Effects of Inner Core Movement and Rotation on Thermal Fluid Flow in Concentric Annulus
Shuichi Torii and Wem-Jei Yang
A numerical study is performed to investigate heat transfer and fluid flow in the concentric annulus with a stationary insulated outer cylinder, in which a slightly heated rotating inner core moves in the flow direction. Emphasis is placed on the effects of axial rotation and streamwise movement of the inner core on the flow structure and heat transfer performance. A two-equation k-e turbulence model is employed to determine the turbulent viscosity and the turbulent kinetic energy. The turbulent heat flux is expressed by Boussinesq approximation in which the eddy diffusivity for heat is given using the turbulent Prandtl number. An inner core rotation causes amplification of the turbulent kinetic energy over the whole cross section, resulting in a substantial enhancement in the Nusselt number. In contrast, the streamwise movement of the inner core causes substantial reduction in the turbulent kinetic energy intensified by the inner core rotation, resulting in the deterioration of the Nusselt number. Heat transfer performance in Couette flow is found to be affected by both the velocity ratio of the moving inner cylinder to the fluid flow and the inner core rotating speed.