Annular Pipe Research Articles

Study on Pneumatic Conveying Characteristics of Suction Nozzle with Annular Injection Pipe

Study on Pneumatic Conveying Characteristics of Suction Nozzle with Annular Injection Pipe

Study on Pneumatic Conveying Characteristics of Suction Nozzle with Annular Injection Pipe

Study on Pneumatic Conveying Characteristics of Suction Nozzle with Annular Injection Pipe

CFD Modelling of Dispersed Bubble Two-Phase Flow in a Concentric Annulus Pipe

CFD Modelling of Dispersed Bubble Two-Phase Flow in a Concentric Annulus Pipe

Experimental and CFD simulation of slurry flow in the annular flow path using two-fluid model

The current study is allocated to experimental evaluation of the multiphase flow of fine solid particles (FSPs) as well as comprehensive numerical study in an annular space under static, laminar, and turbulent flow conditions with consideration of the inner pipe eccentricity and rotation. The experimental investigation was carried out using an annular pipe flow loop. The numerical modeling and simulation of the multiphase flow in the annular space have been performed using the Euler-Euler approach. The unsteady-state multiphase model based on the kinetic theory of granular flow (KTGF) is developed to investigate the particulate flow characteristics in the annular space. Moreover, Standard and Realizable k-ε turbulence models used to predict turbulence in this study. The Realizable Per-Phase turbulence model with new corrected coefficients (C2=4.2,C3=1.3,CT=0.0131,σk=1,σε=1.2) is calibrated to predict the pressure drop along the annular pipe for solid-liquid multiphase flow. Comparison between numerical and experimental analyses showed that under both flowing and static conditions, the simulation results are in good agreement with experimental data. Based on the error estimation model, the CFD model's accuracy for pressure drop and FSPs concentration prediction is 99% and 95%, respectively. The trends of the variation in particle concentration along the annular pipe were investigated for different flow velocities (0.05–2.5 m/s) and different inner pipe rotations of 500, 1000, and 1500 rpm. The results also showed that the higher particle settling occurred at the critical inclination angles of 45–60°.

Superhydrophobic annular pipes: a theoretical study

Abstract

Conceptual design of reactor system for hybrid micro modular reactor (H-MMR) using potassium heat pipe

Hybrid micro modular reactor (H-MMR) combining MMR with renewable energy and energy storage systems (ESS) is designed using heat pipe. H-MMR could produce 10 MW of electric power more flexibly and efficiently through load following. LOCA accident is precluded in advance as there is no primary coolant due to the use of potassium heat pipe. Reactor solid core consist of hexa-annulus UN fuel with a heat pipe inserted, which connects a sodium pool of intermediate heat exchanger (IHX). The annular gap wick heat pipe (ACHP) using potassium is optimized to maximize the heat transport performance. Reactor core configuration is designed through core analysis and thermal analysis using 1D lumped finite differential method. Reactor core of H-MMR make 18 MW of thermal power for 56 years without refueling when diameter of heat pipe is 22 mm. The feasibility of heat pipe safety system and sodium pool is evaluated in normal operation. Reactor vessel auxiliary cooling system (RVACS) is designed to cool down decay heat within safety margin using implicit transient analysis.

Effects of radius ratio on turbulent concentric annular pipe flow and structures

The effects of radius ratio on fully-developed turbulent concentric annular pipe flow and structures are investigated using direct numerical simulations (DNS). In order to study the radius ratio effects on the flow, four radius ratios of a concentric annular pipe (for Ri∕Ro=0.1–0.7) are compared at a fixed Reynolds number. Here, Ri and Ro are the radii of the inner and outer pipes, respectively. It is observed that the radius ratio influences the interaction of two boundary layers developed over the inner and outer cylinder surfaces, and has a significant impact on the turbulent flow structures and dynamics. The characteristics of the flow field are investigated in both physical and spectral spaces, which include the analyses of the first- and second-order statistical moments, budget balance of the transport equation of Reynolds shear stress, two-point correlation coefficients, and premultiplied spectra of velocity and vorticity fluctuations.

