Impacts of Amplitude and Local Thermal Non-Equilibrium Design on Natural Convection within NanoflUid Superposed Wavy Porous Layers.

Ammar I Alsabery,Tahar Tayebi,Zehba A S Raizah,Ali J Chamkha,Ali S Abosinnee,Ishak Hashim

doi:10.3390/nano11051277

Abstract

A numerical study is presented for the thermo-free convection inside a cavity with vertical corrugated walls consisting of a solid part of fixed thickness, a part of porous media filled with a nanofluid, and a third part filled with a nanofluid. Alumina nanoparticle water-based nanofluid is used as a working fluid. The cavity’s wavy vertical surfaces are subjected to various temperature values, hot to the left and cold to the right. In order to generate a free-convective flow, the horizontal walls are kept adiabatic. For the porous medium, the Local Thermal Non-Equilibrium (LTNE) model is used. The method of solving the problem’s governing equations is the Galerkin weighted residual finite elements method. The results report the impact of the active parameters on the thermo-free convective flow and heat transfer features. The obtained results show that the high Darcy number and the porous media’s low modified thermal conductivity ratio have important roles for the local thermal non-equilibrium effects. The heat transfer rates through the nanofluid and solid phases are found to be better for high values of the undulation amplitude, the Darcy number, and the volume fraction of the nanofluid, while a limit in the increase of heat transfer rate through the solid phase with the modified thermal ratio is found, particularly for high values of porosity. Furthermore, as the porosity rises, the nanofluid and solid phases’ heat transfer rates decline for low Darcy numbers and increase for high Darcy numbers.

Highlights

For a low Darcy number, the isotherms are virtually vertical in the porous layer and correspond to the solid phase isotherms, indicating that the heat transfer occurs essentially by the conduction mode because the porous medium becomes less permeable
By comparing the isothermal lines in the solid part and the nanofluid phase in the porous layer, it is clear that, when the heat transport mode is mainly governed by conduction at low Darcy number values, the Local Thermal-Equilibrium (LTE) state is feasible because the isotherms are conformal
To frame the effect of the porous medium permeability, we present in Figure 6 the numerical results given by the profiles of the local velocity with the vertical line at X = 0.5 (a), the local Nusselt number of the nanofluid phase (b), and the local Nusselt number of the solid phase (c) for different Da for the case of φ = 0.02, γ = 10, A = 0.1, and ε = 0.5

Summary

Introduction

Natural convection heat transfer in an enclosure, which is divided into two regions, one filled with a porous medium and the other with a fluid, was analyzed by Tong and Subramanian [3], for the aim of developing the characteristics of heat transfer for enclosures containing different quantities of porous material. Both studies of Poulikakos et al [4] and Poulikakos [5] relied on measuring the flow of fluid floating on a porous bed heated from below at Rayleigh numbers above a critical value. The authors in Beckermann et al [6]

Methods

Results

Conclusion