WP4: Safety and Performance for Innovative Reactor Systems

3rd Annual Meeting, Imperial College London, 9th April 2008

Reynolds-Averaged Navier-Stokes (RANS) investigation of Advanced Gas-Cooled Reactors

(AGRs)

by

Amir Keshmiri

School of Mechanical, Aerospace & Civil Engineering (MACE)The University of Manchester

Manchester M60 1QD

OutlineOutline

• Topic 1: Ascending Flow in a Heated Pipe under Post-trip Condition

• Topic 2: Modelling the Coolant in the AGR’s Fuel Elements

• Topic 3: Development of Wall Functions

• Future Work

Topic 1:Topic 1:

Ascending Flow in a Heated Pipe under Post-trip

Condition

Solution MethodsSolution Methods

• In-House Code (CONVERT)In-House Code (CONVERT)

• Commercial CFD Package (STAR-CD)Commercial CFD Package (STAR-CD)

• Industrial Code (Code_Saturne)Industrial Code (Code_Saturne)

• or

• Radius=0.1 m

• Ascending Flow

• Constant Heat Flux BC

• ‘Boussinesq’ Approximation

180Reτ 5300ReD

Key Features of the Flow ProblemKey Features of the Flow Problem

The analysis focuses on 4 cases:

• Gr/Re^2=0.000 Forced Convection

• Gr/Re^2=0.063 Early onset Mixed Convection

• Gr/Re^2=0.087 Laminarization

• Gr/Re^2=0.241 Recovery

Test CasesTest Cases

Models TestedModels 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) – presented by Dr. Yacine Addad

The Results are validated against:

• DNS of You et al (2003)

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0.01 0.1 1 10Bo

Nu

/Nu

0

Launder & Sharma Model Cotton & Ismael Model Suga ModelData of Carr et al (1973)DNS of You et al (2003) Launder & Sharma Model (Desc. flow)Cotton & Ismael Model (Desc. flow)Suga Model (Desc. flow)Data of Easby (1978) (Desc. flow)Data of Parlatan et al (1996) (Desc. flow)DNS of You et al (2003) (Desc. flow)

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

0.01 0.1 1 10Bo

Nu

/Nu

0

Launder & Sharma Model (CONVERT)Large Eddy Simulation (STAR-CD)Data of Steiner (1971)Data of Carr et al (1973)Data of Parlatan et al (1996)DNS - You et al (2003)

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

0.01 0.1 1 10Bo

Nu

/Nu

0

Launder & Sharma Model (CONVERT)

Suga Non-Linear Eddy Viscosity Model (CONVERT)

k-omega-SST Model (STAR-CD)

k-omega-SST Model (Code_Saturne)

Large Eddy Simulation (STAR-CD)

DNS - You et al (2003)

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

0.01 0.1 1 10Bo

Nu

/Nu

0

Launder & Sharma Model (CONVERT)

k-omega-SST Model (STAR-CD)

Lien & Durbin v2f Model (STAR-CD)

Manchester v2f Model (Code_Saturne)

Large Eddy Simulation (STAR-CD)

DNS - You et al (2003)

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

0.01 0.1 1 10

Bo

Nu

/Nu

0

Launder & Sharma Model (CONVERT)Cotton & Ismael Model (CONVERT)Suga Non-Linear Eddy Viscosity Model (CONVERT)Lien-Chen-Leschziner k-eps 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 (STAR-CD)DNS - You et al (2003)

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Bo

Nu

/Nu

0

Launder & Sharma Model (CONVERT)Cotton & Ismael Model (CONVERT)Suga Non-Linear Eddy Viscosity Model (CONVERT)Lien-Chen-Leschziner k-eps 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 (STAR-CD)DNS - You et al (2003)

Topic 2:Topic 2:

Modelling the Coolant in the AGR’s Fuel Elements

Advanced Gas-Cooled Reactors (AGRs)Advanced Gas-Cooled Reactors (AGRs)

1. Charge tubes2. Control rods3. Graphite moderator4. Fuel assemblies5. Concrete pressure vessel and radiation shielding6. Gas circulator7. Water8. Water circulator9. Heat exchanger10. Steam

Fuel ElementFuel Element

Axis of symmetry

Transverse Ribs

Work in progress:Work in progress:

Multi-Start Rib-Roughened Fuel Elements

Helical/Spiral Ribs

Topic 3:Topic 3:

Development of Development of Wall Functions

Wall FunctionsWall 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.

AWF Results in Ascending Pipe FlowAWF Results in Ascending Pipe Flow

• Running STAR-CD for “Spiral Ribs” and measure the effects of CO2 Particle deposition on the heat transfer.

• 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 and validation against TEAM/STREAM Codes.

Future WorksFuture Works

THE ENDTHE ENDTHANK YOUTHANK YOU