Simple, accurate, and precise measurements of thermal diffusivity in liquids using a thermal-wave cavity

A simple methodology for the direct measurement of the thermal wavelength u sing a thermal-wave cavity, and its application to the evaluation of the th ermal diffusivity of liquids is described. The simplicity and robustness of this technique lie in its relative measurement features for both the therm al-wave phase and cavity length, thus eliminating the need for taking into account difficult-to-quantify and time-consuming instrumental phase shifts. Two liquid samples were used: distilled water and ethylene glycol. Excelle nt agreement was found with reported results in the literature. The accurac y of the thermal diffusivity measurements using the new methodology origina tes in the use of only difference measurements in the thermal-wave phase an d cavity length. Measurement precision is directly related to the correspon ding precision on the measurement of the thermal wavelength. (C) 2001 Ameri can Institute of Physics.