ermsar 2012, cologne, germany, march 21 – 23, 2012 1 improvement of spray modelling for hydrogen...

ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012

1

Improvement of spray modelling for hydrogen risk analysis in a PWR

S. Mimouni1, A. Foissac1,2, J. Malet2, E. Le Coupanec1, A. Schumm1

1 EDF R&D, Chatou (FR) 2 IRSN, Saclay (FR)


2

Spray modelling for hydrogen risk analysis in a PWR

Overview on the advances realized in NEPTUNE_CFD:

Spray modeling.

Validation : CARAIDAS, TOSQAN, PANDA experiments.

Outline the major criticism of the validation plan proposed.

Outline


3

ContextDROPLET PHENOMENA•Heat and mass transfer (evaporation, condensation)•Droplet-wall interaction•Droplet-aerosol interaction not modeled in NEPTUNE_CFD

•Droplet-droplet interaction


4

The NEPTUNE_CFD codeStandard featuresThe code deals with compressible, unsteady, turbulent 3D two-phase or multi-phase flow.

The numerical approach is based on a finite volume co-located cell-centered approach.

Fully-parallelized.

Equations of the two-phase flow model (so-called 6 equation model): mass, momentum and energy balance for both liquid and gas are solved

heat and mass transfer

gasliq

gasliq

VV

TT


5

The NEPTUNE_CFD code : Modelling of the sprayOnly the Drag force is considered.

Gas turbulent kinetic energy Kg and its dissipation rate eg are calculated by using a two-equations K-e approach

combustion

+ 1 Equation which gives the droplet diameter (monodispersed) drag force He stratification interfacial area mass transfer

Mass balance equation of the non-condensable gas (Air – helium). He stratification

Droplet evaporation / Steam condensation on droplets / Steam condensation at wall / Droplet-wall interaction …


6

Validation

CARAIDAS experiment (carried out at IRSN)

TOSQAN experiment (IRSN)

PANDA experiment (PSI)

CALIST experiment (IRSN – EDF)


7

CARAIDAS (IRSN) : cylindrical enclosure used to study the drop evolution under representative conditions.

0,6m

5m

Droplets (T2, D2, U2)

adiabatic wall

droplets

x

z y

D2

Air + vapor (P, T1, HR)

Drop diameter measurements are performed at 3 elevations: top, middle and bottom.


8Tests conditions and Results

Test P (bar) T1 (°C) HR (%) T2 (°C) D2 (m) U2 (m/s) EVAP3 1,00 20,1 20,5 20,6 611 +/-4 3,58

EVAP13 5,42 100,1 15,0 31,0 605 +/-4 3,75

EVAP18 1,00 135,2 3,0 30,9 309 +/-5 3,66

EVAP21 4,29 97,4 15,0 29,2 311 +/-7 3,63

EVAP24 4,97 135,0 4,0 30,3 296 +/-4 3,10

COND1 4,00 141,3 55,0 36,0 341 +/-2 4,90

COND2 4,80 141,6 71,0 37,0 344 +/-2 4,70

COND7 5,30 139,3 87,0 35,0 593 +/-11 2,10

COND10 2,40 121,5 79,0 16,0 673 +/-5 2,10

Sensitivity to the mesh refinement


9

Validation

CARAIDAS experiment (IRSN)





10

Validation : TOSQAN experiment

It is a closed cylindrical vessel (4 m high, 1.5 m internal diameter).

The inner spray system is located on the top of the enclosure on the vertical axis.

full spray cone

7 m3 volume

TOSQAN 113 : dynamical effect of a spray(interaction between a spray and a helium stratification)

TOSQAN 101 : thermodynamical effect of a spray


11TOSQAN 101 : thermodynamical effect of a spray

Initial conditions for the air-steam mixture

Gas Temperature T1 = 120°C

Total Pressure P = 2,5 bar

Relative humidity RH = 75%

Initial conditions for the droplets flowrate Qinj = 30g/s

Droplet temperature T2 = 20°C

Droplet diameter d2 = 200μm

Objective : validation of the modelling of steam condensation on droplets, evaporation of droplets, …

The wall temperature is maintained constant at 120 °C during the whole test.


12Radial profiles just below the nozzle at equilibrium (steady state)

Vapour condenses on the surface of the droplets in the spray region and then the gas temperature decreases . As a result, the droplets temperature increases in the spray region along the vertical axis .


13

Validation






14

14

PANDA : preliminary results

The spray nozzle is oriented vertically downward in vessel 1.It produces a conical solid spray pattern.The two vessels are connected with a 1 m diameter pipe (IP).Ddroplet=0.582mm


1522000 cells


16

16

Initial conditions

Test: ST3_0 (100% Air)A helium rich layer is created in the upper part of the vessel 1, while the remaining volume of v1 and the full volume of v2 is filled with air.


