间歇微波干燥过程中木材内含水率动态分布规律

为研究微波干燥过程中木材内部的含水率动态分布规律,以红橡和南方松木材为研究对象,采用无损检测的X射线扫描方法,揭示间歇微波干燥过程中木材内部含水率分布的动态变化规律。结果表明:微波干燥的绝大部分时间内,木材厚度方向存在着整体性内高外低的含水率梯度场;随着干燥过程的进行,木材内部水分更趋均匀,当木材平均含水率在10%以下时,木材内水分分布非常均匀;在整个微波干燥过程中,木材内部虽然发现了部分内层含水率低于外层的情况,但并未出现与常规干燥相反的含水率梯度。

Dynamic profiles of moisture content in wood during intermittent microwave drying

An accurate measurement of dynamic profiles of moisture content inside the wood is a key to understand the mechanisms of microwave drying. A new non-destructive X-ray scanning method was used to monitor the change of moisture content profiles in wood samples of red oak (Quercus rubra) and southern pine (Pinus palustris) during intermittent microwave drying. The results showed that the moisture gradients presented a similar pattern observed during conventional kiln drying, with higher moisture content in the center and lower moisture content on the surface layer during most of the microwave drying process. During microwave drying, the moisture content profiles inside the samples were flat, especially for the wood with average moisture content below 10%. Although occasionally the moisture content of the inner layers was slightly lower than that on the surface layer, the general moisture profiles during microwave drying were similar to the patterns observed during conventional kiln drying.