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.