The Hyperbolic Heat Conduction Equation in an Anisotropic Material

In this work, the phase-lag concept in the wave theory of heat conduction is extended to describe the thermal behavior of an anisotropic material. This is achieved by assuming that there are phase lags of different magnitudes between each component of the heat flux vector and the summation of temperature gradients in all directions of the orthogonal coordinate system. Also, expressions are provided to specify the locations of the principal coordinate axes, the prin- cipal thermal conductivities, and the principal thermal relaxation times.