Post on 15-Mar-2018
Low GWP Refrigerants for Stationary AC and Refrigeration
Thomas J Leck, Frank Rinne, Kostas Kontomaris,DuPont Company
Sustainable Refrigeration and Heat Pump TechnologyKTH Stockholm, 15 June 2010
2
Outline
Introduction - The need for New Refrigerants
HFO-1234yf Properties, Flammability
Refrigerant Blends
Model and Experimentally Measured Results
AC, Heating, Refrigeration, Chillers
Conclusions
3
Commercial Refrigerant Examples Many types necessary to meet diverse cooling needs
Refrigerant Primary Use Normal B.P.
Comment
CO2 Low Temp -78 ºC Low critical temperature. Requires expander for AC
Ammonia Industrial Freezing
Ice Making
-33 ºC Toxic
Mildly flammable
Safety MeasuresHFC-134a
HFC-410A
HFC-404A
General Refrigeration, Air Conditioning
-26 ºC
-51 ºC
-46 ºC
High Global Climate Impact Potential
Isobutane
Propane
Domestic Refrigeration Industrial
-12 ºC
- 42 ºC
Explosive – Must limit charge size, or use industrial safety controls
HCFC-123 Large Tonnage Centrifugal
28 ºC Mild Toxicity
ODS
4
HFO-1234yf R-134aBoiling Point, Tb -29ºC -26ºCMolecular Weight 114 102Formula CF3CF=CH2 CH2FCF3Global Warming Potential 4 1430
REFPROP EquationOf State available
00.51
1.52
2.5
33.5
-40 -20 0 20 40 60 80 100
R-134a
HFO-1234yf
Pres
sure
(MPa
)HFO-1234yf Properties
Temperature, degrees C
Vapor Pressure
5
HFO-1234yf - Excellent Environmental Properties
ODP = 0; GWP100 = 4
Atmospheric lifetime = 11 days
Atmospheric chemistry measured• Atmospheric breakdown products same as for 134a
• No high GWP breakdown products
Good LCCP for Mobile AC
Now accepted as global standard for car AC systems, to meet F-gas regulations
HFO-1234yf Environmental Properties Established and Peer Reviewed
Chemical Physics Letters
439 (2007) pp 18-22
450 (2008) pp 263-267
6
HFO-1234yf Flammability
aFlame limits measured at 21 oC, ASTM 681-01bTests run in 12 liter flask to minimize wall quenching effects cHFO-1234yf BV measured by AIST, Japan
Mildly Flammable – “2L”
LFLa
vol%
UFLa
vol%(UFL- LFL)
vol%
MIE
mJ
HOC
kJ/gBV
cm/s
Propane 2.2 10.0 7.8 0.25 46.3 46
R152a 3.9 16.9 13.0 0.38 16.5 23
R32 14.4 29.3 14.9 30-100b 9.4 6.7
Ammonia 15.0 28.0 13.0 100-300b 18.6 7.2
HFO-1234yf 6.2 12.3 6.1 5,000- 10,000b
10.7 1.5c
7
HFO-1234yf HFC-134a
HFO-1234yf Thermal Stability
HFC-134aHFO-1234yfNo Detectable Fluoride nor Acid Generation
Thermal Stability and POE Miscibility comparable to R-134a
HFO-1234yf/POE vs HFC-134a/POEAFTER TWO
WEEKS @ 175 °C
Front View Side View
8
Compatibility with System Materials
Metals – No corrosion of common metals - Fe, Cu, AlNo catalytic or reactive behavior from metals
Lubricants - Solubility patterns similar to that of R-134aVery low mutual solubility in MO, non polar lubricantsModerate solubility in polar lubricants - PAG and POE
Plastics and Elastomers – degree of interaction very similar to that of conventional HFC refrigerants like R-134a
- Absorption in to polymer- Softening, weight gain, volumetric swell
No changes in materials appear to be necessary
9
HFO-1234yf at AC Conditions Thermodynamic Cycle Model Results:Evaporator Temp: 7 ºC Condenser Temp: 47 ºC
Liquid Refrigerant Subcool : 12 K
Suction Gas Superheat 3 K Suction Temperature 10 ºC
Refrigerant GWP
IPCC AR4
Flammable ?
