This work concerns the modelling of coupled heat and mass transfer in a reacting porous medium used in a fixed-bed gas/solid reactor. The model takes into account the resistances to mass diffusion through the effective permeability of the reacting bed and the resistances to heat diffusion via two parameters : the effective heat conductivity of reacting medium and the heat transfer coefficient between the solid and the gas. The model equations are solved by the finite elements method. The influence of the solid-gas heat transfer coefficient on the simulation results has been studied. Experimental results are used to validate our model. The proposed model in this study allows one to have exactly the gas flow rate leaving the reactor and correctly describes the behaviour of the gas/solid reactors used in chemical heat pumps domain.