Radiation and Chemical Reaction Effects on Unsteady Mhd Free Convection Flow past a Semi-infinite Porous Moving Plate with Heat Absorption

The objective of the present chapter is to analyze the radiation and mass transfer effects on an unsteady two-dimensional laminar mixed convective boundary layer flow of a viscous, incompressible, electrically conducting chemically reacting fluid, along a vertical moving semi-infinite permeable plate with suction, embedded in a uniform porous medium, in the presence of transverse magnetic field. The equations of continuity, linear momentum, energy and diffusion, which govern the flow field, are solved by using a regular perturbation method. The behavior of the velocity, temperature, concentration, skin-friction, Nusselt number and Sherwood number has been discussed for variations in the governing parameters. INTRODUCTION Combined heat and mass transfer (or double-diffusion) in fluid-saturated porous media finds applications in a variety of engineering processes such as heat exchanger devices, petroleum reservoirs, chemical catalytic reactors and processes, geothermal, geophysical engineering such as moisture migration in fibrous insulation, nuclear waste disposal and others. Double diffusive flow is driven by buoyancy due to temperature and concentration gradients. Minkowycz [1] presented similarity solutions for free thermal convection from a plate in a fluid-saturated porous medium. Bejan and Khair [2] investigated the vertical free convection boundary layer flow in porous media owing to combined heat and mass transfer. Lai and Kulacki [3] used the series expansion method to investigate coupled heat and mass transfer in natural convection from a sphere in a porous medium. The suction and blowing effects on free convection coupled heat and mass transfer over a vertical plate in saturated porous medium was studied by Raptis et al. [4] and Lai and Kulacki [3], respectively. There has been a renewed interest in studying magnetohydrodynamic (MHD) flow and heat transfer in porous and non-porous media due to the effect of magnetic fields on the boundary layer flow control and on the performance of many systems using electrically conducting fluids. In addition, this type of flow finds applications in many engineering problems such as MHD generators, plasma studies, nuclear reactors, and geothermal energy extractions. Raptis et al. [4] analyzed hydromagnetic free convection flow through a porous medium between two