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

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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%

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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

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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

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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.

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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

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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

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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 !

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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

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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

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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.

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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

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www.refrigerants.dupont.com

Special Acknowledgement for data and permission from: Hiroichi Yamaguchi, Toshiba Carrier Corporation

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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

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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

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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

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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

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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