Numerical analysis of hybrid nanofluid natural convection in a wavy walled porous enclosure: Local thermal non-equilibrium model

Abstract

A numerical study of the Buoyancy-driven flow in a porous enclosure, having a bottom heated wavy wall, filled with Cu-Al2O3/water hybrid nanofluid is performed using the local thermal non-equilibrium model. The non-dimensional governing equations of fluid flow and heat transfer are solved using the Galerkin finite element method. The state variables change in the porous enclosure is represented using the Darcy-Brinkman model. The impacts of various effective parameters which include nanoparticle volume fraction (0 ≤ Φ ≤ 0.04), Darcy number (10−5 ≤ Da ≤ 10−2), modified conductivity ratio (0.1 ≤ γ ≤ 1000), the number of undulations (1≤ N ≤ 5) and the amplitude of waviness (0.05 ≤ A ≤ 2). The results showed that the Darcy number is the first controlling parameter on the fluid flow and temperature distributions followed by A, N and γ. Additionally, the heat transfer rate is increased by increasing the thermal conductivity of the nanoparticles reaching its maximum value at Φ = 0.04. Furthermore, by comparing the temperature fields of the fluid phase and solid matrix, it is clear that the effects of the local thermal non-equilibrium are significant at a low modified thermal conductivity ratio and high Darcy number.