EPA/600/A-96/007
EVALUATION OF R-22 ALTERNATIVES FOR HEAT PUMPS
Y. Hwang
J.F. Judge
R. Radermacher
Center for Environmental Energy Engineering
University of Maryland
College Park, Maryland 20742-3035
ABSTRACT
This study investigates three different possibilities for replacing
refrigerant R-22 with R-407C in a heat pump. The first and simplest
scenario is the retrofit with no hardware modification at all. This
scenario resulted in cooling and heating capacities of 79 to 103 % and
coefficients of performance (COPs) of 76 to 95 % of the R-22
baseline. The second possibility investigated is the path modification
that requires altering the refrigerant path to attain a near-counterflow
configuration in the indoor coil for the heating mode. The path
modification improves the heating capacity by 2 to 16 % and the
heating COP by 10 to 18 % as compared to the retrofit case. The third
and most complex possibility is soft optimization consisting of
maximizing the COPs in the heating and cooling modes by optimizing
refrigerant charge and expansion devices. The soft optimized system
with R-407C has a -3 to +1% different capacity and a -8 to -4 %
different COP in the cooling and heating modes than those of R-22.
INTRODUCTION
The accelerated technical development and economic growth of
most countries during the last century have produced severe
environmental problems. Many manufactured products contributing
to human comfort have side effects threatening our health as a result
of harming the environment. The greatest inventions ill thermal
engineering which contribute to comfortable living are the refrigerator
and air-conditioner. The first supplies cold water and ice and preserves
food. The second cools and removes moisture in the air and separates
indoor space from the hot and humid outdoor environment. CFCs
(chlorofluorocarbons) and HCFCs (hydrochlorofluorocarbons) have
been used in refrigerators and air-conditioners as working refrigerants
and blowing agents in foam. CFCs are being regulated and HCFCs
will be regulated because of stratospheric ozone depletion and global
warming (Reed, 1993). The refrigerator and car air-conditioner
industries have already responded to this challenge. We can now buy
refrigerators and car air-conditioners that use non-ozone-depleting
hydrofluorocarbon HFC-134a. Within a limited time, the HCFCs,
including R-22, also have to be replaced.
Theoretical analysis was used to screen possible replacement
mixtures for CFC and HFC refrigerants (Domanski and Didion, 1993;
Radermacher and Jung, 1991).
Experimental results showing performance within ± 10% of R-22's
performance were presented by refrigerant manufacturers using their
proposed refrigerant mixtures (Bivens et a!., 1994; Ferrari ct al„ 1994;
Spatz and Zheng,1993). Although much research has already gone
into R-22 substitutes, the problem is not solved completely. To
contribute to the evaluation of R-22 alternatives, an experimental study
on what was seen to be the most probable replacement refrigerant was
initiated at the Center for Environmental Energy Engineering (CEEE).
In this study, the "retrofit" performance of HFC-32/125/134a
(23/25/52 wt. %), R-407C, was evaluated, and system hardware
modifications such as "path modification" and "soft optimization"
were tested to match the performance of R-407C with that of R-22.
DEFINITIONS
In this study, three options were investigated to evaluate the
performance of the conventional refrigerant, R-22, and the refrigerant
mixture, R-407C. They are defined as follows.
(1)	Retrofit: The refrigerants, R-22 and R-407C were used in an
existing system without changing any system hardware. The
refrigerant charge was optimized to maximize coefficient of
performance (COP) at ASHRAE1 cooling test A condition.
(2)	Path Modification (R-407C only): The refrigerant path within
the indoor coil was modified by adding four additional check valves to
supply the refrigerant to the indoor coil always in the same direction
regardless of the action of the four-way valve. This was done to
maintain near-counterflow heat exchange between refrigerant and air.
' ASHRAE: American Society of Heating, Refrigerating and Air-
Conditioning Engineers, Inc., Atlanta, GA

-------
TABLE 1 ASHRAE TEST CONDITIONS (ASHRAE, 1983)
Test
Indoor Dry
Indoor Wet
Outdoor Dry
Outdoor Wet

