Method of measuring thermal relaxation in the solid state

The differential equations of heat conduction of a solid body, which are a consequence of the Fourier, Cattaneo–Vernotte, and Lykov’s equations, are considered. A mathematical model of the transient, three-period process in a circular plate is constructed in the form of a solution to the hyperbolic boundary value problem of heat conduction with boundary conditions of the third kind. The method to determine the Bio numbers in each period of the transition process and the time of thermal relaxation is described by the results of experimental and theoretical studies of transient thermal processes in the center of round plates of different thicknesses made of polymethylmethacrylate upon their sudden immersion in hot water.