Thermal Fractional Diffusion: Experimental Evidence from the Discrepancies in the Amplitude and Phase in Photothermal Technique

Abstract The photoacoustic (PA) signal is the pressure variation in the PA cell and by means of the open photoacoustic cell (OPC) technique, its amplitude and phase components are measured. In this work, the issue of disagreement between experimental measured amplitude and phase for AISI 316 samples with the expected theoretical result from the classical model is studied. The results of the thermal diffusivity obtained from amplitude are inconsistent with phase analysis. This work aims to show a way to get a unique value of thermal parameters from simultaneous analysis of the amplitude and phase of the PA signal. Also, the fractional models were applied to improve the fit of experimental data and provided results closed with the expected thermal diffusivity value.