With the recent increase in power density and miniaturization of various equipment

the requirements for compactness and efficiency of heat exchangers become increasingly stringent. Micro-structured surfaces have a significant impact on flow patterns and heat transfer mechanisms during flow boiling. To examine the effect of heterogeneous wetting surfaces on the flow boiling process

an experiment on subcooled vertical flow boiling on heterogeneous wetting surfaces in a narrow rectangular microchannel was conducted using a high-speed camera. Deionized water was used as the working fluid

and the cross-section of the channel was 0.5 mm × 5 mm. The mass fluxes of the subcooled flow boiling were 300 kg/(m2?s) and 400 kg/(m2?s). The heat flux was within 30–300 kW/m2. The experiment was conducted under atmospheric pressure

and the subcooling degree was 10 K. Hydrophobic patterns perpendicular (HC) and parallel (HP) to the flow direction were compared. The subcooled boiling curves

heat transfer coefficient

and pressure drop were investigated with respect to the variations in heat flux and mass flux

and their trends were analyzed along with the flow patterns. The heat transfer coefficient of flow boiling on heterogeneous wetting surface HC was enhanced by as much as 39.55% compared with a silicon surface with less pressure drop. During the boiling process

the dominant heat transfer mechanism was nucleate boiling

with numerous nucleation sites between the hydrophilic/hydrophobic stripes.