Influence of moisture content on the thermophysical properties of tropical wood species

The aim of this work was to investigate the thermal behavior of solid wood used as building materials. Three tropical wood species namely Iroko (Milicia excelsa), Bilinga (Nauclea diderrichii), and Tali (Erythrophleum suaveolens) were chosen. The thermophysical properties in the longitudinal, radial and tangential directions were determined experimentally for different moisture contents. Asymmetrical hot plate method was used to measure the thermal conductivity and volumetric heat capacity. The influence of water content and the direction of the fibers on thermophysical properties of the species studied were investigated. The results show that thermal conductivity and volumetric heat capacity increase with moisture content, while the diffusivity decreases. In the wide range of moisture content considered, thermal conductivities varied between 0.1 and 0.6 Wm−1 K−1. The increase of moisture content by 1% induces a 0.2% increase in thermal conductivity for Bilinga, 0.4% for Tali and 0.3% for Iroko. Tali, whose density is the highest, presented high values of thermal conductivity in longitudinal direction but lowest values in radial and tangential directions compared to other species. Thermal conductivity is 2 to 3 times higher in the longitudinal direction than in the radial and tangential directions. The volumetric heat capacity was not influenced by the direction of the heat flow.