微纳耦合表面池沸腾强化传热的实验研究

The Experiment Study of Pool Boiling Heat Transfer Enhancement on Micro-nano Surface

以去离子水为工质,拟在钛板表面利用线切割进行微槽处理,采用阳极氧化法制备出二氧化钛纳米管阵列的微纳耦合表面,研究该表面的强化沸腾传热性能.通过场发射扫描电镜表征其微观结构形貌,利用接触角测量仪检测表面的静态接触角.结果表明,与光板相比,微槽结构增大了传热表面,规整的纳米管阵列具有亲水特性,接触角明显减小,微纳耦合表面的传热系数和临界热流密度分别达到了15.5 kW·m^(-2)·℃^(-1)和420.1 kW·m^(-2),分别提高了158.3%和50%,结合实验现象及机理分析可知,微纳耦合表面的微通道结构为气泡继续生长提供了支撑,有效避免了换热壁面被合并的大气泡完全覆盖;过热度达到一定温度后,更小的活化中心被激活,过热度随着热流密度的上升出现下降的趋势。微纳耦合表面对池沸腾具有强化作用。

The heat transfer enhancement on different surface was studied with distilled water. The surface of pure titanium plate was deal with micro-channels by wire-cutting, and then TiO2 nanotube layers were prepared on this surface, which was micro-nano surface. Microstructures of TiO2 nanotubes were characterized by SEM. Static contact angle was obtained on the coatings via optical contact angle measuring device. The results show that micro-channels increase the heat transfer surface, and the surface with TiO2 nanotubes arrays with hydrophilic properties, contact angle decrease obviously. Compared with the untreated titanium plate, both micro-channels and the surface with TiO2 nanotubes arrays were enhanced heat transfer coefficient and critical heat flux. The micro-nano surface improved the heat transfer coefficient and the critical heat flux by 158.3% and 50%. The heat transfer coefficient was 15.51W·m^-2·℃^-1 and CHF was 420.1 kW·m^-2. According to the experimental phenomenon and mechanism analysis, the microchannel structure propped bubbles up to grow, effectively avoid that the heat transfer surface completely was covered and merged by large bubbles. The smaller vaporization core activated at a higher super heat and the super heat doesn＇t increase with the increasing heat flux anymore. The micro-nano coupling surface can enhance the pool boiling.