ermsar 2012, cologne, germany, march 21 – 23, 2012 1 improvement of spray modelling for hydrogen...
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ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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)
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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ContextDROPLET PHENOMENA•Heat and mass transfer (evaporation, condensation)•Droplet-wall interaction•Droplet-aerosol interaction not modeled in NEPTUNE_CFD
•Droplet-droplet interaction
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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 …
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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Validation
CARAIDAS experiment (carried out at IRSN)
TOSQAN experiment (IRSN)
PANDA experiment (PSI)
CALIST experiment (IRSN – EDF)
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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.
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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Validation
CARAIDAS experiment (IRSN)
TOSQAN experiment (IRSN)
PANDA experiment (PSI)
CALIST experiment (IRSN – EDF)
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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.
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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 .
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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Validation
CARAIDAS experiment (IRSN)
TOSQAN experiment (IRSN)
PANDA experiment (PSI)
CALIST experiment (IRSN – EDF)
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
1522000 cells
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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.
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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ST3_0
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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.
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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B20
D14
GH14
L26L14
B18C14 C26
GH26
A good agreement is obtained between experimental data and calculations.
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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.
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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.
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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Validation
CARAIDAS experiment (IRSN)
TOSQAN experiment (IRSN)
PANDA experiment (PSI)
CALIST experiment (IRSN – EDF)
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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 ??
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
25Characteristics of the simulation
Experimental and numerical results obtained for two interacting sprays are compared for different positions along the symmetrical axis.
Monodispersed Polydispersed
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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=60 cm CALISTz=95 cm CALIST
z=20 cm NEPTUNE_CFDz=40 cm NEPTUNE_CFD
z=60 cm NEPTUNE_CFDz=95 cm NEPTUNE_CFD
5
10
15
20
25
0 10 20 30 40 50 60
z=20 cm CALISTz=40 cm CALIST
z=60 cm CALISTz=95 cm CALIST
z=20 cm NEPTUNE_CFDz=40 cm NEPTUNE_CFD
z=60 cm NEPTUNE_CFDz=95 cm NEPTUNE_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
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
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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.
Two PWR interacting sprays: some results
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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).
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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 ?
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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.
ERMSAR 2012, Cologne, Germany, March 21 – 23, 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
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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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
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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 :
ERMSAR 2012, Cologne, Germany, March 21 – 23, 2012
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Two PWR interacting sprays: some results
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