ENHANCEMENT OF DUPUIT-DARCY THERMAL CONVECTION OF SWCNT-WATER NON-NEWTONIAN NANOFLUID SATURATED POROUS MEDIUM

Abstract

The focus of this manuscript is to investigate numerically the free convection of a single-wall carbon nanotube-water non-Newtonian nanofluid saturating an inclined square porous medium, where the Dupuit-Darcy model is used for modeling the fluid flow inside the cavity along with the Carreau-Yasuda model for describing the apparent viscosity of the nanofluid. The top and bottom walls of the enclosure are kept adiabatic, whereas the others are differentially heated. The governing parameters for the problem are the Rayleigh number, nanotubes volume fraction, inertial effect parameter, the Carreau-Yasuda non-Newtonian parameters as well as the inclination angle of the cavity. The finite difference method is used to resolve the governing partial differential equations of the problem. The obtained results are presented through graphs, streamlines, isotherms, and apparent viscosity contours. In addition, a scale analysis is presented to show the maximum heat transfer enhancement recorded. As a matter of fact, the obtained momentum equation enables the analysis of the Newtonian and non-Newtonian behavior of the nanofluid along with the Darcy and the departure from Darcy situation. The findings show that the increase of the single-wall carbone nanotube (SWCNT) percentage significantly enhances the heat transfer even with the increase of the fluid viscosity. Furthermore, the increase of inertial effect parameter inhibits the flow inside the cavity and causes a decrease in the convection rate. In actual fact the power-law index parameter of the Carreau-Yasuda model has a significant effect on the fluid flow strength as well as the convection rate inside the enclosure, i.e., the more the shear thinning the fluid, the better is the rate of convection. The inclination angle of -30° presents better angle for maximum convection rate. An enhancement of 8% in convection rate is recorded for the case of the Newtonian behavior, while for the shear-thinning situation the enhancement reaches eight times of that recorded of Newtonian condition.