The increasing heat dissipation from electronic devices on board satellites makes it necessary to find solutions for their cooling. In the present case, 20 electronic components in series need to dissipate a heat flux of 20 kW/m(2) owing to microevaporators mounted in a refrigeration system. An approach for optimizing the design of the evaporators based on the entropy generation minimization is presented here. To solve this thermal problem, a steady-state three-dimensional conduction model is combined with thermohydraulic flow boiling models valid for microchannels. The best design corresponds to an aspect ratio (ratio between height and width) around 8.8. The sensitivity of the results to the choice of the flow boiling models is also analyzed.