Increasing Pipe Diameter Research Articles

Assessment of Optimum Slurry Pipe Design for Minimum Erosion

Particulate erosion is a major concern in slurry handling unit of a thermal power plant. The pipe bends are the most erosion affected element of a pipeline unit thus, a cost-effective method to reduce pipeline erosion is highly desirable. This work aims to suggest the optimal pipe bend design to minimize the particulate erosion by analyzing the erosion wear in geometrically different pipe bends for bottom ash slurry flow by using Computational Fluid Dynamics code FLUENT. A Three-dimensional simulation study of erosion wear is carried out by implementing Euler-Lagrange modeling along with the standard k-ε turbulence model to solve the complex multi-phase flow. Pipe bends of different bending angle (30°, 45°, 60°, and 90°), diameter (50 to 250 mm) and bending ratio (r/D = 1 to 2.5) are evaluated at different flow condition. The wear location gets shifted to the upper section of the bend and its magnitude is significantly reduced with the increase in pipe diameter and bending angle. The dynamics of multiphase slurry through different bends is analyzed to understand the complex wear phenomenon. The simulation result shows good agreement with the published findings. Finally, a least erosion affected pipe bend profile is suggested for slurry transport unit.

АНАЛІЗ СУЧАСНОГО СТАНУ РИНКУ ПУБЛІЧНИХ ЗАКУПІВЕЛЬ У СФЕРІ БУДІВНИЦТВА НА ПРИКЛАДІ ЗОВНІШНІХ МЕРЕЖ ТЕПЛОПОСТАЧАННЯ

У статті проаналізовано сучасний стан ринку публічних закупівель зовнішніх мережтеплопостачання,виявлено що з кожним роком закупівель на будівництво трубопроводів, лінійзв’язку та електропостачання стає дедалі більше. Це пояснюється зношеністю мереж трубопро-водів та потребує їх негайної заміни. Проаналізовано вартість прокладання зовнішніх мереж те-плопостачання та виявлено, що ціна збільшується зі збільшенням довжини мережі та зменшу-ється зі збільшенням діаметру труби. Статистичний аналіз виявив, що учасникам закупівель вигі-дніше брати участь у закупівлях на великий об’єм робіт – це більш економічно вигідно для підпри-ємства у разі перемоги. Проведений аналіз дав змогу виявити, що питання оптимізації механізмівздійснення публічних закупівель відповідно до цілей такої політики уявляється актуальним напря-мом для подальших досліджень.

Numerical simulation of dense-phase pneumatic transport of powder in horizontal pipes

This paper presents a numerical study of dense-phase horizontal pneumatic conveying of powders by means of Computational Fluid Dynamics (CFD). The validity of the numerical model is first verified by comparing predicted pressure gradients with both published laboratory and industrially measured data. Then, effects of gas superficial velocity, solids loading ratio and pipe diameter on the flow regime transition and dune formation in horizontal pipes are investigated. Results show that dune, stratified and suspension flow regimes can be successfully reproduced. The transition of the suspension flow to the dune flow is determined mainly by the proportion of gas and solid phases. With increasing pipe diameter, the dune flow changes to the stratified flow. Also, flow characteristics are analyzed with respect to different flow regimes. It reveals that the formation of the dune flow is due to the intensive interaction between suspension and accumulation zones through a contact zone.

The suitability of the dimensionless terms used in correlating slug liquid holdup with flow parameters in viscous two-phase flows

Empirical correlations have been proposed for estimating slug liquid holdup, HLS, using Froude number, NFr, viscosity number, Nμ, and inverse viscosity number, Nf. Some of these correlations show physically inconsistent behavior when tested against each flow parameter due to relying on regression analysis without considering the effect of each flow parameter included in these numbers.This work analyzes the performance of these numbers and provides guidelines for the selection of the correct combination of non-dimensional numbers. Our analyses indicate that the Nμ is not suitable for revealing the effect of liquid viscosity on HLS; instead it reveals the effect of mixture velocity due to its dominant effect. Also, the product of the NFr and Nμ, both with positive exponents, is unsuitable for correlating HLS with liquid viscosity. This combination results in a decrease in HLS with increasing liquid viscosity, contradicting the experimental observations. Furthermore, the product of the NFr and Nf, both with positive exponents, results in a decrease in HLS with increasing pipe diameter, opposing experimental findings reported in the literature. Finally it is concluded that the most suitable combination for correlating HLS is the product of the NFr with a positive exponent, and the Nμ with a negative exponent.

