CONVECTIVE DRYING MODEL OF SOUTHERN PINE

A transient one dimensional first principles model is developed for th e drying of a porous material (wood is used as an example) that includ es both heat and mass transfer. Heat transfer by conduction and convec tion, mass transfer by binary gas diffusion, pressure-driven bulk flow in the gas and liquid, and diffusion of bound water are included in t he analysis. The diffusive mass transfer terms are modeled using a Fic kian approach, while the bulk flow is modeled assuming Darcian flow. D epending on the state (pendular or funicular) of the moisture in the w ood, appropriate terms are considered in the development of the govern ing mass equations. The results provide distributions within the mater ial of each moisture phase (vapor, liquid, and bound), temperature, an d total pressure. Information regarding the drying rate and evaporatio n rate is also presented. Average distributions are obtained as a func tion of time, and compared with experimental data from the literature. It is observed that the total pressure within the material can be con siderably above one atmosphere during the drying process.