Analysis of the Vacuum Drying Rate for Red Oak in a Hot Water Vacuum Drying System

Red oak boards of 76.2 cm (long) × 7.62 cm (wide) × 2.54 cm (thick) were dried from green moisture content (MC) to 7% MC in the hot water vacuum-drying system. These boards were dried at the pressure of 12 mm Hg and the temperatures ranging from 30 to 50°C within 25 to 70 h. Drying rates were measured and drying curves were calculated. The results showed that the drying rate was higher at higher temperatures. The vacuum drying was faster when wood MC was above 30% than when it was less than 30%. The individual samples did not dry at the same drying rates even at the same drying conditions because of anatomical variations between boards.