Two-phase Flow Measurement Research Articles

A New Model for Measurement of the Droplet Size and Volume Fraction in Air–Droplet Two-Phase Flow Based on Ultrasonic Attenuation Method

Ultrasonic attenuation method has great advantages in the measurement of particle two-phase flow. Most of the existing ultrasonic attenuation theoretical models are suitable for the two-phase flow where the continuous phase is liquid or the particle phase is solid, and different models are aimed at the different particle size range, which makes them limited in practical applications. To solve the above problems, a new ultrasonic attenuation theoretical model, which combines McClements model and Bouguer–Lambert–Beer-Law (BLBL) model (MCBL model), is proposed for air–droplet two-phase flow. It extends the droplet size range to make it not affected by frequency and suitable for all wavelength regimes. In addition, the ultrasonic propagation process in air–droplet two-phase flow is simulated based on COMSOL. The simulation ultrasonic attenuation results are compared with the existing theoretical models and MCBL model. Besides, the simulation ultrasonic attenuation results are inversed by the MCBL model and hybrid particle swarm optimization (HPSO) algorithm, and the error is within ±8%. Furthermore, the flowing experiment is carried out to measure the ultrasonic attenuation coefficient of air–droplet two-phase flow. The experimental results are also inverted using the proposed MCBL model and HPSO algorithm to obtain the droplet size and volume fraction. Compared with the results of the image method, the error is less than 15%, which verifies the applicability and practicability of the MCBL model proposed in this article.

Measurement of void fraction in pipes by nuclear transmission based techniques

In this study, the application of nuclear transmission based techniques to the measurement of two-phase flow was evaluated and the experiment setup was described. Because neutrons are appreciably affected by interaction with hydrogen atoms, techniques based on transmission of thermal and fast neutron are particularly suitable for use with water or any other hydrogenous fluids. Based on the effective of water for gamma-rays attenuation on mass basis, transmission technique based on measuring of total gamma-rays has been examined. The beams of fast neutrons, thermal neutrons and gamma-rays emitted from 252Cf neutron source of strength 1.3 × 107 n/s were used. Void fraction is measured for steady-flow regimes in a horizontal air–water flow. Results are evaluated and the strength and limitations for each technique are given and discussed.

Measurement of pressure loss throughout a clogged steam generator tube support plate in two-phase flow

Two-phase flow head losses across tube support plates in U-bend tube steam generators are classically evaluated from single phase head losses duly modified with a correction factor to account for two-phase effects.This communication reports upon a series of experiments to feed head loss models for clogged tube support plates under two-phase flow. By using a classical approach, a single phase head loss model is used together with a two-phase flow multiplier. The experiments cover a large span of clogging levels, up to the unrealistic limit case of 95% of clogging.Singular head loss due to the tube support plate is measured under single-phase flow for clean and clogged plates. The head loss factor is hence evaluated and compared to the prediction of some available models. Then the same experiment is repeated under two-phase flow condition. By combining the previously measured single-phase factor with the two-phase flow measurements, recommendations for predicting two-phase flow multiplier with existing models are given.

Electromagnetic-conductance measurement method for the flow rate and void fraction of gas-liquid two-phase flows

Gas-liquid two-phase flow systems are widely existed in many engineering systems and industrial processes, and measurement techniques for two-phase flows are crucial in a diverse range of engineering applications. Most of the existing measurement techniques usually brought extra resistance to the flow in the branch pipes and, to some extent, influenced the original distribution of the gas-liquid two-phase flows in the parallel T-junction system. In order to study the distribution characteristics of two-phase flow in vertically parallel T-junctions, the electromagnetic-conductance measurement method was developed to measure the void fraction and liquid flow rate of the gas-liquid two-phase flow in the branch pipes. Electromagnetic-conductance measurement technique has the advantages of high response rate, satisfactory accuracy and low disturbance on the flow field of gas-liquid two-phase flows. In order to calibrate the conductance measurement method, experiments were carried out with the liquid velocity range of 0.2–2 ​m·s-1, the gas velocity range of 0–50 ​m·s-1 and the volume void fraction range of 0–0.99. Through the calibration experiments, the relationship between the resistance value of each conductivity sensor and the volume void fraction of two-phase fluid was decided to be established as a logistic function. By the error analysis of the calibration results, 75.9% of experimental results of the void fraction in the gas-liquid two-phase flow fell within the ±20% error bands. The electromagnetic-conductance measurement method proposed in this paper could provide a reference for accurate and non-interference measurement of two-phase flow in parallel T-junctions.

