Numerical simulation on the influence of surface convection on the laminar air flow induced by natural convection in vertical parallel plates is explained. This simulation discussed symmetrically and asymmetrically for uniform heated flux (UHF) and uniform wall temperature (UWT) cases. The effects of variable fluid parameters taken into account for incompressible Navier-Stokes equations. The thermophysical properties variation are determined from air temperature at the inlet of channel. Distribution of several parameters in different sections considered and visited for natural convection. Many tests in various conditions have been undertaken for incompressible Navier-Stokes equations to allow evaluating average Nusselt numbers and air mass flow rate in this thesis. It has found out narrow vertical channels with different aspect ratios exhibit different heat transfer behaviours. Influence of mesh refinement on physical characteristic behaviour has been investigated. Several specific numerical codes, based on stabilized finite element method (FEM) used to solve the incompressible Navier-Stokes equations within the air gap region. These specific codes are suitable to determine the accuracy of heat transfer behaviours in different areas.