Abstract: Because mass propagation velocity has a finite value for porous media in an unsteady mass transfer process, the hypothesis that mass propagation velocity in a mass transfer process is infinite is inconsistent with the real situation in the case of wet porous materials in a highly intense drying process. In this paper, a description of an unsteady humidity profile in the form of the hyperbolic equation is made. From the equation, wave characteristic can be seen in the mass transfer field of the inner material. One-dimensional hyperbolic equation of mass transfer within wet porous materials in a highly intense drying process is developed. The non-Fick phenomena in a highly intense drying process are analyzed by the comparison of the solutions between the Fick equation and the non-Fick equation. The calculation results show that when mass flux or mass transfer coefficient is high, the non-Fick effect is noticiable and it is not negligible in an intense drying process.

Key words: highly intense rapid drying, porous media, mass relaxation time, non-Fick effect, abnormal mass transfer