COP Capacity
kJ/m3
R-410A 2088 No 4.04 6225
R-22 1810 No 4.299 4300
R-407C 1774 No 4.225 4371
R-134a 1430 No 4.378 2816
HFO-1234yf 4 Yes 4.267 2667
Can use mixtures to create higher performance, low GWP replacements
10
Formulation of Refrigerant Mixtures: Desired Properties, Trade-Offs
Select Components with Desired Properties• Refrigeration Performance
• Energy Efficiency (COP) – Relates to Energy Usage• Capacity
• Flammability – at ASHRAE or ISO Conditions• GWP• Azeotropes or Blends with Similar Boiling Points
• Minimum Temperature Glide
• Work in Existing Equipment Designs• Match Pressure Characteristics of Existing Refrigerant
Capacity vs GWP - AC Cycle7 C Evap, 47 C Cond, 12 K Subcool, 3 K Super Heat
30%
40%
50%
60%
70%
80%
90%
100%
110%
120%
0 500 1000 1500 2000
GWP Value
Cap
acity
vs.
R-4
10A
R-410A, 0.1G
R-32
DR-5, 1G
DR-4, 5G
DR-6, 3G
DR-3, 7G
DR-9, 4G
DR-11, 0 G
R-407C, 4.8 GR-22
R-134a
HFO-1234yf
COP vs 410A
0 to +1%+3 to +6%
+6 to +8%
R-134a
R-410A
HFO-1234yf
Mildly Flammable Non FlammableG = Glide, K
R-22R-407C
R-32
0 G
4 GCOP vs 410A
+0.5 to +1.5%+2 to +3%+3 to +5%+5 to +6%
0 %DR-11
DR-5, G1DR-6, G3
DR-9DR-3 7G
DR-4, 4G
13
Medium Temp Comparisons -10C Evaporator, 40C Condensing Reduced GWP Candidates Capacity Relative to R404A
40%
60%
80%
100%
120%
140%
160%
0 500 1000 1500 2000 2500 3000 3500 4000 4500GWP
% o
f R40
4A C
apac
ity
R-32
DR-7, 6G
DR-3, 7G
DR-8, 5G
HFO-1234yf
DR-11, 0G R-134a
R-407C, 5G
R-22
R-404A
DR-9, 4GCOP vs R404A -3% 0% +3 to +5% +7% to +8%
14
HFO-1234yf AC “Drop In” Test
High End Inverter type R-410A AC/Heat Pump Ductless Split
Rated Capacity (R-410A) Cooling: 2.8 kW, Heat 3.2 kW
Testing at JRAIA Standard Conditions
Rated Condition Cooling and Heating COP were very low, as expected
Intermediate Load Condition: Performance Better than expected
Design Modifications can improve performance:
Reduce pressure drop
Increase mass flow rate
Overall energy performance not as good as R-410A
15
HFO-1234yf Drop In Results Analysis:
LCCP Life Cycle Climate Performance
Assumption: 70 % of refrigerant charge eventually lost,
(based on Japanese survey data for mini-split units)
Direct emissions out weigh energy use for R-410A LCCP
LCCP for HFO-1234yf benefits from low GWP value
APF Annual Performance Factor
= AC and Heating loads / annual electric power consumption
Comprehensive month by month calculation using standardized operating conditions
16
Evaluation of HFO-1234yf in R-410A Heat Pump
48
62
80
9586 88
93
7971
8189 88
0102030405060708090
100
COPCooling
COPHeating
APF LCCP
% v
s R41
0A
HFO-1234yfDrop In
HFO-1234yfModified PD
HFO-1234yf Modified Comp.
