EPA/600/A-97/104
Alternatives for CFC-12 Refrigerant in Automotive Air Conditioning
James J. letter
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
86 T. W. Alexander Drive, MD-63
Research Triangle Park, NC 27711, USA
Francis R. Delafield
Acurex Environmental Corporation
4915 Prospectus Drive
Durham, NC 27713-4401, USA
Abstract
Ten refrigerants including CFC-12, HFC-134a, and eight refrigerant blends were tested in
an instrumented automotive air-conditioning system designed for CFC-12. The refrigerants were
compared at three test conditions for refrigeration capacity, coefficient of performance,
compressor discharge pressure, compressor discharge temperature, and evaporator outlet
pressure. Due to limitations of the testing, test results should not be used as conclusive evidence
of the performance of refrigerants. However, the results were obtained by testing all the
refrigerants in the same system under the same conditions, and the results provide an indication
of the comparative performance of the refrigerants. Refrigeration capacities for CFC-12
substitutes ranged from 9 percent lower to 9 percent higher than capacities for CFC-12.
Capacities for refrigerant blends containing HCFC-22 tended to be higher than capacities for
CFC-12 and other substitutes for CFC-12. Evaporating pressures for HFC-134a closely matched
those for CFC-12. Compressor discharge pressures for HFC-134a ranged from 4 to 8 percent
higher than those for CFC-12. Compressor discharge pressures for refrigerant blends containing
HCFC-22 were 17 to 34 percent higher than those for CFC-12. Discharge temperatures for two
of the four blends that contained HCFC-22 were more than 5C° higher than temperatures for
CFC-12. Further laboratory and field testing would be required to adequately evaluate
performance and other important refrigerant characteristics including materials compatibility,
chemical stability, fractionation, and long-term durability.
Introduction
Title VI of the 1990 Clean Air Act Amendments requires the U.S. EPA (Environmental
Protection Agency) to regulate substitutes for ozone depleting substances, including CFC
(chlorofluorocarbon)-12 '. Title VI, Section 612 mandates "that it shall be unlawful to replace
any class I or class n [ozone-depleting] substance with any substitute substance which the [EPA]
Administrator determines may present adverse effects to human health or the environment.... The
Administrator shall publish a list of (A) the substitutes prohibited under this subsection for
specific uses and (B) the safe alternatives identified under this subsection for specific uses."
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EPA implemented the Title VI, Section 612 requirements with the SNAP (Significant
New Alternatives Policy) Program in 19942. Under the SNAP Program, EPA evaluates
substitutes for effects on human health or the environment including toxicity, flammability,
ozone depletion, and global warming. Under the SNAP Program, EPA does not evaluate
performance characteristics such as refrigeration capacity, efficiency, materials compatibility,
miscibility with lubricants, and thermodynamic properties. As of June 3, 1997, 10 substitutes for
CFC-12 in motor vehicle air conditioning were listed as "acceptable subject to use conditions."
Use conditions include a requirement for unique fittings to prevent cross-contamination, a
requirement for labeling to identify refrigerants in each vehicle, a prohibition against topping off
one refrigerant with another, and a prohibition against recycling of refrigerant blends.
Additionally, refrigerant blends containing HCFC (hydrochlorofluorocarbon)-22 require the use
of barrier hoses to reduce permeation.
The substitutes listed as acceptable subject to use conditions under the SNAP Program
include HFC (hydrofluorocarbon)-l34a, three refrigerant blends containing HFC-134a, five
blends containing HCFC-22, and a blend with a composition claimed as confidential business
information by the manufacturer. Compositions of nine substitute refrigerants that were tested
for performance are shown in Table 1. Since the testing was completed, another blend called
GHG-X5 (0.41 HCFC-22 / 0.15 HCFC-142b / 0.04 isobutane / 0.40 HFC-227ea) has been listed
as acceptable under the SNAP program. Only pure HFC-134a has been endorsed as a substitute
for CFC-12 by the automotive OEMs (original equipment manufacturers). However, many of the
refrigerant blends are currently available or will be available in the U.S. market.
EPA's National Risk Management Research Laboratory performed the testing described
in this paper to provide information to EPA's regulatory office and the automotive air-
conditioning industry. Testing was conducted at the Air Pollution Prevention and Control
Division located in Research Triangle Park, North Carolina. This EPA laboratory has had prior
experience in testing automotive air-conditioning systems and refrigerants3'4'5.
