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CHATS on Applied Superconductivity , 9-12 th July 2019

Parametric study and optimization of the cooling capacity of the cryomagnetic system for EU DEMO at the pre-conceptual design phase. Christine Hoa a , Thomas Latella a , François Bonne a , Louis Zani b , Benoît Lacroix b , Jean-Marc Poncet a , Monika Lewandowska c ,

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CHATS on Applied Superconductivity , 9-12 th July 2019

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  1. Parametric study and optimization of the cooling capacity of the cryomagnetic system for EU DEMO at the pre-conceptual design phase Christine Hoaa, Thomas Latellaa, François Bonnea, Louis Zanib, Benoît Lacroixb, Jean-Marc Ponceta, Monika Lewandowskac, Kamil Sedlakd, Valentina Coratoe aUniv. Grenoble Alpes, CEA IRIG-DSBT, Grenoble 38000 France bCEA IRFM, Saint Paul lez Durance 13018 France cFaculty of Mechanical Engineering and Mechatronics, West Pomeranian University of Technology, Szczecin, Poland dÉcolePolytechniqueFédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), Forschungsstrasse 111, 5232 Villigen PSI, Switzerland eENEA, ENEA C.R. Frascati, 00044 Frascati (Rome), Italy CHATS on AppliedSuperconductivity, 9-12th July 2019 Faculty of Mechanical Engineering and Mechatronics of the West Pomeranian University of Technology, Szczecin

  2. Summary • Context of the study • Optimizations on the pancake design • Preliminary results on the double layer design • Conclusions & perspectives

  3. Context of the study 28 sept. 2016

  4. Context of the study • Pre-conceptual design of EU DEMO magnets including cryogenic studies • Toroïdal Field superconducting magnet design • 3 cable-in-conduct designs (2015) • ITER-like: double pancake design • Graded conductors: layer-design • Mechanical analysis • Thermal-hydraulic analysis • Cryogenic studies • Objective: to find cost effective solutions for the superconducting magnets and their cooling systems

  5. Context of the study

  6. Context of the study Interface with the cryogenic distribution: Supercritical helium at Tin= 4.5 K, Pin=6 bar, = 1 bar (reference case) Thermal hydraulic analysis: (Tcs (x)- Tcicc (x) ) > 1,5 K Plasma Nuclear heating, AC losses, radiation, conduction, joints…. What is the optimized (magnet+ cryogenic distribution)? Parametric studies Tin et

  7. Context of the study Nb3Sn TF conductor options 05/10/2018 single layer Double layers Double pancake

  8. Modelling tools Optimization model 1D CICC model

  9. Modelling METHODOLOGY • Variable Parameters • Tin = [4.05; 4.2; 4.35, 4.5] K • ΔP= [0.25, 0.5; 0.75; 1] bar TF coil with a CICC design Cross-checks SIMCRYOGENICS 1D CICC model Inter-turn /Inter layer coupling Parametric studies • TACTICS: THEA/CAST3M model • Inter-turn coupling • Analytical model • 1D CICC model • no inter-turn coupling • Parametric studies Nuclearheating SIMCRYOGENICS Optimization algorithm (CryodistributionSHe loop+ CICC model

  10. OptimizationSon the Pancake design WP3 28 sept. 2016

  11. Simcryogenics model cryodistribution +Cable-in- conductor WP3 Double Pancake design (CEA) Central double pancake

  12. ASSUMPTIONS of the model • 1D CICC model with Inter-turn thermal coupling

  13. ASSUMPTIONS of the model • Impact of the inter-turn model on the heat load repartition With inter-turn Without inter turn WP3 v2 reference case Tin=4.5 K, ΔP=1 bar Total load 11.7 W

  14. Parametric studies • Good agreement between Simcryogenicsand the analytical model with no inter-turn coupling

  15. Parametric studies • Simcryogenics model with/without inter-turn coupling • Impact of the inter-turn coupling on the minimum DT margin (up to 0,2 K) • The inter-turn coupling gives lower values of DT margin

  16. OPtimization model cryodistribution +CICC • 1 optimization calculation for the central pancake WP3 2b • Optimized parameters • Tin = Tbath +0.05 K • ΔP • Constraint - • Minimization of the refrigeration power • CICC loads • Cold circulatorpumping power • Cold compressor 4.5 K, 10 bar Tbathor Pbath Tin= Tbath+0.05 K

  17. Optimization results • Temperature margin criteria fixed at 1.5 K with respect to Tcs(x) • Minimum temperature margin is located in the first 40 meters of the conductor length

  18. Optimization results Total refrigeration power 15.8 W Total refrigeration power 25.6 W • Refrigeration power saving is about 33% on WP3 2b design • Large reduction of the pumping powers of the cold circulator • Small increase of the cold compressor power to reduce the inlet temperature to 4.24 K 11.7 W (50%) 11.4 W (48%) 12.6 W (53 %) 1.25 W (5%) 1.8 W (8%) 0.5 W (2%) Optimized case Tin=4.24 K, ΔP=0.25 bar, Reference case Tin=4.5 K, ΔP=1 bar,

