The factors that affect the speed of wood drying are varied, the most important ones are explained below:

✓ Temperature

Temperature is the main external factor that determines the speed of wood drying. When wood is surrounded by high-temperature air, the heat needed to increase the temperature and evaporation of water in the wood is supplied by convective heat transfer. The higher the temperature of the medium, the higher the temperature of the wood and its internal humidity, which accelerates the thermal movement of water molecules and improves the speed and intensity of moisture evaporation. Therefore, increasing the temperature can speed up the drying rate, but too high a temperature will cause the strength and performance of the wood to decrease.

✓ Air humidity

When the temperature is constant, the decrease in air humidity will make the moisture in the wood evaporate into the air more easily and the drying speed will be accelerated. On the contrary, if the air humidity increases and reaches 100%, the drying rate slows down and the evaporation of water stops.

✓ Air circulation speed

The speed of the air in the drying medium directly affects the evaporation of water on the surface of the wood. When the velocity of the air over the surface of the wood exceeds 1 m/s, the airflow is turbulent. Improving the ability of the air to transfer heat to the wood and absorb water vapor on the surface of the wood, but generally does not exceed 3 m/s.

✓ Water content gradient

The water content gradient is the driving force for the movement of moisture in wood. The water content in the wood moves from a place of high content to one of low water content.

The greater the difference in water content, ie a larger gradient, the higher speed of water movement and faster drying speed will be obtained.

In the drying process, a moisture content coating gradient with a high interior and a low exterior should be formed to promote internal moisture to move outward, but care should be taken not to cause a moisture content gradient. excessive and not to form a layer of saturated vapor on the surface of the wood. Otherwise, not only can the moisture not continue to move out, but it will also cause drying defects. (mold and mildew)

✓ Temperature gradient

The temperature gradient is also the driving force for the movement of water in wood. In the normal drying process, the surface temperature of the wood is higher than the internal temperature, because the temperature gradient is higher inside the wood, making it difficult for moisture to move out.

In order to cause a high temperature gradient on the outside and make it consistent with a high water content gradient on the inside and a low water content gradient on the outside, and together push the water content in the wood to move out quickly.

High temperature and high humidity media are generally used to treat wood, so that the wood can be fully heated without evaporating water, and the internal temperature of the wood can be increased; Then the temperature and humidity of the medium are lowered to lower the surface temperature of the wood, but the interior of the wood is still kept at a high temperature, thus forming a temperature gradient with high inside and low outside, which is consistent with the moisture content gradient with high interior and low exterior, and accelerating the movement of moisture in the wood.

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