Sectional lumped parameter model using bond graph and simulation for hot asphalt pipelines

ABSTRACTIn order to achieve the matching control of hot asphalt and foaming water and improve the quality of foamed asphalt, fully considering the characteristics of the asphalt pipeline is necessary. Our dynamic model of the hot asphalt pipeline system was constructed by a sectional lumped parameter method, and the dynamic characteristics of the hot asphalt pipeline system were analyzed using Simulink software. The results showed that with decreasing pipe diameter and increasing pipe length and asphalt viscosity, the fluid pressure, flow vibration frequency, and amplitude reduced at the pipeline nozzle, whereas the loss increased. Under these conditions, the dynamic response of the pressure and flow reached the steady state faster. In contrast, with increasing pipe diameter and decreasing pipe length and asphalt viscosity, the fluid pressure, flow vibration frequency, and amplitude increased at the pipeline nozzle, whereas the loss decreased. The dynamic response speed of the pressure and flow attained steady state at a slower pace.

Numerical Analysis on the Effect of Artificial Ventilated Pipe Diameter on Hydrodynamic Performance of a Surface-Piercing Propeller

Under the condition of large water immersion, surface-piercing propellers are inclined to be heavy loaded. In order to improve the hydrodynamic performance of the surface-piercing propeller, the installation of a vent pipe in front of a propeller disc is more widely used in the propulsion device of high speed planning crafts. Based on computational fluid dynamics (CFD) method, this paper studied the influence of diverse vent pipe diameters on hydrodynamic performance of the surface-piercing propeller under full water immersion conditions. The numerical results show that, with the increase of vent pipe diameters, the thrust and torque of the surface-piercing propeller decrease after ventilation, and the efficiency of the propeller increases rapidly; the low pressure area near the back root of the blade becomes smaller and smaller gradually; and the peak of periodic vibration of thrust and torque can be effectively reduced. The numerical results demonstrate that the installation of artificial vent pipe effectively improves the hydrodynamic performance of surface piercing propeller in the field of high speed crafts, and the increase of artificial vent pipe diameter plays an active role in the propulsion efficiency of the surface-piercing propeller.

Assessment of the Load on Automatic Pipe-Rolling Systems and Prospects for New Systems

The actual load on the primary line and the rollers in the automatic mill of the TPA-220 pipe-rolling system at AO PNTZ is assessed, with a view to expansion of the pipe range (increase in pipe diameter to 245 mm).

Development of fragility functions for natural gas transmission pipelines at anchor block interface

In this paper, fragility functions are developed for natural gas transmission pipelines at anchor block interface under the effect of seismic wave propagation. The fragility functions are developed for three typical pipelines in two types of soils. Seismic response of the pipeline at anchor block interface is evaluated by conducting non-linear dynamic response analysis of the pipeline system. The pipeline system consisting of the pipe, the anchor block, and the surrounding soil is subjected to ground shakings associated with a set of 36 earthquake records to develop the fragility function. The results of analyses indicate that the critical pipeline section is at pipe-anchor block interface where the pipe is susceptible to local buckling failure. The fragility functions are developed using strain limit state associated with local buckling of the pipe. The results of this study indicate that the vulnerability of pipelines to the local buckling failure at pipe-anchor block interface increases with increasing pipe diameter. Also because of the relatively large anchor blocks in soft soils, pipelines are more vulnerable to the local buckling failure in soft soils than in hard soils.

Push-out test: Why bother?

