Song Youngsup, Gong Shuai, Vaartstra Geoffrey, Wang Evelyn N
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
ACS Appl Mater Interfaces. 2021 Mar 17;13(10):12629-12635. doi: 10.1021/acsami.1c00750. Epub 2021 Mar 8.
Boiling is an essential process in numerous applications including power plants, thermal management, water purification, and steam generation. Previous studies have shown that surfaces with microcavities or biphilic wettability can enhance the efficiency of boiling heat transfer, that is, the heat transfer coefficient (HTC). Surfaces with permeable structures such as micropillar arrays, in contrast, have shown significant enhancement of the critical heat flux (CHF). In this work, we investigated microtube structures, where a cavity is defined at the center of a pillar, as structural building blocks to enhance HTC and CHF simultaneously in a controllable manner. We demonstrated simultaneous CHF and HTC enhancements of up to 62 and 244%, respectively, compared to those of a smooth surface. The experimental data along with high-speed images elucidate the mechanism for simultaneous enhancement where bubble nucleation occurs in the microtube cavities for increased HTC and microlayer evaporation occurs around microtube sidewalls for increased CHF. Furthermore, we combined micropillars and microtubes to create surfaces that further increased CHF by achieving a path to separate nucleating bubbles and rewetting liquids. This work provides guidelines for the systematic surface design for boiling heat transfer enhancement and has important implications for understanding boiling heat transfer mechanisms.
沸腾是包括发电厂、热管理、水净化和蒸汽产生在内的众多应用中的一个重要过程。先前的研究表明，具有微腔或双亲润湿性的表面可以提高沸腾传热效率，即传热系数（HTC）。相比之下，具有诸如微柱阵列等可渗透结构的表面已显示出临界热流密度（CHF）的显著提高。在这项工作中，我们研究了微管结构，即在柱体中心定义一个腔，作为结构构建块，以可控方式同时提高HTC和CHF。与光滑表面相比，我们分别展示了CHF和HTC同时提高高达62%和244%。实验数据以及高速图像阐明了同时提高的机制，即微管腔内发生气泡成核以提高HTC，微管侧壁周围发生微层蒸发以提高CHF。此外，我们将微柱和微管结合起来，通过实现分离成核气泡和再润湿液体的路径来创建进一步提高CHF的表面。这项工作为系统的表面设计以增强沸腾传热提供了指导方针，并且对理解沸腾传热机制具有重要意义。
