EPA/6QQ/A-96/114
ALTERNATIVES TO CFC-114 IN HIGH-TEMPERATURE HEAT PUMPS:
COMPRESSOR PERFORMANCE WITH HFC-236EA AND HFC-236FA
Georgi S. Kazachki
Acurex Environmental Corporation
P.O. Box 13109
Research Triangle Park, NC 27709
Cynthia L. Gage and Robert V. Hendriks
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Research Triangle Park, NC 27711
ABSTRACT
Comprehensive calorimeter tests on a semi-hermetic compressor were performed with
CFC-114, HFC-236ea, and HFC-236fa over a wide range of temperature test conditions:
evaporating temperatures from 0 to 35° C and condensing temperatures from 40 to i 10°C. More
than 600 tests were ran at 66 test conditions with the three refrigerants. The following parameters
were assessed as criteria for performance evaluation and for reliable performance: cooling
capacity; electric power input, current, and voltage; coefficient of performance; compressor
volumetric and isentropic efficiencies; and discharge and oil temperatures. Polyolester oil was
used as lubricant in the compressor. The oil charge was unchanged when switching refrigerants.
With all three refrigerants, the compressor ran 1,800 hours without failure and without indication
of excessive noise or vibration.
INTRODUCTION
For decades, chlorofluorocarbon (CFC)-l 14 has been the refrigerant of choice in high-
temperature, high-lift vapor-compression heat pumps. Its thermal stability and wet isentropic
compression allowed for operation at condensing temperatures of up to 120°C and in some
instances even higher without refrigerant decomposition or chemical reactions with the oil or
with construction materials. The wet isentropic compression of its saturated vapor meant that the
discharge temperatures did not significantly exceed the condensing temperatures even at high
suction superheat. As a result, the compressor was able to handle high condensing temperatures
without risk of damage. After the ban on the production of chlorine-containing refrigerants, a
replacement for CFC-114 was needed. Since this refrigerant was also the refrigerant of choice in
surface craft and submarine air-conditioning systems, the need for alternatives to CFC-114
became even more urgent Under these circumstances, the Environmental Protection Agency
(EPA) ii i cooperation with the Electric Power Research Institute (EPRI) initiated a search for new
compounds to be identified and synthesized as replacements for all chlorine-containing
refrigerants (1,2,3). From this work, two isomers were recognized as primary candidates for
CFC-114 alternatives: hydrofluorocarbon (HFC)-236ea and HFC-236fa.
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Early analyses focused on HFC-236ea as a replacement for CFC-114 in chiller
applications (4,5,6). Calorimeter tests with a semi-hermetic compressor were also reported at
chiller conditions for this refrigerant (7). Later, thermodynamic evaluations were performed on
both HFC-236fa and HFC-236ea at high-temperature heat pump conditions (8). These
evaluations indicated that both refrigerants would have wet isentropic compression similar to
CFC-114. However, HFC-236fa had cooling capacities from 0 to 20% higher than CFC-114,
while HFC-236ea was predicted to have capacities ±6% of those for CFC-114 at all but the
highest condensing temperature. The COPs (coefficients of performance) for both HFC-236fa
and HFC-236ea were found to be close to those for CFC-114 except at condensing temperatures
greater than 80°C.
Atmospheric lifetimes of the two isomers have been measured(9). HFC-236fa has a
relatively long atmospheric lifetime of 194 years, while the lifetime for HFC-236ea is only 10
years. Recent material compatibility studies show that both isomers have acceptable
performance with several different elastomers and desiccant materials(lO).
TEST METHOD AND PROCEDURE
Experimental evaluation of the CFC-114 alternatives was done on a compressor
calorimeter test rig with a semi-hermetic compressor. The original calorimeter was modified for
low-pressure refrigerants to eliminate excessive pressure drops. These modifications were
detailed in earlier publications(7). The semi-hermetic compressor had a 0.56 kW motor and
delivered 1.329 L/s at 1750 RPM. The compressor was designed for use with HFC refrigerants
and was lubricated by polyolester oil.
