A numerical simulation is performed for heat transfer enhancement in a parallel-plate heat exchanger equipped with multiple metal foam blocks of various size. Localized heat sources are placed on the top wall of the exchanger in the location of the metallic foam blocks. The Brinkman-Forchheimer-extended Darcy model is used to characterize the flow field inside the foam region. Solution of the coupled governing equations for the composite fluid/ foam system is obtained using the finite volume method. In this study, the influence of the parameters such as the Darcy number, the Reynolds number and the arrangement of the foam samples on the hydrodynamic and thermal behavior of the flow are deeply analyzed. The results are reported for two different configurations containing four metal foam blocks mounted alternately on the top and bottom of the channel walls: (1) blocks are attached straightly to the channel walls and (2) blocks positioned at a precise distance from the channel walls . The obtained results show that the improvement of the cooling of the heat sources by forced convection is better in configuration (2).