Table 1. Refrigerant Composition (Percent by Weight)
Name
HFC-134a
R-406A/GHG/McCool
GHG-X4/Autofrost/ChilI-It
GHG-HP
Hot Shot/Kar Kool
FREEZE 12
FRIGCFR-12
Free Zone/RB-276
Ikon- 12
HCFC-
22
55
51
65
50
HCFC-
124
28.5
39
39
HCFC-
142b
41
16.5
31
9.5
20
19
HFC-
134a
100
*
80
59
79
Butane
(R-600)
2
Iso-
butane
(R-600a)
4
4
4
1.5
Propri-
etary
lubricant
2
Composition claimed as confidential business information
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Description of Testing
Refrigerants were tested in an instrumented, OEM, automotive air-conditioning system
designed for CFC-12. The 1993 passenger car system had an orifice tube expansion device and a
suction line accumulator. The evaporator and housing were located inside an insulated
calorimeter chamber. Refrigeration capacity was determined by measuring the power input to
electric heaters, heater fans, and evaporator fan inside the chamber. The capacity was determined
with an uncertainty of approximately ±100W and a repeatability of ±30W. COP (coefficient of
performance) was determined from the measured power input to the compressor with an
uncertainty of approximately ±75W and a repeatability of ±50W. Pressures were measured with
capacitive pressure transducers with an uncertainty of ±0.1 psia (±0.7 kPa) for 0-100 psia (0-689
kPa) and ±0.6 psia (±4.1 kPa) for 100-250 psia (689-1724 kPa). Refrigerant temperatures were
measured with an uncertainty of ±0.9 F° (0.5 C°) with thermocouple probes inserted into the
fluid. Instrumentation was similar to that described in a previous paper3.
A new compressor was broken in for 40 hours with CFC-12 refrigerant and mineral oil
lubricant. Following the break-in period, baseline tests were performed with CFC-12 and
mineral oil.
Refrigerant blends were mixed in the laboratory using an electronic scale with an
accuracy of ±0.2 gram. The Free Zone/RB-276 blend was not mixed in the laboratory because it
contains a proprietary lubricant. A 30-pound (13.6 kg) cylinder of the Free Zone/RB-276 was
obtained and the blend was charged into the system as a liquid from the cylinder. For all the
refrigerant blends, manufacturer or supplier recommendations on charging the system were
followed if they were available. Before each refrigerant was charged, the system was triple-
flushed with dry nitrogen and evacuated until the system held a vacuum of less than 25 um Hg
for 15 minutes to ensure that no significant amount of residual refrigerant or moisture remained
in the system. For all tests, minimal superheat at the compressor inlet indicated the presence of
some saturated liquid in the suction line accumulator and confirmed that the system was fully
charged.
Refrigerant manufacturer recommendations on lubricants were also followed if they were
available. The four refrigerant blends that contained HCFC-22 were tested with the same
mineral oil used with CFC-12. FREEZE 12 and FRIGC FR-12 were tested with 3 ounces (89
cm3) of POE (polyolester) lubricant added to the existing mineral oil. The POE lubricant had a
viscosity reported by the manufacturer to be 134 cSt at 40°C and 25 cSt at 100°C. Free
Zone/RB-276, containing 2 percent of a proprietary lubricant, was tested with the mineral oil
used with CFC-12. Dcon-12 was tested with a POE lubricant that had previously been tested for
compatibility with the refrigerant5. HFC-134a was tested with PAG (polyalkylene glycol)
lubricant added to the mineral oil used with CFC-12, as recommended by the OEM. When
lubricants were changed, residual lubricant was removed from the system by repeatedly flushing
with a solvent followed by evacuation to remove the solvent. The accumulator/drier was
removed each time before the system was flushed and was replaced with a new unit after
flushing. Heptane was used as a solvent to remove mineral oil and POE lubricant, and methanol
was used to remove PAG lubricant. Solvents were not used to flush the compressor, but the
compressor was repeatedly flushed with heated lubricant.
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Conditions for the three tests performed with each refrigerant are shown in Table 2.