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

This work assesses the accuracy of two-phase flow measurement, based on cross correlation (XC) and cross-spectrum (CS) velocity computation, using dual plane nonintrusive 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 XC 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 is 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 CS method provides enhanced velocity estimation for both flow phases over the conventional XC 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.

Characteristics of horizontal gas-liquid two-phase flow measurement in a medium-sized pipe using gamma densitometry

Two-phase flows are common occurrences in many industrial applications. The understanding of their characteristics in industrial piping systems is vital for the efficient design, optimization, and operation of industrial processes. Most of the previous experimental studies involving the use of gamma densitometers for holdup measurements in air-water mixtures are limited to smaller diameter pipes (generally regarded as those with < 50 mm in nominal diameter). Further, very few literature report experimental data obtained using gamma desitometers. This paper presents an application of a gamma densitometer in the measurement of two-phase flow characteristics in an intermediate diameter pipe (nominal diameter between 50 mm and 100 mm). Scaled air-water experiments were performed in a 17-m long, 0.0764-m internal diameter horizontal pipe. Liquid superficial velocity ranged between 0.1–0.4 m/s while gas superficial velocity ranged from 0.3 to 10.0 m/s. The measured parameters include liquid holdup, pressure gradient, flow pattern, and slug flow features. The flow patterns observed were stratified, stratified-wavy, plug, slug, and annular flows. Plug and slug flow patterns showed good agreement with established flow pattern maps. Furthermore, the slug translational velocity was observed to increase with increasing mixture velocity, as reported by previous authors, hence establishing the reliability of the instrumentation employed. The slug body length was also measured using the gamma densitometer and was found to be within the range 24–36D with a mean length of 30.6D.

Wellbore fluid sonic conditions during blowouts

The understanding of high-velocity two-phase flow is critical for predicting worst-case discharge scenarios. During a blowout, the fluid discharge rate can be very high, and its velocity may reach the sonic speed at the surface. Therefore, it is crucial to understand the fluid dynamics and flow characteristics of multiphase flow in the high-velocity range. In this investigation, two-phase (air-water) flow experiments were conducted to study the flow evolution in extreme high-velocities occurring during worst-case discharge. The experiments were performed in a vertical pipe section with a diameter of 83 mm and a length of 5.5 m. A fully transparent viewport was installed on the test section to monitor the flow pattern. The superficial gas velocities were ranging approximately from 8 to 160 m/s. During the test, the pressure gradient was monitored while increasing the gas rate at a constant liquid rate. Under subsonic conditions, the pressure gradient increase with superficial gas velocity indicating the establishment of friction dominated flow regime. However, the pressure-gradient trend changed when shock waves formed in the test section. With increasing the superficial gas velocity at a given liquid rate, the pressure gradient attained its maximum when flow transition occurred and shock waves formed in the test section, which were observed through the viewport. Under sonic conditions, increasing the superficial gas velocity a constant liquid flow rate reduced the pressure-gradient.After examining various two-phase flow sonic velocity models and measurements, a new correlation has been developed to predict sonic conditions during worst-case discharge. Experimental results are compared with predictions of existing wave propagation models and demonstrated reasonable agreement. Subsequently, a computational tool has been developed to estimate fluid flow rates for worst-case discharge scenarios involving sonic flow conditions. The new correlation has been implemented in the computational tool to forecast the establishment of sonic flow conditions in the wellbore. The computational tool shows a reasonable agreement with commercial packages for basic worst-case discharge circumstances. A sensitivity analysis performed using the computational model suggests that the discharge rate varies with the in-situ parameters such as skin factor, pay-zone height, and reservoir permeability.

