A mathematical model of an industrial steam-methane reformer (SMR) is developed for use in monitoring tube-wall temperatures. The model calculates temperature profiles for the outer-tube wall, inner-tube wall, furnace gas and process gas. Inputs are the reformer inlet-stream conditions, the furnace geometry and material properties of the furnace and catalyst-bed. The model divides the reformer into zones of uniform temperature and composition. Radiative-heat transfer on the furnace side is modeled using the Hottel Zone method. Energy and material balances are solved numerically. The effect of important model parameters on reformer temperature profiles is assessed and the parameters are fit to data from an industrial SMR. At plant rates greater than 85% the model accurately predicts the process-gas outlet temperature, composition, pressure, flow rate and tube-wall temperatures. The adjustable parameters may need to be re-estimated using additional low plant rate data. The model has the capacity to be developed into a more complex model that accounts for classes of tubes associated with different radiative environments. (C) 2011 Elsevier B.V. All rights reserved.