17
Modeled Cycle COP and CapacityAC and Heating Conditions
99 101
82 81
99 101 100 100
0
20
40
60
80
100
120
COP Cooling COP Heating CapacityCooling
CapacityHeating
% v
s. R
410A
DR-4
DR-5
Model Results Predict that DR-5 is best match for R-410A
18
Measured System PerformanceStraight "Drop In" Testing
9097 97
79
104 101 103
76
0
20
40
60
80
100
120
COP Cooling COP Heating APF LCCP
% R
elat
ive
to R
410A
DR-4
DR-5
“Drop In” test using residential R-410A AC/Heat Pump
19
Drop In Test Observations:HFO-1234yf (GWP = 4, Glide = 0)
COP Cooling and Heating, 55 % of R-410ALCCP 89 % of R-410A
DR-4 (GWP ~ 300, Glide ~ 5 K) results:COP Cooling and Heating, 90 % and 97 % of R410AAPF 97 % of R-410ALCCP 21 % better than R-410A
DR-5 (GWP ~ 500, Glide < 1 K) results:COP Cooling and Heating, 104 % and 101 % of R-410AAPF 103 % of R-410ALCCP 24 % better than R-410A
The Lower GWP Fluids HFO-1234yf and DR-4 show Energy and Environmental performance NOT AS GOOD AS DR-5 !
20
Centrifugal Water Chillers
Previous centrifugal chiller refrigerants and transitions
CFC-11HCFC-123 CFC-12HFC-134a
Number ofCentrifugal Chillers in
Operationaround the world:
Over 130,000
Total Refrigerant Bank:ca. 60,000 tonnes
Evaporator
Condenser
Expansion
Valve
High Pressure Refrigerant Gas
Low Pressure Refrigerant Gas
Centrifugal Compressor
Electricity
Water
Chilled Water
To Building
Focus Today
21
Centrifugal Chiller Efficiency – Capacity Trade-Offs
Teva = 4.4 [oC]; Tcond = 37.8 [oC]; Tsubc = 0 [oC]; Tsuperh = 0 [oC]; P=0 [Pa]
0.95
0.96
0.97
0.98
0.99
1.00
1.01
1.02
0.93 0.94 0.95 0.96 0.97 0.98 0.99 1.00 1.01 1.02Vol Cooling Capacity Realtive to HFC-134a
CO
P R
elat
ive
to H
FC-1
34a
HFC-134aCFC-12
DR-11
HFC-1234yf
Vol Cooling Capacity Relative to HFC-134a
CO
P R
elat
ive
to H
FC-1
34a
22
Conclusions & Observations:• HFO-1234yf has been shown to be a safe, effective refrigerant for
environmentally sustainable solutions for MAC applications.• HFO-1234yf has excellent potential to replace R-134a for HVACR
applications where mild flammability can be managed. • HFO-1234yf is not a replacement for fluids like R-410A, R-404A• We have developed reduced GWP blends with good capacity and COP that
may be useful in R-134a, R-22, R-410A or R-404A applications• There are trade-offs of GWP, Flammability, Performance, and Glide.• Regulatory uncertainty causes uncertainty since regulations will impact
final product selection and timing.• We suggest that regulatory structures not be based solely on a GWP cap,
but instead consider energy efficiency, capacity and other performance related issues so that the best environmental solutions can be applied.
• Flammability issues must be assessed for safety codes in residential and commercial buildings before this new generation of refrigerants can be fully implemented.
23
Containment is CriticalNo refrigerant , while sealed in a cylinder, or in a system can cause environmental damage. Or cause fires, or cause other harm.
Proper stewardship of the refrigerant is at least as important as the choice of refrigerant to be used.
There is a need for enforceable protocols, or meaningful incentives for recovery, recycle, and end of life disposition of equipment and refrigerant gases.
