The effusion sources modeled in this article are part of a continuous process for production of thin-film photovoltaic modules. Industrial production requires tight control of the vapor flow rates during long run times. A dynamic model is developed to provide physical insight, facilitate simulation studies, and to be incorporated into model-based control schemes. Prediction of the vapor flow rate requires both the mass and energy balance to be solved. Model parameters are estimated based on literature and experimental data, and the entire model is shown to be consistent with independent experimental data. (C) 2005 American Institute of Chemical Engineers.