Development of a novel method to investigate the dew line of binary mixtures using a modified two-sinker densimeter

为了了解流体混合物的相行为，并开发精确描述液体和蒸汽之间相界面的模型，准确的实验数据是必不可少的。这种模型对研究和工业越来越重要，例如在天然气加工和碳捕获和储存领域。根据实验数据，很难准确确定将均相汽相区域与非均相两相区域分开的露线。由此导致的准确数据的缺乏阻碍了理论模型的重大改进。在此背景下，本项目的主要目标是研究一种精确测量二元混合物露线的新技术。使用的仪器是美国国家标准与技术研究所的高精度双沉降式密度计。之所以选择二元混合物，是因为多组分混合物的最新模型仅根据组成的二元对进行拟合。在第一组实验中，我们打算测量选定二元混合物在不同压力下的露点温度。此外，还将研究混合吸附和预凝效果。有了第一个结果，就有可能验证应用技术测量露点温度的适用性。在第二组实验中，将对使用的双沉降器密度计进行改进，集成一对新的沉降器，该沉降器专门设计用于改进露点温度测量的特殊目的的技术。与原来的沉降器相比，新的沉降器将具有相同的质量、相同的体积但不同的表面特征；这将允许定量确定吸附在沉降器上的样品的质量。第二个实验数据集将包括与第一个数据集相同的测量点。这将允许检查使用一对特殊沉降器的想法，并做出第一次不确定性估计。这两组测量都将提供有关双沉降式密度计作为精确露点仪器的应用的全新信息。此外，这项工作将作为在波鸿鲁尔大学热力学教席上精确测量热物理性质的小组内未来研究的介绍性工作。因此，应对露线热力性质数据的测量进行全面的研究。

To understand the phase behavior of fluid mixtures and to develop models that precisely describe the phase boundary between liquid and vapor, accurate experimental data are essential. Such models are of increasing importance for research and industry, for example in the fields of natural gas processing and carbon capture and storage. With regard to experimental data, the dew line, separating the homogeneous vapor region from the heterogeneous two phase region, is very difficult to determine accurately. The resulting lack of accurate data obstructs a significant improvement of the theoretical models. Against this background the major objective of this project is to investigate a new technique for accurately measuring the dew line of binary mixtures. The instrument to be used is the highly accurate two-sinker densimeter of the National Institute of Standards and Technology. Binary mixtures are chosen because state of the art models for multicomponent mixtures are only fitted in terms of the constituent binary pairs. In a first set of experiments we intend to measure dew-point temperatures at different pressures of selected binary mixtures. Confounding adsorption and pre-condensation effects will be studied as well. With the first results it will be possible to verify the suitability of the applied technique for the measurement of dew-point temperatures. For a second set of experiments the two-sinker densimeter utilized will be modified by integrating a new pair of sinkers specifically designed to improve the technique for the special purpose of measuring dew-point temperatures. In contrast to the original sinkers, the new ones will be of same mass, same volume but different surface characteristics; this will allow a quantitative determination of the mass of sample adsorbed onto the sinker. The second experimental data set will include the same measurement points as the first data set. This will allow to check the idea of using a special pair of sinkers and to make a first uncertainty estimate. Both sets of measurements will provide completely new information about the application of a two-sinker densimeter as an accurate dew-point instrument. Moreover, this work will serve as introductory work for future research within the group for the accurate measurement of thermophysical properties at the chair of thermodynamics of Ruhr-University Bochum. Thereby a comprehensive study of measuring thermodynamic property data on the dew line shall be carried out.