EAGER: Experimental Study of Condensation Enhancement on Durable Slippery Surfaces

强化冷凝提高了发电厂的效率、水的收集、海水淡化和制冷。理想的强化冷凝表面必须提供较大的换热面积，并在经久耐用的操作中快速去除液滴。到目前为止，由于在液滴去除和表面耐久性方面的科学挑战，这一点无法实现。首先，由于粗糙表面上的钉扎力很大，所以在与空气无关的粗糙表面上没有实现被动的液体排斥。其次，在水滴持续脱落的蒸汽环境中，表面的耐久性是不可持续的。现有的大多数拒液表面依赖于空气润滑剂的存在，空气润滑剂在蒸汽环境中或与低表面张力流体接触时可以被置换，导致凝析油去除失败。这个迫切的项目的目标是通过开发以前没有实现的亲水性和光滑的粗糙表面来应对这些挑战。研究成果与外联和教育相结合，招募和培训了代表性不足的学生。PI还积极与德克萨斯州的工业公司接洽，寻求这项研究的广泛影响。对与空气无关的光滑粗糙表面上的凝结强化的实验研究导致了与超疏水表面上的空气依赖凝结不同的概念策略。这种亲水光滑的粗糙表面为冷凝提供了较大的表面积，同时保持了较小的接触角滞后，用于冷凝液的去除。研究目标包括：(1)实验证明光滑粗糙表面与最先进的冷凝表面相比可以显著提高冷凝换热系数；(2)了解光滑粗糙表面在连续液滴脱落的蒸汽环境中的破坏机理。为了提高表面耐久性，聚合物链被接枝到粗糙的基板上，以同时增强传热面积和液滴去除。该项目开发了耐用的独立于空气的光滑粗糙表面，用于特殊的冷凝强化。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Enhancing condensation improves power plant efficiency, water harvesting, desalination, and refrigeration. An ideal surface for condensation enhancement must provide large heat transfer areas and rapid droplet removal in durable operations. Until now, this could not be achieved because of scientific challenges in both droplet removal and surface durability. First, the passive liquid repellency on air-independent rough surfaces has not been achieved due to the large pinning forces on rough surfaces. Second, the surface durability in a steam environment with continuous droplet shedding cannot be sustained. Most of existing liquid-repellent surfaces rely on the existence of air lubricant, which can be displaced in a steam environment or in contact with low surface tension fluids, leading to the failure of condensate removal. The goal of this EAGER project is to address those challenges by developing previously unachieved hydrophilic and slippery rough surfaces. The research outcomes are integrated with outreach and education, with under-represented students recruited and trained. The PI also actively approaches the industrial companies in Texas for broad impact of the research .The experimental study of condensation enhancement on air-independent slippery rough surfaces leads to a conceptually different strategy from the air-dependent condensation on superhydrophobic surfaces. This hydrophilic slippery rough surface gives a large surface area for condensation and in the meantime keeps a small contact angle hysteresis for condensate removal. The research objectives include: (1) experimentally demonstrate that the slippery rough surfaces can significantly increase the condensation heat transfer coefficient compared with the state-of-the-art condensing surfaces, and (2) understand the failure mechanism of this surface in a steam environment with continuous droplet shedding. To improve surface durability, polymer chains are grafted on the rough substrate to simultaneously enhance heat transfer areas and droplet removal. This project leads to the development of durable air-independent slippery rough surfaces for exceptional condensation enhancement.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.