Linking dynamics and equilibrium thermodynamics: entropy scaling and density scaling of siloxane mixtures and other working fluids for Carnot batteries

SPP中提出的自上而下的方法需要精确的热力学平衡和输运性质数据，才能实现高效率。在反设计中，理论上合理的描述这些特性的方程对于确定最佳工作流体和操作条件是必要的。输运性质的预测方程的发展仍然远远落后于平衡性质的发展，因此它是拟议项目的目标。事实上，平衡性质数据和预测方程的更好可用性使得探索输运和平衡热力学之间的联系变得引人注目。熵标度和密度标度，以同形理论为背景，将讨论纯流体和混合物的剪切粘度和热导率的建模。该项目的目标之一是详细阐述一种可靠的方法，并建议将熵缩放应用于传输属性建模。基于对硅氧烷及其混合物的研究，对Rosenfeld关于熵标度理论的开创性工作的可用修改进行了批判性评估。罗森菲尔德认为，输运性质，当按适当的物理尺寸缩放时，是剩余熵的单变量函数。该项目还将重点放在密度标度的理论和方法发展上，因为它与熵标度相反，不需要亥姆霍兹能量状态方程的可用性。申请人的准备工作表明，使用与流体有效硬度相关的恒定有效密度标度指数可以将密度标度的唯一变量转换为剩余熵的单变量函数。在这个意义上，提出了密度标度及其与熵标度的关系的研究。这将需要使用基于米氏势的模型流体和混合物，该模型允许排斥力相互作用的变化。作为一类真实的流体，硅氧烷化学家族，线性和循环，以及它们的混合物将被研究。化学族的选择将为研究模型参数和分子结构之间的联系提供可能性，这是逆向设计所必需的。在混合的情况下，重点将放在混合规则和高度不对称的混合物，其中单变量行为预计将被打破。通常，分子模拟技术将用于获得均匀分布的混合输运性质数据集以及剩余熵数据。该项目是SPP的一部分，包括与其他合作伙伴的高水平合作。它不仅限于开发输运性质标度方案，还包括根据其他SPP项目合作伙伴的具体需求提供平衡性质和研究其他流体。

The top-down methodology ambitioned in the SPP requires accurate data on thermodynamic equilibrium and transport properties if high efficiencies are to be achieved. In inverse design, theoretically sound equations describing these properties are necessary to identify optimal working fluids and operating conditions. The development of predictive equations for transport properties has remained well behind that of equilibrium properties, such that it is the objective of the proposed project. In fact, the better availability of equilibrium property data and predictive equations makes exploring the link between transport and equilibrium thermodynamics compelling. Entropy scaling and density scaling, having isomorph theory as a background, will be addressed for modeling the shear viscosity and thermal conductivity of pure fluids and mixtures. One of the goals of this project is the elaboration of a trustworthy methodology and recommendations for the application of entropy scaling to transport property modeling. A critical evaluation of the available modifications of Rosenfeld’s pioneering work on entropy scaling theory based on studies of the siloxanes and their mixtures will be performed. Rosenfeld suggested that transport properties, when scaled with the appropriate physical dimensions, are an univariate function of the residual entropy. This project also lays a focus on the theoretical and methodological development of density scaling, since it, contrary to entropy scaling, does not require the availability of a Helmholtz energy equation of state. Preparatory work of the applicant showed that the use of a constant effective density scaling exponent, related to the fluid’s effective hardness, can transform the unique variable of density scaling into a univariate function of residual entropy. In this sense, a study of density scaling and its relationship with entropy scaling is proposed. This will require the use of model fluids and mixtures, based on the Mie potential, which allows for variation of the repulsive interaction. As a class of real fluids, the siloxane chemical family, linear and cyclic, as well as mixtures thereof will be studied. The choice of a chemical family will offer the possibility to investigate the link between model parameters and molecular structure, which is required for inverse design. In case of mixtures, emphasis will be put to mixing rules and to highly asymmetric mixtures, where the univariate behavior is expected to break down. Generally, molecular simulation techniques will be employed to obtain evenly distributed hybrid transport property data sets as well as residual entropy data. This project, conceived as a part of the SPP, includes a high level of collaboration with other partners. It is not limited to the development of transport property scaling schemes, but also includes the supply of equilibrium properties and the study of other fluids according to the specific needs of other SPP project partners.