Numerical prediction of single-phase flow mixing characteristics in a 1/12th of the cross segment of a 54-rod bundle

Numerical simulations of selected subchannel tracer (Potassium Nitrate) based experiments have been performed to study the capabilities of state-of-the-art of Computational Fluid Dynamics (CFD) codes. A Reynolds stress model (RSM) has been selected as the primary turbulence model to be applied for the simulation case as it has been previously found reasonably accurate to predict flows inside rod bundles. As a comparison, the case is also simulated using a standard k-epsilon turbulence model that is widely used in industry. Flow enters into the computational domain through the mass inflow at the three subchannel faces. Simulation results have been extracted at different locations of the mixing zone and downstream zone. The local mass fraction shows uniform mixing. In present investigation using the species transport model, includes the study of diffusion of two fluids (water and KNO3) to study its interaction and how mixing is enhanced. The species model is concerned with the transport of species with in this phase, where it is experimentally found that our species are completely miscible. The effect of the applied turbulence model is nearly negligible just before the outlet plane because the distributions look like almost identical and the flow is fully developed. On the other hand, quantitatively the dimensionless mixing scalar distributions change noticeably, which is visible in the different scale of the colour bars.