Real-time enthalpy measurement of two-phase geothermal fluid flow using load cell sensors: Field testing results

Field testing data from five different wells using load cell sensors were analysed to investigate their possible application for estimating geothermal two-phase fluid enthalpy. Two different data analysis approaches - measuring the liquid phase velocity and estimating the dryness fraction - were examined. The liquid velocity was predicted successfully using the cross-correlation technique. However, liquid velocity cannot be used alone to measure the fluid enthalpy without slip ratio and void fraction. It was only possible to calculate the dryness fraction estimate from the weight of the pipeline for one data set due to measurement noise and the results were found to be of low quality. The remaining technical challenges and recommendations are discussed.

Theoretical study and experimental measurement of the gas liquid two-phase flow through a vertical Venturi meter

An accurate two-phase flow rate measurement is essential in many applications and industries such as; oil/gas, chemical, pipeline transportation and nuclear industry. This paper presents the findings obtained from two-phase flow rate measurements using Venturi meters coupled with conductance probe sensors. The measurement system and presented methodology can be used to directly and continuously measure the mass flow rate of gas-liquid flows without any need for using a separator. Most of the available data in literature on mass flow rate using Venturis in gas-liquid two phase flows are limited/valid to a certain flow regime. However, the experimental data presented in this paper covered a wide range of flows (i.e. bubbly, slug and churn flows). Three Venturis with different diameter ratios, β = 0.40, β = 0.55 and β = 0.75 have been employed using an air-water vertical test section. The effect of the Venturi’s geometry on the flow behaviour was also evaluated. The average void fraction and void fraction time series have been measured along the test section by nine different conductance probe sensors covering the convergent, throat and divergent sections. In addition, the two-phase pressure drop across the Venturi was measured. Moreover, a new correlation for the gas-liquid slip ratio was proposed in this paper, which is necessary for calculating the two-phase mass flow rate. The proposed slip ratio correlation showed more accuracy than the ones available in literature. It was found that the correlation proposed by Chisholm to predict the two-phase mass flow rate in Venturis with a diameter ratio, β = 0.55, shows the best accuracy among others such as; Murdock, Lin, James and Zhang correlations.

The Performance Characteristics of Electromagnetic Flowmeter in Vertical Low-Velocity Oil-Water Two-Phase Flow

Since the responses of the electromagnetic flowmeter (EMF) can be affected by the flow characteristics, the combination of the EMF and the void fraction meter is always necessary for the two-phase flow measurement. Combined with a plug-in conductance sensor array (PICSA), the measurement characteristics of the EMF in low-velocity oil-water two-phase flows are investigated in this study. In a low-velocity oil-water flow experiment, the water holdup of the oil-water flows at low velocity is measured by the PICSA. By introducing correction coefficients of the EMF under different flow patterns, the correlations between the EMF responses and the oil holdup are established to measure the water superficial velocity. Finally, the oil superficial velocity is accurately predicted by a drift flux model derived from the liquid holdup and mixture velocity. Satisfactory prediction accuracy for the oil superficial velocity can be achieved without the need to introduce oil velocity measurement as in previous studies.

Experimental investigation of gas-liquid two-phase splitting in parallel pipelines with risers

To study two-phase flow splitting at a T-junction, Parallel vertical riser pipelines were set up in the laboratory. Each of these pipelines was completely symmetrical. The experiment was conducted with various combinations of gas velocity and liquid velocities. Accurate measurement of gas-liquid two-phase flow were performed to determine whether the two-phase flow was evenly distributed in the two riser pipelines. The conductance probe technique was used to measure the average liquid holdup in the cross section of the pipe. Three flow patterns in two risers were observed during the experiment: slug-slug (S-S), churn-churn (C-C), and churn-slug/churn (C-SC). Gas-liquid flow of S-S and C-SC is asymmetric, while that in C-C is symmetric. When the flow state in the two risers is S-S, the gas-liquid two-phase split could be uneven. When the gas and liquid velocities were sufficiently high for sustaining C-C, the gas and liquid were split evenly. The last state was the transition state between S-S and C-SC. A model based on pressure-minimization was established to predict two-phase flow splitting. The measured and predicted flow splits were observed to be in agreement.

