Gas flow in hardwoods

Abstract

A model was developed for describing the axial gas flow through hardwood samples, and gas permeability variations with increasing specimen length. To that effect, the mean vessel length of the wood species (λ) was taken into account, and the intervessel junction was modelled as a perforated plate. Mass and momentum conservation equations were then used to describe the fluid evolution through it. Outside the junction, wood was assumed to be a permeable material of Darcian behaviour. Thus, by combining Darcy's equations with the one derived for the junction zone, a system of equations was obtained modelling the overall fluid flow through the sample. The model was experimentally tested on ceibo (Erythrina crista-galli L.) samples of different lengths. Their gas permeabilities were measured, and the permeability of a zero-length sample (equivalent to that of an ideal specimen of infinitely long vessels) was calculated by means of an existing model. By introducing this last parameter into the above mentioned equation system, a theoretical value for the gas permeability was obtained. A fair agreement was observed between the model and experimental values, the differences between them being attributable to a number of simplifying assumptions that were made in order to render the system mathematically tractable.