The moisture in the wood, the vacuum drying equipment can move in the direction of the fiber under certain conditions, from the two end faces of the wood tree, or can move transversely to the fiber direction, and is discharged from the side of the wood tree. This property is called the moisture of the tree. Conductivity. The moisture in the wood moves at a speed of 12-15 times faster than the transverse fiber direction, but the side area of ​​a sawn timber is much larger than the end surface area. Therefore, when the wood tree is dry, the water mainly depends on the direction of the transverse fiber, from the surface of the board. evaporation.
During the drying process of the wood tree, the free water in the cell cavity on the surface of the wood tree is first evaporated. When the free water in the surface layer is evaporated, the water in the cell wall is evaporated. The evaporation surface gradually penetrates into the interior, and the wood section forms an inner high. Low water content, moisture pressure in the inner layer of the wood tree, and the pressure of the vacuum drying device on the outer layer. Due to the pressure difference, the water moves in the liquid form along the microcapillary system in the cell sag from the inside to the outside, while the water is still The large form of the vapor form along the cell cavity moves from the inside out to the surface.
When drying, the movement of moisture in the wood, in addition to the moisture content gradient, the temperature gradient is also a factor that causes moisture to move, and the moisture moves from a high temperature to a low temperature. Under normal circumstances, the internal moisture of the wood is higher than the outside, forming a moisture gradient inside the inner high and the outer, so that the water is conducted from inside and outside.
When the atmosphere is dry, the temperature difference between the dry lining and the outside is small, the temperature influence is small, and the moisture inside the wood is mainly caused by the pressure difference caused by the water content gradient, so that the water gradually moves to the surface to evaporate to dry dry vacuum drying equipment.