Bulb
Bulb
Bulb
Bulb

[°cmj
l°C (°F)J
[°C (°F)]
[°C (°F)]
A
26.7(80)
19.4 (67)
35.0(95)
23.9(75)
B
26.7(80)
19.4 (67)
27.8 (82)
18.3(65)
High Temp.
21.1 (70)
si 5.6 (60)
8.3 (47)
6.1 (43)
Low Temp.
21.1 (70)
s 15.6 (60)
-8.3(17)
- 9.4 (15)
(3) Soft Optimization (R-22 and R-407C): The refrigeration cycle
was optimized for both cooling and heating performances. The
combination of the expansion devices and the refrigerant charge was
chosen to maximize both the cooling COP for ASHRAE cooling test
A and the heating COP for ASHRAE heating test 47S.
EXPERIMENTAL SETUP AND PROCEDURES
Test Facility
A test facility, called a psychrometric calorimeter, was set up to
measure the steady state performance of a air-to-air heat pump. The
test chamber could simulate the summer and winter climate conditions
defined by ASHRAE Standard 116, Table 1 (ASHRAE, 1983).
The test facility consisted of a closed indoor loop, an environmental
chamber, and a data acquisition system. The closed indoor loop was
equipped with devices which measured the dry bulb and dew point
temperatures of the air, and a nozzle which measured the air flow rate
downstream of the test unit. The desired air flow rate for the indoor
side was adjusted by an inverter that controls the speed of an additional
blower located in the air handler. This blower was used to overcome
the additional pressure drop caused by mixing devices, nozzle, and air
handler. The frequency setting for the inverter was carefully adjusted
to obtain the specific air flow rate of 22.7 m'/min (800 ftVmin) for
both the cooling and heating modes.
Test Unit
The test unit was a 7.0 kW capacity split heat pump system. The
test unit used a reciprocating compressor and two expansion devices.
One expansion device was a thermostatic expansion valve (TE V) for
the heating mode and the other was a short tube restrictor (S.T.) for
the cooling mode. The inside diameter of the S.T. shipped originally
was 1.50 mm (0.0590 in). Figure 1 shows the heat exchange
configuration for the indoor coil. The indoor unit was installed at an
inclination of 20° from the vertical position of the wall with downward
air flow as shown in Figure 1.
The refrigerant circuit of the test unit is shown in Figure 2. The
refrigerant flow direction can be switched by the action of a four-way
valve. The indoor coil piping configuration was changed so that the
system could be operated in two modes as shown in Figure 2. The
original configuration allows near-counterflow heat exchange between
the refrigerant and the air during the cooling mode, but becomes a
near-parallelflow heat exchanger during the heating mode because of
the action of the four-way valve. With the new arrangement, termed
"path modification." the near-counterflow heat exchange can be
utilized for both modes.
Capacity Measurement
The experiments to measure the capacity were performed based on
ASHRAE Standard 116, and ARI2 Standard 210/240. The air
enthalpy method and the refrigerant enthalpy method were used for
the capacity measurement in this study. The air enthalpy method was
used as a primary method and the refrigerant enthalpy method was
used as a secondary method to confirm the reliability of data. To
confirm tiiat the data are reliable, the capacity determined using these
two methods should agree within 6% of each other as required by
ASHRAE Standard 116. The two methods agreed within 3% for all
tests conducted in this study.
In the loop air enthalpy method, the total capacity is calculated as a
sum of the sensible and latent capacities. The sensible capacity is
determined from measurement of the air flow rate, the humidity ratio,
the air temperature entering the indoor unit, and the air temperature
exiting the indoor unit. The latent capacity is calculated from the
humidity ratio difference between inlet and outlet of the indoor coil.
In the refrigerant enthalpy method, the refrigerant mass flow rate and
the refrigerant enthalpies at the inlet and outlet of the heat exchanger
are used to calculate the refrigerant-side capacity. The mass flow rate
is measured by a mass flow meter, and the refrigerant enthalpies are
calculated by using the REFPROP database V4.0 (Gallagher et al.,
1993) from the temperature and pressure of the refrigerant at the inlet
and outlet of the indoor coil. Then the capacity is calculated from the
energy balance for the indoor coil.
After the test conditions were set, the test unit and the reconditioning
apparatus for the indoor loop and outdoor environmental chamber
were operated until equilibrium conditions were attained within the
test tolerances specified in ASHRAE Standard 116. An hour after the
equilibrium condition was attained, the data acquisition program was
started to obtain data at 1 minute intervals for 1 hour. Then the data
were averaged for every 5 minutes, and the 12 sets of data were used
as an input for an energy balance program.
Test Procedures
The experimental tests were carried out with refrigerants R-22 and
R- 407C. First, the R-22 "baseline" test and the "retrofit" test for R-
407C were carried out without making modifications except changing
the lubricant in the compressor and adding a filter drier for the mixture
tests. The optimum charge that gave the maximum COP at ASHRAE
Cooling test A condition was found for each refrigerant. After the
optimum charge was found, ASHRAE tests were carried out to
compare the performance of each refrigerant. Second, the "path
modification" was implemented to improve the performance of the
system with R-407C. Third, the "soft optimization" was carried out
for both R-22 and R-407C. The reported capacity and COP values
were based on air-side values. The refrigerant-side values were used
only to check the total energy balance and to prove the validity of the
test.
! ARI: Air- Conditioning and Refrigeration Institute, Arlington, VA
2

