In this work, we describe how to efficiently and reliably calculate p‐x and T‐x diagrams for binary mixtures of fluids. The method is based on the use of the Helmholtz energy density as the fundamental thermodynamic potential. Through the use of temperature and molar concentrations of the components as the independent variables, differential relationships can be constructed along the phase envelope surface, and this system of differential equations is then integrated to construct isotherms and isobars cutting through the phase envelope. The use of the Helmholtz energy density as the fundamental potential allows several models to be considered in this formalism, including cubic equations of state (Peng‐Robinson, GC‐VTPR, etc.) as well as high‐accuracy multifluid equations of state (the so‐called GERG mixture model). Examples of each class are presented, demonstrating the flexibility of this method. Source code, examples, and comprehensive analytic derivatives are provided in the Supporting Information. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2745–2757, 2018

中文翻译：

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从等容热力学上构造二元混合物p-x和T-x图

在这项工作中，我们描述了如何有效和可靠地计算流体的二元混合物的p-x和T-x图。该方法基于使用亥姆霍兹能量密度作为基本热力学势。通过使用组分的温度和摩尔浓度作为自变量，可以沿相包络线表面建立微分关系，然后将该微分方程组集成以构造穿过相包络线的等温线和等压线。使用亥姆霍兹能量密度作为基本势能可以在此形式主义中考虑多个模型，包括立方状态方程（Peng-Robinson，GC-VTPR等）以及高精度多流体状态方程（所谓的GERG混合模型）。给出了每个类的示例，证明了该方法的灵活性。支持信息中提供了源代码，示例和全面的分析派生工具。©2018美国化学工程师学会AIChE J，64：2745–2757，2018