The basic concept of wood drying(2)
What are the basic concepts of wood drying, do you know?
3.Equilibrium moisture content
Under certain air conditions, the wood moisture content of the wood is higher, and the wood moisture content will continue to decrease with the continuation of time. Low wood, with the continuation of time, the wood moisture content will continue to increase, and the value that the wood moisture content finally reaches and maintains is called the hygroscopic stable moisture content. The stable moisture content of desorption or moisture absorption of a thin piece of wood under certain air conditions is called the wood equilibrium moisture content. In other words, the equilibrium moisture content of an environment means that if the wood is placed in this environment, after a sufficient period of time, the wood moisture content will be equal to the equilibrium moisture content of the environment.
In general, the higher the temperature, the lower the relative humidity, and the lower the equilibrium moisture content, and vice versa. The relationship between temperature, relative humidity and equilibrium moisture content is shown in the appendix table.
Drying Gradient:
The drying gradient refers to the ratio of the moisture content of the wood to the equilibrium moisture content of the medium environment, namely:
Drying Gradient = Wood Moisture Content / Equilibrium Moisture Content
The drying gradient represents the ability of the environment to dry the wood. In general, the larger the drying gradient, the faster the wood will dry, and vice versa. However, too large a drying gradient will produce wood drying defects, so the drying kiln environment should always maintain a suitable drying gradient during drying. When calculating the drying gradient, the value range of wood moisture content is < 35%. When the wood moisture content is higher than 35%, it is calculated as 35%.
