UNS: Detailed molecular-thermodynamic methods for high-precision calculation of condensation, criticality, and supercritical behaviors of fluids and fluid mixtures

UNS：用于高精度计算流体和流体混合物的冷凝、临界和超临界行为的详细分子热力学方法

• 批准号: 1510017
• 负责人: David Kofke
• 金额: $ 32.46万
• 依托单位: SUNY at Buffalo
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-06-15 至 2021-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1510017&HistoricalAwards=false
• 关键词: UNS; Detailed; molecular; thermodynamic; methods

#1510017Kofke, David A.Given a detailed mathematical description for how molecules interact, it is difficult to predict how a macroscopic material formed from those molecules will behave. Yet such a capability is extremely valuable, because it gives us a powerful means to understand, optimize and control the behavior of natural and engineered systems. The most reliable technique is to perform a molecular simulation, and observe what happens when many molecules are made to interact virtually, on a computer. This approach has some disadvantages though: it takes a lot of computer time, which limits the type of molecular models that can be used, and instead of producing an equation that can be manipulated, it yields data, like an experiment, that requires further processing to be useful. The work performed in this project takes a completely different approach to the problem. It proceeds via a methodical examination of how two molecules interact, then three, four, etc., and in this manner builds a theoretically-correct equation that describes the macroscopic behavior. The resulting formula can be even more accurate than molecular simulation, but it has different limitations, which pertain to the state conditions such as temperature and density where it is applied. The aim of this project is to understand and overcome these limitations, so that this "cluster integral" approach can take its place alongside molecular simulation as a robust and widely-used means for understanding and using materials for practical applications.This work proceeds in several mutually reinforcing directions: (1) refining and extending an important algorithm that appeared in the literature in 2013. This is used to better enable calculation of cluster integrals needed for the project; (2) exploring methods to estimate very high-order cluster integrals, and investigating their ability to identify the condensation binodal density; (3) developing and applying approximants that enforce known critical scaling. Evidence suggests that the critical singularity hampers application of the virial series for a sizeable range of conditions in the vicinity of the critical point. Analytic treatment of the singular behavior via an approximant enables the virial series to locate the vapor-liquid critical point accurately, while providing a greatly improved equation of state for the surrounding region; (4) examining cluster series in relation to the Joule-Thomson effect; (5) applying the methods to fluid systems of practical interest.The impact of this research and related activities will be felt in many ways. First, the tools and understanding developed here can aid design and operation of many technological processes, allowing manufacturing and other commercial activities to be performed more safely, with lower cost, less energy usage, and reduced environmental impact. Educational tools will be produced relating to the topics studied here, and open-source software for implementing the methods we develop will be disseminated online. Finally, the ideas underlying this research will be introduced into curricula at the undergraduate and graduate levels, as well as part of an annual 2-week workshop for high-school students.

#1510017Kofke，David A.给出分子如何相互作用的详细数学描述，很难预测由这些分子形成的宏观材料将如何表现。然而，这种能力非常有价值，因为它为我们提供了理解、优化和控制自然和工程系统行为的强大手段。最可靠的技术是进行分子模拟，并观察当许多分子在计算机上虚拟相互作用时会发生什么。但这种方法有一些缺点：它需要大量的计算机时间，这限制了可以使用的分子模型的类型，并且它产生的数据不是可以操作的方程，而是像实验一样需要进一步处理变得有用。 该项目中执行的工作采用了完全不同的方法来解决问题。它通过系统地检查两个分子如何相互作用，然后是三个、四个等如何相互作用，并以这种方式建立一个描述宏观行为的理论上正确的方程。所得公式甚至可以比分子模拟更准确，但它有不同的局限性，这与应用它的状态条件（例如温度和密度）有关。该项目的目的是理解并克服这些限制，以便这种“簇积分”方法可以与分子模拟一起作为一种强大且广泛使用的方法来理解和使用材料进行实际应用。这项工作在几个方面进行相互促进的方向：（1）完善和扩展2013年文献中出现的一个重要算法。这用于更好地计算项目所需的簇积分； （2）探索估计极高阶簇积分的方法，并研究其识别凝聚双节密度的能力； (3) 开发和应用强制已知临界缩放的近似方法。有证据表明，临界奇点阻碍了维里级数在临界点附近相当大范围的条件下的应用。通过近似法对奇异行为进行解析处理，使维里级数能够准确定位汽液临界点，同时为周围区域提供大大改进的状态方程； (4) 检查与焦耳-汤姆逊效应相关的簇序列； (5) 将这些方法应用于实际感兴趣的流体系统。这项研究和相关活动的影响将通过多种方式感受到。首先，这里开发的工具和理解可以帮助许多技术流程的设计和操作，使制造和其他商业活动能够更安全地进行，同时降低成本、减少能源消耗并减少对环境的影响。将制作与此处研究的主题相关的教育工具，并且用于实施我们开发的方法的开源软件将在网上传播。最后，这项研究的想法将被引入本科生和研究生课程，以及每年为高中生举办的为期两周的研讨会的一部分。