Horizontal Straight Pipe Research Articles

Numerical investigation of aqueous graphene nanofluid ice slurry passing through a horizontal circular pipe: Heat transfer and fluid flow characteristics

Ice slurry is an attractive phase-change cold storage medium that offers excellent thermal performance, thus rendering it a good prospect for applications in renewable energy storage, power peak-cutting, and valley filling. In this study, a computational fluid dynamic (CFD) numerical framework is employed based on the particle dynamics approach of an Euler-Euler two-fluid model coupling interphase transfer mechanisms. Thermal transport of a water-based graphene nanofluid ice slurry moving in the turbulent regime in a horizontal circular straight pipe is simulated and described. During the flow, the ice crystals tend to cluster on the top of the horizontal pipe, according to the findings, while uniformity of the crystal size distribution improves with an increase of velocity and the ice packing factor (IPF). Under the conditions of inlet IPF of 10% and heat flux q = 8000 (W m−2), the heat transfer coefficient on the heated section wall is increased by around 9% and 15%, respectively, as compared to pure water ice slurry and water. However, since the nanofluids have a higher viscosity than water, the pressure drop of nanofluid ice slurry is about 5% higher than that of pure water ice slurry in the same working environment.

Numerical simulation of pneumatic conveying characteristics of micron particles in horizontal pipe

In this paper, a mathematical model for the pneumatic transport of micron silica particles in the dust removal pipeline is established, and the gas-solid two-phase flow in the pipeline is numerically simulated. This paper is mainly based on the FLUENT fluid simulation module in ANSYS WORKBENCH to simulate the motion behavior of particles in the pipeline, and obtained the penetration rate (particle deposition rate in pneumatic conveying) of silica particles in the horizontal straight pipe under different gas flow rates. In the numerical simulation, the influence of particle diameter, shape, lift and other factors on silica particles was considered. Under a large number of simulation conditions, the movement laws of micron silica particles in horizontal pipe pneumatic transport were obtained, and the influence of the above factors on the movement laws of the particles were determined.

Flow Morphologies in Straight and Bent Horizontal Pipes

Two-phase flows in pipes develop characteristic patterns or flow morphologies. Their transport between process units and plant components often involves short pipes, large pipe diameters, as well as bends and curvatures. The prediction of the predominantly undeveloped flow morphologies in such systems is challenging and subject to high uncertainties due to lacking experimental data and universal engineering models. In this work, comprehensive experimental studies were conducted in horizontal straight and bent pipes of 50 mm and 200 mm diameter. Wire-mesh sensors were applied at characteristic positions to obtain the gas–liquid distributions with high spatiotemporal resolution. Subsequently, a fuzzy classification method is applied to assign a flow pattern to characterize the flow conditions. As this assignment is fuzzy, we introduce an advanced concept of a color-coded flow map visualization for further analyses. As a result, we analyze the effect of pipe curvatures on the flow morphology and its downstream recovery.

Experimental and numerical investigations into flow features in an intake duct for the waterjet propulsion under mooring conditions

The waterjet propulsion is widely applied in the marine vessels over 30 knots, and the intake duct is considered as an essential component that strongly relates to the propulsion performance. This paper sheds light on the flow features inside an intake duct under mooring conditions by using the particle image velocimetry (PIV) technique with three-dimensional (3D) numerical simulations. The hydraulic loss gradually increase as the flow-rate increases. According to analyses via the Bernoulli equation, the hydraulic loss is composed of the frictional head loss (hf ~ V1.75) and the local head loss (hj ~ V2.0). A recirculation region is observed near the duct lower wall with a high-velocity flow near the upper wall, and subsequently a shear flow presents in the horizontal straight pipe with an obvious velocity gradient. Three-dimensional simulations demonstrate that the vortex pair is very strong in the recirculation region and then it gradually decreases as the fluid flows downstream. With the flow-rate increasing, the non-uniformity at the duct outlet firstly increases to a peak and then slightly decreases, while the perpendicularity at the duct outlet dramatically decreases to a minimum and then increases. This work not only reveals some physics of the waterjet propulsion under mooring conditions, but also promotes its efficient operation. The hydraulic loss gradually increase as the flow-rate increases. The hydraulic loss is composed of the frictional head loss (hf ~ V1.75) and the local head loss (hj ~ V2.0). A recirculation region is observed near the duct lower wall with a high-velocity flow near the upper wall, and a shear flow presents in the horizontal straight pipe with an obvious velocity gradient. Numerical simulations demonstrate that the vortex pair is very strong in the recirculation region and then it gradually decreases as the fluid flows downstream.