-------
TEST RESULTS AND DISCUSSION
R-22 Charge Optimization Test
The charge optimization test results for R-22 are shown in Figure 3.
When increasing the charge, the capacity and COP for R-22 increase
to a maximum point and then decrease. COP for R-22 reaches a
maximum at approximately 4.0 kg (8.8 lb) charge, and the capacity
reaches a maximum at 4.2 kg (9.2 lb) charge. By increasing the
charge, the amount of subcooling increases, while the superheat
decreases. Throughout the ASHRAE tests, the refrigerant charge was
maintained at 4.0 kg (8.8 lb) which corresponded to the maximum
COP for ASHRAE Cooling test A.
Figure 4 shows the effect of charge on COP, power input, pressure
ratio, and refrigerant mass flow rate. With increasing refrigerant
charge, the system pressure increases. This causes a pressure and
temperature increase in the evaporator and condenser while the system
is running. Moreover the evaporating pressure rises faster than the
condensing pressure does, causing a pressure ratio decrease. Then, the
compressor can accept and discharge more refrigerant, resulting in a
higher mass flow rate. With increased mass flow rate, the compressor
has to do more work, resulting in increased energy consumption. With
increased mass flow rate, more heat is absorbed by the evaporator, and
the temperature distribution of indoor coil is changed. Indoor coil
temperature variation with charge for the case of R-22 charge
optimization with a S.T. 1.50 mm (0.0590 in) is represented in Figure
5. Approximately half of the evaporator contains two-phase flow until
a 3.9 kg (8.5 lb) charge is reached. At 4.1 kg (9.0 lb), roughly 75%
of the evaporator contains two-phase flow and, here, exhibits the
highest COP. It is evident that the capacity increases with charge
increase. The evaporating temperature also increases with charge
increase. Increasing the charge beyond 4.3 kg (9.5 lb) has a negative
effect because the temperature difference between air and refrigerant
has been reduced.
After the charge optimization tests, the ASHRAE tests as given
previously in Table 1 were carried out for R-22 with the optimum
charge.
Modifications for the Refrigerant Mixture
Before the mixture was tested, the compressor was separated from
the cycle, the oil remaining in the compressor was drained, and the
compressor was flushed with solvent. The system piping and heat
exchangers were also flushed. The refrigerant mixture, R-407C,
tested is composed of HFC refrigerants only. In testing HFC
refrigerant mixtures, an ester based oil was used. The filter drier was
also exchanged for a drier that was originally developed for R-134a.
Before charging the system, the concentration of the mixture was
checked with a gas chromatograph. The concentration agreed with
desired composition within ± 0.8 wt.%. The result of the
concentration measurement of R-407C is compared with the desired
composition and the manufacturer's data in Table 2.
R-407C Charge Optimization Test
The mixture, R-407C, was first tested as a "retrofit." Only the
refrigerant charge was optimized to obtain maximum COP. The same
procedure used for R-22 was used for the charge optimization test of
R-407C. The results are shown in Figure 3. The COP is maximum
TABLE 2 COMPARISON OF R-407C CONCENTRATION
Component
Desired
Manufacturer's
Data

Composition
Data
Measured
R-32
0.23 [wt %]
0.229 [wt %]
0.226 [wt %]
R-125
0.25 [wt %]
0.236 [wt %]
0.258 [wt %]
R-I34a
0.52 [wt %J
0.534 [wt %]
0.517 [wt %]
TABLE 3 COMPARISON OF ASHRAE COOLING A
TEST RESULTS

R-22
R-407C
R-407C
R-22
R-407C

Base
Retrofit
Path
Soft
Soft



Modi.
Opti
Opti.
Capacity [kW]
6.95
7.13
6.69
6.82
6.89
COP
3.08
2.94
2.91
3.20
3.06

