Thermo-fluid Analysis of Helium cooling solutions for the HCCB

TBM

Presented By: Manmeet Narula

Alice Ying, Manmeet Narula, Ryan Hunt and M. Abdou

ITER –TBM meetingUCLA May 10-11 2006

Outline

• Thermo-fluid analysis of first wall cooling strategies for HCCB TBM sub-modules.– Introduction to SC/Tetra® by CRADLE Co Ltd.– Results from preliminary design activity for the first wall helium

cooling system

• Steps toward developing an Integrated Modeling capability for TBM design.– Coupling of SC/Tetra thermo-fluid analysis with ANSYS®

thermal stress calculations

HCCB sub-module cooling solution

Helium at 8 MPa 573K at a flow rate of 0.32 kg/s

HCCB TBM sub-module

Helium flow path

First wall cooling channel

First wall cooling system with 16 channels

Design Analysis Approach

CAD model CADthru

SC/Tetra

ANSYS

.MDL file format input to SC/Tetra preprocessor

SCTPre

SCTsolver

SCTpost

FLDUTIL

.cdb file format to input geometry and temperature load for ANSYS

Thermo-fluid Analysis

Velocity Temperature Pressure in fluid domain

Temperature in solid domain

Thermal Stress Analysis

Stress and Strain in the solid domain

Transient and steady state thermal stress Analysis

Fix CAD model

.MDL model

SC/Tetra® by CRADLE

• SC/Tetra is a CFD system designed specifically for CAE activities for systematic product design.– Versatile and Robust CAD interface (CADthru)– A fast and efficient hybrid mesh generator– High speed optimized flow solver with parallel processing

capabilities– In built post processor with state of the art data interpretation

and visualization tools– Ability to interface with commercial FEA codes (ANSYS,

NASTRAN, IDEAS) for multi physics analysis

• Widely used in the automotive industry.

SC/Tetra® Features

• Turbulence models– Standard k-e– RNG k-e– Various low Re models for accurate simulation of near wall regions

• Models for fluid solid conjugate heat transfer analysis– Turbulent heat transfer enhancement at the interface (log law)– Phase change heat transfer

• User defined surface and volumetric heating (with spatial and temporal variation)

• Variable properties for the fluid and solid (properties change with time, temperature, flow conditions)

• Models for diffusion of species

• Models for radiation heat transfer

Helium flow analysis in HCCB sub-module: SC/T

• Model comprises inlet and exit manifolds and first wall channels.

• Computational domain includes first wall Be layer (2mm), The RAFS structure and Helium coolant.

• Compressible flow model is used for helium flow with the RNG k-e model to calculate the transfer coefficients.

• A constant heat flux of 0.3 Mw / m2 is imposed on the first wall Be surface during the simulation.

• The helium stream is input at 0.32 Kg/s at a pressure of 8 MPa and temperature of 573 K.

Helium flow analysis in HCCB sub-module: SC/T

• Turbulent heat transfer condition is used at the fluid solid interface. No thermal contact resistance is applied at the RAFS-Be interface on the first wall.

• Adiabatic conditions are used at the interface between the RAFS and the surroundings. (Heat is only transferred to the He coolant)

• Initial temperature of 573 K is applied in the entire domain.

• A total of 3 million elements are used in the analysis.

• Two layers of prismatic elements are placed in the fluid domain within 1mm separation from all solid surfaces for proper calculation of the turbulent heat transfer coefficient.

• The simulation is run until steady state is reached (when solution residuals fall below a pre decided tolerance)

Helium flow model with inlet manifold design A

Velocity distribution contours in the inlet and exit manifold

Helium inlet at 8 MPa 573K at a flow rate of 0.32 kg/s

Automatic hybrid mesh generation based on the Advancing Front method. Octree specification is used as the intermediate interface between the model and the mesh to control the mesh density and quality

Prismatic elements are added at the wall boundaries to ensure accurate capture of boundary layers

Top view: Cross section cut in the middle of helium flow channels

Inlet manifold design A

Front view: Velocity distribution is not uniform in the cooling channels

Helium inlet at 8 MPa 573K at a flow rate of 0.32 kg/s

Temperature distribution in the ferritic steel structure as a result of heat transfer between the first wall Be layer and the helium coolant

Temperature distribution in the first wall Be layer

Surface heat flux on first wall 0.3 Mw / m2

Helium flow model with inlet manifold design B

Velocity distribution contours in the inlet and exit manifold

Helium inlet at 8 MPa 573K at a flow rate of 0.32 kg/s

Velocity distribution in first wall cooling channels (cross sectional view)

Inlet manifold design B

Temperature distribution in the first wall Be layer

Velocity distribution in the helium flow circuit

Manifold design B

Helium inlet at 8 MPa 573K at a flow rate of 0.32 kg/s

Temperature distribution on the Be layer surface exposed to surface heat flux.

Inlet manifold design B

Temperature distribution on the Be layer surface exposed to surface heat flux.

Inlet manifold design A

Incident surface heat flux: 0.3 Mw / m2

Coupled analysis of thermal flow and thermal stress

• The CFD analysis model created from the available CAD geometry for SC/T is used for the FEA analysis by ANSYS. (SC/T uses a node based finite volume method. The nodal field and the mesh can be used by the ANSYS FE model)

• Nodal temperature field in the solid domain is calculated by SC/T. This is used by ANSYS as the temperature load condition

• The tetrahedral mesh and model definitions in the solid domain are selectively exported to ANSYS

• The first order tetrahedral elements used in the thermo-fluid analysis by SC/T are converted to higher order 10 node elements before exporting to ANSYS. The temperature at the new mid nodes is interpolated from the solution field. (FLDUTIL)

• The coupled thermal stress analysis can be steady state or transient

Next steps

• Analyze the complete flow path. (Expected elements ~ 12 million)

• Steady state thermo fluid - thermal stress analysis using SC/T- ANSYS CFD-FEM system

• Transient thermo fluid – thermal stress analysis