1. E. Da Riva/M. Gomez Marzoa1 WG4 Meeting - 27th June 2012 Air Cooling by means of carbon fiber structure Enrico DA RIVA (EN-CV-PJ) Manuel GOMEZ MARZOA (EN-CV-PJ) 27 th June 2012

2. E. Da Riva/M. Gomez Marzoa2 WG4 Meeting - 27th June 2012 Outline  Air cooling: unites cooling performance and material budget.  Triangular carbon fiber structure considered, using it for cooling.  Similar solution as the STAR experiment: 8 m s -1, 0.1 W cm -2  Advantages:  Simple cooling system  No extra material added  Disadvantages:  Adequate for low power densities  Restricted air velocity (vibrations)  Sensor temperature uniformity STAR Experiment Models studied by means of CFD: 1.Single stave: Thermal fin performance 2.A two-layer model of the ITS Barrel

3. E. Da Riva/M. Gomez Marzoa3 WG4 Meeting - 27th June 2012 Overview  Single stave: Thermal fin performance  Geometrical features:  CF: 130 µm thick  Si: 50 µm thick  Stave: 300 mm long  Material properties:  CF: k = 620 W m -1 K -1 (assumed to be isotropic)  Si: k = 150 W m -1 K -1  Boundary conditions:  T air Inlet = 14 °C  v Inlet  q’ Silicon IN OUT Si sensor 268 mm 15 mm

4. E. Da Riva/M. Gomez Marzoa4 WG4 Meeting - 27th June 2012 Single stave: CFD Analysis 0.3 W cm -2, 10 m s -1 Temperature CF [°C] Temperature silicon [°C] T max = 60 °C

5. E. Da Riva/M. Gomez Marzoa5 WG4 Meeting - 27th June 2012 0.3 W cm -2, 20 m s -1 Single stave: CFD Analysis Temperature sensor [°C] Temperature stave [°C] T max = 43 °C

6. E. Da Riva/M. Gomez Marzoa6 WG4 Meeting - 27th June 2012 Stave heat flux [W m -2 ] q’ = 0.3 W cm -2, 10 m s -1 Single stave: conclusions  Only the case with 0.1 W cm -2 and 10 m s -1 would fulfill the detector thermal requirements for a single stave  The behaviour of the stave as a thermal fin is seen  Thermal performance improved when cooling from both sides of the triangular shape. 0.1 W cm -2, 10 m s -1 T max = 30 °C

7. E. Da Riva/M. Gomez Marzoa7 WG4 Meeting - 27th June 2012 2. A two-layer model of the ITS Barrel:  Only a section including two triangular shapes was modeled  Assumed a 30 mm chamber at the barrel end as recirculation zone  Mesh: ~ 5 million cells  Turbulence model: SST k-ω, Low-Re corrections 30 mm L1 L2 Beam Pipe Two-layer model: description

8. E. Da Riva/M. Gomez Marzoa8 WG4 Meeting - 27th June 2012 Two-layer model: description  Sector of the ITS barrel was modeled by means of CFD  Two inlet ducts and one outlet per layer  Simplified geometry built from the mechanical CAD design  Total length stave: 300 mm (268 mm sensor) + recirculation region  Material properties:  CF: o T300 fabric (biaxial thermal conductivity)  k Planar = 400 W m -1 K -1  k Transv = 1.2 W m -1 K -1 o Thickness: 130 µm (triangles and separation layers)  Si: k = 150 W m -1 K -1  Boundary conditions:  v Inlet = 10 m s -1  q’ Sensor = 0.3 W cm -2  T air Inlet = 14 °C

9. E. Da Riva/M. Gomez Marzoa9 WG4 Meeting - 27th June 2012 Two-layer model: CFD study 0.3 W cm -2, 10 m s -1 Magnitude of air velocity in a plane along the volume [m s -1 ] Pressure drop: L1 = 325 Pa, L2 = 306.28 Pa

10. E. Da Riva/M. Gomez Marzoa10 WG4 Meeting - 27th June 2012 Two-layer model: CFD study 0.3 W cm -2, 10 m s -1 Temperature silicon L1 [°C] Temperature silicon L2 [°C]

11. E. Da Riva/M. Gomez Marzoa11 WG4 Meeting - 27th June 2012 Two-layer model: CFD study 0.3 W cm -2, 10 m s -1 Heat flux silicon in triangle L2 [W/m2]Heat flux to outlet L2 [W/m2]

12. E. Da Riva/M. Gomez Marzoa12 WG4 Meeting - 27th June 2012 Two-layer model: CFD study 0.3 W cm -2, 10 m s -1 Temperature CF stave L1 [ °C ]

13. E. Da Riva/M. Gomez Marzoa13 WG4 Meeting - 27th June 2012 Outcome  The silicon is only cooled with the air flow inside the triangular duct, because v outlet duct is small.  Possible solutions: 1.Increase air velocity  Vibration & shear stress increase 2.Equalize inlet/outlet sections: guarantee high velocity at outlet ducts 3.Use different cooling fluid  Laminar flow and small molecule: no stresses over mechanical structure  Still, cooling from both sides of the sensor has to be guaranteed Umean [m s -1 ]1020 Re24014802 FlowTransitionalTurbulent Umean [m s -1 ]203040 Re6169241232 FlowLaminar AIR HELIUM

14. E. Da Riva/M. Gomez Marzoa14 WG4 Meeting - 27th June 2012 Outcome  The silicon is only cooled with the air flow inside the triangular duct, because v outlet duct is small.  Possible solutions: 1.Increase air velocity  Vibration & shear stress increase 2.Equalize inlet/outlet sections: guarantee high velocity at outlet ducts 3.Use different cooling fluid  Laminar flow and small molecule: no stresses over mechanical structure  Still, cooling from both sides of the sensor has to be guaranteed Solution to be used for low q’ Umean [m s -1 ]1020 Re24014802 FlowTransitionalTurbulent Umean [m s -1 ]203040 Re6169241232 FlowLaminar AIR HELIUM

15. E. Da Riva/M. Gomez Marzoa15 WG4 Meeting - 27th June 2012 Enrico DA RIVA (EN-CV-PJ) Manuel GOMEZ MARZOA (EN-CV-PJ) 27 th June 2012 Air Cooling by means of carbon fiber structure