85.5
82.0
77.8
76.3
78.1
T^J°C]
22.6
21.8
19.6
18.0
23.3
P^fkPa]
1768.7
2124.2
1959.6
1641.8
1825.9
P^[kP"]
Pressure Ratio
712.7
736.2
699.8
707.5
704.6
2.48
2.89
2.80
2.32
2.59
Subcooling [°CJ
9.6
14.0
10.4
4.0
4.8
Superheat f°Cl
11.1
11.3
10.8
6.7
14.3
TABLE 4 COMPARISON OF ASHRAE HEATING 47S
TEST RESULTS

R-22
R-407C
R-407C
R-22
R-407C

Base
Retrofit
Path
Soft
Soft



Modi.
Opti.
Opti.
Capacity [kW]
6.24
5.84
5.98
6.13
5.95
COP
3.03
2.53
2.79
3.13
2.96

83.2
96.5
86.3
81.4
77.1
T^J°C]
8.7
9.9
9.0
9.2
8.9
P^PcPo]
1793.9
2678.9
2236.6
1678.5
1860.3
P^pfkPa}
507.4
502.9
483.1
494.6
478.9
Pressure Ratio
3.54
5.33
4.63
3.39
3.88
Subcooling [°C]
21.1
39.9
29.9
20.2
21.4
Suuerheat f°Cl
9.9
11.3
11.6
9.5
11.7
at approximately 4.0 kg (8.8 lb) which is the same as that of R-22.
After these tests, ASHRAE tests were carried out with the optimum
change. The results for both R-22 and R-407C arc listed in Tables 3,
4, and 5.
Path Modification Test
The indoor coil of the test unit has a quasi-crossflow heat exchange
configuration. In the cooling mode, the refrigerant flows from bottom
to top, whereas in the heating mode the refrigerant flows from top to
bottom as shown in Figure 1. The heat exchange pattern between air
and refrigerant is ncar-counterflow for the cooling mode, but it is near-
parallelflow for heating. The indoor coil path was changed by
installing four additional check valves as shown in Figure 2. With this
path modification, the refrigerant can be supplied to the indoor coil
3

-------
from bottom to top for both cooling and heating modes to maintain a
near-counterflow heat exchange between air and refrigerant.
Comparison of R-22 Baseline. R-407C Retrofit and Path
Modification
The retrofit and path modification test results for R-407C are
compared with R-22 baseline test results in Tables 3 and 4 for cooling
test A and heating test 47S. In Table 5, the test results for cooling test
B and heating test 17L are compared. The retrofit test results for R-
407C show a 2.6% higher capacity and a 4.5% lower COP in the
cooling A case (Table 3), and a 6.4% lower capacity and a 16.5%
lower COP in the heating 47S case (Table 4) as compared to the R-22
baseline. Cooling test B has similar results to cooling A case (Table
5), while heating test 17L has a greater degradation than the heating
47S case (Table 5). The cooling results are similar to the Alternative
Refrigerant Evaluation Program (AREP) results shown in Table 6
(Godwin, 1993), but the heating results show more degradation.
Although R-407C has similar thermodynamic characteristics to R-22,
some key cycle parameters are different. R-407C shows a 16.5%
higher pressure ratio compared to that of R-22 for the cooling A case.
Also, the cycle shifts to higher evaporating and condensing pressures.
The higher pressure ratio lowers the compressor efficiency. Although
R-407C has a slightly higher capacity, it has a lower COP.
R-407C retrofit shows more degradation for heating than for
cooling. This can be explained by the heat exchange configuration of
the indoor coil as shown in Figures 1 and 2. As already mentioned, the
heat exchanger configuration contributes to the capacity degradation
in the heating mode, especially for mixtures that have a temperature
glide.
Path modification results show a 3.7% lower capacity and a 5.5%
lower COP for cooling test A as compared to that of R-22. The
reason is that the four additional check valves cause additional
pressure drop, resulting in a lower mass flow rate and a lower
evaporating pressure. But it shows a significant improvement, 10.3%,
in the heating COP for heating test 47S, as compared to the retrofit
case. The greatest improvement for path modification can be observed
in low temperature heating test 17L: 15.6% for capacity and 17.6%
for COP. The refrigerant temperatures along the cycle for retrofit and
path modification are compared in Figures 6 and 7, for cooling test A
and heating test 47S. In these figures, the x-axis is not to scale; it
indicates just the sequence of each temperature probe as the refrigerant
passes on its way through the cycle. The first point is the compressor
discharge and the last point is the compressor inlet. The profile for the
cooling of R-407C is similar to that of R-22. The heating case shows
a higher compressor discharge temperature and a lower evaporating
temperature than that of R-22, resulting in a high pressure ratio for R-
407C. The temperature profiles in the indoor coil, the condenser,
show large differences. These temperature profiles explain the
performance degradation of the retrofit case which had the large
temperature difference because of the near-parallelflow configuration.
They also explain the performance improvement due to path
modification which resulted in a small temperature difference because
of the near-counterflow configuration. The path modification can
improve the performance by reducing the thermodynamic
irreversibility.
TABLE 5 COMPARISON OF ASHRAE COOLING B AND
HEATING 17L TEST RESULTS

