - 2.0077
C"T"
As= -6(5.8882
B5 = - 9.4839
Ds = 4.4864
CT2
A0 = -30.2322
B„ = 19.0693
D6 = 0.0
t-2
At = 11.6399
Bi = 0.0
D7= 0.0
c2t*2
Ag= 26.5244
Bs= 0.0
Dg = - 2.3293
Figures 3 through 10 provide plots of solubility, viscosity, kinematic viscosity, and density as a
function of temperature for both the HFC-236ea/POE lubricant and for the CFC-114/mincral oil.
[Note: In the graphs, "R" stands for "refrigerant" 236ea or 114.]
35
-------
0.0 0.1 0.2 0.3 0.4
refrigerant concentration, mass fraction
Figure 3. Solubility of HFC-236ea in POE lubricant
-------
1.0
Ui
0.8
«
CL
uT
ce
D
V)
I
0,8
£
aoc
70 C
60 C
fiOC
40 C
30 C
0.2
0.0 cj.
0.0
t > i
< tit ¦ ¦ t
-J 1 L.
0.1 02 0.3 * 0.4
REFRIGERANT CONCENTRATION, MASS FRACTION
0.5
Figure 4. Solubility of CFC-114 in mineral oil (York C)
-------
¦i
10
to1
o
10
CO
70
00
30
100
Temperature, °C
Figure 5. Absolute viscosity of mixtures of HFC-236ea (R-236ea) and POE lubricant
-------
2
10
i
0
30
40
50
60
70
. BO
100
Temperature, °C
Figure 6. Absolute viscosity of mixtures of CFC-114 (R-l 14) and mineral oil (York €)
-------
60
70
00
30
eo
100
Temperature, °C
Figure 7. Kinematic viscosity of mixtures ofHFC-236ca (R-236ea) and POE lubricant
-------
z
10
I
10
UK n i 14
30
60
100
Temperature, °C
Figure 8. Kinematic viscosity ofCFC-114 (R-l 14) and mineral oil (York C)
-------
1.15
«y. n?3s»«
30% H 218m
SOftiltKM
iokiizmm
W. 11536..
0.90 I ¦ i—i—i—I—¦—l—i—i—I—¦—«—s—i—I—i—i l—i—l I I I i
30 40 50 60 70 80 80 100
Temperature, °C
Figure 9. Density of mixtures of HFC-236ea (R-236ea) and POE lubricant
-------
1,05
1.00
FJ
<
Ch
£
OT
s
Q 0,95
0.00
0J5
30
40
SO
60
70
80
80
too
Temperature, °C
Figure 10, Density of mixtures of CFC-114 (R-l 14) and mineral oil (York C)
-------
HFC-236ea/POE Lubricity
A wear test based on the ASTM Method D2670-88, "Standard Test Method for Measuring
Wear Properties of Fluid Lubricants (Falex Pin and Yee Block Method)" was carried out (ASTM,
1988). This ASTM method was modified to accommodate testing the lubricant/refrigerant
combinations by substituting the standard oil test cup with a glass cup with an internal glass frit in
the bottom and a side arm. The lubricant was added to this glass cup and the test gas added through
the side arm. The test gas would then bubble up through the oil.
The Falex test machine rotates a metal journal between two metal stationary vee blocks
immersed in an oil bath. Load is applied to the system through lever arms (load arms) to the vee
blocks. An analog, dial-type gauge measures the applied load and an electronic load cell measures
the torque transferred by the friction between the rotating pin and the vee blocks. The load is
generated by a screw-drive clamp mounted across the ends of the lead arms. The amount of wear of
the test pieces is measured as the amount of rotation of a toothed wheel attached to the screw-drive
(200 teeth equals one full rotation).
The wear test uses a five minute break-in period at fixed load. Following the break-in period,
a wear test consists of operating the machine at a fixed load for 15 minutes; the total number of teeth
passing a reference point is reported as the result.
The extreme pressure test used the step test procedure described in ASTM D3233-92,
"Standard Test Method for Measurement of Extreme Pressure Properties of Fluid Lubricants (Falex
Pin and Vee Block Method)"(ASTM, 1992). The pressure test also involves a five minute break-in
period at fixed load. Following the break-in period, the load is increased in 250-pound increments
and maintained for 1 minute at each increment. The extreme pressure test is complete when a brass
shear pin breaks (at approximately 100 in-lbs torque) or when the maximum system load (2885
pounds) is reached without failure of the shear pin. The load at failure (or maximum load) is
reported as the result. Results of the step tests are in "pounds" of load applied to the test pieces at
44
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failure. In this case, a larger number indicates a better performance. A value "2885+" indicates that
the test piece did not seize or break after the completion of the maximum load of the test m^rnine
A combined test matrix was developed using a mineral oil-sulfur mixture (ASTM D 2670-88
Blend B) and argon gas as controls. The order of the tests was randomized to remove possible bias
as a result of test order. Argon was chosen as an inert control gas since nitrogen might react with the
hot test pieces during test. A gas flow rate of 0.1 liter per minute was maintained in all tests. The
cylinder, valve, flow meter, and lines were kept at ambient temperature. The mass low rale for
HFC-236ea was approximately 1 gram per minute.
