The aim of the study is to illuminate the mechanism of drying phenomena as well as to establish a set of mathematical equations for heat and mass transfer within a porous body. The modeling method is described on the basis of recent advances and is classified according to the importance of gas pressure gradient. The mathematical model provides its acceptable reasonability through the comparison between experimental and calculated results, and also it must be useful to comprehend the effects of the temperature and moisture gradient and gravity on the heat and mass transfer in porous media.