Condensation and evaporation processes from wetted surfaces are of utmost importance in many technological or industrial applications. In many devices such as home-appliances and air conditioning systems just to name a few, condensation and evaporation processes greatly impact their performance and energy efficiency; The physics of these processes is quite complex, involving conjugate heat transfer among solid liquid film-gaseous phase together with the change of phase associated with evaporation and/or condensation. In spite of their own importance in technological applications, most physical aspects of this class of multiphase flows still need to be addressed. So far, many studies have been performed focusing on individual issues of full process, and, to the authors knowledge, their mutual influences was not addressed as yet. The aim of the present study is to supplement this field with a reliable numerical model for evaporation and condensation of thin liquid films in buoyant, conjugated heat transfer systems with vapor transport. The model is presented, validated on a simple case and successively applied to a literature relevant case. Validation is carried out considering a simple, insulated, 2-D geometry consisting of a fluid box connected to a solid. This allows to validate the model in a tightly controlled environment. Successively we reproduce the work of N. Laaroussi, G. Lauriat, G. Desrayaud, Effects of variable density for film evaporation on laminar mixed convection in vertical channel, Int. J. Heat Mass Transfer 52, 2009, 151-164, and we highlight the importance of considering the thermal characteristics of the solid part for the accurate reproduction of the complex physics associated to evaporation/condensation processes. (C) 2013 Elsevier Ltd. All rights reserved.