A/C System Control Strategies for Major Refrigerant … System Control Strategies for Major Refrigerant Options J.Benouali, ... ARSS Phoenix presentation ... Evaporator 6 passes 5,3

A/C System ControlStrategies for MajorRefrigerant OptionsJ.Benouali, S.Karl, C.Petitjean

Final – June 11th, 2008

June 11th, 2008 I 2 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean

IntroductionAR selection and then ?

10 years to come to AR selection

10 years ago: 1st Phoenix meeting

5 years ago: 1st draft of the EU F-Gas regulation

1 year ago: HFO 1234-yf becomes the challenger of R744

0,5 year ago: EU commission proposal to have a regulationincluding “Minimum Efficiency requirements for MAC”

After AR option(s) selection due to direct emission issuesEnergy efficiency is the main challenge


Agenda: major parts of the presentation

Referenced Test Results for 3 refrigerants- A/C system at bench

- In cars at Climatic Wind Tunnel

- LCCP analysis

A/C system control strategies and results- Methodology for torque estimation

- Results for sub-critical refrigerants (R134a & 1234-yf)

- Results for super-critical refrigerant (R744)

- Conclusion

1

2

3


Tested A/C system architectures

Integrated IHX Accumulator(510 cc)Integrated IHX Accumulator(510 cc)IHX

Pressure sensor (condenser outlet)Evaporator Air Temperature sensor

P/T sensorEvaporator Air Temperature sensorSensors

14,4 kg14,5 kgSystem weight

110mm110mmPulley

Accumulator

New back pressure expansion valveFixed orifice + by passExpansion valve

6passes, 5,3 dm2 (38mm width)6 passes 5,3 dm2 (38 mm width)Evaporator

25 dm2, 16mm width25 dm2, 16 mm widthGas cooler

Optimized 28cc Externally controlled28cc externally controlledCompressor

Enhanced R-744 systemR744 A/C system



Sensors

12,7 kg12,4 kgSystem weight

110mm110mmPulley

Thermostatic expansion valve (new settings)Thermostatic expansion valveExpansion valve

New 6passes (counter flow) , 5,3 dm2 (48mm width)6passes (U-bends), 5,3 dm2 (60mm width)Evaporator

23,5dm2, 16mm width + integrated receiver dryer23,5dm2, 16mm width + integrated receiver dryerGas cooler

High efficiency IHXNoneIHX

171cc Externally controlled171cc Externally controlledCompressor

Enhanced R134a & HFO 1234yf A/C systemR134a & HFO 1234yf A/C system


Test bench facilities

Valeo system test bench is fully instrumented

Acceptance criteria for testing point is ± 5% the air side cooling capacity is measured with amixing chamber and compared to the refrigerant


Method and test conditions at bench

Valeo Standard test conditions

HVAC position MAEI (kg/h) TAEI (°C) HRAEI (°C) MAGI (kg/h) TAGI (°C) N (rpm) TAEO (°C)

Sizing 45 Fresh air 540 45 40 2300 45 1850 MinIDLE 45 Fresh air 540 45 40 1300 45 1000 MinIDLE 40 Fresh air 520 40 40 1000 40 1000 MinIH 45_35 Recirculation 465 35 30 1500 45 1500 8 or minIH 35 Fresh air 540 35 40 1500 35 1500 8 or min

IH 35_25 Recirculation 465 25 40 1600 35 1600 9IH 30 Fresh air 520 30 40 1600 30 1600 12IH 25 Fresh air 260 25 55 1600 25 1600 8IH 20 Fresh air 260 20 70 1600 20 1600 8IH 15 Fresh air 180 15 90 1600 15 1600 8

CD1 Recirculation 540 46,5 15,5 2300 46 2500 MinCD2 Recirculation 540 37 17 2300 46 2500 MinCD3 Recirculation 540 28 24 2300 46 2500 MinCD4 Recirculation 540 30 30 1600 46 1000 Min

High thermal loads

Average and low thermal loads

Cool down

All the A/C systems are tested and compared with: The same test bench

The same test matrix


Result at high thermal load:explore the limitsConditions

Cooling capacity - High thermal test points

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

8000

8500

9000

Sizing 45 IDLE 45 IDLE 40 IH 45_35 IH 35

Co

oli

ng

ca

pa

cit

y(W

)

R-134a baseline R-134a enhanced

R-744 baseline R-744 enhanced

HFO-1234yf baseline HFO-1234yf enhanced

Conclusions

High load test points are the most severeconditions applied to the system in order to checkthe maximum cooling capacity:

- Sizing & Idle 45 : 45°C and 40% RH (fresh air)

- IDLE 40 : 45°C and 40% RH (fresh air)