Bonding between cement and steel is currently believed to be of key importance in well integrity since it prevents the development of microannulus. Push-out test is often used to quantify the bonding strength between cement and steel in laboratory. Our experiments reveal a strong size-dependency of the push-out strength measured in these tests: the strength decreases with pipe diameter. This means that the push-out strength is not an intrinsic material parameter ("bonding strength") and therefore cannot be applied to field conditions before a proper correction is introduced. Such correction should take into account the large difference in diameter between the casing and the pipes typically used in laboratory tests. Finite-element simulations show that the experimentally-observed size-dependency could be, at least partially, explained by cement shrinkage that creates initial normal stress at the interface. The observed push-out strength is then not an intrinsic property of the interface between two materials (which would be an adhesive shear strength) but rather a result of interfacial friction. As the pipe diameter increases, the shrinkage-induced normal stress at the interface decreases, the frictional resistance decreases, and thus the measured push-out strength decreases, too, as observed in the lab tests. Simulations show, however, that shrinkage-induced decrease in push-out strength cannot fully explain the size-dependency since the decrease is much larger in the experiments than in the simulations. Another mechanism that could be at play is the common size effect: interfaces become weaker as their size increases because it is more likely that a larger interface contains an initial flaw of a given size. The decrease of push-out strength with pipe diameter has at least two practical implications: (i) the concept of bonding strength is misleading (unless it is specified explicitly that this parameter refers to frictional resistance at the interface rather than to an inherent adhesive strength) and (ii) the results of push-out tests can be used in well design only if a proper correction for the pipe diameter is introduced.

Possibilities to use the meta model and classical approaches to evaluate the impact of hydraulic conditions in prediction of the critical submergence depth ratio

Abstract One of the hydraulic phenomena that mainly occurs during the water withdrawal process of channels is the formation of vortices that can cause many problems for the hydro-mechanical facilities of intakes. In the current study, classical models and meta model approaches (i.e. Support Vector Machine and Gene Expression Programming) were applied to evaluate the impact of pipe diameter and hydraulic condition changes in prediction of the critical submergence depth ratio in horizontal intakes. In this regard, two types of critical submergence experiments, based on bottom clearance, were considered (i.e. c = 0 and c = d/2, in which c and d are the bottom clearance and diameter of the intake, respectively). Different models were developed and tested using experimental data series. The results indicated that in modeling the critical submergence depth ratio, meta model approaches led to better predictions compared to the classical approaches. It was observed that the developed models for the state of c = d/2 yielded better results. According to the outcome of sensitivity analysis, the ratio of velocities in the intake pipe and channel (Vi/Vc) had a key role in the modeling. It was also found that intake pipe diameter affected the critical submergence depth ratio in intake pipes. Increasing pipe diameter caused a decrease in model accuracy.

Experimental study of the factors affecting the flow pattern transition in horizontal oil–water flow

Flow patterns are important for pressure gradient calculation and corrosion protection. In this study, the characteristics of oil–water flow were investigated in a horizontal acrylic pipe with an inner diameter of 14.6 mm. The effects of oil viscosity, pipe diameter, pipe material and oil type were studied. Mineral oils with viscosity values of 20, 237 and 456 mPa·s were used as the working fluids. The flow patterns were identified by a high-speed camera and pressure gradients. The size of the dispersed oil droplets increased with increasing oil viscosity. The mixture velocity required to initiate ST&MI flow from SS flow increased with increasing oil viscosity. The transition boundaries extended to high velocities with increasing pipe diameter. In large-diameter pipes, the low-viscosity oil–water flow patterns were stratified flow, dispersed flow and their transition flow, and the high-viscosity oil–water flow patterns were annular flow in addition to these other flows. In small-diameter pipes, stratified flow, dispersed flow, annular flow and intermittent flow patterns were found for both low- and high-viscosity oil–water flow.

