Using a fiber-optic probe for the measurement of volumetric expansion of liquids

A fiber-optic probe is developed for the fast, in-situ measurement of volumetric expansion of multiphase and multicomponent systems. An experiment with the binary mixtures of CO₂-toluene and CO₂-ethanol was conducted to demonstrate the usefulness of the fiber-optic probe in accurately tracking the isothermal volumetric expansion as a function of pressure. In the 1-L autoclave that has been used, the probe was shown to detect the liquid level height within a precision of 0.35% of the total height of the vessel. The results for the volumetric expansion of toluene and ethanol with CO₂ correlate well with those found in the literature. The probe itself can be used up to pressures of 140 barg and temperatures of 120°C.