DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 1Date: 24.02.2005
Concerns about CO2 A/C Systemsfor Compact Vehicles and their
Solutions
24.02.2005
Dr. Werner Hünemörder
DENSO AUTOMOTIVE Deutschland GmbH
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 2Date: 24.02.2005
• 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
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 3Date: 24.02.2005
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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 4Date: 24.02.2005
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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 5Date: 24.02.2005
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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 6Date: 24.02.2005
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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 7Date: 24.02.2005
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
Problem for Compact Vehicles• Introduction
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 8Date: 24.02.2005
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.
Tair in = 45°C (Tamb = 30°C)
Problem for Compact Vehicles• Introduction
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
Tair in = 45°C (Tamb = 30°C)
Tair in = 35°C (Tamb = 20°C)
DENSO AUTOMOTIVE Deutschland GmbH
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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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 10Date: 24.02.2005
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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 11Date: 24.02.2005
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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 12Date: 24.02.2005
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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
1
Se
ries c
on
de
ns
er s
ize
25K
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 13Date: 24.02.2005
Evaporator inlet air: 40°C, 60%RH
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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 14Date: 24.02.2005
Power consumption trend for CO2 systems
Evaporator inlet air: 40°C, 60%RH
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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
The CO2 system efficiency will increase in the future
DENSO AUTOMOTIVE Deutschland GmbH
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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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
Control of compressor power consumption
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 16Date: 24.02.2005
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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
Control of compressor power consumption
DENSO AUTOMOTIVE Deutschland GmbH
This information is exclusive property of DENSO Corporation. Without their consent, it may not be reprinted or given to third parties Page 17Date: 24.02.2005
Coordination with powertrain
EngineOutput (driving)
Compr. Air-conditioning
Displacement controlTemperature control
Displacement controlDischarge pressure control (safety)
Compressor management
Driving condition
Drivers request
• Introduction
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary
Control of compressor power consumption
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
DENSO AUTOMOTIVE Deutschland GmbH
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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
• Problems for compact vehicles
• Power consumption comparison
• Reduction of compressorpower consumption
• Power consumption trend for CO2 system
• Control of compressorpower consumption
• Summary