CAREER: Bridging Length Scales to Unlock the Mechanistic Interdependence of Phase Interface Dynamics and Heat Transfer in Pool Boiling Processes

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The process of boiling a liquid from a submerged heating element in a stagnant pool, known as "pool boiling", plays a critical role in the successful operation of power plants, refrigeration systems, manufacturing, food production, and many other endeavors that are vital to the sustenance and quality of human life. A major scientific barrier to achieving greater efficiencies in pool boiling processes is the limited understanding of the heat transfer mechanisms at the small length and time scales associated with the generation of individual vapor bubbles. In this project, an innovative approach to pool boiling experimentation will provide temperature, heat flux, and liquid-vapor phase interface information from beneath individual vapor bubbles. This project will provide better understanding of the underlying physical processes which can be used to improve pool boiling processes at larger scales. In coordination with efforts in the laboratory, this project also supports strategic experiential learning and outreach initiatives for K-12 and undergraduate students related to the fundamentals of thermal energy, with special emphasis on measuring how these activities affect student understanding. Through these initiatives, educators will gain valuable insight into how students from different backgrounds best learn about the thermal sciences, thereby improving student success and increasing participation in science, technology, engineering, and math (STEM) disciplines within both traditional and underrepresented groups.The overall scientific objective of this project is to obtain a deep understanding of the timing and relative importance of the various modes of heat transfer associated with bubble nucleation, growth, and departure for both single and coalesced bubble conditions. This is achieved via a family of microfabricated test devices with thermal- and phase interface-sensing features centered on one or more artificially created nucleation sites, with sensor outputs temporally coupled to a high-speed imaging system. This provides a means of unlocking key insights into the complex interplay between liquid, vapor, and solid during pool boiling processes including long-debated questions regarding the behavior and roles of the moving contact line, microscale contact angles, and microlayer behavior in nucleate boiling heat transfer. The versatility of this method allows it to be employed to study a wide range of boiling phenomena, regimes, conditions, and multiscale surface modifiers, thereby making for a valuable new set of capabilities that can provide a high level of productivity and benefit to the greater scientific community. This award is jointly funded by the Division of Chemical, Bioengineering, Environmental, and Transport Systems in the Directorate of Engineering and the Established Program to Stimulate Competitive Research in the Office of Integrative Activities.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.