Three-dimensional measurement of temperature distribution in wood during Radio-Frequency/Vacuum drying

In this study, we measured the temperature at many points using a fiber-optic and a platinum sensor in boxed heart, square timber of Sugi under various drying conditions that could affect temperature distribution. We then constructed a three-dimensional distribution chart of the average temperature during drying. During RF/Vacuum drying, the temperature near the midpoint between two opposing electrode plates should be higher than the boiling point corresponding to the ambient pressure, but the temperature near the plates and the evaporating surfaces should be less. The moisture content distribution after drying along the thickness direction (direction of the electric field) was affected by the drying temperature distribution. The region where the temperature was lower than the boiling point still had very high moisture content. In the other directions the temperature distribution had no effect on moisture content distribution. This difference was caused by two modes in heat transfer to reduce the surface temperature.