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In the present work, local oil holdup in oil-in-water emulsion flows is experimentally investigated with multiple mini-conductance probes. With the aid of finite element method (FEM), we firstly optimize the geometry structure of a mono-sensor conductance probe through the examination on its electrical and sensitivity field distribution. Thereafter, multiple mini-conductance probes composed by 16 mono-sensor probes are designed for a vertical upward pipe with 20 mm inner diameter (ID). The flow conditions regarding pipeline flows of oil-in-water emulsion are set within low velocity (0.0184–0.2576 m/s) and high water-cut (80–96%). By processing the fluctuating signals of multiple mini-conductance probes, we derive oil holdups on different positions at pipe cross section. Accordingly, oil holdup distribution at the whole pipe cross section is acquired using cubic spline interpolation, and correspondingly the slippage effect between oil and water phase is analyzed. The research results indicate that local oil holdup distribution is susceptible to the variation in mixture velocity and water-cut. Furthermore, the degree of inhomogeneous distribution in local oil holdup presents the weakest under the conditions of high mixture velocities as well as high water-cuts. Finally, a complexity measure designated as weighted-permutation entropy is extracted from the fluctuating signals of multiple mini-conductance probes to characterize the evolution in oil holdup distribution from the perspective of nonlinear dynamics. [ABSTRACT FROM AUTHOR]

This paper is devoted to measuring water holdup of oil-water two-phase flow with low velocity using a coaxial capacitance sensor. We first investigated the distribution characteristics of the coaxial capacitance sensor via the finite element method (FEM) and optimized its geometry size. Afterward, we carried out a vertical upward oil-water two-phase flow experiment in a pipe with a 20-mm inner diameter (ID) to obtain the responses of four flow patterns: transition flow (TF), dispersed oil-in-water slug flow (D OS/W), dispersed oil-in-water flow (D O/W) and very fine dispersed oil-in-water flow (VFD O/W). The sensor outputs were normalized to equivalent water holdup and compared with the set values from a quick closing valve (QCV) method. Finally, we studied the time-frequency dynamic characteristics of different flow patterns based on the Adaptive Optimal Kernel Time-Frequency Representation (AOK-TFR) algorithm to further analyze the evolution of oil-water two-phase flow with low velocity. The results show that the coaxial capacitance sensor can be effectively applied in the measurement of water holdup under moderate and low water-cuts as well as uncovering discrepancies regarding different flow patterns. [ABSTRACT FROM AUTHOR]