1. Wound-truss carbon fiber structures as a solution for cooling of silicon particle detectors
Corrado GARGIULO (CERN)
Claudio BORTOLIN (CERN)
Martin DOUBEK (CTU, Czech Technical University, Prague)
Andrea FRANCESCON (CERN)
Manuel GOMEZ MARZOA (CERN)
Romualdo SANTORO (CERN)
3th October 2012
M. Gomez Marzoa
6th September 2012

2. Contents Water tests: results Data post-processing
Two-Phase C4F10 tests
Discussion
Optimization
Design parameters
Stave calculations
Cooling fluid calculations
Cooling fluid considerations
DSF & Water chiller status
Research lines
M. Gomez Marzoa
6th September 2012

3. Water tests: results
M. Gomez Marzoa
6th September 2012

4. Data post-processing
D08 water tests -> Stave thermal resistance calculation
From Silicon to water, two thermal resistances can be defined:
Calculating thermal resistance of stave:
Water tests: recalculation of HTC:
RtConv
RtCond-Stave
Water
Silicon
Pipe inner wall Q
[L h-1]
P [W]
Re [-]
HTC
[W m-2 K]
Rt-conv-pred [K W-1]
ΔT-st-water [K]
Rt-stave
[K W-1]
Rt-conv-calc [K W-1]
HTC-recalc [W m-1 K]
ΔT-pipe-water [K] 3
12.14
652
1920
0.209
13.1
0.867
0.196
2047.6
2.4 5
1086
13.4
0.890
0.219
1829.7
2.7 8
1738
13.0
0.858
0.186
2153.3
2.3
20.41
21.3
0.834
0.163
2466.9
3.3 12
12.33
2607
8051
0.050
12.2
0.943
0.112
3574.2
1.4
20.49
19.2
0.889
0.059
6822.1
1.2
Laminar & Gnielinski
Recalculated values
M. Gomez Marzoa
6th September 2012

5. Two-phase C4F10 tests: overview
Inlet vapor quality:
𝑥= 𝑚 𝑉𝑎𝑝𝑜𝑟 𝑚 𝐿𝑖𝑞 = ℎ 2 − ℎ 𝐿𝑖𝑞 𝑆𝑎𝑡 ​ 𝑝 2 ℎ 𝑉𝑎𝑝 𝑆𝑎𝑡 ​ 𝑝 2 − ℎ 𝐿𝑖𝑞 𝑆𝑎𝑡 ​ 𝑝 2
Superheating at stave outlet:
Δ 𝑇 𝑆𝑢𝑝𝑒𝑟ℎ𝑒𝑎𝑡𝑖𝑛𝑔 = 𝑇 4 − 𝑇 3 ′
T = const
x = const
Mass flow rate calculation:
𝑚 = 𝑄 𝐿 Δ 𝑥 2−3 1
𝑄 = 𝑚 𝐿 Δ 𝑥 2−3 ;
p [bar]
where L is latent heat [kJ kg-1]: 3
𝐿= ℎ 𝑉𝑎𝑝 𝑆𝑎𝑡 − ℎ 𝐿𝑖𝑞 𝑆𝑎𝑡 3’ 2 4
Usually:
Qstave [W]
Δ 𝑥 𝐸𝑣𝑎𝑝 <0.5
0.2< 𝑥 𝐸𝑣𝑎𝑝 𝐼𝑛 <0.3
𝑥 𝐷𝑟𝑦𝑜𝑢𝑡 ~ 0.8 ÷0.9
h [kJ kg-1]
M. Gomez Marzoa
6th September 2012

6. Evaporative cooling system performs as good as single-phase water
D08: water vs. W cm-2
Water
Q [L h-1]
ΔpSt [bar] v
[m s-1]
TH20 [°C]
ΔTH20 [K]
ΔTHeater [K]
3.0
0.19
0.52
15.1
2.4
9.8
5.0
0.25
0.86
14.8
1.5
9.0
8.0
0.46
1.38
14.7
0.7
12.0
0.74
2.08
0.6
6.8
C4F10
m [g s-1]
xIn
xOut
TC4F10-Out [°C]
0.16
0.06
0.08
0.92
16.8
0.20
0.07
0.75
14.0
5.5
0.40
0.42
13.4
5.6
0.60
0.31
6.0
Evaporative cooling system performs as good as single-phase water
M. Gomez Marzoa
6th September 2012