Results for the wear tests given in Table 7 show the number of teeth advanced on the screw
drive (higher number equals more wear) or that the test pieces seized during the test Using the POE
oil in the absence of argon or HFC-236ea resulted in seizure of the test pieces in 6 of the 8 trials
while the other 2 trials gave less wear than did operation with Blend B. It was observed that fine
metal particulate generated during the wear tests remained suspended in the Blend B oil but
agglomerated in the POE oil and often accumulated in the test piece interfaces causing seizure.
Agglomeration of the metal particulate in the POE oil may be related to an additive in the oil which
was not present in Blend B. Overall, addition of argon to the POE oil gave significant improvement
in wear resistance, and addition of HFC-236ea to the POE oil gave slightly greater improvement It
is postulated thai this decrease in the amount of wear upon adding argon or HFC-236ea may be due
to a reduction in the temperature of the oil caused by the flow of gas through the oil and/or to gas
bubbles flushing metal particles from the joumal/vee-block interfaces. For some tests, it was
observed that all of the wear occurred in the last 5 minutes of the test when the oil had reached a
temperature of 90 to 100°C,
45
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Table 7. HFC-236ea wear tests results (unit is teeth of wear)
Blend B
POE lubricant
w/o Argon
w/Argon
w/o Argon
w/Argon
w/HFC-236ea
114
162
seized
56
32
117
140
seized
135
35
109
165
seized
90
0
111
seized
45
128
seized
43
131
seized
seized
117
41
106
118
73
Results for the extreme pressure or step tests are given in Table 8. Results are tabulated as
either the load (in pounds) at which the rotating journal seized or as "2885+" to indicate that the
lubricant was tested to the limits of the machine without failing. Again, the standard Blend B oil
outperformed the POE oil in all tests except for those in which HFC-236ea was added to the POE oil.
Addition of argon slightly enhanced the lubricity of both the Blend B and POE oils in the step test,
again possibly due to a cooling effect. Addition of HFC-236ea to the POE oil improved its
performance on average by a factor of approximately 2.5 in the step test.
In general, it was found that the presence of HFC-236ea in the POE oil significantly improved
the lubricity of the oil as measured in the ASTM wear and extreme pressure tests.
Table 8. Extreme pressure (step test) results (lb)
Blend B
POE lubricant
w/o Argon
w/Argon
w/o Argon
w/Argon
w/HFC-236ea
2600
2SS5+
765
1100
2885+
2600
2885
930
1100
930
2450
2885+
765
1100
2885+
2450
765
2885+
2885+
930
765
2885+
1 100
765
2600
2600
46
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HEAT TRANSFER CHARACTERISTICS
A stud}' was performed by Iowa State University for the EPA and the U. S. Navy to compare
HFC-236ea and CFC-114 refrigerant heat transfer characteristics in condensation and pool boiling
with various tube surfaces (Huebsch and Pate, 1996), Horizontal, integral finned tubes have been in
service for over 40 years, and these tubes are widely used because of their higher performance
compared to plain tubes. The scope of this study was to:
• Modify an existing spray evaporation test facility' so that it could perform condensation
and pool boiling tests using a two-pass single tube set-up
• Test refrigerant HFC-236ea and compare its performance to CFC-114 as the reference
fluid
• Evaluate plain. 26 and 40 fpi (fins per inch) tubes for condensation
• Evaluate plain. 26 and 40 fpi tubes for flooded evaporation
• Investigate oil effects in pool boiling on the shell side heat transfer performance by varying
the oil concentration from 0 to 3 percent
• Compare results to published correlations for condensation and pool boiling
The test facility used in this study was initially used for spray evaporation testing, however, it
was redesigned and modified for use with condensation, pool boiling, or spray evaporation testing.
During condensation, the rig was capable of producing saturated or superheated vapor. During pool
boiling or spray evaporation, the test facility was capable of testing pure refrigerants or
refrigerant/lubricant mixtures- During some boiling experiments, lubricant was mixed with the
refrigerant. The mineral oil used with CFC-114 was York "C" with a viscosity of 315 SUS (68 cSt)
at 40°C. A polyolester (POE) lubricant with a viscosity of 340 SUS was used with HFC-236ea. The
two lubricants were miscible with the corresponding refrigerants over the entire range of conditions
tested in this research.
The main objective of this study was to conduct an experimental heat transfer evaluation
comparing the performance of CFC-114 and HFC-236ea in the condensation and pool boiling
-------
environments. Condensation testing included an investigation of saturated and superheated vapor on
fin tube surfaces. Pool boiling research involved nucleate boiling of pure refrigerant and
refrigerant/lubricant mixtures on fin tube surfaces.
