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

广泛的地面研究已经进行了七十多年，以开发，测试和验证预测理论的流动沸腾和冷凝，因为它们发生在各种应用中的石油化工，制药，生物化学，核和冶金工业。一旦沸腾的气泡在加热的表面上形成，它很快就变得足够大，以脱离成核位置并与流动的流体一起移动。沸腾气泡的演变取决于惯性力、毛细力、阻力提升流体动力学力和浮力之间的微妙平衡。测量气泡运动时的一个小误差会导致实验数据解释的很大不确定性。 严格的测试和验证理论的两相流在个别气泡水平仍然是一个长期的挑战。通过消除强浮力效应，国际空间站（ISS）流动沸腾和冷凝实验（FBCE）硬件上的长时间微重力实验提供了一个独特的机会，可以研究毛细管力和水动力在流动流体和冷凝膜中气泡生长和合并中的作用。该项目团队还将参与教育计划，利用空间主题，通过将我们的项目工作纳入课程计划和实验室工作，以提高STEM的兴趣和技能，使大学和高中学生受益。所提出的努力旨在量化的流场，温度场和相分布之间的相互作用，在流动沸腾和冷凝的瞬态和不稳定的条件下，在没有重力。实验将涉及设置国际空间站FBCE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。重点是强制瞬变和两相流的不稳定性，并使用数值技术模拟系统性能。最终的目标是看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，则确定理论中缺少了什么，以便更好地匹配实验数据。项目团队将使用图像分析技术检查气泡动力学的细节，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组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，并加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，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

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.