ERI: Ultrafast Transiently Nucleated Laser Bubbles for Realistic Phenomenological Boiling Studies

核沸腾在发电、海水淡化、化学加工和热管理等主要工业中是一种极为重要的现象。然而，由于其固有的物理复杂性和热表面蒸汽泡形成的随机性，它仍然知之甚少，阻碍了有意义的性能增强。近年来，先进的高速光学和红外成像技术可用于实验研究气泡生长的动态和热行为。然而，问题在于，在大量随机形成和相互作用的气泡中，集中研究单个气泡生长事件在实验上存在困难。通过研究超快速微尺度液体-蒸汽转变的物理特性，该项目寻求开发一种基于激光的新技术，以产生与核沸腾中随机形成的气泡相同的热和生长特性的受控蒸汽气泡。这将使沸腾的突破性参数和现象学研究成为可能，可能导致对国家国防、基础设施和能源安全至关重要的许多热系统的大规模能源效率和吞吐量的提高。该项目还包括重要的教育和推广活动，包括对CSULB本科生和研究生的研究培训，开发基于网络的工程应用平台，以提高科学计算和编程技能，以及向当地高中和社区大学学生推广。本研究的目的是开发和表征一种新的基于激光的可控气泡产生技术，并阐明激光脉冲诱导固液界面均匀成核的物理原理。这种作为受控气泡人工成核场所的超快速非平衡成核机制，在实验和理论上都未得到很大程度的探索。本项目进行严格的实验研究和理论/CFD分析，以实现基于激光的现象-沸腾研究平台，填补近壁非平衡均匀成核的重大科学空白，具体目标有两个：(i)演示激光诱导人工气泡的产生并表征关键激光参数；（ii）通过参数成核实验和建模确定临界近壁均匀气泡成核温度。在实验方面，光学高速成像研究将使用聚焦激光装置和先进的池沸腾设备进行。理论分析和CFD模拟将用于模拟激光热点在成核过程中的热演化。研究结果将为建立近壁非平衡均相蒸汽成核理论奠定基础。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。

Nucleate boiling is a phenomenon of utmost importance in major industries such as power generation, desalination, chemical processing, and thermal management. However, it remains poorly understood due to its inherent physical complexity and the random nature of vapor bubble formation on hot surfaces, preventing meaningful performance enhancements. Advanced high-speed optical and infrared imaging techniques have recently become available to experimentally study the dynamic and thermal behavior of growing bubbles. The problem, however, is the experimental difficulty in focusing on an individual bubble growth event amidst a huge mass of randomly forming and mutually interacting bubbles. By studying the physics of ultra-fast microscale liquid-vapor transitions, this project seeks to develop a novel laser-based technique to generate a controlled vapor bubble that is identical in its thermal and growth characteristics to randomly forming bubbles in nucleate boiling. This will enable ground-breaking parametric and phenomenological studies in boiling, potentially leading to large scale energy efficiency and throughput improvements in many thermal systems critical for the nation’s defense, infrastructure, and energy security. The project also encompasses significant educational and outreach activities, including research training of diverse undergraduate and graduate students at CSULB, development of a web-based engineering applications platform to promote scientific computational and programming skills, and outreach to local high school and community college students.The goal of this research study is to develop and characterize a novel laser-based controlled bubble generation technique and to illuminate the physics underlying laser pulse-induced homogeneous nucleation at a solid-liquid interface. The mechanism of this ultra-fast non-equilibrium nucleation, which acts as an artificial nucleation site for the controlled bubble, has largely been unexplored, both experimentally and theoretically. This project undertakes rigorous experimental studies and theoretical/CFD analysis to implement the laser-based phenomenological-boiling-studies platform and fill significant scientific gaps in the understanding of near-wall non-equilibrium homogeneous nucleation in two specific aims: (i) Demonstrate laser-induced artificial bubble generation and characterize the key laser parameters and (ii) Identify the critical near-wall homogeneous bubble nucleation temperature using parametric nucleation experiments and modeling. On the experimental side, optical high-speed imaging studies will be performed using a focused-laser setup and an advanced pool boiling facility. Theoretical analysis and CFD simulations will be used to model the thermal evolution of the laser hotspot in nucleation. Results of this study will lay the groundwork for a new theory on near-wall non-equilibrium homogeneous vapor nucleation.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.