  19. Preliminary results on double layer design (WP2) 28 sept. 2016

  20. Parametric studies WP2 WP2 (ENEA Design) 6 Double Layers • 6 double layers • DL1 to DL5 Nb3Sn (high field region) • DL5 Nb-Ti • Rectangular CICC • Bundle region • 2 cooling channels with steel spirals

  21. Inputs of the model Nuclearheatingheat load Tcs(x) Current Sharing Temperature with 1.5 K margin • The heat load is uniformly distributed on each layer • Large non uniformity of the heat load among the 6 DL  graded conductors • Tcs(x) on odd layers • 18 inter-turns on each layer • DL1, DL2, DL5 have the lowest values of Tcs (x)  critical DLs

  22. Layer 1 and Layer 3 • Simcryogenics simulates lower or higher minimum DT margins with respect to analytical model FME • Higher heat input : Layer 1: 39.6 W/ Layer 3: 23.6 W • The reference case (Tin=4.5K, ΔP=1 bar)is not compliant with DT margin=1.5 K for bothlayers.

  23. Layer 5 and layer 7 • Good agreement between the 2 models • Small impact of the inter-turn coupling with lower loads (15.1 W and 8.7 W)

  24. Layer 9 and layer 11 • Good agreement between the 2 models • Small impact of the inter-turn coupling with lower loads (5.1 W and 3 W)

  25. OPtimization model cryodistribution +CICC • Optimization • 1 optimization calculation for each double layers of the WP2 design • One global optimization on the 6 DLs • Optimized parameters • Tin = [4.0, 4.5] K • ΔP= [0.25, 1.2] bar • Temperatureconstraint - • Minimization of the refrigeration power • Heat input on the CICC • Cold circulatorpumping power • Cold compressor Tbathor Pbath Tin= Tbath+0.05 K

  26. Results on temperature constraint • Minimum temperature margins are located in the 250 last meters of conductor length Minimum DT margin for DL1 Minimum DT margin for the 5 other DLs

  27. DOUBLE Layer optimization • 6 optimization calculations • Comparison with the reference case Tin=4.5 K and ΔP=1 bar • Large distribution of the optimized parameters (Tin, ΔP) on the 6 DLs: • Tin [4.16, 4.5] K • ΔP: [0.25, 1.2] bar • Global optimization for the 6 DLs to becompleted (longer computation time)

  28. Optimization: TOTAL refrigeration Power • Minimization of the pumping powers of the cold circulator and cold compressor • Cold compressor (impact on Tin): 6% to 19% of the total refrigeration power • Cold circulator (impact on ΔP): 2% to 17% of the total refrigeration power DL1 4,33 K, 1.2 bar DL2 4,44 K, 1.2 bar DL3 4,50 K, 0.53 bar DL4 4,50 K, 0.32 bar DL5 4,16 K, 0.36 bar DL6 4,45 K, 0.25 bar

  29. Conclusions & persepctives 28 sept. 2016

  30. conclusion • Investigations on the cooling parameters beyond the reference values (Tin=4.5 K, ΔP=1 bar) on 2 CICC designs • Parametric studies on temperature margin on WP3 and WP2 • Cross checks have been performed with an analytical model • Inter-turn coupling can have impact on the temperature margin calculation depending on the heat input value and distribution. • Model-based optimization tool with Simcryogenics is well adapted to compare different CICC designs and estimate the total refrigeration power taking into account the pumping powers of the cold circulator and cold compressor • Optimization on the Pancake wound design (WP3 v2b) • WP3 88 kA (2b design) : 4.16 K, ΔP=0.25 bar • Potential saving of 33% on the total refrigeration power with respect to the reference case

  31. Perspectives • Preliminary optimization results on the Double Layer CICC (WP2 design) • First results to be consolidation/cross checked • Optimization per layer design: large distribution of the optimized parameters (Tin, ΔP) • Possible impacts on the cooling system architecture • 1 or several temperatures supply • Parallel or in series distributions of the hydraulic circuits • Global optimization of the 6 DLs to be performed: one optimal (Tin, ΔP) • Contribution to the magnet design activities • Iteration loop with the magnet designer with WP3 • refrigeration power vs. conductor mass • Comparisons of the 3 designs for EU DEMO • Complete the comparisons between the 3 designs (2015): pancake and double layer • Analyze new 2019 designs

  32. Thankyou for your attention Commissariat à l’énergie atomique et aux énergies alternatives Centre de Grenoble| 38054 Grenoble Cedex 09 T. +33 (0)4 38 78 48 85 | M. +33 (0)1 06 38 65 71 06 Etablissement public à caractère industriel et commercial | RCS Paris B 775 685 019 Direction de la Recherche FondamentaleInstitut Nanosciences et CryogénieService des Basses TempératuresLaboratoire d’Électronique et d’Automatismes 28 sept. 2016

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