Concerns about CO2 A/C Systems for Compact Vehicles and ... · DENSO AUTOMOTIVE Deutschland GmbH...

DENSO AUTOMOTIVE Deutschland GmbH

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Concerns about CO2 A/C Systemsfor Compact Vehicles and their

Solutions

24.02.2005

Dr. Werner Hünemörder




• Introduction

• Problem for compact vehicles

• Power consumption comparison

• Reduction of compressor power consumption

• Power consumption trend for CO2

• Control of the compressor power

consumption

• Summary

Contents• Introduction

• Problems for compact vehicles


• Reduction of compressorpower consumption

• Power consumption trend for CO2 system

• Control of compressorpower consumption

• Summary



Requirements for the implementation of a new refrigerant for vehicle A/C systems

• Environmental Benefit

Indirect & Direct Global warming Impact

• Cooling Performance

• Efficiency and Energy consumption

• Quality, Costs, Weights

• Safety, Serviceability

• applicable to all vehicles (also for small cars)

• applicable to all climate conditions

• Introduction






• Summary



Vehicle Trend

7%

24%

30%

22%

17%Seg. A

Seg. B

Seg. C

Seg. D

Seg. E

61%

39%Seg. A-C

Seg. D-E

Japan (2003)

Europe (2003)

- Compact vehicles (segment A-C) occupy about 60% of the

market in Europe and Japan

- The share of compact vehicles will increase due to fuel economy regulation

• Introduction






• Summary



Climate Conditions

Frankfurt Brussels Los Angeles Dubai Tokyo

10

20

30

40

24°C23°C

29°C

41°C

31°C

0

Average maximum temperature[°C]

Target: CO2 A/C systems in compact vehicles must have the same

performance as current R134a systems under severer climate

conditions

• Introduction






• Summary



The ground Temperature: 65°C

Gas cooler air inlet conditions in idle conditions

The gas cooler inlet air temperature rise is up to 20K due to “convection”

and “hot air re-circulation”

Ambient:40°C (convection)

45°C

50°C … 60°C

(hot air re-circulation)

Problem for Compact Vehicles• Introduction






• Summary



Pre

ss

ure

Enthalpy

30°C

40°C

50°C

60°C

op

t. C

OP

lin

e

The influence of gas cooler air temperature to the system

performance

Internal heat exchanger

Tair in =45°C

TRefrigerant ≈≈≈≈ 50°C

Ta

mb

= 3

0°C

eva

po

rato

r

Ga

s c

oo

ler

Exp

an

sio

n v

alv

e

co

mp

resso

r

accu

mu

lato

r

TRefrigerant ≈≈≈≈ 50°C







• Summary



CO2 System HFC-134a System

Comparison of the CO2 and R134a cycle

Pre

ss

ure

Enthalpy

40°C

50°C

∆∆∆∆hev ∆∆∆∆hc

Pre

ss

ure

Enthalpy

30°C

40°C

50°C

60°C

∆∆∆∆hev ∆∆∆∆hc

Tair in = 35°C (Tamb = 20°C)

� The COP of the CO2 system is decreasing quicker than the COP of the R134a system

Quicker decrease of evaporation enthalpy (∆hev) and increase of compressor power consumption (∆hc) of the CO2 system with higher air temperature.








• Summary





CO2 system has a large power consumption rise by the temperature rise

of gas cooler inlet air

Ø16x2000

W199

xH231xD38

W500

xH325xD16

Variable

CO2

VariableCompressor

-

Internal Heat

Exchanger

W199

xH231xD38Evaporator

W500

xH325xD16

HFC-134a

Gas cooler /Condenser

Specifications of A/C components

for compact vehicles (engine volume 1.0l)

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

20 30 40 50 60 70

Gas cooler inlet air temp.(°C)

Idling

Evaporator inlet air:

25°C, 50% RH

Co

mp

res

so

r p

ow

er

rati

o CO2

HFC-134a

Power Consumption

Comparison of CO2 and HFC-134a

• Introduction






• Summary



The increase in compressor power consumption at high ambient

temperatures has a big impact on the vehicles driving performance

0

40

80

120

48%

increased

CO2

R134aV

eh

icle

Sp

ee

d(k

m/h

)

