Thermal-wave resonator cavity design and measurements of the thermal diffusivity of liquids

A liquid-ambient-compatible thermal wave resonant cavity (TWRC) has been constructed for the measurement of the thermal diffusivity of liquids. The thermal diffusivities of distilled water, glycerol, ethylene glycol, and olive oil were determined at room temperature (25 °C), with four-significant-figure precision as follows: $(0.1445±0.0002)×10−2 cm2/s$ (distilled water); $(0.0922±0.0002)×10−2 cm2/s$ (glycerol); $(0.0918±0.0002)×10−2 cm2/s$ (ethylene glycol); and $(0.0881±0.0004)×10−2 cm2/s$ (olive oil). The liquid-state TWRC sensor was found to be highly sensitive to various mixtures of methanol and salt in distilled water with sensitivity limits 0.5% (v/v) and 0.03% (w/v), respectively. The use of the TWRC to measure gas evolution from liquids and its potential for environmental applications has also been demonstrated.