Effect of Particle Size on fluid flow and heat transfer in a Pipe with slurry flow

A three-dimensional numerical simulation is carried out in a straight horizontal pipe to predict the impact of particle size on fluid flow and heat transfer of ash water slurry. Steady turbulent equations are solved by using commercial code Fluent. Eulerian Method is incorporated considering ash as granular material. Fly-ash particle diameter is varied with 12, 20, 28 and 34 µm suspended in water for a flow velocity 4m/s and solid concentration of 40%. The temperature of pipe wall is kept at 400K and the granular temp i.e. slurry temp is taken as 300K. Present study finds asymmetric velocity distribution at higher particle size. Pumping power increases with particle size. Granular pressure and heat transfer increases with particle size. Granular pressure is maximum at bottom of the wall.

Numerical solution for magnetohydrodynamic flow in straight horizontal elliptical pipe

Numerical solution for magnetohydrodynamic flow in straight horizontal elliptical pipe

Velocity profile for magnetohydrodynamic flow in straight horizontal elliptical pipe

Velocity profile for magnetohydrodynamic flow in straight horizontal elliptical pipe

Temperature distribution for magnetohydrodynamic flow in straight horizontal elliptical pipe

Temperature distribution for magnetohydrodynamic flow in straight horizontal elliptical pipe

Numerical analysis of dilute gas-solid flows in a horizontal pipe and a 90° bend coupled with a newly developed drag model

The influence of particle concentration on the drag force of a particle deserves attention when using the Lagrangian Particle Tracking methods for the prediction of industrial type gas-solid flows. The Lagrangian approach is best suited to applications where the solids volume fraction is low, and the effect of particle concentration can be ignored. In the present work, a 3D time dependent numerical analysis is performed to study the effect of Lagrangian model improvements to replicate experimental studies of straight horizontal pipe flow and flow through a 90° horizontal-to-vertical bend. The present predictions are compared with published experimental data of Tsuji and Morikawa (1982), and Yilmaz (1997). Special attention is paid to influence of particle mass-flow rates and conveying velocity on the particle motion within the system. This study used a CFX-4 package, where the ability to modify the code was necessary to include particle model improvements. These improvements included implementing a newly drag force model developed as a part of this research work. Particle-wall collision and particle-particle collision models developed by Sommerfeld (1992), and Sommerfeld (2001) are also implemented in the CFD model. The standard k–ε dispersed turbulence model was utilized as the predictions for the gas phase only gave similar predicted axial velocity compared to the more computationally demanding Reynolds stress model. The results showed that the inclusion of the various improvements lead to reasonable predicted particle velocities in both the upper and lower regions of the straight horizontal pipe which denote the dilute and dense regions respectively. It was also found that the inclusion of the rough-wall particle wall collision model decreases the axial particle velocity in the lower region where the bulk of the particle wall collisions occur. While the inclusion of the particle collision models tends to disperse the particles away from the lower region resulting in a less dense lower section and a distinctly more homogenous particle distribution compared with the standard model predictions. Further, the increase in particle concentration leads to a reduction in axial velocity due to a loss of momentum through particle-wall and particle-particle collisions. Finally, the improved CFD model best predicted both the reduction and increase in the particle velocities in the different regions.

A study of the vibration of a horizontal U-bend subjected to an internal upwards flowing air–water mixture

U-bends are a common geometry in heat exchangers. In this paper, a U-bend in the vertical plane connected to horizontal straight pipes is considered. An initially stratified water/air flow moves upwards against gravity. The aim of this research is to investigate the internal flow profile and resulting force when the U-bend is subjected to a stratified air–water flow at the inlet. This is done numerically, i.e. by solving the unsteady Reynolds-averaged Navier–Stokes equations. For low mass flow rates, large gas bubbles are naturally formed at the entrance of the bend. The transient force on the tube allows to determine precisely the time instants of bubble initiation and thus to quantify the bubble frequency. Firstly, the tube is assumed to be rigid and the dependence of force oscillation on the inlet conditions is investigated. Secondly, the influence of the viscosity, wall wetting and the mass flow rate is analyzed. Finally, a fluid–structure interaction calculation is performed in order to quantify the vibration characteristics of the tube.