Evaporator air inlet temperatures were set high enough to provide sufficient load to prevent
cycling of the compressor. Steady-state operation enabled measurement and comparison of
performance characteristics including refrigeration capacity, COP, pressures, and temperatures.
Although a significant part of the refrigeration load on an air-conditioning system can result from
moisture condensing on the surface of the evaporator, in the test system, air inside the evaporator
chamber was not humidified to simplify the measurement of refrigeration capacity. Relative
humidity was maintained at a low level during testing to prevent any condensation of water
vapor. Electrical potential applied to the evaporator fan motor was regulated and maintained at
10.6VDC to obtain consistent air flow through the evaporator.
Table 2. Test Conditions
Compressor rotational speed (rpm)
Evaporator air inlet temperature, °C (°F)
Condenser air inlet temperature, °C (°F)
Condenser air inlet velocity, m/s (ft/min)
Compressor ambient temperature, °C (°F)
1
1000
37.8 (100)
46.1(115)
1.02(200)
54.4 (130)
2
2000
43.3(110)
35.0 (95)
1.78 (350)
54.4(130)
3
3000
48.9 (120)
35.0 (95)
1.78(350)
54.4(130)
At each test condition, data were recorded at 30-minute intervals during a 2-hour period
to ensure steady-state operation. After initial baseline tests with CFC-12 and tests with the nine
substitutes were completed, tests were repeated with CFC-12 to ensure that system performance
had not degraded during the course of the testing. Comparisons of the final tests with the initial
CFC-12 tests are shown in Table 3. Refrigeration capacity remained within ±2 percent. At the
1000, 2000, and 3000 rpm test conditions, COP increased by 1.5, 5.4, and 3.9 percent,
respectively. This increase in COP may have resulted, in part, from additional break-in of the
compressor during the testing.
Table 3. Comparison of Final Tests with CFC-12 to Initial Baseline Tests With CFC-12
Refrigeration capacity (percent change)
COP (percent change)
1
+1.0
+1.5
2
-0.4
+5.4
3
-2.0
+3.9
Limitations of Testing
Tests results described in this paper contribute to the information available in the open
technical literature on alternative refrigerants. However, results should not be used as conclusive
evidence of any refrigerant's relative merits for the following reasons:
1. All tests were performed with one automotive air-conditioning system. Performance
may vary between different vehicle air-conditioning systems.
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2. Only three tests were performed for each refrigerant. Automotive air conditioners
operate over a greater range of conditions than represented by the test conditions.
3. Tests were performed under steady-state conditions. Automotive air conditioners
usually operate under transient conditions with changing rotational speed, changing
load conditions, changing capacity, or on/off cycling of the compressor.
4. In the laboratory, refrigerant blend composition was carefully controlled for the tests.
In the field, composition can change due to leakage or fractionation during servicing.
Performance may vary with changing blend composition.
5. Tests were performed to evaluate only air-conditioning system performance. Other
important factors involved in refrigerant evaluation include materials compatibility,
chemical stability, fractionation, and long-term durability. Extensive laboratory and
field testing is required to adequately evaluate these factors.
Discussion of Results
Refrigeration capacities for the ten refrigerants are .compared at the three test conditions
in Figure 1. Of the ten refrigerants tested, HFC-134a had the lowest capacities with values
ranging from 8 to 9 percent lower than the capacities for CFC-12. Capacities for the four blends
that contained HCFC-22 were 0 to 9 percent higher than those for CFC-12 at the three test
conditions. Capacities for the three blends that contained HFC-134a were 3 to 9 percent lower
than those for CFC-12. Refrigeration capacities for Ikon-12 were 2 to 6 percent lower than those
for CFC-12. Comparison of refrigeration capacities for Ikon-12 with those for HFC-134a is
consistent with results obtained in a previous evaluation5.
COPs are compared in Figure 2. COPs for HFC-134a ranged from 7 to 9 percent lower
than those for CFC-12. COPs for HFC-134a and the four blends that contained HCFC-22 tended
to be lower than the COPs for Ikon-12 and the three blends that contained HFC-134a.
Comparison of the COPs for Ikon-12 with those for HFC-134a is consistent with results obtained
in a previous evaluation5.
