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

包括能源、航空航天、国防、消费电子等在内的许多行业的能源利用率都有显著提高。目前使用空气或水流的冷却系统往往不能有效地提取热量并保持合理的运行温度。液体沸腾是一种非常有效的冷却机制，但沸腾系统可以提取的量是有限制的，由临界热通量定义。超过临界热流密度可能会导致制热系统或设备发生故障。这个项目的首要目标是理解临界热流背后的物理原理。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，该项目是一项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了解简单冷却系统的经验。为了补充本单元的教学部分，计划对池沸腾现象进行实验室演示，以关注自然系统中沸腾引起的相变。研究表明，流动沸腾的临界热流密度可以由流动中发生的流体动力气液不稳定性触发。然而，到目前为止，还没有对这些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图像测速测量来探索流动沸腾过程中的界面流动动力学，从而对临界热流密度背后的机理有一个基本的了解。利用获得的数据，将开发一个预测临界热流的机械模型。这一奖项反映了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。

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.