The natural drying cycle of wood

China's vast territory, different climate, various wood natural drying final moisture content value has significant difference. In the arid Lhasa, the average annual estimated equilibrium water content is 8.6%, and in the hot and humid Haikou area, the average annual estimated equilibrium water content is 17.3%. Therefore, the truth of natural drying must be based on the local climate and seasonal characteristics of the specific analysis. Regardless of the region or the season, the drying rate of wood is faster in the first month of natural drying, and is greatly affected by the region and season in the following months. The drying time of the actual production material pile should be adjusted appropriately according to the specific situation.

In the natural drying process, the tree species is the most important factor affecting the duration of wood air drying. The drying rate and drying period of softwood wood with lower density are faster and shorter than that of hardwood with higher density. The thickness of sawing village also has a great impact on drying, and the ambient temperature is low during natural drying, and the flow of water inside the wood to the surface is slow. The drying rate of sawn timber is higher than that of raw edge when the type of sawn timber is homogeneous. The drying rate of heartwood and sapwood is different. The moisture content of heartwood is generally lower and the drying rate is slower. The sapwood contains more water and the drying rate is faster. The lower the final moisture content required by enterprises for natural drying sawn timber, the longer the drying duration. In the case of relatively high ambient air humidity, it is generally impossible to achieve a very low moisture content.

Selecting the site according to the conditions of the board yard can play a role in storage and conducive to the drying of sawn timber. The ventilation of the courtyard should be ensured to be good, and the longitudinal road of the courtyard should be parallel to the local dominant wind direction. Sawn timber of different trees and thickens is stacked in different areas, hard hardleaf wood and thick board are stacked in the center of the courtyard or in the main body of the humid wind direction, and easy to dry conifer wood and thin board are stacked in the periphery of the courtyard or above the main wind direction, so as to make full use of the climatic conditions and the role of the microclimate of the courtyard to improve the drying rate and reduce drying defects. In the process of natural drying, the drying medium depends on the microclimate zone formed between and within the pile to form a natural cycle to promote the drying of wood. Microclimate has a certain influence on the intensity of water evaporation, the temperature in the pile and the direction of air circulation, and also affects the drying rate and drying quality.