17

ST3_0


18

TD2_1

I15

B20

D15

L26

B18

ST3_0 (100% Air+30% He)

Spray activation causes the break-up of helium-rich layer and results in about mixed v1.

Helium rich mixture.


19

B20

D14

GH14

L26L14

B18C14 C26

GH26

A good agreement is obtained between experimental data and calculations.


20

20

Initial conditions

Test: ST3_2 (60% Steam-40% Air)A helium rich layer is created in the upper part of the vessel 1, while the remaining volume of v1 and the full volume of v2 is filled with the steam-air mixture.


21


22

TD2_1

B20

L26

TD2_5

M15

L15

ST3_2 (60% Steam, 40% Air +30% He)

Helium rich mixture.

• Helium-rich mixture travels through the lower region of the IP.

• Helium-rich mixture accumulates around the mid level of v2.

A qualitative agreement is obtained between experimental data and calculations.Under process.


23

Validation






24Spray system characteristics

Hollow cone swirling spray (60°)

ΔP = 3,5 bar

Flowrate : 1 kg/s

Very few data about droplet size and velocityData necessary for the PWR spray system

numerical simulation-> Measurement on the CALIST experimental

facility to characterize these sprays

4 cm

Hollow cone

10 cm

Smoke

Highlight on the hollow cone structure: Highlight of the gas entrainment generated by the spray:

TOSQAN – PANDA : full cone spray consequences ??


25Characteristics of the simulation

Experimental and numerical results obtained for two interacting sprays are compared for different positions along the symmetrical axis.

Monodispersed Polydispersed


26

0

2

4

6

8

10

0 10 20 30 40 50 60

z=20 cm CALISTz=40 cm CALISTz=60 cm CALISTz=95 cm CALISTz=20 cm NEPT_CFDz=40 cm NEPT_CFDz=60 cm NEPT_CFDz=95 cm NEPT_CFD

0

2

4

6

8

10

0 10 20 30 40 50 60

z=20 cm CALISTz=40 cm CALISTz=60 cm CALISTz=95 cm CALISTz=20 cm NEPT_CFDz=40 cm NEPT_CFDz=60 cm NEPT_CFDz=95 cm NEPT_CFD

5

10

15

20

25

0 10 20 30 40 50 60

z=20 cm CALIST

z=40 cm CALIST

z=60 cm CALIST

z=95 cm CALIST

z=20 cm NEPT_CFD

z=40 cm NEPT_CFD

z=60 cm NEPT_CFD

z=95 cm NEPT_CFD

5

10

15

20

25

0 10 20 30 40 50 60

z=20 cm CALIST

z=40 cm CALIST

z=60 cm CALIST

z=95 cm CALIST

z=20 cm NEPT_CFD

z=40 cm NEPT_CFD

z=60 cm NEPT_CFD

z=95 cm NEPT_CFD

5

10

15

20

25

0 10 20 30 40 50 60

z=20 cm CALISTz=40 cm CALIST


z=20 cm NEPTUNE_CFDz=40 cm NEPTUNE_CFD


5

10

15

20

25

0 10 20 30 40 50 60





0

2

4

6

8

10

0 10 20 30 40 50 60

z=20 cm CALIST

z=40 cm CALIST

z=60 cm CALIST

z=95 cm CALIST

z=20 cm NEPT_CFD

z=40 cm NEPT_CFD

z=60 cm NEPT_CFD

z=95 cm NEPT_CFD

0

2

4

6

8

10

0 10 20 30 40 50 60

z=20 cm CALIST

z=40 cm CALIST

z=60 cm CALIST

z=95 cm CALIST

z=20 cm NEPT_CFD

z=40 cm NEPT_CFD

z=60 cm NEPT_CFD

z=95 cm NEPT_CFD

Axial velocity (m/s) of droplets vs Radial distance (cm)

Radial velocity (m/s) of droplets vs Radial distance (cm) m

on

od

ispersed

po

lydisp

ersed

Two PWR interacting sprays: some results


27

Fréquence de collision

(m-3.s-1)

1e90,75e90,5e9

0,25e90e9

Buse 1 Buse 2

109 collisions.m-3.s-1

Small droplets

Nombre de petites gouttes

par m3

Large droplets

Nombre de grosses gouttes

par m3

•The smallest droplets are drifted away in the air flow.•The biggest droplets, having more inertia, are not altered in the spray interacting area.

