1234yf System Evaluation

June 10, 2008

Ken Porrett / Eric ScarlettGeneral Motors Corporation

2

Introduction

Objective: evaluate performance impact of the HFO 1234yf refrigerantversus the production R134a system maximum air-conditioning performance and steady-state conditions for three

vehicles; Opel Astra, Opel Corsa, and GMC Acadia.

Evaluation items: refrigerant system modifications with the TXV compressor control valve refrigerant plumbing coaxial heat exchanger Evaporator Modifications Condenser Modifications

Fuel economy measurements are compared between the productionR134a system and final 1234yf configuration at nearly equal capacity

3

Astra System Configuration

IHX

600 g

19mm tube / 16mm hose

U-channel

0.210 Mpa cross charge, 2.0 ton

CTCi

43.6 psia

Delphi 6CVC135

1.6L Gasoline, 5-spd Transmission

Astra

525 g w/o IHX

¾” suction

modified

0.190 Mpa

Modified

45.0 psia

Changes

ChargeAmount

ControlValve

Suction Line

Evaporator

TXV

Condenser

Compressor

Powertrain

4

Charge Determination – Opel AstraAstra Charge Determination

1234yf with 3/4" suct line vs R134a with 5/8" suct line

-5.0

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

0.400 0.450 0.500 0.550 0.600 0.650 0.700

charge (KG)

SH

,S

C,

Tem

p

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Pre

ssu

re(k

pa)

1234yf ave Evap Air Out

1234yf Evap Out SH

1234yf Cond Out SC

R134a Ave Evap Air Out Grid

R134a Evap Out SH

R134a cond out SC

1234yf Pd

R134a Pd

1234yf charge R134a charge

Evap Out SH up 7C

Condenser Out SC reduced ~2C

Evap Air Out Temperature up ~1.5C

Discharge pressure reduce ~50 kpa

Charge level reduced ~10%

Changes from R134a to HFO1234yf

5

Maximum A/C Performance – Opel Astra

0%1234yf w/ ¾”

+2.5%1234yf IHX

R134a

% Capacity Change

Astra #237 (Modified Evaporator Core)- GMW3037

------- R134a Baseline -------1234yf w/ 3/4" suction Line -------1234yf w/ IHX

0

10

20

30

40

50

60

70

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Time (sec)

Tem

pe

ratu

re(C

)

0

400

800

1200

1600

2000

2400

2800

Pre

ssu

re(k

pa)

Compressor Out Pressure

Avg Front Breath

Avg Evap Air Out Grid

50 kph REC 80 kph REC 50 kph OSA 80 kph OSA Idle REC 110 kph OSA Idle OSA

6

Detailed Analysis– Opel Astra

+3 K SCincreasedNo changeModifiedCondenser Core

No effectNo effect0-1 C colderModifiedEvaporator Core

No effectNo effectNo changeTXV

No effectNo effect0-1 C colder¾” Suction Line

Increased SC atTXV in 6C

No effect1-2 C colderexcept at OSA

Idle

Front IHX

Effect onCondenser Out SC

Effect onCompressor OutPressure

Effect on EvapOut Air Temp

ComponentChange

7

GMC Acadia System Configuration

1050 g

19mm (3/4” inch)

Front - 42 Tube, Flat Tube 6 Pass Rear- 24 Tube, Flat Tube 6 Pass

Front - 0.195 Mpa Cross Charge, 2.0 T

Rear –0.140 Mpa Gas Charge, 0.6 T

4 Pass

Evaporator Air Temp Sensor

Denso 10S20

3.6L Gasoline/6-spd Automatic

Baseline

900 gChargeAmount

CompressorControl

Front IHXSuction LineDia.

Evaporator

TXV

ModifiedCondenser

Compressor

Powertrain

Changes

8

Charge Determination – GMC AcadiaLambda Charge Determination

0.0

5.0

10.0

15.0

20.0

25.0

0.700 0.750 0.800 0.850 0.900 0.950 1.000 1.050

Charge (kg)

Tem

p(C

),S

H&

SC

(K)

1300

1400

1500

1600

1700

1800

Pre

ssu

re(k

pa

)

1234yf Avg Vent Temp

1234yf Evap Out SH

1234yf Front TXV IN SC

R134a Avg Vent Temp

R134a Evap Out SH

R134a TXV n SC

1234yf Comp Out Press

R134a Comp Out Press

1234yf charge R134a charge

Lower Condenser Out SubCool ~2K

Higher Average Panel Temp ~4C

Higher Compressor In Superheat ~8K

Lower Comp Discharge Pressure~50kpa

Reduced Charge - Approx 10%

Charge Comparison

1234yf vs. R134a

9

Maximum A/C Performance – GMC AcadiaLambda GMW3037 Front Vent & Breath and Compressor Out Pressure (Drop In)