Thermal and Flow Characteristics in a Concentric Annular Heat Pipe Heat Sink

A concentric annular heat pipe heat sink (AHPHS) was proposed and fabricated to investigate its thermal behavior. The present AHPHS consists of two concentric pipes of different diameters, which create vacuumed annular vapor space. The main advantage of the AHPHS as a heat sink is that it can largely increase the heat transfer area for cooling compared to conventional heat pipes. In the current AHPHS, condensation takes place along the whole annular space from the certain heating area as the evaporator section. Therefore, the whole inner space of the AHPHS except the heating area can be considered the condenser. In the present study, AHPHSs of different diameters were fabricated and studied experimentally. Basic studies were carried out with a 50 mm-long stainless steel AHPHS with diameter ratios of 1.1 and 1.3 and the same inner tube diameter of 76 mm. Several experimental parameters such as volume fractions of 10–70%, different air flow velocity, flow configurations, and 10–50 W heat inputs were investigated to find their effects on the thermal performance of an AHPHS. Experimental results show that a 10% filling ratio was found to be the optimum charged amount in terms of temperature profile with a low heater surface temperature and water as the working fluid. For the methanol, a 40% filling ratio shows better temperature behavior. Internal working behavior shows not only circular motion but also 3-D flow characteristics moving in axial and circular directions simultaneously.

Flow structure development due to water injection into the annulus of heavy oil pipe flow. (Dept. M.)

This work investigates the flow structure development due to the injecting water into the annulus of heavy oil pipe flow. Numerical simulation of the axisymmetric core-annular turbulent flow is carried out using the standard κ-ω model. The flow field and flow characteristics are investigated using FLUENT 6.3.26. The core-annular flow of heavy oils-water in 15.24 cm diameter pipe, with three core diameters is considered. The influence of flow parameters upon the development of axial and radial velocity, turbulent kinetic energy, turbulence intensity, and strain rate profiles are investigated. Results show that the flow development depends on the core to outer diameters ratio, oil viscosity, flow velocity, and water loading ratio. As oil's viscosity increases, the flow structure develops faster towards fully- developed one. Fully- developed velocity profiles show uniform distribution in oil's core, while all velocity changes occur in water flowing in pipe annulus. The flow in the core region seems to be as rigid body carried by annular water flow. It has been demonstrated that major changes in flow structure occur at the oil-water interface

Experimental and Numerical Study of Wax Deposition in a Laboratory-Scale Pipe Section under Well-Controlled Conditions

Detailed local and averaged measurements of wax deposition in an annular pipe section were conducted and combined with a comprehensive simulation model. The objective of the study was to contribute...

Performance of counter flow membrane-based annular pipe liquid desiccant air conditioner

The present study comprises an experimental and numerical simulation of a counter flow membrane-based annular pipe liquid desiccant air conditioner (AP_LDAC) system. The experimental rig was constructed by using DuPont™ Tyvek® Solid as semi-permeable membrane and it has simplier structure compared to other types of membrane-based dehumidifiers. To validate the numerical data, experiments were carried out at different air side Reynolds (Re) number. The 3D numerical simulation of counter flows of the AP_LDAC system presented good agreement (R-square: 0.9659) with experimental data, as a result of the validation. Once the reliability of numerical data were verified, the mass transfer coefficient of counterflow obtained by designed system was revealed and optimized numerically by investigating for various aspect ratios, Reynolds (Re) and Schmidt (Sc) numbers. The derived Sh model was predicted over COMSOL Sh numbers with error interval from 0.1% to 10%. The effect of air inlet temperatures on temperature, concentration distributions and efficiency of the optimized AP_LDAC system were also investigated. The dehumidification efficiency was found as 99% for the maximum aspect ratio and the lowest Re number.

X-ray measurements of thin liquid films in gas–liquid pipe flow

This paper presents a method for reconstructing the thickness profile of the thin liquid film being present in steady, fully developed gas–liquid annular pipe flow, taking advantage of nonintrusive X-ray measurements. Experiments have been performed with low liquid loading, annular flows, in a near horizontal pipe system (inclination +2.5°), using a high-density gas (SF6) and Exxsol D60 oil. Special care was taken to ensure the flows were fully developed, and statistically steady. The superficial gas velocity was maintained at a constant value of 10 m/s, while the superficial liquid velocity was varied between 0.5 mm/s and 42 mm/s. The X-ray measurements were supplemented by gamma ray densitometer data and isokinetic data. An explicit mathematical method is presented, whereby the shape and thickness of very thin liquid films can be reconstructed if X-ray images of the flow have been obtained from two independent directions: one with a vertical view of the pipe, and another with a horizontal side view. The method can be straightforwardly applied to cases where the film volume dominates the total volume of droplets suspended in the gas phase. This condition is generally satisfied for the experiments presented in this paper, as verified by isokinetic measurements.Mean liquid hold-up values determined by gamma densitometer are in reasonable agreement with the X-ray results. It is found that the mean film thickness at any position on the pipe wall increases with the superficial liquid velocity. While the film thickness is maximal at the pipe bottom in virtually all experimental cases, its profile exhibits multiple local maxima and minima, with the smallest thickness apparently 20°–30° away from at the pipe top. The presented film reconstruction method is highly sensitive; even at extremely low liquid levels, with a superficial liquid velocity less than 0.01% of the mixture velocity, the film and its thickness profile are clearly detected. An analytical fit for the film profile as a function of perimeter angle and superficial liquid velocity is given. The fit captures the main features of the profile as derived from X-ray measurements, for thin films with maximum thickness less than 5% of the pipe diameter.

