Wire-mesh Sensor Research Articles

An HDTV-SB imaging algorithm for wire-mesh tomography

In multiphase flow detection, wire-mesh sensors are an important detection tool. However, the reconstructed image is heavily jagged due to the rectangular measurement of the sensor structure. In order to overcome this shortcoming, an higher degree total variation (HDTV) algorithm based on a total variation imaging algorithm is applied to the image reconstruction of a wire-mesh sensor. This algorithm uses the directional derivative in each direction as a regularity and is applied to the equation with the smallest residual. Combining the HDTV algorithm with a split Bregman (SB) algorithm, the calculation speed of the algorithm is accelerated and, finally, a HDTV-SB image reconstruction algorithm which can be applied to the Jacobian matrix is obtained. Subsequently, we performed static simulation experiments of complex flow patterns and compared them with some traditional algorithms. Experiments show that the image reconstruction quality of the HDTV-SB algorithm is higher than other algorithms. Finally, quantitative experiments are carried out on the two important parameters of the HDTV-SB algorithm. The results show that if the parameters are adjusted within a certain range, a one-step to two-step iteration can obtain a better reconstructed image.

Experimental study of pseudo-slug flow in upward inclined pipes

Pseudo-slug flow occurs between the slug and segregated flows and occupies a non-negligible area in the flow pattern map especially for gas condensate pipeline/wellbore where the liquid flow rate is low. An experimental study was conducted in a 3-in. flow loop with a valley configuration to investigate pseudo-slug flow characteristics using wire-mesh sensors, which include total average liquid holdup, liquid holdups in pseudo-slug body, and film region, respectively, pseudo-slug frequency, body length, and structure velocities.Comparison with conventional slug characteristics shows that pseudo-slugs have lesser liquid holdup in slug body, shorter body lengths, and smaller structure velocities. The pseudo-slug characteristics were also compared with predictions from existing correlations for conventional slug flows, as no correlation is available for pseudo-slug flow. The comparison shows poor agreement as expected, which necessitates the development of correlations for pseudo-slug flow specifically.The spatial evolution of pseudo-slugs is also discussed. Two initiation and dissipation mechanisms are described based on the location where pseudo-slugs are initiated and dissipated. In general, pseudo-slugs are shorter and slower near the inlet of uphill section compared the farther downstream locations in the uphill section.

New Algorithm to Discriminate Phase Distribution of Gas-Oil-Water Pipe Flow With Dual-Modality Wire-Mesh Sensor

Three-phase gas-oil-water flow is an important type of flow present in petroleum extraction and processing. This paper reports a novel threshold-based method to visualize and estimate the cross-sectional phase fraction of gas-oil-water mixtures. A 16×16 dual-modality wire-mesh sensor (WMS) was employed to simultaneously determine the conductive and capacitive components of the impedance of fluid. Then, both electrical parameters are used to classify readings of WMS into either pure substance (gas, oil or water) or two-phase oil-water mixtures (foam is neglected in this work). Since the wire-mesh sensor interrogates small regions of the flow domain, we assume that the three-phase mixture can be segmented according to the spatial sensor resolution (typically 2-3 mm). Hence, the proposed method simplifies a complex three-phase system in several segments of single or two-phase mixtures. In addition to flow visualization, the novel approach can also be applied to estimate quantitative volume fractions of flowing gas-oil-water mixtures. The proposed method was tested in a horizontal air-oil-water flow loop in different flow conditions. Experimental results suggest that the threshold-based method is able to capture transient three-phase flows with high temporal and spatial resolution even in the presence of water-oil dispersion regardless of the continuous phase.

