m. gomez marzoa1 13th december 2012 psb-dump: first cfd simulations enrico da riva manuel gomez...

M. Gomez Marzoa 113th December 2012

PSB-Dump: first CFD simulations

Enrico DA RIVA

Manuel GOMEZ MARZOA

13th December 2012

Contents

13th December 2012 2M. Gomez Marzoa

1. Studied case overview

2. CFD Model:

Geometry

Mesh

Setup

Running conditions

3. Results

4. Conclusion

Studied case overview


Option 2: blow air out of the dump chamber from the ducts drilled in the shielding.

Keeps the whole volume of the sump under pressure, preventing from leaks.

Easier access to the ducts for placing the fans.

8 L min-1, 0.5 W cm-2

Symmetry plane

CFD model: geometry


8 L min-1, 0.5 W cm-2

Full geometry: symmetry applied in the model

Duct-main volume junction. Beam pipe separated 1 cm from dump.

PSB Dump

PSB Dump

Beam pipe

Air duct

Beam pipe PSB Dump

CFD model: mesh


8 L min-1, 0.5 W cm-2

Front end of the PSB Dump. Duct-main volume junction mesh.

Beam pipe

PSB Dump

Duct

Main air

volume

Main mesh features:

1. Regular mesh in ducts and cylindrical volumes, where possible (extruded).

2. Tetrahedral mesh for the dump solid, the rear air volume and the duct junctions.

3. Boundary layers + standard wall function enabled.

4. 8.7*105 cells.

5. Cell skewness can be problematic at pipe junction.

CFD model: setup


FLUKA file:

24M cellsReorder

Set it as a Fluent

interpolation file

Interpolate

it in Fluent

Use Fluent UDFs to

set the values as

energy source term

Run simulation

Gev/cm3/particle W/m3

Energy source term:

Boundary conditions:

Velocity inlet: 2.12 m s-1 : corresponding to a flow rate of 1800 m h-1

Air temperature at inlet: 20 °C

Pressure outlet.

Symmetry.

Shielding inner wall and beam pipe: adiabatic.

Models:

Turbulence: Standard k-ε.

Wall treatment: standard wall function.

Gravity accounted.

Solver: steady-state, pressure-based, SIMPLE pressure-velocity coupling.

Running the CFD model


Initialization

Adjusting under-relaxation factors

Convergence assessment:

Mass balance: achieved with an accuracy of 10-5 kg s-1

Energy balance: net (solid + air) = -0.19 W

Over 4738 W dissipated at PSB Dump: 0.004 % accuracy.

Monitors: average inlet pressure, average dump surface temperature, outlet mass flow

rate, heat flux through dump outer surface.

Solver: steady-state, pressure-based, SIMPLE pressure-velocity coupling.

Data validation:

Consider analytical calculation regarding pressure drop and dump average temperature:

~ 2000 m3 h-1

CFD results: temperature


PSB Dump T map [°C] from front end. PSB Dump T map [°C] from back end: influence of gravity

Top is slightly warmer

Gravity vector

Av_Static_T (K)----------------------- inlet 293 pres-outlet 315.4 --------------- Net 304.2

Expected ΔT

(analytical) = 15 K

with 2000 m3 h-1

CFD: ΔTAverage= 22.4 K

with 1800 m3 h-1

PSB Dump volume average T [°C]:

Analytical = 220 °C

CFD = 210 °C

CFD results: heat flux


Total Heat Transfer Rate (W)-------------------------------- -------------------- beam-pipe 0 dump-wall 4738.229 inlet -1091.2483 pres-outlet -3647.1692 wall 0 ---------------- -------------------- Net -0.18843226

PSB Dump outer wall heat flux map [W m-2], as seen from the dump front end.

Average power dissipated in Cu core

(FLUKA estimation) = 9433 W

CFD calculation = 2*4738.3 = 9476.6 W

Deviation between

calculations < 0.5 %

CFD results: air velocity


Air velocity magnitude map [m s-1] at the model

symmetry plane.

Air velocity magnitude map [m s-1] at the central plane of the duct.

CFD results: air pressure


Airflow gauge pressure at the wall [Pa].

Main pressure drop happens at

the ducts, as expected.

Air global Δp [bar]:

Analytical:

Main = 12 Pa

Duct = 80 Pa

CFD:

Global = 321 Pa

Mass-Weighted Av Static Pressure (pa)--------------------- --- inlet 321.22 pres-outlet 0 ------------- Net 160.61

Airflow gauge pressure at symmetry plane [Pa].

Airflow gauge pres. at duct central plane [Pa].

Conclusion


CFD simulation:

Importation from FLUKA is successful.

CFD matches the analytical calculations:

Pressure drop seems not to be the expected:

Singularities/junction?

Mesh not adequate?

Further steps:

CFD can provide a better insight when considering:

Radiative heat transfer to surrounding shielding: quantify heat dissipated.

Different dump shapes.

Heat transfer to the beam pipe.

Pressure drop reduction.

Adding fins: doubling the surface with fins can reduce dump T to almost half!

M. Gomez Marzoa 1313th December 2012

PSB-Dump: first CFD simulations

Enrico DA RIVA

Manuel GOMEZ MARZOA

13th December 2012

m. gomez marzoa1 13th december 2012 psb-dump: first cfd simulations enrico da riva manuel gomez...

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