Four Parameter Heat Transfer Turbulence Models for Heavy Liquid Metals

In advanced Gen IV nuclear reactors heavy liquid metals are considered as coolant for their high conductivity and specific neutronic properties. These fluids have a very low Prandtl number and show a peculiar heat transfer where conduction can be the dominant mechanism at very high Reynolds numbers. In ordinary fluids various turbulence models are available to match the experimental data: Similarity between velocity and thermal turbulent fields is assumed in almost all commercial Computational Fluid Dynamics codes and the simple eddy diffusivity model with constant turbulent Prandtl number is implemented. In low Prandtl number fluids this model fails to reproduce standard correlations build from experimental data. Therefore it is important to develop new heat transfer turbulence models that are able to reproduce numerically the physical behavior. In this work we present different turbulence models to study the heat transfer in heavy liquid metal turbulent flows. Results obtained with the simple eddy diffusivity model are reported. More complex four parameter turbulence models are also presented and numerical results in simple geometries are reported. For a large range of forced flows with no similarity between velocity and thermal fields a four parameter turbulence model is a powerful tool for predicting the heat transfer.