CO2-A/C-system
COP comparison R134a vs. CO2
•Characteristic of the CO2- cooling cycle
•Test bench investigation R134a vs. CO2
•Calculation of Power Consumption in
NEFZ-Driving Cycle
•Summary
abc
Dradi, 2000-03-08
CO2-A/C-system
Thermodynamic process
pressure
CO2-process
120 bar
32°C/ 101°C
R134a-process
20 bar
35 bar
1 bar
abc
enthalpy
Dradi, 2000-03-08
CO2-A/C-system
Thermodynamic process
pressure
120 bar
32°C
CO2-process
•Existence of a COP optimum
high pressure
35 bar
enthalpy
abc
Dradi, 2000-03-08
CO2-A/C-system
Thermodynamic process
pressure
CO2-process
120 bar
•Existence of a COP optimum
high pressure
•COP highly dependent to air
flow through the gas cooler
32°C
35 bar
enthalpy
abc
Dradi, 2000-03-08
CO2-A/C-system
Thermodynamic process
pressure
CO2-process
120 bar
•Existence of a COP optimum
high pressure
•COP highly dependent to air
flow through the gas cooler
•At low ambient temnperatures
high COP
32°C
35 bar
enthalpy
abc
Dradi, 2000-03-08
CO2-A/C-system
Thermodynamic process
pressure
CO2-process
120 bar
•Existence of a COP optimum
high pressure
•COP highly dependent to air
flow through the gas cooler
•At low ambient temnperatures
high COP
•Internal heat exchanger
32°C
1. Increases cooling capacity at
high ambient air temperatures
2. Increases COP
35 bar
enthalpy
abc
Dradi, 2000-03-08
CO2-A/C-system
System layout
Expansion- Pressuresensor
valve
Temperaturesensor
Internal heat exchanger
Fan
t°
P
Gascooler
Receiver
Compressor
t°
Ambient air
Evaporator
t°
Air temperature
at evap. outlet
Outlet airflow
Engine control unit
Control unit
Control panel
abc
Dradi, 2000-03-08
CO2-A/C-system
System layout
COP optimized high pressure control
Expansion- Pressuresensor
valve
Temperaturesensor
Internal heat exchanger
Fan
t°
P
Gascooler
Receiver
Compressor
t°
Ambient air
Evaporator
t°
Air temperature
at evap. outlet
Outlet airflow
Engine control unit
Control unit
Control panel
abc
Dradi, 2000-03-08
CO2-A/C-system
System layout
Expansion- Pressuresensor
valve
Internal heat exchanger
Fan
t°
P
Sammler
Temperaturesensor
Gascooler
Ambient air
Comfort & energy
optimized suction pressure control
Kompressor
t°
Evaporator
t°
Air temperature
at evap. outlet
Outlet airflow
Engine control unit
Control unit
Control panel
abc
Dradi, 2000-03-08
CO2-A/C-system
Test bench
Conditioning of fresh air
Outlet air
Fresh-air mode
HVAC
Passenger compartment model
Climatic chamber air flow
Gas cooler air flow
Frontend
abc
Dradi, 2000-03-08
CO2-A/C-system
comparison CO2- vs. R134a-A/C-system
Selection
Selectionof
ofclimate
climate
conditions
for
conditions forbench
bench
tests
tests
Measurement
Measurementof
ofcooling
coolingcapacity
capacityof
ofthe
the
R134a-A/C-system
in
fresh-air
mode
R134a-A/C-system in fresh-air mode
Measurement
Measurementof
ofthe
thepower
power
consumption
of
the
CO2-A/C
consumption of the CO2-A/C
system
systemat
atthe
thesame
samecooling
cooling
capacity
capacity
Calculation
Calculationof
ofthe
thepower
powerconsumption
consumptionof
ofthe
the
A/C-systems
in
the
NEFZ-driving
cycle
A/C-systems in the NEFZ-driving cycle
abc
Dradi, 2000-03-08
CO2-A/C-system
comparison CO2- vs. R134a-A/C-system
g
J/k
k
60
g
J/k
k
50
g
J/k
k
40
g
J/k
k
30
%
30
G
point
15
g
J/k
k
10
D
point
tF
poin
10
g
J/k
k
0
%
10
5
g
J/k
k
20
E
point
%
20
water content [g/kg]
g
J/k
k
70
tH
poin
I
point
20
g
J/k
k
80
g
J/k
k
90
0%
10
%
90
%
80
%
70
%
60
%
50
%
40
25
g
J/k
k
0
10
0
45
abc
35
25
15
5
-5
-15
temperature [°C]
Dradi, 2000-03-08
CO2-A/C-system
comparison CO2- vs. R134a-A/C-system
cooling capacity
6000
5000
4000
cooling capacity
[W]
3000
2000
1000
140
93
velocity
47
[km/h]
abc
43.0°C/15%
0
40.0°C/40%
35,0°C/40%
ambient conditions
30,0°C/75%
25.4°C/55%
19,8°C/64%
0
Dradi, 2000-03-08
CO2-A/C-system
comparison CO2- vs. R134a-A/C-system
power consumption of R134a-compressor
6000
5000
4000
power
consumprtion
[W]
3000
2000
1000
140
93
velocity
47
[km/h]
40.0°C/40%
0
43.0°C/15%
abc
35,0°C/40%
ambient conditions
30,0°C/75%
25.4°C/55%
19,8°C/64%
0
Dradi, 2000-03-08
CO2-A/C-system
comparison CO2- vs. R134a-A/C-system
power consumption of CO2 -compressor
6000
5000
4000
power
consumption
[W]
3000
2000
1000
140
93
velocity
47
[km/h]
43.0°C/15%
30,0°C/75%
35,0°C/40%
ambient conditions
0
40.0°C/40%
abc
25.4°C/55%
19,8°C/64%
0
Dradi, 2000-03-08
CO2-A/C-system
comparison CO2- vs. R134a-A/C-system
comparison of power consumption
1500
1000
500
power consumption
CO2 - R134a
[W]
0
-500
-1000
43.0°C/15%
30,0°C/75%
35,0°C/40%
ambient conditions
0
40.0°C/40%
abc
25.4°C/55%
19,8°C/64%
-1500
140
93
velocity
47
[km/h]
Dradi, 2000-03-08
CO2-A/C-system
NEFZ-driving cycle
140
120
velocity [km/h]
100
80
60
40
20
0
0
abc
200
400
600
800
1000
time [s]
Dradi, 2000-03-08
CO2-A/C-system
NEFZ-driving cycle at 19.8°C, 64% r.h.
