The heat and mass transfer of natural convection was a subject of many theoretical, numerical and experimental studies that have dealt with heat and mass transfer confined into different vertical and horizontal annular enclosures. The study of heat and mass transfer in annular spaces is of fundamental importance because it's often met in many practical applications. These annular spaces have different geometries and can be partly or completely filled with porous media. Interest in the phenomena of heat and mass transfer by natural convection is due to many potential applications in the engineering processes which involve the chemical, oil and gas industries, thermal recovery process, the underground spreading of chemical waste and other pollutants, evaporation, cooling and solidification are few other application areas where combined thermosolutal convection in porous media can be observed.

The present work formulate a two-dimensional heat and mass transfer by natural convection in an annular cylindrical space filled with fluid-saturated porous medium which is analyzed by solving numerically the mass balance, momentum, energy and concentration equations, using Darcy's law and Boussinesq approximation. Both walls delimiting the annular space are maintained at two uniform different temperatures and concentrations. The external parameter considered is Rayleigh-Darcy number, Lewis number and the buoyancy ratio. The heat and mass transfer by natural convection is studied for the case of aiding equal buoyancies, where the flow is generated in a cooperative mode by both temperature and solutal gradients. The local Nusselt and Sherwood numbers are presented in term of the external parameters.