Liquid convective heat transfer in microchannels exhibits high efficiencyHowever

the large pressure drop causes much concern for practical applicationWater flowing in hydrophobic tubes shows low pressure drop owing to the slippage on the tube wallsSuper-hydrophobic/hydrophilic micro aluminum tubes of 0.68mm inner diameter were fabricated with a two step procedure of chemical etching and then surface chemical modificationA kind of micro-nanometric hierarchical structure was formed on the surface

which could trap air serving as the slip agentHeat transfer and fluid flow of deioned water flowing laminary in the super-hydrophobic/hydrophilic microchannels were studied experimentallyThe results showed that the air-layer existing in the micro-nano hierarchical structures of the superhydrophobic surface decreased flow resistance evidently but decreased heat transfer coefficient only a little

which was still higher than the superficial heat transfer coefficient while considering the heat conduction of stationary nanolayer of airIt was supposed that eddy flow was generated in the micronano bubbles by the slip flow of water on the tube wall

which enhanced the heat transfer.