A comprehensive numerical investigation on membrane distillation of methanol and water in a microseparator was carried out. The focus was to investigate the impact of the apparatus geometry on the separation performance and to develop alternative designs for process intensification. To describe the process, a computational fluid dynamics-based model was developed and validated against experimental data from literature. Based on this model, parametric studies were performed to gain a deeper understanding of the microchannel geometry influence. Furthermore, two geometry modifications were suggested and analyzed, a miniaturization of the channel and an implementation of baffles. The modification with baffles was chosen for a new separator design which was studied experimentally, and the obtained experimental data were used for another model validation, this time for the baffle arrangement. Subsequent comprehensive simulations were performed to investigate mass-transfer enhancement by the modified geometry. Generally, the baffles reveal a considerable potential for the process intensification. (c) 2015 American Institute of Chemical Engineers AIChE J, 61: 2240-2256, 2015