Preliminary study on three-dimensional imaging of cryogenic two-phase flow based on electrical capacitance volume tomography

The potential application of electrical capacitance volume tomography (ECVT) to the liquid nitrogen-vaporous nitrogen two-phase flow measurement is evaluated by numerical experiment. The Landweber iteration is taken as the inversion algorithm which derives the reconstructed images. Eight types of ECVT sensor structures are tested and the accuracy of the reconstructed images is compared to evaluate the quality of the sensor structures. Especially, the effect of the axial guard electrodes is analyzed and discussed. The anti-noise ability of the optimal structure is also determined by calculating seven different phase distribution cases. The results demonstrate that the shifted plane and the axial guard electrode in ECVT sensor are helpful for image reconstruction quality. The layer number of ECVT sensor influences the reconstructed images a lot while the shape of the electrode has little effect on it. ECVT also shows a certain anti-noise ability under the noise level of 60 dB and 55 dB.

Sectional void fraction measurement of gas-water two-phase flow by using a capacitive array sensor

The sectional void fraction measurement for multiphase flow is usually influenced by flow patterns. Inspired by electrical capacitance tomography (ECT) devices applied to flow imaging (whose measured capacitance data contain both the flow pattern and sectional void fraction information), a capacitive array sensor is developed to realize two functions, flow pattern recognition and void fraction measurement, simultaneously; so that the void fraction measurement can be conducted for a certain flow pattern and the measurement accuracy can be expected to be improved. The main idea of the proposed method can be described as: firstly, the proper feature vectors are extracted from the electrical signal to identify the flow pattern (the BPNN model with GDX learning algorithm is used for flow pattern identification); and then the average of electrical signal is applied to estimates the void fraction by the corresponding calibration curve. An experimental platform of air/water two-phase flow is built (on which 3 flow patterns can be generated stably) to test the performance of the proposed method. The results support the correctness and effectiveness of the proposed method.

Optical Fiber Transducer for Monitoring Single-Phase and Two-Phase Flows in Pipes

Fluid flow monitoring is essential in many industrial processes. However, some flow measurement methods may not be feasible in a few applications such as the ones in potentially explosive atmospheres or under presence of intense electromagnetic fields. In this study, we present the construction and evaluation of an optical fiber transducer, which is suitable for flow monitoring in industrial environments pipes. Besides single-phase flow, which has been already monitored by similar techniques in the past, we also present in this paper the measurement of two-phase gas-liquid flows. Working principle is based on the measurement of the force induced by the streaming fluid into a cantilever whose deformation is indirectly and optically monitored by means of fiber Bragg gratings. Static and dynamic tests were performed for transducer calibration and validation. In static calibration, sensor sensitivity to force corresponded to 2.34 nm/N. The transducer was successfully applied to measure single-phase flow rate in the range of 0 $\text{m}^{{3}}$ /h to 6.68 $\text{m}^{{3}}$ /h, presenting maximal uncertainty of 0.3 $\text{m}^{{3}}$ /h. Finally, the transducer was applied in two-phase gas-liquid flow, being able to correctly identify gaseous and liquid phases since the cantilever is exposed to different forces during the passage of the gas and liquid. In this way, the developed transducer may be well applied to two-phase flow monitoring.

New method for bubble/slug velocity measurement in small channels.

Based on the C4D technique and cross correlation velocity measurement technique, a new method for bubble/slug velocity measurement of the gas-liquid two-phase flow in small channels is proposed. A new C4D sensor, which is suitable for the parameter measurement of the gas-liquid two-phase flow in small channels, is developed by introducing the principle of capacitive reactance elimination. With two new C4D sensors, a bubble/slug velocity measurement system is developed, and the bubble/slug velocity is determined by the cross correlation velocity measurement technique. To verify the effectiveness of the proposed bubble/slug velocity measurement method, three prototypes of bubble/slug velocity measurement systems with different diameters (1.82 mm, 2.65 mm, and 2.96 mm, respectively) were established, and the bubble/slug measurement experiments were carried out. The research results show that the capacitive reactance elimination is an effective way to overcome the unfavorable influence of the coupled capacitances on measurement results. The experimental results indicate that the proposed method can successfully realize the bubble/slug velocity measurement in small channels, and the velocity measurement accuracy is satisfactory. For the three prototypes of the bubble/slug velocity measurement system, the maximum relative errors of the bubble/slug velocity measurement are all less than 5%.

