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The present study investigates the effect of cross-links on flow boiling heat transfer characteristics in rectangular microchannel heat sinks, using FC-72 as the working fluid. The silicon test section consists of 45 cross-linked microchannels, measuring 16 mm in length, with a hydraulic diameter of 248 μm. The parameters investigated include mass flux, heat flux, and exit quality, ranging from 99–275 kg/m2 s, 7.2–88.8 kW/m2 , and 0.01–0.71, respectively. Thermochromatic liquid crystals have been used in the present study as full-field surface temperature sensors to map the temperature distribution on the heat sink surface. The flow boiling heat transfer coefficient shows a different trend in the cross-linked design relative to the straight microchannel design. The flow boiling heat transfer coefficient increases with increasing exit quality at a constant mass flux, which is caused by the domination of the nucleation boiling mechanism in the cross-link region. The predictions obtained from the existing heat transfer correlations found in the literature significantly under-estimate the present heat transfer measurements, except for the Yu et al. (2002) correlation.Copyright © 2009 by ASME