A flowmeter for measuring the dispersed phase velocity in multiphase flow with non-uniform velocity profiles

Abstract

This study aims to introduce a new technique to measure the velocity distribution of the dispersed component of a vertical, upward, water continuous two-phase pipe flow. Here, it is proposed that measurements of the variation in the local conductance of the mixture can be cross correlated to determine the local velocity distribution of, for example, gas bubbles in water. The measurements were conducted by using arrays of axially separated conductance sensors placed normal to the flow. Each array contained eight electrodes distributed over the internal circumference of the pipe carrying the flow. The arrays, were mounted at a known distance from each other along the pipe. Within each array, individual electrodes could be configured as either ‘excitation’, ‘measurement’ or ‘earth’. By changing the electrode configuration of an array the electric field sensitivity distribution associated with the array could be altered, thus changing the region of the flow ‘interrogated’ by the system. By cross correlating the output signals from these arrays, in various combinations, the velocity of the dispersed phase can be obtained at different regions within the flow, thereby enabling the velocity profile of the dispersed phase to be measured. The sensitivity distribution associated with given electrode configurations has been investigated in a bench test. First the flow meter was filled with water, and then nonconducting rods were inserted into the flow meter at various spatial locations parallel to the pipe, the resulting change in conductance was measured.. The sensitivity distribution has also been simulated using COMSOL software. Agreement between experiment and theory was close to 1 %.