The document discusses testing of low global warming potential (GWP) refrigerant alternatives to replace R-404A in commercial refrigeration systems. Two alternatives, DR-7 and DR-33, were tested in a reach-in freezer and a display case with an external condensing unit. DR-7 has a GWP of 246 and is suitable for smaller systems, while DR-33 has a GWP of 1410 and is suitable for all system types. Testing found that both alternatives provided equivalent or improved energy efficiency compared to R-404A, with comparable operating pressures and temperatures. The alternatives show potential as low-GWP replacements for R-404A in commercial refrigeration applications.

1. Testing of Low GWP R-404A
Alternatives in Commercial
Refrigeration Systems
Barbara H. Minor & Joachim Gerstel
DuPont Fluorochemicals
Milano, 7th-8th June 2013

2. Topics
 Regulatory Environment
 Properties of New Refrigerants
 Thermodynamic Cycle Performance
 Drop-in System Testing
Reach-in Freezer
Display Case/Condensing Unit
 Summary
2

3. Growing regulatory pressure on HFCs
 EU – F-Gas directive has GWP cap of 150 in new vehicle
model a/c systems beginning January 1, 2011; HFC-134a no
longer allowed
 EU – EU Commission proposed revisions to F-Gas regulation
regarding stationary requirements
 Australia – Instituted carbon tax starting July, 2012
 Global – Potential for HFC phase-down under the Montreal
Protocol framework (cap and allocation)
 R-404A is a leading target for replacement as it has one of
the highest GWPs for HFCs (100 yr 3922 - AR4)

4. New low GWP Alternatives for R-404A
 DR-7 2L Mildly Flammable GWP = 246
 HFC-32/HFO-1234yf at 36/64 wt%
 94% lower GWP than R-404A
 Suitable for smaller charge R-404A systems due to charge
size restrictions in EU codes and standards
 DR-33 Nonflammable GWP = 1410
 32/125/134a/1234yf at 24/25/26/25 wt%
 65% lower GWP than R-404A
 For all R-404A systems, including larger systems if
nonflammability is required
 Potential for retrofit of existing R-404A systems

5. Refrigerant Properties
R-404A DR-7 DR-33
100 yr GWP 3922 246 1410
Flammability None 2L None
Boiling Point °C -47 -48 -46
Critical Point °C 72 81 82
Vapor Pressure at
25°C in kPa
1254 1372 1271
Liquid Density at
25°C in kg/m³
1044 1133 1139
Vapor Density at
25°C in kg/m³
65,3 46,8 48,9

6. Evaporator temperature = -26ºC, Condenser temperature = 43ºC,
Subcool amount = 14K, Suction temperature = -4ºC,
Compressor isentropic efficiency = 75%.
Suct
Press
kPa
Disch
Press
kPa
Comp
Ratio
Compress
Disch
Temp °C
Average
Temp
Glide K
Cap
Rel to
404A
COP
Rel to
404A
R-404A 242 1969 8,1 86 0,4 100% 100%
DR-7 230 1987 8,6 107 5,7 103% 101%
DR-33 207 1869 9,0 103 4,3 95% 102%
Thermodynamic Cycle Performance
DR-7 and DR-33 have comparable capacity and
energy efficiency compared to R-404A

7. System Testing – Two Door Reach-in Freezer
- 1,5 m³ double-door unit designed for R-
404A
- Reciprocating two piston compressor
- Refrigerant charge size 1,15 kg,
adjusted based on liquid density
- Polyol ester (POE) 32 centistokes
lubricant
-Tested per AHAM Standard HRF-1-2008
-Tested at three ambient temps: 32ºC,
24ºC and 21ºC
- Average freezer compartment temp
controlled at -17ºC, average evaporator
temp -28ºC

