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

CBET-1403657不断增长的发热量已经成为许多电子和能源应用的进步和高效运行的障碍，例如功率和射频电子、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对这些应用的热管理的一种补救方法。尤其是微通道中的相变液体冷却过程受到了极大的关注。近二十年来，科学界的一个主要焦点一直是提高微通道散热器中的沸腾换热系数。然而，一个主要的障碍是对传输特性的相对有限的了解，这是由于与诊断微通道中的界面行为有关的困难造成的。这些知识对于推进紧凑型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理解微通道内流动沸腾所涉及的不同微尺度换热机制的物理性质。本研究的目的是利用一种新的测量方法来理解微通道内流动沸腾所涉及的不同微尺度换热机制的物理性质，并测量它们对整个表面换热的相对贡献。推动这一领域的科学理解和工程实践都需要表征潜在界面过程的实验能力。此外，在实验技术的启发和验证下，相变热传递控制的变革性改进可能来自新机制模型的开发，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。该方法包括对微通道中流固界面的热场(温度和热流密度)进行高分辨率测量。所提出的测量方法的独特之处在于实施了一种带有嵌入式微型传感器的复合墙，该传感器允许确定表面热流。热场测量与气泡的高速成像以及在汽相和固相之间形成的液膜的厚度同步。采用激光干涉法测量液膜厚度。实验研究将解释微通道内流动沸腾的换热机理，评价主要的两相微通道力学模型的准确性，并了解表面微结构和纳米结构对界面传输事件和流动沸腾特性的影响。

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.