Key words: Numerical method, cavity, porous medium, heat and mass transfer, entropy generation, double diffusive convection.

Abstract: Entropy generation in double diffusive convection through a rectangular porous cavity saturated by a binary perfect gas mixture is numerically studied using Darcy – Brinkman formulation. The set of equation describing the phenomenon is solved by using a modified version of the Control Volume Finite-Element Method. Effect of the enclosure geometry on entropy generation was investigated. The results are numerically presented through graphs and maps to observe the effects of aspect ratio of the cavity on entropy generation for the two cases of opposite and cooperatives buoyancy forces.

Key words: natural convection, heat source, Rayleigh number, heat transfer, boundary conditions.

Abstract: The present work deals with the prediction of a natural convection flow in a square cavity, partially heated by an obstacle placed at the bottom wall. The two transverse walls and the top wall of the cavity are supposed to be cold. The main parameter of numerical investigations is the Rayleigh number (engine convection) ranging from 103 to 105. Different configurations relative to cooling obstacle are presented and analyzed in the current study. The simulations were conducted using a numerical approach based on the finite volume method and the projection method, which are implemented in a computer code in order to solve the Navier-Stokes equations.

Abstract: The heat transfer by convection is so far a basic principle in many industrial applications. This study led to the analysis of turbulent convection. Ra> 10⁹ in a three-dimensional parallelepiped cavity filled with air, the two opposite vertical walls are differentially heated at a constant temperature, the other walls are hot wall except ceiling. The finite volume method has been used to discredited the equations of flow in turbulent convection turbulence model used is (κ-ε). The results are relevant because they show that for a number of Pr = 0.71 the Rayleigh number, thus generating a great influence on heat transfer within the study area, and the onset of instability due to the interaction of turbulent structures with the boundary layer.

Key words: Natural convection, finite volume, parallelepiped.

Key words: inverse problem, Levenberg-Marquardt, optical thickness, sensitivity analysis.

Abstract: An inverse radiation problem was considered to estimate the optical thickness for a one-dimensional cylindrical model of a semi-transparent, gray and isotropically scattering medium. The radiative transfer equation is solved using the finite volume method and the temperature is determined according to the dimension of the semi-transparent medium. In order to find the points which give us more information about the optical thickness using the measured temperatures, we carried out a sensitivity analysis. The solution of the inverse problem is obtained with the Levenberg-Marquardt method. The identification results were analyzed with respect to the number of measurements and the initial estimate of the unknown radiative property. The effect of the parameter of the LM method on the stability of the solution, in particular in the vicinity of the initial estimate, was also investigated.

Keywords: Mixed convection, Richardson number, lid-driven cavity, temperature gradients.

Abstract: In this study, the mixed convective heat transfer in a lid driven cubic cavity at is investigated numerically. Two cases are negotiated, the top moving lid and the bottom walls are at constant uniform temperatures (case 1: Ttop > Tb, case 2: Ttop < Tb) while the vertical walls are thermally insulated. The Reynolds number is fixed at Re=100, while the Richardson number is varied from 0.001 to 10. The effect of temperature gradient orientation on the fluid flow and heat transfer has been performed. It is shown that the downward temperature gradient yields a better heat transfer rate than the upward temperature gradients (case 1). Multiple correlations in terms of the heat transfer rate and Richardson number has been established.