Flow In Horizontal Pipe Research Articles

Estimation of pressure drop of single-phase flow in horizontal long pipes using artificial neural network

Large- pressure drop and drag along the pipe route is one of the problems with fluid transfer lines. For many years, various methods have been employed to reduce the drag in fluid transmission lines. One of the best ways for this purpose is reducing friction coefficients by utilizing drag lowering materials. Experimentally by adding minimal amounts of this material at the ppm scale to the lines and reducing the drag of the flow, fluid can be pumped without the need to change the size of the pipe. In this study, the effect of carboxymethylcellulose biopolymer on the water flow reduction in a 12.7- and 25.4-mm galvanized pipe was investigated. In order to have a comprehensive analysis of process conditions, experiments were carried out with three different levels of concentrations, flow rate and temperature. Also, as a new innovation in this investigation, the outputs of the experimental data were evaluated and analyzed using the Taguchi method and neural network system, and optimized through a genetic algorithm. In this study, the highest rate of drag reduction will be achieved at 39 ° C and at a concentration of 991.6 ppm and flow rate of 1441.1L/h was 59.83% at 12.7-mm diameter.

Holdup Measurements of Aqueous Foam Flows and Flow Regime Characterization through Image Processing

Summary One of the most critical issues in the oil and gas industry is the dewatering of the pipelines used for natural gas transportation, and foam injection seems to be a prominent solution. This work has two goals: The main one concerns the development of an optical tool to measure the liquid holdup in foamy flows and perform the flow regime characterization, whereas the secondary goal is to quantify the effectiveness of surfactant injection in reducing the liquid loading. In this paper, we present the results of an experimental campaign aimed at the characterization of gas-liquid-foam flows in a horizontal pipe. Initially, liquid loading measurements for gas and liquid superficial velocities, ranging from 0.41 to 2.30 m/s and from 0.03 to 0.06 m/s, respectively, were performed by means of a specifically developed optical method. For each liquid superficial velocity, the minimum liquid holdup was found to lie in the proximity of the boundary between plug and stratified flow regime, with a superficial gas velocity between 0.44 and 0.90 m/s. Hence, the plug flow region corresponds to the best operating condition to perform the pipeline dewatering procedure. Moreover, the drift-flux model usually adopted for ordinary two-phase gas-liquid flows seems to fit well with the measured values of void fraction.

Numerical investigation of gas-liquid two-phase flow in horizontal pipe with orifice plate

Gas-liquid two-phase flow in horizontal or vertical pipeline significantly impacts on the transportation process. In fact, in the pipeline for regulating the flow flux or pressure, orifice plate and other current limiting device are frequently encountered. The flow behaviors of two-phase flow thus become more complicated in the pipeline with orifice plate. In order to explore the characteristics of gas-liquid two-phase flow in the pipeline accompanied by orifice plate, the computational fluid dynamics (CFD) simulation with volume of fluid (VOF) method and SST k−ω eddy viscosity model were imposed to probe the transient two-phase flow in a horizontal pipeline. The reliability of the numerical method was verified by a case of annular multiphase flow in a pipeline. In our research, two transient simulations related to different liquid volume ratios were carried out to explore the developments of the flow regimes. In addition, fluctuations of the area-average fluid pressures acting on the orifice plate surfaces were also monitored. The frequency characteristics of pressure pulsations were extracted via non-uniform fast Fourier transform (NUFFT). The main results show that the jet could be produced after the liquid passes through the orifice plate, and the liquid volume ratio has significant effects on the gas-liquid two-phase flow behaviors, a higher ratio leads to a faster stable and fuller jet. The stability of jet could be reflected via the dimensionless velocity ratio. The gas-liquid two-phase flow in the pipe with orifice plate induces typical broadband excitation.

Multiphase Flow Regime Characterization and Liquid Flow Measurement Using Low-Field Magnetic Resonance Imaging.

