Abstract:

Using the Masson Pine as specimen, when the medium were super_heated steam and air respectively, the preheating characteristics of wood in wood drying under vacuum-floating pressure were discussed by the measurement of the internal temperature field and the variation of moisture during the stage of preheating. The relationship between drying medium condition and the rate of drying revealed that: Firstly, compared with the process of air-drying, the time needed to be preheated under vacuum-floating decreased dramatically, meanwhile, the magnitude of condensation on the surface was relatively larger. Secondly, the rate of wood drying under vacuum-floating increases coupled with the temperature of medium, the reduction of absolute pressure, and the raise of fluctuation rate of frequency. The sequence of factors' contribution to drying rate was listed as following: the temperature of medium (T)>the fluctuation rate of pressure (H_{z<.sub>)>absolute pressure (P).}

Key words: Wood drying, Vacuum, Floating pressure, Preheating, Drying characteristics