Computational Fluid Dynamics Simulation of Mixed Convection Heat Transfer to Liquid Metals in a Vertical Pipe

Velocity and temperature fields caused by mixed convection in vertical pipes containing liquid metals were predicted numerically with a computational fluid dynamics model based on a finite volume method. The constant heat flux was imposed as a boundary condition at pipe walls. The developed model considered variable properties of the liquid metals with the Prandtl numbers Pr ∼ 0.0059. The range of considered Reynolds and modified Grashof numbers were 10,000 < Re < 50,000 and 10⁸ < Gr* < 4*10⁸. The ascending and descending flows with moderate and high buoyancy were considered. For some cases, conjugated heat transfer including pipe walls was modeled. Various sensitivity studies such as mesh sizes, meshing approaches, considered computational domains, initial, inlet, and outlet conditions, and axial conduction in pipe walls were performed. The meshing approach was based on hexahedral cells and local mesh refinement near the pipe walls. The modeling approach was evaluated against experimental Nusselt numbers, velocity, and temperature profiles.