Regular Article

Effects of magnetic field on natural convection heat transfer in a T-shaped cavity

¹ Laboratoire de Mécanique, Matériaux et Energétique (L2ME), Faculté de Technologie, Université A. Mira de Bejaia, 06000 Bejaia, Algeria
² Laboratoire de Mécanique des Fluides Théorique et Appliquée (LMFTA), Faculté de Physique, Université des Sciences et de la Technologie Houari Boumediene (USTHB), 16111 Alger, Algeria
³ Service Transferts, Interfaces et Procédés (TIPs), Faculté des Sciences Appliquées/Ecole Polytechnique, Université Libre de Bruxelles (ULB), CP165/67, avenue F.D. Roosevelt 50, 1050 Bruxelles, Belgium

^* e-mail: sahi.adel@hotmail.fr

Received: 11 April 2014
Accepted: 20 February 2017

Abstract

This study was conducted to investigate the magnetic-field effect on the two-dimensional buoyancy-driven natural convection inside a grooved rectangular enclosure subjected to isothermal boundary conditions. The magnetohydrodynamic (MHD) equations, under Boussinesq approximation, are numerically solved using the finite volume method. Numerical simulations have been performed to investigate the free convective heat transfer induced by a temperature difference between the bottom hot wall and the upper cold flat wall. The numerical results, for wide range of Hartmann and Rayleigh numbers and for both horizontal and vertical magnetic field directions, are discussed in terms of velocity, temperature field, streamlines, isotherms, Nusselt numbers and reduction heat transfer ratio. The results highlighted the enclosure's performance condition and revealed that the heat and fluid flow fields are affected by the Rayleigh number and the magnetic field strength and direction. It is observed that increasing the Hartmann number damps the fluid flow, reduces the convection currents, decreases the average Nusselt number at the cold surface and has tendency to delay the transition to convection regime and lengthening the conduction zone. However, the use of magnetic field reduces heat exchange up to 30% with an optimal Rayleigh (Ra_opt) for each Hartmann number.