Abstract

In this study, comprehensive study of laminar flow and heat transfer of pseudo-plastic non-Newtonian nanofluid (Al2O3 + CMC) within the porous circular concentric region is presented. The effect of volume fraction of nanoparticles, Reynolds number, Darcy number, thickness ratio is studied. Simulations for different Reynolds numbers and Darcy numbers in the range of 100 ≤ Re ≤ ۳۰۰ and 10− ۴ ≤ Da ≤ ۱۰− ۲ are done. The results show that the effect of the porous layer on increasing the convective heat transfer coefficient is larger than the Reynolds number, since, at a given volume fraction, the porous medium plays a greater role in increasing the heat transfer compared to the increasing Reynolds number. Also, at a given volume fraction and for a fixed porosity, decreases in the permeability leads to increased Darcy velocity and, consequently, velocity profile. As the thickness of the porous layer increases at fixed values of permeability and porosity, the velocity of the nanofluid is also increased in a constant Reynolds number, by increasing the thickness of the porous media, heat transfer coefficient increases. In addition, at a specified thickness and constant Reynolds number, by increasing the Darcy number, the heat transfer coefficient and the Nusselt number increases. Moreover, as the thickness of the porous layer increases at fixed values of permeability and porosity, the velocity of the nanofluid is also increased; this consequently maximizes the pressure drop.

Introduction

A non-Newtonian fluid is a fluid that does not follow Newton’s law of viscosity. Shear thinning is the non-Newtonian behavior of fluids whose viscosity decreases under shear strain [1,2]. In fluid mechanics, fluid flow through porous media is the manner in which fluids behave when flowing through a porous medium. The concept of porous media is used in many areas of applied science and engineering [3]. Nanofluids are fluids containing nanoparticles. They are engineered colloidal suspensions of nanoparticles in a base fluid. They exhibit enhanced thermal conductivity and the convective heat transfer coefficient compared to the base fluid [4–۱۳].