Tests were performed using ASHRAE Standard 23-1993(11) as a basis. The cooling
capacity was determined by two methods: a primary method based on the quantity of electrically
supplied heat to the calorimeter boiler and a secondary method based on the heat balance of the
water-cooled condenser. The secondary method was not available at the highest condensing
temperature because the water flashed to steam. Agreement between the two methods was better
than 3%. Each test condition was evaluated three times, and the resulting values were averaged.
The standard deviation of the average value for any given parameter was never greater than 2%.
The primary method was also used to determine the refrigerant mass flowrate. This value was
used, along with the enthalpy difference between the compressor discharge at the measured
conditions and the condition of saturated liquid at the condensing pressure, to determine the
heating capacities. With all three refrigerants, the compressor ran 1,800 hours without failure and
without indication of excessive noise or vibration, a positive indicator for field performance.
Tests were performed at evaporating temperatures from 0 to 35°C and condensing
temperatures from 40 to 110°C. A few degrees of subcooling was achieved in the condenser to
ensure liquid feeding to the expansion valve. Similarly some superheating was achieved in the
evaporator to ensure that no liquid reached the compressor to avoid wet compression. All results
for the cooling capacities were corrected back to conditions of saturated liquid leaving the
condenser and saturated vapor leaving the evaporator.
2
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RESULTS
Table 1 presents an example table for HFC-236ea at 32.2°C evaporating and 65.6°C
condensing temperatures. Similar tables were generated for all refrigerants at all test conditions.
Due to the significant number of tests performed (more than 600 tests at 66 test
conditions with the three refrigerants), representative results at 10 and 32.2°C evaporating
temperatures are presented graphically. As a result of the upper capacity limit of the calorimeter,
data could not be collected for HFC-236fa at the 32.2°C evaporating and 51.7°C condensing
temperatures. The lower critical temperature for HFC-236fa (130.65°C) compared to HFC-
236ea(141.15°C) and CFC-114 (145.65°C) also prevented measurements at 107.2°C for this
chemical.
Figures 1 and 2 present the cooling capacities of all three refrigerants at 10°C and 32.2°C
evaporating temperature, respectively. As predicted, cooling capacities for HFC-236fa were
from 0 to 25% higher than for CFC-114. For HFC-236ea, the cooling capacities as compared to
CFC-114 were slightly lower than predicted. Heating capacities for the three refrigerants at both
temperatures are shown in Figures 3 and 4. Again, HFC-236fa had capacities up to 25% higher
than CFC-114, while HFC-236ea has heating capacities slightly less.
Electrical power input to the compressor is shown in Figures 5 and 6. At 10°C
evaporating, the power input requirements for HFC-236fa were about 10% more than for CFC-
114. This requirement increased to about 14% at 32.2°C evaporating. HFC-236ea required
about 5% less electrical input at the lower evaporating temperature and had almost identical
power input as CFC-114 at the higher temperature. The cooling COP is shown in Figures 7 and
8. For HFC-236fa, the COP is similar to higher than CFC-114 at condensing temperatures lower
than 79.4°C. This performance was better than predicted. The performance becomes up to 10%
poorer at the higher condensing temperatures. For HFC-236ea, the COPs are similar to lower
than CFC-114 at all conditions. This agrees with the theoretical expectations.
Compressor isentropic energy efficiency is shown in Figures 9 and 10. For HFC-236fa,
this efficiency is higher than CFC-114 at all conditions. This explains why the measured COPs
were higher than expected. The energy efficiency for HFC-236ea is similar to CFC-114 at
condensing temperatures less than 79.4°C, but is poorer at higher condensing temperature.
Compressor volumetric efficiencies are presented in Figures 11 and 12. For HFC-236fa, these
efficiencies are very close to those of CFC-114. For HFC-236ea, the efficiencies are lower than
for CFC-114, explaining why measured cooling capacities were lower than predicted.
CONCLUSIONS
1. Both HFC-236fa and HFC-236ea are viable alternatives for CFC-114 in high temperature heat
pumps. The shorter atmospheric lifetime for HFC-236ea is also favorable.
2. HFC-236fa was found to have better cooling and heating capacities than both HFC-236ea and
3
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CFC-114 at almost all conditions tested. Capacities for HFC-236ea were similar to those of
CFC-114.
