CAREER: Ultrafast Localized Plasmas in Dense Fluids: From Fundamental Phase-Change Phenomena and Diagnostics to Efficient Heat and Mass Transport

能源和水是我们全球社会相互关联的基础。大多数热电能量转换和水净化技术的核心是沸腾、蒸发和冷凝等液-气相变过程。为了改进这些将热能转化为电能或提供清洁水的技术，相变现象必须既有效又可控。这个CAREER项目的目标是围绕在液体和蒸气中使用超快（20-100纳秒）和快速（0.1-10微秒）脉冲等离子体放电来探测、操纵或调节和增强沸腾和脱盐过程中遇到的液-气相变化过程中的传热和传质过程，将研究和教育结合起来。等离子体是物质的四种基本状态之一，是一种电离的高能量状态，具有独特的物理和光学特性（例如，考虑闪电）。通过控制等离子体在致密流体（如液态水）中的持续时间，可以最大限度地减少传热和电解造成的损失，并且可以控制等离子体对流体的影响。在这个项目中，等离子体将根据应用进行定制。超快或非热脉冲等离子体将被用于测量温度和物质，或在沸腾过程中局部扰动流体，而快速或热脉冲等离子体将被用于局部改变海水淡化过程中的流体状态。该项目还将利用这种跨学科的方法，向德克萨斯州布莱恩学院站地区从K-8年级到大学水平的不同学生群体传达有效的能源转换和水资源利用的重要性。这些努力的目标是参与、鼓励和支持对科学相关的高等教育的追求，并培养对我们的能源和水资源知情的、当前/未来的消费者。该项目的研究重点是致密流体中极短时间尺度脉冲非热和热等离子体放电与流体中快速能量沉积引起的热力学相变之间的相互作用。这些等离子体-流体相互作用将通过实验表征，从根本上研究流体中脉冲等离子体放电的能量/时间尺度控制所导致的高度瞬态液-气-固相变和物理化学过程。这些基础研究将用于开发新的光学诊断技术，以非热等离子体作为探针，在相变传热过程中原位测量物质浓度和气相温度。研究结果还将用于调整和加强沸腾传热和水净化过程中的热/质传递过程，通过非热等离子体和通过热等离子体进行盐水分离，按需和局部气泡成核。等离子体-流体相互作用框架将作为一种新的工具，吸引和介绍不同群体的早期学生了解能源转换和清洁水技术，并激发他们对科学和工程高等教育的兴趣。这些研究活动产生的知识也将积极纳入本科和研究生阶段的热流体科学课程，向学生介绍和培训最先进的能量转换和水净化技术。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。

Energy and water are the interconnected foundations of our global society. Central to most thermo-electric energy conversion and water purification technologies are liquid-vapor phase-change processes such as boiling, evaporation and condensation. To improve these technologies that convert thermal energy to electrical energy or provide clean water, phase-change phenomena must be both efficient and controllable. The goal of this CAREER project is to integrate research and education around the use of ultrafast (20-100 nanoseconds) and fast (0.1-10 microseconds) pulsed plasma discharges in liquids and vapors to probe, manipulate or tune and enhance heat and mass transfer processes during liquid-vapor phase change encountered in boiling and desalination processes. Plasma, one of the four fundamental states of matter, is an ionized and highly energetic state of matter with unique physical and optical properties (consider, for example, lightning). By controlling the duration of a plasma in a dense fluid, such as liquid water, losses via heat transfer and electrolysis may be minimized, and the impact of the plasma on the fluid may be controlled. In this project, the plasma will be tailored to the applications. Ultrafast or non-thermal pulsed plasmas will be sued to measure temperature and species or locally perturb a fluid during boiling, and fast or thermal pulsed plasmas will be used to locally alter the state of the fluid in desalination processes. The project will also leverage this cross-disciplinary approach to convey the importance of efficient energy conversion and water resource utilization to a diverse group of students, ranging from grades K-8 to the university level, in the Bryan-College Station area of Texas. The goals of these efforts are to engage, encourage, and support the pursuit of science-related higher education and to train informed, current/future consumers of our energy and water resources.The intellectual focus of this project is the interaction between extremely short timescale pulsed non-thermal and thermal plasma discharges in dense fluids and the thermodynamic phase transitions that result from rapid energy deposition in the fluid. These plasma-fluid interactions will be experimentally characterized to fundamentally study highly transient liquid-vapor-solid phase-change and the physicochemical processes resulting from the controlled energy/timescale of pulsed plasma discharges in fluids. The fundamental studies will be leveraged to develop novel optical diagnostic techniques to measure species concentration and vapor phase temperature in situ during phase-change heat transfer using a non-thermal plasma as the probe. The findings will also be used to tune and enhance heat/mass transfer processes during boiling heat transfer and water purification through on-demand and localized bubble nucleation via a non-thermal plasma and salt-water separations through a thermal plasma. The plasma-fluid interaction framework will be leveraged as a novel vehicle to engage and introduce a diverse group of early-age students to energy conversion and clean water technologies and to spark their interest in science and engineering higher-education. The knowledge resulting from these research activities will also be actively integrated into thermal-fluid sciences curricula at the undergraduate and graduate levels to introduce and train students in state-of-the-art energy conversion and water purification technologies.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.