Collaborative Research: ISS: GOALI: Transients and Instabilities in Flow Boiling and Condensation Under Microgravity

七十多年来，人们进行了广泛的陆地研究，以开发、测试和验证流动沸腾和冷凝的预测理论，因为它们发生在石化、制药、生化、核能和冶金行业的各种应用中。一旦沸腾的气泡在加热的表面上形成，它很快就会变得足够大，足以从成核位置分离出来，并与流动的液体一起移动。沸腾气泡的演化是由惯性力、毛细气体力、阻力和升力流体动力以及浮力之间的微妙平衡决定的。测量气泡运动时的微小误差可能会导致对实验数据的解释产生很大的不确定性。在单个气泡水平上对两相流理论进行严格的测试和验证仍然是一个长期的挑战。通过消除强烈的浮力效应，国际空间站(ISS)流动沸腾和冷凝实验(FBCE)硬件上的长期微重力实验提供了一个独特的机会来研究毛细管力和流体动力在流动流体和冷凝膜中气泡生长和合并中的作用。项目团队还将参与利用空间主题提高对STEM的兴趣和技能的教育项目，方法是将我们的项目工作纳入教案和实验室工作，使大学生和高中生受益。这项工作旨在量化流动沸腾和冷凝在瞬变和不稳定条件下的流动沸腾和凝结中的流场、温度场和相分布之间的相互作用。实验将包括设置ISS FBCE的操作参数，然后记录系统内的压力和温度响应，并对两相流进行成像。重点是在两相流中强迫瞬变和不稳定性，并使用数值技术来模拟系统性能。最终目标是看沸腾和冷凝的理论预测是否与微重力下的测量结果相匹配，如果不匹配，则确定理论中哪些方面需要更好地与实验数据相匹配。项目团队将使用图像分析技术检查气泡动力学的精细细节，仔细检查两相流中的密度波振荡，并将其与系统中机械和热部件产生的温度和压降振荡相关联。机器学习技术将使用微重力实验数据来测试和验证相变流体流动的理论预测模型，并增强陆地和重力无关应用中流动沸腾和冷凝设备的设计指南。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。

Extensive terrestrial studies have been conducted for over seventy years to develop, test and validate predictive theories for flow boiling and condensation as they occur in various applications in the petrochemical, pharmaceutical, biochemical, nuclear, and metallurgical industries. Once a boiling bubble forms on a heated surface, it soon grows large enough to detach from the nucleation site and travel with the flowing fluid. Evolution of boiling bubbles is governed by a delicate balance between the inertial, capillary, drag & lift hydrodynamic, and buoyancy forces. A small inaccuracy in measuring the bubble motion can lead to a large uncertainty in the interpretation of experimental data. Rigorous testing and validation of theories for two-phase flows at the individual bubble level remains a longstanding challenge. By eliminating strong buoyancy effects, long duration microgravity experimentation on the International Space Station's (ISS) Flow Boiling and Condensation Experiment (FBCE) Hardware offers a unique opportunity to study the role of capillary and hydrodynamic forces in the bubble growth and coalescence in a flowing fluid and condensate film. The project team will also participate in educational programs that use space themes to improve interest and skills in STEM by incorporating our project work into lesson plans and laboratory work for the benefit of college and high-school students. The proposed effort seeks to quantify the interactions between the flow field, temperature field, and phase distributions in flow boiling and condensation under transient and unstable conditions in the absence of gravity. Experiments will involve setting the ISS FBCE operating parameters and then recording the pressure and temperature responses within the system and imaging the two-phase flow. The focus is to force transients and instabilities in two-phase flows and to simulate system performance using numerical techniques. The ultimate goal is to see if theoretical predictions for boiling and condensation match up with the measurements in microgravity, and if not, to determine what is missing in the theories that is required to better match the experimental data. The project team will inspect the fine details of bubble dynamics using image analysis techniques, scrutinize the density-wave oscillations in two-phase flows, and correlate those with temperature and pressure-drop oscillations generated by the mechanical and thermal components in the system. Machine learning techniques will use microgravity experimental data to test and validate theoretical predictions models for phase-change fluid flows and enhance guidelines for the design of flow boiling and condensation equipment in terrestrial and gravity-independent applications.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.