[PPT] - Multiphase CFD Applied to Steam Condensation Phenomena in the PowerPoint Presentation

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Multiphase CFD Applied to Steam Condensation Phenomena in the Pressure Suppression Pool

Marco Pellegrini - IAE Colin Josey, Emilio Baglietto - MIT

STAR Japanese Conference Yokohama, Japan – June 2nd, 2015

N U P E C

SLIDE 2

BACKGROUND

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3 7 10 13 16 19 22 25 28 31 0.0 0.1 0.2 0.3 0.4 0.5 3/11 12:00 3/11 18:00 3/12 0:00 3/12 6:00 3/12 12:00 3/12 18:00 3/13 0:00 Time after scram [hour] DW Pressure (MPa[abs]) Time [date]

UNIT 3 UNIT 2

RCIC system DW Pressure

earthquake

STAR Japanese Conference, Yokohama, Japan 6/9/2015

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RCIC MAIN DIFFERENCES

0.283 m 1.275 m

UNIT 2 VERTICAL JET UNIT 3 HORIZONTAL JETS

steam flow 2.577 m

0.033 m

0.680 m

Sparger detail

steam flow

1F2 RCIC suspected to have worked

in two-phase flow

1F2 torus suspected to have been

flooded by the tsunami

1F3 RCIC worked at the same time

with cycling SRVs

Bottom closed

STAR Japanese Conference, Yokohama, Japan 6/9/2015

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EXPERIMENTAL ACTIVITIES AND COLLABORATIONS

TITech Facility

G. Gregu, M. Takahashi

pool scrubber SIET Facility

3 m 0.5 m

STAR Japanese Conference, Yokohama, Japan 6/9/2015

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SPARGER STRATEGY

Vent pipe - RCIC 1F2 RCIC 1F3

Petrovich, Int, J. Heat and Mass Tr, 2007

Steam mass flux [kg/m2-s] Diameter [m] Subcooling [K]

T-quencher 0.02 m 0.2 m D D 0.1 m D

STAR Japanese Conference, Yokohama, Japan 6/9/2015

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Petrovich, Int, J. Heat and Mass Tr, 2007.

Steam mass flux [kg/m2-s] Diameter [m] Subcooling [K]

STAR Japanese Conference, Yokohama, Japan

CONDENSATION REGIME MAP

CHUGGING BUBBLING JETTING

Experiment at SIET labs, Italy Visualization by Prof. L. Araneo, POLIMI 6/9/2015

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TITech EXPERIMENT: CHUGGING PHENOMENOLOGY

1000 fps time [ms] Mass flow rate: 3.9 g/s Tpool: 23.7 °C

100

60

pressure [kPa] pressure [kPa]

60

100 0.2 0.4 0.6 1 1.2 1.4 1.6 0.8

65ms: bubble formation at outlet
170ms: bubble collapse
258ms: condensation inside the pipe
599ms: condensation inside the pipe
997ms: condensation inside the pipe
1550ms: bubble formation at outlet
1679ms: bubble collapse

pressure signal – G. Gregu, POLIMI/TITech

STAR Japanese Conference, Yokohama, Japan 6/9/2015

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UNIT 3 RCIC SPARGER

Visualization by L. Araneo, POLIMI

STAR Japanese Conference, Yokohama, Japan

Steam flow Tpool = 30 °C Steam flow

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TWO-FLUID MODEL: MOMENTUM EQUATION

∙

∙

Standard Drag
1

2

4
Phase momentum equation

Interphase momentum transfer

drag force

virtual mass force lift force turbulent dispersion force Schiller-Naumann Tomiyama Bozzano-Dente

correction factor

,

Two-fluid model approach

STAR Japanese Conference, Yokohama, Japan 6/9/2015

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TWO FLUID MODEL: ENERGY EQUATION

∙

∙ ∙ , ∙ ∙

∙

Phase energy equation

∆

∆∆

Source term in the energy equation

interaction length scale area density

Differently from two-fluid for boiling applications, the interaction length scale is generally differently defined from the area density in condensation applications. lt

