Experimental Study of the Anisotropic Thermal Conductivity of Spruce Wood

The anisotropic fibers of wood will lead to a macroscopic anisotropic property in both mechanical strength and heat transfer. Previous experimental studies of wood materials were mainly focused on the mechanical property while their anisotropic thermal property is still lacking. In this research, the anisotropic thermal performance of spruce wood is studied at different temperature, humidity and mechanical load. The one-dimensional steady-state method and the transient plane source method are adopted to conduct the test. The thermal conductivity both in-plane and outside-of-plane of spruce wood at temperature ranging from 25 to 422 ℃, relative humidity ranging from 30–90% RH and mechanical load ranging from 0 to 20 MPa are obtained. The accuracy of the TPS method is validated using the 1D steady-state method. Both methods can be utilized to gauge the anisotropic thermal conductivity of spruce wood. Due to the unidirectional distribution of fiber, spruce wood has an outside-of-plane thermal conductivity that is roughly three times greater than its in-plane thermal conductivity. Among environmental conditions of temperature, humidity and mechanical load, the thermal conductivity of spruce wood are varied with temperature more significantly, which is followed by humidity and mechanical load. The measurement uncertainty is also discussed.