Effect of Variable Viscosity on Convective Heat and Mass Transfer by Natural Convection from Horizontal Surface in Porous Medium

The aim of this paper is to investigate the effect of variable viscosity on free convective heat and mass transfer from a horizontal plate embedded in a saturated porous medium. The governing equations of continuity, momentum, energy and concentration are transformed into non linear ordinary differential equations using similarity transformations and then solved by using Runge – Kutta – Gill method along with shooting technique. Governing parameters for the problem under study are the variable viscosity (θc), the buoyancy ratio (N) and the Lewis number (Le). The velocity, temperature and concentration distributions are presented and discussed. The Nusselt and Sherwood number is also derived. The numerical values of local Nusselt and local Sherwood numbers have also been computed for a wide range of governing parameters θc, N and Le. The viscous and thermal boundary layer thicknesses are discussed. Key-Words: Free convection, Heat transfer, Mass transfer, Variable viscosity, Porous medium.