Enhanced Flow Boiling Heat Transfer at Microscale for Stable, High Heat Flux Removal

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CBET-1236062PI: KandlikarHigh heat flux removal while limiting the substrate temperature is critical in electronics cooling application. Current processor cooling demands are seen to reach a heat flux of 1 kW/cm2 while the device surface temperature needs to be low enough to keep the junction temperatures below 85 °C within the IC chip. Flow boiling in microchannels has been identified as a potential cooling technique to meet this cooling demand. However, the boiling instability and poor heat transfer performance during flow boiling in microchannels have been major impediments in realizing the desired cooling performance.The project effort is directed specifically at developing a stable, high performance flow boiling system to meet the current electronics cooling demands. This will be accomplished by a novel open microchannel design with tapered manifolds. The open microchannel design provides a low resistance pathway for vapor while the liquid remains in contact with the substrate providing efficient cooling due nucleate and/or convective boiling. Further enhancements in heat transfer coefficient and critical heat flux (maximum possible heat flux under safe operation) will be achieved by adding offset strip-fins and nanowires respectively on the substrate. The tapered manifold provides an effective way to eliminate the flow boiling instability. These concepts have been validated in the preliminary experiments in the PI?s lab. The focus of the project will be to understand the basic mechanism of flow boiling in this configuration and significantly improve the heat transfer performance with water. In addition, FC87 and ethanol will also be investigated as working fluids. FC87 is a dielectric fluid that can be directly used in electronics cooling application. Ethanol is also a dielectric fluid and has a better heat transfer performance compared to FC87. Although ethanol is flammable, its superior performance may be weighed against the precautions needed in designing safe cooling systems. The work will be done by graduate and undergraduate students who will gain hand-on experience on conducting advanced research on microscale transport processes. The major outcomes of the project will be developing a novel high heat flux removal system, understanding the basic heat transfer mechanisms during flow boiling at microscale, and educating undergraduate and graduate students. In addition, the students and PI working on the project will open interactions with area middle school students. They will be introduced to the emerging scientific areas including advanced heat transfer concepts, nanostructure development and research endeavors in quest of overcoming scientific barriers. Student from a local city school are scheduled to visit RIT once every week to interact with graduate students and learn from simulated projects that will be directed towards mimicking some of the key aspects of the planned research. The project will also be showcased to female students from high schools during their visits organized by WE (Woman in Engineering) volunteers at RIT.