Numerical two-dimensional analysis using finite difference approach with “line method” is performed
on the laminar magneto-hydrodynamic natural convection in a square enclosure filled with a porous
medium to investigate the effects of viscous dissipation and radiation. The enclosure heated from left
vertical sidewall and cooled from an opposing right vertical sidewall. The top and bottom walls of the
enclosure are considered adiabatic. The flow in the square enclosure is subjected to a uniform magnetic
field at various orientation angles (? = 0?, 30?, 45?, 60? and 90?). Numerical computations occur at wide
ranges of Rayleigh number, viscous dissipation parameter, magnetic field orientation angles, Hartmann
number and radiation parameter. Numerical results are presented with the aid of tables and graphical
illustrations. The results of the present work explain that the local and average Nusselt numbers at the
hot and cold sidewalls increase with increasing the radiation parameter. From the other side, the role
of viscous dissipation parameter is to reduce the local and average Nusselt numbers at the hot left wall,
while it improves them at the cold right wall. The results are compared with another published results
and it found to be in a good agreement.