General bubble surface

STAR Japanese Conference, Yokohama, Japan 6/9/2015

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TWO FLUID MODEL: ENERGY EQUATION

Model Formulation / Reference Large eddy

/

Fortesque and Pearson (1967) Small eddy

/

Banerjee et al. (1968) Surface divergence / / Banerjee (1990) SD no shear 0.3 2.83

/

2.14

/ /

Banerjee (1990) Gas flow T Main historical heat transfer models lt vt

∆∆
Surface renewal period

⁄ ⁄

⁄

⁄

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STAR Japanese Conference, Yokohama, Japan

TWO FLUID MODEL: INTERFACIAL AREA DENSITY

Sauter mean diameter Magnitude of Volume Fraction Gradient

Example of volume fraction 1.00 0.75 0.50 0.25 0.00

volume fraction

3L L

More proper in case of

boiling applications

EULERIAN-EULERIAN TWO-FLUID APPROACH

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COMPRESSIBILITY EFFECT

1.00 0.75 0.50 0.25 0.00

volume fraction

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WATER

Constant or temperature dependent density

STEAM

incompressible

compressible

P ρ Pressure limit

SLIDE 14

TITech EXPERIMENT: MESH SENSITIVITY 0.5 m 0.5 m

200,000 cells 800,000 cells COARSE FINE

TEST CONDITIONS Pipe diameter = 2.7 cm Mass flow rate = 5.58 g/s Mass flux = 9.75 kg/m2-s Pool bulk T = 19 ºC Steam T = 100 ºC (saturated)

STAR Japanese Conference, Yokohama, Japan 6/9/2015

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5 10 15 20 25 30 5 10 15

Condensation mass transfer [g/s]

Time [ms]

CHUGGING AT LARGE SUBCOOLING AND MASS FLUX

1.00 0.75 0.50 0.25 0.00

volume fraction

1.00 0.75 0.50 0.25 0.00

volume fraction

COARSE FINE fine mesh coarse mesh Inlet mass flow rate 5.58 g/s Tpool = 19 ºC Tpool = 19 ºC

STAR Japanese Conference, Yokohama, Japan 6/9/2015

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NON ENCAPSULATING BUBBLE

6.8 ms 6.9 ms 7.0 ms 7.2 ms 6.0 ms 5 10 15 20 25 30 35 40 5 10 15 20 25 30 2.5 5 7.5 10 12.5 Mass transfer [g/s]

Time [ms]

Total area [cm2]

STAR Japanese Conference, Yokohama, Japan 6/9/2015

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CHUGGING: LOW SUBCOOLING AND MASS FLUX

4 2

2

Pressure [kPa] 100 200 300 400

Pressure starts decreasing

below zero due to condensation greater than inlet mass flow rate

f steam
An implosion time is reached at

the minimum pressure value

Afterwards the interface flows in

the pipe and the steams gets compressed interface within the pipe

Marks and Andeed, 1979

implosion SIET facility Pipe diameter = 0.2 m Mass flow rate = 0.1 kg/s Mass flux = 3.18 kg/m2-s Pool bulk T = 65 ºC Steam T = 100 ºC (saturated)

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STAR Japanese Conference, Yokohama, Japan

CHUGGING: PHENOMENA INTERPRETATION

4 2

2

Pressure [kPa] 100 200 300 400

Pressure starts decreasing

below zero due to condensation greater than inlet mass flow rate

f steam
An implosion time is reached at

the minimum pressure value

Afterwards the interface flows in

the pipe and the steams compressed interface within the pipe

Marks and Andeed, 1979

implosion 20 ms 40 ms IMPLOSION LOW PRESSURE INTERFACE MOVING UPWARD

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SLIDE 19

STAR Japanese Conference, Yokohama, Japan

RAYLEIGH-TAYLOR INSTABILITY

g A LIGHT FLUID HEAVY FLUID LIGHT FLUID HEAVY FLUID Gravitation field Accelerating flow field separator