R-22
R-407C
R-407C
R-22
R-407C

Base
Retrofit
Path
Soft
Soft



Modi
Opti.
Opti.
"B " Capacity [kW]
7.12
7.13
7.15
7.34
7.16
"3" COP
3.52
3.22
3.40
3.78
3.49
"17L" Capacity [kW]
3.40
2.69
3.11
2.77
2.75
"17L-COP
2.09
1.59
1.87
1.97
1.82
TABLE 6 COMPARISON OF SOFT OPTIMIZATION
RESULTS WITH AREP DATA
Cooling	Heating
Capacity COP	Capacity COP
Present Study 0.98-1.01 0.92-0.96 0.97-0.99 0.92-0.95
AREP Result 0.93-1.01 0.90-0.97 0.98-1.02 0.93-1.02
Note: The above data are the ratios of R-407C performance to R-22 performance
Although the path modification improved the performance of the R-
407C over the retrofit, it still has degradation as compared to R-22,
especially in the heating mode: a 4.2% lower capacity and a 7.9%
lower COP at heating test 47S. The reason for this degradation is that
the retrofit was performed after the charge was optimized at cooling
test A condition without optimizing at the heating test condition. So
it is natural to degrade the heating performance. These results indicate
that more extensive optimization is necessary.
Soft Optimization Test Results
To improve the steady state performance of the mixture, the soft
optimization was carried out for R-22 and R-407C, which could
reconcile the imbalance between the cooling and heating optimums.
At first, heating test 47S was conducted to obtain the optimum charge
for heating. The results are shown in Figure 8. The charge that has
the maximum COP is 3.6 kg (8.0 lb) for R-22 and 3.4 kg (7.5 lb) for
R-407C. To obtain the same optimum charge for cooling, the S.T.
diameter was increased. Optimum charge tests for each S.T were
carried out with charge increments of 0.2 kg (0.5 lb). Figures 9 and 10
show the change of capacity and COP with refrigerant charge for R-22
and R-407C, respectively. The results show that R-22 has the same
optimum charge for the cooling and heating modes with a 3.6 kg (8.0
lb) charge and a 1.65 mm (0.0650 in) S.T., while R-407C has the
same optimum charge for both modes with a 3.4 kg (7.5 lb) charge
and a 1.70 mm (0.0670 in) S.T. Therefore soft optimization has a 10-
15 % less refrigerant charge and a 10-14% larger S.T. than those of
the retrofit case.
Another trend observed was the change in the amount of subcooling
and superheating. As the charge was increased, the subcooling
increased but the superheat decreased. Increasing the size of the S.T.
with the same charge decreases both the subcooling and superheat.

