Review of Thermofluid / MHD activities for DCLL

Review of Thermofluid / MHD activities for DCLL Sergey Smolentsev & US TBM Thermofluid/MHD Group 2006 US-Japan Workshop on FUSION HIGH POWER DENSITY COMPONENTS and SYSTEMS Santa Fe, New Mexico, USA Nov. 15-17, 2006

Outline • Introduction. MHD phenomena in DCLL blankets • Scaling analysis for DCLL DEMO and ITER TBM • Particular MHD phenomena • MHD software development: HIMAG • Experiment

B-field He FCI PbLi DCLL is current US blanket choice for DEMO and testing in ITER DCLL DEMO ITER TBM SiC/SiC FCI is the key element of DCLL • Blanket performance is strongly affected by MHD phenomena • Studying MHD in DCLL conditions is one of the most important goals

physical/mathematical model development • code development • numerical simulations • experiments Thermofluid / MHD activities cover two major areas: (I) Design, (II) R&D • Thermofluid / MHD issues of the DCLL blanket: • Effectiveness of FCI as electric/thermal insulator • MHD pressure drop • Flow distribution and balancing • Heat transfer These issues are being addressed via:

E D B A C g DEMO Heat Transfer in DCLL blankets is strongly affected by fluid flow phenomena, where MHD plays a major role • Formation of high-velocity near-wall jets B.2-D MHD turbulence in flows with M-type velocity profile C. Reduction of turbulence via Joule dissipation D. Natural/mixed convection E. Strong effects of MHD flows and FCI properties on heat transfer =5 =100 =500

Key DCLL parameters (outboard) MHD / Heat Transfer phenomena in ITER can be quantitatively/qualitatively different from those in DEMO

Engineering scaling (poloidal flow) Major differences between ITER and DEMO are expected for buoyancy- driven flows, which are much more intensive in DEMO conditions

a b a b Formation of near-wall jets and MHD pressure drop reduction by FCI No pressure equalization openings DCLL unit-cell with FCI With a pressure equalization slot MHD pressure drop reduction by FCI DEMO (old) B=4 T Ha=16,000

(b) Poloidal distance (a) B Study of MHD buoyancy-driven flows A. Numerical simulation of unsteady buoyancy-driven flows Present computations are limited to Gr~107. The near goal is to achieve Gr~109-1012. B. Analytical solution for steady mixed convection

Modeling of 2-D MHD turbulence • Two eddy-viscosity models (zero- and one-equation) have been • developed and tested against experimental data (MATUR) • 2-D DNS was performed for flows with internal shear layers to • address the effect of bulk eddies on the boundary layer • One-equation model was used in heat transfer calculations for DCLL 2-D DNS

y U(y) (y) 0 x x 0 l Transitions in MHD flows in a gradient magnetic field A. Linear stability analysis B. Nonlinear analysis BC: Flow will be unstable if the Hartmann number built through the magnetic field gradient > ~ 5 Sketch of the problem. Formation of the double row of staggered vortices from the internal shear layers.

Temperature Profile for Model DEMO Case kFCI = 2 W/m-K FCI Pb-Li FS GAP sFCI = 5 S/m 20 S/m 100 S/m Heat transfer for 3 DCLL scenarios:DEMO, ITER H-H, ITER D-T Parametric analysis at: 0.01<<500, 2<k<20 • Preliminary identification of required SiC FCI properties: ~100 S/m, k~2 W/m-K • The most critical requirement is that on T across the FCI. Near-wall jet allows for lower T • Reduction of the jet effect via instabilities, turbulence, buoyancy-driven flows ? • Narrow design window • Further MHD analysis is necessary

U / U0 y / a MHD software development: HIMAG Rectangular duct, Ha=10,000 • The HyPerComp Incompressible MHD Solver for Arbitrary Geometry (HIMAG) has been developed over the past several years by a US software company HyPerComp with some support from UCLA. • At the beginning of the code design, the emphasis was on the accurate capture of a free surface in low to moderate Hartmann number flows. • At present, efforts are directed to the code modification and benchmarking for higher Hartmann number flows in typical closed channel configurations relevant to the DCLL blanket. Circular pipe, Ha=1000

QTOR magnet and LM flow loop BOB magnet JUPITER 2 MHD Heat Transfer Exp. in UCLA FLIHY Electrolyte Loop MTOR Laboratory at UCLA

The manifold experiment • (Exp. A) Non-conducting test-article • (Exp. B) Conducting test-article • (Exp. C) Manifold optimization • Parameters: L=1 m, B~2 T • Measurements: Pressure, electric potential, flow rate, velocity • Status: Vacuum testing Goal:Manifold design that provides uniform flow distribution and minimizes the MHD pressure drop

Modeling the manifold experiment (Exp. A): Ha = 1000; Re = 1000; N = 1000

Modeling the manifold experiment Flow imbalance: center channel = +11.8% side channels = -5.9% Dependence on Ha, Reand geometry must be studied – Likely to be more imbalanced at higher Ha

CONCLUSIONS • Basic MHD phenomena that affect blanket performance have been identified • Preliminary MHD/Heat Transfer analysis have been performed for 3 blanket scenarios using reduced 2-D/3-D models • More analysis is required to address 3-D issues based on full models and via experiments • HIMAG is potentially a very effective numerical tool for LM blanket applications

Review of Thermofluid / MHD activities for DCLL