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

conxita.lifante@ansys.com

C. Lifante, T. Frank, A. BurnsANSYS

conxita.lifante@ansys.comconxita.lifante@ansys.com

D. Lucas, E. KrepperForschungszentrum

conxita.lifante@ansys.com

D. Lucas, E. KrepperForschungszentrum

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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

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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

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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

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• 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

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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

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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

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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

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y

TOPFLOW Test Facility @ FZD8m

L~ 8

D=195mm

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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

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– 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

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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)

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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

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Results: Vapor Volume Fraction

© 2009 ANSYS, Inc. All rights reserved. 22 ANSYS, Inc. ProprietaryConfig 2 Config 3Config 1

Results: Vertical averaged steam distribution

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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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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

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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

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p pbased on ANSYS CFX 12

Th k Y !Thank You!© 2009 ANSYS, Inc. All rights reserved. 30 ANSYS, Inc. Proprietary