Analysis of Entropy Generation of a Magneto-Hydrodynamic Flow Through the Operation of an Unlooped Pulsating Heat Pipe

The aim of the study is the analysis of a uniform magnetic field effect on fluid flow, heat transfer, and entropy generation through the operation of a pulsating heat pipe (PHP). An open loop PHP with three neighboring vapor plugs and two liquid slugs has been considered. The governing equations such as momentum, energy, and mass equations are solved using an explicit method except for the energy equation of liquid slugs. For each case study, Bejan number has been derived to find the heat transfer share in entropy generation. According to the results, the performance of the oscillating heat pipe decreases by applying uniform magnetic field. Moreover, the obtained results illustrate the effects of the applied magnetic field position on the heat transfer and the entropy generation. The latent and sensible heat transfer into the PHP enhance as a result of increase in the pipe diameter, so that the liquid slugs oscillate with high amplitudes. In addition, the entropy generation value increases with an augmentation in the value of the pipe diameter. The evaluated Bejan numbers indicate that the viscous effects in entropy generation decrease as the pipe diameter increases. Furthermore, the results depict that the heat transfer performance of PHP improves by increasing temperature difference between evaporator and condenser sections. With an increase in the value of the evaporator temperature, the Bejan number will increase, as a result, this phenomenon reveals the inconsiderable role of viscous impacts in high evaporator temperatures. In order to validate the calculations, the calculated results have been compared with the previous studies which show good agreement.

Effects of pipe size on horizontal two-phase flow: Flow regimes, pressure drop, two-phase flow parameters, and drift-flux analysis

This paper performs experimental studies to investigate the effects of pipe size on horizontal air–water two-phase flow in a wide range of flow configurations. Some of the major characteristic two-phase flow phenomena of interest include flow regime transitions, two-phase frictional pressure drop, local interfacial structures, and drift-flux analysis. Based on the experimental results obtained in two pipe sizes, the flow regime maps and the correlations for two-phase frictional pressure drop employed in conventional nuclear reactor system analysis codes (TRACE and RELAP) are evaluated. It is found that the flow regime maps in the codes incorrectly predict plug and slug flows as bubbly flow. Effects of pipe size on flow regime transitions are observed, while these effects are not reflected on the maps employed in the codes. The frictional pressure drop analysis suggests that the closure relations used in both TRACE and RELAP can be improved for horizontal two-phase flow. The local time-averaged two-phase flow parameters acquired by a four-sensor conductivity probe including void fraction, interfacial area concentration, bubble velocity, and bubble Sauter-mean diameter provide quantitative descriptions for the interfacial structures in different pipe sizes. It is found that increasing the pipe size tends to cause bubbles to be more concentrated near the top wall in bubbly flow. As a result, the bubble layer occupies a smaller portion of the flow area as pipe diameter increases. Based on the experimental database, drift-flux analysis using both the 〈〈vg〉〉 vs. 〈 j〉 and 〈α〉 vs. 〈β〉 methods is performed. The effect of pipe size on drift-flux analysis is found to be negligible. The global slip is found to be less than one, indicating that the gas phase moves slower than the liquid phase in horizontal bubbly flow. This analysis also provides a predictive method to estimate the void-weighted bubble velocity and void fraction, which can be predicted with an average percent difference of ±3.3% and ±3.1%, respectively.

Charge and discharge behavior of elemental sulfur in isochoric high temperature thermal energy storage systems

Thermal energy storage with elemental sulfur is a low-cost alternative to molten salts for many medium to high-temperature energy applications (200–600 °C). In this effort, by examining elemental sulfur stored isochorically inside isolated pipes, we find that sulfur provides attractive charge/discharge performance since it operates in the liquid-vapor regime at the temperatures relevant to many important applications, such as combined heat and power (CHP) plants and concentrating solar power (CSP) plants with advanced power cycle systems. The isolated pipe configuration is relevant to shell-and-tube thermal battery applications where the heat transfer fluid flows over the storage pipes through the shell. We analyze the transient charge and discharge behavior of sulfur inside the pipes using detailed computational modeling of the complex conjugate heat transfer and fluid flow phenomena. The computational model is validated against experiments of a single tube with well-defined temperature boundary conditions and internal temperature measurements. The model results evaluate the influence of pipe diameter on charge and discharge times, heat transfer rate, and Nusselt number due to buoyancy driven convection currents. Depending on the Rayleigh number (pipe diameter), the average Nusselt number obtained for discharge is 3–14 times higher than proposed solid-liquid phase change technologies based on molten salt, which are limited in their performance due to conduction based solidification and low thermal conductivity. The results show competing trade-offs between increase in heat transfer coefficient, thermal energy stored in sulfur, and increase in charge and discharge time with increase in pipe diameter. A preferred pipe diameter can be determined for target applications based on their requirements and these competing trade-offs. A validated fundamental correlation for Nusselt number as a function of Rayleigh number for charge and discharge is developed that can be used to design the sulfur-based thermal storage system for transient operation.

