Moisture content dependence of anisotropic effective thermal conductivity for recycled paper

Machine-made paper is a typical orthogonal anisotropic material vis-a-vis conductive heat transfer, and the effective thermal conductivity may change with moisture content. Two-dimensional temperature change with time within a layer of recycled paper sheets was measured using by an unsteady heating method with fine hot wire. Repeated the measurement, three-dimensional effective thermal conductivity of the layer was obtained from a set of analytical solution for the conductive beat transfer equation of the anisotropic media. The measured conductivity increases with moisture content on each dimension, and stepwisely near the fiber saturation point, which is estimated through the adsorption isotherm measured in the study.