Horizontal Straight Pipe Research Articles

Particle Dynamics Study on Influencing Factors of Ice Slurry Flow Characteristics in District Cooling Systems

In district cooling systems, substituting the conventional cooling medium with ice slurry represents an ideal approach to achieve economical operation. During pipeline transportation, ice slurry exhibits heterogeneous flow characteristics distinct from those of pure fluids. Consequently, investigating the flow field characteristics of non-homogeneous ice slurry, quantitatively analyzing the rheological variations and flow resistance laws due to the uneven distribution of ice particles, and standardizing the comprehension and depiction of flow patterns within ice slurry pipes hold significant theoretical importance and practical value. This study analyzes the heterogeneous isothermal flow characteristics of ice slurry in a straight pipe by employing particle dynamics and the Euler–Euler dual-fluid model. Taking into account the impact of ice particles’ non-uniform distribution on the rheological properties of ice slurry, a particle concentration diffusion equation is incorporated to develop an isothermal flow resistance model for ice slurry. The flow behavior of ice slurry with initial average ice particle fractions (IPFs) ranging from 0% to 20% in DN20 horizontal straight and elbow pipes is examined. The findings reveal that the degree of heterogeneous flow in ice slurry is inversely proportional to the initial velocity and directly proportional to the initial concentration of ice particles. When the flow velocity is close to 0.5 m/s, the flow resistance of ice particles exhibits a linear positive correlation with changes in flow velocity, whereas the flow resistance of the fluid-carrying phase displays a linear negative correlation. As the flow rate increases to 1 m/s, the contribution of each phase to the total flow resistance becomes independent of the initial velocity parameter. Additionally, the drag fraction of the ice particle phase is positively associated with the initial concentration of ice particles. Furthermore, the phenomenon of “secondary flow” arises when ice slurry flows through an elbow, enhancing the mixing of ice particles with the carrier fluid. The extent of this mixing intensifies with a decrease in the turning radius and an increase in the initial velocity.

Two-Phase Crude Oil-Water Flow Through Different Pipes: An Experimental Investigation Coupled with Computational Fluid Dynamics Approach.

The present study deals with two-phase non-Newtonian pseudoplastic crude oil and water flow inside horizontal pipes simulated by ANSYS. The study helps predict velocity and velocity profiles, as well as pressure drop during two-phase crude-oil-water flow, without complex calculations. Computational fluid dynamics (CFD) analysis will be very important in reducing the experimental cost and the effort of data acquisition. Three independent horizontal stainless steel pipes (SS-304) with inner diameters of 1 in., 1.5 in., and 2 in. were used to circulate crude oil with 5, 10, and 15% v/v water for simulation purposes. The entire length of the pipes, along with their surfaces, were insulated to reduce heat loss. A grid size of 221,365 was selected as the optimal grid. Two-phase flow phenomena, pressure drop calculations, shear stress on the walls, along with the rate of shear strain, and phase analysis were studied. Moreover, velocity changes from the wall to the center, causing a velocity gradient and shear strain rate, but at the center, no velocity variation (velocity gradient) was observed between the layers of the fluid. The precision of the simulation was investigated using three error parameters, such as mean square error, Nash-Sutcliffe efficiency, and RMSE-standard deviation of observation ratio. From the simulation, it was found that CFD analysis holds good agreement with experimental results. The uncertainty analysis demonstrated that our CFD model is helpful in predicting the rheological parameters very accurately. The study aids in identifying and predicting fluid flow phenomena inside horizontal straight pipes in a very effective way.

Improving flushing processes through targeted control of the temperature boundary conditions

AbstractIn this contribution the authors investigate how flushing of chocolate using a follow‐up chocolate in a straight horizontal pipe is affected by temperature. The authors investigate a non‐uniform distribution of temperature across the considered domain. This is done using two cases, where the first exhibits a wall temperature deviating from the normal process temperature and the second exhibits a differently tempered follow‐up chocolate. The investigations are performed using unsteady three‐dimensional numerical simulations with an OpenFOAM multiphase solver, which is extended to include an additional equation for energy conservation. The physical properties of the chocolate are analyzed with respect to their dependence on temperature and implemented in a new model in OpenFOAM. The results of both cases are assessed according to industrially relevant questions. Among others, they include the amount of follow‐up chocolate needed to achieve a set goal of cleanliness. The time needed to achieve this is also considered. A dimensionless time is used to compare the different cases. Recommendations are provided on how different temperature of pipe wall and follow‐up chocolate may lead to improved flushing processes and which savings may be achieved with this strategy.

