Effects of Magnetohydrodynamics on Natural Convection and Entropy Generation with Nanofluids

The paper presents a numerical study of the magnetohydrodynamic natural convection heat transfer of a heated block situated on the bottom wall of an enclosure filled with nanofluids. The transport equations for a Newtonian fluid are solved numerically using the lattice-Boltzmann method. The effective thermal conductivity and viscosity of the nanofluid are calculated by the Koo-Kleinstreuer-Li correlation. The influence of pertinent parameters such as Rayleigh number, solid volume fraction, Hartmann number, magnetic field inclination angle, nanoparticle volume concentration and aspect ratio of the rectangular heated block on the flow, heat transfer characteristics, and entropy generation has been investigated. It is found that the total entropy generation is an increasing function of the Rayleigh number, whereas it is a decreasing function of the Hartmann number. Moreover, the numerical results demonstrate that the average Nusselt number increases steadily but nonlinearly by the augmentation of the nanoparticle volume fraction. Also, the results show that the magnetic field with an inclination angle of gamma = pi/2 has the maximum heat transfer coefficient and total entropy generation.