Time

Full power acceleration

30°C w/solar radiation

FRS, Max Cool

CO2 R134a

25% decreased

Fu

el

Eco

no

my R

ati

o

LA#4mode30°C, w/solar radiationFRS, Max Cool

1.0

0

Acceleration - Fuel Economy

Power Consumption• Introduction






• Summary



Enlargement of Gas cooler

&

Reduction of hot air re-circulation by improved sealing

The extension of vehicle length has a significant influence especially on

compact vehicle design

Improved sealingIncreased gas

cooler width

Vehicle

design

Vehicle length extension

Concern for the vehicle design

Reduction of compressor power consumption• Introduction






• Summary



The reduction of the air temperature before gas cooler and the increase

of the gas cooler size are necessary

Reduction of compressor power consumption

0

0.2

0.4

0.6

0.8

1

1.2

1.4

400 600 800 1000

Gas cooler width size (mm)

Co

mp

res

so

r p

ow

er

rati

o (

R1

34

a=

1)

Evaporator inlet air: 40°C, 60%RH

Cooling performance=3.3kW (constant)

Gas cooler inlet air temp. for CO2

60°C

55°C

Ambient temp.

+20K

Ambient temp.

+15KGas cooler size up

• Introduction






• Summary

1

Se

ries c

on

de

ns

er s

ize

25K




Gas cooler inlet air : 60°C, idling

(Ambient temp. +20K)

R134a CO2 CO2Ejector

Co

mp

res

so

r p

ow

er

rati

o(R

13

4a

=1)

1

Ejector

Gas cooler

Compressor

Accumulator

Evaporator

Ejector Cycle

Internal heatexchanger

Pre

ss

ure

Enthalpy

- New approach to achieve same efficiency as 134a system

- The system is more complicated than normal CO2 system

Reduction of Compressor Power Consumption

Decompression loss energyis recovered by Ejector

• Introduction






• Summary



Power consumption trend for CO2 systems


Gas cooler inlet air : 60°C, idlingC

om

pre

ss

or

po

wer

rati

o (

HF

C-1

34a

= 1

)

1

decreasing of gas cooler inlet air temperature

and

Adopting new technologies (CO2 Ejector, etc.)

’99 ’04 future

Further improvement of

A/C components

improvement of

A/C components

• Introduction






• Summary

The CO2 system efficiency will increase in the future



Application for Small Vehicles

1.Worse Fuel cons.

2.Worse Drivability

3.quick Pd increase

(Small G.C., fixed orifice)

Task of Small Vehicle Proposal

60

65

70

75

80

85

90

ηη ηηta

d　（

％）

　（

％）

　（

％）

　（

％）

Idle ( 800rpm )

R134a

+20%

2. Mass flow control

1.Reduce Power consumption by high efficiency compressor

2.Accurate Torque control by mass flow control

3.Prevent Pd peak by mass flow control

High accurate torque estimation

Acceleration control

Safety control (Prevent Pd peak)

crankcase

F= A*(PH-PL) F=Fsol

PL

Mass flow

Throttle

PH

1. High compressor efficiency

• Introduction






• Summary

Control of compressor power consumption



Accurate torque estimation

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

Measured

Estimation

Time (sec)

To

rqu

e (N

m)

To control high torque at high load condition

TrqNm

Time sec

idle

PdMPa

L[Kw]

R134aCO2

Merit of mass flow control for Small Vehicle

• Introduction






• Summary




Coordination with powertrain

EngineOutput (driving)

Compr. Air-conditioning

Displacement controlTemperature control

Displacement controlDischarge pressure control (safety)

Compressor management

Driving condition

Drivers request

• Introduction






• Summary


ECU

Cooperative control of engine , A/C and compressor

0 20 40 60

4

8

10

12

To

rqu

e (

Nm

)

Time(s)

Target Torque

Real Torque

Comp. power

Displacement controlCompressor power consumption

target torque

actual torque



Some technological issues still remain before introducing CO2 A/C systems to various markets of the world.

To keep the same quality level as current R134a systems at high load conditions, the following items must be considered:

+ Vehicle design - reduction of gas cooler air inlet temperature

- avoiding re-circulation by improved sealing

- vehicle front-end design

+ A/C system design - improvement of the system and components

- increase Component efficiency

- Ejector system

- Torque control

Summary• Introduction






• Summary

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Concerns about CO2 A/C Systems for Compact Vehicles and ... · DENSO AUTOMOTIVE Deutschland GmbH...

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