The paper reports heat-transfer measurements for condensation of pure steam and steam-ethanol mixtures in parallel horizontal microchannels in an aluminum test section cooled from above and below by water in counter-current flow. The local heat flux and channel surface temperature were determined from temperatures measured by 100 thermocouples accurately located in small holes above and below the microchannels and spaced at 10 locations in the flow direction. Tests were conducted for a range of vapor mass fluxes and cooling intensities. The streamwise distributions of channel heat flux, channel surface temperature and vapor quality were obtained by curve-fitting the test block temperatures. Heat-transfer coefficients were obtained for the cases where complete condensation did not occur in the channels by assuming linear pressure distribution between accurately measured pressures at inlet and exit and assuming saturation conditions in the two-phase flow region of the channels.

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