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Slawomir Pietrowicz, Bertrand Baudouy CEA/IRFU/SACM January 20, 2011, SACLAY

EuCARD -HFM ESAC review of the high field dipole design Cooling , heat transfer and cool-down issues. Slawomir Pietrowicz, Bertrand Baudouy CEA/IRFU/SACM January 20, 2011, SACLAY. Outline. Modeling of thermal process in the magnet during ramp rate – 2 D steady state model

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Slawomir Pietrowicz, Bertrand Baudouy CEA/IRFU/SACM January 20, 2011, SACLAY

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  1. EuCARD-HFM ESAC review of the high field dipole designCooling, heat transfer and cool-down issues Slawomir Pietrowicz, Bertrand Baudouy CEA/IRFU/SACM January 20, 2011, SACLAY

  2. Outline • Modeling of thermal process in the magnet during ramp rate – 2 D steady state model • Geometry and applied mesh; • Properties of the materials; • Results - maximum temperature rise as a function of heat load. • Modeling of cool-down process – 2 D transient model • Indirect method from 300 k to 20 K – cool-down through cooling tubes • Assumptions and scenarios of cool-down used during calculations; • Results – maximum temperature rise as a function of time; • Direct method from 20 K to 4.2 K – direct filling with helium; • Scenario of cool-down used during calculations; • Results - maximum temperature rise as a function of time; • Estimation of maximum temperature rise of cooling helium. • Summary

  3. Modeling of thermal process in the magnet during ramp rate– 2 D steady state model • Geometry and applied mesh; • Properties of the materials; • Results - maximum temperature rise as a function of heat load. • Modeling of cool-down process – 2 D transient model • Indirect method from 300 k to 20 K – cool-down through cooling tubes - Assumptions and scenarios of cool-down used during calculations; - Results – maximum temperature rise as a function of time; • Direct method from 20 K to 4.2 K – direct filling with helium; - Scenario of cool-down used during calculations; - Results - maximum temperature rise as a function of time; • Estimation of maximum temperature rise of cooling helium. • Summary

  4. Modeling of thermal process in the magnet during ramping process – 2 D steady state model • Physical model • model of heat transfer used during simulations (steady state): • Assumptions • Two types of boundary conditions: • Constant temperature on walls (red lines); • Symmetry (yellow lines); • Thermal conductivity as function of temperature; • Perfect contact between solid elements; • 1 W, 5 W and 10 Wdissipated in conductors. For those values the homogenous spreadsof heat sources are used; • Calculations are carried out also for CUDI model (AC loss due to ISCC losses, non-homogenous spreads) • Calculations are performed for two bath (helium) temperature 1.9 K and 4.2 K Geometry and boundary conditions applied during simulations

  5. Modeling of thermal process in the magnet during ramp rate – 2 D steady state model Details of applied mesh Mesh – 715 k of structural elements

  6. Modeling of thermal process in the magnet during ramp rate – 2 D steady state model Source: Cryocomp Software v 3.06 Metalpak Software v 1.00

  7. Modeling of thermal process in the magnet ramp rate – 2 D steady state model The temperature contour map and localization of maximum temperature rise 4.2 K 1.9 K 1 W Homogenous spread of heat dissipation 5 W 10 W CUDI Model average 0.2 W

  8. Modeling of thermal process in the magnet during ramp rate – 2 D steady state model Maximum temperature difference in magnet at different temperature and heat load LHC Upgrade Temperature rise in the magnet as a function of unit heat load

  9. Modeling of thermal process in the magnet during ramp rate– 2 D steady state model • Geometry and applied mesh; • Properties of the materials; • Results - maximum temperature rise as a function of heat load. • Modeling of cool-down process – 2 D transient model • Indirect method from 300 k to 20 K – cool-down through cooling tubes - Assumptions and scenarios of cool-down used during calculations; - Results – maximum temperature rise as a function of time; • Direct method from 20 K to 4.2 K – direct filling with helium; - Scenario of cool-down used during calculations; - Results - maximum temperature rise as a function of time; • Estimation of maximum temperature rise of cooling helium. • Summary