Impact of Pipe Diameter on the Discharge Process of Halon1301 in a Fire Extinguishing System with Horizontal Straight Pipe

In aviation fire extinguishing systems, the extinguishing agent is stored in a bottle, which is pressurized by nitrogen. When fire occurs, the agent is discharged via pipe and nozzle to the target compartment. The geometry of the pipe has a significant impact on the discharge process, and merits study. In this study of the discharge process of halon1301 using pipes of different diameters, the pressure distribution was significantly influenced by varying pipe diameter. Contributions to pressure drops through the valve/pipe/nozzle were approximately 2%, 8%, and 90%, respectively, when the pipe diameter was larger than the nozzle diameter. The contribution through the pipe increased, and the contribution through the nozzle decreased, as the pipe diameter became smaller. When the pipe diameter was decreased to the nozzle diameter, pressure drops through the valve/pipe/nozzle were 10%, 45%, and 45%, respectively; there was an increased pressure drop through the pipe. Distinctions in pressure distribution led to temperature differences; when there were more pressure drops through the nozzle, the temperature in the pipe was lower.

Solid friction coefficient in a horizontal straight pipe of pneumatic conveying

Pressure drop prediction model has been well concerned in pneumatic conveying system design. The Barth’s additional pressure drop prediction model is one of the most widely accepted and applied models, in which the solid friction coefficient in horizontal straight pipe is particularly important. In this work, a regression model of solid friction coefficient was addressed on the basis of two dimensionless numbers (the inlet Froude number and the solid-gas loading ratio), which were conducted based on fly ash pneumatic conveying experiment data in a 16 m length pipeline. Then, the prediction accuracy of the regressed model was verified by the pressure drop of other pneumatic conveying pipeline system, 123 m and 139 m pipelines, respectively. The results show that solid friction coefficient gradually decreases with inlet Froude number, conversely, it increases with solid-gas loading ratio. And the regressed solid friction coefficient maintained relatively high accuracy in the prediction of pressure drop, for both fly ash pneumatic conveying pipelines of 16 m length and 123 m length. However, a different prediction accuracy appeared for the different loading ratio of 139 m length pipeline complete pneumatic conveying system. The pressure drop prediction accuracy sharply declines when solid-gas loading ratio is larger than 85.

Additional pressure loss coefficient of pneumatic conveying of moist-mixed materials for shotcrete based on CFD-DEM method

A systematic study of pressure loss through four common pipeline forms for pneumatic conveying of moist-mixed materials for shotcrete (horizontal straight pipes, vertical pipes, horizontal elbow, and vertical upward elbow) was conducted using CFD-DEM coupling. On-site experiments were conducted to verify the accuracy of the simulation. The research results showed that solid-gas ratio and moist-mixed materials for shotcrete have an influence on pipeline pressure loss. Furthermore, coefficients for additional pressure loss in horizontal and vertical pipes, and an equivalent horizontal length for both types of bends were established. Additionally, the spatial position and velocity of particles were examined under four conditions. The findings of this study have implications for the design and pressure loss estimation of pneumatic conveying pipelines for moist-mixed materials for shotcrete.

Numerical study on critical flow velocity of ice slurry in the pipe of ice source heat pump system

The traditional evaporator of water source heat pump system is easy to freeze when the water source temperature is too low in winter. A novel ice source heat pump system is proposed, which can use low temperature surface water to supply heat to buildings. One of the key problems for safe transportation is velocity range of ice slurry in ice outlet pipeline. In order to study the critical flow velocity of ice slurry in the pipe, an Euler model of horizontal straight pipe and 90° elbow pipe were established by Fluent software. The influence of five factors on the critical flow velocity of two kinds of pipes, including initial ice packing fraction, ice particle size, pipe diameter, length of straight pipe and radius curvature of elbow was studied. It found that the initial ice content should be controlled from 10% to 15%. The inlet flow rate was 20% higher than the critical flow rate under the most unfavorable condition. Ice particle size was less than 0.2 mm. The total length of ice discharge pipeline was less than 50 m. Curvature radius of the bend should be met the minimum requirements of the specification of the pipe used.

