Factors affecting the moisture content (MC) measuring during radio-frequency/vacuum (RF/V) drying

Radio-frequency/vacuum (RF/V) drying has been widely used in modern wood industry, but the key technology and mechanism for moisture content measuring during RF/V are still unknown. In this study, the aim was to measure moisture content using temperature, pressure and equilibrium moisture content during RF/V drying. The effects of drying schedules, drying time, ambient conditions in the chamber etc. on moisture content measuring were investigated during RF/V drying. In total 14 runs with different conditions were tested. The results showed that the accuracy of the moisture content measured was highly consistent in all tests either with pre-vacuum treatment or without treatment. When the drying time during RF/V reaches a certain point, there is no significant difference in moisture content measuring between pre-vacuum treatment and non-treatment. However, moisture content measuring at locations close to surfaces or open end of the timber was significantly affected by the ambient temperature and pressure condition in the drying chamber.