Effects of diffusion drying schedules on gas and liquid permeability in Paulownia fortunei wood

Abstract

As to the importance of permeability in the preservation process of solid woods, the effects of diffusion drying schedule with three different initial moisture contents (MC) on fluid flow in the sapwood and heartwood of paulownia wood (Paulownia fortunei) were studied here. Boards with initial MCs of 113 % (D-1), 75.5 % (D-2) and 53.5 % (D-3) were dried to the final moisture content of 8 ± 2 %. Results showed a significant difference in the specific gas and liquid permeability of paulownia wood dried with these different initial MCs. Although gas permeability of sapwood and heartwood specimens was significantly different, no significant difference was seen in liquid permeability between these two parts. D-2 and D-1 showed the highest specific gas and liquid permeability, respectively. It was therefore concluded that the initial MC has a significant effect on the gas and liquid permeability of paulownia boards dried under diffusion schedule with different MCs. Furthermore, the presence of tyloses plays a more important role in permeability than vessel size and frequency by forming an impermeable barrier, resulting in a significant decrease in gas and liquid permeability in paulownia wood.