Simulation of magnetic field effect on heat transfer enhancement of swirling nanofluid

Abstract

In this paper, the swirling nanofluid flow which is driven by a rotating bottom disk of a cylindrical container under magnetic field effect and temperature gradient is considered. Effects of electrical conductivity of cylindrical walls on heat transfer enhancement are numerically analyzed. The governing equations that describe the combined problem (magnetohydrodynamics and mixed convection) under the adoptive assumptions are solved numerically by the finite volume technique. Calculations were made for fixed Reynolds number (Re[Formula: see text]1000), Richardson number (0[Formula: see text]Ri[Formula: see text]2), aspect ratio ([Formula: see text]), Hartmann number (0[Formula: see text]Ha[Formula: see text]60), and solid nanoparticle (copper) with volume fraction ([Formula: see text]). Five cases are considered in this study: (EI-Walls), (EC-Walls), (EC-Bottom), (EC-Top), and (EC-Sidewall). A decrease in the mean Nusselt number was found with the increase of the Richardson number due to stratification layers. These latter limits the heat transfers between the hot and cold zones of the cylinder. The results indicate that the Nusselt number gets bigger within a certain range of Hartmann numbers, and especially when the rotating lid is electrically conducting. Indeed, average Nusselt number decreases while the Hartmann number increase after it exceeds a critical value. Finally, the electrical conductivity of the rotating lid plays an important role in heat transfer enhancement in nanofluid swirling flow.