Dependence of the instantaneous response of impedance probes on the local distribution of the void fraction in a pipe

Abstract ln a vertical pipe of circular cross-section the instantaneous response of an impedance probe which has its electrodes mounted flush in the tube wall to avoid disturbing the two-phase flow, depends on the void-fraction distribution. Different probe geometries (different widths and numbers of electrodes) and different a.c. supplies were studied to minimize the influence of this parameter. With single-phase a.c. supply the electrodes of intermediate width yield the best results. An increase from two to four electrodes, does not entail any improvement, whatever the kind of electrode connection. With a six-phase a.c. supply, such that a rotating electric field is obtained within six electrodes, the results are better than those obtained with two electrodes of intermediate width supplied with single-phase current.