This study focuses on a numerical simulation of a steam reforming system. The steam reforming system consisted of a cylindrical steam reformer and a combustion burner. The heat was supplied to an endothermic steam reformer from combustion gases. The correlation between the performance and the shape of the system was studied using two different configurations. The first configuration utilized a flame guide between the combustion burner and the steam reformer, whereas the other did not. The flame guide changed the flow of the combustion gas, which affected the heat transfer rate from the burner to the reformer. Reactor temperature profiles, heat transfer rates, fuel conversions, and hydrogen yields were calculated. In addition, the fuel feed ratio between the burner and the steam reformer was manipulated as an operating parameter.