Effect of radiatlon and viscous dissipation on convection flow in a vertical porous channel

The effect of radiation on a combined free and forced convection flow of a Boussinesq fluid through a vertical porous channel with viscous and Darcy dissipation is investigated analytically. The temperature of the walls is assumed to be equal and vary linearly with the height of the wall. Closed form solutions are obtained using a perturbation method valid for smalI values of the Eckert number. The effects of radiation, the porous parameter and Prandtl number on the velocity, temperature, flow rate and rate of heat transfer are presented graphically.