Numerical and experimental approaches to characterize the mass transfer process in wood elements

Abstract : The scope of this paper is an experimental characterization of diffusion parameters for wood material. Based on a nonlinear mass transfer algorithm, the present study focuses on the need to capture experimental moisture profiles in the sample, along with its evolution in weighting during both the desorption and adsorption phases, especially when the moisture content of the samples is far from the equilibrium state inducing a great gradient between heart and exchange surfaces of specimen. These moisture profiles are derived by means of a gammadensimetry laboratory method based on the water adsorption of gamma rays. Determination of the diffusion parameters is obtained through optimizing a simulation by means of implementing the mass transfer kinetics into a finite difference method. Both the diffusion coefficient and convective exchange coefficient are deduced by considering a Nelder–Mead simplex inversion method. This work highlights the efficiency of the approach dedicated to uncoupling nonlinear diffusion in the cross sections from boundary conditions in terms of convective exchanges and equilibrium moisture. Scale effects and boundary conditions are also investigated herein.