Water Vapor Sorption Rates By Wood Cell Walls

Rates of water vapor adsorption and desorption by the cell walls of yellow poplar (Liriodendron tulipifera L.) and white oak (Quercus alba L.) were measured at 40 C in the absence of air. The rates were much lower than would be expected for Fickian diffusion of bound water. Species had little effect, but desorption was faster than adsorption, especially at higher humidities. The shapes of the rate versus remaining moisture content curves were also decidedly non-Fickian in nature. Heat transfer to the specimen was found to play an important role. An empirical equation was found to fit the data with a high degree of accuracy, but only limited success was achieved in relating the constants of the equation to the corresponding relative humidity levels