Lead-Bismuth Eutectic (LBE), a promising coolant for generation IV nuclear reactors, exhibits a distinct low Prandtl number (Pr≈0.01~0.025) compared to conventional fluids like air or water (Pr>0.7). This unique property fundamentally alters its turbulent heat transfer behavior, yet systematic investigations into LBE's thermal transport mechanisms under turbulence remain scarce, limiting its engineering applications.

This study aims to simulate four-equation model for turbulent heat transfer in liquid LBE flows with multi-channel structure so as to provide theoretical support for optimizing reactor thermal-hydraulic designs and safety protocols.

A four-equation turbulence model (k-ε-k_θ-ε_θ) was implemented in commercial software STAR-CCM+ to resolve both momentum and thermal fields. Firstly, the turbulent thermal diffusivity was derived by solving the turbulent thermal energy and thermal dissipation rate transport equations using a passive scalar approach. Subsequently, the turbulent thermal diffusivity was coupled with the turbulent viscosity from the k-ε model to dynamically evaluate the turbulent Pr. Three canonical configurations, i.e., fully developed parallel plate flow, pipe flow, and rod bundle channel flow, were simulated to validate the model across representative geometries.

Simulation results show that the four-equation model can successfully capture key low-Pr thermal features, resulting a good linear relationship between dimensionless temperature and wall-normal distance in the viscous sublayer of parallel plate flow, consistent with theoretical predictions; For pipe and rod bundle flows, simulated Nusselt numbers agree closely with experimental data, demonstrating accuracy in predicting wall heat flux.

Results of this study demonstrate that the k-ε-k_θ-ε_θ four-equation model is a promising framework for modeling LBE turbulent heat transfer, overcoming limitations of constant turbulent Pr assumptions in classical models.