The heat transfer associated with an infinite planar array of distributed heat sources on the bottom wall of a horizontal air filled plenum is modelled numerically, and simulations which account for natural convection and radiation are performed to investigate the effect of independent sinusoidal modulation of heat fluxes. Nusselt number, maximum velocity and Rayleigh number decrease with increasing oscillation amplitude, while the temperature difference between the cold upper wall and the average source temperature decreases. The decrease in temperature difference associated with heat flux modulation indicates an improvement in overall heat transfer. (c) 2006 Elsevier Ltd. All rights reserved.