超疏水表面微通道内水的传热特性

微通道传热效率高但流动阻力大，超疏水表面因其与水具有滑移边界而表现出低流阻的特征,在微过程中具有应用前景。利用化学刻蚀法制备出具有微纳米阶层结构的铝基超疏水表面微通道(内径为0.68mm)。在超疏/亲水微通道内进行了水的流动传热实验研究，并将结果进行对比。研究发现存在于超疏水表面微纳米结构里的气泡层减小了水的流动阻力，也降低了表面传热系数，但降低程度明显小于流动阻力的降低,传热系数高于考虑纳米气泡层计算的传热系数。因此认为在水的滑移速度作用下，凹穴中微纳米级气泡内产生了气体的涡旋流动，一定程度上增强了传热效果。

Heat transfer characteristics of water flowing in microchannels with super-hydrophobic inner surface

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.