All of the tubes used in this study had a nominal outside diameter of 19.2 mm (0.75 in.) and a
length of 838.2 mm (33 in.). Shell side heal transfer coefficients presented below were based on the
outside surface area of a corresponding smooth tube, with the outer diameter measured over the
surface enhancement. Therefore, the calculated heat transfer coefficient takes into account the area
enhancement, fin efficiency, and surface enhancement of the tubes tested.
Refrigerants CFC-114 and HFC-236ea were evaluated in the condensation environment on the
plain, 26 and 40 fpi tube surfaces. In addition, the effects on the heat transfer performance from
condensing superheated vapor were investigated with CFC-114, During saturated vapor testing,
temperature was held constant at 40°C. For condensation of superheated vapor, the saturation
temperature (T^) was also 40°C, but the incoming vapor was 3 to 5C° higher than T^.
For condensation of both refrigerants, the integral fin tubes yielded heat transfer coefficients
approximately four times those produced from the plain tube. In addition, all combinations of the
finned tubes and refrigerants produced similar shell side condensation coefficients in the heat flux
range tested, with a maximum deviation of 9 percent.
A correlation comparison made with the plain tube results showed excellent agreement with the
Nusselt correlation. CFC-114 and HFC-236ea data were predicted within 3 and 10 percent,
respectively. A Beatty and Katz correlation was able to predict the 26 fpi tube data for both
refrigerants with a maximum deviation of 15 percent. Predictions for the 40 fpi tube resulted in
larger deviations. The Beatty and Katz correlation predicted the 40 fpi tube data within 18 and 21
percent for CFC-114 andHFC-236ea, respectively.
The two refrigerants produced similar performance characteristics in condensing vapor on
integral fin tubes, so the transition to HFC-236ea should be accomplished without major
48
-------
modifications to existing condensers. Overall, the above information shows that HFC-236ea is a
valid replacement for CFC-114 in the condensation environment.
Results also showed that the condensation of superheated vapor had negligible effects on the
shell side heat transfer coefficient with respect to saturated vapor results. Superheated vapor data for
the 26 and 40 fpi tubes were within 5 and 3 percent, respectively, of the saturated vapor results for
the same tube surface.
CFC-114 and HFC-236ea were evaluated in the pool boiling environment on plain, 26, and 40
fpi tube surfaces. In addition, this study investigated the effects of small concentrations of oil on heat
transfer performance. The concentrations tested were 1 and 3 percent mass using a 68 cSt mineral oil
for CFC-114 and a 340 SUS POE oil for HFC-236ea. During pool boiling, data were taken at a
constant saturation temperature of 2°C for both pure refrigerant and refrigerant/lubricant mixtures.
The 26 fpi tube produced boiling coefficients for CFC-114 that were 12 and 30 percent higher than
for the 40 fpi tube, and the plain tube, respectively. For HFC-236ea, the 26 fpi tube outperformed
the 40 fpi tube by 18 percent and the plain tube by 14 percent. In addition, HFC-236ea produced
higher boiling coefficients than CFC-114 for all tubes tested. The maximum increase in boiling
coefficient with HFC-236ea relative to CFC-114 was 39 percent for the 26 fpi tube and 34 percent
for the 40 fpi tube.
Lubricant addition to CFC-114 produced enhancements in the boiling coefficients for the three
tubes tested with oil. Maximum enhancement occurred at a 3 percent oil concentration for each tube.
Addition of oil at a 1 percent concentration improved the heat transfer coefficients for the 26 fpi tube
by 27 percent, while the 3 percent oil concentration only showed minor improvement over the 1
percent results. The 40 fpi tube produced similar trends to the 26 fpi tube at both oil concentrations.
Pool boiling of HFC-236ea with POE lubricant produced consistent decreases in the heat
transfer performance at both concentrations. The 26 fpi tube showed a decrease in performance of 6
49
-------
and 17 percent relative to results with HFC-236ea alone at oil concentrations of 1 and 3 percent,
respectively. The 40 fpi tube had only a 10 percent decrease in the boiling coefficients at a 3 percent
concentration with respect to the pure refrigerant. At an oil concentration of 1 percent, the 40 fpi
tube showed negligible oil effects in the low heat flux range. It is evident that the heat transfer
enhancement gained front the turbulent mixing within the foaming layer is dependent upon the type of
oil. The mineral oil used with CFC-114 showed a general improvement in the heat transfer
performance, while the POE lubricant consistently degraded the heat transfer performance of HFC-
236ea.
It is also worth noting that, even though the pure HFC-236ea results are higher than those for
CFC-114, the oil effects on both refrigerants cause the boiling coefficients to be within 12 percent of
each other for the 26 fpi tube at an oil concentration of 3 percent Therefore, the addition of oil
decreased the deviation in the heat transfer coefficients between the two refrigerants.
