Ultrahigh-resolution pyroelectric thermal-wave technique for the measurement of thermal diffusivity of low-concentration water-alcohol mixtures

摘要

Thermal diffusivities of water-methanol and water-ethanol mixtures were measured using a thermal-wave cavity with two techniques: conventional single-pulse photopyroelectric frequency scans and the common-mode-rejection demodulation dual-pulse scheme. The frequency-scan measurements showed maximum resolution of the photothermal signal in water at the level of 0.5percent by volume in mixtures of methanol and ethanol. The common-mode-rejection demodulation method improved the resolution up to the level of 0.2percent by volume, which is the highest thermophysical resolution of water-methanol and water-ethanol mixtures reported to date, to our best knowledge. The ultrahigh sensitivity of the method can be especially useful in environmental applications, specifically in real-time water pollution monitoring.