EAGER: Uncovering the Physical Mechanism behind Flow Boiling Critical Heat Flux

能源、航空航天、国防、消费电子等行业能源利用率显著提高。目前使用空气或水流的冷却系统通常无法有效地提取热量并保持合理的工作温度。液体的沸腾是一种非常有效的冷却机制，但沸腾系统可以提取多少是有限制的，这是由临界热通量定义的。超过临界热流密度会导致发热系统或装置失效。这个项目的首要目标是理解临界热通量背后的物理学。这种理解可以用来避免沸腾系统中的故障。该项目的教育和推广目标是通过为凯斯西储大学的“创新导论”项目开发一个模块来补充研究活动，这是一个新的校园范围内更广泛影响战略的核心，为中学教育工作者提供应用核心科学概念来理解简单冷却系统的经验。计划在实验室演示池沸腾现象，以补充该模块的教学部分，重点关注自然系统中沸腾引起的相变。研究表明，流动中发生的流体动力汽液不稳定可以触发流动沸腾临界热流密度。然而，到目前为止，还没有对这种现象进行彻底的验证，以确定其背后的机制。在这个项目中，研究人员计划通过结合高速成像和粒子成像测速测量来探索流动沸腾过程中的界面流动动力学，从而对临界热通量背后的机制有一个基本的了解。利用获得的数据，将建立一个机制模型来预测临界热通量。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

Many industries including those in energy, aerospace, defense, and consumer electronics sectors are seeing a significant increase in energy utilization. Current cooling systems that use air or water flows are often incapable of extracting the heat effectively and maintaining reasonable operating temperatures. Boiling of liquids is a very effective cooling mechanism, but there is a limit on how much boiling systems can extract, defined by the critical heat flux. Exceeding the critical heat flux can cause a failure of the heat-generating system or device. The overarching goal of this project is the understand the physics behind the critical heat flux. This understanding can then be used to to avoid failure in boiling systems. The educational and outreach goal for the project is to complement the research activity by developing a module for Case Western Reserve University’s “Introduction to Innovation” program, the centerpiece of a new campus-wide broader impact strategy, to give middle school educators experience in applying core scientific concepts to understanding simple cooling systems. A lab demonstration of the pool boiling phenomena has been planned to supplement the teaching section of the module to focus on phase-transformation due to boiling in natural systems.It has been shown that flow boiling critical heat flux can be triggered by hydrodynamic liquid-vapor instabilities occurring in the flow. However, to date, no thorough validation of the phenomena has been performed to ascertain the mechanism behind it. In this project, the investigators plan to develop a fundamental understanding of the mechanism behind critical heat flux by exploring interfacial flow dynamics during flow boiling by using a combination of high-speed imaging and particle image velocimetry measurements. Using the data obtained, a mechanistic model will be developed to predict critical heat flux.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.