Influence of Numerical Tools on the Flow and Heat Transfer of Super-Critical Water

Abstract

In a Supercritical Water Reactor (SCWR) the reactor core is cooled with supercritical water (SCW). For the design and operation of a SCWR, the characteristics of the heat transfer from the fuel rods to the SCW coolant needs to be well understood. These heat transfer characteristics are complex and cannot be captured by the correlations that are currently available in literature. Predicting the heat transfer to SCW has also become a challenge for Computational Fluid Dynamics (CFD) models. In the present study, the influence of numerical tools on the supercritical water flowing through a heated tube configuration has been investigated in preparation for analyses of a rod bundle validation case. A wide range of 2D axi-symmetrical and full 3D calculations are performed and compared for the SCW tube experiments of Yamagata and Ornatskiy. In addition, different meshing techniques, i.e. hybrid (hexa- and polyhedral), were used to achieve an optimal mesh resolution for such high Prandtl number flows. Furthermore, the influence of the applied meshing strategy in the transition from near wall to bulk region has been investigated for the prediction of the overall flow topology and heat transfer.