7. D08: water vs. C4F10 @0.5 W cm-2 Water C4F10Q
[L h-1]
ΔpSt [bar] v
[m s-1]
TH20 [°C]
ΔTH20 [K]
ΔTHeater [K]
8.0
0.43
1.38
14.7
1.5
16.0
12.0
0.76
2.08
14.8
0.6
13.5
C4F10 m
[g s-1]
xIn
xOut
TC4F10-Out [°C]
0.4
0.17
0.06
0.65
13.4
13.0
0.26
0.05
0.46
14.0
0.8
0.33
0.03
0.36
14.5
Results independent of the mass flow rates.
Controlling the vapor quality at the inlet/outlet is very important.
Almost subcooled liquid at the stave inlet!
M. Gomez Marzoa
6th September 2012

8. D08: C4F10 tests discussion Two cases did not perform as expected:
Case: 0.3 W cm-2 m
[g s-1]
ΔpSt [bar]
xIn
[m s-1]
xOut
TC4F10-Out [°C]
ΔTHeater [K]
0.8
0.28
0.04
0.26
13.3
14.0
Low vapor quality at the stave entrance: subcooled liquid entering stave?
ꜛ m, ꜛ HTC, but ꜛΔp. Since pOut = constant, ꜛpInlet, ꜛTsat-Inlet, ꜛΔTFluid
Case: 0.5 W cm-2 m
[g s-1]
ΔpSt [bar]
xIn
[m s-1]
xOut
TC4F10-Out [°C]
ΔTHeater [K]
0.2
0.09
0.08
1.20
21.0
28.0
Low vapor quality at the stave entrance: saturated liquid entering stave?
Mass flow rate too low: superheated vapor at stave outlet
M. Gomez Marzoa
6th September 2012

9. Data post-processing
D08 C4F10 tests: HTC prediction and flow characterization
Pool boiling or convective boiling?
C4F10
T_sat [°C] 15
p_sat [bar]
1.9
0.3 W cm-2 m
[g s-1] G
[kg m-2 s-1]
xAverage [-]
hCooper-PB
[W m-2 K-1]*
hLiuWinterton
RtConv-Stave [K W-1]
hCalculated
[W m-2 K-1]
0.2
125
0.42
603
1618
0.32
1290
0.4
250
0.25
2257
0.36
1132
0.6
370
0.18
2845
0.29
1437
0.8
500
0.15
3238
1407
0.5 W cm-2 m
[g s-1] G
[kg m-2 s-1]
xAverage [-]
hCooper-PB
[W m-2 K-1]*
hLiuWinterton
[W m-2 K-1]
RtConv-Stave [K W-1]
hCalculated
0.4
250
0.30
1005
2499
0.57
2664
0.6
370
0.20
2921
0.04
3031
0.8
500
0.15
3330
0.27
3550
*Assumed smooth pipe. For correlations, power is assumed to be distributed uniformly around the cooling pipe.
Used Cooper (1984) and Liu-Winterton (1991) correlations for HTC.
M. Gomez Marzoa
6th September 2012

10. Design parameters Preliminary calculations: Heat transfer path: Stave:
Si-glue
Glue-wrapping CF
Wrapping CF-CF sleeve
Heat distribution within CF sleeve
CF sleeve-cooling pipe
Cooling pipe-fluid 5 4 6 2 3 1
Materials (with Mechanics group):
Carbon Fiber:
Wrap fiber: K13D-2U CF: kFiber ~ 450 W m-1 K-1 ; kTransv ~ 1.2 W m-1 K-1
Carbon Paper: kFiber ~ 1000 W m-1 K-1 ; kTransv ~ 1.2 W m-1 K-1
Glue: k ~ 1 W m-1 K-1
Pipe (Polyimide): k= 0.12 W m-1 K-1 , OD = 1.5 mm, wall 35 µm thick
Silicon: k = 150 W m-1 K-1
M. Gomez Marzoa
6th September 2012