Collisions lead to break up

The droplet size decreases: the mean geometric diameter is about 300 µm before spray interaction and about 200 µm after spray interaction.



28

Conclusion about the sectional method with collisions

1. Good agreement between experimental and numerical.

2. But some limits still exist to simulate a whole severe accident (improve the modeling of the droplet collision, calculations are time-consuming).


29

Conclusion

Results of the code-experiment comparison on CARAIDAS (tests on single water droplets), TOSQAN and PANDA tests give satisfactory agreement with a monodispersed approach.

Mesh convergence has been carefully investigated.

But TOSQAN + PANDA = full spray cone.

CALIST experiment : PWR spray system = hollow spray cone.

Collect of data about droplet size and velocity

Modeling the droplet size and velocity polydispersion

Modeling the droplet collisions

Numerical simulation of two interacting PWR sprays

Some questions still exists: How quantify/validate the gas turbulence (inlet condition in combustion

calculation) ?

Interaction between a helium stratification and a hollow spray cone ?


30References

S. Mimouni, J.-S. Lamy, J. Lavieville, S. Guieu, and M. Martin, “Modelling of sprays in containment applications with a CMFD code”, Nuclear Engineering and Design, Vol. 240 (9), 2010, pp 2260–2270.

S. Mimouni, N. Mechitoua, M Ouraou, “CFD Recombiner Modelling and Validation on the H2-Par and Kali-H2 Experiments”, Science and Technology of Nuclear Installations, Volume 2011 (2011), Article ID 574514, 13 pages, doi:10.1155/2011/574514.

S. Mimouni, N. Mechitoua, A. Foissac, M Ouraou, “CFD Modeling of Wall Steam Condensation: Two-Phase Flow Approach versus Homogeneous Flow Approach”, Science and Technology of Nuclear Installations, Volume 2011 (2011), Article ID 941239, 10 pages.

S. Mimouni, A. Foissac, J. Lavieville, “CFD modelling of wall steam condensation by a two-phase flow approach”, Nuclear Engineering and Design, Volume 241, Issue 11, November 2011, Pages 4445-4455.

S. Mimouni, A. Foissac, J. Malet, A. Schumm, J. Laviéville, « Improvement of spray modelling for hydrogen risk analysis in a PWR”, ERMSAR 2012

A. Foissac, J. Malet, R.M. Vetrano, J.M. Buchlin, S. Mimouni, F. Feuillebois and O. Simonin, “Experimental measurements of droplet size and velocity distributions at the outlet of a pressurized water reactor containment swirling spray nozzle”, Proceedings of XCFD4NRS-3, Washington D.C., USA, 2010 Atomization and Sprays, 2011, accepted.

A. Foissac, J. Malet, S. Mimouni and F. Feuillebois, “Binary water droplet collision study in presence of solid aerosols in air”, Proceedings of the 7th ICMF, Tampa, USA, 2010.

A. Foissac, J. Malet, S. Mimouni, P. Ruyer, F. Feuillebois and O. Simonin , “Eulerian simulation of interacting PWR sprays : influence of droplet collisions”, NURETH-14, Toronto, Ontario, Canada, September 25-30, 2011

J. Malet, L. Blumenfeld, S. Arndt, M. Babic, A. Bentaib, F. Dabbene, P. Kostka, S. Mimouni, M. Movahed, S. Paci, Z. Parduba, J. Travis, E. Urbonaviciusk “Sprays in containment: Final results of the SARNET spray benchmark”, Nuclear Engineering and Design, Volume 241, Issue 6, June 2011, Pages 2162–2171

J. Malet, T. Gelain, . Mimouni, G. Manzini, S. Arndt, W. Klein-Hessling, Z. Xu, M. Povilaitis, L. Kubisova, Z. Parduba, S. Paci, N.B. Siccama, M.H. Stempniewicz, “HEAT AND MASS TRANSFER MODELLING OF SINGLE DROPLET FOR CONTAINMENT APPLICATIONS – SARNET-2 BENCHMARK “, ERMSAR 2012.


