Thermal Analysis of Fusion Power Heat Exchange Component

Overview

The thermal performance of a carbon fibre composite-copper (CFC/Cu) monoblock, a sub-component of a fusion reactor divertor, was investigated using image-based finite element modelling. Simpleware software was used to reconstruct and mesh X-ray tomography data and generate micro-structurally faithful models, capturing details such as manufacturing defects. A high-resolution image-based method was verified and validated using a CFC/Cu sample, showing advantages over an idealized CAD and low-resolution model; the method was then used to inspect and quantify the effects of debonding regions at the carbon fibre composite-copper interface. This approach enables insights into 'as manufactured' component performance, demonstrating advantages over CAD methods that cannot faithfully reproduce micro-cracking or porosity.

Characteristics:

Experimental and image-based methods (X-ray tomography) used
Image-based modelling helped understand impact of microfeatures
Simpleware ScanIP and +FE module used to generate a microstructurally faithful finite element model
FEA in ParaFEM (revision 1796) demonstrated that manufacturing defects effected performance
Image-based modelling showed regions to target for improvements

Thanks to

Culham Centre for Fusion Energy: Ll.M. Evans
University of Manchester (School of Materials; IT Services for Research; School of Earth, Atmospheric and Environmental Sciences; School of Mechanical, Aerospace and Civil Engineering):
L. Margetts • L.M. Lever • J. Bushell • T. Lowe • A. Wallwork • M. Schmidt • P.M. Mummery
Politecnico di Torino: V. Casalegno
NETZSCH-Gerätebau GmbH: A. Lindemann

References

Evans et al., 2015. Transient thermal finite element analysis of CFC–Cu ITER monoblock using X-ray tomography data. Fusion Eng. Des., 100, 100–111.

Experimental Testing

The project involved two parts for verifying and validating the image-based technique. Experimental and simulated results were first obtained from a disc-shaped sample of CFC bonded to Cu subjected to Laser Flash Analysis (LFA) to determine thermal properties. Simulations were run using a CAD-based model, a low-resolution model generated from X-ray tomography (Nikon Metrology 225/320 kV, Manchester X-ray Imaging Facility), and a high-resolution model from the same data run in a high performance computing facility. As the high-resolution model showed the closest match to experimental results, the second stage of the tests used this method to simulate the behaviour of a CFC-Cu divertor monoblock mock-up under reactor-like thermal loads.

Image-based Modelling

For both stages of the test, the X-ray scan data was imported to Simpleware software and 3D images converted into models using segmentation techniques such as flood-fill, cavity fill, island removal, manual paint and a recursive Gaussian smoothing filter. The smoothing was used to better describe the curved nature of the geometry. Linear 4-node tetrahedral elements were selected for meshing, with a low and high-resolution mesh created for the CFC-Cu disc study – the higher resolution captured the fine microstructure.

A CAD mesh was also created using a commercial FE package as part of the process. Automatic segmentation enabled multiple phases to be obtained, while manual segmentation was used to remove noise, and images downsampled to reduce computational cost without losing micro-structural detail. Finite element simulations for the CAD model, low-resolution and high-resolution meshes were carried out using ParaFEM (revision 1796).

Simulation & Results

For studying the divertor monoblock, it was desirable to analyse thermal performance due to defects introduced during manufacturing. In this instance the greatest impact was due to the debonding of the CFC from the Cu pipe on one side of the interface. A high-resolution image-based approach was particularly suitable for studying the behaviour of the interface in the monoblock, because the dominating effect of the micro features would not have been captured by CAD modelling.

This technique has broader scope than use for fusion power components and could be used for quality assurance in manufacturing industries where micro-scale features have a significant impact on performance.

Any Questions?

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