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Radio Frequency Cavity Air Cooling

Radio Frequency Cavity Air Cooling . General problem. New Radio Frequency cavity developed in BE dep. 2 coils dissipating 650W each by joule effect. Define cooling air mass flow to keep the coils colder than 80˚C. Improve cavity shape to reduce hotspots. Development time: about 1 month.

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Radio Frequency Cavity Air Cooling

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  1. Radio Frequency Cavity Air Cooling CFD team supports CERN development 19 May 2011

  2. General problem • New Radio Frequency cavity developed in BE dep. • 2 coils dissipating 650W each by joule effect. • Define cooling air mass flow to keep the coils colder than 80˚C. • Improve cavity shape to reduce hotspots. • Development time: about 1 month CFD team supports CERN development 19 May 2011

  3. Estimate mass flow in Nominal Conditions 90 mm 25 mm • Thermal conductivity of the rings: 7 W/(m °C) • Power dissipation per ring : 650 W continuous ≈1/r2 • Range of tested air mass flows: 0.1 - 0.5 kg/s 20 mm CFD team supports CERN development 19 May 2011

  4. Mesh and numerical models • Air: compressible ideal gas model • K-Ԑ Two Layers Turbulence model • Buoyant flow • Thermal conduction over the supports and the box are neglected • Gas domain • Core Polyhedral Mesh • 10 layers cells “boundary layer” • Extrusion on outlet side • Solid domain • Core Polyhedral Mesh CFD team supports CERN development 19 May 2011

  5. Nominal ConditionsRings temperature VS air mass flow Rings’ temperature for 0.3 kg/s case. CFD team supports CERN development 19 May 2011

  6. Flow at Nominal Conditions Velocity magnitude maps on middle section 0.3 kg/s case CFD team supports CERN development 19 May 2011

  7. Studied Modified Geometries Compromise between reducing pressure drop and making the most uniform the Heat transfer coefficient on the coils’ surfaces. V.3 V.4 V.5 V.6 V.7 CFD team supports CERN development 19 May 2011

  8. Case: 0.3kg/s V.3 V.4 V.5 V.6 V.7 CFD team supports CERN development 19 May 2011

  9. Temperature VS Pressure Drop CFD team supports CERN development 19 May 2011

  10. Final Cavity Layout Version 9 • From treated cases we learn that: • Coils’ supports interfere with air flow/heat transfer • No grills: lower pressure drop • Cavity corners have to be “closed” CFD team supports CERN development 19 May 2011

  11. HTC: lower absolute value but more uniform(depends only on air flow pattern – independent from solid properties) V.3 V.4 V.7 V.9 CFD team supports CERN development 19 May 2011

  12. Case: 0.3kg/s V.3 V.9 V.4 V.7 CFD team supports CERN development 19 May 2011

  13. CFD team supports CERN development 19 May 2011

  14. Conclusions Our first target was to estimate a mass flow able to guarantee T<80˚C: obtained with a mass flow of 0.3kg/s Secondly target was to uniform the HTC over the coils’ surface to prevent from hot-spots and lower the pressure drop across the system: between the studied geometries “version 9” is the best compromise between those conditions. Experimental test of the cavity are going to be performed in the next future to validate the cavity and the simulations. CFD team supports CERN development 19 May 2011

  15. Thank you for your attention! CFD team supports CERN development 19 May 2011

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