氧化铝渐变纳米孔阵列结构强化沸腾传热性能研究

Pool-boiling, a new powerful cross-disciplinary point of interface physicochemical and engineering thermophysicsa, has attracted great interest due to the efficient heat transfer ability based on the large latent heat absorbtion of vaporization. The key to enhance the pool-boiling heat transfer is making the high-efficient bublle nucleation as well as the rapid departure of these bubbles from the heated surface, which closely related to the structural morphology and wettability of the material surface. However, the effects of the nanostructure parameters (profile, period and size) and wettability on the growth kinetics of bubbles is unknown. Based on our research works on modulating the profiles and periods of self-ordered three-dimensional alumina taper-nanopores, this project is intended to focus on studying the synergistic effect of structural parameters and surface chemistry of the self-ordered alumina taper-nanopores on its liquid-gas phase transition and pool-boiling heat transfer enhancing. The research including: the in-situ growth of self-ordered alumina tapered-nanopore arrays with controlled structural parameters on the surface of aluminium rod, and fabricate cylindrical nanopore as control; modify the surface of the alumina nanopores with different silane which has different surface energy, studying the synergistic effect of structural parameters and surface chemistry of alumina nanopores on its liquid-gas phase transition and pool-boiling heat transfer enhancing, the key point is regulation the active bubble nucleation sites and the bubble departure frequency; exploring the influence of the intrinsic thermal conductivity on the pool-boiling heat transfer performance and proper working condition of alumina nanopore arrays, which can provide the possibility for its potential application. These results help to have a deep insight to the regulation mechanism of the liquid-gas phase transition and pool-boiling heat transfer of the nano-interface, and design nanomaterials with high pool-boiling heat transfer efficiency.

基于界面液气相变过程调控以实现热量高效传递的沸腾传热研究已成为近年来界面物化与工程热物理高度交叉的新兴学科生长点。强化沸腾传热的实质是使界面气泡高效产生并快速脱离，而气泡生长动力学与材料表面结构和浸润性密切相关，但迄今为止其调控规律尚不清楚。基于申请人在氧化铝梯度渐变纳米孔可控制备方面取得的最新成果，本项目拟重点开展自有序渐变孔的几何参数和表面化学协同效应对强化界面沸腾相变过程和传热能力的调控规律研究。内容包括：铝棒表面梯度渐变纳米孔阵列结构原位构筑，同时以柱孔阵列作为空白对照；在周期性纳米孔阵列结构表面修饰不同表面能硅烷分子，研究结构和表面化学协同对强化液气相变及传热过程的影响，重点调控气泡成核点密度和气泡脱离频率；探索氧化铝纳米孔阵列结构本征热导率对沸腾传热的影响极其稳定的服役工况条件。相关研究成果有助于深入理解纳米界面液气相变及传热过程调控机理及设计开发高效节能沸腾传热材料。

基于界面液气和气液相变过程调控以实现热量高效传递的沸腾和冷凝传热研究已成为近年来界面物化与工程热物理高度交叉的新兴学科生长点。强化沸腾/冷凝传热的实质是使界面气泡/冷凝液滴高效产生并快速脱离，而气泡/冷凝液滴生长动力学与材料表面结构和浸润性密切相关。纳米棒孔复合结构以及纳米锥结构由于具有极小的固气/固液接触面积，因此经亲水/疏水修饰后能够有效的促进气泡/冷凝液滴的脱离和产生从而提高传热效率。本项目重点研究了经亲、疏水化处理后的纳米棒孔复合结构和纳米针锥结构表面上气泡和冷凝液滴超浸润行为，内容包括：1 铜铝表面纳米结构的可控制备。 深入研究了氧化铝自有序原理并制备了大周期氧化铝纳米孔和棒孔复合结构，同时采用电化学沉积的方法在铜表面构筑了铜纳米锥及氢氧化铜纳米针团簇。 2 氧化铝纳米棒孔复合结构的超浸润性能研究。 表征和分析了在水中亲水棒孔复合结构与气泡的粘附力以及疏水化后的棒孔复合结构表面冷凝液滴的自驱离行为并以柱孔结构为对照。3 纳米界面沸腾和冷凝相变过程及高效传热研究。 通过对自有序阳极氧化铝纳米多孔结构的周期、孔壁厚度及深度的独立调控，研究了沸腾临界温度随几何参数的调控规律；研究了表面经亲水处理后的铜纳米锥表面的沸腾传热性能和经疏水化处理后的氢氧化铜纳米团簇的冷凝传热性能，发现纳米结构表面的热流密度及换热系数相对光滑铜表面均有大幅度的提升。相关研究成果有助于深入理解纳米界面液气和气液相变及传热过程调控机理及设计开发高效节能沸腾和冷凝传热材料。