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

为了理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边界的模型，精确的实验数据是必不可少的。这种模型对于研究和工业，例如在天然气加工和碳捕获和储存领域，越来越重要。就实验数据而言，分离均相汽相区和非均相两相区的露点线是很难准确确定的。由此产生的缺乏准确的数据阻碍了理论模型的显着改善。在这种背景下，本项目的主要目标是研究一种新的技术，用于精确测量二元混合物的露点线。使用的仪器是国家标准和技术研究所的高精度双沉降密度计。选择二元混合物是因为用于多组分混合物的现有技术模型仅根据组成二元对来拟合。在第一组实验中，我们打算测量露点温度在不同的压力下选定的二元混合物。还将研究混杂的吸附和预冷凝效应。有了第一批结果，就有可能验证所应用的技术对露点温度测量的适用性。对于第二组实验，将通过整合一对新的沉降片来修改所使用的双沉降片密度计，所述新的沉降片专门设计用于改进测量露点温度的特殊目的的技术。与原来的沉降片相比，新的沉降片将具有相同的质量、相同的体积，但不同的表面特性;这将允许定量测定吸附到沉降片上的样品的质量。第二实验数据集将包括与第一数据集相同的测量点。这将允许检查使用一对特殊的沉降片的想法，并作出第一次不确定性估计。这两组测量结果将提供有关双沉降片密度计作为精确露点仪器的应用的全新信息。此外，这项工作将作为在鲁尔大学波鸿热力学主席的热物理性质的准确测量组内的未来研究的介绍性工作。因此，必须对露点线上的热力性质测量数据进行全面的研究。

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.