Investigation on the applicability of turbulent-Prandtl-number models in bare rod bundles for heavy liquid metals

The study of turbulent heat transfer in heavy liquid metals has been undertaken till now as promising coolants for advanced nuclear fast reactors. However, the low Prandtl number property of liquid metals makes their heat transfer differ from traditional coolants and a constant turbulent Prandtl number is proven to be inappropriate for complex conditions. In this paper, in order to assess the applicability of different turbulent-Prandtl-number models in the bundle flow, turbulent heat transfer in triangular and square lattices with different pitch-to-diameter ratios are simulated. The low Reynolds k-∊ Launder and Sharma turbulence model is adopted for turbulent momentum transport, and different turbulent-Prandtl-number models are used to solve turbulent heat transport. Deviations of these models on overall Nusselt number and local temperature distributions are analyzed. Based on the results achieved, turbulent-Prandtl-number models of Kays and Aoki are recommended for heat transfer simulation in bundle flow. A constant turbulent Prandtl number of 1.5 seems to be also acceptable compared with the recommended turbulent-Prandtl-number models.