Design of the thermosiphon Test Facilities
2nd Thermosiphon Workshop
A. MORAUX
PH Dpt / DT Group
CERN
October 1st 2009
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 Proposal overview and
objectives
Condenser
Summary
 Thermodynamic cycle
 Operating scenarios
 Services
 Conclusion
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Evaporator
 Design parameters
2
Interests and Objectives
 Provide a natural circulation of the fluid
 Avoid working components in the main circuit
 Access refrigeration units in the surface and make maintenance
easier
 Validate gravity driven system design
 Achieve cooling at low temperature (-40 C)
 Compensate pressure drops in cooling channels by low temperature
condensation on surface
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Process Diagram
0.59 Bar
-48.0 C
SURFACE
11.5 Bar
+20.0 C
11.5 Bar
-25.0 C
PIT
70 m
0.8 Bar
+20.0 C
CAVERN
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Cycle of the cooling system
Operation at -40°C (evaporation temperature in the boiling channel)
-25C
T T= =-25C
P = 11.5 bar
P = 13.55 bar
m’ = 60 g/s
m' = 60 g/s
T = 20C
T = 20C
P = 11.5 bar
P = 13.55 bar
m’ = 60 g/s
m' = 60 g/s
I
SURFACE
Storage Tank
&
Condenser
A
C3F8
Chiller
T = -40C
P = 0.87 bar
m' =60 g/s
x = 0.58
T = +20C
P = 0.8 bar
m' = 60 g/s
Δh ≈ 80m
PIT
T = -48.8C
P = 0.57 bar
m' = 60 g/s
T = -41.9C
P = 0.8 bar
m' = 60 g/s
x = 0.9
BY PASS
T = 20C
P = 0.57 bar
m' = 60 g/s
Heater
Heater
C
B
Filter
CAVERN
TEST SECTIONS
Heater
D
E
F
G
H
DUMMY LOAD
1 kW LOOP
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Operating Scenarios
 Purging and filling the system
I
 Start-up
SURFACE
Storage Tank
&
Condenser
A
C3F8
 Nominal operating conditions
with 0.1 kW loop
Chiller
 Nominal operating conditions
with full power
Δh ≈ 80m
PIT
BY PASS
Heater
Heater
C
B
Filter
CAVERN
TEST SECTIONS
Heater
D
E
F
G
H
DUMMY LOAD
1 kW LOOP
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Design parameters: Test sections and Mass flow (1/4)
Evaporation
temperature
[°C]
Nominal
power load
[kW]
Outlet
quality
Inlet
quality
Latent heat
[kJ/kg]
Mass flow rate
[g/s]
Nominal operation
-40
2.0
0.9
0.58
106.3
58.8
-25
2.0
0.9
0.48
100.8
47.2
0
2.0
0.9
0.24
90.3
33.5
-25
0.1
0.9
0.48
100.8
2.3
-35
0.1
0.9
0.55
104.5
2.7
mass flow rate baseline under different operating conditions
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Transfer lines (1/2)
 Material: Stainless Steel 304L
 70m Liquid transfer line characteristics
 Mass without fluid (pipe + insulation): 145 kg
 Mass with fluid (density = 1600 kg/m3): 220 kg
♦ Thermal expansion
70 m
♦ Nominal diameter / pressure: DN25 / PN25
♦ Insulation: 25mm ARMAFLEX A/F
♦ Weight (for sizing wall support)
 From 20 C to -40 C → Length change = - 0.072 m
 70m Gas transfer line characteristics
♦ Nominal diameter / pressure: DN50 / PN10
♦ No insulation
♦ Weight: 205 kg
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Transfer lines (2/2)
 Liquid transfer line
♦ Outlet temperature (Inlet temperature = -48 C)
 -25 C with mass flow = 60 g/s (ΔT = 18 C)
 +12 C with mass flow = 6 g/s (ΔT = 60 C)
♦ Pressure drops (taking into account density change along pipe)
 Frictional pressure drop is in the order of 5 mbar
 Hydrostatic pressure = 9.6 bar with mass flow = 6 g/s
 Hydrostatic pressure = 10.9 bar with mass flow = 60 g/s
♦ Outlet pressure
 10.2 bar with mass flow = 6 g/s
 11.5 bar with mass flow = 60 g/s
 Gas transfer line
♦ Calculated pressure drop (hydrostatic + frictional + singular) = 90 mbar
♦ Condensation temperature is designed for ΔP = 300 mbar
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Transfer line to test section
 Approximate required length : 15 m (DN 25)
 Equipment
♦
♦
♦
♦
Thermal tapes
H2O Filters
Mass flow meter (0 - 100 g/s)
C3F8 bulk temperature measurements
 Thermal tapes
♦
♦
♦
♦
Heating the liquid up to 20 C
Maximum required power: 3kW
Thermal tapes switched on according to the test sections in use
Temperature control by PWM
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Bypass line (1/2)