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RAYLEIGH-TAYLOR INSTABILITY

LIGHT FLUID HEAVY FLUID A

steam water

Gravitation field Accelerating flow field g

Psteam Pwater

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STAR Japanese Conference, Yokohama, Japan

APPROACH FOR RTI IMPLEMENTATION

d n dt   

( , , , , ) n f g k A   

Amplitude growth description wave number

2 4 2

n Agk k k     

2 w s

k n Ag k            

Duff et al. Physics of Fluid, 1962 Livescu, Physics of Fluid, 2004 Classic instability theory

n Agk 

acceleration wave number Atwood number viscosity surface tension Livescu Duff Classical theory

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C. Josey, E.

Baglietto, 2013

SLIDE 22

STAR Japanese Conference, Yokohama, Japan

IMPLEMENTATION OF THE RTI IN STAR-CCM+

 

max

3

w s

Ag k     

w w

P g        

2

1

i s

k a            

n t t t te

 

 



Wave number term Acceleration term

ν ν

Duff and Livescu combined model for RTI

Final terms for area growth

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POOLEX: LOW SUBCOOLING AND MASS FLUX

POOLEX facility detail

Experiment conditions at the POOLEX

Pipe diameter = 0.2 m T pool = 62 °C Steam Mass Flux = 8 kg/m2s

velocity inlet pressure

utlet

adiabatic walls

Mesh elements: 405,067

steam inlet

Domain Discretization

STAR Japanese Conference, Yokohama, Japan 6/9/2015

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RTI MODEL RESULTS

Rayleigh-Taylor Instability Model Minimum Area Model

STAR Japanese Conference, Yokohama, Japan 6/9/2015

24 Tpool = 62 ºC Tpool = 62 ºC With RTI model the steam interface re-enters the pipe and a new cycle is started once decrease of interfacial area, turbulence, subcooling creates the proper conditions.

SLIDE 25

MASS TRANSFER COMPARISON

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0.5 1 1.5 2 2.5

mass transfer [kg/s]

time [s] Rayleigh-Taylor Instability model Minimum area model

STAR Japanese Conference, Yokohama, Japan 6/9/2015

25 Bubble at the pipe mouth Inlet mass flow rate 0.3 kg/s Without a model that takes into account the growth of the area the bubble remains

scillating at the outlet

Rayleigh-Taylor Instability adds an exponentially increasing surface area that reproduces the bubble collapse.

SLIDE 26

BUBBLE IMPLSOSION COMPARISON

120 ms 190 ms 210 ms 230 ms

EXP no RTI model RTI model

120 ms 190 ms 210 ms 220 ms

Tanskanen, Ph.D. Thesis 2012

STAR Japanese Conference, Yokohama, Japan 6/9/2015

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TEMPERATURE EVOLUTION

Rayleigh-Taylor Instability Model Minimum Area Model

STAR Japanese Conference, Yokohama, Japan 6/9/2015

27 Wrong prediction of interface movement will tend to overestimate the creation of stratification in the pool.

SLIDE 28

SIET FACILITY - STRATIFICATION

20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0

Temperature [°C] Time [min] TP1 TP2 TP3 TP4 TP5 TP6 TP7 TP8 TP9 TP10 TP11 TP12

Chugging stops

STAR Japanese Conference, Yokohama, Japan 6/9/2015

28 Stratification = 55 ºC

nce chugging is occurring the temperature will be

uniform “almost” independently on the location of the pipe

nce chugging stops stratification starts proportional to

the distance from the surface

SLIDE 29

There is large potential to employ CFD in

severe accident applications (DCC is one of them)

Generally a SA code employs one large node

to model the whole S/C

CFD can be used as informative tool for SA

code but…

… it can be used also for industrial

applications:

– Design operation – Severe Accident Management Guidelines

REMARKS

STAR Japanese Conference, Yokohama, Japan 6/9/2015