Prediction of the permeability of fibrous porous structures under the full flow regimes

Abstract

Permeability of fibrous porous structures is a key material property for predicting the gas flow path during working conditions. A direct simulation Monte Carlo method is proposed to study the H2 gas flow in fibrous porous structures under different flow regimes of the molecular flow zone, transition zone, slip zone, and continuum zone. The effects of fibrous porous structural parameters such as porosity, fiber diameter, and variance of fiber diameter on the permeability are studied. Results show that the permeability of the continuous zone is in good agreement with that predicted by the semi-empirical formula, while the permeability of other flow regimes is larger than that predicted by the semi-empirical formula, and the deviation increases with the increase in the Knudsen number. The porosity, fiber diameter, and variance of fiber diameter have positive correlations with permeability under the full flow regimes. When the Knudsen number increases, the influence degree of porosity on the permeability gradually decreases, while the influence degree of the other parameters on the permeability increases. A new empirical formula considering the Knudsen number and structure characteristics is proposed to well predict the permeability of fibrous porous structures under the full flow regimes.