31Droplets condensation/evaporation

Computation of Sh and Nu numbers : relations of Frössling / Ranz-Marshall

Tabulated laws : D(Tm), ρsat(T2), λ1(Tm)

12

211

''

HHc

gdmgd

dg

vgdsatmd

dcg

TTTNud

transferheat

yTTDShd

transfermass

).(.6

':_

)().(.6

:_

2

2

3/12/1

3/12/1

PrRe56,02

Re56,02

Nu

ScSh

diffusion coefficient

thermal conductivity

d : droplet

g : gas

Vapor mass fraction

Vapor density at saturation state at Tdroplet

Vapor density at Tgas

gasliq

gasliq

VV

TT


32

1) Accurate study of PWR spray system

2) Modeling the droplet size and velocity polydispersion

3) Modeling the droplet collisions

4) Numerical simulation of two interacting PWR sprays


33Sectional method developped in NEPTUNE_CFD code

Development of the sectional approach into the NEPTUNE_CFD code

Cutting the size distribution into sectionsSolving the equilibrium equations for each section:- mass- momentum- enthalpy

Equation closure terms:- turbulence (+ inverse coupling)- drag (between sections and gaseous phase)- collision terms (mass and momentum transfers)

1 size <-> 1 velocity0

0.2

0.4

0.6

0.8

1

0

No

rma

lize

d n

um

be

r o

f d

rop

lets

D1 D2 D3 D4 D5

Monodispersed Polydispersed


34

1) Accurate study of PWR spray system

2) Modeling the droplet size and velocity polydispersion

3) Modeling the droplet collisions

4) Numerical simulation of two interacting PWR sprays


35

Outcome of the collision between droplets:

ls ddb

2

23

22

1112

dUWe s

Symmetrical Weber number (Rabe et al. 2010)

Impact parameter

Experimental maps of collision

outcomes and definition of the

transitions0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2 2.5 3Nombre de Weber symétrique Wes

Par

amètr

e d'im

pac

t b

Bouncing

Coalescence

Stretching Separation

Reflexive Separation

Symmetrical Weber Number

Imp

act p

ara

mete

r

Bouncing CoalescenceStretchingSeparation

ReflexiveSeparation Splashing

= dl+ds


36Modeling the outcome of a collision between droplets m and n

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 0,5 1 1,5 2 2,5 3

2) Calculation of Weber number between m and n

3)

Ou

tcom

e d

istr

ibu

tion

Bouncing

Stretching

Coalescence

Reflexion

4) Identification of resultingdroplet properties

No modification

No modification

Birth of one droplet of section k

Birth of 3 dropletsof section k’

Mass and momentumtransfers from sections

m and nto section k

Mass and momentumtransfers from sections

m and nto section k’

Splashing(for We>10)

Impact

para

mete

r

Birth of 20 dropletsof section k’’

1) Calculation of the collision rate between m and n

Map of binary collision outcome


37Characteristics of the simulation

Inlet conditions: definition of 9 sections for each nozzle

Section Diameter Flowrate

1 55 µm 1.42 10-5 kg/s

2 166 µm 2.67 10-2 kg/s

3 277 µm 1.28 10-1 kg/s

4 388 µm 1.91 10-1 kg/s

5 500 µm 2.02 10-1 kg/s

6 611 µm 1.72 10-1 kg/s

7 722 µm 1.29 10-1 kg/s

8 833 µm 8.87 10-2 kg/s

9 944 µm 6.35 10-2 kg/s

Experimental and numerical local size distributions obtained for two interacting sprays are compared for different positions along the symmetrical axis :


38


0

100

200

300

400

500

600

-40 -20 0 20 40

X (cm)

d10

(µm

)

CALISTNEPTUNE_CFD

0100200300400500600700800

-40 -20 0 20 40

X (cm)

d32

(µm

)

CALISTNEPTUNE_CFD

0

5

10

15

20

25

30

-40 -20 0 20 40

X (cm)

Uz

(m/s

)

CALISTNEPTUNE_CFD

0

5

10

15

20

25

30

-40 -20 0 20 40

X (cm)

Uz

(m/s

)

CALISTNEPTUNE_CFD

0100200300400500600700800

-40 -20 0 20 40

X (cm)

d32

(µm

)

CALISTNEPTUNE_CFD

0

200

400

600

800

-40 -20 0 20 40

X (cm)

d32

(µm

)

CALISTNEPTUNE_CFD

0

100

200

300

400

500

600

-40 -20 0 20 40

X (cm)

d10

(µm

)

CALISTNEPTUNE_CFD

0

100

200

300

400

500

600

-40 -20 0 20 40

X (cm)

d10

(µm

)

CALISTNEPTUNE_CFD

0

5

10

15

20

25

30

-40 -20 0 20 40

X (cm)

Uz

(m/s

)

CALISTNEPTUNE_CFD

Mean droplets are well predicted by the code. Results are better far from the nozzle.

Z=

60 c

mZ

=80 c

mZ

=100 c

m

Differences for high X.Work on momentum terms

necessary

ermsar 2012, cologne, germany, march 21 – 23, 2012 1 improvement of spray modelling for hydrogen...

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