A theoretical model is presented that describes sweeping gas membrane distillation processes through porous hydrophobic membranes. The approach considers the case in which the liquid feed and the sweeping gas counterflow in a plate and frame membrane module. The model developed emphasises the importance of the heat fluxes in the directions parallel and perpendicular to the membrane surface and permits to obtain the temperature profiles inside the fluid phases. In order to check the model, two membranes have been studied in different experimental conditions. The influence of some relevant parameters, such as the inlet and outlet temperatures or the circulation velocities of the fluids has been studied. The theoretical predictions of the model have been applied to the obtained results and the accordance may be considered good.