Investigation of Nucleate Boiling Mechanisms using 3D Transient Temperature Mapping

纳米技术和微电子技术的快速发展对电气系统中紧密受限区域释放的极端热负荷的热管理提出了重大挑战。利用与气泡生长相关联的沸腾传热可能是电气系统的最有效的冷却方法之一，因为在从水到蒸汽的相变期间大量的热移除。尽管显着提高散热速率，许多问题仍然存在关于气泡生长机制的基本原理，增强散热的主要来源。该项目的目标是开发一种气泡生长的机械模型，以减少传热强化试验失败的风险。这将为下一代冷却系统提供系统化的设计路线，同时节省时间和金钱。该项目将研究活动与教育目标相结合，例如为代表性不足的少数民族和女性研究生和本科生提供实践研究经验。本计画的研究目标是精确量测成长气泡周围的局部液体温度分布，以帮助更好地解释气泡成长的热质传递。微层中的局部流体温度由全内反射测温法询问，而在热边界层中的液体-蒸汽界面附近的流体温度由双示踪剂激光诱导荧光测温法测量。为了捕捉瞬态温度分布，这两种技术都与高速成像相结合。瞬态流体温度数据被用来量化的时间分辨热通量的质量传递附近的成长气泡。全面的三维温度信息也被用来验证现有的理论和实验热传输模型。该项目在科学上具有重要意义，因为它阐明了气泡快速增长的主要传热模式，因此提供了可靠的方法来设计表面和流体特性，以增强传热，而无需试错过程。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

The rapid advancement of nanotechnology and microelectronics poses significant challenges to the thermal management of extreme heat loads discharged from tightly confined areas in electrical systems. Harnessing boiling heat transfer associated with bubble growth is perhaps one of the most efficient cooling methodologies for electrical systems due to the large amount of heat removal during the phase change from water to vapor. Despite significant enhancements in heat removal rates, numerous questions remain regarding the fundamentals of bubble growth mechanisms, a major source of enhanced heat dissipation. The project goal is to develop a mechanistic model for bubble growth that lessens the risk of failure in trial-and-error tests for heat transfer enhancement. This will, in turn, provide a systematic design route for next-generation cooling systems while saving time and money. This project integrates research activities with educational goals such as offering underrepresented minority and female graduate and undergraduate students with hands-on research experiences. The research objective of this project is to accurately measure local liquid temperature distributions surrounding a growing bubble that help better explain the heat and mass transfer to bubble growth. Local fluid temperatures in the microlayer are interrogated by total internal reflection thermometry while fluid temperatures in the thermal boundary layer near the liquid-vapor interface are measured by dual-tracer laser-induced fluorescence thermometry. To capture transient temperature distributions, both techniques are combined with high-speed imaging. The transient fluid temperature data are used to quantify time-resolved heat fluxes contributing to mass transfer near the growing bubble. Comprehensive 3D temperature information is also used to validate the existing theoretical and experimental thermal transport models. This project is scientifically significant in that it illuminates the dominant heat transfer mode for fast bubble growth and therefore provides reliable methodologies to engineer surface and fluid properties for enhanced heat transfer without a trial-and-error process.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.