cfd model setup & boundary conditions

PSB Dump air coolingResults with:1. Flat dump without fins 2. Fins ‘5 mm – 10 mm – 10 mm’ 3. Fins ‘5 mm – 10 mm – 20 mm’4. Fins ‘5 mm – 25 mm – 20 mm’5. Fins ‘5 mm – 25 mm – 50 mm’

2013-02-07 E. Da Riva, M. Gomez Marzoa 1

Contents

1. Set-up and geometry

2. Pressure drop with “smooth” and “sharp” connection

3. Temperature results with different fins geometries

4. Some detailed results

2013-02-07 E. Da Riva, M. Gomez Marzoa 2

CFD model setup & boundary conditions

E. Da Riva, M. Gomez Marzoa2013-02-07

Air flow and heat transfer in the fluid and solid solved all together in a single simulation.

Steady-state simulation.

Turbulence model : Standard k-ε + standard wall functions.

Gravity and buoyancy taken into account (even if not really relevant in this case).

Dependence of air conductivity, viscosity and constant heat on temperature taken into account.

Thermal conductivity of copper C18150: 320 W m-1 K-1 (temperature independent).

Inlet flow rate: 1800 m3 h-1 (→ 15 K air temperature rise, 12.5 m/s air velocity in the ducts).

Air injected from the ducts.

Air temperature at inlet: 20 °C. Energy deposition inside the dump: imported from FLUKA file (~9500 W).

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CFD model: geometry

E. Da Riva, M. Gomez Marzoa2013-02-07

8 L min-1, 0.5 W cm-2

Beam pipe separated 1 cm from dump.

Full geometry: symmetry applied in the model

PSB DumpBeam pipe

Air duct

Beam pipe PSB Dump

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Duct connection geometry

E. Da Riva, M. Gomez Marzoa2013-02-07

2 geometries considered in the CFD simulations:

150 mm internal diameter 150 mm bending radius

PSB Dump

A. “smooth connection” B. “sharp connection”

159 mm i.d. for both duct & connection

Actual geometry from CATIA model:

~160 mm i.d. for the duct ~150 mm i.d. for the connection Inner surface of the duct end rounded

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Pressure drop results

E. Da Riva, M. Gomez Marzoa2013-02-07

A. “Smooth connection” B. “Sharp connection”

Geometry Flow rate Pressure drop“Smooth connection” (no fins) 2000 m3 h-1 152 Pa

“Smooth connection” (no fins)

1800 m3 h-1

125 Pa

“Sharp connection” (5-10-10 fins) 232 Pa

“Sharp connection” (5-10-20 fins) 240 Pa

“Sharp connection” (5-25-20 fins) 220 Pa

“Sharp connection” (5-25-50 fins) 271 Pa

Gauge pressure at 1800 m3 h-1 [Pa].

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Energy deposition

E. Da Riva, M. Gomez Marzoa2013-02-07

Heat generation inside the dump imported from FLUKA file: ~9450 W total power.

Energy deposition in the dump [W m-3].

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Fins geometry

E. Da Riva, M. Gomez Marzoa2013-02-07

The solution of “thin fins” brazed on the dump is neglected because of manufacturing consideration.

Only “bulky fins” machined on the dump cylinder are taken into considerations Diameter of dump: 400 mm at the foot of the fins. 3 different dump surfaces simulated:

Dump surface

Fin thickness

Gap between 2 fins available for air flow Fin height

1) Flat --

2) ‘5-10-10’ 5 mm 10 mm 10 mm

3) ‘5-10-20’ 5 mm 10 mm 20 mm

4) ‘5-25-20’ 5 mm 25 mm 20 mm

5) ‘5-25-50’ 5 mm 25 mm 50 mm

‘5-10-10’ fins. ‘5-10-20’ fins.

r = 200 mm

r = 220 mm

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‘5-25-20’ fins. ‘5-25-50’ fins.

CFD results: temperature

E. Da Riva, M. Gomez Marzoa2013-02-07

Dump surface Maximum T1) Flat 236°C2) ‘5-10-10’ 188°C3) ‘5-10-20’ 150°C4) ‘5-25-20’ 168°C5) ‘5-25-50’ 119°C

A. ‘no fins’ B. ‘5-10-10’ fins C. ‘5-10-20’ fins

Temperature at the symmetry plane [°C].

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D. ‘5-25-20’ fins E. ‘5-25-50’ fins

Detailed results for ‘5-10-20’ fins(aka ‘didactic fancy pictures’)

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Velocity (5-10-20 fins, 1800 m3h-1)

E. Da Riva, M. Gomez Marzoa2013-02-07

Velocity at the symmetry plane [m s-1].

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Temperature (5-10-20 fins, 1800 m3h-1)

E. Da Riva, M. Gomez Marzoa2013-02-07

Note that the air flowing between the fins is locally much warmer than the average out air temperature (35°C) → important to take into account the dependency of air properties on temperature.

Homogeneous temperature of fins → no problem of thermal fins efficiency (on copper side).

Temperature [°C] at 0.5 m from the front (hot) end of the dump.

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Temperature (5-25-20 fins, 1800 m3h-1)

E. Da Riva, M. Gomez Marzoa2013-02-07

Temperature [°C] at 0.5 m from the front (hot) end of the dump.

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Temperature (5-25-50 fins, 1800 m3h-1)

E. Da Riva, M. Gomez Marzoa2013-02-07

Temperature [°C] at 0.5 m from the front (hot) end of the dump.

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Velocity (5-10-20 fins, 1800 m3h-1)

E. Da Riva, M. Gomez Marzoa2013-02-07

The area available for the air flow between the dump (D=400 mm at the foot of fins) and the shielding (D=500 mm) is extremely important since it determines the air velocity and therefore the heat transfer coefficient.

Note that the air velocity in the gap between 2 fins is smaller than far away from the fins → the local heat transfer coefficient is reduced.

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Velocity (5-25-20 fins, 1800 m3h-1)

E. Da Riva, M. Gomez Marzoa2013-02-07

Increasing the gap between the fins, a more favorable velocity is locally achieved, however the total surface available for the heat transfer is reduced.

The geometry ‘5-25-20’ performs better than ‘5-10-10’ (168°C vs 188°C, same total area available). The geometry ‘5-10-20’ performs better than ‘5-25-20’ (150°C vs 168°C) because the higher total area

available is the dominating effect.

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Velocity (5-25-50 fins, 1800 m3h-1)

E. Da Riva, M. Gomez Marzoa2013-02-07

The area available for the air flow between the dump (D=400 mm at the foot of fins) and the shielding (D=500 mm) consists in closed ducts and the air flow is better exploited.

The ducts on the top display a higher velocity.

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Heat flux (5-10-20 fins, 1800 m3h-1)

E. Da Riva, M. Gomez Marzoa2013-02-07

Local heat flux [W m-2].

The highest heat flux is achieved at the top of the fins. The surface at the foot of fins is not ideally exploited because of the local reduced air velocity.

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Heat flux (5-25-20 fins, 1800 m3h-1)

E. Da Riva, M. Gomez Marzoa2013-02-07 19

Local heat flux [W m-2].

Heat flux (5-25-50 fins, 1800 m3h-1)

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Local heat flux [W m-2].