Development of Carbon Dioxide (CO2) Applied
Refrigeration System
<Compatibility of cooling performance and safety functions
with the use of electrically controlled expansion valve>
Torahide Takahashi
CalsonicKansei Corporation
2000
1
Contents of Presentation
1. Introduction
2. System Components & Specifications
3. Control Method
4. Results of Vehicle Tests
5. Summary
6. Future Activities
2000
2
1. Introduction
In the development of CO2 refrigeration systems, the challenge to
be met is to assure the cycle safety and the required cooling
performance at the same time,
time due to the higher refrigerant gas
pressure & temperature at the compressor outlet. (Compared with
HFC134a systems)
In order to meet this challenge, the CO2 refrigeration system we
have developed uses an electrically controlled expansion valve.
With the introduction of this electrically controlled valve,
our system has successfully achieved the required
cooling performance and safety levels.
2000
3
2. System Components & Specifications
2-1 Components
Gas cooler
Internal heat exchanger
Electrically controlled
expansion valve
‡E
‡D
Evaporator
‡B
Relief valve
Pressure SW
Pressure sensor 3.5
‡A Temperature
sensor
‡@
‡A
Pressure
(MPa)
‡C
‡C ‡B
10
‡E
‡D‡@
0•‹C31•‹C
Enthalpy (J/kg)
Mollier chart
CO2 Refrigeration
System
Accumulator
Compressor
2000
4
2-2 Specifications of components
HFC134a system
variable displacement type,
Compressor
swash plate
Displacement : 184 cc/rev
Multi-flow type
Gas cooler
swash plate
Displacement : 30 cc/rev
Multi-flow type
Multi-flow type
Core size (mm): 235W x 265H x 64D Core size (mm): 265W x 213H x 88D
Frontal area: 0.0628 m2
Frontal area: 0.0553 m2
Internal
heat
exchanger
Expansion Thermal expansion valve
valve
2000
fixed displacement type,
Core size (mm): 690W x 372H x 19D Core size (mm): 702W x 374H x 27D
Frontal area: 0.257 m2
Frontal area: 0.262 m2
Laminate type
Evaporator
CO2 system
Double tube serpentine type
Size: 19(dia) x 4 connections
Electrically controlled
expansion valve
5
•¢P (Pin•]Pout)
2-3 Electrically controlled expansion valve
Plunger
Solenoid
OUT
Outlet pressure: Pout
Compressor outlet
pressure & temperature
Up
Down
Smaller Duty
Larger
IN
Pilot valve
2000
Main valve
Piston
Solenoid
applied
voltage
Inlet pressure: Pin
a
b
Time
6
2-4 Vehicle installed condition
Evaporator (Passenger room)
Electrically
controlled
expansion valve
Internal heat
exchanger
Compressor
2000
Gas cooler
7
Pmax
Pressure limit
Relief valve operation value
P0
Protection control zone
nce
a
rm
o
f
r
pe one
g
re
in rol z
u
l
s
o
s
Co cont
pre ction
w
Lo ote e
pr zon
T0 T1
T2
Thermal limit
P1
Compressor off value
on temparature sensor
P2
Compressor off value
on electric pressure sensor
•ÛŒì•§Œä—̈æ
P4
Mechanical pressure switch operation value
P3
Expansion valve
control zone
Compressor outlet pressure (Mpa)
3. Control
3-1 System control
Tmax
Expansion valve control zone
Compressor outlet temperature (•‹C)
2000
8
3-2 Cooling performance control
Ambient sensor
Passenger room
temperature
Gas cooler
Engine
revolution
PTC set value
Internal heat exchanger
Control
amplifier
Accumulator
Pex
Tex
Proper duty
value
Clutch
Electrically controlled
expansion valve
Ps / Ts
Pe / Te
Clutch
Pd / Td
Compressor
Evaporator
Intake air
temperature sensor
Evaporator back
temperature sensor
2000
9
3-3 System protection control
(at gradual pressure & temperature rise)
Compressor outlet pressure
(Mpa)
Pmax
P4
P3
P2
Protection control zone
P1
P0
Gradual rise
g ance
n
i
l
Coo erform l zone
p ntro
co
Gradual rise
T0 T1
T2
Tmax
Compressor outlet temperature (•‹C)
2000
10
Pressure (Mpa)
3-3-1 Protection control at gradual pressure rise
Compressor OFF
P2
Protection control zone
Rising ratio
determining
P1
P0
Returning point
Cooling performance control zone
Expansion
valve opening
ratio (%)
100
Amplifier spec. value
0
Opening ratio will increase until the pressure becomes
lower than the control returning value.
Time
2000
11
3-3-2 Protection control at gradual temperature rise
Temperature
(•‹C)
T2
T1
T0
Compressor OFF
Protection control zone
Rising ratio
determining
Returning point
Cooling performance control zone
Expansion valve
opening
ratio (%)
100
Amplifier spec. value
0
Opening ratio will increase until the temperature
becomes lower than the control returning value.
Time
2000
12
3-4 System protection control
(at rapid pressure & temperature rise)
Compressor outlet pressure
(Mpa)
Pmax
P4
P3
P2
Protection control zone
P1
P0
Rapid rise
e
g
c
n
i
n
l
a
Coo rform l zone
pe ntro
co
Rapid rise
T0 T1
T2
Tmax
Compressor outlet temperature (•Ž )
2000
13
Pressure (Mpa)
3-4-1 Protection control at rapid pressure rise
P2
Compressor OFF
Protection
control zone
P1
Returning point
Expansion
valve opening
ratio (%)
P0
Cooling performance
control zone
100
Amplifier spec. value
0
Time
2000
14
Temperature (•‹C)
3-4-2 Protection control at rapid temperature rise
T2
Compressor OFF
Protection
control zone
T1
Returning point
T0
Expansion
valve opening
ratio (%)
Cooling performance
control zone
100
Amplifier spec. value
0
Time
2000
15
Engine revolution
(min-1)
3-5 System protection control
(at rapid engine revolution rise)
Increase rate
determination
Expansion
valve opening
ratio (%)
100
Amplifier spec. value
0
Time
2000
16
3-6 Other protective functions
1) Evaporator anti-freezing function
2) Refrigerant leak protection
3) Compressor protection at its
maximum speed operation.
2000
17
4. Vehicle Cool Down Test Results
Temperature (•‹C)
50
<Ambient conditions>
Temperature: 40•‹C
Humidity : 50%
Sun load: 1,050 W/m2
CO2
HFC134a
40 km/h
100 km/h
Idling
40
Room Average
30
20
Vent Outlet
10
0
0
2000
10
20
30
50
40
Time (min)
60
70
18
5. Summary
1) Same cooling performance level as the
HFC134a system was achieved due to
precise control of electrically controlled
expansion valve.
2)Through the control on changing ratio of
pressure and temperature, our CO2
system expanded operational zone.
And our system reduced clutch on/off
frequency and improved drivability.
2000
19
6. Future Activities
1) System weight reduction
2) System efficiency improvement
3) Further safety improvement
2000
20