-------
Since the refrigerant mass flow rate increases as (he charge increases,
a greater portion of the evaporator can be used, and the superheat is
reduced. The decrease in the superheat at the compressor inlet reduces
the superheat of the compressor outlet, and the rise in refrigerant mass
flow rate increases the capacity of the condenser. Therefore, the
suboooling increases with increasing refrigerant charge because of the
increased condenser capacity and the reduced superheat of the
compressor outlet. Moreover, these phenomena can be retarded by
decreasing the size of the S.T., because of the decreased mass flow
rate.
After the charge optimization of the heating and cooling modes,
ASHRAE tests were carried out with the optimum S.T. and refrigerant
charge. Test results are shown in Tables 3,4, and 5.
Comparison of Soft Optimization for R-22 and R-407C
As can be seen in Tables 3 and 4, the pressure ratio of R-22 after
soft optimization is reduced by 6.5 % for cooling test A and by 4.2%
for the heating test 47S as compared to the R-22 baseline. The lower
mass flow rate causes a loss of 2% in capacity, but the lower pressure
ratio causes a 3-4 % increase in COP. From this result, it can be said
that the existing unit can also be improved in terms of COP with a
small loss of capacity by soft optimization. The R-407C soft
optimization still shows degradation as compared to R-22 by 4-8 % for
the cooling and heating cases in terms of COP. But these COP results
are better than the retrofit case, by 4-8 % for the cooling mode and 15-
17 % for the heating mode in terms of COP. Also, these results agree
with the results presented by AREP (Godwin, 1993).
The temperature profiles for the R-22 and R-407C soft optimization
are shown in Figures 11 and 12. In these figures, coordinates are the
same as those of Figures 6 and 7. The temperature profiles are very
close to each other except the temperature glide of R-407C for both
modes. This suggests why soft optimization can achieve a
capacity and COP that are closer to those of R-22.
R-4G7C shows a performance degradation when retrofitting, so soft
optimization should be used. The soft optimization of R-407G shows
a steady state performance (capacity and COP) within ± 8% of the soft
optimization performance of R-22. These results are compared with
AREP test results (Godwin, 1993) in Table 6.
CONCLUSIONS
The R-22 baseline lest and the R-407C retrofit test were carried out
using ASHRAE test conditions for both cooling and heating.
"Retrofit" was defined as changing only the refrigerant and lubricant
with no equipment changes. With this definition, the retrofit tests in
this study were conducted with charge optimization only. The results
show that R-407C has a 0-3 % higher cooling capacity, a 5-9 %
lower cooling COP, a 6-21 % lower heating capacity, and a 17-24 %
lower heating COP as compared to the R-22 baseline.
The capacity and COP in the heating mode show a larger
degradation than in the cooling mode, so the heating performance
should be improved by methods such as hardware modifications or
soft optimization. Path modification is one way to improve the heat
exchange performance of mixtures by taking advantage of the
temperature glide. The advantage of this option was proven by
comparing the results with those of the retrofit. The path modification
for this study improved the heating capacity by 2-16 % and the heating
COP by 10-18% as compared to the retrofit case. It also changed the
cycle temperature profile so that it approached that of R-22.
Soft optimization, balancing cooling and heating performance,
requires significant effort to find the appropriate expansion device and
the optimum charge. Even with R-22, soft optimization can improve
the COP by 3-4 % at the expense of a 2% capacity loss, if this decrease
in capacity is acceptable. Relative to the R-22 soft optimization, the R-
407C soft optimization shows a capacity of 97-101 % and a COP of
92-96 %.
ACKNOWLEDGMENTS
The support by the Electric Power Research Institute, U.S.
Environmental Protection Agency, The Trane Company, DuPont, ICI,
Parker Hannifin Corporation, and CEEE at the University of Maryland
is gratefully acknowledged.
NOMENCLATURE
17L	Low Temperature Heating Test based on
ASHRAE Standard 116
47S	High Temp Heating Test based on
ASHRAE Standard 116
ASHRAE	American Society of Heating, Refrigerating
and Air-Conditioning Engineers, Inc.,
Atlanta, GA
ARI	Air- Conditioning and Refrigeration Institute,
Arlington, VA
AREP	Alternative Refrigerant Evaluation Program
CFCs	Chlorofluorocarbons
COP	Coefficient of Performance
G.W.P.	Global Warming Potential
HCFCs	Hydrochlorofluorocarbons
HFCs	Hydrofluorocarbons
O.D.P.	Ozone Depletion Potential
R-22	Refrigerant 22, Trifluoromethane
R-407C	Refrigerant consists of R-32/R-125/R-134a
in composition of23/25/52 wt.%
Pcond	Condensing Pressure
Pevap	Evaporating Pressure
Pressure Ratio	Ratio between Pcond and Pevi))
S.T.	Short Tube Reslrictor
Tdischarge	Compressor Discharge Temperature
T^^	Compressor Suction Temperature
REFERENCES
Air-Conditioning and Refrigeration Institute, 1989, "Unitary Air-
Conditioning and Air Source Ileat Pump Equipment," ARI Standard
210/240-1989.
American Society of Heating, Refrigerating and Air-Conditioning
Engineers, Inc., 1983, "Methods of Testing for Seasonal Efficiency of
Unitary Air-conditioners and Heat Pumps,"	ASHRAE
Standard ANSI/ASHRAE 116-1983.
Bivens, D.B., et a!., 1994, "HCFC-22 Alternative for the Air
Conditioners and Heat Pumps," ASHRAE Transactions, Vol. 100,
5

