A Closed Tube Method for Measuring Gas Diffusion Coefficients
- T. K. Tokunaga*,
- L. J. Waldron and
- J. Nemson
A transient, closed tube method for measuring both ordinary gas diffusivities and porous media effective diffusivities is presented. The current method is suitable for measuring gas diffusivities in air-dry systems over a range of temperatures. Gas concentrations are continuously monitored in a well-stirred volume of a single end chamber, which is connected to a closed sample chamber during experiments. An analytic solution for this diffusion process is available in which, after a sufficient time, the diffusivity of the sample is obtained from the slope of the logarithm of dimensionless concentration excess versus time. The method was checked by comparing measurements of N2-O2 gas diffusivities at 0, 30, and 60 °C to various previously reported values in the literature. The measured diffusivities fall within the uncertainties of these earlier works.
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