An evaluation of testing and modeling procedure for solids friction factor for fluidized dense-phase pneumatic conveying of fine powders

For the reliable design of a pneumatic conveying system, accurate estimation of solids friction factor through horizontal straight pipe is of paramount interest. Although the “straight pipe” method is fundamentally more appropriate, the “back calculation” approach provides several practical advantages for testing and modeling. However, earlier literature reports that “back calculation” approach suffers from 40 to 150% inaccuracy in prediction of total pipeline pressure drop in scale-up pipes, which had been discouraging for its use. In the present work, it has been argued that much of the criticism for the inaccuracy of back calculation method lies with the choice of its format of modeling solids friction factor. In this paper, “back calculation” method of modeling has been used by employing a “two layer” model format for solid friction factor for fly ash, ESP dust and cement. These models, when scaled up to predict the total pipeline pressure drop in larger and longer pipelines, have resulted in overall deviation from experimental data ranging from 3 to 35%, which is a significant improvement in prediction capability. The results prove that the selection of a better format of model for solids friction factor could significantly improve the reliability of “back calculation” method.

Water–air flow in straight pipes and across 90∘ sharp-angled mitre elbows

Water–air flow in horizontal and vertical straight pipes and through 90∘ sharp-angled mitre elbows is investigated by visualizing the flow patterns by means of a high-precision camera and by measuring the pressure drop. The flow is studied in pipes with three diameters for about six hundred conditions of water–air flows, characterized by superficial velocities in the ranges of jL* = 0.3–1 m/s for water and jG* = 0.15–34 m/s for air. The portion of the pipe upstream of the elbow is always positioned horizontally, while the portion of the pipe downstream of the sharp bend is oriented horizontally or vertically with the flow moving upward. Plug, slug, slug-annular, and annular flows are visualized in horizontal straight pipes, while slug, churn, and annular regimes are recorded in vertical straight pipes downstream of the sharp bend. These patterns are well predicted by the Mandhane map (Mandhane et al., 1974) for horizontally oriented straight pipes and by the Hewitt–Roberts map (Hewitt and Roberts, 1969) for vertically oriented straight pipes. The changes of the flow patterns as the fluids pass through the mitre elbows are discussed. A multiple membrane flow structure is observed in the vertical upward flow at much higher Reynolds numbers based on the water superficial velocity than in the vertical downward case previously reported in the literature. A dimensional analysis is employed to obtain the non-dimensional parameters that describe the flows through the straight pipes and across the elbows. It is proved that a rigorous way to present the flow regimes and the pressure-drop coefficients of the water–air flow for a given geometry is the space of the Reynolds numbers based on the superficial velocities of air and water for fixed Froude number because the flow is incompressible and isothermal. By expressing the maps in scaled form, the prediction of the flow patterns along the straight portions of the pipe improves. The flow patterns through the elbows are expressed in terms of rescaled Mandhane maps, which, for the first time, simultaneously represent the flow patterns both upstream and downstream of the elbows. New pattern-based empirical correlations are obtained for the scaled pressure drops for the water–air flows through the horizontal and vertical pipes and through the elbows. The correlations are based on the flow patterns and do not rely on widely used prediction models, thereby predicting the pressure drop more accurately than the models presently available in the literature.

Effects of parallel magnet bars and partially filled porous media on magneto-thermo-hydro-dynamic characteristics of pipe ferroconvection

In this experimental-numerical study, effects of transverse magnetic field of parallel magnet bars perpendicular to the fluid flow direction and partially filled porous media are investigated. Moreover, constant heat flux is applied on the outer surface of a circular straight horizontal pipe and concentric porous media is embedded inside it. Magnet bars are located right at the entrance of pipe and a thick layer of insulation is wrapped the pipe to prevent heat loss. In addition, a 3D numerical simulation is performed using CFD techniques to capture the influence of these two factors on the thermohydrodynamic behavior of ferrofluid flow. Hybrid scheme of finite volume method and SIMPLE algorithm are employed to discretize and solve governing equations as well as TDMA for solving the linear algebraic matrix equation. Mineral oil is used as a base fluid and ferrofluid with three different volume fractions 0.5, 1 and 2% are prepared for the experiment. Finally prepared experimental setup configuration in this investigation leads to this conclusion that in comparison with magnetic field, although porous media induce more unfavorable pressure loss, it will bring more heat transfer enhancement as well.

