Rarefied gas flows in softwood tracheid network: identification of morphological parameters from gas permeability measurements
Résumé
We propose a new method to identify morphological parameters of porous (bio)materials. This method is based on gas apparent-permeability measurements and takes advantage of the flow regime changes which occur at different pressure depending on the pore size. The apparent permeability at a given mean pressure is measured from the pressure relaxation kinetics when gas is allowed to permeate through the tested material from a slightly higher pressure compartment to a slightly lower pressure one. Our setup is able to measure apparent permeability ranging from 10e-10 to 10e-18 m2. Then, morphological parameters are identified from the variations of apparent permeability as a function of the mean pressure, thanks to a pore network model. The network consists in elements such as pipes, slits or orifices connected in series or in parallel. The unknowns may be the connectivity of the network, the duct diameter or the slit width for example. The flow in each element is described by the appropriate model. The unknowns are determined by minimizing the deviation between the experimental variations of the apparent permeability and the simulated ones. The present approach is first applied to track-etched polycarbonate membranes. It appears that the identified pore radius is of 38 nm, close to the measured value by scanning electron microscopy equal to 35 nm. Then, Norway spruce is tested: the identified mean pit radius and pits number per tracheid in both tangential and longitudinal direction are in reasonable agreement with anatomical data reported in literature.
Origine : Fichiers produits par l'(les) auteur(s)
Loading...