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Gas diffusion in random‐fiber substrates
Author(s) -
Melkote Rajesh R.,
Jensen Klavs F.
Publication year - 1989
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690351205
Subject(s) - knudsen number , knudsen diffusion , porosity , knudsen flow , monte carlo method , porous medium , materials science , diffusion , fiber , gaseous diffusion , composite number , mechanics , thermodynamics , composite material , chemistry , physics , mathematics , statistics , electrode
A Monte Carlo (MC) technique involving explicit calculation of molecular trajectories in fibrous media is used to obtain effective transport coefficients in the Knudsen regime of gas diffusion. A fully penetrable cylinders (FPC) model is used to represent a fibrous substrate during the course of densification, as in composite fabrication processes such as chemical vapor infiltration (CVI). The calculated Knudsen permeabilities are in excellent agreement with available data. Accessible porosities are computed as a function of total porosity and are shown to depend on the fiber number density. The nonfiber phase is shown to percolate at ϕ ≈ 0.095, but the threshold is sensitive to the boundary conditions employed.