variavel0=Mauricio Araujo Zanardi - mzanardi@feg.unesp.br UNESP - Campus de Guaratinguetá Newton Galvão de Campos Leite - nleite@uerj.br UERJ - Campus Regional de Resende Abstract. A theoretical model for a two-phase thermosyphon is presented. The mass, momentum and energy conservation equations are used to describe the internal flow and heat transfer mechanisms in a vertical thermosyphon. The developed model was tested using experimental results available in the open literature. In this work we present the results for the simulation of some thermosyphons built to operate at bakery ovens. The comparison between the numerical and experimental results shows the consistence of the model. Keywords. two-phase thermosyphons, mathematical modeling.