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/ 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/ 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/ Star-CCM+ Version , 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, (2010). Upcoming paper in the 2010 TOFE. Background
DL Youchison 5931/ ITER First Wall 04
DL Youchison 5931/ 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/ What are hypervapotrons? Hypervapotron FW “finger”
DL Youchison 5931/ 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/ Velocity distributions 5 MW/m 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/ Star-CCM+ 560 k polyhedra mesh Switches from Eulerian multi-phase mixture to VOF for film boiling.
DL Youchison 5931/ 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/ 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/ 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/ Systematic parameter study performed on rectangular channels – then applied to hypervapotrons.
DL Youchison 5931/ 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 400 C Not ss yet! Rectangular channel results
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/m 2, 1 m/s 115 C inlet, 2 MPa
18 CCM+ solid/fluid interface temperatures for 6.0 MW/m
19 Vapor fraction – 6.0 MW/m
20 Thermocouple response through 6 s Russian data 4 s for TCs to ss
21 Outlet temperature close to steady state.
DL Youchison 5931/ a)sub-cooled b)nucleate to transition boiling c)film boiling d)sub-cooled All flow regimes can exist simultaneously. 4.0 MW/m o C, 2 MPa water 1.0 m/s T: h:
DL Youchison 5931/ CHF Testing Testing of the HV mock-up Water 2 m/s P abs 10 MW/m 2 t puls 300s T/C (1.5 mm from CuCrZr surface) Second pulse at 10 MW/m 2 ) ICHF !