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Single microchannels and their arrangements for liquid mixing are investigated numerically. A smaller lateral inlet diameter and the zigzag form of the channels are found to be beneficial for the mixing performance in microchannels. Under proper operational conditions, the mixing process can be almost completed. Furthermore, some constructal distributor designs for the arrangement of microchannels are proposed and analyzed with regard to the fluid distribution. For the optimized distributor, the standard deviation from perfectly even distribution does not exceed 4% while keeping the pressure drop low. Two multichannel micromixer designs are suggested, with accordingly optimized microchannels and distributors, and their mixing performance is very close to that of a single microchannel. The specific energy dissipation in the multichannel micromixer is in the range of 0.016−93 W/kg, which is similar to batch reactors. Finally, the design procedure for multichannel micromixers is proposed.

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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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2240–2256, 2015