Heat and mass transfer by natural convection in a bi-layered cubic enclosure with opposing temperature and concentration gradients

The present study reports a numerical investigation of double-diffusive natural convective heat and mass transfer with three-dimensional flows, in a bi-layered cubic enclosure. The right and left vertical walls are subjected to uniform different temperatures and concentrations while the other walls are assumed adiabatic and impermeable. The Prandtl number Pr is kept at 7 characterizing the case of aqueous solutions as a fluid saturating the two porous layers. The main parameters governing the problem are the Rayleigh number varying from 10(4) to 10(6), the buoyancy ratio for opposing flows (N < 0) from -4 to -0.5, Lewis number form (Le) from 1 to 100, the Darcy number from 10(-8) to 1, the thermal conductivity and the mass diffusivity ratios (lambda(r) and D-r) respectively from 0.01 to 10(3). The nonlinear coupled dimensionless governing equations are resolved using the control volume method. The results of this study are presented in terms of streamlines, isotherms, isoconcentration lines, the average Nusselt and Sherwood numbers and for the velocity, the concentration and the temperature profiles.