In addition to the heat transfer performed with conventional plain and integral finned tubes, the
heat transfer performance of HFC-236ea was examined for high performance enhanced tubes during
condensation, pool boiling, and spray evaporation. Shell side heat transfer coefficient data were
obtained for condensation on a Turbo CII tube, pool boiling on Turbo B and Turbo BII tubes, and
spray evaporation on Turbo B and Turbo CII tubes. These tubes each had a nominal outer diameter
of 19.1 mm (0.75 in.).
For condensation of HFC-236ea at 40°C , the high performance Turbo CII tube gave heat
transfer coefficients approximately twice those for either integral finned tubes and 5 to 10 times
higher than those for the plain tube. For pool boiling of HFC-236ea at 2°C, the Turbo BII tube
outperformed all other tube types tested and provided approximately 1.2 to 1.7 times higher heat
transfer coefficients than the Turbo B tube. The Turbo B tube yielded approximately 1.1 to 1.3 times
higher heat transfer coefficients than the 26 fpi tube, 1.4 to 1.5 times higher than the 40 fpi tube, and
1.8 to 2.2 times higher than the plain tube. The heat transfer coefficient in pool boiling increased
with heat flux.
-------
For spray heat evaporation of HFC-236ea at 2DC, the Turbo B tube outperformed both the
Turbo CII and the 40 fpi tube (heat coefficients ca. 1.1 to 1.2 times higher than the Turbo CII and
1.6 to 1.8 times higher than the 40 fpi tube). The heat transfer coefficient in spray evaporation
increased at low heat fluxes but then decreased with increasing heat flux. A comparison of heat
transfer performance of spray evaporation with pool boiling showed that the heat transfer superiority
of HFC-236ea for spray evaporation over pool boiling exists only at low heat loads.
A review of the above information shows that HFC-236ea is a valid replacement for CFC-114
in the nucleate boiling environment. The boiling performance of HFC-236ea was either equal to or
greater than the performance of CFC-114 for all testing parameters. With the similar boiling
characteristics, transition to HFC-236ea in a flooded evaporator would be relatively simple.
STABILITY AND MATERIALS COMPATIBILITY
Thermal and hydrolytic stability of HFC-236ea in the presence of metal catalysts were
evaluated by placing the chemical in evacuated sealed glass tubes in contact with copper, steel,
aluminum, brass, bronze, 304 stainless steel, black annealed steel, and galvanized steel coupons. All
tubes were then heated at 175°C for 14 days in accordance with the methods described in
ANSI/ASHRAE Standard 97-1989 (American Society of Heating, Refrigerating and Air-
Condi tioning Engineers) (ASHRAE, 1989). These tests were repeated with IS068 POE lubricant
added, and with added moisture.
At the end of the 14-day aging period, the contents of the tubes were visually inspected and the
vapor and liquid phases analyzed by a combination of gas chromatography, mass spectroscopy, and
Fourier transform IR spectrometry. For all samples, there was no change in the HFC-236ea (vapor)
following the aging process. No evidence of degradation of either lubricant or refrigerant was
observed in the liquid phases of any sample.
Another matrix of sealed tube samples was prepared combining HFC-236ea with various
desiccants, plastics, and elastomers with and without POE lubricant to test for compatibility of the
51
-------
Table 9, Compatibility test matrix
Sample ID
Material(s)
la,b
HFC-236ea/Bima™-N
2 a,b
HFC-236ea/E-70
3 a,b
HFC-236ea/HNBR
4 a,b
HFC-236ea/Hypalon®
5 a,b
HFC-236ea/Kalrez® C
6 a,b
HFC-236ea/Natural rubber
7 a,b
HFC-236ea/NBRS
8 a,b
HFC-236ea/Neoprene 3229
9 a,b
HFC-236ea/S-70
10 a,b
HFC-236ea/Teflon®
11 a,b
HFC-236ea/Geolast®
12 a,b
HFC-236ea/Buna™-N/POE
13 a,b
HF C-236ea/E-70/POE
14 a,b
HFC-236ea/HNBR/POE
15 a,b
HFC-236ea/Hypalon™/POE
16 a,b
HFC-236ea/Kalrez-C®/POE
17 a,b
HFC-236ea/Nataral nibber/POB
18 a,b
HFC-236ea/NBRS/POE
19a,b
HFC-236ea/Neoprene 3229/POE
20 a,b
HFC-236ea/S-70/POE
21 a,b
HFC-236ea/Teflon®/POE
22 a,b
HFC-236ea/Geolast®/POE
(continued)
52
-------
Table 9. Continued
Sample ID
Material(s)
23 a,b
HFC-236ea/Mylar®
24 a,b
HFC-236ea/Nomex®
25 a,b
HFC-236ea/Nylon 6,6
26 a,b
HFC-236ea/Mylar®/POE
27 a,b
HFC-236ea/Nomex®/POE
28 a,b
HFC-236ea/Nylon 6,6/POE
29 a,b
HFC-236ea/Brass, Bronze
3Ga,b
HFC-236ea/Cast iron
31 afi
