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Modelling of two-phase boiling flows with OpenFOAM-SIAMUF seminar
Kai Fu
Division of Nuclear Reactor Technology, KTH
May 24, 2012
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ObjectiveProject Northnet Roadmap 1: Development of two phase flow with OpenFOAM
Model descriptionGoverning equation and closure laws
Validation case2D/3D uniform heated pipe
Future work
Outline
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Problem description in subcooled two-phase flow
qw' '
Onset of nucleate boiling
Modeling of1. bubble lift off size2. evaporation rate at walls3. condensation rate in the bulk4. bubble movement/distribution
Prediction/validation:1. void fraction2. bubble diameter3. velocities4. liquid temperature
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Objective - Northnet Roadmap 1: Development of two phase flow with OpenFOAM
Why OpenFOAM open source free distribution rather fast growing user base
ANSYS
CD-adapco
CFdesign
Edge
FLOW-3D
NUMECA
OpenFOAM
Phoenics
0 50,000 100,000 150,000 200,000
Posts at cfd-online forum
~ March 2010
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Objective - Northnet Roadmap 1
Mechanistic modeling of two-phase flows and heat transferin fuel assemblies of LWRs in Eulerian method1. wall heat partitioning model 2. interfacial area transport model3. interfacial momentum transfer4. turbulence modeling in two-phase flow5. applicable for both steady-state and transient analyses in 3D geometries6. prediction of onset of critical heat flux
Validation of implemented models 1. adiabatic air-water upward bubbly flow2. subcooled wall boiling two-phase flow
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Model description
Phase continuity equation
Linear momentum conservation equation
M ki Interfacial momentum transfer
drag force, lift force, wall lubrication force, turbulent dispersion force,virtual mass force
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Enthalpy equation
l
ev Cells adjacent to walls
Other cells=
qw=q1qeqq
Interfacial heat transfer
Wall boilingAt near wall cells: wall heat partitioning model
Other cells in the bulk: interfacial heat transfer
Nu=20.6Re0.5Pr0.33
qw=q1qeqq
Model description
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Interfacial area concentration transport equation
BB
BC Random collision, wake entrainment
Turbulence induced
Hibiki and Ishii: air/water adiabaticYao and Morel: improved version, DEBORA exp
Lo, Rao and Zhang: S-Gamma model, droplets/bubbles
ai=6DS
Model description
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Upward pipe flow validation case 1: Bartolomej experiment
Working fluid
p (MPa) G (kg/m2s) qw (kW/m2) Tsub (K)
water 4.5 900 570 58.2
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Upward pipe flow validation case 2: DEBORA experiments
Working fluid
p (MPa) G (kg/m2s) qw (kW/m2) Tsub (K)
R12 1.4/2.6 1980-2980 74-109 17.5-23.4
Void fraction
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Void fraction (continued)
Upward pipe flow validation case 2: DEBORA experiments
Working fluid
p (MPa) G (kg/m2s) qw (kW/m2) Tsub (K)
R12 1.4/2.6 1980-2980 74-109 17.5-23.4
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Liquid temperature
Upward pipe flow validation case 2: DEBORA experiments
Working fluid
p (MPa) G (kg/m2s) qw (kW/m2) Tsub (K)
R12 1.4/2.6 1980-2980 74-109 17.5-23.4
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Future work
Extension of validation case: 3D
1. Validation of mechanistic wall heat partitioning model in a low void fraction (<1%) subcooled flow
2. part of the rod bundles.
aθ
n
t
FSTn
FSTt
FGRt
FGRn
FS
FQS
FP
FG
y
xrθ
iθ
Situ and Hibiki, 2005
Bubble departure: 0, =ttotF
Bubble lift off: 0, =ntotF