Multiple Wire-Mesh Sensors Applied to the Characterization of Two-Phase Flow inside a Cyclonic Flow Distribution System

Abstract

Wire-mesh sensors are used to determine the phase fraction of gas–liquid two-phase flow in many industrial applications. In this paper, we report the use of the sensor to study the flow behavior inside an offshore oil and gas industry device for subsea phase separation. The study focused on the behavior of gas–liquid slug flow inside a flow distribution device with four outlets, which is part of the subsea phase separator system. The void fraction profile and the flow symmetry across the outlets were investigated using tomographic wire-mesh sensors and a camera. Results showed an ascendant liquid film in the cyclonic chamber with the gas phase at the center of the pipe generating a symmetrical flow. Dispersed bubbles coalesced into a gas vortex due to the centrifugal force inside the cyclonic chamber. The behavior favored the separation of smaller bubbles from the liquid bulk, which was an important parameter for gas-liquid separator sizing. The void fraction analysis of the outlets showed an even flow distribution with less than 10% difference, which was a satisfactorily result that may contribute to a reduction on the subsea gas–liquid separators size. From the outcomes of this study, detailed information regarding this type of flow distribution system was extracted. Thereby, wire-mesh sensors were successfully applied to investigate a new type of equipment for the offshore oil and gas industry.

Void Fraction Measurement in a Gas-Liquid Swirling Flow Using an Ultrasonic Sensor

“…Figure 11 shows the wire-mesh 3D void fraction data of some representative swirling flow tests in this work (graphics are horizontal, but the actual flow is vertical oriented). For details on this data processing, the reader is referred to [8]. As an intermittent flow, it is possible to identify the aerated liquid slug (thinner gas volume) and elongated bubble structures (thicker gas volume) but in a swirling motion.…”

“…Figure 6 shows the flow map of [26] for the vertical 1-inch pipe for water and air. The intermittent swirling flow pattern generated can be found in detail in other works [8], [27]. The test cases, highlighted with dots, are located at slug or slug/dispersed bubbles flow transition area.…”

“…Additionally, the droplets are separated from the gas, increasing the liquid film thickness [10]. This behavior occurs in all upward vertical flow patterns such as bubbly and slug [8] [11], churn [10]- [12], and annular flow [13]. The studies show that with sufficient superficial liquid and gas velocities at the input of the swirler, the generated swirling flow characteristics do not depend on the flow regime.…”

“…where the voltage readings V are proportional to fluids' electrical permittivity, (i,j) are wire indices, and k is the discrete temporal index (for details see [8] and [24]). By appropriate processing of the matrix α, it is possible to visualize the data in different ways, for instance, averaged one-dimensional time series, time-averaged 2D images, as well as three-dimensional contour images, as was described in our previous work [8] and was also applied here. According to [25], WMS presents a void fraction uncertainty of ±10.5% over a variety of flow regimes relative to other methods such as radioactive methods.…”

“…This type of flow is characterized by a swirling liquid film on the pipe wall and a swirling gas flow at the center of the pipe. This condition is explored in applications such as heat exchangers [2], steam separators [3], gas-liquid separators [4]- [7], and multiphase flow distribution systems [8] [9]. The swirling motion promotes the gas accumulation in the center of the pipe due to the pressure gradient in the radial direction.…”