MEASUREMENT OF THERMAL CONDUCTIVITIES OF MOIST POROUS BUILDING MATERIAL

Abstract

In this paper, thermal conductivity of a moist material is measured by the periodic method, based on the results of the preceding paper. Necessary conditions for reliable measurements, such as the time necessary for achieving stationary state, amplitude and angular velocity of the input surface temperature, etc., are investigated. Based on these results, temperature conductivity (which include moisture movement) of wood fibreboard is measured for several different temperatures and water contents. The results show that thermal conductivity λ* increases rapidly with water content from 0.06 (kcal/mh℃) when air dried, to 0.18 at 200 % water content. Furthermore, it increases with the mean temperature and the rate of change is rather large. This increase is mainly because of the temperature variation of vapour diffusivity D_<TV>. which is a component of λ*. Making use of this fact, the value of D_<TV> and λ (the value with no moisture movement) were gotten separately from the results obtained.