3. Electric power input for HFC-236fa was higher than for CFC-114, while input for HFC-236ea
was lower. When combined with cooling capacities, this resulted in COPs similar to CFC-114
for both alternatives.
4. The low critical temperature for HFC-236fa may be a limiting factor in some heat pump
applications.
REFERENCES
1. Adcock, J.L., S.B. Mathur, W.A.Van Hook, H.Q.Huang, M. Narkharde, and B.H.Wang,
"Fluorinated Ethers: A New Series of CFC Substitutes," Proceedings of the 1991 International
CFC and Halon Alternatives Conference, Baltimore, MD, 1991, 386-395.
2. Beyerlein, A.L., D.D. Des Marteau, S.H. Hwang, N.D. Smith, and P. Joyner, "Physical
Property Data on Fluorinated Propanes and Butanes as CFC and HCFC Alternatives,"
Proceedings of the 1991 International CFC and Halon Alternatives Conference, Baltimore, MD,
December 1991, 396-405.
3. Smith, N.D. "New Chemical Alternatives for CFCs and HCFCs," EPA-600/F-92-012, March
1992.
4. Smith, N.D., K. Ratanaphmks, M.W. Tufts, and A.S. Ng, "HFC-236ea: A Potential
Alternative for CFC-114," Proceedings of the 1993 International CFC and Halon Alternatives
Conference, Washington DC, October 1993, 150-157.
5. Kazachki, G.S., and C.L. Gage, "Thermodynamic Evaluation and Compressor Characteristics
of HFC-236ea and HFC-245ca as CFC-114 and CFC-11 Replacements in Chillers," Proceedings
of the 1993 International CFC and Halon Alternatives Conference, Washington, DC, October
1993. 167-176.
6. Kazachki, G.S., and R.V. Hendriks, "Calorimeter Tests of HFC-236ea as a CFC-114
Alternative and HFC-245ca as a CFC-11 Alternative," Proceedings of the 1993 International
CFC and Halon Alternatives Conference, Washington, DC, October 1993, 158-166.
7. Kazachki, G.S., and R.V. Hendriks, "Performance Testing of a Semi-hermetic Compressor
with HFC-236ea at CFC-114 Chiller Conditions," Proceedings of the 1994 International
Refrigeration Conference at Purdue University, West Lafayette, IN, July 1994,407-411.
8. Kazachki, G.S., C.L. Gage, R.V. Hendriks, and W.J. Rhodes, "Investigation of HFC-236ea and
HFC-236fa as CFC-114 Replacements in High-Temperature Heat Pumps," CFCs: The Day After,
Padua, Italy, September 1994, 155-162.
9. DeMore, W.B., S.P. Sander, C.J. Howard, A.R. Ravishankara, D.M. Golden, C.E. Kolb, R.F.
Hampson, M.J. Kurylo, and M.J. Molina, "Chemical Kinetics and Photochemical Data for Use in
Stratospheric Modeling, Evaluation Number 11," Jet Propulsion Laboratory Publication 94-26,
1994.
10. Ratanaphmks, K., M.W. Tufts, A.S. Ng, and N.D. Smith,"Material Compatibility
Evaluations of HFC-245ca, HFC-245fa, HFE-125, HFC-236ea, and HFC-236fa,"For presentation
at the International Conference On Ozone Protection Technologies, Washington, DC, October
1996.
4
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11. ASHRAE Standard 23-1993, "Methods of Testing for Rating Positive Displacement
Refrigerant Compressors and Condensing Units," American Society of Heating, Refrigerating
and Air-Conditioning Engineers, Atlanta, GA, 1993.
