Open AccessMeasurement of Gas Diffusion Coefficient in Highly Permeable Porous Media
Author(s) -
Levintal Elad,
Dragila Maria I.,
Kamai Tamir,
Weisbrod Noam
Publication year - 2019
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2018.08.0164
Subject(s) - porous medium , diffusion , gaseous diffusion , isothermal process , effective diffusion coefficient , permeability (electromagnetism) , molecular diffusion , thermodynamics , diffusion process , chemistry , diffusion equation , porosity , materials science , analytical chemistry (journal) , chromatography , physics , membrane , innovation diffusion , composite material , operations management , economy , service (business) , metric (unit) , knowledge management , computer science , magnetic resonance imaging , biochemistry , radiology , medicine , electrode , economics
Core Ideas A modified method was used to quantify gas diffusion within coarse media. All data were highly correlated to an inverse solution of the diffusion equation. D P / D 0 results were in the range of common D P / D 0 predictive models. Observed increase in gas transport with permeability was named enhanced diffusion . Gas diffusion is a fundamental transport process in porous media. However, to date, there is no method for experimentally estimating the gas diffusion coefficient of coarse porous media. A modified method is proposed here and was validated against sand media. The method was tested using particle sizes ranging between 1 and 4 cm: ∼10 −3 cm 2 < intrinsic permeability < ∼10 −2 cm 2 . Laboratory experiments were conducted in large horizontal columns filled with different homogeneous spherical particles inside a climate‐controlled laboratory under isothermal (± <0.2°C) and windless conditions. Diffusion coefficients were similar for particles sizes of 1 and 2 cm, which indicates that pure diffusion governs gas transport. Above 2 cm, diffusion coefficients were higher, suggesting an enhanced gas transport, most likely initiated by small, local advective components. Because the enhanced transport can be modeled by the diffusion equation using a larger diffusion coefficient, it is associated with the enhanced diffusion concept.