This paper presents an experimental and numerical study of heat and mass transfer in a porous channel crossed by a gravity driven or forced fluid flow. We measured mass flux and local and overall heat transfer coefficients. In the gravity driven case, a maximal mass flux is observed, for which a maximal heat flux is measured. We propose an analytical model based on the Forchheimer law to determine this mass flux. Pore scale numerical simulations were used to provide local quantities and provide complementary interpretation of experimental data. Finally, we have shown that only a part of the foam is efficient for heat transfer and we have determined a foam active length. We propose an analytical model to evaluate this active length.