CAREER: Vapor-Liquid Separation for Sustainable Condensation Heat Transfer

冷凝换热性能的提高降低了制冷、空调、热交换器和热管理系统的尺寸、重量和成本。为了获得较大的换热系数，必须迅速去除表面上的冷凝物，以提供无液体的区域，以便发生汽液相变化。理想的表面应能提供较大的换热面积，并能迅速去除冷凝物以实现可持续冷凝。目前的挑战包括去除超低表面张力制冷剂以及工程表面缺乏长期耐久性。这个职业项目的目标是通过开发汽液分离工艺来推进超低表面张力流体的冷凝换热，并将新知识整合到教育中以培养下一代热传导者，以应对这些挑战。该项目的目标是实现：(1)超低表面张力流体(例如R134a)的滴状冷凝；(2)可持续的汽液分离，为快速冷凝提供大片无液区域。所提出的方法将使用新开发的耐用准液体表面来实现滴状冷凝和快速去除超低表面张力冷凝物。超光滑的准液体表面将阻止滴状向膜状的转变。为了获得高的换热性能，汽液将在光滑的粗糙表面上进行准液体润滑，这将为冷凝提供较大的表面积。X射线纳米成像将用于研究光滑粗糙表面微结构中的成核和液体去除。研究了准液体润滑微结构在不同过冷和剪切应力条件下的表面耐久性和持续凝结性能。传热学和材料制造方面的初步结果为开展这些活动提供了坚实的基础。该提议的项目符合PI的长期职业目标，即通过结合多学科领域的学习来解决热传递挑战。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。

Improving the performance of condensation heat transfer reduces size, weight, and cost in refrigeration, air conditioning, heat exchangers, and thermal management systems. To achieve a large heat transfer coefficient, condensates on a surface must be rapidly removed to provide liquid-free areas for vapor-liquid phase change to occur. The ideal surface is one that provides a large heat transfer area and rapidly removes condensates for sustainable condensation. Present challenges include the removal of ultralow surface tension refrigerants and the lack of long-term durability of engineered surfaces. The goal of this CAREER project is to address those challenges by developing a vapor-liquid separation process to advance condensation heat transfer of ultralow surface tension fluids, and integrate the new knowledge into education to train the next generation of heat transfer leaders.The objective of this project is to achieve: (1) dropwise condensation of ultralow surface tension fluids (e.g., R134a), and (2) sustainable vapor-liquid separation that provides large liquid-free areas for rapid condensation. The proposed approach will use the newly developed durable quasi-liquid surface to achieve dropwise condensation and rapid removal of ultralow surface tension condensates. The super slippery quasi-liquid surface will prevent the dropwise to filmwise transition. To achieve a high heat transfer performance, the vapor and liquid will be separated on a slippery rough surface with quasi-liquid lubrication which will provide a large surface area for condensation. X-ray nano-imaging will be used to investigate the nucleation and liquid removal inside microstructures of the slippery rough surfaces. The surface durability and sustainable condensation performance of quasi-liquid lubricated microstructures will be studied under various subcooling and shear stress conditions. The preliminary results in heat transfer and materials fabrication provide a solid foundation to execute those activities. The proposed project is in line with the PI’s long-term career goal to address heat transfer challenges by incorporating learning from multidisciplinary areas.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.