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

In this article, we propose a novel ultrasonic technique to measure the gas void fraction in a liquid-gas intermittent swirling flow. The method converts the liquid film thickness measurement to a gas void fraction value considering a symmetrical flow pattern. We propose the use of the first echo peak instead of the standard maximum echo peak to estimate the liquid film thickness. The results are compared with a wire-mesh sensor, a reference for gas void fraction measurement, in a 1-inch inner-diameter vertical flow loop. A Root-Mean-Square-Deviation (RMSD) of 2.87% was observed between the proposed ultrasonic method and the reference sensor. An improvement of 6.06% if compared to the standard film thickness method (8.93%). The studied cases show that our method improves the use of ultrasound for gas void fraction measurement in a gas-liquid swirling flow.

Development of Wire Mesh Sensor for Measurement of Void Fraction Distribution in Refrigerant-Air Two Phase Flow

Development of Wire Mesh Sensor for Measurement of Void Fraction Distribution in Refrigerant-Air Two Phase Flow

Bio-Foam Internals for Potential Water Treatment Units Adapted to Marine Applications: Hydrodynamic Study

Reliance on harmless and renewable resources to mitigate process environmental footprint has become increasingly important for the design and operation of sustainable processes. One challenge that is prevalent in marine water surface contamination concerns treatment and recovery from oil spills where efforts are needed to design emergency units adapted to marine conditions. Potential candidates are naturally-grown porous loofa (bio-foam) materials which can be integrated in floating units transportable to the contamination area. For this purpose, a hexapod platform motion simulator was employed to emulate sea-driven floating movements of a column packed with two loofa bio-foam packings (dense and open-cell samples) and operated in cocurrent gas-liquid upflow mode. The column hydrodynamic behaviour was monitored by means of capacitance wire mesh sensors and electrical capacitance tomography for various inclination and rolling parameters. In the case of dense bio-foam packing, the relatively even distribution of gas and liquid in the vertical bed tended to degrade as the bed tilted up to 15°. Column rolling prompted fluid displacements in bed crosswise planes inducing notable amplitude oscillations of the local liquid saturation. Kerosene exhibited a strong foaming behavior with promotion of earlier inception of pulsing flow as a function of column inclination as compared to water.

Control of a Gas-Liquid Inline Swirl Separator Based on Tomographic Measurements

This text structures the application of Wire-Mesh sensors and Electrical Resistance Tomography in the control of an Inline Swirl Separator. It introduces a mechanistic model of the two-phase flow inside the device, which is linearized around an ideal perfect operation, and implemented in a Model Predictive Controller. The whole text is structured aiming at a future real application of the controller, briefly introducing the setup that is going to be used, the sensors and their working principles. The results obtained show a stable controller, able to regulate the process relatively fast in relation to the time resolution of the sensors. The positive response of the approach stimulates further improvements in the model developed, and the implementation of more sophisticated techniques to handle the non-linearities of the process.

Investigating the effect of pressure on a vertical two‐phase upward flow with a high viscosity liquid

AbstractThis article presents void fraction and pressure gradient data for sulfur hexafluoride (SF6) with gas densities of 28 and 45 kg/m3 and oil (with viscosity 35 times that for water) in a 127 mm diameter pipe. The superficial velocities of gas ranged from 0.1 to 3 m/s and those for liquid from 0.1 to 1 m/s, respectively. Measurements of void fraction data were recorded using a capacitance wire mesh sensor (WMS) system, which permits the 3D visualization of the flow patterns. All the data were obtained with a data acquisition frequency of 1,000 Hz. A differential pressure transducer was used to measure the pressure drops along the length of the pipe. The WMS provide time and cross‐sectionally resolved data on void fraction and from an analysis of its output, flow patterns were identified using the characteristic signatures of probability density function (PDF) plot of time series of void fraction. The PDF plots showed the single peak shapes associated with bubbly and churn flows but not the twin‐peaked shape usually seen in slug flows. This confirms previous work in larger diameter pipes but with less viscous liquids. For the bubble and churn flows investigated, the pressure gradient was observed to decrease with an increase in gas superficial velocity. Nevertheless, there was an insignificant observed effect of pressure on void fraction below certain transitional flow rates, the effect however became significant beyond these values. In the present work, wisps appear to be smaller, which might be due to the different fluid properties of the working fluids employed. In addition, wisps are easily revealed as long as there is a transition between churn and annular flows regardless of the pressure. Experimental data on void fraction and pressure gradient are compared against existing data. Reasonably good agreements were observed from the results of the comparison.

