Phase identification by a novel needle-contact capacitance probe in gas-liquid two-phase flows

In this paper, we propose a novel probe to identify phases in any two-phase flows where one phase is conductive and the other nonconductive. We can further obtain many parameters such as void fraction, bubble velocity, and interfacial area concentration. Compared with the traditional probe, the novel probe has unique advantages that it is less dependent on water conductance or distance between the electrodes, and that the amplitude is bigger between high and low levels. Theoretical analyses showed that the measurement error became higher when water conductance decreases or distance increases, which is consistent with the theoretical analyses. Experimental results showed that the output signal kept constant with salt content of 0-5% and electrode distance of 0-30 mm in tap water. The level difference was up to 6.4 V, resulting in identifying two phases easily. Time traces of phase identification were completely consistent with the flow structures.