-------
Part 2, pp. 566-572.
Domanski, PA. and Didion, DA., 1993, "Thermodynamic
Evaluation of R-22 Alternative Refrigerants and Refrigerant
Mixtures," ASHRAE Transactions, Vol. 99, Part 2, pp. 636-648.
Ferrari, D., et al., 1994, "Performance Testing of R-22 and R-502
Alternatives Based on R-32/R-125/R-134a," Proceedings,
International Conference; CFCs, The Day After, Padova, Italy, pp.
223-229.
Gallagher, J., McLinden, M., and Huber, M., 1993, "REFPROP,"
NIST Thermodynamic Properties of Refrigerants and Refrigerant
Mixtures Database, Version 4.0, Thermophysics Division of National
Institutes of Standards and Technology, Gaithersburg, MD.
Godwin, D.S., 1993, "Results of Soft-Optimized System Tests in
ARTs R-22 Alternative Refrigerants Evaluation Program,"
Proceedings, The 1993 International CFC and Halon Alternatives
Conference, Washington D.C., pp. 7-12.
Radermacher, R. and Jung, D., 1991, "Theoretical Analysis of
Replacement Refrigerants for R-22 for Residential Uses," U.S.
Environmental Protection Agency Report, U.S. EPA/400/1-91/041.
Reed, J.W., 1993, "Environmental Overview: CFC and HCFC
Regulatory Update," Proceedings, The 4th IEA Heat Pump
Conference, Maastricht, The Netherlands, pp. 11-19.
Spatz, M.W. and Zheng, J., 1993, "Experimental Evaluation of
HCFC-22 Alternative in Unitary Air Conditioning Systems,"
Proceedings, The 1993 International CFC and Halon Alternatives
Conference, Washington D.C., pp. 19-24.

-------
Air Flow
Heating
Refrigerant Flo
Cooling
Heating
Cooling
FIGURE 1. INDOOR COIL HEAT EXCHANGER
CONFIGURATION
R-22 Capacity
R-22 COP
R-407C Capacity
R-4075COP
3.00 fe
(9.5 lb)
3.6
(8 .0 lb)
4.1
(9.01b)
Charge (kg)
FIGURE 3. R-22 & R-407C CHARGE VS. CAPACITY &
COP AT COOLING TEST A (1.50 mm S.T.)
AIR FLOW BALL VALVE
i SWITCH
OVER
VALVE
INDOOR
OUTDOOR
COIL
OMP
SHORT TUBE
EXPANSION 9		
VALVE
FLOW DIRECTION
-COQUNG —HEATING
- PATH MODIFICATION
HEATING
CHECK VALVE
(2 CHECK VALVE ADDED FOR PATH MODIFICATION
FIGURE 2. REFRIGERANT CIRCUIT DIAGRAM
o
3
fr.
O
u
COP
Power Input —~
Mass Flow Rate
Pressure Ratin —O
2.7 3.0 3.2 3.4 3.6 3.9 4.1 4.3
(6.0 lb) (6.5 lb) (7.0 lb) (7.5 lb) (8.0 lb)(8.5 lb) (9.0 lb) (9.5 lb)
Charge [kg]
FIGURE 4. CHARGE EFFECT ON CYCLE (R-22.
COOLING TEST A, 1.50 mm S.T.)
Evap -Inlet Evap.-!/4 Evap.-Middle Evap-3/4 Evap.-Outlet
FIGURE 5. CHARGE EFFECT ON INDOOR COIL
TEMPERATURE (R-22, 1.50 mm S.T.)
100
80
~ 60
a
|
g 40
£
20

R-22 Baseline

R-407C Retrofit

—*— R-407C Path Modification
\



CoRip. Good Cand S.T. Evap. Evap Evap. Evap. Evap- Comp,
Disch -InJet -Outlet -Inlet -Inlet -1/4 -Mid. -3/4 -Outlet -Suction
FIGURE 6. TEMPERATURE PROFILES ALONG THE
CYCLE AT COOLING TEST A
7

