真空条件下木材表面水分蒸发速率模型及应用初探  

A model of water evaporation rate from wood surface and its application under vacuum condition

作　　者：何正斌[1] 李帆[1] 伊松林[1] 张璧光[1] 

机构地区：[1]北京林业大学材料科学与技术学院,木材科学与工程北京市重点实验室,木质材料科学与应用教育部重点实验室,北京100083

出　　处：《北京林业大学学报》2010年第6期105-108,共4页Journal of Beijing Forestry University

基　　金：国家自然科学基金项目(30871978)

摘　　要：对真空条件下木材表面水分蒸发速率模型进行了理论推导,并以截面为20mm×20mm,长度分别为100、150、200、250、300mm的桦木为试材,在干燥温度分别为60、75、90℃,绝对压力分别为0.02、0.04、0.06、0.07、0.08MPa的真空干燥条件下,对试材内部水分移动速率进行研究。结果表明:木材表面水分移动速率大于内部水分移动速率,二者的比值在10～150之间变化。根据试验结果,得出了不同条件下各种规格试材的干燥速率与温度、绝对压力的关系式,并与理论推导得出的模型进行比较,得到木材表面水分蒸发速率与内部水分移动速率之比。最后根据不产生干燥缺陷的最大(极限)速比,得出木材真空干燥过程中不产生缺陷时的温度和绝对压力的关系式。We developed a model of water evaporation rate from wood surface under vacuum condition using birch as material with cross-sectional area of 20 mm × 20 mm and length of 100, 150, 200, 250 and 300 mm. The internal water moving rates of specimen were studied under the temperature of 60, 75 and 90℃ and absolute pressure of 0.02, 0.04, 0. 06, 0.07 and 0.08 MPa. The results show that the surface water evaporation rates were much faster than the internal water moving rates, and the ratio of the former to the later varied from 10 to 150. In addition, the relations of the drying rate with temperature and absolute pressure under different conditions were deduced based on the experimental results. Compared with the model of surface water evaporation rate, we can obtain the ratio of the wood surface water evaporation rate to the internal water moving rates from the regression equation. Finally, the optimum formula between temperature and absolute pressure was deduced according to the maximal ratio of the surface water evaporation rate to the internal water moving rate, which could cause drying defects during vacuum drying.

关 键 词：水分移动 干燥速率 理论推导 干燥缺陷 

分 类 号：S781.71[农业科学—木材科学与技术]