Only limited studies are available experimentally to investigate hydrocarbon fuel pyrolysis, which can be of practical interest for the active cooling of head-loaded components in aerospace vehicles such as combustors in rocket engines. The numerical simulation is an additional way to investigate the related phenomena (heat and mass transfer with chemistry). After a first-code validation with experiments based upon inert gases, the code is further extended toward permeation with reactive dodecane and a reasonable agreement is found. The experimental accuracy of the permeability's' determination is confirmed numerically to be within 30%. Numerically it is shown that this accuracy is due to strong flow spatial heterogeneities. The border effect of the test cell is found to be related to the permeable medium thickness, whereas the temperature field is correlated to the reaction zone. Two different kinetic mechanisms are used to investigate the chemistry effect on the heat and mass transfer. They also provide a better analysis of the fuel pyrolysis and of the products' formation.