Refrigeration Oils for Future Mobile A/C Systems - R744r744.com/assets/link/FUCHS_Puhl_VDA Winter...

1VDA Winter Meeting Saalfelden 2009FUCHS Europe Schmierstoffe GmbH – C. Puhl

Refrigeration Oils forFuture Mobile A/C Systems

Christian PuhlR&D Refrigeration Oils

FUCHS EUROPE Schmierstoffe


Alternative vehicle air conditioning …

or

…using alternativerefrigerants


Low GWP refrigerant successors for R134a (GWP = 1300)

… two candidates remain:

• HFO-1234yf GWP = 3-6

Use with conventional R134a components. Only minor adjustmentsnecessary. Open questions: flammability and toxicity (HF)

• R744 (CO2) GWP = 1

high pressure level requires new components high costs.Benefits: high vol. cooling capacity, not flammable, impact on humanhealth is completely investigated, cheap

… new syntheticrefrig

eration oils

necessary !


Refrigeration oil requirements in the cooling circuit

Image: BEHR

• High refrigerant miscibility:oil transport back to the compressorheat transfer

• Stability –CO2 transcritical high temperatureHFO1234yf reactivity

• Lubricating properties• Low water content• Material compatibility (elastomers)


Refrigeration Oils for CO2Different MAC applications – different lubricant types

Bus

• Reciprocating piston compressor

Polyol ester (POE, additivated) excellent CO2 miscibility

Passenger car

• Axial piston compressor - open (belt drive)

Polylalkylene glycol compatibility with existing(new PAG, additivated) R134a oils (under investigation)

• Axial piston compressor - hermetic (hybrid / electric vehicle)

Polyol ester high electric resistance /(POE, additivated) good insulation properties


Refrigeration Oils for CO2RENISO ACC 46

refrigeration oil for open CO2 compressors forpassenger car a/c systems

• completely newly-developed PAG typeas base fluid

• chemically-modified, double-endcappedPAG ISO VG 46

• additive package for enhancedwear protection and ageing & thermalstability

• experience from car fleet tests• patent-protected formulation


Refrigeration Oils for CO2Miscibility behaviour of PAG / CO2

0 10 20 30 40 50 60concentration [mass % oil in CO2]

-50

-40

-30

-20

-10

0

10

20

30

40

tem

pera

ture

[o C]

miscible

phaseseparation

miscible

0 10 20 30 40 50concentration [mass % oil in R 134a]

-60

-40

-20

0

20

40

60

80

100

tem

pera

ture

[o C]

phaseseparation

miscibility

…compared toPAG / R134a

0 1.25 2.5 3.75 5 6.25 7.5 8.75 10Konzentration [M-% Öl in R744]

-50

-30

-10

10

30

Tem

pera

tur [

o C]

miscible

Phase separation

PAG / CO2 has restrictedmiscibility properties

But:RENISO ACC 46 is misciblein the conc. 1-3% oil in CO2

safe oil transport in passenger car a/c systems= compact systems

Miscibility diagram (miscibility gap) PAG / CO2

Miscibility diagram ofRENISO ACC 46 / CO2


Refrigeration Oils for CO2Thermal stability

Standard test conditions: storing at

220°C / 2 weeks / 50 bar CO2

Oil analysis in order to detect a decomposition which is indicatedby a change in

• neutralization number

• viscosity

• chemical structure (IR analysis)

Only special PAG / POE derivatives fulfill therequirementsConventional R134a-PAG are not useful


+ 1,48

+ 0,47

8,2 %

0,6 %

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

conventional R134a PAG RENISO ACC 46(PAG for CO2)

incr

ease

neu

traliz

atio

n no

. / T

AN

[mg

KO

H/g

]

0

1

2

3

4

5

6

7

8

9

decr

ease

vis

cosi

ty @

40°

C [%

]increase neutralization no.

decrease viscosity @ 40°C

c(H2O) < 100 ppm

less ageing withRENISO ACC 46

Refrigeration Oils for CO2Thermal stability – oil after ageing: 2 weeks / 220°C / 50bar CO2


Bearing fatigue lifetime test with axial rollerbearings (AXK 18x35) under 50 barCO2 pressure

testing of different refrigeration oilformulations

the longer the bearing lifetime the betterthe wear protection of the tested oil

Refrigeration Oils for CO2Lubrication properties - CO2 high-pressure bearing test rig


