Effect of thermal radiation on the laminar free convective boundary layer is studied analytically. The problem of simultaneous conduction, convection and radiation in the laminar boundary layer along a vertical plate is formulated and solved. Finite difference solutions to the governing set of boundary layer equations for the conservation of mass, momentum and energy are presented. Numerical calculations of velocity and temperature profiles are performed for a constant heat flux boundary condition in $CO_2$ and are compared to some experimental data of the others. Results are thus obtained and includes effects of absorption coefficients, plate-emissivities, and heat fluxes. It is inferred that the velocity and thermal boundary layer are attenuated and expanded by gas radiation phenomena.
