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PSB-Dump: first CFD simulations

This study presents the CFD simulations of the PSB dump, analyzing pressure drop, heat dissipation, and comparing results with analytical calculations. Further steps include considering radiative heat transfer, different dump shapes, reducing pressure drop, and adding fins for better heat transfer.

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PSB-Dump: first CFD simulations

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  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

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