Simulations of Free surface liquid metal layers and other topics…

077-05/rs

Neil B. Morley, A. Ying, M. Narula, R. Hunt, M. AbdouUCLA Fusion Science and Technology, UCLA

R. Munipalli, P. Huang – HyPerCompM. Jaworski, D. Ruzic – UIUC

Simulations of Free surface liquid metal layers

and other topics…

077-05/rs

3D MHD simulations of thermocapillary, thermoelectric, and buoyancy effects in liquid metal layers heated from the top

Initial tests of SiC/Ga compatibility at 750C Initial studies of Be/F82H bonding for ITER TBM

armor attachment Separate Presentation - Simulations of active

water cooling of the ITER FW/Shield components 3D Simulations and experiments for fast flowing

liquid metal layers (work completed this year, but not presented here)

Outline

077-05/rs

HyPerComp Incompressible MHD solver for Arbitrary Geometry

3D, MHD, multiple material, coupled transport (heat/mass) code for liquid metal free surface and closed channel (blanket) problems

Main development activities: Acceleration and validation exercises (see Munipalli poster)

077-05/rs

Thermocapillary Force Modeling

Surface heating can cause a temperature gradient at the free surface

Surface tension changes as a function of temperature (lithium factor is about -3.75%/100K)

Liquid moves along the surface from areas of lower surface tension to higher surface tension, thermocapillary (Marangoni) convection Fsurf= n – s where = surface curvature, n = surface unit normal, s surface gradient

Rigid-Lid Boundary -- “Free” surface approximation with traction

n u =sT where = o + T = temp dependent surface tension coefficient,

Deformable free surface with improved surface tension model in HIMAG to include variable surface tension

Fsurf= n – s n – (T – nT)

-4 -2 0 2 40

0.2

0.4

0.6

0.8

1

Free surface contours

Tangential surface tension forces

Liquid metal

Gas/Plasma/Vacuum

077-05/rs

SLIDE and Thick Liquid Layer Simulations with rigid-lid BC

1 x 10 x 10 cm cavity full of Lithium simulated with 3D-MHD HIMAG code

Surface Conditions– 10 mm wide shaped surface heat

flux strip• LHF = 104 W/m2 peak• HHF = 106 W/m2 peak

– Rigid-Lid “Free” surface approximation with traction

n u =sT

Wall conditions– No-slip– Electrically insulated or

perfectly conducting– Thermally insulated, sides– Isothermal, bottom

5

Surface heat flux

Lithium cavity

B

Field |B| Bcopl Bnorm

Case 1 0.500 0 0.500 0.000

Case 2 0.500 15 0.483 0.129

Case 3 0.129 90 0.000 0.129

- dynamic viscosity

- surface tension gradient wrt T

077-05/rs

(2u/y2) - B2u/ - g h/x = 0 1D Model including: – Surface height change – Conservation of flow Gives solution: – dh/dx =

– usurf =

– u(y)/usurf =

xy

1D Analytic Model – (Slightly modified from Jaworski)

6

Constant surface temperature gradient

T/x = b, Defines surface traction

b = (/) u/y

B

077-05/rs

X

-4

-2

0

2

4

Y

-4

-2

0

2

4

Z00.51

X Y

Z

B

T gradient ~ 104 K/m

Surface Temperature Comparison of 3D

HIMAG simulation with rigid-lid BC to 1D analytical model

077-05/rs

B = 0.13 T

B = 0.5 T

Surface temperature profiles not dramatically changed with field direction changes

Heat flux into the bottom wall was measurably changed

Study of impact of field direction on Marangoni recirculation velocity

B = 0.5 T

077-05/rs

New rigidlid results – no symmetry and 3 component field relative to the walls / heat flux

9

B = 0.5 T 15

15

077-05/rs

Looking from the top, the heated spot appears to be pulled slightly off center line by strong lateral velocity

10

077-05/rs

Parameter b/gh (~Bond No.) provides estimate of the change in surface height

b b/gh ~q’’

103 K/m .03 mm/cm 105 W/m2

104 K/m .3 mm/cm 106 W/m2

105 K/m 3 mm/cm 107 W/m2

dh/dx varies from 1.5x to 1x the dimensionless parameter b/gh with increasing field

Surface deformation becomes important for SLIDE (~1 cm) when q’’ approaches 10 MW/m2