Assessment of the Resilience against Liquid Maldistribution of Monolith Packings under Offshore Floating Conditions

The study provides insights for adapting commercially available packings to work on floating vessels in the marine context aiming at preserving performances similar to land-based packed-bed reactors. Specifically, liquid distribution for cocurrent gas-liquid downflow (Ug = 0.0065-0.131 m/s and Ul = 0.001-0.0078 m/s) inside monolith packings embarked on a hexapod emulator was compared against glass-bead containing trickle bed and open-cell foam packings using wire-mesh sensors under vertical, inclined and rolling column conditions. Sensitivity of the tested internals with regard to liquid maldistribution was diagnosed and analyzed in terms of a maldistribution factor for the vertical/inclined and rolling columns. Liquid maldistribution was found to prevail at high gas and low liquid superficial velocities for the tested three packings regardless of column conditions. Monolith packed beds demonstrated superior robustness to counteract liquid maldistribution induced by bed static inclinations and roll motion...

Experimental Study of the Two-Phase Flow Patterns of Air-Water Mixture at Vertical Bend Inlet and Outlet

Air-water two-phase flow in pipes introduces a noticeable challenge due to the complexity of the fluids. Thus, to estimate the best design and reasonable financing cost of the transportation pipelines where the bends are presenting a part of their accessories, the investigators should have been able to estimate the flow regime occurring at different directions. An experiment was carried out by using a 90o bend fixed with two pipes where the flow was upstream from a vertical to a horizontal pipe which were representing the bend inlet and outlet respectively. Two wire-mesh sensors were used for obtaining the data of the void fractions (α) at water superficial velocities (Usl) which changed from 0.052 to 0.419m/s, and air superficial velocities (Usg) from 0.05 to 4.7m/s. Furthermore, the characterization of flow regimes of the air-water flow at both bend inlet and outlet were competed accurately by using void fraction analysis of the time series, Power Spectral Density (PSD), tomographic images observed by the sensor program, and the Probability Density Function (PDF) method. The flow regimes of vertical flow lines at the bend inlet were observed as bubbly, cap-bubble, slug, and churn flow, whereas the flow regimes of the horizontal flow line at the bend outlet were characterized as having stratified, stratified wavy, bubbly, plug, slug, wavy annular, and semi-annular flow due to the gravity and bend effects.

Detection of transient gas-liquid flow structures in horizontal shale gas well using wire-mesh sensor

Gas-liquid two-phase flows in shale gas well are characterized by extremely unstable motions. In this study, we proposed a new conductance wire-mesh sensor (WMS) operated in a mode of sinusoidal excitation, and designed a flow loop with multi-nozzle gas inlet to mimic the transient gas-liquid flows in horizontal shale gas well. The designed WMS was successively mounted at non-stationary and stationary sections along the pipe line to detect the transient flow structures. Flow pattern transitions at non-stationary and stationary sections are investigated according to the WMS flow visualizations. Notably, local structures of non-stationary gas-liquid flows are detected using the WMS. The results indicate that plug flows at non-stationary pipe section are characterized by wave bridge and pseudo slug, and local evolution characteristics of the wave bridge and the pseudo slug can dominate the initiation of slug flow.

