Effect of Wall Electrical Conductivity on Heat Transfer Enhancement of Swirling Nanofluid-Flow

摘要

Effects of electrical conductivity of cylindrical walls on both heat transfer enhancement in nanofluid swirling flow and fluid layers produced in a cylindrical container are numerically analyzed. A temperature gradient and external magnetic field are imposed in the axial direction on the rotating flow which is moved by the bottom disk. The governing equations that describe the combined problem (MHD and mixed convection) under the adoptive assumptions are solved numerically by the finite volume technique. Calculations were made for fixed Reynolds number (Re = 1000), Richardson number (0 ≤ Ri ≤ 2), aspect ratio (H/R = 2), Hartmann number (0 ≤ Ha ≤ 60), and solid nanoparticle (copper) with volume fraction (Φ = 0.1). 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.