Photoacoustic methodologies by using diode laser as light source for precise measurements of thermal diffusivity for liquids

摘要

The analytical solution for the one-dimensional heat diffusion problem, involving three layers and assuming surface absorption only, is shown to be useful to provide of a simple photoacoustic methodology for the direct measurement of the thermal-wavelength for thermal waves generated across liquid samples. A simple methodology for measuring thermal diffusivity for liquids, taking advantage of the relationship between this thermal property and the thermal wavelength, is developed. The thermal diffusivity of two pure liquids (distilled water and ethylene-glycol) was measured and excellent agreement was obtained with the corresponding thermal-diffusivity values reported in the literature. A photoacoustic experimental setup, using diode laser as ligth source, is also showed to be very suitable to carry out this kind of experiments.