I. On the stational drying conditions: The drying rate curves for various materials and methods from which Eq. 1 is derived are shown in Figs. 1-4. It is clear from these that the decreasing drying rate of granular material is proportional to the water content of the material. The heat transfer between air and material is shown by Eq. (2). When the temp. gradient of the material is negligibly small, Eq. (3) is obtained. As shown in Figs. 5 and 6, the temp. gradient can be neglected for the granular material whose diameter is below 2-3mm. Eq. (4) derived from Eqs. (1) and (3) may be solved numerially, e.g., by Runge-Kutta's method. When the sensible heat of water (wc·cw) contained in the material is small as compared with the specific heat of the dried material and rm≅rw, Eq. (5) can be solved analytically:(6)In case (wc·cw) has a value comparable to the specific heat of the material, Fcrw/(c+cww )(t-tw)>>1 and rm≅rw, the following approximate equation, Eq. (8), can be obtained. (8) Eqs. (6) and (8) give the relation between tm and w. II. On the unsteady drying conditions: The unsteady drying which takes place in a continuous (parallel or counter current) dryer, such as a rotary, pneumatic conveying, spary or fluidized-bed dryer, can be presented by Eqs. (9)-(12). From these are derived Eqs. (13) and (14), whose solutions show the relations among t, tm and w in the dryer. These equations could be solved numerially. The calculated examples are shown in Table 1 and Figs. 9 and 10. The drying rate and the drying time in the continuous adiabatic dryer which can be easily calculated by using these relations may help to decide the dryer volume. The application of this calculation method to the dryer design would be expatiated upon in our report.