 Approximate required length : 4 m
 Pipes nominal diameter
♦ Inlet DN15
♦ Outlet DN25
 Equipment
♦
♦
♦
♦
Valves (shut-off and control)
Evaporator
Mass flow meter (0 - 20 g/s)
Instrumentation
PT
FT
 Bypass control
♦ Flow control or Bottom temperature control
♦ Evaporation pressure
♦ Water glycol bath temperature
TT PT
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Bypass line (2/2) - Evaporator
 Objectives
♦ Heat the liquid up to 20 C
♦ Evaporate the fluid at 20C
 Design height: 1.5 m
 Design external diameter: 0.4 m
 Required power: 1.25 kW (10 g/s)
 Internal spiral
♦ Pipe nominal diameter: DN15
♦ Spiral nominal diameter: 0.3 m
♦ Approximate height: 1.2 m
 Water/Glycol bath
Simulations performed
by A. Romanazzi
♦ Maintain at constant temperature by electrical heater
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Storage vessel
 Storage vessel size and volume
0.6 m3
♦ Useful volume 600 L
♦ Approximate internal diameter: 1 m
♦ Approximate internal length: 1.5 m
ID = 1
h = 0.25
 Heat loads
♦ Insulation: 25mm ARMAFLEX A/F
♦ Heat pickup in the tank: 250 W @ -48°C
Length = 1.5
 Flanges, feedthroughs and instrumentation
♦
♦
♦
♦
♦
♦
♦
♦
2 Temperature sensors
1 High and 1 low pressure gauges
1 Level gauge and 1 low level switch
Safety valves
Connections to gas (DN50) and liquid (DN25) transfer lines
Connection to purging valve
Connection to degassing tank
Flanges for condensing + subcooling coils
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Design parameters: Chiller (3/4)
Required power for 0.1 kW loop operation: around 2 kW @ -48 °C
2500
Power [W]
2000
1500
1000
500
0
13.4
8.2
-2.3
-13
-24.1
-29.7
-34.7
-48.6
Chiller operating temperature [°C]
Required chiller power with subcooling coil
Heat to remove from the fluid
Evaporation temperature
[°C]
+15
+10
0
-10
-20
-25
-30
-40
Condensation temperature
[°C]
13.4
8.2
-2.3
-13
-24.1
-29.7
-34.7
-48.6
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Design parameters: Chiller (4/4)
Required power for 2x 1 kW loop operation: around 12 kW @ -48 °C
14000
12000
Power [W]
10000
8000
6000
4000
2000
0
13.4
8.2
-2.3
-13
-24.1
-29.7
-34.7
-48.6
Chiller operating temperature [°C]
Required chiller power with subcooling coil
Heat to remove from the fluid
Evaporation temperature
[°C]
+15
+10
0
-10
-20
-25
-30
-40
Condensation temperature
[°C]
13.4
8.2
-2.3
-13
-24.1
-29.7
-34.7
-48.6
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Service requirements
 Surface
♦
♦
♦
♦
Water distribution
Electrical power (chiller + control system)
Compressed Air
Ethernet Network
 Cavern
♦ Electrical power (heaters + control system + test sections
evaporator)
♦ Compressed air
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Critical issues
 Low pressure in part of the system (return gas pipe + vessel)
 Very low leak rate requirements
 Avoid evaporation in the liquid line
 Avoid elbows on the pipes
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Status for test with blends (C3F8 / C2F6)
 Interests for a gravity driven cooling process
♦ Achieve higher pressure evaporation in the cooling loops
♦ Operate at higher pressure temperature in the surface
♦ Reach higher pressure at the bottom of the liquid column
 Nominal pressure of piping can remain the same (PN25)
 Instrumentation, valves and heaters can approximately
remain the same
 Issues (under study)
♦ Blend composition needs to be carefully monitored
♦ Additional instrumentation has to be installed
♦ Additional equipment to control the mixture composition
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Conclusion and Next steps
Gravity-driven cooling systems are appealing but the feasibility needs
to be demonstrated first and requires precise study and a high level
of materials quality
Next actions
 Build the 1:8 scale test facility in autumn to perform test with C3F8
 Finalize integration study
 Sharp component selection, and market survey for the large scale
system
 Preparation for project Readiness Review
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