Status of MHD/Heat Transfer Analysis for DCLL

US-ITER TBM MeetingUS-ITER TBM Meeting

February 14-15, 2007

Rice Room, Boelter Hall 6764, UCLA

Thermofluid / MHD group

Presented by Sergey Smolentsev

Layout

• Conclusions from the previous MHD/Heat Transfer analysis for DCLL

• MHD phenomena and scaling analysis for poloidal ducts

• New analysis for the DCLL DEMO blanket

• Status of DCLL-related R&D

Conclusions from the previous analysis, 1

• Many results for DCLL had been obtained prior to the External Review Meeting at ORNL (Aug. 15-16, 2006)

• The analysis covered MHD/Heat Transfer issues for DCLL DEMO and ITER TBM

• 20-page TBM Tech. Note SS2, Rev. 1, S. Smolentsev, “Heat Transfer Analysis for DEMO, ITER H-H and D-T”

Conclusions from the previous analysis, 2

• High exit temperature (700C) is achievable • FCI provides reasonable MHD pressure drop reduction.• The design window appears to be very narrow.

Reference parameters: SiC=100 S/m and kSiC=2 W/m-K• Serious concerns still remain on the PbLi-Fe interface

temperature and FCI ΔT• Heat transfer is very sensitive to changes in the PbLi

flows. Complex MHD phenomena, including 2-D MHD turbulence, buoyancy-driven flows etc., should be taken into account

DEMO

Conclusions from the previous analysis, 3

• Both ITER scenarios in normal (and even abnormal) conditions look to be acceptable, i.e. all restrictions on the FCI ΔT and the PbLi-Fe interface T can be easily met

• Flow/heat transfer phenomena in DEMO and ITER are expected to differ significantly, both qualitatively and quantitatively

ITER H-H and D-T

Summary of MHD/Heat Transfer phenomena in DCLL

A. 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. Buyoncy driven flows

E. Strong effects of MHD flows and FCI properties on heat transfer

-0.15 -0.1 -0.05 0 0.05 0.1 0.15R adia l d istance, m

400

800

1200

1600

Tem

pera

ture

, C

lam inar flow m odelturbulent flow m odel

DEMO

E

g

DB

=500

=100

=5

A C

Scaling analysis for poloidal ducts for ITER and DEMO

ITER D-T DEMO

Re=30,500 61,000

Ha=6350 Ha=11,640

Ha/Re=0.208 Ha/Re=0.190

N=1320 N=2217

Gr=7.22x109 Gr=3.52x1012

r=11.1 r=70.3

Gr/Re=2.36x105 Gr/Re=5.76x107

Ha/Gr=8.80x10-7 Ha/Gr=3.31x10-9

a/b=0.55 a/b=1.0

L/a=50 L/a=18

•The lack of neutrons and reduced PbLi exit temperature in ITER (470C) are the main reasons why ITER flow physics differs from that in DEMO

•The most pronounced differences are expected in regard to buoyancy-driven flows, which are significantly more intensive under DEMO conditions

•Smartly designed sub-module experiment in ITER may result in data, which can be extrapolated to DEMO conditions (see N. Morley)

ITER versus DEMO

New analysis for DEMO, 1

• New dimensions• New SHF and NWL• New PbLi and He

inlet/outlet T• More detailed

distributions for He flows• 5, 2.5, 10 and 15 mm FCI• Front, 1st and 2d return

ducts

225

210

210

Cross-sectional area of theDCLL blanket with dimensions

SHF = 0.58 MW/m2

NWL = 3.08 MW/m2

PbLi T in/out = 500/700CHe T in/out = 350/450C

What is new ?

New analysis for DEMO, 2

A. Effect of the FCI thickness on the MHD pressure drop: tFCI=2.5, 5, 10 and 15 mm; SiC=100 S/m

B. Effect of SiC on the MHD pressure drop: SiC=5-500 S/m; tSiC=5 mm

C. Heat transfer for the “reference ” case (tsic=5 mm, SiC=100 S/m, kSiC=2W/m-K, Ufront=5.8 cm/s, Urtrn=3.1 cm/s) for the front and two return ducts

D. Heat transfer for the “reduced SiC” case (tsic=5 mm, SiC=20 S/m, kSiC=2W/m-K) for the front duct

E. Heat transfer for the “turbulent” case (reference case parameters but the flow is turbulent) for the front duct

S.Smolentsev, “Upgrades of MHD/Heat Transfer Analysis for DCLL DEMO, TBM Tech. Note TBM-SS3, 21 p., Feb.05, 2007

What has been done?

New analysis for DEMO, 3

FCI: 2.5 mm FCI: 5.0 mm FCI: 10.0 mm FCI: 15.0 mm

Front duct. SiC=100 S/m.

Effect of the FCI thickness on the velocity profile

New analysis for DEMO, 4

SiC=500 S/m SiC=200 S/m SiC=50 S/m SiC=5 S/m

Front duct. tFCI=5 mm.

Effect of SiC on the velocity profile

New analysis for DEMO, 5

FCIthickness

mm

Maximum velocity in the

parallel gap

Maximum velocity in the Hartmann gap

Maximum jet velocity

Velocity at the duct center

2.5 4.2 0.07 6.7 0.07

5 3.0 0.04 5.0 0.08

10 2.1 0.03 3.5 0.21

15 1.7 0.01 2.8 0.35

Effect of the FCI thickness on the jet velocity, velocity at the duct center and in the gap. Front duct. SiC=100 S/m.

