Theory and Applications of Non-Equilibrium Thermodynamics

申请人的主要研究涉及开发精确的模型，用于模拟和理解微尺度系统中的过程，在微尺度系统中，非平衡程度很强，公认的流体动力学和热传递定律不再有效。这些强大的模拟工具提供了测量无法访问的重要过程细节，并最大限度地降低了原型和物理测试的成本。申请人在开发和应用来自微观描述的先进流动模型方面取得了出色的成功和认可，这些模型完善了流体动力学方程，并将有效性扩展到微观流动。精化的方程给出了有用的微观物理近似，并描述了所有有趣的输运机制。先进的冷却系统依赖于微观尺度上的蒸发冷却，因此必须在模型中包含对蒸发和冷凝现象的准确描述。虽然蒸发和冷凝是日常现象，但它们在微观尺度上的行为很难确定。例如，报告的水的蒸发系数的值分散在几个数量级上。分子模拟显示，肉眼看起来像是液体和蒸汽之间的尖锐界面，实际上是一个很小的区域，质量密度和其他性质在几个原子直径的距离内不断变化-变化很大，但不是很剧烈。申请人最近与同事和学生合作，着手开发和测试一套改进的流体动力学方程，描述液体和汽相以及用表面张力和界面电阻率分解的相界面。与分子模拟相比，新方程的求解效率明显提高。初步结果没有显示随机噪声，而是显示了非平衡界面的所有显著特征：显著偏离饱和压力；界面上的温度变化强烈，对应于温度跳跃；温度和密度变化的偏移；克努森过渡层，扩展了一些平均自由路径进入蒸汽；以及界面上速度的强烈变化，对应于滑移。拟议的研究计划将专注于模型的进一步发展，并利用它来全面了解影响非平衡相界面行为的因素。申请人的研究团队将继续建立在之前NSERC发现赠款资助计划的成功基础上，并利用新方程提供的速度和效率来探索从近平衡到强非平衡的广泛界面过程。申请者还将继续并扩展以前在非平衡热力学方面的工作，例如，理论对齐，以及在能源系统中的更广泛应用。

The applicant's main research concerns development of accurate models for simulation and understanding of processes in microscale systems, where the degree of nonequilibrium is strong and the well-established laws of fluid dynamics and heat transfer cease to be valid. These powerful simulation tools provide important process details that are not accessible to measurements, and minimize costs of prototyping and physical testing. The applicant had excellent success and recognition in developing and applying advanced flow models from the microscopic description, which refine the equations of fluid dynamics, and extend the validity towards microflows. The refined equations give useful approximations of the microscopic physics, and describe all interesting transport regimes. Advanced cooling systems rely on evaporative cooling on the microscale, hence an accurate description of evaporation and condensation phenomena must be included in the models. While evaporation and condensation are everyday phenomena, their behavior on the microscale is difficult to ascertain. For instance, the reported values for the evaporation coefficient of water scatter over several orders of magnitude. Molecular simulations reveal that what appears to the naked eye as a sharp interface between liquid and vapor, is in fact a small region in which mass density and other properties change continuously over the distance of few atomic diameters-the change is steep, but not sharp. In collaboration with co-workers and students, the applicant has recently embarked on the development and testing of a refined set of fluid dynamics equations which describe liquid and vapor phases as well as resolved phase interfaces with surface tension and interface resistivities. In comparison to molecular simulations, the new equations can be solved with significantly higher efficiency. Preliminary results do not show stochastic noise, and exhibit all the salient features of nonequilibrium interfaces: marked deviation from saturation pressures; strong variations of temperature across the interface, corresponding to temperature jumps; offset of temperature and density variation; Knudsen transition layers that extend some mean free paths into the vapor; and strong variations of velocity across the interface, corresponding to slip. The proposed research program will focus on the further development of the model, and its use to gain a comprehensive understanding of the factors that affect the behavior of nonequilibrium phase interfaces. The applicant's research team will continue to build on the success of the previous NSERC Discovery Grant funded program and exploit the speed and efficiency offered by the new equations to explore a wide range of interface processes, from near equilibrium to strong nonequilibrium. The applicant will also continue and extend previous work in nonequilibrium thermodynamics, e.g., on alignment of theories, and wider applications to energy systems.