11. Table of initial D08 geometrical parameters.
Design parameters
Analysis of different scenarios were carried out, changing structural parameters:
Parameter
Value
Pipe OD [mm]
1.5
Pipe thickness [mm]
0.035
Pipe ID [mm]
1.43
Carbon paper sleeve thick tcs [mm]
0.03
CF tangential coverage β [deg]
~ 360
Wrapping CF thickness tCF [mm]
0.07
Pitch p+w [mm]
~ 4.5
Fiber width w [mm]
p [mm]
~ 3
Angle fiber with pipe axis α [deg] 23
Stave width wStave [mm]
~ 17
Stave height hStave [mm] 5
CF HC Plate thickness [mm]
Comments:
7.5 mm pitch (data) corresponds to ~ 35 fibers
But in D08 prototype, 54 fibers were counted.
This corresponds to a pitch of ~ 4.5 mm
Influence on the CFD simulations (where a 7.5 mm pitch was taken into consideration)
Table of initial D08 geometrical parameters.
M. Gomez Marzoa
6th September 2012

12. Stave calculations
0. D08 prototype
Decrease stave width to 15.5 mm
Increase CF width to 1.75 mm
Increase CF width to 1.90 mm
Increase CF thickness to 100 µm
Decrease number of fibers to 40
Increase wrap angle to 40 deg
Increase wrap angle to 60 deg
Increase glue thickness to 200 µm and decrease its th. cond. to 0.5 W m-1 K-1
Increase pipe outer diameter to 2.5 mm
New prototype (not tested yet)
Strategy: estimate the ΔT that every part of the structure will introduce.
Case
h-stave [mm]
w-st [mm]
Fiber w [mm]
Fiber thick [mm]
N-fibers [mm]
Wrap angle α [deg]
Glue thick [mm]
Glue k
[W m-1 K-1]
Sleeve thick [mm] OD
[mm] ID 5
16.3
1.50
0.07 54 23
0.1
1.0
0.03
1.5
1.43 1
15.0 2
1.75 3
1.90 4
0.10 40
0.2
0.5 6 7 60 8 9
2.5
2.37 10 15
0.93
M. Gomez Marzoa
6th September 2012

13. Stave calculations Silicon to glue and crossing
Assumption: heat only crosses transversally glue.
BEST:
Reduce thickness.
Use high k glue (TIMs, Th. Grease)
Little influence in the global ΔT.
Case
Fiber w [mm]
N-fibers [mm]
Wrap angle α [deg]
Glue thickness [mm]
Glue Th. Cond
[W m-1 K-1]
ΔTGlue [K]
1.50 54 23
0.1
1.0
0.4 1 2
1.75
0.3 3
1.90 4 5 40
0.2
0.5 6
0.6 7 60
0.9 8
1.6 9 10
q' [W cm-2]
0.3
Stave length [mm]
270
Silicon width [mm] 15
Glue
Araldyte
k [W m-1 K.1]
1.0
M. Gomez Marzoa
6th September 2012

14. Stave calculations Glue into carbon fiber
Most important contribution to global ΔT
ΔT glue-fiber + ΔT fiber
BEST:
Increase wrap angle (no ꜛx/X0)
Increase fiber width and thickness (but ꜛx/X0)
Case
w-st [mm]
Fiber w [mm]
Fiber thick [mm]
N-fibers [mm]
Wrap angle α [deg]
ΔTFiber [K]
ΔTFiber-Si-pipe [K]
16.3
1.50
0.07 54 23
22.9
4.0 1
15.0
0.0 2
1.75
19.6
3.4 3
1.90
18.0
1.2 4
0.10
16.0
2.8 5 40
30.8
5.4 6
13.9
2.4 7 60
10.3
1.8 8 9 10
q' [W cm-2]
0.3
Stave length [mm]
270
Silicon width [mm] 15
Carbon fiber
K13 D 2U
kHigh [W m-1 K.1]
450
kLow [W m-1 K.1]
1.2
M. Gomez Marzoa
6th September 2012

15. Power density at wrapping surface [W cm-2]
Stave calculations
Wrapping fiber into pipe carbon paper sleeve
Assumption: heat uniformly distributed angularly.
Target: decrease W cm-2 at interface fiber/sleeve
BEST: increase pipe diameter (but ꜛ x/X0)
q' [W cm-2]
0.3
Stave length [mm]
270
Silicon width [mm] 15
Carbon fiber
K13 D 2U
kHigh [W m-1 K.1]
450
kLow [W m-1 K.1]
1.2
Case
h-st [mm]
w-st [mm]
Fiber w [mm]
Fiber t [mm]
N-fibers [mm]
Wrap angle α [deg]
Sleeve thick [mm] OD
[mm] ID
Power density at wrapping surface [W cm-2]
ΔTRadial [K] 5
16.3
1.50
0.07 54 23
0.03
1.5
1.43
1.40
0.8 1
15.0
1.42 2
1.75
1.20
0.7 3
1.90
1.10
0.6 4
0.10
1.2 40
1.88
1.1 6
2.30
1.3 7 60
3.09
1.8 8 9
2.5
2.37
0.81
0.5 10 15
0.1
1.0
0.93
2.15
M. Gomez Marzoa
6th September 2012