Our industry must do much better than it has in the past
24
www.refrigerants.dupont.com
Special Acknowledgement for data and permission from: Hiroichi Yamaguchi, Toshiba Carrier Corporation
26
HFO-1234yf and DR-11: Basic properties
Property CFC-12 HFC-134a HFO-1234yf DR-11Chemical Formula
CCl2 F2 CH2 F-CF3 CF3 CF=CH2 Azeotrope
Safety Class(ASHRAE Std 34)
A1 A1 A2L A1(expected)
ODP 1.00 0.00 0.00 0.00GWP100 10,890 1430 4 <600
Tcr [oC] 112.0 101.1 94.7 97.5Pcr [MPa] 4.14 4.06 3.38 3.82
Tb [oC] -29.8 -26.1 -29.5 -29.2Chiller Glide [oC] N/A N/A N/A No greater
than 0.01
27
HFO-1234yf and DR-11: Vapor Pressure
0
500
1000
1500
2000
2500
-20 -10 0 10 20 30 40 50 60 70Temp [oC]
Pres
sure
[kPa
]
DR-11
CFC-12
HFO-1234yf
HFC-134a
28
HFO-1234yf and DR-11: Compatibility with POE Lubricants, Plastics and Elastomers
HFO-1234yf/POE and DR-11/POE blends:
Miscible over range of chiller conditions
Stable with metals at 175 oC for 2 weeks
HFO-1234yf and DR-11 with
Polymers and Elastomers:
Degree of interaction comparable to HFC-134a
29
Summary: HFC-134a Replacements
Next:Full Scale Chiller Testing, LCCP Analysis, Risk Assessment,
Guidelines for Safe Use, Standards & Codes Revisions
KEY: Flexible climate protection regulations Acceptance of optimum refrigerants
Two promising low GWP candidatesto replace HFC-134a in centrifugal chillers:
GWP100 FLAMMABILITYHFO-1234yf 4 2LDR-11 <600 Nonflammable
30
Compatibility with Plastics% weight change after 2 wks @ 100ºC in HFO-1234yf vs HFC-134a
Polymer 0 Hrs 0 Hrs 24 Hrs 24 Hrs
HFC-134a HFO-1234yf HFC-134a HFO-1234yfPolyester Resin 7.6 4.2 2.2 2.3Nylon Resin 0.3 -0.2 -0.5 -0.4Epoxy Resin 0.1 -0.1 -0.3 -0.1Polyester PET 9.3 5.3 5.8 3.8Polyester PBT 12.5 1.1 12.3 1.1Polycarbonate 4.2 0.9 3.9 0.8Polyimide 3.7 3.4 3.2 3.2Polyethylene 1.3 1.7 1.1 1.3PTFE 2.7 3.0 2.3 2.4FEP 3.1 3.8 2.7 3.2ETFE 6.0 4.9 4.8 4.2Phenolic Resin -0.8 -0.8 -1.0 -0.8Acetal Resin 2.7 0.7 2.1 0.6PET Film 0.8 -1.0 -1.3 -2.1
Immediately after exposure 24 Hrs after exposure
31
Compatibility with Elastomers
Elastomer 0 Hrs 0 Hrs 24 Hrs 24 Hrs
HFC-134a HFO-1234yf HFC-134a HFO-1234yfNeoprene WRT 2.6 2.4 1.3 1.3HNBR 15.2 5.2 9.9 4.4NBR 14.1 5.8 8.0 4.6EPDM (Nordel) 3.6 3.5 0.7 0.6Silicone 10.6 2.0 -0.1 -0.4Butyl Rubber 4.1 5.0 3.2 4.1Terminal seal 2.2 4.8 0.8 2.0Buna S (SBR) 2.7 2.1 1.1 0.8Viton 47.4 20.0 8.0 8.0Hypalon 3.2 2.7 2.6 2.4Neoprene o-ring -0.4 3.0 -0.5 2.3
Immediately after exposure 24 Hrs after exposure
% weight change after 2 wks @ 100ºC in HFO-1234yf vs HFC-134a
Overall: Comparable degree of interaction of polymers & elastomers with 1234yf and 134a