CHEMICAL ENGINEERING TRANSACTIONS VOL. 71, 2018 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Xiantang Zhang, Songrong Qian, Jianmin Xu Copyright © 2018, AIDIC Servizi S.r.l. ISBN 978-88-95608-68-6; ISSN 2283-9216 Numerical Simulation of Magneto Hydrodynamic Natural Convection in a Vertical Cylindrical Crucible Vahid Ahmadpour*, Iraj Mirzaei, Sajad Rezazadeh Urmia University of technology, Mechanical Engineering Department, P.O. Box 57155-419, Urmia, Iran V.ahmadpour@yahoo.com The purpose of this paper is a numerical study to investigate the effects of external horizontal magnetic field on heat transfer characters within a pure molten metal filled a vertical 3D cylindrical crucible. The inner and outer walls of annulus are kept at constant temperature and the upper and lower walls are thermally insulated. The model is based on magneto hydrodynamic natural-convection theory and low Reynolds number approximation. Finite volume approach and fully implicit scheme is adopted to discrete corresponding equations. Results have been conducted for three different geometrical sizes, Rayleigh and Hartman Numbers. The 3D simulation results indicate a strong relation between heat transfer, the magnetic field strength and the aspect ratio of the crucible. In addition, this model shows that the azimuthal distribution of velocity and temperature fields affected greatly in crucible in presence of external magnetic field. The model has been validated availiable results. The findings of this study are expected to be useful for enhancing the design of solidification systems. 1. Introduction Solidification processing has been used extensively in metallic alloys and semiconductors industry for many years. From the view of production, the final product quality is dependent upon many parameters including composition, cooling rate, boundary conditions, body and external forces and the temperature field of the melt region. In fact, these parameters could affect the flow patterns in the melt by producing convection flows. In addition, the nature of these flows is so that plays significant role on melt/solid front morphology and solidified structure. Also, experimental evidences proved that during solidification process such fluid motions in molten metal affect performance of final product. Hence, controlling unwanted convection flows in melt is crucial. In practice, it is possible to overcome these limitations partially by several methods. An interesting solution is applying an external magnetic field to suppress the buoyancy driven flows which referred to Magneto hydrodynamics (MHD) problems in the literature. Whatever we recognize as main figures of MHD theory refers to Hartmann, Alfvén, and other’s experiments in the first half of the twentieth century (Davidson 2001). (Sarris et al., 2010) carried out numerical investigations about the problem of transient and turbulent natural convection of the electrically conductive low-Prandtl number fluid that driven by horizontal temperature gradients in a vertical cylinder in the presence of a vertical magnetic field. An investigation of solidification and melting of gallium in presence of constant magnetic field in a rectangular cavity was performed (Charmchi et.al, 2004). (Sankar et al., 2008) studied the effect of magnetic field on the driven convection in combination of buoyancy and surface tension forces in a cylindrical annular enclosure. (Afrand et al., 2017) investigated a 3D numerical method to analyse the natural convection in a cylindrical annulus containing molten potassium under a magnetic field. An experimental study for free convection in a vertical annulus was presented by Ejaz and Manzoor (2018). Effects of a bottom heated rotating cylinder in a vertical annulus have been experimentally studied with respect to heat transfer parameters. (Vasanthakumari and Pondy, 2018) presented a numerical investigation of steady two dimensional laminar, boundary layer flow of incompressible, viscous nanofluid with MHD along with heat generation and suction effect is considered. (Wang et al., 2017) examined the natural convection heat transfer of Al2O3-water nanofluid in a differentially-heated three-dimensional cubic enclosure. The study focuses on the DOI: 10.3303/CET1871230 Please cite this article as: Ahmadpour V., Mirzaei I., Rezazadeh S., 2018, Numerical simulation of magneto hydrodynamic natural convection in a vertical cylindrical crucible, Chemical Engineering Transactions, 71, 1375-1380 DOI:10.3303/CET1871230 1375