Preliminary study of wood ultrasoundvacuum combined drying dynamics.

Combined with the advantages of ultrasound drying and vacuum drying, Juglans mandshurica Maxim was dried by ultrasound\|vacuum combined drying method at different drying temperatures, absolute pressures, ultrasound power and frequency conditions. The water effective diffusion coefficient during drying process was measured, and the drying dynamics model was also established. The results showed that the value of the water effective diffusion coefficient increased along with the increasing temperature, while absolute pressure had little effects on the water effective diffusion coefficient during the ultrasound\|vacuum drying process; temperature had significant effects on drying rates; the variation trends of drying rates versus time were approximate at the same temperature and different absolute pressure conditions; the drying model, which was established based on the effective diffusion coefficient equation and the Ficks unidirectional diffusional equation, was approximate to the practical drying dynamics.