ISS: Collaborative Research: Thermally activated directional mobility of vapor bubbles in microgravity using microstructured surfaces

这项研究将使蒸汽泡在没有重力驱动的浮力的情况下流动，这些浮力来自经历沸腾的表面。研究小组将在国际空间站(ISS)上飞行名为气孔形成和流动性调查(PFMI)炉的飞行硬件包的略微改进版本。长期以来，蒸汽泡无法从表面分离，一直阻碍着太空中电子元件高效相变散热的实现。研究小组的努力是基于一种新型的不对称表面微结构，这种结构可以在不使用外力的情况下产生蒸汽气泡的运动。纹理表面的形式是重复的毫米级不对称棘轮，具有30-60度的面。要测试的假设是，这种结构化表面为不利地面取向和微重力环境下的电子热管理提供了沸腾中的蒸汽团的迁移率，从而缓解了过早的疲劳。在可变重力环境中以及在相反方向的加热表面中影响蒸汽气泡被动运动的可能性可能会产生深远的好处。长期目标是开发一种用于消费电子产品和飞机电子产品的散热器的简单、被动、自我调节的微结构表面技术。国际空间站的实验设计、开发和实施将与CASIS实施伙伴TBE合作，利用航空航天承包商丰富的飞行实验专业知识。具体目标有三个：验证在国际空间站实验室的微重力飞行实验中观察到的横向气泡运动，执行地面实验和分析以验证/改进分析模型，以及探索地面应用。插入PFMI的密封方形横截面安瓶将被重新配置，以适应平面加热的棘轮表面。安瓶的设计将以改进后的开放式渠道设施中的地面实验为指导。作为该项目的一部分，将在国际空间站和陆地环境中进行高速可视化和传感器测量。这些数据可以被传热界的计算专家用作沸腾数值模拟的验证案例。从国际空间站和地面实验获得的数据和视频图像将在NASA的物理科学信息学(PSI)数据库中传播，用于在国际空间站进行的实验。除了为研究生辅导提供途径外，该项目还将通过加州大学伯克利分校的麦克奈尔奖学金计划和奥本的阿拉巴马州太空助学金计划，让未被充分代表的本科生参与其中。

This study will enable the mobility of vapor bubbles in the absence of gravity-driven buoyancy from surfaces experiencing boiling. The research team will fly a slightly modified version of a flight hardware package called the Pore Formation and Mobility Investigation (PFMI) furnace aboard the International Space Station (ISS). The inability of vapor bubbles to detach from a surface has long impeded the implementation of efficient phase-change heat dissipation from electronics components in space. The research team's efforts are based on a novel asymmetric surface micro-structure that produces movement of vapor bubbles without the use of externally applied forces. The textured surfaces are in the form of repeating millimetric-scale asymmetric ratchets with 30-60 degree faces. The hypothesis to be tested is that such structured surfaces provide mobility to vapor mass in boiling for electronics thermal management under adverse terrestrial orientations and microgravity environments, thereby mitigating premature burnout. The potential to affect passive motion of vapor bubbles in variable gravity environments, as well as in adversely oriented heated surfaces could have far reaching benefits. The long-term goal is to develop a simple, passive, self-regulating micro-structured surface technology for heat sinks used in consumer electronics and aircraft electronics.The ISS experiment design, development, and implementation will be pursued in conjunction with CASIS implementation partner TBE, leveraging the aerospace contractor's extensive flight experiment expertise. The specific objectives are three-fold: to verify lateral bubble motion observed in microgravity flight experiments aboard the ISS lab, to perform ground-based experiments and analysis to validate/ refine an analytical model, and to explore terrestrial applications. Sealed square cross-sectioned ampoules inserted into the PFMI will be reconfigured to accommodate a planar heated ratcheted surface. The ampoule design will be guided by terrestrial experiments in a modified open-ended channel facility. High-speed visualization and sensor measurements in ISS and terrestrial environments will be generated as a part of the project. These data can be used by computational experts in the heat transfer community as validation cases for numerical simulations of boiling. The data and video images obtained from ISS and terrestrial experiments will be disseminated on NASA's Physical Science Informatics (PSI) data repository for experiments performed on the ISS. Apart from providing an avenue for graduate student mentoring, the project will enable the participation of under-represented undergraduate students through the McNair scholar program at UCD and the Alabama Space Grant program at Auburn.