Multicomponent gas diffusion in nonuniform tubes |
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Authors: | Thomas Veltzke Lars Kiewidt Jorg Thöming |
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Affiliation: | Dept. of Chemical Engineering, Center for Environmental Research and Sustainable Technology (UFT), University of Bremen, 28359, Bremen, Germany |
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Abstract: | In many technical processes gas, multicomponent diffusion takes place in confinements that are rarely uniform in direction of their long axis (e.g., catalysts pores). Here, we show that in conical tubes multicomponent diffusion is hindered. This effect increases with ratio of inlet to outlet cone radius Λ, indifferent of the orientation of the tube. Based on the Maxwell–Stefan equations, predictive analytical solution for ideal multicomponent diffusion in slightly tapered ducts is developed. In two‐bulb diffusion experiments on a uniform tube, the results of Duncan and Toor (1962) were reproduced. Comparison of model and experiment shows that the solution presented here provides a reliable quantitative prediction of the temporal change of H2, N2, and CO2‐concentration for both tube geometries, uniform and slightly conical. In the demonstrated case (Λ = 3.16), mass diffusion is 68% delayed. Thus, for gaseous diffusion in “real,” typically tapered pores the transport limitation is more serious than considered so far. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1404–1412, 2015 |
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Keywords: | gas multicomponent diffusion experiments on conical tubes classical Maxwell– Stefan equations analytical transport model two‐bulb diffusion experiment |
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