Capacitive probe for use in two-phase flows of electrically conductive aqueous fluids

Abstract

Two-phase flows take place when two different fluid components flow together in the same pipeline or equipment. They are observed in chemical, food, energy and petroleum industries, having important influence on many processes. The development of dedicated instruments for two-phase flows is a wide-open field for technological research. More specifically, capacitive probes are instruments used to measure and detect physical quantities of dielectric two-phase flows, mainly the volumetric concentration (or fraction) of one component. They are composed basically of two parts: a sensing section with electrodes composing a capacitor with guard and electric shield, and an electronic transducer circuit. They are robust, simple of handling, and do not request special safety care as X ray and gamma ray methods, and they are also of low relative cost. However, there are several technical challengers that still request research efforts to take them from laboratories to be widely used in the industries. One of them is the effect of the electrical conductance of fluid components on the response of capacitive probes, by affecting the internal electrical field distribution. Thus, theoretical and experimental studies are proposed in this work aimed on a technological solution of this effect on response of such probes. Simulations based on the Finite Element Method - FEM with a commercial software package will be performed, a capacitive sensing section on a Plexiglas pipe and the electronic transducer circuit suitable to operate with conductive fluids will be designed and mounted, and a sequence of experimental tests with saline water and air to evaluate the performance of the whole measurement system will also be performed. (AU)