5
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TABLE 1: TEST CONDITIONS AND MAIN RESULTS FROM THE CALORIMETER TESTS OF THE SEMI-
HERMETIC COMPRESSOR WITH HFC-236ea:
Symbols: p, - suction pressure, kPa; p2 - discharge pressure, kPa; TEi - temperature at the evaporator inlet, °C; T^ - saturated
vapor temperature at suction pressure, °C; Tcst - saturated temperature at discharge pressure, °C; TCj - temperature at
the condenser inlet, °C; TSH - temperature at the evaporator exit, °C; Tsc - temperature before the expansion valve,
°C; T, - temperature at the compressor inlet, °C; Ta - temperature at the compressor outlet, °C; TOIL - oil temperature
at the sump bottom, °C; QEP - cooling capacity from the primary method, W; QESC - cooling capacity from the
condenser secondary method, W; 6Q- relative deviation of the secondary condenser method from the primary method,
%; Pel - electrical input power into the compressor at the real conditions, W; V - Voltage, V; Ic - compressor motor
current, A; COP - coefficient of performance; Q„ - heating capacity (heat transferred to the water), W; COPH-
heating coefficient of performance; Ac - compressor volumetric efficiency, %; T|c - compressor energy efficiency, %;
SD - standard deviation.
Remarks:
1. Test conditions: T,; = 32.2°C Tr = 65.6DC
Test
P.
P2
tf.
^est
TCl
Tcst
Tsh
Tsc
T,
Ta
Ton.
Qe"
QfSC
8Q
Pd
V
Ic
COP
Qh
COPH
\c
tic
325
260.9
696.9
32.3
32.2
71.4
65.6
42.1
60.1
41.6
72.4
51.3
1951
1971
1.0
611
115
7.11
3.2
2553
4.18
82.1
45.5
326
260.3
696.8
32.4
32.2
71.7
65.6
42.1
60.2
41.6
72.8
52.2
1951
1975
1.2
612
115
7.13
3.2
2561
4.18
82.4
45.5
327
260.8
696.7
32.4
32.2
71.7
65.6
42.1
60.3
41.6
72.8
52.2
1956
1979
1.1
612
115
7.12
3.2
2565
4.19
82.4
45.6
Avg
260.7
696.8
32.4
32.2
71.6
65.6
42.1
60.2
41.6
72.7
51.9
1953
1975
1.1
612
115
7.1
3.2
2560
4.18
82.3
45.5
OU
0.32
0.1
0.1
0.0
0.2
0.0
0.0
0.1
0.0
0.2
0.5
3.2
3.8
NA
0.5
0.0
0.0
0.0
6.1
0.01
0.15
0.03
NA - not applicable
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1400
1200
1000
a.
(S
U
t>0
c
"o
o
O
600
400
200
|IIFC-236fa ®HFC-236eanCFC-114
40.6
93.3
51.7 65.6 79.4
Condensing Temperature (°C)
Figure 1: Cooling Capacity at 10°C Evaporating.
2000
? 1500
o
m
S-
U
bfl
C
8 500
X
|HFC-236fa fflHFC-236eanCFC-114
40.6 51.7 " 65.6 79.4 " 93.3
Condensing Temperature (°C)
Figure 3: Heating Capacity at 10°C Evaporating.
HFC-236fa W HFC-236ea O CFC-114
•S 1000
51.7 ' 656 79.4 93.3 107.2
Condensing Temperature (°C)
Figure 2; Cooling Capacity at 32.2°C Evaporating.
3500
3000 4
C 2500
&
"I 2000
a.
8 1500
60
c
Hi iooo
-------
HFC-236fa m HFC-236ea n CFC-114
S 400
40.6
93.3
51.7 65.6 79.4
Condensing Temperature (°C)
Figure 5: Compressor Electrical Power Input
at 10°C Evaporating.
CO
2.5
ex.
O
a
n
§
g
<3
s*
w
1.5
0.5
I HFC-236fa m HFC-236ea ~ CFC-114
40.6
51.7 65.5 79.4
Condensing Temperature (°C)
Figure 7: Cooling Coefficient of
Performance at 10°C Evaporating
93.3
HFC-236fa
700
3 HFC-236ea n CFC-114
51.7
107.2
65.6 79.4 93.3
Condensing Temperature (°C)
Figure 6: Compressor Electrical Power Input
at 32.2°C Evaporating.
0m
o
g
¦§ 2
k. *¦
a.
x
W ,
|HFC-236fa jg§HFC-236eaQCFC-l 14
51.7
65.5 79.4 93.3
Condensing Temperature (°C)
Figure 8: Cooling Coefficient of
Performance at 32.2°C Evaporating.
107.2
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6
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Compressor Energy Efficiency (%)
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