On slug frequency in concurrent high viscosity liquid and gas flow

Slug frequency is an important input parameter in most mechanistic and semi-mechanistic models used for estimating slug flow characteristics such as pressure gradient, slug length and slug holdup. It is also essential in the design and sizing of transport and/or production pipelines, process flow control, design and operation of process equipment, etc. This study experimentally investigates slug frequency in two horizontal pipelines with internal diameters (ID) of 0.0254 and 0.0764 m. Test liquids used in the study were mineral oil (with viscosity ranging from 1.0 to 4.0 Poise) and water while compressed air is the gas phase. Effects of liquid viscosity, gas superficial velocity, liquid superficial velocity, pipe internal diameter, pipe length and pressure gradient are discussed. Results indicate that slug frequency increased with increase in oil viscosity; decreased with increase in pipe diameter; and reduces along the length of the pipe. For gas Reynolds number, ReSG≤2500, slug frequency increased with increase in gas superficial velocity, when ReSG>2500, slug frequency decreased with increase in gas superficial velocity. A new slug frequency correlation that accounts for liquid viscosity and gas superficial velocity, hitherto not included in other correlations was proposed. A comparative analysis of the proposed models and existing slug frequency correlation on a high viscosity databank showed that the proposed correlation gave the best prediction with an average absolute percentage error (AAPE) of 19.91%.

Experimental study of interfacial structure of horizontal air-water two-phase flow in a 101.6 mm ID pipe

The current work seeks to investigate the interfacial structure and establish an extensive experimental database in horizontal air–water two-phase flow in a 101.6 mm inner diameter pipe. A wide range of flow configurations are studied including bubbly, plug and slug flows. A flow visualization study using the high-speed video camera enables qualitative description of bubbly-to-plug and bubbly-to-slug transitions, while the database of local time-averaged two-phase flow parameters obtained by the four-sensor conductivity probe enables quantitative study on the evolution of the flow. Detailed measurements across the flow area are performed for nine test conditions at three different axial locations downstream of the inlet. Using this database, the effects of superficial liquid and gas velocities, and development length on the evolution of interfacial structure are investigated. Similar characteristics are observed as in a counterpart 38 mm ID horizontal two-phase flow facility, which include (1) the bubbles are found to be more concentrated near the top wall in bubbly flow as superficial liquid velocity decreases at a constant superficial gas velocity, while increasing superficial gas velocity promotes the growth of bubble layer thickness; (2) in bubbly-to-plug transition, the void fraction of small bubbles decreases and the size of small bubbles increases, while in bubbly-to-slug transition, opposite trends are observed. Meanwhile, different characteristics on the evolution of the interfacial structure are also observed, which indicates the effect of increasing pipe diameter. The bubbly-to-plug/slug transition is found to shift to higher superficial liquid velocities as pipe diameter increases. It is observed that the gas phase is more concentrated near the top wall in the large diameter pipe. As a result, the distance between bubbles is smaller and there is a higher chance for bubbles to coalesce into large bubbles. The critical void fraction where the bubbly-to-plug/slug transition initiates decreases as pipe size increases.

