Influence of magnetic field on natural convection and entropy generation in Cu-water nanofluid-filled cavity with wavy surfaces

This paper investigates the influence of a magnetic field on the natural convection heat transfer and entropy generation of Cu-water nanofluid in a cavity with complex-wavy surfaces. The study examines the effects of the Hartmann number, Rayleigh number, Eckert number, nanoparticle volume fraction, and wavy-wall geometry parameters on the Nusselt number, entropy generation and Bejan number. The results show that at higher values of the Rayleigh number, the mean Nusselt number decreases and the total entropy generation increases as the Hartmann number is increased. However, for low Rayleigh numbers, the Hartmann number has a minor effect on the mean Nusselt number and total entropy generation. In addition, an optimal heat transfer effect and a minimal total entropy generation can be obtained when an appropriate wavelength of the wavy surface is applied to the cavity. Furthermore, the mean Nusselt number decreases and total entropy generation increases with an increasing wave amplitude of the wavy surface when a high Rayleigh number is given. Finally, the Bejan number decreases with an increasing Eckert number, but increases with an increasing Hartmann number.