Pipe Section Research Articles

Flow rheology of light foams generated from aqueous solutions of polyvinyl alcohol

Recent studies have shown that foam-assisted application of additives into a wet web has advantages over the conventional way of adding the chemicals into the pulp suspension before forming, e.g., increased mechanical retention as well as high dosage giving increased wet strength without impairing the sheet uniformity. To engineer processes utilizing this new technology, the complex flow behavior of applied foams must be quantified. At the minimum, the foam viscosity and the slip velocity at the solid surfaces need to be known to build practical models that can be used in analyzing and upscaling unit processes of the foam-assisted application. In this study, the rheological behavior was quantified for foams having polyvinyl alcohol (PVOH), a widely used strength additive chemical, as the surfactant. The foam density was varied between 100 g/L and 300 g/L, and the concentration of the PVOH solution was varied between 0.5% and 6.0% (w/w). The foams were generated with a commercial foam generator, and the rheological properties of the foams were measured by using a horizontal pipe bank. At the outlet from the generator, the volumetric flow rate, the absolute pressure, and the bubble size distribution of the foam were measured. In the measurement pipe section, the viscous pressure gradient and the slip velocity were measured, after which the foam was discharged to ambient air pressure. The viscosity and the dynamic surface tension of the PVOH solutions were quantified with commercial laboratory devices. In the viscosity analysis, the apparent shear rate was calculated from the volumetric flow rate, and the resulting apparent viscosity was translated to real material viscosity data by applying the Weissenberg-Rabinowitsch correction. The results indicated that PVOH foams can be described with high accuracy as shear-thinning power-law fluids where the detailed behavior depends on the foam density and the PVOH concentration. Slip flow, as usual, increased with increasing wall shear stress, but it was also dependent on the PVOH concentration, the air content, and the bubble size. For both the foam viscosity and the slip flow, a correlation was found that described the quantitative behavior of all the studied foams with good accuracy.

Study on quantitative risk assessment of girth weld failure of natural gas pipeline based on reliability

In order to avoid safety accidents caused by the failure of welding girth weld of long-distance gas pipeline, carry out quality investigation of girth weld of in-service pipeline, and perform quantitative risk assessment based on reliability for girth weld with difficulty in excavation, to effectively improve the effectiveness and economy of excavation point selection. In this study, using the probability-based weld structure failure prediction method through girth weld X-ray inspection results during the construction period, calculate the probability of fire and explosion due to leakage/rupture of girth welds in the natural gas pipeline and the impact range based on the basic risk evaluation information such as external environment and personnel distribution in the area of the pipe section where the welds are located. Identify excavation plan based on the evaluation results, and propose effective risk mitigation measures for nonexcavation sites. In the end, practical application cases are listed.

Experimental and numerical study on cooling performance of a novel earth-to-air heat exchanger system with an inlet plenum chamber

Previous studies have focused on the horizontal buried pipe section regarding the performance improvement of the earth-to-air heat exchanger, showing limited attention paid to the vertical air inlet section. In this study, we proposed a novel earth-to-air heat exchange system utilising an inlet plenum chamber (IPC-EAHE) to pre-treat the outdoor air in the inlet section. To evaluate its cooling performance, a numerical model was developed and validated based on a field experiment. The results showed a good agreement between simulated and experimental data, with a maximum absolute relative error of 4.43 % for the outlet air temperature. Then comparative studies between the IPC-EAHE and traditional EAHE are conducted under three airflow rates. Results indicated that the IPC-EAHE has a lower and more stable outlet air temperature than traditional EAHE. Compared to the traditional EAHE, the IPC-EAHE reduces the fluctuation of outlet air temperature by 53.13 %, 29.84 %, and 26.60 % under the airflow rates of 190 m3/h, 380 m3/h, and 570 m3/h, respectively. This improves the free cooling potential of EAHE for buildings. Moreover, the IPC-EAHE can reduce the buried pipe length by around 60.30 %, 53.0 %, and 50.0 % for three airflow rates, respectively. The friction resistance loss of the IPC section is at least 20 % less than that of the traditional EAHE vertical inlet section. The above results demonstrate that the IPC-EAHE offers greater renewable energy utilization efficiency and less buried pipe length than the traditional EAHE.

Numerical simulation of gas-liquid flow in inclined shale gas pipelines

Corrosion and perforation accidents often occur in shale gas gathering pipelines, which causes serious economic losses. The accumulation laws and flow field of shale gas gathering pipelines are revealed by OLGA and ANSYS Fluent simulation. Under different working conditions, the gas entering the pipeline contains 1.3∼3.1% water, which will condense in the pipelines with the decrease of temperature and form effusion. The effusion is mostly distributed in low-lying places and climbing pipe sections, which is consistent with the location of corrosion perforation. Through the three-dimensional simulation of the local upward pipe section, the effusion pipe will form vortices to accelerate the corrosion mass transfer. Further combine the high-temperature and high-pressure reactor experiment, the flowing causes of corrosion failure of shale gas gathering pipelines in the lower part of upward inclined pipeline sections are determined. Therefore, the lower part of the upward inclined pipeline section is a high-risk corrosion area.

