Simulation of Forced and Mixed Convection Heat Transfer in Vertical Pipes

Forced and mixed convection-generated velocity and temperature fields in vertical pipes containing liquid metals and water were numerically predicted with a computational fluid dynamics model based on a finite volume method. The constant heat flux is imposed as a boundary condition at walls. The developed model considers the variable properties of liquid metals. The range of considered Reynolds and modified Grashof numbers is 10,000 < Re < 50,000 and 108 < Gr* < 4 * 108. The ascending and descending flows with moderate and high buoyancy were considered. Various sensitivity studies such as mesh sizes, and meshing approaches, considered computational domains, various initial, inlet, and outlet conditions, and effects of axial conduction in walls were performed. The meshing approach was based on hexahedral cells and local mesh refinement near the walls. To evaluate various modeling approaches the similarities and differences between predictions and available experimental results were presented and discussed based on the comparisons of the velocity and temperature profiles and Nusselt number.