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Numerical modelling of direct contact condensation
of steam in BWR pressure suppression pool
system
Gitesh Patel, Vesa Tanskanen, Juhani Hyvärinen
LUT School of Energy Systems/Nuclear Engineering, Lappeenranta University of
Technology, Finland
Nuclear Science & Technology Symposium - NST2016 Helsinki, Finland, 2-3 Nov. 2016
Outlines
Motivation
Objective
POOLEX facility
Numerical models and simulations details
Results
Summary
Current work
Gitesh Patel 2NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
In a BWR, the suppression pool is
one of the key safety systems
during a loss of coolant accident
(LOCA) or safety valve actuation.
Suppression pool provides a large
pressure and heat sink by
condensing vapor into liquid and
absoring the energy disharge from a
reactor vessel.
Motivation
3Gitesh Patel
Containment(a)
(a) http://www.tvo.fi/uploads/File/nuclear-power-plant-units.pdf
NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
Motivation (cont.)
4
The sub-cooling of the pool liquid and the mass flux of injected vapor determine
the character of occuring of direct contact condensation (DCC).
Injected steam interacts with pool water by heat transfer, rapid condensation
and momentum exchange, inducing hydrodynamics loads to the pool
structures.
(a) R. Lahey, and F. Moody, (1993). The Thermal-Hydraulics of a Boiling Water Reactor, 2nd edn. American Nuclear Society.
Gitesh Patel
Schematic of typical regions for condensation modes during SRV or LOCA blowdown in BWR(a)
NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
Objective
To implement two-phase solver of OpenFOAM CFD code
To simulate DCC phenomena appearing in BWR suppression pools
Validation of results
5Gitesh PatelNST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
POOLEX facility
6
The POOLEX (Condensation Pool Experiment) test facility was a scaled down
representation of a suppression pool wetwell.
Gitesh Patel
(a) Laine, J. and Puustinen, M., (2006), Condensation Pool Experiments with Steam using Insulated DN200 Blowdown Pipe,
Research report POOLEX 03/2005, LUT.
NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
POOLEX(a)
POOLEX facility: STB-28 test
The STB-28 test was aimed to investigate steam bubble formulation and its
condensation at the blowdown pipe outlet as a function of pool water temperature.
During the blowdown, seven short time intervals in the range of 12 s to 30 s were
recorded with a higher sampling rate. These sub tests were labelled from STB-28-1
to STB-28-7.
7Gitesh PatelNST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
Numerical models and simulations details
Eulerian-Eulerian two-fluid approach was used in OpenFOAM.
8
Flow turbulence was solved by employing the k-ε turbulence model.
PIMPLE (PISO-SIMPLE) pressure velocity coupling algorithm was applied.
Gitesh Patel
(Energy Eq.)
(Continuity Eq.)
(Momentum Eq.)
NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
The interfacial heat fluxes were solved as,
9
,,, iiSi HTTHTCQ
tL
NuHTC
aibi
bSbiaSai
biaiHH
TTHTCTTHTC
,,
,,
,,
Gitesh Patel
Numerical models and simulations details (cont.)
2
1
PrRe2
tNu
b
ttbt
Lv
Re
4
13
tL 4
1
)(tv
(a)
Hughes and Duffey (1991)
(a) Hughes, E.D., Duffey, R.B., (1991). ‘Direct contact condensation and momentum transfer in turbulent separated flows’. Int. J.
Multiphase Flow 17, 599-619
NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
2D-axisymetric grid
3D grid
• 2D-axisymmetric grid contains 45626 hexahedral cells.
• Full 3D grid contains 302796 hexahedral cells.
Test conditions (STB28-4):
• steam temperature: 379.1 K;
• water temperature: 340.5 K;
• steam mass flow rate at inlet: 0.238 kg/s;
• water in the pool: hydrostatic pressure;
• steam-water interface at t=0 s: 0.76 m in the pipe.
Gitesh Patel 10NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
Numerical models and simulations details (cont.)
Grid Convergence Index (GCI) method was used.
Relative error Extrapolated relative error
Grid Convergence Index (GCI)
Results
Condensation mass flow rate Interfacial area
Gitesh Patel 11NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
12
STB-28 experiment
Gitesh Patel
STB-28-4 (OpenFOAM)
NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
Results (cont.)
Results (cont.)
NEPTUNE_CFD
(V. Tanskanen, 2012)
OpenFOAM
(incompressible solver)
OpenFOAM
(compressible solver)
2D results
Gitesh Patel 13NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
Results (cont.)2D results
• The incompressible is
inadequate for
chugging simulations.
• Visually, the chugging frequency is higher but the amplitude of interface position in
blowdown pipe is lower in the OpenFOAM case than in the NEPTUNE_CFD
simulations.
• The DCC rate in the
OpenFOAM simulations
is relatively high than to
the DCC rate of
NEPTUNE _CFD
simulations.
Gitesh Patel 14NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
Results (cont.)Penetration of the initial steam jet
Eruption and collapse of the bubble
after the steam jet penetration
3D results
Gitesh Patel 15NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
2D-axisymetric grid
• 72089 hexahedral cells.
16Gitesh Patel
PPOOLEX simulations (DCC-05-4 test)
Current work…
NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
Summary
17
The suppression pool is one of the key safety systems of BWR containment.
Two-phase flow solver of OpenFOAM CFD code was implemented.
The HD DCC model based on surface renewal model was employed.
As the reference, the steam blowdown tests of the suppression pool test facilities of
Lappeenranta University of Technology were used.
Previously simulated results of NEPTUNE_CFD code were utilised for the assessment
of OpenFOAM simulations.
The qualitative and quantitate behavior of the steam-water interface agreed well to the
test results in the simulations with the OpenFOAM and NEPTUNE_CFD CFD solvers.
An adequate grid size and compressible solver are crusial for chugging simulations.
Gitesh PatelNST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland
Acknowledgements
The research leading to these results was funded by the Finnish Nuclear Waste
Management Fund (VYR) via SAFIR2014 and SAFIR2018, and Doctoral Programme
for Nuclear Engineering and Radiochemistry (YTERA).
NST 2016, 2-3 Nov., Helsinki Nuclear Engineering, LUT, Finland 18Gitesh Patel
Thank You For Your Attention !