Diffusion through fibre networks

We study gas diffusion through computer-generated random fibre networks using random walk simulations. The simulation results are consistent with steady-state experiments. The comparison of the simulated time-dependent diffusion flux with one-dimensional diffusion theory suggests that the latter is invalid at low porosities and low thicknesses. We also find that, if sorption is relevant, steady-state measurements of the diffusion constant combined with the one-dimensional diffusion theory are not enough to predict the dynamic evolution of diffusion flux. Our results demonstrate that gas diffusion through uncoated paper and board sheets can be simulated using model fibre networks, including the effects of fibre sorption.