Theory and Applications of Non-Equilibrium Thermodynamics

非平衡热力学理论与应用

• 批准号: RGPIN-2022-03188
• 负责人: Struchtrup, Henning
• 金额: $ 4.01万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=760286
• 关键词: Theory; Applications; Non; Equilibrium; Thermodynamics

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.

申请人的主要研究涉及开发用于模拟和理解微尺度系统过程的精确模型，其中不平衡程度很强，流体动力学和热传递的既定定律不再有效。这些强大的仿真工具提供了重要的过程细节，这些细节是无法测量的，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从微观描述的先进流动模型方面取得了卓越的成就和认可，这些模型改进了流体动力学方程，并将其有效性扩展到微观流动。精炼的方程给出了微观物理的有用近似，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。虽然蒸发和凝结是日常现象，但它们在微观尺度上的行为是难以确定的。例如，报告的水的蒸发系数值分散在几个数量级上。分子模拟显示，在肉眼看来是液体和蒸汽之间的一个明显的界面，实际上是一个很小的区域，在这个区域内，质量密度和其他性质在几个原子直径的距离上不断变化——变化是陡峭的，但并不明显。在与同事和学生的合作下，申请人最近开始开发和测试一套精细的流体动力学方程，该方程描述了液体和蒸汽相，以及具有表面张力和界面电阻率的分解相界面。与分子模拟相比，新方程的求解效率显著提高。初步结果不显示随机噪声，并表现出非平衡界面的所有显著特征：明显偏离饱和压力；界面上温度的强烈变化，对应于温度的跳跃；温度和密度变化的偏移；克努森过渡层将一些平均自由路径延伸到蒸汽中；并且在界面上的速度变化很大，对应于滑移。提出的研究计划将集中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以前NSERC发现资助项目的成功基础上，并利用新方程提供的速度和效率来探索从接近平衡到强非平衡的广泛界面过程。申请人还将继续和扩展以前在非平衡热力学方面的工作，例如，理论的一致性，以及在能源系统中的更广泛应用。