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Prediction of Polydisperse Steam
Prediction of Polydisperse Steam Polydisperse Steam
Bubble Condensation in Subcooled Water using
th I h
Polydisperse Steam Bubble Condensation in Subcooled Water using
th I h the Inhomogeneous MUSIG Model
the Inhomogeneous MUSIG Model
C. Lifante, T. Frank, A. BurnsANSYS
C. Lifante, T. Frank, A. BurnsANSYS
[email protected]@ansys.com
D. Lucas, E. KrepperForschungszentrum
D. Lucas, E. KrepperForschungszentrum
© 2009 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary
Forschungszentrum Dresden-RossendorfForschungszentrum Dresden-Rossendorf
Outline
• Motivation• Model descriptionp• Validation
– TOPFLOW facility & condensation experimentTOPFLOW facility & condensation experiment– CFD Experiment comparison
• Previous approaches vs. extended MUSIG pp• Improvements in the extended MUSIG simulations
• Summary & conclusions
© 2009 ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary
y
Outline
• Motivation• Model descriptionp• Validation
– TOPFLOW facility & condensation experimentTOPFLOW facility & condensation experiment– CFD Experiment comparison
• Previous approaches vs. extended MUSIG pp• Improvements in the extended MUSIG simulations
• Summary & conclusions
© 2009 ANSYS, Inc. All rights reserved. 3 ANSYS, Inc. Proprietary
y
Motivation
• NRS applications:– Subcooled boiling in nucl. react fuel assemblies– Steam injection into pools– Steam bubble entrainment in subcooled liquids
by impinging jets
C d / t d d IAD• Cond./evap. rates depend on IAD bubble size distributionNeed of polydispersed• Need of polydispersedinhomogeneous simulations
• Need to deal with phase
© 2009 ANSYS, Inc. All rights reserved. 4 ANSYS, Inc. Proprietary
• Need to deal with phase change effects
Outline
• Motivation• Model descriptionp• Validation
– TOPFLOW facility & condensation experimentTOPFLOW facility & condensation experiment– CFD Experiment comparison
• Previous approaches vs. extended MUSIG pp• Improvements in the extended MUSIG simulations
• Summary & conclusions
© 2009 ANSYS, Inc. All rights reserved. 5 ANSYS, Inc. Proprietary
y
Standard Inhomog. MUSIG Model
• Polydisperse fluids •Small bubbles move with the fluid phase
d1 d3 d4 d5 d6 d7 d8d2•Large bubbles are more influenced by
v1 v2 v3
buoyancy
•Lift coefficient changes its sign at a critical size;depends on (p T)Velocity group mass transfer
© 2009 ANSYS, Inc. All rights reserved. 6 ANSYS, Inc. Proprietary
depends on (p,T)
Break up Coalescence
Standard Inhomog. MUSIG Model
• MUSIG setup:– Definition of the initial diameter classes (di)
• Mass classes used – Definition of velocity groups (vj)
• Homogeneous/Inhomogeneous• Which di belong to each vj
– 1 size fraction equation for each bubble diameter
– 1 momentum equation for each velocity group
© 2009 ANSYS, Inc. All rights reserved. 7 ANSYS, Inc. Proprietary
Model Extension description
• Basic population balance equationsNew terms
dn(m, r, t) n(m, r, t) U(m, r, t)n(m, n(m, r, t) m(r, t)dt
r, t)m tt r
B D B D
• Size fraction equations
B B C CB D B D Bubble number density
Breakup/Coalescence terms
Size fraction equations
B B C C
ji d i i d i i B D B Dj i( r f ) ( r U f ) S S S S
t xS
i ii i 1
i i 1 i 1 i
m mm m m m
Si=
for evaporation
≈≈© 2009 ANSYS, Inc. All rights reserved. 8 ANSYS, Inc. Proprietary
i ii 1 i
i i 1 i 1 i
m mm m m m
Si
for condensation iii
i
ii ≈≈
Outline
• Motivation• Model descriptionp• Validation
– TOPFLOW facility & condensation experimentTOPFLOW facility & condensation experiment– CFD Experiment comparison
• Previous approaches vs. extended MUSIG pp• Improvements in the extended MUSIG simulations
• Summary & conclusions
© 2009 ANSYS, Inc. All rights reserved. 9 ANSYS, Inc. Proprietary
y
TOPFLOW Test Facility @ FZD8m
L~ 8
D=195mm
© 2009 ANSYS, Inc. All rights reserved. 10 ANSYS, Inc. Proprietary
Courtesy of FZD
Condensation Test Case