Surface deformation becomes important for 1 mm when q’’ approaches 100 kW/m2

Bond No. for 1 cm thick lithium film

b b/gh ~q’’

103 K/m .3 mm/cm 105 W/m2

104 K/m 3 mm/cm 106 W/m2

105 K/m 30 mm/cm 107 W/m2

Bond No. for 1 mm thick lithium film

077-05/rs

12

5 mm thick Li film in a 10 x 10 cm reservoir

Strip heat flux with 1 MW/m2 peak 1 cm width

Fluid ratio 100 Small field (500 g)

Observed height change ~0.6 mm

Peak surface velocity 0.22 m/s in liquid phase

Test case with temperature dependent surface tension and deformable surface model

lithium

~gas

Heat flux

Slices from 3D simulation showing temperature and velocity contours

streamlines

077-05/rs

Conclusions of Thermocapillary simulations

Thermocapillary surface velocity on the order of tens of cm/s possible with 1 MW/m2 heat flux on 1 cm deep lithium, even in 0.5 T magnetic fields

Thin film motion more strongly influenced by small surface normal field than the larger toroidal field– SLIDE with surface normal field only should give similar flow and thermal

response to divertors– 1D model with surface normal field appears to give good estimate of

base flow at the surface Impact of convection flow should provide measurable

variation in heat flux at the bottom surface– Flows for different field alignment cases are very different

Surface deformation should become appreciable at heat fluxes > 1 MW/m2 or for thinner films

Cases with no symmetry assumption/ 3D fields, some asymmetric effects seen – more interpretation necessary

13

077-05/rs

Thermoelectric Currents and Forces

Slices from 3D simulation showing thermoelectric current emerging from steel wall at the hot interface and returning at cooler interface

Surface heating can cause a temperature gradient at the solid/liquid interface

This induces an electric current via the Seebeck effect (lithium/Iron couple is about 20 V/K)

Electric current interacts with the magnetic field via JxB Lorentz force

Include S T into Ohm’s law calculation

j = (– + v x B - ST)

077-05/rs

Li has unusually high Seebeck constant

15

Li is very thermo-electrically active

Li/Iron hasP = SLi – SFe ~ 20

Impact of this effect is suspected in SLIDE results

077-05/rs

Preliminary test of TE current effect on SLIDE

163D simulation showing thermoelectric induced vortical motion

Test problem with electric potential at bottom wall imposed to approximate S.grad(T) effect from SLIDE data

– 1 MW/m2 heat flux stip, 500 g vertical field, 15 K temp difference at bottom wall, rigid-lid “free” surface

Result clearly shows cyclonetype vortical motion ~0.3 m/s on surfaceand strong smearingof the heat flux at the “free” surface

Will be strong difference betweenvertical and horizontal fields

077-05/rs

Next steps

17

Finish coupling / testing of HIMAG changes – Higher resolution tests, higher field tests– simulation of representative SLIDE cases– simulations of effect for thin heated films with coplanar

fields (NSTX, melt layers, DiMES revisted) Combined deformable surface, thermocapillary,

thermo-electric, buoyancy simulations

ISFNT paper

Consideration of future experiments in BOB or QTORmagnets (using Ga alloy, Hg, Pb alloy)

MTOR Thermofluid/MHD facility

077-05/rs

Magnetic Intervention for Inertial Fusion:Cusp magnetic field keeps ions off the wall(in Plasma Physics terms: Conservation of P = rA = 0)

Axis Polar cusp (2)

Equatorial

cusp

Plasma expansion initially spherical

Ion cloud deforms as it encounters cusp

Ions, at reduced power, leak into external dumps

1. Physics demonstrated in 1979 NRL experiment: R. E. Pechacek, et al., Phys. Rev. Lett. 45, 256

(1980).2. NRL experiment modeled by D. Rose at Voss Scientific

(2006)

077-05/rs

Chamber radius: 5 m Point cusps: 16 T Main coils: 0.75 T

Energy absorption in Ga: 85% in first 10 mg/cm2

15% in next 100 mg/cm2

Only first layer evaporates

Gallium inventory enough so mean temp rise < 300C

1 1

2 23

4 5

9

8

7

6

3

45

9

8

7

6

An example of a Magnetic Intervention Chamber

Ions deflected downward by magnetic fieldsIon energy absorbed in Gallium Rain Ion Dissipaters

ionorbits

beam tubes

chamber

coils

GalliumDroplets

NB Vapor P of Ga = 10-6T at 720 C

A.E. Robson, NRL (ret)