- IH45_35 (8°C/min) : 45°C (recirculation 35°C, 30%)

- IH35 (8°C/min) : 35°C and 40% RH (fresh air)

- R134a remains the most efficient for high loadsconditions

- R744 & 1234-yf w/o IHX show limitation in coolingcapacity in severe idle conditions

- For specific high load countries the use of anautomatic recirculation HVAC function isrecommended with R744 & 1234-yf w/o IHX

COP - High cooling capacity test points

0,00

0,25

0,50

0,75

1,00

1,25

1,50

1,75

2,00

2,25

2,50

2,75

3,00

3,25

3,50

Sizing 45 IDLE 45 IDLE 40 IH 45_35 IH 35

CO

P(-

)





Result at medium & low thermal loadsQualify the energy efficiencyConditions

Average and low thermal loads - Cooling capacity

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

2750

3000

3250

3500

IH 35_25 IH 30 IH 25 IH 20 IH 15

Co

olin

gc

ap

acit

y(W

)




Conclusions

IH test points have been selected in order toevaluate the A/C loop efficiency according to theWest European Climate test matrix.

The A/C loop control the blown air temperaturebetween 8°C and 12°C (depending on the testconditions).

The A/C loop is always in capacity reduction so thecooling capacity is the same whatever therefrigerant.

- R744 becomes more efficient as far as the thermalload is reducing

- Calculated average values for EU climate showsthat both systems are close in terms of efficiencywith an advantage (6-9%) for R744 in thisapplication

Average and low thermal loads - COP

0,000,250,500,751,001,251,501,752,002,252,502,753,003,253,503,754,004,254,504,755,00

IH 35_25 IH 30 IH 25 IH 20 IH 15

CO

P(-

)





Results on cool down test pointsCorrelate bench and car testsConditions

Cool down test points - Cooling capacity

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

CD 1 CD 2 CD 3 CD 4

Co

olin

gcap

acit

y(W

)




Conclusions

Cool down test points have been defined in order tosimulate the A/C loop behavior during the cooldown procedure:

-CD1 : conditions after 3’ (40 km/h III gear phase)



-CD4 : conditions after 60’ (IDLE phase)

- R744 can bring a better cool-down than 1234-yf

- But this better cool-down leads to a slightly lowerefficiency

Cool down test points - COP

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

1,60

1,80

2,00

2,20

2,40

2,60

CD 1 CD 2 CD 3 CD 4

CO

P(-

)





In car results: Test in CWT (R-134a and HFO-1234yf)

Additional configurations under tests: 171cc compressor + w & w/o IHX + new condenser

L V W in d tu n n e l te s ts - V a le o c o o l d o w n R 1 3 4 a v s . H F O 1 2 3 4 y fA m b ie n t a ir c o n d it io n s 4 5 °C & 4 0 % R H (re c irc u la tio n )

0

5

1 0

1 5

2 0

2 5

3 0

3 5

4 0

4 5

5 0

5 5

6 0

0 3 0 0 6 0 0 9 0 0 1 2 0 0 1 5 0 0 1 8 0 0 2 1 0 0 2 4 0 0 2 7 0 0 3 0 0 0 3 3 0 0 3 6 0 0 3 9 0 0 4 2 0 0 4 5 0 0 4 8 0 0T im e (s )

Tem

pe

ratu

re(°

C)

B a s e l in e V e n t O u tle t T °C b a s e lin e F ro n t H e a d T °C

IH X V e n t O u t le t IH X F ro n t H e a d

V e n t o u tle t 1 2 3 4 y f F ro n t h e a d 1 2 3 4 y f

4 0 k m /h - II I g e a r Id le -N 9 0 k m /h - V g e a r

V e n t o u t le t = 6 ,7 °C

V e n t o u t le t = 1 5 ,7 °C

V e n t o u t le t = 1 0 ,9 °C

R 1 3 4 a b a s e lin e 1 7 1 c c

V e n t o u tle t = 8 ,3 °C

V e n t o u t le t = 1 6 ,3 °C

C p r 1 4 0 c c + IH X - R -1 3 4 a

C p r 1 4 0 c c + IH X - 1 2 3 4 y f

R -1 3 4 a R -1 3 4 a

V e n t o u t le t = 1 7 ,0 °C

1 .4 l ite r g a s o lin e e n g in e


In car results: Test in CWT (R-744)

Wind tunnel tests - Valeo cool down R-134a baseline vs. R-744Ambient air conditions 45°C & 40%RH (recirculation)

0,0

2,5

5,0

7,5

10,0

12,5

15,0

17,5

20,0

22,5

25,0

27,5

30,0

32,5

35,0

37,5

40,0

42,5

45,0

47,5

50,0

52,5

55,0

57,5

0 300 600 900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500 4800

Time (s)

