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Projekt Druckansicht

Diffusionskoeffizienten von Gasgemischen mittels Loschmidt-Verfahren basierend auf holografischer Interferometrie

Fachliche Zuordnung Technische Thermodynamik
Förderung Förderung von 2011 bis 2015
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 190778119
 
Erstellungsjahr 2016

Zusammenfassung der Projektergebnisse

A Loschmidt cell combined with two holographic interferometers was applied to determine the concentration dependency of gaseous binary diffusion coefficients in one experimental run using pure gases prior to the diffusion process. The measurement apparatus was validated by investigating the concentration, temperature, and pressure dependency of the binary diffusion coefficient for the two noble gas systems argon-neon and krypton-helium. It could be shown that for a mean mole fraction of 0.5 reliable temperature and pressure dependent data with an uncertainty of 2% can be obtained. Afterwards, binary diffusion coefficient data for more complex and technical interesting systems for which barely or no data are available in literature were determined. For this, the systems ammoniahelium, nitrous oxide-nitrogen, and propane-helium were chosen. Concerning the concentration dependency, discrepancies were found both for the noble gas and the molecular gas systems. According to theory, the binary diffusion coefficient should increase over the mole fraction of the heavier component. This is in agreement with experimental data from literature where gas mixtures are used prior to the diffusion process in combination with a noninterferometric gas analysis method. Here, several time-consuming measurements must be performed to determine the concentration dependency. Our experimental results and further literature data where pure gases are used prior to the diffusion process in connection with an interferometric gas analysis method showed disagreements to the other literature data and no reliable trend of the binary diffusion coefficient over the mole fraction of the heavier component could be figured out. Therefore, efforts were made to identify the reason for the discrepancies, where several potential errors sources could be excluded. Experimental data from literature which are in agreement with theory were determined with a non-interferometric gas analysis method analyzing concentration differences between the two half-cells. Furthermore, for these data, gas mixtures of nearly the same compositions were used prior to the diffusion process. This is different to the interferometric gas analysis method applied in the present project, where the concentration dependency is detected in one experimental run simultaneously and independently in both half-cells of the Loschmidt cell. To compare both evaluation procedures, we used also gas mixtures and we performed a data evaluation based on concentration differences between the half-cells. Then, the binary diffusion coefficient is in agreement with data provided by methods based on the same data evaluation strategy and with theoretical data.

Projektbezogene Publikationen (Auswahl)

 
 

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