This paper deals with the modeling of the performance, in terms of energy consumptions and distillate flow rate produced, of flat and capillary membrane modules in vacuum membrane distillation (VMD). The developed model was validated by experimental tests carried out at lab-scale on a lab-made flat module of 40 cm(2) membrane area, equipped with a commercial polypropylene membrane (pore size, 0.2 mu m), and on a commercial capillary Microdyn module of 0.1 m(2) membrane area. Once validated, the mathematical model was used to predict the performance of modules with higher membrane areas (up to 5 m(2)). The flat module resulted to perform better than the capillary one in terms of energy consumption/permeate flow rate ratios, the lowest value being 130 kW h/m(distillate)(3), for a 5 m(2) membrane area, at 80 degrees C of feed temperature and 10 mbar of vacuum pressure. (c) 2013 Elsevier B.V. All rights reserved