Evaporator outlet pressures are compared in Figure 3. HFC-134a evaporator pressures
most closely matched those of CFC-12 at the three test conditions. The four blends that
contained HCFC-22 had evaporator pressures that were notably higher than the pressures for
CFC-12. Ikon-12 and the three blends that contained HFC-134a had evaporator pressures that
were lower than those for CFC-12.
Compressor discharge pressures are compared in Figure 4. Discharge pressures for HFC-
134a were 4 to 8 percent higher than those for CFC-12. Compressor discharge pressures for the
four blends that contained HCFC-22 were 17 to 34 percent higher than the pressures for CFC-12.
The three blends that contained HFC-134a had discharge pressures that were lower than those for
CFC-12.
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Compressor discharge temperatures are compared in Figure 5. Discharge temperatures
for HFC-134a and for two of the blends that contained HFC-134a were more than 5C° lower
than temperatures for CFC-12. Discharge temperatures for two of the four blends that contained
HCFC-22 were more than 5C° higher than temperatures for CFC-12.
Conclusions
Due to the limitations of testing, test results should not be used as conclusive evidence of
the performance of refrigerants, as discussed above. However, the results do provide some
useful indications of performance. Results from this evaluation indicated that the refrigeration
capacities for all the refrigerants tested are likely to be adequate compared to the capacity for
CFC-12. Although HFC-134a had the lowest capacity, its'capacity was within 10 percent of that
for CFC-12. The four refrigerant blends that contain HCFC-22 had the advantage of somewhat
higher capacities than those of the other substitutes for CFC-12. Higher refrigeration capacity
can improve occupant comfort during certain operating conditions when the refrigeration load is
high compared to the available capacity.
However, the blends that contain HCFC-22 had the disadvantage of higher evaporating
and condensing pressures. Higher pressures can increase the stress on air-conditioning system
components and can have a negative effect on control systems with pressure sensing devices.
Compressor discharge temperatures for two of the four blends that contained HCFC-22 were
more than 5C° higher than temperatures for CFC-12. Higher discharge temperatures can cause
the lubricant to break down at a faster rate and may cause a reduction of the time before failure of
the system. Discharge temperatures for HFC-134a and for two of the blends that contained HFC-
134a were more than 5C° lower than temperatures for CFC-12. Lower discharge temperatures
may increase the durability of the system.
Results indicated that the COPs for all the refrigerants tested are likely to be adequate
compared to the COP for CFC-12. Refrigerants with lower COPs may cause a slight increase in
vehicle fuel consumption.
Dcon®-12 and the refrigerant blends that contain HFC-134a had the advantage of lower
condensing pressures than those of HFC-134a. Dcon®-12 and the refrigerant blends that contain
HFC-134a also had the advantage of slightly higher refrigeration capacities than those of HFC-
134a. However, all zeotropic blends have the disadvantage of potential fractionation during
installation, operation, and servicing. Performance may decline with changing blend
composition. Pure HFC-134a has no fractionation and has had more extensive testing for
materials compatibility and system durability.
Notice
Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
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CFC-12
HFC-134a
R-406A/GHG/McCool
GHG-X4/Autofrost
GHG-HP
Hot Shot/Kar Kool
FREEZE 12
FRIGC FR-12
Free Zone/RB-276
lkon-12
• 1000RPM
D 2000 RPM
3000 RPM
2.5 3 3.5 4 4.5 5 5.5
Figure 1. Refrigeration Capacity (kW)
CFC-12
HFC-134a
R-406A/GHG/McCool
GHG-X4/Autofrost
GHG-HP
Hot Shot/Kar Kool
FREEZE 12
FRIGC FR-12
Free Zone/RB-276
lkon-12
1000 RPM
2000 RPM
3000 RPM
1.4 1.6 1.8 2 2.2 2.4 2.6
Figure 2. Coefficient of Performance
2.8
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CFC-12
HFC-134a
R-406A/GHG/McCool
GHG-X4/Autofrost
GHG-HP
Hot Shot/Kar Kool
FREEZE 12
FRIGCFR-12
Free Zone/RB-276
lkon-12
• 1000 RPM
D 2000 RPM
U 3000 RPM
_L
0.25 0.3 0.35 0.4 0.45 0.5
Figure 3. Evaporator Outlet Pressure (MPa)
_L
0.55
CFC-12
HFC-134a
R-406A/GHG/McCool
GHG-X4/Autofrost
GHG-HP
Hot Shot/Kar Kool
FREEZE 12
FRIGC FR-12
Free Zone/RB-276
lkon-12
• 1000 RPM
D 2000 RPM
3000 RPM
1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9
Figure 4. Compressor Discharge Pressure (MPa)
8
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CFC-12
HFC-134a
R-406A/GHG/McCool
GHG-X4/Autofrost
GHG-HP
Hot Shot/Kar Kool
FREEZE 12
FRIGCFR-12
Free Zone/RB-276
lkon-12
• 1000 RPM
D 2000 RPM
H 3000 RPM
55 60 65 70 75 80 85 90
Figure 5. Compressor Discharge Temperature (Degrees Celsius)
Acknowledgment
The authors wish to acknowledge the assistance of Georgi S. Kazachki of Acurex
Environmental Corporation, who provided technical consultation for performance testing.
