M. Gomez Marzoa1 13th December 2012 PSB-Dump: first CFD simulations Enrico DA RIVA Manuel GOMEZ MARZOA 13 th December 2012

Contents 13th December 20122M. Gomez Marzoa 1.Studied case overview 2.CFD Model:  Geometry  Mesh  Setup  Running conditions 3.Results 4.Conclusion

Studied case overview 13th December 20123M. 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 13th December 20124M. Gomez Marzoa 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 Beam pipe Air duct Beam pipe PSB Dump

CFD model: mesh 13th December 20125M. Gomez Marzoa 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 *10 5 cells. 5.Cell skewness can be problematic at pipe junction.

CFD model: setup 13th December 20126M. Gomez Marzoa FLUKA file: 24M cells Reorder 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/cm 3 /particleW/m 3 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 13th December 20127M. Gomez Marzoa  Initialization  Adjusting under-relaxation factors  Convergence assessment:  Mass balance: achieved with an accuracy of kg s -1  Energy balance: net (solid + air) = W  Over 4738 W dissipated at PSB Dump: % 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 m 3 h -1

CFD results: temperature 13th December 20128M. Gomez Marzoa 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 Net Expected ΔT (analytical) = 15 K with 2000 m 3 h -1 CFD: ΔT Average = 22.4 K with 1800 m 3 h -1 PSB Dump volume average T [°C]:  Analytical = 220 °C  CFD = 210 °C

CFD results: heat flux 13th December 20129M. Gomez Marzoa Total Heat Transfer Rate (W) beam-pipe 0 dump-wall inlet pres-outlet wall Net 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* = W Deviation between calculations < 0.5 %

CFD results: air velocity 13th December M. Gomez Marzoa 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 13th December M. Gomez Marzoa 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 pres-outlet Net Airflow gauge pressure at symmetry plane [Pa]. Airflow gauge pres. at duct central plane [Pa].

Conclusion 13th December M. Gomez Marzoa 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 Marzoa13 13th December 2012 PSB-Dump: first CFD simulations Enrico DA RIVA Manuel GOMEZ MARZOA 13 th December 2012