Multiphase flow metering with operationally robust, low-cost real-time systems that provide accuracy across a broad range of produced volumes and fluid properties, is a requirement across a range of process industries, particularly those concerning petroleum. Especially the wide variety of multiphase flow profiles that can be encountered in the field provides challenges in terms of metering accuracy. Recently, low-field magnetic resonance (MR) measurement technology has been introduced as a feasible solution for the petroleum industry. In this work, we study two phase air-water horizontal flows using MR technology. We show that low-field MR technology applied to multiphase flow has the capability to measure the instantaneous liquid holdup and liquid flow velocity using a constant gradient low flip angle CPMG (LFA-CPMG) pulse sequence. LFA-CPMG allows representative sampling of the correlations between liquid holdup and liquid flow velocity, which allows multiphase flow profiles to be characterized. Flow measurements based on this method allow liquid flow rate determination with an accuracy that is independent of the multiphase flow profile observed in horizontal pipe flow for a wide dynamic range in terms of the average gas and liquid flow rates.

An investigation of transition processes from transient gas–liquid plug to slug flow in horizontal pipe: Experiment and Cost-based recurrence analysis

Transient gas–liquid two-phase flows are often encountered in nuclear industries. Investigating the dynamics of the transient gas–liquid flows is of significance for optimizing the reaction processes and predicting the thermal–hydraulic phenomena relevant to the performance of nuclear reactors. In this study, a multi-nozzle gas inlet was designed to mimic the transient gas–liquid flows in a horizontal pipe. A conductance wire-mesh sensor (WMS) was used to visualize the phase distribution at the pipe cross-section. Based on the WMS data, a cost-based recurrence analysis (CBRP) was developed to reveal the dynamics of transient gas–liquid flows. Different transition processes from plug flow to slug flow were observed in the experiment and explored by the determinism (DET) of the CBRP. Note that special flow structures, i.e., wave bridge and pseudo slug, were encountered during the flow pattern transition, and their generation mechanisms were uncovered. The processes of the flow pattern transition were also characterized by the slug frequency and the probability density function of the water holdup, which presented a good agreement with the CBRP results.

Analysis of interfacial behavior in two-phase flow using image processing

Two-phase flow has a wide range of application from petroleum to space industry. Gas-liquid two-phase flow in horizontal pipe commonly occurs in petro-chemical, nuclear and geothermal industry, where simultaneously gas and liquid are transported through pipelines. During the transportation of gas-liquid flow simultaneously, due to the interaction of two phases, slug forms from the stratified-wavy flow. Slug flow consists of strong aeration at the slug front which is responsible for pipe failure and hazards in industries. Thus, it is required to understand the phenomena of slug formation in industrial pipeline to avoid the catastrophic pipe failure. In the present research, image processing technique is used to accurately analyze the interfacial behavior of two-phase flow. The interfacial behavior plays crucial role, as it is the plane where the two phases interact and interaction of the phases leads to the transition of different two-phase pattern. Experimentally captured images are processed using image processing algorithm, to study the variation of liquid film thickness. With the help of liquid film thickness transition of the interface is analyzed for different superficial Reynolds number of liquid and gas. Further, a PDF analysis is reported to understand the mechanism of the growth of the wavy interface.

Effects of density, viscosity and surface tension on flow regimes and pressure drop of two-phase flow in horizontal pipes

Two-phase gas/liquid flow in pipes is a common occurrence in the petroleum, chemical, nuclear and geothermal industry. In the petroleum industry, it is encountered in the production, transportation, and processing of hydrocarbons from the oil and gas fields. In designing these systems, accurate prediction of pressure drop is imperative, which is determined from the flow pattern and flow regime map. Unfortunately, most of the flow regime maps were developed for the air-water system and widely used for the oil/gas system. Despite the practical importance, the general applicability of these maps is not addressed. In order to improve the generality of flow regime maps, it is necessary to evaluate the effect of density, viscosity, and surface tension, which differ by great magnitude on flow regime maps. Thus, this study evaluates the effect of density, viscosity, and surface tension on the flow regime map. To evaluate the effect of fluid properties, experiments were conducted using a horizontal flow loop of 9.15 m (30 ft) pipe length and 0.0254 m (1-inch) pipe diameter with a two-phase air/liquid system. The surface tension was varied using the surfactant solution, viscosity was varied with the aid of glycerin, and density was varied with the aid of calcium bromide. The superficial velocity of the liquid ranges from 0 to 3.048 m/s (0–10 ft/s) and superficial gas velocity ranges from 0 to 18.288 m/s (0–60 ft/s) respectively. The experimental data were used to generate a flow pattern map and to predict the effect of these properties on the variation in the boundaries of different flow patterns and pressure drop. The results show that the flow patterns and transition boundaries were affected by fluid properties. The boundary between the annular and slug-annular flow at high velocity, the slug flow and pseudo-slug flow at medium velocity, and inertial wave and ripple wave flow at low velocities are affected by the variation in surface tension, viscosity, and density. The decrease in surface tension shifted the boundary between annular and slug flow toward the left-bottom corner of the flow regime map, while, similar effects were observed due to an increase in viscosity, which is opposite to the effect of surface tension. The increase in density shifts the boundary toward the top-right corner of the flow regime map. The effect of density on the flow pattern transition is significant compared to the viscosity, while the viscosity effect is higher than the surfactant. The effect of fluid properties on pressure drop is noticeable at high velocities, however, the pressure drop is not evident to reveal the flow pattern and boundary transition quantitatively.

