Arrays of 68 microchannels, each one 200 μm wide, 100 μm deep and 40 mm long, were fabricated by mechanical micro-machining of brass foils, and used to evaporate water in the mass flux range between 61 kg m−2s−1 and 123kg m−2s−1 in an electrically powered device. Three different microchannel designs were tested: straight channels with and without impactor structures at the microchannel exits, and curved channels following a sinusoidal path. Variations of the average steam quality inside the microchannel arrays (pulsation) were observed by high-speed videography. Even when the device as a whole produced overheated steam, pulsation inside the channel array near the outlet, spatial maldistribution of the two phase flow, and liquid water reaching the outlet plenum were observed in many cases. From these observations and their analysis, conclusions are drawn for the further empirical optimization of microchannel array evaporators.

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