Prediction of unsteady slug flow in a long curved inclined riser with a slug tracking model

An improved one-dimensional mechanistic model is presented for the prediction of unsteady gas-liquid slug flows in inclined curved pipes, using the slug tracking approach. The equations for mass and momentum conservation are applied to the slug body, liquid film, and elongated bubble regions constituting a slug unit cell. The proposed model can be applied to horizontal or inclined upward flows. Statements of mass conservation result in axial changes of the liquid and gas velocities in the liquid film and elongated bubble. The slug initiation at the inlet is modelled as a random process with slug length variations. Closure relationships for the bubble nose velocity, modified by the wake effect, and the slug frequency for slug initiation are employed. The discretized governing equations are solved fully implicitly, introducing numerical treatments associated with the outlet boundary conditions and the merging of slug units. Of practical interest is an upward gas-liquid slug flow in a catenary riser with a high aspect ratio (length over diameter) being an order of a thousand representing an offshore subsea pipe for the oil and gas production. By considering the pipe initially fully filled with the traveling liquid, the dynamic scenario of the pipe transporting successive slug units is simulated, capturing the continuing evolution of slug flow patterns along the pipe exhibiting the disappearances of liquid slugs due to the bubble coalescences. Spatio-temporal variations of the liquid holdup, the pressure and its gradient, the film and slug lengths, the slug frequency, the velocities of the slug front, bubble nose, liquid in the slug body and film, and of the gas in the elongated bubble are evaluated. The backward flow occurrence in the film zone near the outlet is also predicted due to the pipe inclination. Parametric investigations are performed by specifying the superficial liquid and gas velocities, and comparing the cases of catenary pipes (with variable inclinations) versus inclined and horizontal straight pipes (with fixed inclinations). Results highlight the important effect of gas-to-oil superficial velocity ratio (GOR) in combination with the pipe inclination and curvature effects. Fluctuations of slug flow properties appear to be considerably amplified and more intermittent when increasing the GOR. This observation is important towards regulating the practical flow rates for subsea oil and gas productions as well as designing flexible pipes subject to slug flow-induced vibrations.

Estimation of energy consumption and transportation characteristics for slurry flow through a horizontal straight pipe using computational fluid dynamics

The energy expense of slurry transportation through the pipeline plays a vital role in the economics of various modern industries, such as mining, crude oil, petroleum, and mineral processing. Therefore, it is essential to develop a suitable condition by which we can efficiently transport slurry without affecting the environment and capital costs. To solve these problems, a steady state three-dimensional multiphase Eulerian RNG k–ε turbulence model based on the kinetic theory of granular flow is developed to investigate transportation parameters like pressure distribution, concentration distribution, head loss, settling velocity, and specific energy consumption. Four different particles named bottom ash, glass beads, iron ore, and silica sand with five different sizes, 125, 200, 275, 350, and 440 μm are transported through 3.8 m long straight pipe having 54 mm pipe diameter. The trends of various transportation properties with varying flow velocity (Vm = 1–5 m/s) and efflux concentration (Cw = 40%–60%) are presented. The numerically obtained results for different slurries and water are in good agreement with the past experimental data available in the literature. The computational finding shows that the transportation of bottom ash requires minimum energy, whereas silica sand needs the maximum. In addition, the degree of deviation into transportation properties increases with the particle size, efflux concentration, and flow velocity.

An Experimental Study on the Transportation Characteristics of Perfluoro(2-methyl-3-pentanone) in a Straight Pipe

Gaseous fire suppressants are usually stored in a vessel via pressurization, and then discharged out through pipelines. The flow behaviors of the agents in pipes greatly affect its dispersion in space, as well as the fire extinguishing results. Here, an experimental study was carried out on the transportation characteristics of perfluoro(2-methyl-3-pentanone) (C6F12O) in a horizontal straight pipe with the temperature and pressure recorded synchronously. At a filling pressure of 1800 kPa and a filling density of 517 kg·m−3, the agent release was completed in 2.0 s with the pipeline pressure peak of 1145 kPa and the pipeline temperature nadir of −10.6 °C. In comparison to that of bromotrifluoromethane (CF3Br) under the same conditions, the temperature and pressure curves of C6F12O exhibited similar varying trajectories but a much smaller amplitude, which could be ascribed to their different thermophysical properties. When keeping the other conditions unchanged, raising the filling pressure C6F12O reduces the discharge duration and the pipeline temperatures. Increasing the filling density extends the discharge duration, but shows little influence on the pipeline temperatures. The results were expected to provide useful information for the model validation and engineering design of a C6F12O fire-suppressing system with a predictable performance.

