Nonisothermal moisture movement in wood

Abstract

In order to analyze the effect of temperature gradient on moisture movement during highly intensive drying, such as microwave-vacuum drying, the profile of the temperature and moisture content in sealed wood whose opposite faces were subjected to temperature gradient for a short time was measured. The ratio of the moisture content (MC) gradient to the temperature gradient (dM/dT) was calculated and the factors influencing moisture movement under nonisothermal conditions were discussed. The results indicate that moisture moved in wood from the warm surface to the cold one even if opposite faces of the sealed wood assembly were exposed continuously to different but constant temperatures for a short period. The moisture content on the cold surface was higher than that on the warm surface. The moisture content gradient opposite to the temperature gradient was established, and the dM/dT was below 0.9%/vH. The temperature in the sample and the distance from the hot surface of the sample was strongly linearly correlated. With an increase in temperature, initial moisture content and experimental time, the dM/dT was significantly increased.