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

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

Nano-particle deposition in laminar annular pipe flows

The transport and deposition of nano-particles in annular pipe flows under laminar conditions were studied. The Lagrangian particle tracking method was used to simulate the Brownian diffusion of ultrafine solid particles in a three-dimensional domain. The effects of nano-particle size, flow rate, inner and outer pipe diameters, pipe length, and temperature were studied. The computational models for the deposition of nano-particles in tubular, as well as annular pipe flows, were validated. Furthermore, using the CFD simulations and the Lagrangian particle tracking results, a new correlation for evaluating the deposition fraction of nano-particles in annular pipe flows was developed. The presented results could provide guidelines for evaluating nano-particle transport and deposition in annular pipes.

The cross-sectional curvature effect of twisted tapes on heat transfer performance

This study reports the cross-sectional curvature effect resulted from a twisted tape fabrication or installation into an annular pipe on the enhancement of heat transfer to pay attention to the use of twisted tapes more efficiently. Six different twisted tapes having two twist ratios (3 and 4) and three curve ratios (1.761, 2.252 and 3.271) in the Reynolds number range from 5840 to 30,900 were numerically analyzed. The analysis method was validated with three different experimental results from loose-fit to tight-fit of a twisted tape. According to polyhedral mesh element analysis of curved cross-sectional twisted tapes, capable of having better compatibility with experimental results, Nusselt numbers increased with increasing curve ratio and decreasing Reynolds number and twist ratio. While the curved twisted tape is more efficient than the smooth tube, losses on heat transfer efficiency are observed compared to the classical twisted tape. Although the losses caused by the curvature on the twisted tape appear to be insignificant at high curve ratios, the effect of low curve ratios increases significantly. For the lowest CR and the highest TR under analysis conditions, it was observed that TT lost 28 % of its normal productivity increase due to this effect.

On the rise characteristics of Taylor bubbles in annular piping

A three-dimensional phase-field lattice Boltzmann method has been applied to investigate the rise of Taylor bubbles within annular pipes. The approach couples the conservative phase-field model with a velocity-based lattice Boltzmann scheme. The implementation uses 27 discrete velocities to resolve both the interfacial dynamics and the hydrodynamics. To assist numerical stability for the high-density ratio, two-phase flows a weighted multiple-relaxation-time collision operator is employed. This paper makes contributions in three areas. First, the model is employed to capture the behaviour of Taylor bubbles in five combinations of vertical annular pipes, with results compared to experimental findings from the literature for air-water flows. From this, shortcomings were identified in the ability of existing correlations to accurately predict rise velocities for bubbles in various liquids. Second, the effect of pipe inclination on the rise behaviour of the bubbles was investigated. From the findings, a preliminary correlation describing the rise velocity was proposed. The first two components of the study were conducted with the Taylor bubble rising in stagnant fluid. The final component of this study imposed liquid flow in a concentric annular pipe to determine the impact of this on the bubble’s dynamics. The liquid velocity was defined through a Reynolds number based on the average inlet velocity up to an absolute value of 10. The viscosity was varied to examine Morton numbers from 2.56e-3 to 6.55e-5. To this end both co- and counter-current flow was analysed and a distribution parameter proposed to capture the liquid-gas interaction. To extend this work, future investigations will look to extend the parameter range assessed to ensure the universality of the correlations identified.

