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

点击翻译按钮获取中文摘要

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.