Numerical study of MHD natural heat transfer of non-Newtonian, carbon nanotube-water nanofluid inside an internally finned annulus

In this paper, a numerical analysis of natural convection of a non-Newtonian nanofluid flow in a finned annulus employing a finite element approach is presented. The computational domain is affected by an external magnetic field. This study is carried out for various parameters, including Hartmann number, Rayleigh number, nanoparticles volume fraction, power-law index, Prandtl number, and fin length ratio. Results show that as the Hartmann number increases, the magnetic force opposes the buoyancy force and generally suppresses the convection process. Also, it is shown that the effect of Hartmann number alteration on the equivalent thermal conductivity (K eq ) weakens for smaller Ra numbers. Besides, the influence of the Hartmann number on decreasing the net convective heat transfer drop as the power-law index increases, and augmentation of the power-law index causes K eq to decline. The results reveal that by adding nanoparticles to the base fluid, the enhancement in total heat transfer is more intensified in low Rayleigh numbers with a reduction in the difference between K eq values for various volume fractions as the Hartmann number rises. Furthermore, the effect of the Hartmann number on decreasing the net convective heat transfer increases for lower power-law index values, i.e., variations of the Hartmann number has a stronger influence on K eq for power-law fluids with n 1.