ReviewAnalysis of natural convection and entropy generation in a cavity filled with multi-layers of porous medium and nanofluid with a heat generation

- I studied numerically the heat transfer, fluid flow and entropy generation through the multilayers' cavity.
- The absolute value of the maximum streamfunction increases as the thickness of the porous media layer decreases.
- The average Nusselt number decreases as Darcy number increases.
- The maximum value of the heatfunction reduces as the thickness of the porous media layer increases.

A numerical analysis is performed to study the fluid flow, heat transfer and entropy generation inside a cavity with an internal heat generation. The cavity is filled with two layers of nanofluid (TiO2-water) and one center layer of saturated porous media filled with the same nanofluid. The uniform constant heat flux is applied partly at the left vertical wall. Finite element method based on the variational formulation is employed to solve the main equations. Comparisons with previously published works are performed and the results are found to be in a good agreement. In this study, the effect of the main pertinent parameters, such as: Rayleigh number (104 ⩽ Ra ⩽ 107), nanoparticles volume fraction (0 ⩽ Φ ⩽ 0.1), Darcy number (10−1 ⩽ Da ⩽ 10−5), heat generation constant (0 ⩽ λ ⩽ 20), and porous layer thickness (Lpm) on the fluid flow, heat transfer and entropy generation are investigated. Two different cases depending upon the location of the heat source are studied. The results indicate the heat transfer for the case-2 is better than for the case-1. The ratio of the average Nusselt number for the case-2 to the case-1 increases as the Lpm increases (the ratio is 1.365, 1.385 and 1.387 for Lpm = 0.2, 0.333 and 0.466 respectively at Ra = 106, Φ = 0.05, Da = 10−3 and λ = 10).