Gas Diffusion in Closed-Cell Foams

Abstract

The objective of this paper is to present an engineering model, based on fundamentally sound but simplified treatment of mass diffusion phenomena, for practical predictions of the effective diffusion coefficient of gases through closed-cell foams. All assumptions and simplifications that define the range of applicability of the proposed model are clearly stated. The model developed is based on the electrical circuit analogy and on the first principles. The analysis suggests that the effective diffusion coefficient through the foam can be expressed as a product of the geometric factor and the gas diffusion coefficient through the foam membrane. Comparison of model predictions with experimental data available in the literature shows satisfactory agreement. Discrepancies between predictions and data have been noted for gases with high solubility in the condensed phase for which Henry's law does not apply. Additional experimental data for both the foam morphology and the diffusion coefficient in the membrane are needed to fully validate the model.