Unsteady Mixed Convection in a Vented Enclosure Partially Filled with Two Non-Darcian Porous Layers

Abstract

Mixed convection in a ventilated rectangular cavity with a horizontal strip occupied by two media of different permeability is studied by using the finite-volume method. The effect of the parameters that govern the problem, the Reynolds number (200–500), the Richardson number (0.1–10), the Darcy number (1.E–6–1.E–2), permeability ratio (0.01–100), aspect ratio of the cavity (1–1.5), and direction of flow with or against gravity, is investigated. From the numerical results, the influence of Darcy and Reynolds numbers on the fluid mechanics can be inferred. When the cold fluid flow is descending, the fluid–porous medium heat transfer increases because the hotter fluid is located in the upper zones of the cavity. As the aspect ratio (height/width) increases from 0.67 to 1.5, both the Nusselt number (7.5 < Nu < 27) and the friction coefficient increase. The friction coefficient on the walls is greater when Re = 500 and Ri = 10 in the two directions of flow. As the Darcy number increases, the velocity gradients increase near the walls, causing an increase of the friction coefficient (0 < Cf Re < 47).

The authors acknowledge CONICYT-Chile for support received in the FONDECYT 1070186 project and to DICYT-USACH-Chile in the DICYT 010633SM project.