8. Reach-In Freezer Schematic
- no equipment changes for candidate testing, except TXV closed one turn

9. Reach-In Freezer Test Results
Energy
Cons
Rel to
R-404A
Mass
Flow
Rate
(kg/h)
Suct
Press
(kPa)
Disch
Press
(kPa)
Comp
Ratio
Comp Disch
Temp (ºC)
Ambient t = 32ºC
R-404A 100% 44 211 2027 10 90
DR-7 92% 34 191 2133 11 105
DR-33 96% 30 172 1931 11 104
Ambient t = 24ºC
R-404A 100% 46 198 1647 8 75
DR-7 95% 35 184 1728 9 91
DR-33 100% 31 172 1551 9 88
Ambient t = 21ºC
R-404A 100% 48 199 1558 8 70
DR-7 97% 36 179 1600 9 85
DR-33 100% 33 172 1448 8 83
 equivalent to slightly reduced energy consumption
 comparable pressures and compression ratio
 modest increase in discharge t and lower mass flow rate

10. System Testing – Display Case with External Condensing Unit
 2,5 m open food display case designed
for R-404A, fully loaded with food
simulator
 Reciprocating compressor with POE 32
oil
 Refrigerant charge size ~3,8 kg,
adjusted based on liquid density
 Tested per ASHRAE Standard 72-2005
 Tested at two ambient temps: 28ºC and
35ºC in outdoor room, 24ºC in indoor
room
 Only minor TXV adjustment made (1,6
turns closed)
 Tested at low and medium temp
conditions
Open Display Case in Indoor Room
Condensing Unit in Outdoor Room

11. CONDENSING UNIT AND DISPLAY CASE LAYOUT
OUTDOOR ROOM INDOOR ROOM
Evap
Pressure
Regulator
T, P =
TEMP.
AND
PRESS
TAPS
Suction LineLiquid Line
Insulated
Suction-Liquid
Heat Exchange
ENVIRONMENTAL
CHAMBER
Mass Flow
To Discharge Line
P
T
PsP
T T T
P
T
Frozen Food CaseCondensing Unit
T Ts
Pd TdkW
28ºC or 35ºC 24ºC

12. Condensing Unit/Display Case Low Temp Results
Energy
Cons
Rel to
R404A
Mass
Flow
Rate
kg/h
Suct
Press
kPa
Disch
Press
kPa
Comp
Ratio
Avg
Food
Temp
ºC
Comp
Disch
Temp
ºC
Ambient
t = 28ºC
R-404A 100% 32 112 1438 13 -17 78
DR-33 97% 26 104 1407 14 -17 83
Ambient
t = 35ºC
R-404A 100% 33 127 1722 14 -16 87
DR-33 96% 26 115 1685 15 -15 92
 ~3% lower energy consumption
 Similar pressures and compression ratio
 Modest increase in discharge t and slightly lower mass flow rate

13. Condensing Unit/Display Case Med Temp Results
Energy
Cons
Rel to
R404A
Mass
Flow
Rate
kg/h
Suct
Press
kPa
Disch
Press
kPa
Comp
Ratio
Avg
Food
Temp
ºC
Comp
Disch
Temp
ºC
Ambient
t = 28ºC
R-404A 100% 38 262 1544 5,9 2,2 72
DR-33 92% 32 262 1496 5,7 2,2 75
Ambient
t = 35ºC
R-404A 100% 41 248 1827 7,4 2,2 82
DR-33 88% 34 283 1792 6,3 2,8 84
 8-12% lower energy consumption
 Similar pressures and compression ratio
 Less increase in discharge t and slightly lower mass flow rate

14. Summary
 New low GWP refrigerants for R-404A under development
 DR-7 has a GWP of 246, is mildly flammable (2L) and suitable
for single condensing unit systems, stand-alone coolers and
freezers.
 DR-33 has a GWP of 1410, non-flammable and suitable for all
R-404A systems, including large racks and potential retrofit of
existing R-404A units.
 Both refrigerants are thermally stable in presence of air and water and
are miscible with POE lubricants.
 Energy consumption in reach-in freezer and condensing unit tests are
comparable or improved versus R-404A while other performance
parameters are similar.

15. Thank you!
Email: joachim.gerstel@dupont.com
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