-------
R-22 Baseline
R-407C Retrofit
R-407C Path Modification
R-22 Capacity
R-22 COP
R-407C Capacity
R-407C COP
4.61			1	'	1 		1	'	1			1			1			1			 2.5
2.5 2.7 3.0 3.2 3.4 3.6 3.9 4.1 4.3
(5.5 lb)(6.0 lb)(6.5 lb)(7-0 lb)(7.5 lb)(8.0 lb)(8.5 lb){9.0 lb)(9 5 lb)
Charge [kg]
Comp. Good. Cond. Cond. Cond. Cond. TEV Evtp Evap. Comp.
Disch. 'Inlel -1/4 -Mid -3/4 -Outlet -Inlet -Inlet -Outlet -Suction
FIGURE 7. TEMPERATURE PROFILES ALONG THE
CYCLE AT HEATING TEST 47S
FIGURE 8. R-22 & R-407C CHARGE VS. CAPACITY &
COP AT HEATING TEST 47S
3.25
O 3.05
ST. 1.50 mm
S.T. 1.55 mm
S.T. 1.60 mm
S.T. 1.65 mm
3.0 3.2 3.4 3.6 3.9 4.1 4.3 4.5
(6 51b) (7.01b) (7.51b) (8.01b) (8.51b) (9.01b) (9.51b) (10.0 lb)
Charge [kg]
S.T. 1.55 mm
S.T. 1.60 rota
S.T. 1.65 mm
S.T. 1.70 mm
3.0 3.2 3.4 3.6 3.9 4.1 4.3 4.5
(6.5 1b) (7.01b) (7.5 lb) (8.01b) (8 5 lb) (9.0 ib) (9.5 1b) (10.01b)
Charge [kg]
FIGURE 9. R-22 CHARGE VS. COP WITH DIFFERENT
SHORT TUBE RESTRICTORS
FIGURE 10. R-407C CHARGE VS. COP WITH
DIFFERENT SHORT TUBE RESTRICTORS
R-22 Soft Optimization
R-407C Soft Optimization
V 60
8 40 -
Comp Cowl Cond. S.T. Evap. Evap. Evap. Evap Evap. Comp.
Disch. -Inlet -Outlet -Inlet -Inlet -1/4 -Mid. -3/4 -Outlet -Suction
100
£ 60
a
S 40
20
-20

» R-22 Soft Optimization
—*— R-407C Soft Optimization



Comp. Cond. Cond Cond. Cond. Cond. TEV Evap. Evap Comp.
Disch. -Inlet -1/4 -Mid. -3/4 -Outlet -Inlet -Inlet -Outlet -Suction
FIGURE 11. TEMPERATURE PROFILES ALONG THE
CYCLE AT COOLING TEST A
FIGURE 12. TEMPERATURE PROFILES ALONG THE
CYCLE AT HEATING TEST 47S
8

-------
T T-,rr-n T™j (\ a f\ TECHNICAL REPORT DATA
JN KMri L>~ K1 Jr_ i U4y (Please read Instructions on the reverse before completing/
	
1 REPORT NO. 2.
FPA/600/A-96/007
3. R6C
4. TITLE AND SUBTITLE
Evaluation of R-22 Alternatives for Heat Pumps
5. REPORT OATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Y. Hwang, J. F, Judge, and E. Radermacher
S. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Center for Environmental Energy Engineering
University of Maryland
College Park, Maryland 20742-3035
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
CR 819710-01-0
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; 9/93-12/94
14. SPONSORING AGENCY CODE
EPA/600/13
is,supplementary notes ^pp^jQ project officer is Robert V. Hendriks, Mail Drop 62B,
919/541-3928. Presented at International Mechanical Engineering Congress and
Exposition, San Francisco, CA» 11/12-17/95.
is.abstract fhg paper reports results of a study investigating three different possibili-
ties for replacing refrigerant R-22 with R-407C in a heat pump. The first and sim-
plest scenario was a retrofit without any hardware modifications, resulting in cooling
and heating capacities of 79 to 103% and coefficients of performance (COPs) of 76 to
95% of the R-22 baseline. The second possibility was a modification that required al-
tering the refrigerant path to attain a near-counterflow configuration in the indoor
coil for the heating mode; this improved the heating capacity by 2 to 16% and the heat-
ing COP by 10 to 18%, compared to the retrofit case. The third and most complex
possibility was soft optimization, consisting of maximizing the COPs in the heating
and cooling modes by optimizing the refrigerant charge and expansion devices: with
R-407C, this had a -3 to +1% different capacity and a -8 to -4% different COP in the
cooling and heating modes, compared to R-22.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. cosati Field/Group
Pollution
Heat Pumps
Refrigerants
Halohydrocarbons
Ozone
Greenhouse Effect
Pollution Control
Stationary Sources
Chlorofluorocarbons
Hydrochlorofluoro-
carbons
Global Warming
13 B
13 A
07C
07B
04 A
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)

-------