Steam Reforming of Methane, which converts natural gas into products with higher economic value in the presence of a suitable catalyst bed reformer, is the most economical method for hydrogen production in petroleum refineries. This study focuses on developing a Computational Fluid Dynamics (CFD) model of a steam methane reformer. To this purpose, a steady-state heterogeneous 3 Dimensional model that was composed of mass, species, momentum, and energy balances was developed. It compares two different geometrical porous bed reformers with different heating tube configurations for better heat transfer and reforming. Effects of heating tubes inlet temperature, the ratio of inlet CH4/H2O, and the configuration of the heating tube are studied and optimized. The results show that conversion of methane will be promoted by increasing inlet temperature of the heating tube as well as the number of heating tubes in the reformer when CH4/H2O ratio is about 0.2. In this platform, the conversion of methane is not affected by the porosity below 0.35. Also, the simulations results are shown to be in agreement with typical data reported in the literature. So, this study can be used to develop industrial natural gas reformers.