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

CBET-1403657不断增加的热量已经成为许多电子和能源应用的进步和有效运行的障碍，例如功率和RF电子，高性能计算机，固态激光器和聚光太阳能电池。液体冷却过程被认为是这些应用的热管理的补救措施。微通道中的相变液体冷却过程，特别是受到了极大的关注。近二十年来，科学界的主要焦点一直是提高微通道散热器中的沸腾传热系数。然而，一个主要的障碍一直是相对有限的理解的传输特性，这是由相关的困难，诊断微通道中的界面行为。这些知识对于推进紧凑和高性能两相流散热器的科学和技术是必不可少的。本研究的目的是利用一种新的测量方法来了解微通道内流动沸腾中不同微尺度传热机制的物理特性，并测量它们对整个表面传热的相对贡献。推进这一领域的科学认识和工程实践需要实验能力的基本界面过程的表征。此外，相变传热控制的变革性改进可能来自新的机械模型的开发，以及来自实验技术的灵感和验证，这些实验技术可以在相关的长度和时间尺度上以足够的灵敏度探测温度和热通量。所提出的方法涉及在微通道中的流体-固体界面处的热场（温度和热通量）的高分辨率测量。所提出的测量方法的独特之处是实施的复合墙与嵌入式微传感器，使表面热通量被确定。热场测量与气泡的高速成像以及汽相和固相之间形成的液膜厚度同步。采用激光干涉法测量液膜厚度。将进行实验研究，以解释流动沸腾在微通道中的传热机制，评估突出的机械两相微通道模型的准确性，并了解表面的微和纳米结构的界面传输事件和流动沸腾特性的作用。

CBET-1403657The 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.