Numerical investigation on natural convection of Al2O3/water nanofluid with variable properties in an annular enclosure under magnetic field

Numerical investigation of the natural convection Al2O3-water nanofluid is carried out in a differentially heated vertical annulus under uniform magnetic field. An in-house Fortran code has been developed to solve system equations governing magneto-hydrodynamic flow. Computations are for different Rayleigh numbers (104 ? Ra 106), nanoparticle diameter (dp = 13 and 47 nm), volume fraction (0 ? 0.09), radius ratio (2 ? 10), Hartmann Ha 100). According simulation data, size crucial evaluating properties, such as viscosity thermal conductivity. The computational results reveal that, nanoparticles with dp nm, average Nusselt number Nu¯i on inner cylinder wall decreases increases. This decrease observed up 0.05, after which it increases again. For full range volumetric fractions, shown that increasing causes increase, while field decrease. Furthermore, increases, heat transfer enhancement En mainly when oriented radially. Finally, new correlations versus Ra, ?, Ha, derived axial radial fields cases.