Multiphase Phenomena Identification by Spectral Analysis: Electrical Impedance Sensor Signals in a Bubble Column

Multiphase phenomena identification in frequency domain through an electrical impedance sensor (EIS) in air–water pipes were analyzed experimentally. The electrical properties between the components were used to settle on the relative volumes of both phases. The selection of the appropriate a.c. frequency is well known to eliminate the capacitive impedance. The EIS is a device whose variable size electrodes were used to measure void fraction and its fluctuations. Measurements were carried out with six electrodes, when air was flowed into a standing water column, producing a bubble chain. Analysis in frequency domain of the electrical impedance signals allowed the spectral power density. This analysis was correlated with observed phenomena through video recording, in order to show that low frequency peaks can be associated to dynamic phenomena, while high frequency peaks could not be clearly correlated to flow particularities.