0

10

20

30

40

50

60

70

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

time (sec)

tem

p(C

)

0

400

800

1200

1600

2000

2400

2800

Pre

ssu

re(k

pa

)

50 kph REC 80 kph REC 50 kph OSA 80 kph OSA Idle REC 110 kph OSA Idle OSA

Compressor Out Press

Ave Front

Breath

Ave Front EvapGrid Air

----- R134a Baseline -----1234yf drop in

-3.9%1234yf drop in

R134a

% Capacity Change

10

Detailed Analysis– GMC Acadia

+ 2 K (eliminatedTXV hunting)

+ 100 kpaNo changeModifiedCondenser Core

NANANAModifiedEvaporator Cores

No effectNo effectNo changeTXV

Effect onCondenser OutSC

Effect onCompressor OutPressure

Effect on EvapOut Air Temp

ComponentChange

11

Opel Corsa System Configuration

450 g

Modified Suction Line

Changes

470 gChargeAmount

0.188 MpaControlValve

18mm tube / 16mm hoseSuction Line

195 x 295 x 38Evaporator

0.200 MPa, Cross ChargeTXV

MFIV, 248 x 647 x 16

2 Pass: 27/6 (tubes)

Condenser

Denso 5SL12Compressor

1.7L Turbo Diesel, 6-spdManual

Powertrain

Corsa

12

Charge Determination – Opel Corsa

Opel Corsa Charge Determination1234yf Drop-in versus R134a Baseline

0

5

10

15

20

25

30

35

40

45

0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70

Charge (kg)

Tem

p(C

),S

H&

SC

(K)

400

600

800

1000

1200

1400

1600

1800

2000

2200

Pre

ss

ure

(kp

a)

1234yf Avg Vent Temp

1234yf Comp In SH

1234yf Cond Out SC

R134a Avg Vent Temp

R134a Comp In SH

R134a Cond Out SC

1234yf Comp Out Press

R134a Comp Out Press

1234yf charge R134a charge

Compressor In SH Increased ~ 5° K

Condenser Out SC Reduced ~ 1.5° K

Average Vent Temp up ~ 1.3° K

Disch Pressure Reduced ~ 120 kpa

Charge Level Reduced ~ 10%

Charge Comparison

1234yf vs. R134a

13

Maximum A/C Performance – Opel Corsa

- 2.6%

- 4.1%

% Capacity change

1234yf Mod Suction

1234yf Drop-In

R134a

14

Detailed Analysis– Opel Corsa

Testing in Progress

IHX

600mm,

25mm O.D.

- 3° K SCReducedapprox 80kPa

@ 80kph

+ 0.6° KModifiedSuction Line

- 1° K SCReducedapprox 120kPa

@ 80kph

+ 1.0° KDrop-In

Effect onCondenser Out

SC

Effect onCompressorOut Pressure

Effect on EvapOut Air Temp

ComponentChange

15

GREEN-MAC-LCCP Analysis of Corsa System

16

15C 25C 35C

Ambient Condition (Deg C)

Over

Co

nsu

mp

tio

nfo

rA

/CU

sag

e(L

/100km

)

Corsa R134a

Corsa 1234yf

Fuel Economy Analysis – Opel Corsa

Fuel Consumption for A/C UsageCombined SCO3 and FTP Highway

Evaporator Capacity35°C x 40%RH, 850 w/m2

Annualized Fuel Consumption(Based on Time in Ambient)

1234yfR134a

3.1%3.0%Frankfurt

13.1%14.0%Phoenix

Highway

SCO3

~ Equal

~ Equal

1234yfR134a

17

15C 25C 35C

Ambient Condition (deg C)

Ove

rC

on

su

mp

tio

nfo

rA

/CU

sa

ge

(L/1

00k

m)

Astra R134a

Astra 1234yf

Fuel Economy Analysis – Opel Astra

Fuel Consumption for A/C UsageCombined SCO3 and FTP Highway

Evaporator Capacity35°C x 40%RH, 850 w/m2

Annualized Fuel Consumption(Based on Time in Ambient)

1234yfR134a

4.0%3.8%Frankfurt

12.2%12.4%Phoenix

Highway

SCO3

~ Equal

~ Equal

1234yfR134a

18

NEDC Fuel Economy Estimate – Corsa/Astra

19

System Configurations to be Considered

Opel Corsa1. IHX2. TXV3. Compressor Control Valve4. Condenser

Opel Astra1. IHX2. TXV

GMC Acadia1. Front & Rear IHX2. Evaporator/TXV3. Compressor

High Mileage Durability testing to begin July 2008.

20

Conclusions

1. Performance enhancements are required for 1234yfto equal R134a

2. Best system configuration is vehicle/supplierdependent

3. Fuel Consumption impact is minimal

4. LCCP impact is reduced with HFO1234yf

Thanks to

Delphi, Denso & Behr

for their support