Probing interfacial phase-change transport events in flow boiling on micro- and nanotextured surfaces

University Of Florida, Gainesville FL

Investigators

Abstract

CBET-1403657 The ever-increasing generation of heat has become an impediment to advancements and the efficient operation of many electronics and energy applications, such as power and RF electronics, high-performance computers, solid-state lasers, and concentrated solar cells. The liquid-cooling process has been considered a remedy for the thermal management of these applications. The phase-change liquid-cooling process in microchannels, in particular, has received significant attention. A main focus of the scientific community for nearly two decades has been to enhance the boiling heat-transfer coefficient in microchannel heat sinks. However, a major obstacle has been the relatively limited understanding of transport characteristics, which is caused by difficulties related to diagnosing interfacial behavior in microchannels. Such knowledge is essential to advancing the science and technology of compact and high performance two-phase flow heat sinks. The objective of this study is to use a new measurement approach to understand the physics of different microscale heat transfer mechanisms involved in flow boiling in microchannels. The objective of this research is to utilize a new measurement approach to understand the physics of different microscale heat transfer mechanisms involved in flow boiling in microchannels and to measure their relative contributions to the overall surface heat transfer. Advancing both scientific understanding and engineering practice in this field requires experimental capabilities for characterization of the underlying interfacial processes. Furthermore, transformative improvements in the control of phase change heat transfer may come from the development of new mechanistic models, with inspiration and validation from experimental techniques that can probe temperature and heat flux with sufficient sensitivity over the relevant length and time scales. The proposed approach involves a high-resolution measurement of the thermal field (temperature and heat flux) at the fluid-solid interface in microchannels. The unique aspect of the proposed measurement approach is the implementation of a composite wall with embedded micro-sensors that allow the surface heat flux to be determined. The thermal field measurements are synchronized with the high-speed imaging of bubbles as well as the thickness of the liquid film formed between the vapor and solid phases. The laser interferometry method is utilized in measuring the liquid film thickness. Experimental studies will be conducted to explain the mechanisms of heat transfer in flow boiling in microchannels, evaluate the accuracy of prominent mechanistic two-phase microchannel models, and understand the role of surface micro- and nanostructures on the interfacial transport events and flow boiling characteristics.