Transcript EDF_in_UoM-30-01-08.ppt

Meeting with EDF at the University of Manchester – 30/01/2008
Coolant Flows in Advanced Gas-cooled
Reactors
‘Progress in KNOO project’
Presented by
Amir Keshmiri
School of Mechanical, Aerospace & Civil Engineering (MACE)
The University of Manchester
Advanced Gas-Cooled Reactors
(AGRs)
[http://www.gen-4.org]
[http://gt-mhr.ga.com]
Advanced Gas-Cooled Reactors
(AGRs)
[The Safety of the AGR by J M Bowerman (1982)]
Ascending/Descending Flows;
Enhancement/Impairment of Heat Transfer
Nu 
hDe

Bo  8 104
Re D 3.425Pr 0.8
gD4 qw
Gr 
 2
Re D 
Pr 
GrD
UD

 Cp



Key Features of the Flow Problem
• ReD  5300 or Reτ 180
• Radius=0.1 m
• Ascending Flow
• Constant Heat Flux BC
• ‘Boussinesq’ Approximation
Solution Methods
• In-House Code (CONVERT)
• Commercial CFD Package (STAR-CD)
• Industrial Code (Code_Saturne)
Test Cases
The analysis focuses on 4 cases:
•
•
•
•
Gr/Re^2=0.000
Gr/Re^2=0.063
Gr/Re^2=0.087
Gr/Re^2=0.241
 Forced Convection
 Early onset Mixed Convection
 Laminarization
 Recovery
Models Tested
Turbulence Models/Techniques Tested:
•
•
•
•
•
•
•
•
Launder-Sharma k-ε model (CONVERT)
Cotton-Ismael k-ε-S model (CONVERT)
Chen k-ε model (STAR-CD)
Suga NLEVM (CONVERT)
k-ω-SST model (Code_Saturne and STAR-CD)
Lien-Durbin v2f model (Code_Saturne and STAR-CD)
Manchester v2f model (Code_Saturne)
LES (STAR-CD)
The Results are validated against:
• DNS of You et al (2003)
• LS of Kim et al (2006)
Heat Transfer Enhancement/Impairment
1.5
Launder & Sharma Model (CONVERT)
Cotton & Ismael Model (CONVERT)
Suga Non-Linear Eddy Viscosity Model (CONVERT)
Standard k-epsilon Model (STAR-CD)
k-omega-SST Model (STAR-CD)
Lien & Durbin v2f Model (STAR-CD)
k-omega-SST Model (Code_Saturne)
Manchester v2f Model (Code_Saturne)
Large Eddy Simulation
Data of Steiner (1971)
Data of Carr et al (1973)
Data of Parlatan et al (1996)
DNS - You et al (2003)
1.3
Nu/Nu 0
1.1
0.9
0.7
0.5
0.3
0.1
1
Bo
10
Publications
•
Keshmiri, A., Cotton, M.A., Addad, Y., Laurence, D.R. & Billard, F., 2008,
“Refined Eddy Viscosity Schemes and LES For Ascending Mixed Convection
Flows”, 4th Int. Symp. on Advances in Computational Heat Transfer, ‘CHT-08’,
Marrakech, Morocco, 11th-16th May 2008.
•
Keshmiri, A., Cotton, M.A., Addad, Y., Rolfo, S. & Billard, F., 2008, “RANS and
LES Investigations of Vertical Flows in tne Fuel Passages of Gas-Cooled
Nuclear Reactors”, 16th ASME Int. Conf. on Nuclear Engineering, ‘ICONE16’,
Orlando, Florida, USA, 11th-15th May 2008.
•
Keshmiri, A. & Cotton, M.A., 2008, “Turbulent Mixed Convection Flows
Computed Using Low-Reynolds-Number and Strain Parameter Eddy Viscosity
Schemes”, 7th Int. ERCOFTAC Symp. on Engineering Turbulence Modelling
and Measurements ‘ETMM7’, Limassol, Cyprus, 4th-6th June 2008.
•
Addad, Y., Cotton, M.A., Laurence, D.R. & Rolfo, S, 2008, “LES for BuoyancyModified Ascending Turbulent Pipe Flow”, 7th Int. ERCOFTAC Symp. on
Engineering Turbulence Modelling and Measurements ‘ETMM7’, Limassol,
Cyprus, 4th-6th June 2008.
Fuel Elements in AGRs
Fuel Elements in AGRs
Fuel Elements in AGRs
Fuel Elements in AGRs
Fuel Elements in AGRs
Fuel Elements in AGRs
T
w
h
Wall Functions
 Standard Wall Function
• Assume ‘universal’ logarithmic velocity and temperature profiles in evaluation of
wall shear stress, turbulent kinetic energy production and wall temperature.
• Inaccurate results when flow departs from a state of local equilibrium.
• Different versions of this WF are available in STAR-CD, Code_Saturne, TEAM
and STREAM codes.
 Analytical Wall Function
• Based on the analytical solution of the simplified Reynolds equations and takes
into account such effects as convection and pressure gradients as well as the
influence of buoyant forces and changes in the thickness of the viscous
sublayer.
• Has proved to be successful in many flow problems e.g. Buoyant flows.
• Currently available in STREAM and TEAM codes.
 Numerical Wall Function
• Based on an efficient one-dimensional numerical integration of the simplified
LRN model equations across near-wall cells.
• Currently available in STREAM and TEAM codes.
Wall Functions
• Running TEAM/STREAM codes for mixed convection
and ribbed surfaces and evaluate the effectiveness
and performance of AWF.
• Modify the AWF if needed to take into account
different flow problems such as ribbed surfaces.
• Development of Code_Saturne by implementing AWF.
• Validation tests by cross-examining of Code_Saturne
with TEAM/STREAM Codes.
• Testing more complex geometries (mainly nuclear
reactor related flow problems) by Code_Saturne.
THE END
THANK YOU