CAREER: Active Cooling of Extreme Heat Fluxes via Transient Fluid Flow and Evaporation in Liquid Thin-films

液体薄膜中瞬态流体流动和蒸发对极端热通量的主动冷却本项目是一项关于液体界面上瞬态热量和质量传递的研究和教育项目。尖端技术的瞬态热流可以超过50 MW/m2，这几乎是太阳辐射的热流。为了控制极端的热负荷，最先进的技术是在微纳米结构的散热器上煮沸和蒸发液体冷却剂。然而，现代冷却技术无法控制瞬态条件下的极端热通量。由于开/关设备操作或间歇性暴露在极端环境中，热流体瞬变会导致热流体行为高度不稳定，最终使液冷设备面临热失控（即设备温度快速、不受控制地升高）导致灾难性故障的危险。一个综合的研究和教育计划，以扩大机构课程，培训和教育在现代技术的过渡过程。一个独特的夏季研讨会和学术推广活动将利用几个成熟的STEM项目，促进许多教育元素的使用，包括课堂项目、演示、视频和关于瞬态运行和非平衡过程的讨论。技术目标是确定瞬态条件下蒸发传热的基本极限。主要的方法是测试蒸发薄膜的传热系数（HTC）是否符合气体动力学理论的预测。该项目将结合时间分辨光学诊断来表征瞬态HTC及其对蒸气质量、过热、加热器表面结构和化学变化等相关因素的依赖。这些瞬态研究与稳态和准稳态实验相结合，有望揭示以前未暴露的关键传热过程，增加对现代技术中瞬态过程的认识和知识，这对可再生能源、先进计算和纳米技术的新思想至关重要。

Active Cooling of Extreme Heat Fluxes via Transient Fluid Flow and Evaporation in Liquid Thin-filmsThis project entails a research and educational program on transient heat and mass transport at liquid interfaces. Transient heat fluxes in cutting-edge technologies can exceed 50 MW/m2, which is nearly the heat flux radiated by the Sun. To manage extreme thermal loads, the State-of-the-Art is to boil and evaporate liquid coolants on micro- and nano-structured heat sinks. However, modern cooling techniques cannot manage extreme heat fluxes under transient conditions. Thermo-fluid transients due to on/off device operation or intermittent exposure to an extreme environment result in highly unstable thermo-fluid behavior, ultimately placing a liquid-cooled device in danger of catastrophic failure via thermal runaway -- i.e., a rapid, uncontrolled increase in device temperature.An integrated research-and-education program is pursued to broaden the institutional curriculum, training, and education on transient processes in modern technologies. A unique summer workshop and academic outreach activities will tap into several well-established STEM programs, facilitating the use of many educational elements -- including in-class projects, demos, videos, and discussions on transient operation and non-equilibrium processes. The technical objective is to identify the fundamental limits of evaporative heat transfer under transient conditions. The main approach is to test if the heat transfer coefficient (HTC) of evaporating thin-films follows the predictions of the kinetic theory of gases. The project will incorporate a combination of time-resolved optical diagnostics to characterize the transient HTC and its dependence on interrelated factors such as vapor quality, superheat, and changes in heater surface structure and chemistry. These transient investigations coupled with steady-state and quasi-steady experiments are expected to reveal previously unexposed key heat transfer processes, increasing both the awareness and knowledge of transient processes in modern technologies, which are vital for new ideas in renewable energy, advanced computing, and nanotechnology.