Heat transfer processes in patterned and rough microchannels

任何实际的表面都是粗糙的，其粗糙程度可以扩展到几个尺度——从原子尺度到肉眼可见的尺度。提出的工作旨在调查这些特性的影响将如何改变流体（液体或气体）流动。例如，粗糙度可能与疏水性有关，与光滑表面相比，液体会以更大的速度（摩擦更小，需要的驱动力和能量更少）沿着表面掠过。对于被加热的液体，这样大的速度可能意味着更大的传热。然而，表面的粗糙度也由低导热系数的空气组成，这可能会降低传热的效率。通过这样的考虑，传热的量和速率可以通过控制粗糙度的量来灵敏地调节，并且将在实验和理论上研究，在这项工作中。由此获得的更深入的了解将产生对粗糙度、摩擦和热控制的基本科学见解。它还旨在将这些见解转化为微尺度管道和流动的即时设计，其应用范围从电子元件和设备的冷却到生物医学诊断。长期应用于提高流体流动、润滑和水过滤的效率，以减少界面上的阻力和热量传递。总体目标是获得多相流和粗糙表面上的传热的定量理解。该项目将研究纳米和微尺度表面效应在调节可测量的宏观特性（如温度、泵送功率和传热）方面的影响，并带来非常广泛的后果。从实验角度来看，该项目主要涉及：(a)图案/粗糙超疏水表面的开发和分析，以及(b)测量这些表面构成的通道流的速度分布和有效传热系数，并与理论模型验证相一致。它同时旨在开发和实施理论和数值工具来模拟有序和时空无序表面上的多相流动和传热。概率框架和随机流域的随机映射将用于模拟表面的固有变异性和由此产生的流。该研究将极大地扩展了从有序表面到随机纳米结构表面的热传输建模的技术水平。通过理论和实验的努力，热传递过程的调整将使更高效的微/纳米流体具有广泛的物理、化学和生物应用。

Any practical surface is rough, with the roughness extending over several scales - from the atomic scale to that observable to the naked eye. The proposed work aims to investigate how the influence of such characteristics would modify fluid (liquid or gas) flow. For example, roughness could be related to a hydrophobic aspect, where liquid would skim along the surface at a larger velocity (with less friction and needing less driving force and energy) compared to a smooth surface. For a heated liquid, such larger velocity may imply larger heat transfer. However, the roughness on the surface is also comprised of air of low thermal conductivity, which would be expected to reduce the efficacy of heat transfer. Through such considerations, the amount and rate of heat transfer may be sensitively regulated by controlling the amount of roughness and will be studied, experimentally and theoretically, in this work. The consequent greater understanding obtained would yield fundamental scientific insights into roughness, friction, and the control of heat. It is also aimed to translate such insights to the immediate design of microscale pipes and flows, with applications ranging from the cooling of electronic components and devices to biomedical diagnostics. Longer-term applications to enhancing the efficiency of fluid flow, lubrication, and water filtering, with respect to reducing drag and heat transfer across the interface are being considered. The overarching goal is to gain quantitative understanding of multiphase flow and heat transfer over rough surfaces. The project will investigate the influence of nano- and micro-scale surface effects in modulating measurable macroscale properties such as temperature, pumping power, and heat transfer, with very wide ranging consequences. From an experimental point, the project mainly involves the: (a) development and analysis of patterned/rough superhydrophobic surfaces, and (b) measurement of velocity profiles and effective heat transfer coefficients in such surface constituted channel flow, in concert with theoretical model validation. It is concurrently aimed to develop and implement the theoretical and numerical tools for modeling multiphase flow and heat transfer over ordered and spatiotemporally disordered surfaces. Probabilistic frameworks and stochastic mapping of random flow domains will be used to model the inherent variability of the surfaces and the resulting flows. The research would substantially extend the state of the art in thermal transport modeling involving ordered surfaces to random nanostructured surfaces. The tuning of thermal transport processes, considered through the theoretical and experimental efforts, would enable higher efficiency micro-/nano-fluidics with a wide range of physical, chemical, and biological applications.