Nanofluid based natural convection in a three-dimensional horizontal annulus with a porous perturbation

Abstract

In this work, the flow dynamics and heat transfer characteristics are analyzed in nanofluid based natural convection in the presence of a porous perturbation. The results indicate that the effect of the porous perturbation on the flow strength and heat transfer is significant when the thermal conductivity is two orders of magnitude greater than the pure fluid. The flow strength is enhanced with an increase in the thermal conductivity. A peak of local Nusselt is found at the center, where two opposite center rolls appear with the presence of the porous perturbation. The peak is higher and the average Nusselt number increases with an increase in the thermal conductivity. On the contrary, a concave characteristic of the local Nusselt number is seen for very small thermal conductivity as the flow is obstructed by the porous perturbation. Flow strength and heat transfer rate are abated with an increase in the nanoparticle concentration. Based on the numerical results, the dependence of the average Nusselt number on the thermal conductivity ratio and the nanoparticle concentration is obtained.