Examples of Nonisothermal Moisture Movement in Wood

Moisture content gradients in wood samples subjected to nonisothermal conditions were monitored over time in two separate experiments using sample material from 1) green ash and 2) southern yellow pine. The warm and cold environment temperatures were maintained at 80 F and -40 F for both experiments. The warm environment relative humidity was maintained at 40% during the ash experiment, and 70% during the southern yellow pine experiment. The cold environment relative humidity was not controlled, but was presumed to be nearly 100%. The temperature gradient through the samples was measured using embedded Type-T thermocouples, and the moisture content profile from the warm to cold surface was determined by sectioning sample material.Total average moisture content generally increased as a function of time, indicating that moisture flux into the sample through the warm surface was greater than flux out of the sample at the cold surface. Moisture accumulated toward the warm surface for the southern yellow pine, but was generally more evenly distributed through the depth for the ash samples. These differences were attributed to different warm environment relative humidity conditions maintained between the two experiments