Gas-liquid two-phase flow measurement by combining a Coriolis flowmeter with a flow conditioner and analytical models

Abstract In oil-gas fields, two phase flow measurement of liquid-gas mixture for the whole Gas Void Fraction (GVF) range remains a challenging task. Coriolis flow meter is proven to be one of the most accurate device for single phase flow measurement. However, for two phase flow metering, its accuracy gets altered for liquid continuous phase (respectively gas continuous phase) in case of GVF that exceeds 20% (respectively low GVF that is lower than 80%). This paper presents a new Coriolis-based two phase flow meter (TPFM) that uses an upstream inline flow conditioner which separates liquid (i.e. water in this paper) from gas. Each of the gas dominant phase and liquid dominant phase are carried by two outlets, namely gas and liquid outlets respectively. A Coriolis flow meter and an actuated valve are placed in each outlet to measure and regulate the GVF that passes in each line. A new measurement algorithm based on a multistage artificial neural network (ANN) and which explores the physical model of the Coriolis flow meter is also suggested. This latest combines the pressure-volume-temperature (PVT) and bubble theory models to estimate the amount of gas (respectively liquid) dissolved in the liquid phase (respectively gas phase). Experimental results that were conducted on a multiphase flow loop reveals that for the whole GVF range (i.e. 0 to 100% GVF), the absolute value of the relative error on both the mass flow rate and density does not exceed 2.5%. This suggests that the proposed TPFM can be considered as a new non-hazardous alternative for accurate two phase flow measurement.

Effect of Viscosity on Pressure Drop of Oil-Water Two Phase Flow in 6” Horizontal and Inclined Stainless Steel Annulus Pipe

Two phase annular fluid flow (oil in water) commonly found in petroleum industry and is generally used for the lubricated transportation of highly viscous oil. Despite their importance, behavior of such flows has not been explored to an appreciable extent. Liquid viscosity may change considerably because of changes in temperature as in deep-water oil production. The variations in liquid viscosity have a remarkable influence on flow characteristics. In this experimental work, attention has been focused on effect of viscosity on pressure drop measurements of oil-water annular two-phase flow in a horizontal and inclined 6-inch diameter stainless steel pipe at different flow conditions. Two different mineral oils Exxsol D80 and Exxsol D130 along with water were used as working fluids in the present experimental study. Experiments were carried out for different inclination angles including: 0° - 90° and for different water cut (WC) ratios (0 to 100% in steps of 20 %). Inlet oil-water flow rates were varied from 2000 to 12000 barrels-per-day (BPD). For a given flow rate the frictional pressure drops (FPD) has been found to decrease from WC = 0 to WC 20%. Further increase in WC, FPD has been found to increase up to WC 40%. For WC more than 40%, the decrease in FPD is not appreciable. This could be due to phase inversion or change in flow pattern regime. For a given case with WC 40% (horizontal, ? = 0° case, flow rate = 10000 BPD), the FPD of Oil (D130) is more than FPD of Oil (D80) by 7%. This implies Oil (D80) is more suitable for transportation of oil-water two phase flows. For a given case (with WC 40%, 10000 BPD), for D80 oil, for increase in angle from zero degree to 90 degree, the increase in FPD is not appreciable. However, for the above scenario, for D130 oil, for increase in angle from zero degree to 90 degree, the percentage increase in FPD has been found to be 27%.

