Hydrothermal impact of multiwall carbon nanotube diameter in a conventional square cavity

Abstract

This study aimed to computationally examine the effect of the average diameter of multiwall carbon nanotubes (MWCNTs) on the hydrothermal properties of a square cavity. A conventional square cavity filled with MWCNT–water was used for the experiment. The left and right walls of the cavity are maintained as hot and cold respectively, whereas the top and bottom walls were assumed to be adiabatic. Mathematical models were developed using the Navier–Stokes equations by applying the thermophysical properties of the MWCNT–water nanofluid. A newly proposed correlation between the effective thermal conductivity and the diameter of carbon nanotube was utilized to analyze the impact of the average diameter on the natural convection of nanofluid inside the cavity. The governing equations were non-dimensionalized using suitable variables and then solved using the Galerkin finite element technique. The combined effects of the Rayleigh number (103<Ra<106) and the average diameter of the MWCNTs (10 nm to 30 nm) on the streamlines, isolines, velocity, local Nusselt number, and mean Nusselt number were examined in detail. It is found that the flow and heat transfer rate inside the cavity can be effectively controlled by increasing the average diameter of MWCNTs at higher Rayleigh numbers compared to lower Rayleigh number. A larger MWCNT diameter dominated the impact of the buoyancy force inside the square cavity.

Keywords

• Convective heat transfer
• Finite element method
• Multi-wall carbon nanotubes
• Nanofluid
• Square cavity