Self-consistent photoacoustic methodologies for thermal effusivity measurements for liquids

Two self-consistent photoacoustic methodologies for the measurement of the thermal effusivity for liquids are introduced. These methodologies make use of the analytical solution for the one-dimensional heat diffusion problem for a single layer, assuming a harmonic heat source in the surface absorption limit. The analytical treatment involves fitting procedures over normalized amplitudes and phases as functions of the modulation frequency. Two values of thermal effusivity for each sample are obtained. The comparison between the experimental phases with the corresponding theoretical ones allows for the description of a simple criterion for deciding on the appropriate modulation frequency range for the analysis.