A numerical simulation of the diffusion phenomenon was carried out in heterogeneous porous mediausing the Lattice Boltzmann method. The developed code was tested on a rectangular lattice divided in two subdomains, each of them associated to a thermal conductivity. Once validated, the code was used to compute the equivalent thermal conductivity of the cellular structure of spruce. The simulation was done in the two transverse direction of wood (radial and tangential). The computed equivalent thermal conductivities in tangential and radial direction are quite close to the theoretical values obtained for the same phases placed in parallel. These results are in good agreement with pervious works and then represent the first step for modeling the mass and thermal diffusion coupling through a three-dimensional heterogeneous porous media.