CAREER: Understanding thermal transport across phase-change interfaces via in situ micro-Raman thermography

在发电、微电子冷却、建筑物热控制等方面，利用蒸发、沸腾、冷凝等液相变化。在过去的十年里，纳米技术的进步使纳米工程设备具有优越的传热性能。虽然可以测量宏观尺度系统级的热性能，但了解微观尺度相变边界发生的情况对于设计下一代热器件是必要的。本研究的总体目标是开发一种可以直接探测相变区域的温度测量技术，并进一步了解纳米结构存在下液气相变热输运的微观机制。通过将实践项目纳入高中和本科教学，接待本科生研究人员和开发新的研究生课程，拟议的研究将融入教育和指导活动。此外，该项目计划从传热传质的角度研究传染病通过呼吸道飞沫传播，以扩大热流体工程对现实世界的影响。本研究旨在开发一种基于微拉曼光谱与热流体室界面的新型平台，以前所未有的精度和空间分辨率原位测量固液气接触线附近的温度。该平台允许人们(i)研究表面微纳米结构在促进相变界面热传递中的作用，（ii）开发多长度尺度结构以同时最大化传热系数和临界热流密度，以及（iii）通过详细的温度映射了解与高温梯度相关的相变过程。所提出的研究将弥合宏观热表征和精确的微尺度热测量之间的差距。通过这项工作获得的基本见解将导致高效的相变器件。此外，原位、局部温度测量方法将成为研究冷凝、结霜和沸腾等相变过程的通用平台，为相变传热的发展做出广泛贡献。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。

Liquid-vapor phase change including evaporation, boiling and condensation are utilized in power generation, cooling of micro-electronics, and thermal control of buildings. The advancement of nanotechnology over the last decade has enabled nanoengineered devices with superior heat transfer performance. Although the thermal performance at the macroscale system level can be measured, understanding what happens at the phase change boundary at the microscale is necessary to design the next-generation thermal devices. The overarching goal of this research is to develop a temperature measurement technique that can directly probe phase change region, and to further understand the microscopic mechanisms of liquid-vapor phase-change thermal transport in the presence of nanostructures. The proposed research will be integrated into education and mentoring activities by incorporating hands-on projects into high school and undergraduate teaching, hosting undergraduate researchers and developing new graduate courses. Furthermore, the project plans to broaden the real-world impact of thermo-fluids engineering by studying the transmission of infectious diseases through respiratory droplets from the perspective of heat and mass transfer.The proposed research aims to develop a novel platform, based on micro-Raman spectroscopy interfaced with a thermofluidic chamber, for in-situ measurement of temperature near the solid-liquid-vapor contact line with unprecedented accuracy and spatial resolution. This platform allows one to (i) investigate the role of surface micro and nanostructures in promoting the thermal transport across phase-change interfaces, (ii) develop multi-length-scale structures to maximize the heat transfer coefficient and the critical heat flux simultaneously, and (iii) understand phase change processes associated with high temperature gradients by detailed temperature mapping. The proposed research will bridge the gap between macroscopic thermal characterization and precise thermal measurement at the microscale. The fundamental insights gained through this work will lead to highly effective phase change devices. In addition, the in situ, local temperature measurement method will be a general platform to investigate phase change processes including condensation, frosting, and boiling, contributing broadly to the advancement of phase change heat transfer.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.