An optical probe for liquid-liquid two-phase flows

A non-intrusive optical probe has been developed for the identification of flow patterns during liquid-liquid two-phase flow through a conduit. It is based on the difference in optical properties of the respective phases and works on the basis of the proportion of light attenuated and scattered by the two-phase mixture. The measuring system consists of a laser source, a light-dependent resistance (LDR) and a processing circuit. The source and the detector (LDR) are located on opposite sides of the test pipe to detect light after its passage through the test section containing the two-phase mixture. The LDR generates a variable resistance depending on the intensity of light incident on it. The voltage across the resistance is amplified by a three-stage amplifier circuit. The dc output of the circuit is recorded as time series signal and analysed for flow patterns during liquid-liquid flow through horizontal and vertical tubes. The probe provides similar signals for similar phase distributions in both vertical and horizontal pipes and could be applied successfully to differentiate between dispersed and separated flows in the two tube orientations. It has also been observed that the present method of detection is more effective as compared to a parallel wire conductivity probe in identifying flow patterns at high phase velocities.