CAREER: Gas-Liquid Interface Dynamics and Dissipation Mechanisms in Capillary-Scale Two-Phase Flow

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CBET-0748049AllenTwo-phase flow in large-scale systems has historically been important to the fields of hydrodynamics and heat transfer. Advances in MEMS analytical devices, microscale heat exchangers, space-based processing and thermal control technologies, and terrestrial-based technologies such as fuel cells have highlighted the need for improved understanding of gas-liquid flow with a strong capillary component. Attempts at developing universal flow regime maps for small scale systems have been unsuccessful due to the inability to properly account for the effects of capillary forces, dissipation due to menisci motion and gas-liquid interface interaction. The PI will conduct a systematic experimental and analytical investigation of two-phase flow at the capillary scale and develop engineering design tools. Educational opportunities for pre-college, undergraduate and graduate students are integrated throughout the research program. The first three overlapping research phases consists of qualitative experiments to study gas-liquid interface dynamics and development of a high-speed confocal microscopy technique. The second phase of this program focuses on quantitative studies utilizing the high-speed confocal microscopy technique for micro-Particle Image Velocimetry (micro-PIV) near dynamic gas-liquid interfaces; a region of flow not accessible with any currently available micro-PIV methods. The analytical and experimental studies of the second phase will isolate and quantify the effects of surface tension, interface curvature, interface shear, gas phase inertia and compressibility, hydrodynamic dissipation due to menisci motion and dynamic contact lines on the morphology of the two-phase flow through microchannels. All of these effects have been observed in capillary-scale two-phase flow, but not quantified. The third phase will construct and test predictive tools for design and development of advanced technologies and to improve water management strategies for more reliable fuel cell operation. The results of research will help in development of automotive fuel cells where inability to effectively manage the water produced by the hydrogen-oxygen reaction constitutes one of the major difficulties in mass deployment. Impacts of this research have an educational aspect and a societal aspect. Graduate and undergraduate student training is an important part of this work. Students will be recruited from under-represented groups through existing Michigan Tech educational partnerships. A key element of the educational aspect of this study is the tiered mentoring of graduate to undergraduate students and undergraduate to pre-college students where students learn through demonstration and instruction from other students. The societal impact will be most evident in advanced technology development; particularly with respect to alternative energy conversion technologies such as fuel cells. The results of this study will be a more thorough, quantitative understanding of two-phase flow in systems where capillary forces are important and application of this understanding to advance technology while developing student talent in the growing field of microscale devices and fuel cells.