Preliminary exploration of liquid metals turbulent heat flux model based on OpenFOAM solver: Second-order differential heat flux model

Abstract

Liquid metal-cooled fast reactors use liquid metals such as lead–bismuth eutectic (LBE) and sodium as the coolant, and the thermo-hydraulic characteristics of liquid metals have a large effect on the thermodynamic parameters of the reactor core. The problem is that using the traditional constant turbulent Prandtl number Pr_t of 0.85 ∼ 0.9, which is generally derived from the Reynolds analogy hypothesis suitable for conventional fluids, will greatly affect the accuracy of the numerical prediction of the thermal–hydraulic properties of liquid metals. In order to obtain more accurate liquid LBE and sodium turbulent heat transfer data, this research introduces a second-order differential heat flux model (DHFM) based on the open-source computational fluid dynamics platform OpenFOAM. The turbulent heat flux model is also tested with geometrical model of a pipe flow, the square and triangular bundle flow. It is shown that the calculation of Nusselt number Nu for liquid LBE by the second-order differential heat flux model (DHFM) is larger than the correlations in the square and triangular bundle flow. While the calculated Nu for liquid sodium is smaller than the correlations in the square and triangular bundle flow. Among them, the calculated results of liquid LBE and sodium in the pipe flow are in good agreement with the experimental data and the correlations. The DHFM model has a larger error in the square and triangular bundle channels for liquid LBE and sodium. In addition, the non-dimensional temperature, temperature fluctuation and dissipation characteristics of different geometrical models are also investigated in this research. This research can serve as a reference for the numerical calculation of turbulent heat transfer in liquid metals. It also enriches the study of thermal-hydraulics in liquid metal reactors.