Abstract: Convective heat transfer in a porous medium with uniform internal heat generation per unit volume q is studied. Evolution of convection with the lapse of time at various Rayleigh numbers is investigated by higher order defference techniques (effect of tilted angle is properly studied for comparison). Convection is computed up to about Ra=16 000 . The results show that the convection is stable at small Ra , and becomes periodic when Ra is increased to 4 600, as Ra is further increased there...