Tracer dispersion in trickle beds under tilts and roll motions – CFD study and experimental validation

A wire-mesh sensor was used to measure the liquid residence time distribution (RTD) and tracer dispersion in trickle beds subjected to stationary tilts and roll motions. The measured tracer characteristics were confronted to three-dimensional transient Euler-Euler CFD simulations to expose the role of inclined and oscillating porous media. The simulation results satisfactorily reproduced the widening tracer signals with increased bed inclination reflecting in asymmetric RTDs prompted by permanent gravity-driven stratified flow zone through the packing. Similarly, tracer dispersion was predicted to increase for rolling beds by increasing tilt angle and motion period. While an increase of tilt angle shortened RTD breakthrough time due to the faster tracer stream evolving in the liquid-rich lower-most zones, tracer elution tended to slow-down with increasing the rolling period. In addition, it was revealed that with altering the column angular position during roll motions the fluid flow structures inevitably varied inside the packing leading to different mixing behaviors and residence time distributions.

A NOVEL METHOD FOR MEASUREMENT OF ELECTRIC FIELD IN EMULATED HUMAN BODY TISSUE USING WIRE MESH SENSOR

Wire mesh sensor has been successfully fabricated and used for measurement of the electric field in emulated human body tissue. Measurement of electric field in human body tissue needs to be done, because the electric field is very useful for the treatment especially cancer treatment and also important for health. In this study, we propose a novel electric field measurement method by using wire mesh sensor (wms), that is all channels on the wire act as receivers, and each cross point of the wire are interconnected. While in existing wire mesh sensors, there are two perpendicular channels of transmitter and receiver, and each channel is unrelated, there is a distance between the two channels. At present, wire mesh sensors 3 × 3 and 8 × 8 were used to measure the value of electric field at each wire intersection point. The wire mesh sensor consists of copper wire in a cylindrical body model with diameter 14 [cm]. The emulated human body tissue were inserted in the wire mesh sensor. Furthermore, linear back propagation technique and bilinear interpolation used for image reconstruction of the electric field distribution. The result showed that the wire mesh sensor 8 × 8 has better resolution than wire mesh sensor 3 × 3. The characterisation of wire mesh sensor 8 × 8 for measurement of electric field in emulated human body tissue is obtained lower than measurement in the air with a ratio of 82%. Meanwhile, the wire mesh sensor 3 × 3 could be achieved at 61.8%. This study can be a new science in measuring electric field so that electric field-based treatment planning system can be more optimal.

Complex Network Analysis of Wire-Mesh Sensor Measurements for Characterizing Vertical Gas–Liquid Two-Phase Flows

Gas–liquid two-phase flows widely exist in industrial production, where understanding the dynamics underlying flow patterns is a challenging problem of great significance. In this brief, we propose a complex network framework for analyzing the wire-mesh sensor measurements, aiming to characterize the flow behavior in the transition from bubble flow to slug flow in a 50 mm-inner-diameter vertical pipe. In particular, we design a wire-mesh sensor system and carry out the gas–liquid two-phase flow experiments to acquire the local flow signals from different flow conditions. We infer a complex network from wire-mesh sensor measurements in terms of the mutual information between time series, and then calculate some network measures to quantitatively characterize the network topological features associated with flow behavior. We find that the networks corresponding to different flow patterns show different topological features, which allows us to characterize the transition of flow behavior. Our results suggest that the proposed analytical framework can effectively reveal the complex dynamical behavior of gas–liquid two-phase flows.

Imaging of a distinctive large bubble in gas–water flow based on a size projection algorithm

Although electrical resistance tomography has been successfully applied to visualise gas–water two-phase flow in many applications, its capability for the determination of the sharp interfaces between gas bubbles and water is still below engineering expectations, which impedes effective estimation of fluid characteristics and flow regimes. A thresholding value method applied to a tomogram demonstrated a splendid view of most flow regimes, especially of a large bubble, but it may present a challenge with its accuracy in practice since the thresholding value was determined empirically. In this paper, a size projection algorithm is proposed for imaging a large bubble with a distinctive boundary, where the optimal thresholding value is automatically determined by minimising the projection error between measured voltages and computed voltages via a forward numerical solution, which specifically focuses on imaging of large bubbles. The accuracy of imaging a large bubble is evaluated by simulating the typical cross-sectional configurations of common pipeline flow regimes. Experimental results are reported in the paper, which were conducted on both horizontal and vertical pipelines engaged with typical gas–water flow regimes, including stratified, plug, slug and annular flow regimes. The results are also compared with the images obtained from a wire-mesh sensor system and high-speed camera videos recorded through a transparent photo-chamber lined in the test rig.

