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

A liquid-ambient-compatible thermal wave resonant cavity (TWRC) has been co nstructed for the measurement of the thermal diffusivity of liquids. The th ermal diffusivities of distilled water, glycerol, ethylene glycol, and oliv e oil were determined at room temperature (25 degrees C), with four-signifi cant-figure precision as follows: (0.1445 +/- 0.0002)x10(-2) cm(2)/s (disti lled water); (0.0922 +/- 0.0002)x10(-2) cm(2)/s (glycerol); (0.0918 +/- 0.0 002)x10(-2) cm(2)/s (ethylene glycol); and (0.0881 +/- 0.0004)x10(-2) cm(2) /s (olive oil). The liquid-state TWRC sensor was found to be highly sensiti ve to various mixtures of methanol and salt in distilled water with sensiti vity limits 0.5% (v/v) and 0.03% (w/v), respectively. The use of the TWRC t o measure gas evolution from liquids and its potential for environmental ap plications has also been demonstrated. (C) 2000 American Institute of Physi cs. [S0034-6748(00)01407-6].