• P=2 [MPa]• Jw=1.0 [m/s]• Js=0.54 [m/s]s [ ]• Ts=214.4 [C]• Tw=210.5 [C] ∆Tw=3.9 [K]Tw 210.5 [ C] ∆Tw 3.9 [K]• Dinj = 1 [mm]• Detailed experimental data:Detailed experimental data:
– Bubble size distributionRadial steam volume fraction distribution
© 2009 ANSYS, Inc. All rights reserved. 11 ANSYS, Inc. Proprietary
– Radial steam volume fraction distributionDirk Lucas, Horst-Michael Prasser: “Steam bubble condensation in sub-cooled water in case of co-current vertical pipe flow”,Nuclear Engineering and Design, Volume 237, Issue 5, March 2007, Pages 497-508
Condensation Test Case
E i t l di l
Experimental bubble size distribution
Experimental radial vapor distribution
© 2009 ANSYS, Inc. All rights reserved. 12 ANSYS, Inc. Proprietary
Numerical Setup
• 1/6 of geometry simulated, 60• Symmetry b.c.• 260.442 elements*• 12 x Injection nozzles modeled
by SOURCE POINTS– Dinj modified (4mm) for vinj
• SST turbulence model• Fdrag, Flift, FTD considered
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Physical Model Setup
• Locally Monodisperse– Particle diameter: constant number of bubbles
dP=dP(dP|Inlet, NP|Inlet)• Standard MUSIG & Extended MUSIG
– 25 bubble size classes– 3 velocity groups:
03 [mm],36 [mm], 630 [mm]– Break up model: Luo & Svendsen (FB=0.025)– Coalescence model: Prince & Blanch (FC=0.05)
© 2009 ANSYS, Inc. All rights reserved. 14 ANSYS, Inc. Proprietary
C
Results: Vertical averaged steam distribution
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Injection nozzles Pipe end
Results: Radial steam distribution
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Results: Radial steam distribution
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Results: Bubble size distribution
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Results: Bubble size distribution
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Results: Tests Comparison
Config 1
Config 2
Config 3
Config 2
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TOPFLOW Condensation case
Config 1 Dinj = 4mm Source point @ W ll - - -Config 1 Dinj 4mm Wall
Config 2 Dinj= 4 mm Source point @ 75 mm FWLF CTD=1.5 Nu=2+0.15Rep
0.8Pr0.5
Config 3 Dinj= 1 mm Source point @ 75 mm FWLF CTD=1.5 Nu=2+0.15Rep
0.8Pr0.5
© 2009 ANSYS, Inc. All rights reserved. 21 ANSYS, Inc. Proprietary
Results: Vapor Volume Fraction
© 2009 ANSYS, Inc. All rights reserved. 22 ANSYS, Inc. ProprietaryConfig 2 Config 3Config 1
Results: Vertical averaged steam distribution
© 2009 ANSYS, Inc. All rights reserved. 23 ANSYS, Inc. Proprietary
Results: Radial steam distribution
© 2009 ANSYS, Inc. All rights reserved. 24 ANSYS, Inc. Proprietary
Results: Radial steam distribution
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Results: Bubble size distribution
© 2009 ANSYS, Inc. All rights reserved. 26 ANSYS, Inc. Proprietary
Results: Bubble size distribution
© 2009 ANSYS, Inc. All rights reserved. 27 ANSYS, Inc. Proprietary
Outline
• Motivation• Model descriptionp• Validation
– TOPFLOW facility & condensation experimentTOPFLOW facility & condensation experiment– CFD Experiment comparison
• Previous approaches vs. extended MUSIG pp• Improvements in the extended MUSIG simulations
• Summary & conclusions
© 2009 ANSYS, Inc. All rights reserved. 28 ANSYS, Inc. Proprietary
y
Summary & Conclusions
• An extension of the MUSIG model in ANSYS CFX in order to catch phase change effect was implemented
• Condensation case at the TOPFLOW geometry used for validationfor validation
• The comparison with previous approaches proved the necessity of the extension
• Qualitatively better results, however improvements in the Setup were requiredA parameter study led to also quantitative• A parameter study led to also quantitative satisfactory results
• Implementation performed in a customized solver
© 2009 ANSYS, Inc. All rights reserved. 29 ANSYS, Inc. Proprietary
p pbased on ANSYS CFX 12
Th k Y !Thank You!© 2009 ANSYS, Inc. All rights reserved. 30 ANSYS, Inc. Proprietary