Analysis of pressure fluctuations for oil-gas two-phase flow in a horizontal pipe using the bubble number density equation

Visualization experiments and numerical simulations of two-phase flow are conducted to study the pressure fluctuation characteristics of oil-gas flow in horizontal pipes. The two-fluid model based on the Eulerian–Eulerian method is adopted, and the bubble number density equation (BNDE) is introduced to the simulation to predict the bubble size and distribution within the pipe. The bubble size and pressure variations in the pipe obtained from the simulations agree well with the recorded values from the experiments. The fast Fourier transform (FFT) algorithm is used to analyze the characteristics of pressure fluctuations, and the results show that the sudden pressure increase in the pipe sections is related to gas injection. The bubble number density increases with liquid flow rate (Ql ), which causes the oil-gas flow to be more turbulent while increasing the amplitude of high-frequency fluctuations. The maximum amplitude for the dominant frequency is observed near the pump inlet for low liquid flow rates. At high liquid flow rates, more liquid vortices are found near the gas orifice, and there is a maximum amplitude for the dominant frequency in this section. Due to the high swirling strength at larger inlet gas volume fraction (IGVF), there is an obvious increase in the amplitude of low-frequency fluctuations, while the amplitude of high-frequency fluctuations is nearly the same under all IGVF.

Predictive correlations for heat transfer characteristics of oil-water horizontal pipe flow-an experimental study

This paper presents convective heat transfer characteristics of liquid-liquid horizontal pipe flow. Experiments are carried out in a stainless-steel pipe of diameter 1.59 cm with L/D ratio of 377. Three different oils with varying properties (viscosity: 630 mPa-s, 202 mPa-s and 1.95 mPa-s and density: 919 kg/m3, 901 kg/m3 and 790 kg/m3 respectively) are employed as oil phase and the other fluid phase being water. The experiments are conducted for four oil-water flow patterns-stratified flow, stratified flow with droplets at the interface, dispersed oil-in-water and dispersed water-in-oil with fluid fractions ranging 0 to 1 at different fluid velocities. A constant temperature heat supply, using jacketed hot water flowing over the test pipe, is maintained. The analysis of heat transfer experiments indicates that the heat transfer process in liquid-liquid flow depends on the same dimensionless terms, the Reynolds number and the Prandtl number, that signifies single-phase flow heat transfer. Accordingly, it is found that the established and existing single-phase heat transfer correlations, modified according to flow regime, flow pattern and fluid flow and thermal properties, are also applicable for liquid-liquid flow. The heat transfer in liquid-liquid flow found to be influenced by the fluid fraction. Effectively, for stratified flow, the heat transfer in the liquid-liquid flow is the sum of heat transfer of the individual fluid phases. However, for dispersed flow, the presence of additional fluid phase is incorporated by employing the effective Reynolds number and effective Prandtl number. Using this methodology, more than 85% of stratified flow and 92% of dispersed flow heat transfer characteristics are predicted within ±20% of experimental data.