REFERENCES
1. "Title Vl-Stratospheric Ozone Protection." Public Law 101-549. November 15, 1990:
2. "Protection of Stratospheric Ozone." Federal Register. Volume 59, Number 185.
September 26, 1994.
3. letter, J.J. and F.R. Delafield. "Retrofitting an Automotive Air Conditioner with HFC-
134a, Additive, and Mineral Oil." Proceedings of the 1994 International CFC and Halon
Alternatives Conference. 1994. Pages 785-794.
4. letter, J.J., N.D. Smith, K. Ratanaphruks, A. Ng, M.W. Tufts, and F.R. Delafield.
"Evaluation of Alternatives for HFC-134a Refrigerant in Motor Vehicle Air
Conditioning." Proceedings of the 1996 International Conference on Ozone Protection
Technologies. 1996. Pages 845-854.
5. letter, J.J., N.D. Smith, K. Ratanaphruks, A. Ng, M.W. Tufts, and F.R. Delafield.
"Evaluation of Ikon®-12 Refrigerant for Motor Vehicle Air Conditioning." Society of
Automotive Engineers. Technical Paper Number 970525. 1997 SAE International
Congress and Exposition. 1997.
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NRMRL-RTP-P-264
1. REPC
EPA/600/A-97/104
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before compU
4. TITLE AND SUBTITLE
Alternatives for CFO12 Refrigerant in Automotive
Air Conditioning
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
James J. Jetter (EPA) and Francis R. Delafield
(A cur ex)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Acurex Environmental Corporation
4915 Prospectus Drive
Durham, North Carolina 27713-4401
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-D4-0005, W. A. 97-014
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper; 10/96-3/97
14. SPONSORING AGENCY CODE
EPA/60.0/13
15. SUPPLEMENTARY NOTES APPCD project officer is James J. Jetter, Mail Drop 63, 919 /
541-4830. For presentation at Int. Conf. on Ozone Protection Technologies, Balti-
more, MD, 11/12-13/97.
i6. ABSTRACT
paper gives results of testing of alternatives for chlorofluorocarbon
(CFC)-12 refrigerant in automotive air conditioning. Ten refrigerants, including
CFC-12, hydrofluorocarbon (HFC)-134a, and eight refrigerant blends, were tested
in an instrumented automotive air-conditioning system designed for CFC-12. The re-
frigerants were compared at three test conditions for refrigeration capacity, coeffi-
cient of performance, compressor discharge pressure and temperature, and evapo-
rator outlet pressure. Due to limitations of the testing, test results should not be
used as conclusive evidence of the performance of the refrigerants. However, the
results were obtained by testing all the refrigerants in the same system under the
same conditions, and the results provide an indication of the comparative perfor-
mance of the refrigerants. Further laboratory and field testing would be required
to adequately evaluate performance and other important refrigerant characteristics
including materials compatibility, chemical stability, fractionation, and long-term
durability. Refrigeration capacities for CFC-12 substitutes ranged from 9% lower
to 9% higher than those for CFC-12.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
Pollution
Substitutes
Refrigerants
Halohydrocarbons
Air Conditioning
Automotive Industry
Pollution Control
Stationary Sources
Automotive Air Condi-
tioning
13 B
14G
ISA
07C
05C,13F
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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