SiC

S/m

Maximumvelocity in the

parallel gap

Maximum velocity in the Hartmann gap

Maximum jet velocity

Velocity at the duct center

500 8.0 0.15 8.7 0.15

200 4.4 0.08 6.4 0.08

100 3.0 0.04 5.0 0.08

50 1.8 0.03 3.5 0.20

20 1.0 0.01 2.3 0.45

5 0.5 0.01 1.4 0.8

Effect of the FCI electrical conductivity on the jet velocity, velocity at the duct center and in the gap. Front duct. 5 mm FCI.

*All velocities in the tables are scaled by the mean velocity, i.e. 5.8 cm/s

Effect of SiC and tSiC on the velocity profile

New analysis for DEMO, 6

Rwall

Rgap

RFCIRFCI

~

“True” parameter, which describes the FCI effectiveness as electric insulator, is its “electrical resistance,” i.e. tFCI/SiC

R is the MHD pressure drop reduction factor Circuit analogy

Electric current path

Effect of SiC and tSiC on the MHD pressure drop

New analysis for DEMO, 7

0 1 2 3 4Polo ida l d istance , m

500

550

600

650

700

750

Pb

Li b

ulk

tem

pe

ratu

re, C

Reference caseFront duct1st re turn duct2d return duct

2-D MHD and 3-D Heat Transfer computations for the DEMO blanket,including PbLi front and two return ducts. Reference case. Laminar flow.

Computedvelocity profile

Cross-sectional temperaturedistribution at 1 m from the bottom

Bulk temperature alongthe flow path

Reference case. MHD & Heat Transfer

New analysis for DEMO, 8Reference case. Temperature distribution in the poloidal ducts

X=0.2 m X=0.8 m X=1.4 m X=1.8 m

Fro

nt

1st r

etu

rn2d

ret

urn

-0.15 -0.1 -0.05 0 0.05 0.1 0.15R adia l d istance, m

400

800

1200

1600

Te

mp

era

ture

, C

Tem perature dropacross the FC I

-0.15 -0.1 -0.05 0 0.05 0.1 0.15R adia l d istance, m

400

500

600

700

800

900

Te

mp

era

ture

, C

Tem perature dropacross the FC I

-0.15 -0.1 -0.05 0 0.05 0.1 0.15R adia l d istance, m

400

500

600

700

800

Te

mp

era

ture

, C

Tem perature dropacross the FC I

New analysis for DEMO, 9

Reference case. Summary of Heat Transfer data

Duct Max FCI

ΔT, front

Max FCI

ΔT, side

Max PbLi-Fe T, front

Max PbLi-Fe T, side

front 140 K 500 K 480C 600C

1st R 200 K 200 K 490C 520C

2d R 200 K 200 K 490C 520C

New analysis for DEMO, 10

Reduced SiC (20 S/m) case. Front duct. FCI ΔT. Interface T. FCI 3 FCI 1, 2 Interface 3 Interface 1, 2

200 K 220 K 495C 560 C

New analysis for DEMO, 11

Turbulent case. Front duct. FCI ΔT. Interface T.

FCI 3 FCI 1, 2 Interface 3 Interface 1, 2

240 K 220 K 495C 560 C

New analysis for DEMO, 12

Case Max FCI

ΔT, front

Max FCI

ΔT, side

Max PbLi-Fe T, front

Max PbLi-Fe T, side

Ref. 140 K 500 K 480C 600C

Red.

200 K 220 K 495C 560C

Turb. 240 K 220 K 495C 560C

Comparison for the three cases. Front duct

New analysis for DEMO, 13

• Temperature drop across the FCI and the maximum PbLi-Fe interface temperature is a concern

• Thermal stress analysis should be performed for different flow conditions and FCI thicknesses

• If the stress is too high, changes in the FCI design will be needed

• Realistic maximum allowable interface temperature should be determined based on the corrosion/deposition considerations

CONCLUSIONS

New analysis for DEMO, 14

Suggested modifications in the FCI design (S. Malang)

FCI 1FCI 2

PbLi

A. Double layer FCI B. Goffered FCI

Reduces ΔT in the FCI

More stress tolerance

Status of DCLL-related R&D, 1

• Two turbulence models for LM flows in a blanket have recently been developed.

S. Smolentsev & R. Moreau, Modeling quasi-two-dimensional turbulence in MHD ducts flows, Proc. 2006 Summer Program, CTR, Stanford University, 419-430 (2006)

• Scaling analysis for the PbLi flows in poloidal ducts (ITER and DEMO) has been performed (presented by N. Morley)

Status of DCLL-related R&D, 2

• Differential reduced-scale MHD sub-module has been proposed for testing in ITER (presented by N. Morley and C. Wong)

• Manifold experiment and complimentary modeling are in progress (presented by K. Messadek and M. Ni)

Status of DCLL-related R&D, 3

• A problem for testing the pressure equalization effect has been formulated, and first 3-D runs started with HIMAG

• Discussions on the initialization of the FCI/Heat Transfer experiment are in progress (K. Messadek & S. Smolentsev)

• New round of studies for buoyancy driven flows in DCLL (2-D and 3-D) has been started