E. Da Riva/M. Gomez Marzoa 1WG4 Meeting - 27th June 2012

Air Cooling by means of carbon fiber

structure

Enrico DA RIVA (EN-CV-PJ)

Manuel GOMEZ MARZOA (EN-CV-PJ)

27th June 2012

E. Da Riva/M. Gomez Marzoa 2WG4 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 performance2. A two-layer model of the ITS Barrel

E. Da Riva/M. Gomez Marzoa 3WG4 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: Tair Inlet = 14 °C vInlet

q’Silicon

IN

OUT

Si sensor 268 mm

15 mm

E. Da Riva/M. Gomez Marzoa 4WG4 Meeting - 27th June 2012

Single stave: CFD Analysis0.3 W cm-2, 10 m s-1

Temperature CF [°C]

Temperature silicon [°C]

Tmax = 60 °C

E. Da Riva/M. Gomez Marzoa 5WG4 Meeting - 27th June 2012

0.3 W cm-2, 20 m s-1

Single stave: CFD Analysis

Temperature sensor [°C]

Temperature stave [°C]

Tmax = 43 °C

E. Da Riva/M. Gomez Marzoa 6WG4 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

Tmax = 30 °C

E. Da Riva/M. Gomez Marzoa 7WG4 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

E. Da Riva/M. Gomez Marzoa 8WG4 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)

kPlanar = 400 W m-1 K-1

kTransv = 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: vInlet = 10 m s-1

q’Sensor = 0.3 W cm-2

Tair Inlet = 14 °C

E. Da Riva/M. Gomez Marzoa 9WG4 Meeting - 27th June 2012

Two-layer model: CFD study0.3 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

E. Da Riva/M. Gomez Marzoa 10WG4 Meeting - 27th June 2012

Two-layer model: CFD study0.3 W cm-2, 10 m s-1

Temperature silicon L1 [°C] Temperature silicon L2 [°C]

E. Da Riva/M. Gomez Marzoa 11WG4 Meeting - 27th June 2012

Two-layer model: CFD study0.3 W cm-2, 10 m s-1

Heat flux silicon in triangle L2 [W/m2] Heat flux to outlet L2 [W/m2]

E. Da Riva/M. Gomez Marzoa 12WG4 Meeting - 27th June 2012

Two-layer model: CFD study0.3 W cm-2, 10 m s-1

Temperature CF stave L1 [°C]

E. Da Riva/M. Gomez Marzoa 13WG4 Meeting - 27th June 2012

Outcome The silicon is only cooled with the air flow inside the triangular duct, because voutlet

duct is small. Possible solutions:

1. Increase air velocity Vibration & shear stress increase

2. Equalize inlet/outlet sections: guarantee high velocity at outlet ducts3. 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] 10 20Re 2401 4802

Flow Transitional Turbulent

Umean [m s-1] 20 30 40Re 616 924 1232

Flow Laminar Laminar Laminar

AIR

HELIUM

E. Da Riva/M. Gomez Marzoa 14WG4 Meeting - 27th June 2012

Outcome The silicon is only cooled with the air flow inside the triangular duct, because voutlet

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 guaranteedSolution to be used for low q’

Umean [m s-1] 10 20Re 2401 4802

Flow Transitional Turbulent

Umean [m s-1] 20 30 40Re 616 924 1232

Flow Laminar Laminar Laminar

AIR

HELIUM

E. Da Riva/M. Gomez Marzoa 15WG4 Meeting - 27th June 2012

Enrico DA RIVA (EN-CV-PJ)

Manuel GOMEZ MARZOA (EN-CV-PJ)

27th June 2012

Air Cooling by means of carbon fiber

structure