Influence of drying medium relation humidity on drying rate of wood base on X-ray scanning method

Taking Chinese fir plantation wood(Cunninghamia lanceolata) as experimental material, an X-ray scanning method was used to analyze the influence of drying medium relation humidity on drying rate of wood in drying klin where the temperature was kept constant at 75°C with various of relation humidity(20%, 30%, 40%, 50%, 60%). The results shown that: 1) The drying rate gradient occurred that the internal layer had a higher drying rate than that of surface layer both below FSP and the whole conventional drying process, with the increase of the drying medium relation humidity, the distribution of drying rate of each layer tended to be flat; 2) Under the condition of each drying medium relation humidity, the drying rate of each layer above FSP was higher than that below FSP, and the drying rate of center layer was higher than that of surface layer; 3)When the drying medium temperature was kept constant at 75°C, with the increase of drying medium relation humidity, there was a declining trend on drying rate of center layer and surface layer both above FSP and below FSP, the ratio of the average drying rate above FSP and that below FSP shown an increasing trend; 4) In the conventional drying of Chinese fir plantation wood, the best drying medium relation humidity was 40%.