  10. Modeling of cool-down process – 2 D transient model – indirect cooling • Assumptions: • 8cooling elements (tubes) for magnet are proposed (2 per quarter) on external shell; • Cpand kare function of temperature, Cp(T), k(T); • Helium is treated as solid domain (it could be changed infuture and buoyancy flow can be modeled); • 4scenarios (1.5, 2, 3 and 4 days) of cool-down from 300 K to 20 K are considered; • The cooling tubes are replaced by temperature evolution in time according to thefollowing graph; • The details of cooling scenarios • I II III IV • Cooling step 300 K to 80 K 3 days 2 days 1days 0,5 day • Electrical integrity test at 80 K 6 hour 6 hour 6 hour 6 hour • Cooling step 80 K to 20 K 12 hour 12 hour 12 hour 12 hour • Electrical integrity test at 20 K 6 hour 6 hour 6 hour 6 hour • Total 4 days 3 days 2 days 1,5 day Evolution of temperature on the cooling elements

  11. Modeling of cool-down process – 2 D transient model -indirect cooling Source: Cryocomp Software v 3.06 Metalpak Software v 1.00 11

  12. Cycleof cool-down (every 8 hours for 4 days) Modeling of cool-down process – 2 D transient model - indirect cooling

  13. Modeling of cool-down process – 2 D transient model - indirect cooling Evolution of maximum DT within the magnet structure

  14. Modeling of cool-down process – 2 D transient model - direct cooling After indirect cool-down to 20 K via external tubes, direct cooling method from 20 K to 4.2 K is applied e.g. helium is flowing directly to the structure from the bottom of magnet (vertical configuration). The first type of boundary conditions is used e.g. the temperature on the walls (read lines). The temperature changes in time according to graph. Geometry and boundary conditions applied during simulations

  15. Modeling of cool-down process – 2 D transient model - direct cooling Evolution of maximum DT in the magnet structure during direct cool-down

  16. Modeling of cool-down process – 2 D transient model – mass flow rate of cooling helium The total heat which has to be removed from whole magnet during cool-down via cooling tubes. The data obtained from numerical simulations. Available compressor with maximum capacity 100 g/s of cooling helium at 16 bars and 80 K (SM18 at CERN) and DTmaxcompr=THe Outlet -THe Inlet =50 K. The mass flow rate of cooling helium can be calculated from the equation: m is limited by capacity of compressor (100 g/s) outlet enthalpy of cooling helium for Tout = 80 K + DT, p = 16 bars inlet enthalpy of cooling helium for Tin = 80 K, p = 16 bars

  17. Modeling of cool-down process – 2 D transient model - mass flow rate of cooling helium The changes of maximum temperature rise of cooling helium for different scenarios The changes of maximum temperature rise of cooling helium for different scenarios

  18. Modeling of thermal process in the magnet during ramp (heat dissipation) rate– 2 D steady state model • Geometry and applied mesh; • Properties of the materials; • Results - maximum temperature rise as a function of heat load. • Modeling of cool-down process – 2 D transient model • Indirect method from 300 k to 20 K – cool-down through cooling tubes - Assumptions and scenarios of cool-down used during calculations; - Results – maximum temperature rise as a function of time; • Direct method from 20 K to 4.2 K – direct filling with helium; - Scenario of cool-down used during calculations; - Results - maximum temperature rise as a function of time; • Estimation of maximum temperature rise of cooling helium. • Summary

  19. Summary • 2D numerical model based on FVM (Finite Volume Method) has been developed in ANSYS CFX Software. The steady and unsteady simulations have been performed. • For steady simulations: the maximum temperature rises are smaller than critical temperature. • For transient simulations: • The simulations show that maximum temperature differences in magnet structure are varying from 10 K to 60 K. • The most critical time during cool-down is first 14 hours (by the reason of mechanical constraints). • The maximum temperature rise during direct cool-down is relatively small 0,45 K in comparison with indirect cool-down method. • One compressor is sufficient for indirect cool-down with helium mass flow rate of 100 g/s at 16 bars, 80 K for all scenarios.

  20. Summary Future plans • Develop the numerical model to 3 D. • Simulate the quench evolution in magnet with different localization of quench heaters. • Extend the calculations to superfluid and boiling helium.

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