Computational analysis on disposal of coal slurry at high solid concentrations through slurry pipeline

ABSTRACTThe present study is conducted to investigate the flow characteristics of coal–water slurry having high solid concentrations in slurry pipeline using commercial computational fluid dynamics. An Euler–Lagrange multiphase approach is used to simulate the flow of coal–water slurry in 50, 100, and 150 mm diameter straight pipelines. The simulations are carried out using various turbulence models and the results obtained are compared with the experimental results presented in the literature. It is found that the shear stress transport (SST) k–ω turbulence model shows good agreement in comparison to other turbulence models. The SST k–ω turbulent scheme is used to solve the governing equations of two-phase model. Simulations are carried out for coal slurry velocity range 2–5 m/s. Numerical simulation results show that the pressure drop in pipeline increases non-linearly with increase in velocity, solid concentration, and particle size. Extensive simulation is also carried out to estimate the effect of pipe diameter on the pressure drop characteristics through pipeline. It is observed that the pressure drop decreases with the increase in pipe diameter. It is found that the particle sizes have significant influence on pressure drop, solid concentrations, and velocity distributions during the flow of coal–water slurry in a pipeline.

Experimental study on magnetic induction property of solenoid coil used in cooling water treatment system

Magnetic induction intensity is a critical factor to determine electromagnetic descaling effects. The current in a solenoid coil is an important parameter affecting the intensity of electromagnetic induction. In order to explore how winding pipe diameter, number of turns and frequency affect the current in the solenoid coil wrapped around the carbon steel pipes, the variation of the current with those factors is investigated by an experiment in which the method of series resistance is used. The peak current is obtained by measuring the voltage crossing series resistance. In this paper, the effect of series resistance on measuring current is analyzed. In order to reduce the influence of series resistance to electric current and ensure measurement reliability, 1.18Ω of the resistance is used for experimental measurements. The magnetic induction decreases with the increase of frequency and pipe diameter, and increases when the number of turns increases. The peak current decreases with the increase of frequency, number of turns, and pipe diameter, respectively. The results of this study shows that the variation of the current in the solenoid coil wrapped around the carbon steel pipes can be affected by various factors, and design guidance for the power of electronic anti-fouling equipment is provided.

Estimation of bedload discharge in sewer pipes with different boundary conditions using an evolutionary algorithm

Sediment transport is a complex phenomenon due to the nonlinearity and uncertainties of the process. The present study applies Gene Expression Programming (GEP) to develop bedload transport models in sewer pipes. In this regard, two types of bedload were considered: loose bed (deposition state) and rigid bed (limit of deposition state). In order to develop the models, two scenarios with different input combinations were considered: Scenario 1 considers only hydraulic characteristics and Scenario 2 considers both hydraulic and sediment characteristics as inputs for modeling bedload discharge. The results proved the capability of GEP in prediction of sediment transport and it was found that for prediction of bedload transport in sewer pipes Scenario 2 performed more successfully than Scenario 1. According to the outcome of sensitivity analysis, Frm (Modified Froude number) and d50/y (relative particle size) for rigid boundary and Frm for loose boundary had key roles in the modeling. The outcome of the GEP models also was compared with existing empirical equations and it was found the GEP models yielded better results. It was also found that pipe diameter affected the transport capacity of the sewer pipe. Increasing pipe diameter caused an increase in model efficiency. A pipe with a diameter of 305mm yielded to the best results.

Secondary vortex-based analysis of flow characteristics and pressure drop in helically coiled pipe

This article presents an investigation for the secondary flow characteristics and associated pressure loss in fluid flow through helically coiled pipe. Computational fluid dynamics is employed to analyze the pipe flow with various geometries, and the accuracy of the numerical methodology is validated by conducting corresponding experiments. The analysis performs a detailed parametric study involving the pressure loss, the secondary vortex motion, and the secondary vortex intensity for a range of coil diameters ( D; ranging from 300 to 3000 mm) and pipe diameters ( d; ranging from 50 to 90 mm). The pipe flow develops to a stable state with increase in coil diameter, while an increase in pipe diameter delays this development. Then, the secondary flow characteristics are analyzed to explore the pressure loss mechanism. The distorted streamline of secondary vortices and the enlarged deflection angle of secondary vortices are both factors contributing to the enhanced pressure loss. Furthermore, the effects of pipe flow development on the following flow characteristics such as the turbulence dissipation rate and the secondary vortex intensity are revealed. These characteristics all distribute regularly and reach lower values when pipe flow begins to a stable state.