Development of closure relations for the motion of Taylor bubbles in vertical and inclined annular pipes using high-fidelity numerical modeling

This study analyses the flow of Taylor bubbles through vertical and inclined annular pipes using high-fidelity numerical modeling. A recently developed phase-field lattice Boltzmann method is employed for the investigation. This approach resolves the two-phase flow behavior by coupling the conservative Allen–Cahn equation to the Navier–Stokes hydrodynamics. This paper makes contributions in three fundamental areas relating to the flow of Taylor bubbles. First, the model is used to determine the relationship between the dimensionless parameters (Eötvös and Morton numbers) and the bubble rise velocity (Froude number). There currently exists no surrogate model for the rise of a Taylor bubble in an annular pipe that accounts for fluid properties. Instead, relations generally include the diameter of the outer and inner pipes only. This study covered Eötvös numbers between 10 and 700 and Morton numbers between 10−6 and 100. As such, the proposed correlation is applicable to concentric annular pipes within this range of parameters. An assessment of the correlation to parameters outside of this range was made; however, this was not the primary scope for the investigation. Following this, the effect of pipe inclination was introduced with the impact on rise velocity measured. A correlation between the inclination angle and the rise velocity was proposed and its performance quantified against the limited experimental data available. Finally, the high-fidelity numerical results were analyzed to provide key insights into the physical mechanisms associated with annular Taylor bubbles and the shape they form. To extend this work, future studies on the effect of pipe eccentricity, diameter ratios, and pipe fittings (e.g., elbows and risers) on the flow of Taylor bubbles will be conducted.

THE USE OF STEEL ARC WELDING PIPES ON TANK FARMS OR OIL AND GAS INDUSTRY OBJECTS

Recently, the use of high-strength steels has significantly reduced the cost of pipeline materials. However, alignment, welding, inspection, and coating costs typically account for about 20 % of the total cost of the pipeline. Due to invention of new arc welding technologies, potential to reduce costs in the construction of pipelines is being created. The need to build large-diameter pipelines over long distances has led to an increase in the need to improve the performance of ring welding of the pipeline. Electric semi-automatic gas-metal welding remains the dominant technology of annular pipe welding. The article describes the processes of arc welding, control of the microstructure of the weld, welding material for pipelines in aggressive environments, the current state of welding of main pipelines in the Russian Federation, innovative welding technologies leading to a further significant increase in the performance of arc welding. The most promising method of welding in the construction and repair of pipelines is arc welding with coated electrodes. As a rule, in semi-automatic welding of joints of sections of trunk pipelines, solid wire and protective gas are used as the electrode. Improving the productivity of welding and installation works can be achieved by introduction of new energy-efficient welding methods, partial or complete replacement of existing welding equipment, the use of innovative welding materials.

Influence of domain size on direct numerical simulation of turbulent flow in a moderately curved concentric annular pipe

Direct numerical simulation (DNS) of turbulent flow in a concentric annular pipe was performed using a pseudo-spectral method computer code. In order to study the effects of computational domain size on the turbulence statistics, 12 test cases of different domain sizes are compared. The characteristics of the velocity field are examined at two different Reynolds numbers. It is observed that the predictive accuracy of the first- and second-order statistics is sensitive to the axial and azimuthal domain sizes. It is also found that the scales and dynamics of turbulence structures vary with the surface curvature of the concave and convex walls. The characteristic length scales of the turbulence structures are identified through a spectral analysis, and it is observed that a minimum computational domain is required in order to accurately capture the near-wall streaky and hairpin structures of a concentric annular pipe flow using DNS.

Experimental Investigation of Vertical Downward Two-Phase Flow in Annulus

Abstract A limited amount of work exists on gas–liquid flow in vertical pipe annulus, and, to the knowledge of the authors, there is no work on the literature to characterize vertical downward two-phase flow in pipe annulus. In the petroleum industry, downward two-phase in annulus is encountered on liquid-assisted gas-lift (LAGL) unloading and production operations. This study presents experimental data for pressure gradient, liquid holdup, and flow regimes for vertical downward two-phase (air and water) flow in pipe annulus. Also, the applicability of two-phase flow models are evaluated. The experimental results show that the liquid holdup is consistently higher for downward flow in annulus than in pipes for the annular flow regime, and these differences are as high as 45%. When the flow regime map for downward flow in annulus is compared with the ones in the literature for flow in pipes, it is observed that the intermittent flow in pipes occurs at lower liquid velocities than flow in annulus. The comparison between experimental data and model results also shows some discrepancy for liquid holdup and pressure gradient. These differences are high for annular and intermittent flow regimes, with errors of 100% for the liquid holdup and 200% for pressure gradient. However, the errors for bubble flow regime are much smaller, generally lower than 20%.