HFC-236ea/Brass, Bronze/POE
32 a,b
HFC-236ea/Cast iron/POE
33 a,b
HFC-236ea/activated Desiccant H-5
34 a,b
HFC-236ea/activatedDesiccant H-6
35 a,b
HFC-236ea/activated Desiccant H-7
36 a,b
HFC-236ea/activated Desiccant H-9
37 a,b
HFC-236ea/Activated esiccant H-5/POE
38 a,b
HF C-236ca/Acti vatcd desiccant H-6/PQE
39 a,b
HFC-236ea/Activated desiccant H-7/POE
40 a,b
HFC-236ea/Activated desiccant H-9/POE
41 a,b
HFC-236ea/Viton® A
42 a,b
HF C-236 ea/Viton® A/POE
43 a,b
HFC-236ea/unactivated desiccant H-5
44 a,b
HFC-236ea/vmactivated desiccant H-5/POE
53
-------
Table 10. Tested elastomers and plastics
Polymer
Description
Buna™-N
Copolymer of 1,3-butadiene (70 percent) and acrylonitrile (30 percent)
HNBR
Hydrogenated nitrile butyl rubber
Hypalon®
Chlorosulfonated high density polyethylene
Geolast®
Nitrile polypropylene
NBRS or Buna™-S
Copolymer of 1,3-butadiene (70-75 percent) and styrene (25-30
percent)
Neoprene
Polychloroprene
Kalrez®-C
Perfluoropolymer of tetrafluoroethylene and perfluoromethyl vinyl
ether
E-70 or EPDM
Ethylene propylene diene methylene rubber
S-70 or SI
Silicone rubber
Viton®-A
Copolymer of vinylidene fluoride and hexafluoropropvlene
Teflon®
Polymer of tetrafluoroethylene
Nomex®
Polymer of m-phenylenediamine and isophthalic acid chloride
Mylar®
Polyethylene teraphthalate
Nylon 6,6
Polymer of adipic acid and hexamethylenediainine
HFC-236ea with these materials. These samples were aged in an oven at 125°C for 14 days. All
tests were run in duplicate. Table 9 gives the sample matrix for the stability and compatibility tests,
and Table 10 shows the polymers in the study.
Figures 11 through 14 graphically display the results of the changes in volume, weight, linear
swell and hardness, respectively, for the elastomeric materials with HFC-236ea with and without the
lubricant. Values represent averages of the duplicate samples for each material. Some swelling of
elastomeric materials is desired for gaskets and O-rings to form a good seal in equipment. However,
volume increases of greater than 20 percent or linear swell of greater than 5 percent may be
considered excessive and detrimental. Also, any shrinkage of the material is not desired. A change of
hardness of greater than +10 percent may indicate excessive softening or embrittlement and may be
54
-------
considered unacceptable. Depending on where in the equipment the engineering materials are placed,
the O-ring and gasket materials may experience contact primarily with HFC-236ea or with a
combination of HFC-236ea and lubricant. Therefore, a given elastomer or plastic may be suitable
for use in one section of the equipment and not in another.
HFC-236ea was one of four HFC refrigerants examined (HFC-236ea, 236fa, 245ca, and
245fa) for thermal and hydrolytic stability and materials compatibility by the EPA. These tests
showed that across all four HFCs, with and without polyolester (POE) lubricant, Buna™-N, Buna™-
S, Geolast®, Hypalon®, silicone rubber, and EPDM elastomers gave acceptable overall performance.
Fluoropolymers such as Viton®, Kalrez®, and Teflon® were especially susceptible to absorption of
HFCs, including HFC-236ea resulting in unacceptable swelling. Hydrogenated butyl nitrile rubber
and natural rubber showed excessive swelling in the presence of the HFC/lubricant mixtures.
Neoprene was deemed unsuitable due to shrinkage and embrittlement with the HFCs, with and
without the lubricant present
Evidence for degradation of HFC-236ea was sought by comparison of the infrared spectra and
gas chromatograms of the vapor phase from each of the aged samples against the corresponding
spectrum and chromatograms of imaged HFC-236ea. Degradation of the aged lubricant was checked
by infrared spectral comparison with the imaged lubricant. Neither HFC-236ea nor the lubricant
showed any evidence of degradation in the presence of various metals after the two-week heating
period.
Some IR spectral changes were observed in the liquid phase for some of the samples containing
the elastomers/plastics, but these features could not be attributed unambiguously to degradation of
the elastomers/plastics or the lubricant or both. The most likely source of the new IR absorption
features seems to be leaching of some components of the polymeric materials such as fillers,
accelerators, or plasticizers included in the polymer formulations.