Comparison between rotation swirler and non-rotation swirler in a horizontal swirling flow pneumatic conveying

This paper proposes an application of a rotation swirler to swirling flow pneumatic conveying for reducing the conveying velocity and pressure drop decrease. A comparison with the swirling flow pneumatic conveying generated by a non-rotation swirler and axial flow pneumatic conveying was made, the total pressure drop decrease, minimum conveying velocity, energy consumption, and additional pressure drop decrease were evaluated experimentally. In addition, the cross-section profiles of the particle velocity and particle fluctuation velocity along a pipeline near the minimum pressure drop decrease were measured by the PIV (Particle Image Velocimetry) technique. The pipeline was a 5-m-long horizontal straight acrylic pipe with an inside diameter of 80 mm. Polyethylene particles of diameter of 2.3 mm were used as the conveying materials. The initial swirl number was varied from 0 to 0.66. The solid mass flow rates of 0.1, 0.28, and 0.47 kg/s were applied, and the superficial air velocity was varied from 9 to 16 m/s. It is revealed that the total pressure drop decrease and power consumption of the swirling flow using the rotation swirler exhibit the smallest values among all cases in the region of low air velocity, and are almost the same as the axial flow in the high air velocity region. The particle velocity and particle fluctuation velocity of the swirling flow originated by the rotation swirler are almost the same as the axial flow in the acceleration regime, but become larger than that of the axial flow near the bottom of the pipeline in the fully developed regime.

Non-intrusive characterization of sand particles dispersed in gas–water bubbly flow using straight and bent pipes with vibration sensing

The transport of a solid dispersed in a gas-water bubbly pipe flow is widely encountered in petroleum engineering. In this paper, the characterization of solid particles dispersed in a water-gas bubbly flow was developed based on vibration sensing from straight and bent pipes. Typical frequency-domain analysis, time-domain statistical analysis, and time-domain joint analysis were applied for sand-vibration signal identification and characterization. Verification experiments were performed, and good agreements were found between the sand concentration (0–0.24 wt%) with uniformly mixed sand size (300–600 μm) and sand-vibration energy in water flow and water-gas bubbly flow. Characteristic frequency bands of 4–5 kHz (horizontal straight pipe), 3.9–5 kHz (bent pipe), and 4.7–5 kHz (vertical straight pipe) were found. The sensor installed on a bent pipe obtained the highest vibration energy of water/water-gas bubbly flow among tested pipes; with the increase of sand injected, a sensor installed on the outer wall at 45° on the elbow obtained the most obvious vibration energy caused by sand–wall interaction. The validity of the detected sand signals was verified using an acoustic sensor. In summary, the vibration-sensing method is applicable to characterize solid particles in water-gas bubbly pipe flow.

Deposition of naphthalene particle in horizontal straight pipe of manufactured gas pipeline

After long time operation of the manufactured gas pipeline, the naphthalene in the gas will jam the pipeline and threaten the safety of the pipeline seriously. To study the naphthalene particle deposition law in the manufactured gas pipeline, a horizontal straight pipe of Kunming manufactured gas pipeline is taken as an example; based on Reynolds stress model and discrete phase model, ANSYS Fluent software is used to carry out the numerical simulation in different pipe diameters, particle size, inlet velocity, temperature, and pressure conditions. The main conclusion can be obtained as follows (1) in the horizontal straight pipe section, particle diameter and temperature are positively correlated with the deposition rate and the deposition velocity of naphthalene particle and the inlet velocity and pressure are negatively correlated with them; (2) the naphthalene particle deposition rate is mainly affected by the particle size and the inlet velocity; (3) the larger the pipeline diameters, the greater the particle mass flow rate under the same particle inlet concentration, the lower the carrying capacity of the fluid to particles, the greater the naphthalene particle deposition rate; (4) the naphthalene particle deposition can be suppressed by increasing the gas transmission velocity and pressure and reducing the temperature, thus ensuring the safe operation of manufactured gas pipeline.