077-05/rs

Preliminary Compatibility Tests between CVD SiC and Pure Ga

Quartz crucible containing SiC disk and Ga, in quartz vacuum tube – before test

After test – Bands of white (located inside furnace) and black (located outside furnace) deposits following 25 hours

077-05/rs


SiC Disk after Ga ExposureSiC Disk after Exposure and Cleaning

Ga partially wets the SiC, roughly have the sample surface area

Ga can be removed by scrubbing with a soft cloth and HCL/ethanol mixture – slight surface discoloration remains

10 mm

077-05/rs


Initial Conclusions– White material

deposition has gallium oxide and both C and Si present

– Partial wetting of the SiC disk was observed

– Sample weighing did indicate a mass loss was 6 mg after only 25 hours

077-05/rs

Test Description– CVD SiC disk sample (initially 0.806 g)– SiC cleaned with ethanol and acetone, then blown with dry air– Pure Ga metal (~3 ml) from Atlantic Metals– In quartz (Si02) crucible, with quartz insert to keep SiC submerged– Crucible placed on steel support in quartz tube, pumped on with mechanical and turbo pump (but no vacuum gauge

available)– Aluminum witness plate placed in cold region of the quartz tube– Quartz tube inserted into tube furnace– Temperature brought to 100C for 24 hours to fully pumping/baking on tube and sample before beginning high temperature

exposure– Temperature brought to 400C for 2 hours to continue pumping/baking, some minor deposition of dark material on cold

quartz tube wall immediately above heater (see photos)– Temperature brought to 700C for 24 hours, significant deposition of dark material seen on cold quartz tube wall

immediately above heater (see photos)– Test terminated due to concerns an unexpected reaction was taking place– White material deposition seen on the quartz tube wall, and steel support inside the hot region (see photo)– Partial wetting of the SiC disk was observed– Sample cleaned with HCL solution (good for dissolving Ga oxides), Fantastic (good for dissolving Ga oxides), water, acetone

and blown with dry air. Mass loss was 6 mg.


077-05/rs

Application: ITER requires a 2mm coating/armor of Beryllium on plasma facing surfaces of TBMsBe used as armor layerF82H (or EUROFER97) used as structural material

Task: create a robust diffusion bond between two dissimilar metalsBeryllium & RAFM steel (F82H)

Metallize Be (w/ Ti, Cu) to enhance HIP bonding characteristics.

Status of Experiments

–Phase 1 HIP Cu to RAFM steel •650*, 700, 750, 800, 850* C *completed•Tensile test, shear test, microstructure analysis all underway

–Phase 2 Not yet underway. Proceed with Be bonding studies

Perform direct bonding of Be to Reduced Activation Ferritic/Martensitic Steel (Hunt, Ying (ULCA), Goods (SNLL))

077-05/rs

Cu to RAFS HIP @ 650 & 850 C (Tensile Test)

850 CFailure in Cu bulk material

850 C diffuses enough to create strong bond



650 CFailure at material interface

650 C creates insufficient bond



077-05/rs

Cu to F82H HIP at 650 & 850 C (Shear Test)









077-05/rs

HIP Test Findings/Progress

AES in progress to characterize elemental composition of fracture surfaces and HIP bond interfaces– Initial AES (auger electron spectroscopy) shows

very little Cu across interface in 650 C HIP Insufficient metallurgical bond

850 C (HIP for 2hrs @ 103MPa) high enough temp for sufficient diffusion of Cu/RAFM

Proceed with HIP at 800, 750, 700 C to find lower suitable temp than 850 C

077-05/rs

Metallization

Proceeding with a series of diffusion studies to optimize Ti and Cu film thicknesses via EMP/SEM characterization

– Anneal substrates of Cu with PVD Ti, and electroplated Cu

Microprobe Analysis– 650 C – Significant percent of

the 20 mm Ti metallization film is reacted

– 850C – TBD– Proceed with 700, 750, 800

to match HIP test temperatures

Oxidation levels found higher than expected. PVD chamber potentially problematic.

Figure showing Cu bulk (light color on top, Ti deposition layer (dark in middle),

and Cu electroplate layer (light color on bottom)

Simulations of Free surface liquid metal layers and other topics…

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