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Desiccant compatibility with the refrigerant was checked by fluoride analysis of the condensate
collected by passing steam over a bed of desiccant mixed with vanadium pentoxide (V2O5) in a nickel
tube furnace at 975 °C. Fluoride analysis in desiccants was based on industry procedures (UOP,
1978; Association of Florida Phosphate Chemists, 1991). Four molecular sieve desiccants in the
aluminosilicate family were aged along with HFC-236ea and HFC-236ea/POE mixture. One
desiccant type showed a small amount of fluoride deposition (<4 percent); see Table 11.
Table 11. Desiccant results with HFC-236ea
Desiccant and Refrigerant
Combinations
[— — — 1 j=s=sss=zge
Percent Fluoride
without POE with PuE
HX-51 & HFC-236ea
3.02
2.02
HX-62 & HFC-236ea
0.00
0.00
HX-72 & HFC-236ea
0.00
0.00
HX-92 & HFC-236ea
0.00
0.00
1 pore size = 4 angstrom (0.4 nm)
2 pore size = 3 angstrom (0.3 nm)
60
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4, REFRIGERANT PERFORMANCE
Two major uses of chlorofluorocarbons and their alternatives are in the applications of comfort
air conditioning and refrigeration. Both processes use the phase changes of a refrigerant in a vapor-
compression cycle to extract heat through evaporation from the area to be cooled and reject heat
through condensation to a high temperature sink. Thermodynamic evaluations of refrigerants were
performed for a variety of vapor-compression configurations in order to rank the alternatives with
favorable thermodynamic properties and to tailor the configuration to best match the thermodynamic
properties of the refrigerant.
Thermodynamic evaluations were performed using several in-house computer models. These
models were developed using as a basis the thermodynamic properties as predicted by the Camahan-
Starling-DeSantis (CSD) equation-of-state and the thermodynamic expressions derived from this
equation-of-state (Morrison and McLinden, 1986). The computer models provide an efficient tool to
investigate a variety of refrigerants and refrigerant blends across a range of evaporating and
condensing conditions and within a variety of vapor compression configurations.
CFC-114 has been used as the refrigerant of choice in centrifugal chillers with capacities
ranging from 440 to no more than 1200kW operating on board ships and submarines. The U. S.
Navy has been a major user of this type of equipment to supply comfort air conditioning and critical
cooling needs on board its ships. CFC-114 has also been used as a refrigerant in high temperature
heat pumps employed in waste heat recovery and utilization. Table 12 presents a list of some CFC-
114 alternatives in the order of their normal boiling points along with their critical properties. HFC-
236ea is one of several alternatives with normal boiling points near that of CFC-114.
61
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Table 12, Properties of CFC-114 and alternatives
(Kazaehki and Gage, 1993)
Refrigerant
Name
Chemical
Formula
T
c
(°C)
Pc
(kPa)
(°C)
CFC-114
Dichlorotetrafluoroethane
CC1F2CC1F2
145.7
3248
3.6
HCFC-124
2-cMoro-l ,1,1,2-tetratluoroethane
CF3CFC1H
122.5
3660
-13.2
HC-600a
isobutane
C4H10
135.0
3648
-11.7
HCFC-142b
1 -chloro-1,1 ,-difluoroethane
ccjf2ch3
137.2
4120
-9.2
HFC-236cb
1,1 ^^,3-pentafluoropropane
CF3CF2CFH2
130,2
3118
-1.4
HFC-236fa
1,1,1,3,3,3-hexafluoropropane
cf3ch2cf3
130.7
3177
-1.1
HFC-254cb
1,1,2,2-tetrafluoroprcpane
hcf2cf2ch3
146.2
3753
-0.8
HG-600
n-butane
C4H10
152.0
3797
-0.4
HFE-134
1,1,2,2-tetofluorodimethylether
kcf2ocf2h
147.1
4228
6.3
HFC-236ea
1,1,1,2,3,3-hexafluorop ropane
cf3chfcf2h
141.2
3533
6.6
HFC-236ca
1,1,2,2,3,3-hexaflucropropane
hcf2cf2cf2h
155.2
3405
12.6
THEORETICAL PERFORMANCE EVALUATION
Both theoretical and experimental thermodynamic analyses were carried out by comparing
the performance of HFC-236ea with CFC-114 under shipboard chiller conditions (2 to 13°C
evaporating and 40 to 65°C condensing temperature) and high-temperature heat pump conditions (0
to 35°C evaporating and 40 to 110°C condensing temperatures) [Kazaehki, et al., 1995 and Kazaehki,
et al, 1994], A comparison of important parameters for centrifugal compressors was made for HFC-
236ea and CFC-114 (Kazaehki and Gage, 1993).