A new objective and distribution-based method to characterize pseudo-slug flow from wire-mesh-sensors (WMS) data

The subjective nature of intermittent (slug/pseudo-slug) flow characterizations has limited the reproducibility and consistency among independent datasets and may contribute to the perceived poor performance of available closure relationships. This deficiency is more critical for pseudo-slug flow where pseudo-slug body and film regions are not easily differentiable. This paper proposed an objective method to characterize pseudo-slug flow based on time-trace signal (time-series) of wire-mesh-sensors (WMS) data. Primarily, the front/tail threshold values and disregard film criteria are selected based on the distribution benchmarking of holdup and film length, respectively.The proposed method is validated qualitatively and quantitatively. The eye-test qualitatively shows that the proposed method is capable of identifying the pseudo-slug front consistently. The end of pseudo-slug is located in the middle of the tail region, where holdup gradually decreases from pseudo-slug (HLPS) to film (HLF) holdup. This behavior is physically intuitive as the tail region consists of both upward (similar to pseudo-slug body) and backward moving liquid bodies (similar to liquid film). Quantitatively, the variables measured with the proposed method, namely: pseudo-slug frequency (fPS), structure velocity (vTPS), body length (lPS), body holdup (HLPS), and film holdup (HLF), demonstrate self-consistency within the framework of unit cell model, thereby indicating conformance to the continuity equation of intermittent flow.

Fuzzy flow pattern identification in horizontal air-water two-phase flow based on wire-mesh sensor data

Online monitoring of two-phase flow patterns is an essential need in various chemical engineering applications, since the reliability of prediction methods is limited. Therefore, the present study aims at developing a practically applicable algorithm for identifying flow patterns in horizontal gas-liquid flows on the basis of wire-mesh sensor data. Experiments were conducted in a 50 mm i. d. pipe over a wide range of superficial velocities of an air-water mixture. Characteristic features involving the influence of gravity and the spatio-temporal behavior of the flows were derived from tomographic phase fraction data and used as input for fuzzy clustering. Three differently determined sets of cluster centers are compared against a reference classification by human specialist through reclassifying the measurements with the aid of defuzzyfication and, alternatively, by means of a novel visualization technique, that retains the fuzziness of the results. With respect to the latter one, best agreement is reached with cluster centers from fuzzy c-means clustering using all recorded measurements. As a special emphasis is put to the identification of transitional flow patterns, the performance of the algorithm at pseudo-dynamic operation is demonstrated, finally.

Pressure Effects on Low-Liquid-Loading Oil/Gas Flow in Slightly Upward Inclined Pipes: Flow Pattern, Pressure Gradient, and Liquid Holdup

