1. CFD-Team Weekly Meeting - 8th March 2012
ITS Upgrade: Progress
M. Gomez Marzoa
CFD-Team Weekly Meeting - 8th March 2012

2. CFD-Team Weekly Meeting - 8th March 2012
Contents
St. Petersburg layout proposal
Layout
Cooling solution
Analytical assessment
Further analysis
EPG/Graphene + Carbon Fiber solutions
M. Gomez Marzoa
CFD-Team Weekly Meeting - 8th March 2012

3. St. Petersburg layout proposal
ALICE ITS Detector: 3 inner layers (Inner barrel) + 4 outer layers
Outer layers: double sided Si-strip detectors.
Inner barrel: Si MAPS Pixel detectors
Design requirements:
Material budget <0.5% x/X0 per Si layer
Innermost layers x/X0<0.3%
Accessibility
Focus on Inner barrel mechanical design.
M. Gomez Marzoa
CFD-Team Weekly Meeting - 8th March 2012

4. St. Petersburg layout proposal
Total per 3 layers: x/X0=0.94%
M. Gomez Marzoa
CFD-Team Weekly Meeting - 8th March 2012

5. St. Petersburg air cooling proposal
Air flow into the shells (100 µm) and out through small holes to Si sensors.
Air INLET
D=1.5 mm (variable)
H= mm (variable)
Si sensor ~ 50 µm
Array of holes (OUTLET)
D=0.35 mm
M. Gomez Marzoa
CFD-Team Weekly Meeting - 8th March 2012

6. St. Petersburg air cooling proposal
Detector Thermal requirements:
Si MAPS working temperature = 30 C
Power density = W/cm2
TAIR-INLET = +14 C (minimum +7 C – dew point)
St. Petersburg cooling estimations:
TAIR-INLET = +14 C
Air volumetric flow rate = l/s
PGAUGE = bar
HTC ~ 200 [W/m2 K] (??)
M. Gomez Marzoa
CFD-Team Weekly Meeting - 8th March 2012

7. St. Petersburg proposal analysis
Detector Thermal requirements:
Si MAPS working temperature = 30 C
Power density = W/cm2
TAIR-INLET = +14 C (minimum +7 C – dew point)
HTC_Needed [W/m^2 K]
q [W/cm^2]
0.25
0.3
0.4
0.5
T_Inlet [K] 7
108.7
130.4
173.9
217.4 10
125
150
200
250 14
156.3
187.5
312.5
M. Gomez Marzoa
CFD-Team Weekly Meeting - 8th March 2012

8. St. Petersburg proposal analysis
Cooling solution can be modeled as an array of impinging jets:
Empirical correlations for round nozzle (single or array): Martin [1], Popiel [2], Goldstein [3] L D r L S
M. Gomez Marzoa
CFD-Team Weekly Meeting - 8th March 2012

9. St. Petersburg proposal analysis
Considering:
Input Volumetric flow rate = 0.8 l/s
Number of nozzles = 142 (1st layer) +142 (2nd) (3rd) = 444
Assuming uniform distribution of air among every nozzle.
Velocity at each hole = 4.93 m/s
H=0.3 mm (best case), D=0.35 mm, S = mm
Ranges of validity of correlations:
Re = 110 (Out of range)
H/D = (Out of range)
A_r = (Out of range)
Applying correlations h_Av ~ 90 W/m2 K
M. Gomez Marzoa
CFD-Team Weekly Meeting - 8th March 2012

10. St. Petersburg proposal analysis
Optimal geometrical settings for increasing Nu:
The optimal value:
matches approximately the length of the jet’ s potential core, region where local heat transfer coefficients achieve higher values.
M. Gomez Marzoa
CFD-Team Weekly Meeting - 8th March 2012

11. St. Petersburg proposal analysis
Additional issues:
Air is not distributed uniformly between all holes.
Sharp edge in nozzles – correlations are for smooth edge.
High pressure drop expected.
Forces over the Si MAPS sensor can break it (50 µm)
Conclusions:
Flow is laminar out of the nozzles.
Increasing the flow, controlling the pitch of the array, the spacing with the detector and the nozzle diameter could help to increase turbulence.
Look for some other correlations.
Perform a CFD simulation – difficulties predicting flow out of the nozzles (but could be a solution).
M. Gomez Marzoa
CFD-Team Weekly Meeting - 8th March 2012

12. CFD-Team Weekly Meeting - 8th March 2012
ITS Upgrade: Progress
M. Gomez Marzoa
CFD-Team Weekly Meeting - 8th March 2012