MOISTURE AND TEMPERATURE CHANGES OF WOOD DURING ADSORPTION AND DESORPTION PROCESSES

Sitka spruce (Picea sitchensis Can.) specimens, 10 mm along the grain and 20 mm in radial and tangential directions, were exposed to three different RH conditions of 22, 47, and 75% for adsorption and desorption at 30 degrees C controlled by a self-designed temperature conditioning chamber. Specimen weight was measured and thermal images were taken at certain time intervals during the processes to investigate their moisture and temperature changes. Results showed that at the beginning of the sorption process, moisture content of the specimens changed significantly and their average temperature increased about 2-7 degrees C for adsorption and decreased about 1-6 degrees C for desorption. During adsorption, the temperature for the center section along the longitudinal direction of the specimens was lower than that for the surface section, whereas the opposite was true for specimens under desorption. Along with the adsorption and desorption processes, moisture content and average temperature of the specimens were gradually approaching equilibrium state.