FREE-CONVECTION DRIVEN BY AN EXOTHERMIC REACTION ON A VERTICAL SURFACE EMBEDDED IN POROUS-MEDIA

The free-convection boundary-layer flow on a vertical surface embedded in a porous media driven by an exothermic catalytic chemical reaction on the surface is considered. The governing equations of this how are reduced to a pair of coupled, parabolic partial differential equation s for the temperature and the concentration of the fluid reactant. The se equations are governed by the,dimensionless chemical parameters lam bda and epsilon, which are measures of the reactant consumption and th e activation energy, respectively, as well as the Lewis number. Simila rity solutions are obtained which are valid near the leading edge of t he surface. Asymptotic solutions, which are valid at large distances d ownstream from the leading edge, are obtained for the two independent situations when lambda = 0 and lambda not equal 0. A numerical solutio n to the partial differential equations is then obtained. The numerica l solution is investigated for a range of the chemical parameters lamb da and epsilon, and was found to exhibit localized rapid increases in temperature when lambda and epsilon are small. Comparisons between the numerical solution and the similarity and asymptotic solutions are ma de and are found to be in good agreement. (C) 1997 Elsevier Science Lt d.