A numerical study of forced convection enhancement in a channel intermittently heated is presented in this work. The use of porous blocks mounted on the heated parts of the channel to improve thermal performance is investigated. In order to account for the inertia, drag and boundary effects, the Brinkman-Forchheimer-extended Darcy model is adopted for the flow inside the porous regions. The effects of several parameters such as Darcy number, the block dimensions, the number of blocks and the thermal conductivity ratio are documented. The results show that the blocks may alter substantially the flow pattern depending on the permeability of the porous medium, and may improve the heat transfer and reduce the wall temperature under certain circumstances.