Numerical simulation of two-phase flow regime in horizontal pipeline and its validation

PurposeThe purpose of this paper is to investigate oil-gas slug formation in horizontal straight pipe and its associated pressure gradient, slug liquid holdup and slug frequency.Design/methodology/approachThe abrupt change in gas/liquid velocities, which causes transition of flow patterns, was analyzed using incompressible volume of fluid method to capture the dynamic gas-liquid interface. The validity of present model and its methodology was validated using Baker’s flow regime chart for 3.15 inches diameter horizontal pipe and with existing experimental data to ensure its correctness.FindingsThe present paper proposes simplified correlations for liquid holdup and slug frequency by comparison with numerous existing models. The paper also identified correlations that can be used in operational oil and gas industry and several outlier models that may not be applicable.Research limitations/implicationsThe correlation may be limited to the range of material properties used in this paper.Practical implicationsNumerically derived liquid holdup and holdup frequency agreed reasonably with the experimentally derived correlations.Social implicationsThe models could be used to design pipeline and piping systems for oil and gas production.Originality/valueThe paper simulated all the seven flow regimes with superior results compared to existing methodology. New correlations derived numerically are compared to published experimental correlations to understand the difference between models.

Flow visualizations and pressure drop measurements of isothermal ice slurry pipe flows

The objective of the present project is to analyze the flow patterns resulting from isothermal ice slurries flowing in a straight horizontal pipe using combined flow visualizations and pressure drop measurements. Ice slurry is composed of an initial solution of 9.5% weight propylene glycol. The influences of the inlet mean axial velocity and ice volume fraction on the flow patterns and pressure drops are investigated experimentally for volume ice concentrations up to 18.4% in both the laminar and turbulent flow regimes. An original transition diagram has been proposed and new more complex stratified regimes are identified compared to the existing literature. Finally, pressure drop measurements have been performed for the straight horizontal pipe but also for more complex geometries such as elbows and T-junctions. At high ice fractions, ice particles agglomerate in the singularities leading to a sudden increase of the pressure drops.

On developing improved modelling for particle velocity and solids friction for fluidized dense-phase pneumatic transport systems

Pneumatic transport of fine powders in fluidized dense-phase pneumatic conveying of powders has become popular in several industries because it offers various advantages, such as reduced air flow and gas velocity, reduced pipeline sizing and wear rate, reduced size requirement of gas–solid separator unit etc. For the reliable design of a pneumatic conveying system precise estimation of the solids friction factor through horizontal straight pipes is essential, but it is a challenging task till date because of the highly concentrated, turbulent, and complex nature of the gas–solids mixture. In the present work, power station fly ash (median particle diameter: 22 μm; particle density: 2370 kg/m3; loose-poured bulk density: 660 kg/m3) and cement (median particle diameter: 19 μm; particle density: 2910 kg/m3; loose-poured bulk density: 1080 kg/m3) were conveyed through different pipeline configurations (i.e., 65-mm inner diameter × 254-m-long and 80/105-mm inner diameter × 407-m-long step-up pipeline). For the fluidized dense-phase flow in pneumatic conveying system, governing equations were developed and the same were solved using fourth-fifth-order Runge-Kutta-Fehlberg (RKF45) method. The results revealed that the particle velocity and actual gas velocity and the ratio of the two velocities increases along the direction of flow, while an opposite trend was found for the solids volumetric concentration. The particle velocity and actual gas velocity terms were then included in an existing pure dilute-phase model (for solid friction factor) to modify it, by incorporating sub-models for particle and actual gas velocities and impact and solids friction factor and make it suitable for dense-phase mode. The solids friction-factor model was then validated by comparing the experimental and predicted pneumatic conveying characteristics for different solids flow rates and by using it to predict the total pipeline pressure drops for larger and longer pipelines. The new model has shown reliable predictions in the dense-phase region.

A slug capturing method in unconventional scenarios: The 5ESCARGOTS code applied to non-Newtonian fluids, high viscous oils and complex geometries

Abstract Previous work showed that a one-dimensional, hyperbolic, transient five-equation two-fluid model can predict automatically the formation, growth, and subsequent development of slugs in horizontal and near-horizontal flow. This method was implemented in a finite volume numerical scheme – called 5ESCARGOTS code. Comparison with experimental data showed that it can be used to predict the flow pattern and statistical characteristics (slug velocity, length, and frequency). However, the capabilities of this approach have been tested only for water-air flows in a straight horizontal pipe. In this work, we validate the application of the code to some unconventional problems. Firstly, we test the possibility of slug capturing approach to describe and predict the relevant features of air/high viscosity oils or air/non-Newtonian fluids flows. Comparisons between some slug characteristics and empirical correlations, available in literature, are discussed. Then, we move from simple geometries toward more complex conditions that may be representative of actual application cases, also employing high viscous oils as liquid phase. Comparison against experimental data shows results in reasonable agreement.