37

75

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

80,0

90,0

100,0

conventional R134a PAG RENISO ACC 46(PAG for CO2)

Lh10

a be

arin

g lif

etim

e [h

]

RENISO ACC 46 doublesthe bearing lifetime

Test conditions: 140°C / 50 bar CO2 / axial load 8 kN / 800 min-1

Refrigeration Oils for CO2Lubrication properties - CO2 high-pressure bearing test rig


Mixed friction: Lubricating film is torn apart

contact of roughness peaksno fluid friction (no hydro-dynamics)impact: wear

causes:• high oil dilution with CO2• high loads in the bearing• high temperature in lubricating gap• on / off mode

Antiwear additives form protective reaction layer on the surfaceProtection against wear

metal surface

Metalloberfläche

oill

metal surface

MHydrodynamiketalloberfläche

oil

Mixed friction

Hydro-dynamics

Refrigeration Oils for CO2Lubrication properties – function of anti wear additives


Refrigeration Oils for HFO-1234yf:Requirements & solution

Oil requirements:

Good refrigerant miscibility propertiesReliable lubrication propertiesHigh stability in combination with HFO-1234yf

Oil solution: POE or PAG …?

R

chem. structure PAG chem. structure POE


PAG / HFO 1234yf has inferior miscibility behaviour compared to PAG / R134aSpecial PAG structures are miscibile with HFO-1234yf up to 30°C, POE up to 67°CIs the performance of PAG sufficient for the situation in the condenser ?

0 10 20 30 40 50 60concentration [mass% oil in R 1234yf]

-60

-45

-30

-15

0

15

30

45

60

75

90

tem

pera

ture

[o C]

Refrigeration Oils for HFO-1234yf:Miscibility Behaviour

complete miscibility

phaseseparation

Fuchs-PAG ISO VG 46

0 10 20 30 40 50 60concentration [mass% oil in R 1234yf]

-60

-45

-30

-15

0

15

30

45

60

75

90

tem

pera

ture

[o C]

phaseseparation


Fuchs-POE ISO VG 80

0 10 20 30 40 50concentration [mass % oil in R 134a]

-60

-40

-20

0

20

40

60

80

100

tem

pera

ture

[o C]

phaseseparation


…compared toPAG / R134a


Water content [ppm]PAG

base oilPAGadd.

POEadd.

0,50 0,360,95 0,60

POEbase oil

dry - PAG <250 ppm / POE <50 ppm 0,28 < 0,1wet - PAG 800 ppm / POE 300 ppm 0,48 < 0,1

Sealed Tube Test acc. ASHRAE 97/1999Test conditions:30% HFO-1234yf / 70% oil / 175°C / 500h / Fe + Al + Cu metal coupons

Comparison:FUCHS base fluid additivated products

Increase in Neutralisation No. (Total Acid Number)in mgKOH/g (fresh oils: < 0,1)

Refrigeration Oils for HFO-1234yf:Chemical Stability

Comparison:

conventionalPAG / R134

< 0,1

0,5

FUCHS additivation:• stabilizer system• anti wear additive

Additivation reduces the TAN significantlyPOE exhibits lower acid values: higher stability


Refrigeration Oils for Future Mobile A/C Systems:Conclusion

• CO2:The necessary requirements for the refrigeration oil - adequaterefrigerant miscibility, high thermal stability and enhanced wear protection (at mixed friction conditions) – can be fulfilled with newly developed PAG-based refrigeration oils that contain an effective antiwear and antioxidant additive system.

• HFO-1234yf:PAG and POE lubricants exhibit different refrigerant miscibilitybehaviour. POE has a smaller miscility gap than PAG. The chemicalstability of both systems POE and PAG can be improved bychoosing a suitable stabilizing additivation of the refrigeration oil.The lubrication properties of PAG / HFO-12234yf are currently underinvestigation.


Thank you for your attention !

Questions welcome …!

POE? PAG?Miscibility gap? ...?


Refrigeration Oils for CO2RENISO ACC 46

pVT diagram (Daniel Plot):RENISO ACC 46 / CO2

Refrigeration Oils for Future Mobile A/C Systems - R744r744.com/assets/link/FUCHS_Puhl_VDA Winter...

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