Investigation on the evolution of ice particles and ice slurry flow characteristics during subcooling release

For the subcooling method ice slurry generator, the characteristics of ice slurry during subcooling release have a significant impact on the efficiency and stability of the system. An object of this paper is to investigate the evolution and distribution of ice particles in supercooled water and the flow characteristics of ice slurry during subcooling release in horizontal straight pipe, based on computational fluid dynamics (CFD). Moreover, the population balance model (PBM) is adopted to research the growth, agglomeration and breakage of ice particles. The effects of velocity, subcooling degree and ice volume fraction at the inlet are investigated. In terms of pressure and velocity, the average error between numerical simulations and experimental results is approximately 10%. The results indicated that the evolution of ice particle diameters is significantly affected by the degree of subcooling, which contribute to the growth of ice particles. For each 1 K increase in supercooling degree, the particle diameter will increase by 50 µm. The temperature trend of water from the supercooled state to the phase equilibrium state is consistent with the evolution of ice particles. Besides, the ice volume fraction along the vertical axis at the outlet can be divided into low-concentration, high-concentration, and stable regions, which is significantly affected by the degree of supercooling. Close to the wall, the ice volume fraction drops sharply due to collisions between the wall and the particles. The velocity of the ice slurry is symmetrically distributed along the vertical axis.

Investigation into starting speed of stone in slurry shield circulation system

Slurry circulating system is the core system for transporting excavated stone from the excavation interface, and the flow characteristics of stone in circulating pipeline is the key to determine whether stone can be transported smoothly. Based on Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) coupling method, the movement model of stone in horizontal straight pipe of circulation system is established, and the influence of stone shape coefficient and equal volume particle size on stone starting speed is studied. The simulation results indicate that under the condition of equal volume particle size of stone is same, starting speed of stone with different shapes is ellipsoid > flat > nearly spherical; When the equal volume particle size of stone is 38.5, 42.5, 53.3, 56.2 and 58 mm, the starting speed of stone is 0.48, 1.06, 1.26, 2.36 and 4.7 m/ s respectively, which increases exponentially with the increase of equal volume particle size. The conclusions can be helpful for setting the working parameters of circulation system.

Application of the Temperature Oscillation Method to Laminar Flow in Straight Horizontal and Curved Minichannels

This work deals with the application of the temperature oscillation method to measure local values of the heat transfer coefficient in laminar flow in a straight horizontal pipe and in a pipe with a bend. This method, applied here for the first time in such experimental conditions, uses a time-varying heat flux as a boundary condition, which is a condition of the third kind. Since an analytical solution for such conditions could not be identified in the existing literature, a numerical study of this problem is applied here. Experimental data for a straight horizontal pipe confirm the numerical results within a reasonable level of error. Experimental measurements on a straight horizontal tube are consistent with predicted results in the literature for both total and local heat transfer coefficient values. The measurements on bent tubes show a very significant influence on the local values compared to the straight tube and in the overall values this change appears as an increase in the heat transfer coefficient.

Characteristics of Flow Development and Boiling Transitions in the Liquid Oxygen Chill-Down Process in a Straight Horizontal Exit-Contracted Pipe

Liquid oxygen chill-down in a straight horizontal pipe was studied experimentally. The effect of the entrance corner was excluded, and much denser wall temperature sensors along the pipe have been set compared to the present studies. In this way, the chill-down process, as well as the development of the flow pattern, has been drawn for every test. As a result, the mechanism of LO2 chill-down would be obtained for various pressure sections. For cases with stable pressure below 1.25 MPa, liquid rewetting in the pipe is controlled by the propagation of quenching fronts. For cases with a higher pressure, liquid rewetting in the second half of the pipe is controlled by the sudden liquid fill-in. Based on the transition points obtained, heat transfer coefficients on the Leidenfrost point and critical heat flux have been correlated for various pressure sections using new approaches. Conclusions show that the correlation equations are dependent on the chill-down mechanisms.