Investigations on the slug two-phase flow in horizontal pipes: Past, presents, and future directives

Precise prediction of the gas–liquid slug flow is crucial for proper design and operation at various industrial processes. This paper provides a comprehensive review of published experimental and numerical works in horizontal pipes, including a critical analysis of state-of-the-art parameters used to characterize the slug flow regime. The discussed slug characteristics are slug length, slug frequency, and slug velocity. Throughout the paper, an endeavor does devote to discerning the areas where modern development work is needed. Accordingly, some observed gaps in the literature, comprising hydrodynamic behavior at the transition zone and the interaction between slug flow and structural pipe. The lack of comprehensive laboratory experimental information for high liquid viscosity and the viscosity impact on the slug characteristic is also observed. On the contrary, robust and less empirically independent CFD models are required for accurately predicting the slug characteristics with a minimal computational cost.

Flow status identification based on multiple slow feature analysis of gas–liquid two-phase flow in horizontal pipes

A gas–liquid two-phase flow is a highly complex and random process with complicated and variable flow statuses. The status identification of two-phase flows focuses on the situation of flow processes over specific time periods, as reflected by flow regimes, phase holdup, flow velocity, and other parameters. Aiming to discover how to obtain flow status information and identify the flow statuses of gas–liquid two-phase flows in horizontal pipes, a meticulous identification method based on multiple slow feature analysis combined with Bayesian inference is proposed, with concurrent monitoring of steady states and process dynamics. In this method, representational models for different typical flow regimes are established to describe both the steady states and temporal distributions. On this basis, by monitoring statistics and developing a Bayesian inference-based index, the current flow status can be identified online. Besides status identification, process dynamics are monitored to detect the dynamic characteristics of the current process with meaningful physical interpretation and deep process understanding. The application of this method to typical flow regimes and the status of transitions from bubble flow to slug flow demonstrates the feasibility and efficacy of the proposed method.

A Computational Fluid Dynamics Study of Liquid–Solid Nano-fluid Flow in Horizontal Pipe

A regular phenomenon in the petroleum industry is the challenges being faced with a multiphase flow system. Recovering only the oil often results in static pressure losses which often leads to a multiphase mixture being pumped to a separation or processing terminal. The rate of micellar aggregates breakup of surfactants is usually faster when compared to their rate of formation. Polymers of high molecular weights are capable of reducing drag even at minute concentrations degrades under shear stress and at high temperatures, this mechanical degradation could be improved upon with the combination of these duos, thereby making use of the physicochemical interactions between polymers molecules and surfactants micellar aggregates, In this study, ionic polymers such as polyacrylic acid (PAA), Tween 20 (non-ionic surfactant) and Carbon Nanotubes (CNT) particle were tested individually and the complexes examined in the pipeline at varied concentrations. A drag reduction of about 50% was obtained with 1000 ppm of polymer, 300 ppm of the surfactant and 500 ppm of the nanofluid CNT. An increase in concentration with increased Torque was also observed regardless of the sample tested. It was realized that these combinations could be a better drag reduction method as results were obtained and analyzed by comparing the individual performances of these substances, with the complexes where the complexes have a better performance, and this could be as a result of the critical role played by the complex mixtures. The effect of the various additives was simulated using computational fluid dynamics.

Experimental and Numerical Investigation of Solidification of Gallium in an Initially Emptied Horizontal Pipe Flow

Abstract In a reactor core meltdown under postulated severe accidents, the molten material (corium) could be ejected or relocated through existing vessel penetrations (cooling pipe connections), thus potentially contaminating other locations in the power plant. There exists, however, a potential for plugging of melt flow due to its complete solidification, providing the availability of an adequate heat sink. Therefore, a numerical model was created to simulate the flow of molten metal through an initially empty horizontal pipe. The numerical model was verified using a previously developed analytical model and validated against experimental tests with gallium (low melting temperature) as a substitute for corium. The numerical model was able to predict the penetration length (length of distance traveled by the molten metal) after a complete blockage occurred with an average percent error range of 9%. Since the numerical model has been verified and validated, the model was updated to predict the penetration length in the cooling pipe in case of a severe accident. The model was used to predict the penetration length for different Reynolds numbers and pipe diameters, which resulted in the range of penetration length from about 0.33 m to 0.93 m.

