Presentation on theme: "DL Youchison 5931/31.02 1 Boiling Heat Transfer in ITER First Wall Hypervapotrons Dennis Youchison, Mike Ulrickson and Jim Bullock Sandia National Laboratories."— Presentation transcript:
DL Youchison 5931/31.02 1 Boiling Heat Transfer in ITER First Wall Hypervapotrons Dennis Youchison, Mike Ulrickson and Jim Bullock Sandia 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 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 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
DL Youchison 5931/31.02 8 Velocity distributions 5 MW/m 2 400 g/s t=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 benchmarked against US and Russian test data for rectangular channels and hypervapotrons to within 10 o C. 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 Fluent for nucleate boiling. Heat transfer coefficients increase in grooves where boiling takes place ranging from 12,000 to 13,000 W/m 2 K.
DL Youchison 5931/31.02 13 Systematic parameter study performed on rectangular channels – then applied to hypervapotrons.
DL Youchison 5931/31.02 14 Temperature (C) Thermocouple response 3.5 MW/m 2 through 6 s Russian data Thermocouple response 4.0 MW/m 2 through 6 s Temperature (C) ICHF Trip @ 400 C Not ss yet! Rectangular channel results
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