A. Mokhtare, A. Jafari, E.P. Furlani
University at Buffalo,
Keywords: ferrofluids, porous media, magnetic fluid, heat transfer enhancement
Summary:Unique interactions of ferrofluids with magnetic fields can be exploited to achieve enhanced heat transfer for myriad fluidic based applications. In this study, we use a numerical simulation to investigate the transient behaviour of flow and heat transfer of an Fe3O4 ferrofluid in a partilly filled vertical porous channel in the presense of a gradient magnetic field. Magneric field distibutions, generated by one permanent magnet, is analyzed to demonstrate the influence of the ambient field on heat transfer enhancement. Influences of local inertial effects, viscous heating due to the viscous dissipation, and the magnetic heating source are also taken into account. Equilibrium magnetization for the ferrofluid and variations of the field distrubution in different media are modeled using a nonlinear relationship between the ferrofluid magnetization and the applied field intensity. In this magneto-thermo-mechanical problem, our objective is to promote heat transfer, which is attributable to the unique characteristics of both the ferrofluid and porous medium. The flow is considered laminar and Forchheimer–Brinkman extended Darcy model is used to model flow through the porous region. The ferrofluid is heated as it flows upward in the vertical channel, mainly as it passes throught the porous portion of the channel. Comprehensive studies are carried out on broad range of parameters. It was found that the Nusselt number can be increased due to the presence of the magnetic field. Heat transfer enhancement is accomplished with a reasonable increase in pressure drop. The simulation results indicate that the fully developed Nusselt number at the outlet can be practically doubled. The results of this study can be used by designers to enhance heat transfer and control channel flow for novel heat exchange applications.