Transport through a slab membrane governed by a concentration-dependent diffusion coefficient. Part I. The four time-lags: some general considerations

Permeation of gases in polymers: parameter identification and nonlinear regression analysis

“…Variations of this method have been proposed in [4,5,10,11] which are trying to extend it to the nonlinear case, i.e. to the case of a concentration-dependent diffusion coefficient.…”

“…To overcome this problem Ash et al [10,11] propose a method involving time-lag estimates from different permeation, sorption and desorption experiments. This basically reduces to an approximation of the nonlinear least-squares optimisation problem by a series of linear problems.…”

“…In a series of papers Ash et al [10,11] have also studied nonlinear diffusion models for the permeation of gases in polymers. However, they mainly analyse the form of the permeation curves for different theoretical models of the diffusion coefficient and do not concentrate on the identification of specific model parameters from actual experimental data.…”

“…For a more exhaustive literature review on nonlinear diffusion models for the permeation of gases in polymers see [1,[10][11][12][13] and the references therein.…”

A Novel Time Lag Method to Measure the Permeation of Vapor-Gas Mixtures

“…Time lag analysis also represents an excellent example of mathematical interpretation of a physical process. Since the 'Method of Frisch' was proposed [1], a number of research progresses have been made with time lag analysis on such aspects of: concentration dependent diffusion coefficient [2], spatial/time dependent diffusion coefficients [3], the effect of isotherm and membrane geometry [4,5], structural heterogeneity [6], and blind pore characteristics [7], etc.. A conventional time lag experimental rig consists of upstream and downstream vessels separated by a membrane cell. The pressures in the upstream and downstream vessels are monitored continuously by pressure transducers, respectively.…”