Numerical investigations of the development and suppression of the natural convection flow and heat transfer in the presence of electromagnetic force

摘要

In this article, a set of parametric studies is performed to establish the optimum configuration of magnetic field strength and its orientation for enhancement in the convection heat transfer. The present numerical analysis reveals the significance of magnetic field and its orientation on the natural convection flow and heat transfer in the 3D cavity at a fixed Rayleigh number (Ra) of 10~6 and Prandtl number (Pr) of 0.025. The governing partial differential equations consist of continuity, momentum and energy equations coupled along with the Maxwell's electrodynamics equations using OpenFOAM. The unsteady flow in the transitional zone is regulated and suppressed back to the steady-state region by the presence of the magnetic field imposed in x- (B_x), y- (B_y) and z-direction (B_z). The magnetic field strength is varied by changing the Hartmann number (Ha) in the range of 0 - 200. It is observed that the B_z magnetic field suppressed the undulation in the flow without suppressing the convection current in the enclosure compared to B_x and B_y magnetic fields, hence, regulating the convection heat transfer. The strength and orientation of the Lorentz force govern the suppression or regulation of flow patterns in the enclosure. The pertinent quantities such as time-averaged Nusselt number (Nu_(avg)) over the hot surface, streamline variations, electric potential distributions, electric current variations, Lorentz force contours, velocity variations (U_x and U_y), and temperature isosurfaces are discussed in detail.