140
0.18
externally controlled R134a-compressor
0.16
externally controlled CO 2-compressor
0.14
100
velocity [km/h]
0.12
80
0.1
60
0.08
0.06
40
0.04
cumulative power consumption [kWh]
120
20
0.02
0
0
0
abc
200
400
600
800
1000
time [s]
Dradi, 2000-03-08
CO2-A/C-system
NEFZ-driving cycle at 25.4°C, 55% r.h.
140
0.3
externally controlled R134a-compressor
120
externally controlled CO 2-compressor
100
velocity [km/h]
0.2
80
0.15
60
0.1
40
cumulative power consumption [kWh]
0.25
0.05
20
0
0
0
abc
200
400
600
800
1000
time [s]
Dradi, 2000-03-08
CO2-A/C-system
NEFZ-driving cycle at 30.0°C, 75% r.h.
140
0.9
externally controlled R134a-compressor
0.8
externally controlled CO2-compressor
0.7
100
velocity [km/h]
0.6
80
0.5
60
0.4
0.3
40
0.2
cumulative power consumption [kWh]
120
20
0.1
0
0
0
200
400
600
800
1000
time [s]
abc
Dradi, 2000-03-08
CO2-A/C-system
NEFZ-driving cycle at 35.0°C, 40% r.h.
140
0.8
externally controlled R134a-compressor
externally controlled CO 2-compressor
0.6
velocity [km/h]
100
0.5
80
0.4
60
0.3
40
0.2
20
cumulative power consumption [kWh]
0.7
120
0.1
0
0
0
200
400
600
800
1000
time [s]
abc
Dradi, 2000-03-08
CO2-A/C-system
NEFZ-driving cycle at 40.0°C, 40% r.h.
140
1.2
externally controlled R134a-compressor
120
externally controlled CO 2-compressor
100
velocity [km/h]
0.8
80
0.6
60
0.4
40
cumulative power consumption [kWh]
1
0.2
20
0
0
0
abc
200
400
600
800
1000
time [s]
Dradi, 2000-03-08
CO2-A/C-system
NEFZ-driving cycle at 43.0°C, 15% r.h.
140
1
externally controlled R134a-compressor
0.9
externally controlled CO 2-compressor
e
0.8
velocity [km/h]
100
0.7
0.6
80
0.5
60
0.4
0.3
40
cumulative power consumption [kWh]
120
0.2
20
0.1
0
0
0
abc
200
400
600
800
1000
time [s]
Dradi, 2000-03-08
CO2-A/C-system
Comparison power consumption at NEFZ-driving cycle
relation of power consumption CO2 vs.
R134a
1.4000
1.2000
1.9
4.9
2.8
• Better gascooler heat transfer at low and medium temperatures
• High pressure losses along R134a-evaporator at high
cooling capacity
• Lower gascooler heat transfer at high temperatures
1.2
1
0.8
1.0000
0.6
0.8000
0.4
0.6000
total compressor work [kWh]
1.1
cooling capacity [kW]
4.1
3.4
0.2
CO2-system
R134a-system
0.4000
0
19,8°C/64%
abc
25.4°C/55%
30,0°C/75%
35,0°C/40%
ambient conditions
40.0°C/40%
43.0°C/15%
Dradi, 2000-03-08
CO2-A/C-system
Summary
•Power consumption dependent on annual climate condition
•Advantages at
•Medium temperatures (<~33°C)
•High cooling capacities due to high humidity
•Disadvantages at
•High temperatures (>~33°C)
•Idle speed
abc
Dradi, 2000-03-08
CO2-A/C-system
Outlook
•CO2-system to be further developed in regard to efficiency
•Optimizing the HVAC unit for CO2-heat exchanger
•Adaptation of the refrigerant passes in the gas cooler to the
realistic airflow in the frontend
•Open point: Small car A/C-system,
Power consumption/cooling capacity/drivability at idle speed and high ambient air
temperatures
abc
Dradi, 2000-03-08