m. gomez marzoa1 13th december 2012 psb-dump: first cfd simulations enrico da riva manuel gomez...
TRANSCRIPT
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
13th December 2012 3M. Gomez Marzoa
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
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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
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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
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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
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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
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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
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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
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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
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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
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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