Study on flame propagation characteristics of coal dust explosion in horizontal straight pipe

AbstractCoal dust explosion is one of the common accidents in mines. The flame generated in the explosion process spreads rapidly, and the high-temperature flame will cause personal injury and equipment damage in the working environment. In order to study the flame propagation characteristics of coal dust explosion, four kinds of coal dust explosion flame propagation experiments were carried out by using the intelligent coal dust explosion identification device, and the flame propagation process was simulated by computational fluid dynamics (CFD) simulation. The results show that the flame length of lignite dust explosion is obviously longer than that of long flame coal, non-caking coal and gas coal. From the ignition of lignite coal dust, the flame length increases continuously, reaches the maximum of 52 cm at a certain time and then gradually decreases to 0. While the flame length increases, the flame propagation rate also experiences the propagation process of accelerating and decelerating. By comparing the explosion flame length obtained by CFD numerical simulation with the experimental results, it is found that the simulation error is within the acceptable range. Further statistical analysis is made on the simulation results of overpressure generated by explosion, and it is found that the change law is consistent with the theoretical formula, so as to further verify the feasibility of numerical simulation for explosion research. The research results lay a theoretical foundation for predicting the disaster scope of coal dust explosion accidents, and have practical significance for taking explosion suppression and flameproof measures in mines.

CFD investigation of pressure drop reduction in hydrotransport of multisized zinc tailings slurry through horizontal pipes

Zinc is an important metal useful in hydrogen production. Mining of zinc also involves zinc tailings disposal using pipeline transportation which is an energy- and water-intensive process. In this study, the multisized slurry of zinc tailings is modeled using CFD to investigate the flow field characteristics in a straight horizontal pipe fitted with swirl-inducing sections. The primary objective was to study the pressure drop by adding swirl-inducing pipe of different numbers of lobes to the conventional pipe. Nine configurations of multi-lobed swirl-inducing pipes were studied for transport characteristics of solids at three flow rates and three overall solids concentrations. Eulerian-Eulerian modeling with the RNG k-ε turbulence model is employed for simulations. The numerical model is validated for pressure drop against available experimental results, and excellent agreement is achieved. The study shows that 10-lobed swirl-inducing section fitted to the conventional pipe reduces the pressure drop by nearly 35%, offering the potential for further exploration.

Numerical Study on Flow-Melt Characteristics of Ice Slurry in Horizontal Straight Pipe with a Local Large Heat Flux Segment

Ice slurry is a high energy density coolant with excellent flow, phase change, and thermophysical properties. In order to investigate the recovery of ice slurry flowing through a local large heat flux segment, a 3D Eulerian-Eulerian model based on the granular kinetic theory considering the flow and melting phase change of ice slurry is developed. Sensitivity analysis of interphase forces is carried out. A comparison of the pressure drop, solid phase velocity, and heat transfer coefficient with empirical data is carried out, respectively. The calculated results are in good agreement with the experimental results, indicating that the numerical model could accurately describe the flow and melting characteristics. Thermophysical field distributions, the axial variation of ice volume fraction (IVF), recovery curve, the average heat transfer coefficient, as well as the re-uniformization length are obtained. After passing through local large heat flux segment, due to shear stress action, the IVF and the particle uniformity of the cross section have recovery characteristics. The gradient of the recovery curve decreases with increasing inlet IVF as well as with increasing Reynolds number. After the local large heat flux increases to a certain value, its effect on the recovery curve of the ice slurry is small. The re-uniformization length increases as the local large heat flux increases. The average heat transfer coefficient of local large heat flux segment increases due to damage of the boundary layer. These results can provide a theoretical basis for the design of ice slurry systems in practical application.

