Multimodal Two-Phase Flow Measurement Using Dual Plane ECT and GRT

Abstract

The present work assesses the accuracy two phase flow measurement, based on cross-correlation and cross-spectrum velocity computation, using dual plane non-intrusive Electrical Capacitance Tomography (ECT), over a broad spectrum of horizontal flow configurations, combined with fraction distribution measurements from Gamma-ray Tomography (GRT). The measurement of two-phase flow encompasses the measurement of both the velocity and the phase concentration of the flow components. The accuracy of the flow velocity is still an open discussion and remains a key challenge in the field of multiphase flow measurement. The velocities of the two-phase components vary, both in between them, and across the pipe cross-section. This study assesses the use of cross- correlation techniques as methods for calculating the cross-sectional velocity distribution by deriving the transit time of the fluid flowing through two parallel ECT sensor arrays mounted on the perimeter of a pipe. The spectral distribution of the velocities is assessed for improved accuracy of individual component velocities. A dual-plane ECT is adopted for the velocity measurements and are combined with state-of-the-art density-based cross-sectional phase fraction distribution from a GRT system to measure the volumetric flow rates of the two phases. The results show that the cross-spectrum method provides enhanced velocity estimation for both flow phases over the conventional cross-correlation technique. Further improvement was reported using a simple predictive correction model resulting in flowrate estimation accuracy of ±10%.The method for two-phase flow measurement suggested in this work leverages the accuracy of the tomography systems on accurate fraction measurement and fast data acquisition to lead to potential enhancement in process control by enabling a more accurate prediction of components velocities.