Capacitive direct-imaging sensor for two-phase flow visualization

This paper introduces a direct-imaging sensor based on multiple capacitance (permittivity) measurements. The sensor is fabricated in a flexible printed-circuit board (PCB) technology and comprises a driving ring electrode and a number of detecting electrodes flush-mounted into pipe peripheral. Direct images are generated representing the cross-sectional distribution of the phases in a two-phase flow. A prototype sensor was built and the system was tested in three different ways. Firstly in an air-water stratified mixture, secondly in an air-oil stratified mixture and then in a dynamic two-phase flow. Results were compared with a reference sensor showing good agreement.