Slurry flow characteristics through a horizontal pipeline at different Prandtl number

The settling behavior of solid particles in the slurry pipeline leads to bed formation and sedimentation at the bottom of the pipeline. This in turn causes the blockage of the pipeline resulting in more energy consumption and a pressure drop in the slurry pipeline. The present work investigates the effect of the different Prandtl numbers on the slurry flow characteristics through a horizontal pipe. Since the flow is a liquid-solid mixture, therefore, a steady-state three-dimensional Eulerian two-phase model in combination with the RNG k-ε turbulence model is implemented for the current simulation in the commercial software ANSYS FLUENT. Numerical predictions and procedures for the mixture of solid concentrations are generally in good agreement with the past experimental data available in the literature. Slurry flow features are examined at four different Prandtl numbers i.e., 2.88, 3.42, 4.62 and 5.83 for different-sized glass beads (125, 200, 275, 350 and 440 μm) slurry for the concentration ranging from 40 to 60% (by weight) at a mean flow-velocity of 5 m/s. The findings show that the pressure drop rises with the escalation in particle sizes and Prandtl number for chosen efflux concentration range. Furthermore, low Prandtl fluid demonstrates relatively higher granular pressure, temperature and wall shear stress, which further increases with raise in solid concentration and particle size. In addition, higher Prandtl number fluid demonstrates maximum specific energy consumption (SEC) for every particle and efflux concentration range. • 3D CFD modeling of slurry flow via horizontal straight pipe is investigated. • Effect of different Prandtl number on slurry flow characteristics is studied. • Effect of particle size and concentration on slurry pressure drop is presented. • At lower Prandtl number, maximum granular pressure and temperature is established. • Transportation of slurry with higher Prandtl fluid is more energy efficient.

Wheeled Capsule Threshold of Motion at Different Locations in a Horizontal Bend Pipeline Based on Hydraulic Capsule Pipeline Transportation

As the process before the transporting of the capsule in a hydraulic capsule pipeline system, the capsule’s threshold of motion process is often tested in the horizontal straight pipe. However, the result of the physical test in this work shows that the wheeled capsule more easily start-moves in a horizontal bent pipe. Thus, the numerical simulation and the theory analysis were used to study the wheeled capsule’s threshold of motion process in the bent pipe. The simulation results demonstrate that the velocity magnitude of the water flow was asymmetric between the inner part and the outer part of the section closing on the wheeled capsule. This was unlike the water flow of the section in the straight pipe. From this result, a new mechanical model was proposed that divides the wheeled capsule into two parts. The two parts of the mechanical model correspond to the two parts of the section. Then, the deduction has shown that the bolsters of the inner part of the wheeled capsule in the bent pipe endured lower maximum static friction than those in the straight pipe. The whole wheeled capsule was more unstable in the bent pipe than in the straight pipe because of the additional drag force induced by the centrifugal effect of the bent pipe’s water flow.

Repercussions of Increment in Reynolds Number and Half Distance of Major Axis on Magnetohydrodynamic Flow in Elliptical Pipe

Analysis has been carried out on velocity configuration for Magnetohydrodynamic (MHD) flow in a straight horizontal pipe of elliptical cross section when Reynolds number and half-length of major axis are adjusted. An electrically conducting, viscous and incompressible fluid flow in the z-direction of a long pipe with elliptical cross-section in x-y plane has been scrutinized. An applied magnetic field is conveyed to the pipe in the y-direction. The fluid is driven by Lorentz force and gravitational force. The governing equations are partial differential equations (pdes) formulated in terms of cylindrical coordinates (r, , z) by amalgamating r-component of Navier-Stokes equation, Ohm’s law, equation of continuity and cross-section of pipe. Navier-Stokes equation is non-dimensionalised, composed in terms of stream function, , converted to an ordinary differential equation (ode) using similarity transformation and evaluated numerically using Finite Element Method (FEM). Results are obtained for velocities for values of Reynolds number, Re? 10.0 and half major axis distance, a 0.0034. Tables and graphs are created and sketched respectively using these findings. The eventualities confess that: When Reynolds number and a half distance of major axis are escalated, velocity of the fluid rises at the centre of the pipe but dwindle to zero towards the periphery of the pipe in both cases. Subsequently, it is anticipated that a pipe of elliptical cross-section would be more beneficial in research on natural phenomena and technological applications than a circular one with the same depth. Fluid velocity and capacity will be higher in the elliptical pipe than in circular pipe resulting in higher MHD effects.