A thermodynamic analysis was performed for HFC-236ea along with five other potential
CFC-114 replacements for use in centrifugal chillers. In the thermodynamic analysis, two main
performance criteria were the refrigerating efficiency and the volumetric refrigerating capacity.
These criteria were determined for a vapor-compression cycle with throttling and dry compression.
62
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Evaporating and condensing temperatures selected for centrifugal chiller analysis were 4 and 40°C,
respectively. No subcooling or superheating was considered other than the minimum vapor
superheating necessity to avoid wet compression.
Figure 15 presents the cycle efficiency for these refrigerants as determined by the
thermodynamic analysis. The order of the refrigerants with regard to cycle efficiency follows the
general rule of correlation between cycle efficiency and k (a saturated vapor parameter denoting dry
or wet compression depending on whether k is positive or negative, respectively). HFC-236ea ,
HFC-254cb, and HFC-236ca are seen to have cycle efficiencies within 1 percent of CFC-114.
Figure 16 presents the volumetric refrigerating capacity of the vapor compression cycle with
CFC-114 and the six potential alternative refrigerants, including HFC-236ea. With the exception of
CFC-114 which has an unexpectedly low value, all the refrigerants rank according to their normal
boiling points and critical temperatures. The alternative with the volumetric capacity closest to CFC-
114 is HFC-236ea.
This analysis shows .that when the determining criterion for an optimum CFC-114 alternative
is the closest volumetric capacity to CFC-114 coupled with highest cycle efficiency, the leading
candidate is HFC-236ea. If the determining criterion is highest capacity and highest cycle efficiency,
the leading candidate is HFE-134 (1,1,2,2-tetrafluorodiethyIether).
63
-------
0.9
HFE-134 HFC-254cb HFC-236ea HFG-236ca CFC-114 HFC-236fa HFC-236cb
0 Tc=40-C O Tc=50*C
Figure 15. Cycle efficiency with ihrotlling and supei heating/dry compression at T, = 4°C for CFC-114 alternatives
-------
1,000
900
Os
Ui
JJC
o
m
o.
<3
O
m
E
~
o
>
800
700
600
500
40 0
HFC-236ca HFC-236ea HFE-134 CFC-114 HFC-254cb HFC-23Gla HFC-236cb
Tc=40»C a Tc=S0*C
Figure 16, Volumetric capacity cycle witlv throttling and superheating/dry compression at Te = 4°C for CFC-114 alternatives
-------
The volumetric capacity ratio of HFC-236ea to CFC-114 is presented in Figure 17 for six
condensing temperatures. The results in Figure 17 show a close match (within ±6 percent) between
the specific volumetric refrigerating capacities of HFC-236ea and CFC-114 over the entire range of
temperatures with the exception of the 107.2cC condensing temperature. The lower volumetric
capacity ratio at 107.2°C is caused by the lower critical temperature of HFC-236ea (141.15X)
compared to CFC-114 (145.65°C) and the closeness of this condensing temperature to the critical
point. This closeness also decreases the accuracy of the refrigerant properties and the evaluation
method. In general, the HFC-236ea volumetric capacity is lower than that of CFC-114 at lower
evaporating temperatures. An increase occurs at the higher evaporating temperatures probably
because of the distancing from the normal boiling point which is higher for HFC-236ea (6.57°C) than
for CFC-114 (3.61°C).
The COP ratio of HFC-236ea to CFC-114 is shown in Figure 18. Up to 80°C the HFC-
236ea COP is within ±1 percent of that of CFC-114 and decreases to 10 percent lower than the COP
of CFC-114 at the higher temperatures examined. The lower critical temperature of HFC-236ea
relative to CFC-114 contributes to lower performance of HFC-236ea at the higher temperatures.
66
-------
i.08
Tc=40.6°C —a— Tc=51.7°C
1.04 •
0.9
10
+
15 20
Evaporating temperature, °C
25
30
35
Figure 17. Theoretical volumetric capacity ratio of HFC-236ea relative to CFC-114
-------
0.98 -
0.96
—Tc=40.6°C
U 0.94
• A ¦ Tc=65.6°C —H— Tc=79.4°€
—Tc-93.3°C —Tc-107.2°C
0.9
0.88
5
20
25
30
35
10
0
15
Evaporating temperature, °C
Figure 18. Theoretical COP ratio of HFC-236ea relative to CFC-114
-------
CENTRIFUGAL COMPRESSOR EVALUATION
Most compressors used in air-conditioning chillers are centrifugal compressors. Important
parameters for centrifugal compressors have been evaluated for HFC-236ea and compared to CFC-
114 {KazaehM and Gage 1993). Table 13 presents some of these parameters for a compressor with
an impeller diameter of 0.5 m and a tip width of 0.025 m for these refrigerants. In developing this
table the following values have used for the compressor coefficients: a compressor head coefficient of
0.6, a tip flow coefficient of 0.3, and a compressor volume flow coefficient of 0.053.
