Numerical results are presented for the transient and steady-state velocity field and the temperature field. These results were obtained by solving the partial differential equations describing the conservation of mass, momentum and energy by an explicit finite-difference method in time dependent form. It has been observed that the velocity componentsu, v (absolute) and the temperature0 have larger values in the presence of heat sources than in their absence. Opposite is the phenomenon in the presence of heat sinks. A worthwhile result obtained from the detailed examination of the problem is that the presence of heat sources delays the attainment of steady-state condition.