Collaborative Research: Scale-free continuum percolation of bubbles as a universal mechanism of the boiling crisis

沸腾换热是一种非常有效的散热过程，在电子冷却、化工处理、发电、暖通空调和水净化中发挥着关键作用。然而，沸腾很容易发生降解，即所谓的沸腾危机，这可能会导致冷却系统故障。了解这场沸腾危机对于开发和安全运行依赖于气-液两相冷却的核反应堆和计算机处理单元至关重要。尽管进行了数十年的研究，但引发沸腾危机的机制仍然不清楚，也存在争议。在这个项目中，基于沸腾过程与交通拥堵形成之间的类比，提出了一个新的随机模型。该项目旨在为热力社区提供一种沸腾换热的新视角。它还为研究生和本科生以及年轻的研究人员提供多学科的STEM培训机会。本项目将调查沸腾的危机作为气泡合并过程中的关键转变。基于四个基本沸腾参数：气泡等待时间和生长时间、气泡足迹半径和成核点密度的随机渗流模型将捕捉到这种不稳定性。在这四个参数的关键组合下，当所有气泡突然合并在一起时，沸腾的危机就会发生。这一假设最近在光滑的表面上得到了验证，在池水和流动沸腾条件下都是如此，在工程表面上也得到了初步的结果。在拟议的工作中，将通过分析不同表面和流体在不同压力和不同流动条件下的沸腾行为来检验该假设的普适性。该项目将通过新颖的沸腾实验来完成，这些实验结合了最先进的红外诊断和后处理算法，能够测量沸腾表面上随时间变化的温度和热流密度分布，以及其他沸腾换热参数。实验调查的结果将与热科学和工程界分享，以支持对其他模型的评估并刺激新模型的开发。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。

Boiling heat transfer is an exceptionally effective heat removal process and plays a critical role in electronics cooling, chemical processing, power generation, HVAC, and water purification. However, boiling is susceptible to a degradation, known as a boiling crisis, which may result in cooling system failures. Understanding this boiling crisis is key to the development and safe operations of nuclear reactors and computer processing units that rely on liquid-vapor two-phase cooling. Despite decades of research, the mechanism triggering a boiling crisis remains unclear and controversial. In this project, a new stochastic model is proposed based on the analogy between the boiling process and the formation of traffic jams. The project seeks to offers a novel perspective of boiling heat transfer to the thermal community. It also provides multidisciplinary STEM training opportunities for graduate and undergraduate students, as well as young researchers.This project will investigate boiling crises as a critical transition in the bubble coalescence process. The instability will be captured with a stochastic percolation model based on four fundamental boiling parameters: bubble wait time and growth time, bubble footprint radius, and nucleation site density. With a critical combination of these four parameters, the boiling crisis occurs when all the bubbles suddenly merge together. This hypothesis has recently been validated on smooth surfaces, in both pool and flow boiling conditions, as well as preliminary results on engineered surfaces. In the proposed work, the universality of the hypothesis will be tested by analyzing the boiling behavior of various surfaces and fluids, at different pressures, and under diverse flow conditions. The project will be accomplished through novel boiling experiments that combine state-of-the-art infrared diagnostics and post-processing algorithms, which enable measurements of time-dependent temperature and heat flux distributions on the boiling surface, as well as other boiling heat transfer parameters. The results of the experimental investigations will be shared with the thermal science and engineering community to support the evaluation of other models and stimulate the development of new ones.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.