An improved tank in series reactor model for the tubular solid oxide fuel cell stack is presented. The model accounts for the charge balances in the electrodes and electrolyte in addition to the component and energy balances, and is used to simulate the potentiostatic operation of the stack. Moreover, the time required for simulating this model is much less compared to the more elaborate three-dimensional models in the literature. The results demonstrate a strong coupling between the temperature, concentration and current density distributions.