Concentration-Dependent Diffusion Coefficients of Binary Gas Mixtures Using a Loschmidt Cell with Holographic Interferometry

A model-based experimental approach is presented to measure concentration-dependent diffusion coefficients of binary gases from a single experimental run. The diffusion experiments are performed with a Loschmidt cell combined with holographic interferometry that has been improved in Part I of this paper (Wolff et al. in Int. J. Thermophys. 2018, https://doi.org/10.1007/s10765-018-2450-8). Measurements are taken with the system helium–krypton. Besides highly accurate measurements, a highly accurate diffusion model is required to retrieve the weak concentration dependence of the diffusion coefficient. We derive a consistent diffusion model considering real gas effects and the concentration dependence of the diffusion coefficient. The model describes the experimental fringe data with deviations of less than 0.2 interference fringe orders, which corresponds to a relative deviation of 0.17 % indicating high quality of both the experimental data and the employed model. Therefore, the concentration dependence of the helium–krypton diffusion coefficient could be successfully retrieved from a single experiment of mixing pure gases. Thus, the presented approach allows for the efficient characterization of diffusion in gases.