人工核化点超疏水混合梯度表面对冷凝液滴成核及运动行为的协同作用机理及强化传热研究

This project is based on the synergetic role of artificial nucleation sites in enhancing the condensing droplet nucleation and the superhydrophobic gradient surface to promote the condensation droplet discharge. Theoretical analysis and experimental research are combined to carry out the research. Artificial hydrophilic nucleation sites were used to increase the nucleation density of the droplets. Relationship between wetting performance, scale and arrangement of artificial nucleation sites, and the nucleation density of the droplets could be investigated. Mechanism of condensation nucleation density enhancement by the wetting performance, scale, and multi-scale of artificial nucleation sites were obtained. Meanwhile, a mathematic model for the droplet movement on super-hydrophobic gradient surface condensation was established. The law of accelerating the movement of droplets through gradient surfaces could be studied, and the coupling mechanism of multiple parameters such as surface morphology and scale on the movement of droplets were obtained. On this basis, experiments were conducted to study the nucleation and movement behavior of condensation droplets under the combined action of artificial nucleation sites and super-hydrophobic gradient surfaces, revealing the synergetic mechanism of the droplet nucleation and discharge by the parameters such as artificial nucleation sites moisture properties, arrangement, placement and the superhydrophobic surface structures and scale. The surface design criteria to promote the nucleation and discharge of condensate droplets based on controllable parameters such as the scale, morphology, wetting properties, and arrangement of the surface structure are proposed. Finally, this project developed a superhydrophobic gradient surface with artificial nucleation sites that can enhance condensation heat transfer.

本项目基于人工核化点强化冷凝液滴成核和超疏水梯度表面促进冷凝液滴排出两个过程对冷凝换热的协同促进作用，采用理论分析与实验研究相结合方法进行研究。提出采用人工亲水核化点增加液滴成核密度，研究人工核化点润湿性能、尺度及布置与液滴成核密度间关系，得到人工核化点润湿性能、跨尺度及多尺度人工核化点及核化点分布对强化冷凝液滴成核的影响机理；同时建立超疏水梯度表面冷凝液滴运动数学模型，研究通过梯度表面加速液滴运动的规律，获得表面结构形态、尺度等多参数对液滴运动的耦合作用机理；在此基础上，实验研究人工核化点和超疏水梯度表面共同作用下，冷凝液滴成核与运动行为，揭示人工核化点的尺度、润湿性能、布置及超疏水表面结构的形态、尺度等对强化冷凝液滴成核与排出的协调作用机制，提出基于表面结构尺度、形态、润湿性能及布置等可控参数的促进冷凝液滴成核与排出的表面设计准则，研制一种能强化冷凝换热的人工核化点超疏水混合梯度表面。

冷凝换热中成核和液滴排出是影响传热的关键过程，换热表面的润湿性能对冷凝成核和液滴移动行为具有重要影响，如何在充分满足液滴成核同时促进液滴排出，是目前高效冷凝换热中亟待解决的关键问题。.本项目从表面微结构润湿性能、微结构形貌对冷凝液滴成核及排出的机理出发，通过理论分析与实验研究相结合的方法，揭示了人工微结构和天然微结构表面的液滴冷凝成核和运动机理，建立了表面微结构与液滴三相线移动行为之间的数学模型，提出了通过表面微结构形成亲水性人工核化点和超疏水性润湿梯度协同作用下强化冷凝换热的混合梯度表面的设计准则。.主要研究成果包括：.（1）基于标准MEMS工艺设计并加工多种微结构表面，利用高速可视化光学实验系统发现了亲水核化点尺度变化、分布密度变化的表面上，液滴成核密度随核化点密度增大而增加、随核化点尺度增大而减小。.（2）基于能量原理并结合液滴前进后退接触角的变化，建立了具有不同形态的微结构超疏水梯度表面上，液滴三相线移动过程的理论模型。搭建多维度可视化高速同步图像采集实验系统，发现由微结构不均导致的液滴运动过程中的非对称分离、受力不均现象；三相线非对称移动、非对称脱离现象；以及处于不同微结构阵列区域的三相线运动差异。.（3）提出了通过表面微结构形成亲水性人工核化点和超疏水性润湿梯度协同作用下强化冷凝换热的混合梯度表面的设计准则。.（4）同时，为研究液滴与微结构表面脱离过程，设计了一种测量液滴与微结构表面间粘附力的测量装置和测量方法，为我国微纳测量仪器设计与制造提供了依据。. 本项目按照预定研究计划执行，未进行调整。依托本项目，共发表论文12篇，其中SCI/EI检索7篇，授权发明专利1项、实用新型专利2项、软件著作权1项，申请在审发明2项，详见附表，所列成果全部标注本项目资助；参加国内基金进展学术交流会2次；项目执行期间，项目组成员1人获正高、2人获副高、1人获中级职称，培养多名本科生参与项目研究。