16. Stave calculations Heat distribution within CF sleeve
Assumption 1: heat transferred axially within the sleeve in the space between fibers.
BEST: increase number of fibers and fiber width.
Case
h-stave [mm]
w-st [mm]
Fiber w [mm]
N-fibers [mm]
Wrap angle α [deg]
Sleeve thick [mm] OD
[mm] ID
ΔTAxial [K] 5
16.3
1.50 54 23
0.03
1.5
1.43
2.1 1
15.0
2.2 2
1.75
1.0 3
1.90
0.3 4 40
7.2 6
4.9 7 60
6.0 8 9
2.5
2.37
1.2 10
0.93
3.3
q' [W cm-2]
0.3
Stave length [mm]
270
Silicon width [mm] 15
Sleeve material
Carbon Paper
kHigh [W m-1 K.1]
1000
kLow [W m-1 K.1]
1.2
M. Gomez Marzoa
6th September 2012

17. Stave calculations Heat distribution within CF sleeve
Assumption 2: heat radially across sleeve thickness
Thickness is small, does not influence ΔTGlobal
Case
h-stave [mm]
w-st [mm]
Fiber w [mm]
N-fibers [mm]
Wrap angle α [deg]
Sleeve thick [mm] OD
[mm] ID
ΔTSleeve [K] 5
16.3
1.50 54 23
0.03
1.5
1.43
0.3 1
15.0 2
1.75 3
1.90 4 40 6 7 60 8 9
2.5
2.37
0.2 10
1.0
0.93
0.4
q' [W cm-2]
0.3
Stave length [mm]
270
Silicon width [mm] 15
Sleeve material
Carbon Paper
kHigh [W m-1 K.1]
1000
kLow [W m-1 K.1]
1.2
M. Gomez Marzoa
6th September 2012

18. Stave calculations Across cooling pipe radially:
Does not play a big role in the ΔTGlobal
Depending on the pipe size, material and wall thickness, ΔT could increase or decrease.
Evaluate different materials.
Case
h-stave [mm]
w-st [mm]
Sleeve thick [mm] OD
[mm] ID
ΔTAcross-pipe [K] 5
16.3
0.03
1.5
1.43
3.3 1
15.0
3.4 2 3 4 6 7 8 9
2.5
2.37
3.6 10 15
1.0
0.93
5.3
q' [W cm-2]
0.3
Stave length [mm]
270
Silicon width [mm] 15
Pipe material
Polyimide
k [W m-1 K.1]
0.12
M. Gomez Marzoa
6th September 2012

19. Stave calculations: conclusion
0. D08 prototype
Decrease stave width to 15.5 mm
Increase CF width to 1.75 mm
Increase CF width to 1.90 mm
Increase CF thickness to 100 µm
Decrease number of fibers to 40
Increase wrap angle to 40 deg
Increase wrap angle to 60 deg
Increase glue thickness to 200 µm and decrease its th. cond. to 0.5 W m-1 K-1
Increase pipe outer diameter to 2.5 mm
New prototype (not tested yet)
Case
ΔTGlue [K]
ΔTFiber [K]
ΔTFiber-Si-pipe [K]
ΔTRadial [K]
ΔTSleeve-axial [K]
ΔTSleeve-Rad [K]
ΔTAcross-pipe [K]
ΔTGlobal
[K]
0.4
22.9
4.0
0.8
2.1
0.3
3.3
33.8 1
0.0
2.2
3.4
30.0 2
19.6
0.7
1.0
28.6 3
18.0
1.2
0.6
24.0 4
16.0
2.8
26.1 5
0.5
30.8
5.4
1.1
7.2
48.6 6
13.9
2.4
1.3
4.9
26.7 7
0.9
5.2
1.8
6.0
18.4 8
1.6
35.0 9
0.2
3.6
32.8 10
5.3
27.2
M. Gomez Marzoa
6th September 2012

