a/c system control strategies for major refrigerant …june 11th, 2008 i 2 property of valeo –...
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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
June 11th, 2008 I 3 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
June 11th, 2008 I 4 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
Pressure sensor (condenser outlet)Evaporator Air Temperature sensor
Pressure sensor (condenser outlet)Evaporator Air Temperature sensor
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
June 11th, 2008 I 5 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
June 11th, 2008 I 6 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
June 11th, 2008 I 7 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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(-
)
R-134a baseline R-134a enhanced
R-744 baseline R-744 enhanced
HFO-1234yf baseline HFO-1234yf enhanced
June 11th, 2008 I 8 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
)
R-134a baseline R-134a enhanced
R-744 baseline R-744 enhanced
HFO-1234yf baseline HFO-1234yf enhanced
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(-
)
R-134a baseline R-134a enhanced
R-744 baseline R-744 enhanced
HFO-1234yf baseline HFO-1234yf enhanced
June 11th, 2008 I 9 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
)
R-134a baseline R-134a enhanced
R-744 baseline R-744 enhanced
HFO-1234yf baseline HFO-1234yf enhanced
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)
-CD2 : conditions after 10’ (40 km/h III gear phase)
-CD3 : conditions after 30’ (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(-
)
R-134a baseline R-134a enhanced
R-744 baseline R-744 enhanced
HFO-1234yf baseline HFO-1234yf enhanced
June 11th, 2008 I 10 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
June 11th, 2008 I 11 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
June 11th, 2008 I 12 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
June 11th, 2008 I 13 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
June 11th, 2008 I 14 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
June 11th, 2008 I 15 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
June 11th, 2008 I 16 IProperty of Valeo – Duplication prohibitedARSS Phoenix presentation – C.Petitjean
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
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