亲/疏水两层结构表面协同排液、强化冷凝传热的机理研究

The heat transfer coefficient of dropwise condensation is much higher than that of film condensation. It is the key problem to improve condensation heat transfer by reducing the droplet diameter and discharging liquid in time. In this project, a scientific idea was proposed using two layer surfaces with hydrophilicity/hydrophobicity to enhance condensation heat transfer. First，in accordance with the principle of condensation heat transfer and droplet dynamics, the construction and characterization of surfaces, dynamics measurement of droplet on surfaces were conducted. Then convective condensation heat transfer and heat transfer characteristics of anti-gravity flat heat pipe with two layer surface were studied. The study focus on the regularity that how the structure parameters and wettability of surfaces affect condensation heat transfer, by reducing droplet diameter, accelerating liquid movement, promoting the inhalation and drainage of liquid. Functional coordination and scale matching of two layer surfaces were also explored in dropwise condensation. A mathematical model for droplet growth, droplet movement, droplet bounce and liquid suction is established, and the numerical simulation is carried out using the finite volume method based on lattice Boltzmann. Experiments and theories are verified each other to reveal the mechanism of the interaction between two layer surfaces and the condensation heat transfer. This project belongs to interdisciplinary frontier areas, in which the material preparation, modification and the cooperation were introduced. It will not only provide a theoretical basis for high efficient condensation heat transfer, but also provide guidance for the design of new type of compact condenser.

针对滴状冷凝传热系数远高于膜状冷凝，减小液滴直径并及时脱离是提高冷凝传热的关键性问题。本项目提出采用亲/疏水两层结构表面协同排液，强化冷凝传热的构想,首先对符合冷凝传热及液滴动力学原理的结构表面进行构建、表征、及液滴动力学测量。然后以对流冷凝传热和液滴弹跳型反重力平板热管传热为载体，研究亲/疏水两层表面的各特征参数、亲/疏水性对减小液滴脱离直径，加速液滴移动，促进液滴吸入并转移排除，从而强化冷凝传热的影响和过程规律性，以及亲/疏水两层表面在冷凝传热中的功能协同及尺度匹配。建立液滴生长、液滴移动、液滴弹跳及液体吸入的数学模型并运用基于格子Boltzmann的耦合有限容积法进行数值模拟。实验与理论相互验证，揭示亲/疏水两层结构表面协同排液，强化冷凝换热的机理。本项目属于多学科交叉前沿领域，将材料的制备、改性与协同性引入到冷凝传热中，既为冷凝传热提供理论基础，又为新型紧凑式冷凝器的设计提供指导。

项目针对滴状冷凝传热系数远高于膜状冷凝，减小液滴直径并及时脱离是强化冷凝传热的关键。项目提出采用亲/疏水结构表面协同排液，强化冷凝传热的构想，从亲/疏水结构表面制备、表征，液滴动力学，平面对流冷凝传热以及平板热管的应用等方面进行研究，出色完成了任务和目标，创新性工作如下：.借助仿生学原理，开发了低成本制备亲/疏水性两层结构表面的方法。烧结制备了多尺度乳突结构，利用氧化和表面改性等手段获取了超亲水和超疏水组合表面，研究了液滴在不同润湿性表面上的液滴动力学和多孔结构的反重力吸液特性，发现了液体在吸液芯内部的两种不同扩散模式。研究了平面对流冷凝传热，提出了“超疏水表面滴状冷凝，超亲水乳突吸液引流”的新思想，可达到“及时引流，协同排液”的预期功能。揭示了亲/疏水性两层结构表面在减小液滴脱离直径，减小液膜厚度、提高冷凝传热系数的机理。当过冷度为1.5K时，组合表面的冷凝传热系数分别是单一超疏水表面和光滑铜表面上的2倍和4.3倍。.研究了亲/疏水性两层结构表面反重力平板热管的传热性能，获取了亲/疏水性两层结构表面在有效控制反重力平板热管启动温度、减小或消除热管中流动与传热不稳定性方面的效果及机理，发现了冷凝所形成的液滴在高/低粘附超疏水表面上脱离形式的差别和规律性；探索了亲/疏水性两层结构表面的反重力平板热管的传热特性，实现了热管从对流传热到核态传热的转变及自适应传热，使热管的传热性能大大提高。建立了材料表面功能与结构尺度、润湿性的关联，微观和宏观的融合，将材料的制备、改性与协同性引入到冷凝传热中，为新型紧凑式散热器的设计提供了很好的指导，具有重大的节能减排和社会经济效益。.共发表论文31篇（期刊论文24篇，会议论文7篇）(包括SCI论文6篇，EI论文15篇)，其中Nano Energy期刊论文1篇（影响因子15.5），申请专利5项（获授权3项），培养硕士生5名，其中4名获优秀毕业生称号。参加国际会议1次，开展了广泛的国内外合作与交流。