Tem

pe

ratu

re(°

C)

Breath level R-134a baseline Vents outlet- R-134a baseline

Breath level R-744 Vents outlet R-744

40 km/h - III gear (30') IDLE - N (30') 90 km/h - V gear (20')

13,9°C

14,9°C

6,3°C

8,9°C

1.6 gasoline engine


LCCP results

Main assumptions

LCCP CO2-Equivalent Emissions during Vehicle's Lifetime

0

500

1 000

1 500

2 000

2 500

3 000

3 500

Frankfurt Madrid

CO

2-E

qu

iva

len

tE

mis

sio

ns

(kg

)

Baseline - R-134a R-134a-EnhancedR-744-baseline R-744-EnhancedR-1234yf-Baseline R-1234yf-Enhanced

Conclusions LCCP CO2-Equivalent Emissions during Vehicle's Lifetime

0

500

1 000

1 500

2 000

2 500

3 000

3 500

4 000

4 500

5 000

5 500

Average Europe Average World

CO

2-E

qu

iva

len

tE

mis

sio

ns

(kg

)

Baseline - R-134a R-134a-EnhancedR-744-baseline R-744-EnhancedR-1234yf-Baseline R-1234yf-Enhanced

Direct emissions: optimistic scenario

- < 6 g/y in EU as regular leak in use added to allothers (service, accident, EoL,…) leading to littlemore than 1 charge lost along life time. Worstcase being around 1,7 charge if no effort on R&R

Indirect emissions:

- Compressor shaft power : test bench results

- Electrical power : blower and fan powersaccording to Valeo control strategy

- Direct emissions of R134a leads to a 1/3 gapversus Low GWP refrigerants

- Indirect emissions between the 2 remaining ARoptions are in a small range < ± 10% depending ofclimate basis

- On a worldwide basis 1234-yf shows the lowestglobal emissions


Methodology for Torque estimation:control software based on physical models

TorqueEstimation

Compressormodel

Torque

CompressorrefrigerantEnthalpyestimation

Shaft powerestimation

CompressorModel

PRCITRCI

PRCO

Ncomp

PRCOTRCO

Densityestimation

PRCO

PRCOTRCOTextNcompIvalve

PRCO

Suction pressureestimation

Compressormodel

Mass flowEstimation

Expansion valvemodel

Suction temperatureestimation

Compressormodel

RefrigerantMass flow estimation

Condenser model

TorqueEstimation

Compressormodel

TorqueIsentropic

compressorenthalpydifference

CompressorShaft power

CompressorModel

PRCITRCIPRCO

Ncomp

Car speedFan powerPRCOTRCO

PRCONcompIvalve

Air flowEstimation

Front end model

PRCOTRCO

Suction pressureEstimation

Compressor model

Suction temperatureEstimation

Compressor model

Sub-critical

R-134a &

1234-yf

Inputs

Super-critical

R-744

Controlled

parametersSequence of physical models


Torque estimation and control results for R-134athe same algorithm is used for 1234-yf with an adjusted tuning

R-134a Windtunnel test : 25°C/55%/250Kg/hTorque estimation

-2

-1

0

1

2

3

4

5

6

7

8

0 200 400 600 800 1000 1200

Time (s)

To

rqu

e(N

.M)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Nco

mp

(rp

m)

Torque_estime Torque_error Torque_measured Ncomp

Torque estimated with +/- 1.5 N.M accuracy


Torque estimation and control results for R-744

R-744 Wind tunnel test: 25°C/55%Torque estimation

-2

-1

0

1

2

3

4

5

6

7

8

0 200 400 600 800 1000 1200

Time (s)

To

rqu

e(N

.M)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Nc

om

p(r

pm

)

Torque_measured Torque_error Torque_estim NComp

Torque estimated with +/- 1 N.Maccuracy


Conclusions

A/C system control with torque estimation is the key functionto deal with the energy efficiency challenge on MAC systems

This validated software approach brings key advantages:

No new device needed vs existing ones No additional cost

Same software structure and environment used Development robustness

Fully adaptable technique to all MAC solutions and market constraints– Adapted and tested for all A/C cycles R134a, R744, 1234-yf: multi-refrigerant

– Adapted to different compressor technologies Market oriented: multi-sourcing

– Able to be tuned to local efficiency requests Climate oriented: multi-region

– Able to adapt strategy (cool-down, stabilized,..) Real life oriented: multi-usage

Engine control optimized thanks to the given real-time dynamic A/C torque value

Many thanks for your attention

Documents

A/C System Control Strategies for Major Refrigerant … System Control Strategies for Major Refrigerant Options J.Benouali, ... ARSS Phoenix presentation ... Evaporator 6 passes 5,3