Table 13. Centrifugal compressor characteristics at 4°C evaporating and 40°C condensing
temperatures.
(From Kazachki and Gage, 1993.)
Refrigerant
P
e
P
C
Ma2
N
Vs
VD
Qe
fcPa
kPa
m/s
-
RPM
3.
m/s
m Is
kW
HFC-236ea
91.1
335.3
181
1.48
6928
2.39
2.14
1792
CFC-114
102.7
336.3
163
1.41
6214
2.15
1.92
1653
When the determining criteria are similar operating parameters and volumetric efficiency and
high cycle efficiency, HFC-236ea is a leading CFC-114 replacement for shipboard chillers.
Comparative evaluations of CFC-114 and HFC-236ea were conducted in a compressor
calorimeter test rig with a semihermetic compressor (Kazachki et ai, 1994, 1995), The compressor
was designed for use with HFC refrigerants, was lubricated with polyolester oil, and used an air-
cooled 0.56 kW motor. It volumetric flow rate was 1.329 L/s at 1750 RPM. The evaluations were
made over a wide range of evaporating and condensing temperatures representing both shipboard
chiller and high-temperature heat pump conditions. Some limitations on these conditions were
determined by the calorimeter's capacity rather than by the refrigerants' properties or compressor
characteristics. The tests were made according to ASHRAE Standard 23-1993 (ASHRAE, 1993).
69
-------
Experimental cooling capacities axe presented in Figure 19 as the ratio of HFC-236ea to CFC-
114. At 40.6°C condensing temperature and evaporating conditions for chillers, the coaling capacity
of HFC-236ea is within ±6 percent of CFC-114. At higher condensing temperatures, it drops off to
65 percent, although for up to 70°C condensing temperatures and for evaporation temperatures higher
than 20°C it is within 5 percent.
The ratio of experimental HFC-236ea to CFC-114 CQPs is presented in Figure 20. At
condensing temperatures up to 65°C, the HFC«236ea COP is within 5 percent of the CFC-114 COP
over most of the evaporating temperatures. At higher condensing temperatures it drops significantly
below that of CFC-114.
The experimental capacities and efficiencies for HFC-236ea are slightly lower than the
theoretical values. This is due to the measured lower compressor volumetric efficiency (Figure 21)
and lower compressor isentropic efficiency (Figure 22) ratios of HFC-236ea to CFC-114.
70
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1.1
0.9
j? 0.8
0.7
0,6 - -
—H—Tc=51.7°C
—Tc=40.6°C
•M—Tc=79.4°C
*—Tc="93.30C
—Tc=»107,2°C
0.5
0 5 10 15 20 25 30 35
Evaporating temperature, °C
Figure 19. Experimental capacity ratio of IIFC-236ea relative to CFC-114
-------
1.05
1.00
0.95
0.90
£ 0.85
0.80
0.75
—M—Tc=65,6°C
0.70
—Tc=79.4°C
+—Tc=107.2°C
0.65
5
0
10
15
20
25
30
35
Evaporating temperature, ®C
Figure 20. Experimental COP ratio of HFC-236ea relative to CFC-114
-------
-n—Tc=51.7°C
—A— Tci=65,6°C
-#-Tc=40.6°C
-
—X—Tc=79.4DC
i
—X—Tc=93J°C
1 1_
-*-Tc=107.2°C
1
!
0 5 10 15 20 25 30 35
Evaporating temperature, °C
Figure 21. Compressor volumetric efficiency ratio of HFC-236ea relative to CFC-114
-------
1.1
"-O
4^
& 0.9
0.7
0.6
—Tc=40.6°C
—S—Tc=51.7°C
—A—Tc=65.6°C
—X—Tc=79.4°C
-*-Tc=93.3°C
—Tcss107.2°C
i » i t i
10
" * " 1 ¦ J "¦ '
15 20
— | ' |
25 30
Evaporating Temperature, °C
35
Figure 22. Compressor isentropic energy efficiency for HFC-236ea relative to CFC-114
-------
CONCLUSIONS
Theoretical and experimental evaluation in a semihermetic compressor confirmed that HFC-
236ea should be considered as a replacement for CFC-114 in shipboard chillers. At shipboard chiller
conditions (2 to 13°C evaporating and 40 to 50°C condensing temperatures), die COP with HFC-
236ea is very close to that of CFC-114 over the range of evaporating temperature. At the same
conditions, the cooling capacities of HFC-236ea arc 2 to 12 percent lower than those of CFC-114.
The evaluations also indicate that HFC-236ea is an acceptable CFC-114 replacement in high
temperature heat pumps (0 to 35°C evaporating and 40 to 110°C condensing temperatures). There is
some drop-off in performance of HFC-236ea at condensing temperatures higher than 70°C and
evaporation temperatures lower than 20aC.
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