High frequency vacuum drying is a combined drying method of high-frequency medium heating and vacuum low-temperature drying, which is a fast and almost waste free drying method, especially suitable for drying hardwood and heavy wood. High frequency heating: Also known as high-frequency medium heating, it converts a regular 380V AC power supply into a high-frequency electromagnetic field after boosting and rectifying it. High frequency heating can be achieved through related supporting equipment with anode and cathode plates. High frequency heating is penetration heating, where the moisture in the electric field is uniformly heated. The parts with more moisture absorb more high-frequency electric fields, while the parts with less moisture only absorb a small amount of high-frequency electric fields. This effectively utilizes the high-frequency output power. However, media such as wood or fiber, due to their lack of polarity, do not absorb electric fields, and high-frequency power is basically used without waste, saving energy consumption and reducing drying costs.
Vacuum state mainly utilizes the lower boiling point of water in vacuum state, which accelerates the evaporation rate and increases the gradient of moisture content on the surface of wood. During the drying process, on the one hand, surface moisture evaporates into the surrounding air, and on the other hand, internal moisture continuously moves towards the surface, thus accelerating the drying rate at lower temperatures, ensuring the drying quality of wood. The vacuum state is a negative pressure state that has a certain water absorption effect, which is exactly similar to the high-frequency pressure gradient and accelerates the discharge of moisture from the wood core. In addition, under low pressure conditions, the oxygen in the drying medium causes less discoloration of the material due to thermal and oxidation effects, which can basically maintain the natural color of precious wood.
Based on the above characteristics, the application of high-frequency vacuum drying in wood drying has become a scientific and environmentally friendly drying method, especially suitable for drying hardwood with a large cross-section.