On the use of particle-wall interaction models to predict particle-laden flow in 90-deg bends

The objective of this work is to evaluate the capability of different combinations of a turbulence model and a Lagrangian particle tracking (LPT) model integrating a particle-wall interaction (PWI) model to predict particle-laden flow in 90-deg bends, as well as the impact of the PWI model on the prediction of the referred flow. The experimental data from Kliafas and Holt (1987) (LDV measurements of a turbulent air-solid two-phase flow in a 90° bend. Experiments in Fluids, 5: 73-85) concerning a vertical to horizontal square-sectioned duct with a hydraulic diameter of 0.1 m that are connected by a 90-deg bend with a curvature ratio of 3.52, served as the benchmark for the aimed analysis. Air with glass spheres of 50 μm diameter flows in the experimental duct system with a Reynolds number of 3.47×105. The airflow was modelled by four different turbulence models: a low Reynolds number k-e model, the SST k-ω model, the v2-f model, and the RSM SSG model. The particle-phase was modelled by a LPT formulation, and the particle-wall interaction was calculated using four different models: Brauer, Grant & Tabakoff, Matsumoto & Saito and Brach & Dunn PWI models. The 3D simulation results of mean streamwise velocities from the sixteen RANS-LPT/PWI combinations were compared qualitatively and quantitatively to experimental and numerical data available in the literature. The four turbulence models produced errors for the gas-phase in the order of 8%. Concerning the particle-phase, the errors produced by all RANS-LPT/PWI combinations were below 4% for bend angles up to 15° and up to 18% for bend angles higher than 30°. The best results for the particle-phase were obtained with the SST k-ω and v2-f model combined with the LPT/Brauer or LPT/Brach & Dunn PWI models, which produced errors inferior to 14%.

Experimental Investigation and CFD Modeling of Slush Cryogen Flow Measurement Using Circular Shape Capacitors.

The measurement of two-phase cryogenic fluid mixtures flow, also known as slush cryogen flow, with its most attractive form (liquid and solid) is of great interest for various applications, due to its thermodynamic advantages. This paper presents a newly developed device, under the form of a circular capacitor prototype, together with an experimental stand for slush formation. Slush nitrogen was used as testing fluid during the experimental work. Then, the experimental data for slush cryogen flow measurement using the proposed circular shape capacitor were compared with theoretical results obtained by simulation. A three-dimensional flow field model was built and solved for the innovative design slush flowmeter using a computational fluid dynamic (CFD) model. Nitrogen slush density of 874 kg/m3, representing approximately 30% solid fraction, was reported for both the modeling and experimental testing, although the numerical investigation is not limited to these values. By comparing experimental vs. simulation results, a deeper view on the designed configuration can be achieved, thus improving the progress in producing high-performance next generation devices for two-phase flow measurement in terms of physical dimensions, length and space between armatures. Even so, the mathematical model has limitations when mixtures with higher percentages of solid phase and particle sizes are encountered.

Liquid-phase turbulence measurements in air-water two-phase flows using particle image velocimetry

Liquid-phase turbulence plays a vital role in determining various gas-liquid two-phase flow parameters, such as void fraction distribution, bubble morphology, bubble-bubble interactions, and interfacial area concentration. In this study, a two-phase flow database including both the gas- and liquid-phases measurements was developed focusing on three bubbly flow conditions in an air-water two-phase flow loop with a vertical one-inch diameter circular pipe test section. A particle image velocimetry (PIV) system integrating an optical phase separation method, i.e., the planar laser-induced fluorescence (PLIF) technique using fluorescent particles and optical filtration, was applied to measure the liquid-phase turbulence information, including the time-averaged velocity, Reynolds stress, and turbulent kinetic energy for the liquid phase. The PIV measurements were taken at three ports along the test section at 14.5, 51.5, and 88.5 pipe inner diameters downstream of a bubble injector. In addition, a double-sensor conductivity probe was used to measure radial distributions of the local time-averaged void fraction and gas velocity. The measured liquid-phase turbulence was used to benchmark Sato's turbulence model considering the bubble-induced shear stress for the three tested bubbly flows. The benchmark results showed good agreement between the PIV measurements and model predictions. In the two bubbly flows tested that have low void fractions being less than 3%, the effect of the bubble-induced turbulence was found not significant. However, the bubble-induced shear stress becomes important with the increase of the void fraction.