Flow and heat transfer for a two-phase slug flow in horizontal pipes: A mechanistic model

In view of the practical importance of gas–liquid two-phase flow in many applications, such as chemical engineering, petroleum engineering, nuclear engineering, etc., a reliable model of flow and heat transfer for two-phase flow is of practical importance in the two-phase flow analysis. Among various two-phase flow regimes, slug flow is most complicated due to the intrinsic randomness and intermittency. This paper aims at developing a novel mechanistic model of flow and heat transfer for two-phase slug flow in horizontal pipes. First, a hydrodynamic model of two-phase slug flow is developed using the concept of slug unit cell. Then, a heat transfer model is deduced based on the hydrodynamic model. The overall heat transfer coefficient is integrated by the local heat transfer coefficients of liquid slug, liquid film, and elongated bubble. The newly developed mechanistic model is well validated by the experimental results. Finally, the dependence of the heat transfer performance on the overall flow parameters, such as superficial liquid velocity and superficial gas velocity, and the local flow parameters, such as slug frequency, pressure drop, void fraction, and ratio of slug length to unit cell length, is comprehensively investigated. The heat transfer enhancement of two-phase slug flow compared with single-phase flow is mainly attributed to the turbulence increase in liquid by the injection of air and the decrease in thermal boundary layer by the frequent alternation between the liquid slug and the elongated bubble.

Parametric study of the {beta }-{sigma } two-fluid model for simulating fully suspended slurry flow: effect of flow conditions

As proven in a recently published paper [Messa GV, Matoušek V (2020) Analysis and discussion of two fluid modelling of pipe flow of fully suspended slurry. Powder Technol 30:747-768.], the beta-sigma two-fluid model is capable of accurately reproducing the main features of turbulent, fully-suspended slurry flows in horizontal pipes provided that suitable values of the two parameters beta and sigma are chosen. At present, the case-specific nature of beta and sigma and their lack of a clear physical meaning are the main obstacles that must be overcome to give the beta-sigma two-fluid model value not only as interpretative tool, but also as a predictive one. An important preliminary step to achieve this goal is to disclose the mathematical essence of the beta-sigma two-fluid model, namely, to interpret the fluid-dynamic solution on the grounds of the structure of the differential and discretized equations. Such a methodological approach is applied here to the benchmark case of turbulent slurry flow between two infinite, horizontal, parallel plates, focusing, in particular, on the influence of the bulk-mean velocity of the slurry and the volumetric concentration of the solids in the flow. The study provides not only deeper insight into the beta-sigma model, but also indicates important implications for alternative two-fluid models.

Dimensionless Parameters to Identify Transition from Stratified to Non-stratified Flow Pattern in Liquid–Liquid Horizontal Pipe Flow

This paper aims to analyze dimensionless parameters, Weber number and Reynolds number, to describe inception of droplets at the interface of liquid–liquid pipe flow. Experiments are conducted in a 15.9 mm diameter and 6 m long stainless-steel pipe using high viscous oils and water. An empirical Weber number correlation, adapted from gas–liquid flow and modified for liquid–liquid flow, is proposed to identify the formation of droplets at the interface. The analysis of the proposed Weber number correlation indicates that the droplets originate when Weber number ≈ 300 and higher. The experimental data from the literature of low and high viscous oil–water flows is also considered for the analysis. The analysis suggests that the Kelvin–Helmholtz instability singularly does not produce droplets at the interface but only when the fluids inertial forces exceed the interfacial tension forces by 300 times. The data from the literature provide sufficient evidence on the existence of wall originated fluctuations in at least one of the fluid phases before the advent of interfacial waves or interfacial droplets. Accordingly, the investigation of Reynolds number indicates that the droplets are found to form when either oil or water phase Reynolds number Reo or Rew attains ≈ 12,000 with the respective fluid mass fraction ≥ 0.2. However, for fluid mass fraction < 0.2, the droplets evolve at the interface when fluid Reynolds number Reo or Rew attains ≈ 3000.

