Upload
alicia-robinson
View
219
Download
0
Tags:
Embed Size (px)
Citation preview
DL Youchison 5931/31.02
1
Boiling Heat Transfer in ITER First Wall Hypervapotrons
Dennis Youchison, Mike Ulrickson and Jim BullockSandia National Laboratories
Albuquerque, NM
August 6, 2010
FNST/MASCO/PFC Meeting
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.
DL Youchison 5931/31.02
2
Outline
• What are hypervapotrons?
• Why hypervapotrons?
• Geometry optimization
• Boiling heat transfer in hypervapotrons– Why CFD?
• Benchmarking with HHF test data
• CHF prediction
DL Youchison 5931/31.02
3
• 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 .
Background
DL Youchison 5931/31.02
4
ITER First Wall 04
DL Youchison 5931/31.02
5
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
DL Youchison 5931/31.02
6
What are hypervapotrons?
Hypervapotron FW “finger”
DL Youchison 5931/31.02
7
Two-phase CFD in water-cooled PFCs
Problem: conjugate heat transfer with boiling
• Focus on nucleate boiling regime below criticalheat flux• Use Eulerian multiphase model in FLUENT & Star-CCM+• RPI model (Bergles&Rohsenow)• Features heat and mass transfer between liquidand 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
DL Youchison 5931/31.02
8
Velocity distributions
5 MW/m2
400 g/st=2.05s
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.
DL Youchison 5931/31.02
9
Star-CCM+ 560 k polyhedra mesh
Switches from Eulerian multi-phase mixture to VOF for film boiling.
DL Youchison 5931/31.02
10
CCM+ boiling models were benchmarkedagainst US and Russian test data for rectangularchannels and hypervapotrons to within 10oC.
capability to predict CHF from CFD
Star-CCM+ Results
Surface temperature distribution, t=6.3 s
Case analyzed is a hot “stripe” on a section of the ITER first wall.
DL Youchison 5931/31.02
11
With no boiling, heat transfer is highest under the fins
With boiling, the vapor fraction in grooves is 4%-6% on average
t=6.3 s
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
DL Youchison 5931/31.02
12
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.
DL Youchison 5931/31.02
13
Systematic parameter study performed on rectangular channels – then applied to hypervapotrons.
DL Youchison 5931/31.02
14
Te
mp
era
ture
(C
)
Thermocouple response 3.5 MW/m2 through 6 s
Russian data
Thermocouple response 4.0 MW/m2 through 6 s
Te
mp
era
ture
(C
)
ICHFTrip @ 400 C
Not ss yet!
Rectangular channelresults
15
Russian HV CHF Mock-up
flow
16
Total of 490k poly cells in mesh
Heated area is 100 mm x 48 mm
3 prism layers
17
Surface temperature – 6.0 MW/m2, 1 m/s 115 C inlet, 2 MPa
18
CCM+ solid/fluid interface temperatures for 6.0 MW/m2 @6s
19
Vapor fraction – 6.0 MW/m2 @6s
20
Thermocouple response through 6 s
Russian data
4 s for TCs to ss
21
Outlet temperature close to steady state.
DL Youchison 5931/31.02
22
a) sub-cooledb) nucleate to transition boilingc) film boilingd) sub-cooled
All flow regimes can exist simultaneously.
4.0 MW/m2
115 oC, 2 MPa water1.0 m/s
T:
h:
DL Youchison 5931/31.02
23
CHF Testing Testing of the HV mock-up
Water 2 m/sPabs 10 MW/m2
tpuls 300s
T/C (1.5 mm from CuCrZr surface)
Second pulse at 10 MW/m2)ICHF !