Magnetohydrodynamic buoyancy-driven heat transfer in a cylindrical–triangular annulus filled by Cu–water nanofluid using CVFEM

In this paper, effect of magnetic field on free convection heat transfer in a horizontal cylindrical–triangular annulus filled with Cu–water nanofluid is investigated numerically. The governing equations of fluid flow and heat transfer are derived in terms of stream function–vorticity formulation. The control volume based finite element method (CVFEM) is employed to deal with these equations using a linear triangular grid system. Theoretical models of Maxwell-Garnetts (MG) and Brinkman are used to simulate the presence of nanoparticles in base fluid. The effects of Magnetic field, Rayleigh number, nanoparticles and annulus radius ratio on streamlines, isotherm and heat transfer are investigated. The results indicate that the fluid flow is suppressed by the retarding effect of electromagnetic force and as Hartmann number increases, Nusselt number decreases. It is also found that the average Nusselt number is an increasing function of nanoparticle volume fraction, Rayleigh number and aspect ratio. Furthermore, enhancement in heat transfer caused by nanofluid, increases with increase of Hartmann number while it decreases with augment of Rayleigh number.