Bubble characteristics and turbulent dissipation rate in horizontal bubbly pipe flow

The energy dissipation rate is a crucial parameter for system control and turbulence modeling but is difficult to quantify in gas–liquid two-phase flows. Little relevant information is available, especially in horizontal pipe flows. Based on the consideration that the bubble characteristics in a stable bubbly flow are a reflection of flow turbulence, the bubble shape and bubble size spectrum are investigated in a 10-m-long horizontal rectangular pipe by means of high-speed imaging and graphic processing techniques. The bubble size spectra indicate a critical length scale, deemed to be the Hinze scale, and the spectral shape is related to turbulent fragmentation and, thus, enables calculation of the turbulence dissipation rate. After careful validation of the approach for estimating the turbulence dissipation rate, an empirical prediction equation is proposed based on the present tested flow conditions, reflecting the effects of both the pipe flow velocity and the gas flow rate. Such information is useful for the modeling of turbulent two-phase flows.

Measurement of Three-Dimensional Characteristics of Slug Flow

Gas-liquid slug flow in horizontal pipes occurs frequently in industrial applications and is harmful to the piping systems owing to its intermittent structures. Therefore, it is essential to accurately describe the flow structure and investigate the flow mechanism. A non-intrusive fluorescence imaging method is employed to quantitatively reconstruct the slug bubble in a 15mm ID horizontal pipe in this article. Optical distortion correction method is firstly developed to improve the measurement accuracy of the instantaneous gas holdup, and then the time-average axial bubble velocity is simultaneously measured according to the feature matching of cross-sectional images. Additionally, the influence of phase superficial velocity on the interface stability is investigated through the phase holdup and the circumferential curvature distribution analysis. The typical three-dimensional structures of slug bubble are finally reconstructed through the velocity-based bicubic interpolation and median fusion algorithm. Previous correlations and reference instrumentation are used to evaluate the proposed method. Comparison results show that the method can effectively measure the flow parameters and reconstruct slug bubbles.

The staged development of a horizontal pipe flow at supercritical pressure

The axial development of heat transfer to supercritical fluids in horizontal pipe has been studied both experimentally and numerically. It has been demonstrated that the flow and heat transfer exhibit a distinct three-stage development, including two entrance effect stages and an asymptotic development stage. Stage I is characterized by a rapid heat transfer coefficient reduction and is largely caused by the thermal boundary layer development. When the inlet temperature is close to the pseudo-critical value however, flow laminarisation also plays a role. Stage II is a special entrance effect, which has not been observed in flow and heat transfer at subcritical pressure condition. This is caused by the strong buoyancy effect, leading to stratification and secondary flow. Most interestingly the heat transfer of supercritical fluids in a horizontal flow can reach a pseudo-developed state stage III, where the flow and heat transfer is free from the influence of the entrance condition. This contrasts the common belief that the heat transfer of supercritical fluids can never reach an axially asymptotic condition because of the significant property variations. The existence of such a condition can be of great value for fluid-to-fluid similarity analyses.

Flow Regimes Identification-based Multidomain Features for Gas–Liquid Two-Phase Flow in Horizontal Pipe

Accurate flow regimes identification is of great significance for the deep understanding of the flow structure and ensuring the safe and economic operation of actual production in the multiphase flow process. For the flow regimes identification of the gas-liquid two-phase flow in the horizontal pipe, a multidomain features processing scheme is proposed. The water holdup data are acquired by conductance rings sensor, and processed by the improved empirical wavelet transform (EWT) to obtain the Fourier spectrum in the frequency domain and decomposition components in the multiscale domain. The obtained multidomain feature information is quantified to get the high-dimensional feature vectors of different flow regimes. To make the features more representative and realize the visualization of the structural relationship between the flow regime samples, the isometric feature mapping (Isomap) method in manifold learning is used to synthesize the feature structure relationships and map them to low-dimensional space. The obtained low-dimensional feature vectors of training samples are input into the support vector machine (SVM) to acquire the flow regimes identification model. Compared with other flow regimes identification schemes that feature reduction uses different manifold learning methods, or feature extraction is not in multidomain, or data preprocessing uses traditional wavelet transform, the proposed scheme can better retain the global structural relationship of the flow regimes, has the characteristics of strong stability, and the identification rate of the gas-liquid two-phase flow regimes in the horizontal pipe is over 95%.