微波干燥过程中木材内部水分移动机理初探

该文通过测定木材微波干燥过程中内部的温度、压力和分层含水率,着重研究了在微波干燥过程中木材内部温度、水蒸气压力和水分分布状态与变化情况.通过对其相互关系的理论分析,得出了以下研究结果:在微波干燥过程中,木材内的温度分布比较均匀,但在干燥的后期,木材内温度分布的不均匀性有加大的趋势;随着干燥的进行,木材内部含水率梯度逐渐减小,含水率分布更加均匀;在木材干燥的初期,木材表面有水分“积聚”现象;在功率1000W条件下,测定规格300mm×100mm×60mm试材内部压力,纤维长度方向木材内部最大压差为20.1kPa,厚度方向木材内部最大压差为17.9kPa,表明木材微波干燥过程中在厚度和长度方向分别存在明显的蒸汽压力梯度.

Mechanism of internal moisture migration in wood during the microwave drying

The internal temperature, vapor pressure, moisture distribution and variation in wood during the microwave drying were studied by testing the internal temperature, pressure and stratified moisture content (MC). The results show that during the microwave drying, temperature is evenly distributed in wood; while at the final stage of drying, this uniformity becomes less apparent; as the drying goes on, internal moisture content gradient decreases gradually and the moisture content is more evenly distributed; at the initial stage of drying, moisture “accumulation" presents on the wood surface; the highest internal pressure gaps along directions of fiber and thickness are 20.1 and 17.9 kPa when sample size is 300 mm×100 mm×60 mm (length×width×thickness) and microwave power is 1 000 W, which indicates that marked vapor pressure gradient exists in the directions of thickness and length respectively.