Design and Development of a Capacitance Sensor for Gas/Gas or Gas/Liquid Void Fraction Detection

A capacitance-based void fraction sensor was designed to detect a range of liquids and gases. The sensor comprises two semi-concave copper electrodes mounted on a hollow cylindrical glass tube. When a radio frequency signal is applied, variations in the dielectric constant of the surrounding medium cause measurable phase shifts in the signal. Experiments with tap water, distilled water, and ethanol showed that the phase shift is directly correlated with the dielectric constant of the liquid. To study gas-phase behaviour, measurements were carried out under mesoporous conditions (10% liquid and 90% gas flow), allowing characterisation of gas molecules based on their dielectric responses. Signal variations were captured using a digital storage oscilloscope, and the observed phase shifts were compared with theoretical values computed using Mathematica. The experimental findings closely matched the theoretical predictions, validating the sensor’s effectiveness in accurately detecting and monitoring liquid and gas flow in pipelines.