Manifolding and MHD issues M. S. Tillack, S. Malang, X. R. Wang ARIES Project Meeting 31 May – 1 June, 2012

Next Steps for MHD and thermal hydraulics (from January Project Meeting) Provide final guidance on MHD Dp. Select the FW channel depth. Choose k for inlet/outlet manifolds. Need full definition of flow paths, flow control Provide temperature boundary conditions for thermal stress analysis. Full heat transfer analysis Start analysis of DCLL (ACT-3) blanket.

Added Topics Definition of ACT1 flow loop pressures and temperatures, power conversion system parameters. Further definition of lower manifold region. Proposed use of “flow balancing”.

Manifolding and distribution Field entrance and exit We have minimized 3D MHD effects throughout the SCLL blanket, except inlet FW manifolds Radial paths Radial variation in field and velocity 90˚ bend 180˚ bends No problem Minor problem Curved flow Radial variation in field and velocity Radial contraction Central duct OK. Annular channels require control. Manifolding and distribution No problem Field entrance and exit TF unavoidable, PF can be reduced

New access pipe routing reduces PF fields experienced by the fluid

(IB now has 8 parallel ducts) Central manifolds use successive splits plus toroidal movements with poloidal component Good (IB now has 8 parallel ducts) Coaxial pipes everywhere Gradual toroidal motions Symmetric splts (some extra Dp, but flow balanced) FW manifolds are a problem. Electrodes are recommended.

“Flow balancing” technique forces equal potential between parallel channels Higher velocity channels generate excess current that pumps the lower-velocity channels. Effectiveness is related to the additional 3d pressure drop. Compatibility of PbLi with W has been studied (Feuerstein, J. Nuc Mater 1996) up to 600 C. M. S. Tillack and N. B. Morley, “Flow Balancing in Liquid Metal Blankets,” Fusion Eng. Design 27 (1995) 735-741.

Pressures and pressure drops for the ARIES SCLL IB blanket Heat exchanger Pressures and pressure drops for the ARIES SCLL IB blanket Dp = 0.25 MPa 0.25 (outboard Dpmhd will be lower) p > 0 4 m (0.4 MPa) Dptop = 0.1 MPa 0.85 0.95 8 m (0.8 MPa) Dpbulk = 0 DpFW = 0.2 MPa 1.65 1.95 Dpout = 0.2 MPa Dpin = 0.45 MPa 2.4 4 m (0.4 MPa) 1.45 1.2 MPa pump 2.8 1.6 1.85 1.85

Semi-empirical formulation of 3D MHD effects Dp3d = k N (rv2/2) where N = Ha2/Re, and k is a semi-empirical constant (z=kN)` For flows with geometrical changes in a uniform magnetic field 0.25 < k < 2. For a change in transverse field strength k~0.1–0.2 (depending on the abruptness of the change in B). For an inlet or outlet manifold, Smolentsev et al used k=1.5. Depends on wall conductance, pipe shape (e.g. circular or rectangular) and other details. I.R. Kirillov, C.B. Reed, L.Barleon, K. Miyazaki, “Present understanding of MHD and heat transfer phenomena for liquid metal blankets, “Fusion Eng and Design 27 (1995) 553-569. S. Smolentsev, C. Wong, S. Malang, M. Dagher, M. Abdou, “MHD considerations for the DCLL inboard blanket and access ducts,” Fusion Eng and Design 85 (2010) 1007–1011.

Final design of blanket based on 2 MPa internal pressure (1 cm annular cooling channel depth for all) 45 cm 30 cm 35 cm Inboard (8 per sector) Outboard I (12 per sector) Outboard II (12 per sector)

Convective heat transfer with laminar slug flow Energy balance equation (internal energy e=rCpT): Exact solution for constant velocity on a semi-infinite plane is equivalent to transient 1D conduction: slug Example slug result: T vs. z/v for several x, q”=0.2 MW/m2, v=4.2 m/s, L=8.3 m

Computational approach for variable flow FW and SW flows are mixed to create uniform central duct inlet temperature

1-dimensionalized FW velocity profile <v> = 2.66 m/s in FW channel Worst case profile that conserves <v> All other channels have constant velocity (0.094 m/s center, 0.266 m/s SW)

Results (radial profiles)

Results (axial profiles)

Heat exchanger temperatures on the primary and secondary sides Temperature restrictions on components reduces the power cycle performance Heat exchanger temperatures on the primary and secondary sides

Power flows and bulk coolant temperatures in ARIES ACT SCLL hot (ACT-1b strawman) 1000 C 1565 MW 6 MW 740 C PbLi HX FW blanket h=58% pump heat cold 325 MW 710 C divertors 800 C hot 700 C pump heat He HX 17 MW 680 C 228 MW hot shields 600 C 650 C cold compressors recuperator to He HX 600 C from PbLi HX Heat sink 1000 C turbine

Brayton cycle efficiency and power core inlet temperature 1000 C turbine inlet temperature 1050 C turbine inlet temperature ARIES-AT operating point

Next step activities Update ACT1 MHD, thermal-hydraulic and geometric parameters (after final strawman is available). Recalculate MHD, thermal-hydraulic and geometric parameters for ACT2 (after strawman is available). Start analysis of DCLL (ACT-3) blanket. Overall configuration will be very similar to ACT1 Manifolding will be simpler

Extras

3D MHD is the dominant force acting upon the coolant in insulated channel blankets FW blanket L g u A inertia gravity wall shear 3D MHD ru2 rgL suB2L/Ha kN (ru2)/2 160,000 8x105 190,000 3x106 100 8x105 475 7x105 conservative dissipative FW core r 10250 kg/m3 s 7.6e5 W-m m 6.5e-4 kg/(m s) L 8 B T u 4 0.1 m/s a 0.03 0.3 Ha 8200 82,000 aB(s/m)1/2 Re|| 2e6 5e5 rua/m N 35 14,000 saB2/ru k 1