Three-dimensional simulation of a simplified advanced gas-cooled reactor fuel element

The present work involves simulations of a simplified three-dimensional representation of the UK fleet of advanced gas-cooled reactors (AGRs) fuel element using a 30° sector configuration. The computations were carried out using the v²-f formulation which was shown to be one of the most accurate turbulence models in earlier simulations of two-dimensional rib-roughened channels. In the present work main features of the mean flow and heat transfer in the fuel element were identified and discussed. The pressure loss and friction factor were also calculated where good agreement with the experimental correlations was found. Further comparisons were made against simulations of a 2D rib-roughened channel in order to assess the validity and relevance of a '2D approximation' approach. It was shown that although a two-dimensional approach is very useful and economical for 'parametric studies', it does not provide an accurate representation of a 3D fuel element configuration, especially for the velocity and pressure coefficient distributions, where large discrepancies were found between the results of the 2D channel and azimuthal planes of the 3D configuration.