The hyperbolic heat conduction equation in an anisotropic material

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