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FNST/MASCO/PFC Meeting. Boiling Heat Transfer in ITER First Wall Hypervapotrons. Dennis Youchison, Mike Ulrickson and Jim Bullock Sandia National Laboratories Albuquerque, NM August 6, 2010.

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Boiling Heat Transfer in ITER First Wall Hypervapotrons


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boiling heat transfer in iter first wall hypervapotrons

FNST/MASCO/PFC Meeting

Boiling Heat Transfer in ITER First Wall Hypervapotrons

Dennis Youchison, Mike Ulrickson and Jim Bullock

Sandia National Laboratories

Albuquerque, NM

August 6, 2010

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company,for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

1

outline
Outline
  • What are hypervapotrons?
  • Why hypervapotrons?
  • Geometry optimization
  • Boiling heat transfer in hypervapotrons
    • Why CFD?
  • Benchmarking with HHF test data
  • CHF prediction

2

slide3

Background

  • Star-CCM+ Version 5.04.006, User Guide, CD-adapco, Inc., New York, NY USA (2010).
  • S. Lo and A. Splawski, “Star-CD Boiling Model Development”, CD-adapco, (2008).
  • D.L. Youchison, M.A. Ulrickson, J.H. Bullock, “A Comparison of Two-Phase Computational Fluid Dynamics Codes Applied to the ITER First Wall Hypervapotron,” IEEE Trans. On Plasma. Science, 38 7, 1704-1708 (2010).
  • Upcoming paper in the 2010 TOFE .

3

why hypervapotrons
Why hypervapotrons?
  • Advantages:
  • High CHF with relatively lower pressure drop
  • Reduction in E&M loads due to thin copper faceplate
  • Lower Cu/Be interface temperature (no ss liners)
  • Less bowing of fingers due to thermal loads
  • Disadvantages:
  • CuCrZr/SS316LN UHV joint exposed to water

5

slide6

What are hypervapotrons?

Hypervapotron FW “finger”

6

two phase cfd in water cooled pfcs
Two-phase CFD in water-cooled PFCs
  • Problem: conjugate heat transfer with boiling
  • • Focus on nucleate boiling regime below critical
  • heat flux
  • • Use Eulerian multiphase model in FLUENT & Star-CCM+
  • • RPI model (Bergles&Rohsenow)
  • • Features heat and mass transfer between liquid
  • and vapor, custom drag law, lift or buoyancy and influence of bubbles on turbulence
  • CCM+ transitions to a VOF model for the film when vapor fraction is high enough – need to know when to initiate VOF

7

slide8

5 MW/m2

400 g/s

t=2.05s

Velocity distributions

Drag on bubbles, lift or buoyancy, changes in viscosity and geometry, all affect the velocity distribution under the heated zone.

2mm-deep teeth and 3-mm spacing optimized to produce a simple reverse eddy in the groove.

8

slide9

Star-CCM+ 560 k polyhedra mesh

Switches from Eulerian multi-phase mixture to VOF for film boiling.

9

slide10

Star-CCM+ Results

CCM+ boiling models were benchmarked

against US and Russian test data for rectangular

channels and hypervapotrons to within 10oC.

Case analyzed is a hot “stripe” on a section of the ITER first wall.

Surface temperature distribution, t=6.3 s

capability to predict CHF from CFD

10

slide11

With no boiling, heat transfer is highest under the fins

With boiling, the vapor fraction in grooves is 4%-6% on average

Star-CCM+ Results

Case analyzed is a hot “stripe” on a section of the ITER first wall.

The details of the heat transfer change dramatically as boiling ensues.

Iso-surface of 2% vapor volume fraction

t=6.3 s

11

slide12

Star-CCM+ gives same h as Fluentfor nucleate boiling.

Heat transfer coefficients increase in grooves where boiling takes place ranging from 12,000 to 13,000 W/m2K.

12

slide14

Thermocouple response 3.5 MW/m2 through 6 s

Thermocouple response 4.0 MW/m2 through 6 s

Russian data

ICHF

Trip @ 400 C

Temperature (C)

Not ss yet!

Temperature (C)

Rectangular channel

results

14

total of 490k poly cells in mesh
Total of 490k poly cells in mesh

3 prism layers

Heated area is 100 mm x 48 mm

16

thermocouple response through 6 s
Thermocouple response through 6 s

4 s for TCs to ss

Russian data

20

all flow regimes can exist simultaneously
All flow regimes can exist simultaneously.

T:

h:

  • sub-cooled
  • nucleate to transition boiling
  • film boiling
  • sub-cooled

4.0 MW/m2

115 oC, 2 MPa water

1.0 m/s

22

slide23

CHF Testing

Testing of the HV mock-up

T/C (1.5 mm from CuCrZr surface)

Water 2 m/s

Pabs 10 MW/m2

tpuls 300s

Second pulse at 10 MW/m2)

ICHF !

23