Model-based Analysis of Diffusion Experiments in Binary Gas Mixtures in a Loschmidt Cell

该研究项目的目的是通过一次实验确定气体中浓度相关的二元扩散系数。测量数据库由Fröba教授（埃尔兰根高级光学技术研究生院）的现有和新确定的实验数据提供。测量在与全息干涉仪相结合的Loschirm细胞中进行。本项目的重点是数据分析程序。以前，数据分析是基于菲克第二定律。因此，它不能解释所需的浓度依赖性的扩散系数和相互作用的影响，在气体mixed.To改善数据分析程序，一个一致的模型，描述扩散的Loschirmcell将开发在教授组的Bardow（主席的技术热力学，RWTH亚琛大学）。该模型应包括浓度依赖性、过量效应以及（如需要）吸附和重力效应。应特别注意参照系的适当选择。一个输出最小二乘法将允许包括所有的测量数据一次，并导致静态最佳的扩散系数。残差的分析提供了潜在的，以揭示需要改进的模型和实验。这个程序是有前途的，因为优秀的数据库，因为类似的分析已经成功地应用于液体中的扩散。在这个项目中开发的基于模型的程序将提供访问气体混合物中扩散的浓度依赖性的独特数据。

The research project aims at the identification of concentration-dependent binary diffusion coefficients in gases from a single experiment. The measurement database is provided by already existing as well as newly to be determined experimental data from the group of Prof. Fröba (Erlangen Graduate School in Advanced Optical Technologies). Measurements are performed in a Loschmidt cell combined with a holographic interferometer. The present project focuses on the data analysis procedure. Previously, data analysis was based on Fick's second law. Therefore, it could not account for the required concentration dependence of the diffusion coefficient and interaction effects in the gas mixture.To improve the data analysis procedure, a consistent model describing diffusion in the Loschmidt cell will be developed in the group of Prof. Bardow (Chair of Technical Thermodynamics, RWTH Aachen University). The model should include concentration dependencies, excess effects, and (if needed) sorption and gravity effects. Particular attention should be given to the suitable choice of reference frame. An output-least-squares-method will allow to include all measurement data at once and lead to the statically optimal diffusion coefficients. The analysis of the residuals offers the potential to reveal the needs for improvements in model and experiment. This procedure is promising because of the excellent database and because a similar analysis has already been successfully applied to diffusion in liquids. The model-based procedure developed in this project will provide access to unique data on the concentration dependence of diffusion in gas mixtures.