Development of noble four-sensor conductivity probe and its signal processing scheme

A four-sensor conductivity probe is designed to effectively minimize the reported limitations of the previous designs. Its added capability of measuring both small and large bubbles enables the new probe to be utilized in a wide range of two-phase flow regimes. The signal processing scheme constructed for the newly designed probe is presented. The two phase parameters of different types of bubbles are identified and categorized in view of building data basis for development of the two-group interfacial transport equation. The experimental data are obtained in a 5.08 cm ID vertical co-current air/water loop by the probe at two different axial locations of L/D=32 and 64. The local time-averaged two-phase parameters obtained by the probe include the interfacial area concentration, void fraction, interface velocity, cord length, and Sauter mean diameter for various types of bubbles. The development of geometric two-phase flow parameters along the axial direction of the flow duct are well demonstrated. Characteristic signatures of both large and small bubbles are quantified. Image analysis is employed to compare the experimental data with theoretical calculations. A good agreement is obtained which assesses both the measurement principle and the capability of the signal processing scheme. (author)