Moreover, owing to the low heat capacity of sawdust and the small amount of sawdust in the sample pan, as well as the relatively low drying temperature, sawdust moisture evaporation had a very little effect on ambient temperature. Hence, the temperature gradient between the surface and the center of sawdust was also negligible. Therefore, the temperature profile of the sample pan shown in Fig. 1 was also that of sawdust in each experiment. Proper determination of Deff is conducted as the isothermal condition is established.