PSB-Dump: first CFD simulations

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

2. Contents • Studied case overview • CFD Model: • Geometry • Mesh • Setup • Running conditions • Results • Conclusion 13th December 2012

3. 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 13th December 2012

4. CFD model: geometry PSB Dump Beam pipe Air duct Full geometry: symmetry applied in the model 8 L min-1, 0.5 W cm-2 PSB Dump PSB Dump Beam pipe Duct-main volume junction. Beam pipe separated 1 cm from dump. 13th December 2012

5. CFD model: mesh Main air volume PSB Dump Beam pipe Duct Front end of the PSB Dump. Duct-main volume junction mesh. Main mesh features: Regular mesh in ducts and cylindrical volumes, where possible (extruded). Tetrahedral mesh for the dump solid, the rear air volume and the duct junctions. Boundary layers + standard wall function enabled. 8.7*105 cells. Cell skewness can be problematic at pipe junction. 8 L min-1, 0.5 W cm-2 13th December 2012

6. CFD model: setup Energy source term: Use Fluent UDFs to set the values as energy source term FLUKA file: 24M cells Set it as a Fluent interpolation file Interpolate it in Fluent Reorder Gev/cm3/particle W/m3 Run simulation • Models: • Turbulence: Standard k-ε. • Wall treatment: standard wall function. • Gravity accounted. • Solver: steady-state, pressure-based, SIMPLE pressure-velocity coupling. • 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. 13th December 2012

7. 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 13th December 2012

8. CFD results: temperature Top is slightly warmer Gravity vector PSB Dump T map [°C] from back end: influence of gravity PSB Dump T map [°C] from front end. Av_Static_T (K) ----------------------- inlet 293 pres-outlet 315.4 --------------- Net 304.2 Expected ΔT (analytical) = 15 K with 2000 m3 h-1 • PSB Dump volume average T [°C]: • Analytical = 220 °C • CFD = 210 °C CFD: ΔTAverage= 22.4 K with 1800 m3 h-1 13th December 2012

9. 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 % 13th December 2012

10. 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. 13th December 2012

11. CFD results: air pressure • Main pressure drop happens at the ducts, as expected. Airflow gauge pressure at symmetry plane [Pa]. Airflow gauge pressure at the wall [Pa]. • 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 pres. at duct central plane [Pa]. 13th December 2012

12. 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! 13th December 2012

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