微波真空干燥过程中木材内的水分迁移机理

Mechanism of moisture movement in wood during microwave-vacuum drying.

该文以马尾松木材为研究对象,对微波真空干燥过程中木材内部的含水率分布进行了研究,首次阐述了微波真空干燥过程中木材内部的水分迁移机理.研究结果表明:在微波真空干燥过程中,木材内部的含水率分布比较均匀,在厚度方向没有明显的整体性含水率梯度,特别是在干燥的后期,木材内部的含水率分布更加均匀;当含水率在纤维饱和点(FSP)以上时,木材中的自由水和水蒸气在压力梯度的作用下以渗透流的形式在木材内部迁移;当含水率在FSP以下时,木材中的水分在压力梯度的作用下以水蒸气的形式向木材表面迁移;因热扩散、含水率梯度引起的水分迁移可以忽略不计.

Based on the research of moisture content distribution in Masson pine, the mechanism of moisture transfer through wood dried by microwave-vacuum（MV） was revealed. The results indicated that, during MV drying, moisture distribution in wood was relatively uniform, without an obvious moisture content gradient along the direction of thickness of wood. Moisture distribution in wood was more uniform in the last period of drying. Above Fiber Saturation Point（FSP）, the movement of moisture through wood was assumed to be permeable movement of free water and vapor under the action of pressure gradient; below FSP, moisture existing in vapor form in wood moved in response to a pressure gradient. Moisture transfer caused by heat diffusion and a moisture content gradient could be neglected.