铜基超疏水-超亲水图型化混合表面强化滴状冷凝传热机理研究

Vapor condensation is widely applied in power generation, water desalination, industrial waste heat utilization, and refrigeration. Breakthrough of condensation technology can significantly decrease heat exchange areas and solve the high heat flux problems of condenser in confined space, and improve energy efficiency. The proposed research is based on the design of hydrophobic-hydrophilic surface and combines the advantages of superhydrophobic surfaces associated with high condensation heat transfer coefficients with those of superhydrophilic surfaces which has low nucleation thermal resistance and high nucleation rates. The PI proposes a project of hybrid superhydrophobic and superhydrophilic patterned surfaces on copper substrates which can improve dropwise condensation. This novel hybrid condensation surface plays a key in enhancement of dropwise condensation heat transfer performance. It can control condensation droplets nucleation rates, maximum droplet radius, droplet size distribution, and droplet removal frequency through superhydrophilic region patterns, pattern sizes, and distances between two neighboring superhydrophililc areas. The proposed research integrates visualization and heat transfer characteristic experiments, mathematical models, and lattice Boltzmann methods to investigate droplet behaviors and heat transfer mechanism of hybrid superhydrophobic and superhydrophilic patterned surface. It is expected that a highly efficient dropwise condensation technology and optimal design of heterogeneous condensation surfaces will be demonstrated.

蒸汽冷凝换热过程广泛存在于火力发电、海水淡化、工业废热利用及制冷等工业领域。强化冷凝换热技术的突破,可大幅降低所需换热面积，解决受限空间内高热流密度冷凝换热问题，提高能源利用率。本项目基于疏水-亲水组合表面强化换热这一理念，结合超疏水表面高冷凝传热系数与超亲水表面低成核热阻、高成核速率的优势，提出了铜基超疏水-超亲水图型化混合表面强化滴状冷凝换热技术。该新型超疏水-超亲水图型化混合表面可通过调节超亲水区域图案、图案尺寸和邻间距对冷凝液滴核化速率、最大液滴半径、液滴尺寸分布以及液滴移除频率进行调控，对于强化滴状冷凝传热性能起到关键作用。本研究采用可视化及传热实验、数学模型和格子Boltzmann数值模拟等方法，揭示超疏水-超亲水图型化混合表面对冷凝液滴行为的调控机制及强化滴状冷凝传热机理。本项目研究成果可以为优化非均匀润湿性冷凝表面设计提供科学依据，对探寻强化冷凝换热技术具有很好的参考意义。

亲/疏水组合表面因具有独特的各向异润湿性，在强化冷凝换热方面具有巨大的应用前景和研究价值。本项目结合超疏水表面高冷凝传热系数与超亲水表面低成核热阻、高成核速率的优势，提出了铜基超疏水/超亲水图型化混合表面强化冷凝换热技术，针对图型化混合表面冷凝液滴动态行为和传热特性等方面开展研究，重要结论和进展如下：（1）采用MEMS光刻法和化学蚀刻方法实验制备了五种不同图案尺寸和邻间距的铜基超疏水/超亲水图型化混合表面，通过高速显微摄像和环境扫描电子显微镜（ESEM）对图型化混合表面润湿条件下液滴生长融合、聚并弹跳等运动行为进行了可视化观测，探索了冷凝液滴在图型化混合表面动力学行为规律；（2）查明了图型化混合表面对冷凝液滴脱离直径、液滴尺寸分布以及液滴脱离频率的调控机制，研究发现，图型化混合表面相比于超疏水表面具有更高的液滴脱离频率是强化传热性能的主要原因，非均匀润湿性表面可诱发液滴快速脱离，提高冷凝传热效果。冷凝液滴脱离直径受图案邻间距影响较大，超亲水图案邻间距越小，液滴合并越剧烈，液滴的尺寸相对较大；（3）设计搭建了冷凝传热特性测试实验台，系统开展了蒸汽工况下不同图型化混合表面冷凝传热性能评估，获得了传热效果最优的图型化混合表面设计，其冷凝传热系数是超疏水表面的1.7倍，冷凝热流密度在实验过冷度范围内相比于超疏水表面可提高31-73%；（4）基于能量方程和动量方程，建立了冷凝液滴在图型化混合表面合并诱导弹跳速度数学模型；（5）发表SCI论文4篇，申请发明专利2项，培养硕士研究生3名。