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

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

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

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

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=0.2-0.3 mm (variable) Si sensor ~ 50 µm Array of holes (OUTLET) D=0.35 mm M. Gomez Marzoa CFD-Team Weekly Meeting - 8th March 2012

St. Petersburg air cooling proposal Detector Thermal requirements: Si MAPS working temperature = 30 C Power density = 0.25-0.5 W/cm2 TAIR-INLET = +14 C (minimum +7 C – dew point) St. Petersburg cooling estimations: TAIR-INLET = +14 C Air volumetric flow rate = 0.8-1.2 l/s PGAUGE = 0.05-0.1 bar HTC ~ 200 [W/m2 K] (??) M. Gomez Marzoa CFD-Team Weekly Meeting - 8th March 2012

St. Petersburg proposal analysis Detector Thermal requirements: Si MAPS working temperature = 30 C Power density = 0.25-0.5 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

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

St. Petersburg proposal analysis Considering: Input Volumetric flow rate = 0.8 l/s Number of nozzles = 142 (1st layer) +142 (2nd) + 160 (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 = 7.071 mm Ranges of validity of correlations:   Re = 110 (Out of range) H/D = 0.857 (Out of range) A_r = 0.0019 (Out of range) Applying correlations h_Av ~ 90 W/m2 K     M. Gomez Marzoa CFD-Team Weekly Meeting - 8th March 2012

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

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

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