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

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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.