This paper reports a numerical study of double-diffusive natural convection through an annular space delimited by a square cylinder on the outside and a cylindrical cylinder on the inside covered by a porous layer. The Darcy-Brinkmann-Forchheimer is used for modeling flow in both fluid and porous areas. The annular space is partially or completely filled with an isotropic porous medium. A finite volume method, using the Patankar-Spalding technique is used for solving the discretization of the dimensionless equations governing the problem. The effects of simultaneously applied thermal and solutal buoyancy forces on heat and mass transfer are shown in the results for a large range of buoyancy ratios N, Rayleigh number, and thermal conductivity. Streamlines, isotherms, and iso-concentrations are presented to analyze the flow structure transition from mass species dominated to thermal dominated flow. Results show that the buoyancy ratio can change the flow pattern and the increased thermal conductivity ratio can improve heat and mass transfer. A good agreement was obtained between the present results and those published were found.

This study aims to analyze mixed convection in a square cavity with two moving vertical walls by finite volume method. The cavity filled with Non-Newtonian fluid of Bingham model is heated from below and cooled by the other walls. This study has been conducted for certain parameters of Reynolds number (Re=1-100), Richardson number (Ri=1-20), Prandtl number (Pr=1-500), and Bingham number has been studied from 0 to 10. The results indicate that the increase in yield stress drops the heat transfer and the flow become flatter, while increasing Reynolds number augments it. The convective transport is dominant when increasing Richardson number which leads to enhance heat transfer in the cavity for both Newtonian and Non-Newtonian fluid. A correlation of Nusselt number is given in function of different parameters.

Two-dimensional steady mixed convection flow in an enclosure with partitions filled with a Bingham fluid is considered. The vertical walls are maintained at different constant temperatures and they are moving in opposite direction. The upper and the bottom walls are fixed and thermally insulated. The governing equations are normalized and solved numerically by the finite volume control. A parametric investigation is performed and a set of isotherms and streamlines are presented. The results shown that the decrease of Richardson number increase the fluid flow and enhanced the heat transfer. The effect of the yield-stress in the presence of the partition is to drop the fluid motion and to augment heat transfer where the conduction mode is dominant.

This study aims to analyze the oxidation of carbon monoxide in moist air from the second thermodynamic law aspect. A mathematical model of laminar premixed ame in a stagnation point ow has been achieved by numerical solution of the boundary layer equation using a self-made code. The chemical kinetic mechanism for ameless combustion of fuel, which is a mixture of carbon monoxide, oxygen, and water vapor, is modeled by 34 elementary reactions that incorporate (09) nine chemical species: CO, O, CO 2 , O 2 , H 2 O, H, H 2 , HO 2 , and OH. The salient point is that for all the parameters we considered, the exergy of the process is completely destroyed by irreversibilities. From the chemical viewpoint, the OH radical plays an essential role in CO oxidation. This latter point has already been mentioned by previous investigators.