Abstract: In order to precisely predict the heat transfer characteristics of the upper head of steal containment of small modular reactor under accidents, a natural convection device with bottom curved heating surface in a rectangular enclosure was designed to study the effect on the fluid temperature derived from thermal conductivity. Based on the OpenFOAM, the numerical simulation method was used to compare and analyze the performance of the existing two kinds of turbulence models and three kinds of turbulent heat flux models, and to select the appropriate numerical model. The result shows that the flow along the curve will be influenced by the boundary layer, and the intensity of natural convection will be decreased firstly and then increased again along the curve surface from upper position to both sides. The effect of conductivity on the temperature distribution of curve surface is larger than that on the fluid temperature distribution beyond the heating section. Through the revised AFM, the parameters were subjected to empirical correction, improvement and re-verification by sensitivity analysis of the model parameters and comparison of experimental data. A turbulence model suitable for natural convective heat transfer with bottom curved heating surface in a rectangular enclosure is obtained.