Summary This paper studied the effects of system pressure on oil/gas low–liquid–loading flow in a slightly upward inclined pipe configuration using new experimental data acquired in a high–pressure flow loop. Flow rates are representative of the flow in wet–gas transport pipelines. Results for flow pattern observations, pressure gradient, liquid holdup, and interfacial–roughness measurements were calculated and compared to available predictive models. The experiments were carried out at three system pressures (1.48, 2.17, and 2.86 MPa) in a 0.155–m–inside diameter (ID) pipe inclined at 2° from the horizontal. Isopar™ L oil and nitrogen gas were the working fluids. Liquid superficial velocities ranged from 0.01 to 0.05 m/s, while gas superficial velocities ranged from 1.5 to 16 m/s. Measurements included pressure gradient and liquid holdup. Flow visualization and wire–mesh–sensor (WMS) data were used to identify the flow patterns. Interfacial roughness was obtained from the WMS data. Three flow patterns were observed: pseudo-slug, stratified, and annular. Pseudo-slug is characterized as an intermittent flow where the liquid does not occupy the whole pipe cross section as does a traditional slug flow. In the annular flow pattern, the bulk of the liquid was observed to flow at the pipe bottom in a stratified configuration; however, a thin liquid film covered the whole pipe circumference. In both stratified and annular flow patterns, the interface between the gas core and the bottom liquid film presented a flat shape. The superficial gas Froude number, FrSg, was found to be an important dimensionless parameter to scale the pressure effects on the measured parameters. In the pseudo-slug flow pattern, the flow is gravity–dominated. Pressure gradient is a function of FrSg and liquid superficial velocity, vSL. Liquid holdup is independent of vSL and a function of FrSg. In the stratified and annular flow patterns, the flow is friction–dominated. Both pressure gradient and liquid holdup are functions of FrSg and vSL. Interfacial–roughness measurements showed a small variation in the stratified and annular flow patterns. Model comparison produced mixed results, depending on the specific flow conditions. A relation between the measured interfacial roughness and the interfacial friction factor was proposed, and the results agreed with the existing measurements.

Robust computational framework for wire-mesh sensor potential field calculations

With the development of the next generation of nuclear reactor safety system codes fast underway, increased importance has been placed on enhancing physical closure correlations and amassing representative benchmark-quality experimental data for validation purposes. Wire-mesh sensors, a reputable experimental measurement technique with sufficient spatial and temporal resolution to serve such goals, and related data reconstruction algorithms have been the subject of renewed interest as researchers attempt to characterize their measurement uncertainty. To assist in such investigations, the present work establishes a comprehensive numerical framework with which to quantify the electric potential field around wire-mesh sensors. Using the finite-volume foundations of OpenFOAM, a numerical solution algorithm is developed to predict the transmitted electric current between transmitter and receiver electrodes for both homogeneous and heterogeneous electrical conductivity fields. A detailed verification against seminal numerical calculations and robust validation procedure is included to ensure the accuracy of the proposed methodology. Parametric studies of spherical bubble diameter, lateral crossing position, and spheroidal shape influence are conducted to provide preliminary insights into wire-mesh sensor operation and the suitability of various calibration approaches. Observed trends in the transmitted currents reveal overshoots relative to calibration conditions, which are fundamentally linked to the maldistributed electric potential field in heterogeneous bubbly flows. The present investigation offers a vital first step towards a comprehensive multi-physics model of multiphase flow around a wire-mesh sensor.

Analysis of flow pattern transition from segregated to slug flow in upward inclined pipes

Segregated and slug flows are two of the most common flow patterns encountered in two-phase upward inclined pipe flow. However, the transition between them is ambiguous. Coherent and distinctive structures have been observed within the transition. These structures have been classified as pseudo-slug flow. The nature of pseudo-slug flow is not well understood due to the complexity of the structure. At low liquid loading conditions, this flow pattern can occupy a large operating region and cannot be neglected. This paper presents a detailed experimental work conducted in a facility with a valley configuration, focusing on the transition region between segregated and slug flows. Wire-mesh sensors were employed to investigate the liquid phase distribution within the flow structure.The current paper investigates the flow patterns and their transition in upward inclined pipe from different perspectives. The investigation includes analysis of images from high-speed videos, evaluation of 2-D liquid holdup axial evolution, 2-D liquid holdup distribution at pipe cross-section, 3-D interfacial structure evolution, and analysis of pressure gradient and liquid holdup measurement, flow characteristics, etc. Differences between slug and pseudo-slug flows are also presented.Three superficial liquid velocities (0.001, 0.005 and 0.01 m/s) and five inclination angles (2°, 5°, 10°, 15°, and 20°) are studied. Simplified correlations are proposed for pseudo-slug structural velocity, showing fair agreement.