Study on Influence of Turbulence Model Selection on Prediction of Flow Distribution and Hot Spot Fuel Temperature in Prismatic HTGR Cores

Abstract

CFD analyses were performed for a cross-flow experiment in prismatic HTGR core fuel blocks to investigate the effect of turbulence models on the prediction of the core flow distribution. A transition model was considered in addition to a fully turbulent model because the flow in the coolant channels of the fuel block is turbulent whereas that in the bypass gap between the blocks is laminar. Additional analyses were carried out to investigate how the variation of the coolant channel flow dependence on the turbulence model selection affected the hot spot fuel temperature. The results showed that the gamma-theta transition model led to a better prediction than the others because it reasonably simulated the flow region where the bypass and cross gaps intersected. The result for the hot spot fuel temperature, however, showed that the temperature change caused by the turbulence model selection is so small that it can be absorbed in a margin of the engineering design. Therefore, the fully turbulent model can be used as an efficient alternative to the transition model in the engineering calculation of an HTGR core flow.