20. Cooling fluid calculations
Convection pipe wall-fluid:
Several HTCs considered
Stave height = 5 mm, fiber wrap angle = 23 deg
Heat transfer area inner pipe wall only below 180-η angle at sleeve.
Case
OD [mm]
ID [mm]
Power half stave [W]
Pipe coverage (180-η) [deg]
Pipe-area for heat transfer [mm2]
HTC
[W m-2 K-1]
ΔTPipe-Ref [°C]
1.5
1.43
6.075
154.28
519.8
1000
11.7 1
2000
5.8 2
5000
2.3 3
8000 4
10000
1.2 5
2.0
1.93
161.77
735.6
8.3 6
4.1 7
1.7 8
1.0
0.93
147.46
323.1
18.8 9
9.4 10
3.8
q' [W cm-2]
0.3
Stave L [mm]
270
Si width [mm] 15
HTC variation
Increase pipe section
Decrease pipe section
M. Gomez Marzoa
6th September 2012

21. Stave optimization Stave: Improvements without increasing mat. budget:
Reduce stave thickness to 15 mm
Increase wrap angle (eventually, use High Conductivity Plate)
Improvements increasing mat. budget:
Increase CF width
Increase carbon fiber thickness
Cooling fluid:
Increasing pipe diameter reduces ΔTPipe-Ref , but increases mat. budget (espec. single phase)
Little improvement when increasing HTC pipe-fluid
Further considerations:
Single-phase or Two-Phase?
Fluid?
M. Gomez Marzoa
6th September 2012

22. Fluid considerations Single-Phase cooling:
+ Simple and capable (D06 prototype)
- Bigger material budget
Pressure drop considerations
Leaks: fluid considerations
Fluids:
Water (leak-less system OR no connectors inside detector). X0=36 cm
C6F14: dielectric. X0=21.8 cm
Two-Phase cooling:
+ Stable and robust once tuned
+ Low material budget thanks to the void fraction
- Distribution among staves can be an issue
C4F10: could be difficult to acquire in the future. X0(L)=21.8 cm
M. Gomez Marzoa
6th September 2012

23. DSF & Water chiller: status
DSF water circuit:
Pressure oscillations at the return (on Friday 28th September): 2.5 to 2.7 bar (with and without stave).
Influence over turbulence in the flow.
Deactivate low-level alarm and let water
Independent water chiller:
Possible borrowing idle chiller for limited time.
Fine flow rate and temperature control
Maximum pressure drop ~ 3 bar.
Vic Vacek: has plant available at CERN
M. Gomez Marzoa
6th September 2012

24. Research lines
In the framework of the ALICE ITS Upgrade, some proposals for research lines:
Study the dependence of the pipe material and rugosity on the boiling process with different fluids.
Characterize flow regime
Develop test section with flow visualization where the single channel for tests can be easily changed (account for different pipe materials)
Flow pattern characterization for C4F10
Possible borrowing IR camera calibrated at EPFL-LTCM . Also a High- Speed camera. Precision of around °C.
Once the HTC is determined locally along the whole stave, calculations could be done taking the HTC as an input (boundary condition). A complete set of points could be predicted.
CFD Boiling simulations (Fluent):
Experimental data from tests and literature as validation.
CFD Team hardware and support
M. Gomez Marzoa
6th September 2012

25. Best case simulated: silicon temperature map.
Prototype simulation
CFD Model:
Symmetric (only a sector of stave modeled)
Imposed HTC fluid-wall at the pipe inner wall. HTC = 1650 W m-2 K-1
Results shown for Twater = 15 °C and q’ = 0.3 W cm-2
Geometry views.
Best case simulated: silicon temperature map.
M. Gomez Marzoa
6th September 2012

26. Wound-truss carbon fiber structures as a solution for cooling of silicon particle detectors
Corrado GARGIULO (CERN)
Claudio BORTOLIN (CERN)
Martin DOUBEK (CTU, Czech Technical University, Prague)
Andrea FRANCESCON (CERN)
Manuel GOMEZ MARZOA (CERN)
Romualdo SANTORO (CERN)
3th October 2012
M. Gomez Marzoa
6th September 2012