A PBM-Based Procedure for the CFD Simulation of Gas–Liquid Mixing with Compact Inline Static Mixers in Pipelines

A compact static mixer for gas–liquid dispersion in pipelines is studied in this paper with a Reynolds averaged two fluid model approach. A procedure based on the lumped parameter solution of a population balance model is applied to obtain the bubble Sauter mean diameter needed to model the interphase forces. The gas distribution in the pipe is analyzed in two different operative conditions and the efficiency of the static mixer is assessed in terms of the gas homogeneity in the pipe section, with low coefficients of variations being obtained. A computational model to obtain the volumetric mass transfer coefficient, kLa, developed for partially segregated systems is applied finding kLa values comparable to those typically obtained with other static mixers. The proposed computational model allows us to locally analyze the oxygen transfer rate by observing the limitations due to gas accumulation behind the body of the static mixer, which leads to the local depletion of the driving force. Geometrical optimization of the static element is proposed, based on the analysis of gas–liquid fluid dynamics and of the interphase mass transfer phenomena.

Numerical modeling of transient non Newtonian thinning fluid flow

This study concerns a numerical simulation of transient non-Newtonian fluid flow in a hydraulic pipe resulting from sudden valve closure, commonly known as waterhammer or hydraulic shock. The fluid behaves as a law power model. The basic equations are solved numerically by the characteristic method to obtain average pressure and velocity across a right sections of pipe and, a flow velocity profile by a Runge–Kutta scheme of fourth-order. The results of the present model agree suitably with those found in the literature [1]. This study highlights the remarkable effects of the properties of this fluids on the pressure oscillations generated by hydraulic waterhammer compared to fluids of Newtonian behavior.

Pipe dent evaluation by acoustic emission during hydraulic pressure tests

Buried pipelines transporting gas and oil are influenced by surrounding soil during long time service. In many cases they are locally deformed by soil movement, especially by hard stones. External local pressure makes limited deformation of original shape of pipe diameter in time. Those types of local deformations are known as a dents. At those areas, the insulation layer is usually damaged and small defects (like cracks) are created in dents. Colonies of small stress corrosion cracks are observed. In this contribution, the evaluation of typical dents is investigated by hydraulic pressure tests, including the fatigue tests. Acoustic emission was used to detect the behaviour of dent in pipe section until the limit state. AE monitoring during pressure tests gave very clear answer of defect activity vs. loading pressure. Parallel to this monitoring, another NDT method, MMM was used with promising results.

Engineering method for calculating fluid flow in pipes with different cross sections in energy and technological processes

The flow of liquid through pipes with various configurations is found in many energy and technological processes. Knowledge of the distribution of velocity and flow through these pipes allows hydrological engineers to find resistance through the pipes and optimize the fluid pumping process. The article suggests a simple engineering method for finding the velocity over pipe sections

Cause Analysis of Economizer Tube Leakage in a Biomass Power Plant

Aiming at the leakage of economizer tube in a biomass power plant, the leakage mechanism of economizer tube was studied by means of macro analysis, chemical composition analysis, metallographic structure, micro Vickers hardness test and scanning electron microscope. The results show that there is no misuse of materials or unqualified chemical composition in the leaked economizer tube; The metallographic microstructure is ferrite + pearlite, and the spheroidization level is between 2.0 and 2.5, indicating that there is no obvious spheroidization in the pipe section submitted for inspection; At the same time, the micro Vickers hardness value did not decrease significantly; The outer wall of the pipe is yellowish brown and there is delamination and peeling of attachments. A leakage hole can be seen in the middle of the pipe section, and there is obvious thinning at the edge of the hole, indicating that there is corrosion thinning. The chemical components of the corrosion products are mainly Fe and O, and contain a certain amount of Cl, s, P, Si, K, Ca and other alkali metal elements. Therefore, it can be inferred that the main cause of economizer pipe leakage is corrosion thinning.

Three-dimensional analysis of the stress-strain state for straightening pipes on skew-roll straightening machines with special roll profiling

In order to increase the competitiveness of domestic metal products, in particular pipes, it is necessary to ensure their compliance with international standards in terms of the main quality indicators. The pipe straightening process provides quality indicators such as straightness and cross-sectional shape. Skew-roll pipe straightening machines are the most common and most effective for straightening pipes of small and medium diameters. The most modern are six-roll pipe straightening machines with special roll profiling, which provide straightening of two types: in the caliber of the profiled rolls and at the step between the roll clamps. But the lack of knowledge about the regularities of straightening pipes holds back the wide implementation of such machines. In the work, a finite element model was developed and with its use, a study of the influence of the straightening process parameters in profiled rolls with symmetric and asymmetric profiling of the extreme pairs of rolls on the indicators of pipe straightness and straightening force was carried out. According to the results of their implementation, it was established that straightening the pipe in gauge and pitch allows to reduce the residual curvature of the pipe by almost three times with a 2.5 times smaller overlapping of the middle rolls relative to the outer ones. At the same time, the force on the most heavily loaded middle rolls increases almost twice, which should be taken into account in view of the possibility of ovality in the section of thin-walled pipes. The use of additional asymmetric profiling of the extreme rolls with step adjustment practically does not affect the quality of straightening in the gauge, increases the quality of straightening at the step by up to 15 %, while reducing the maximum straightening force by 5—7 %. The developed finite-element model allows determining the rational values of rolls overlaps to ensure the minimum residual curvature of the pipes.

Direct Measurement of Beam-Induced Heating on Accelerator Pipes With Fiber Optic Sensors: Numerical Analysis Validation

In the field of accelerator physics it is crucial to account for heating caused by the passage of high intensity beams into accelerator components. This phenomenon is known as Radio Frequency (RF) Beam Induced Heating (BIH) and requires, other than an accurate design stage, to constantly monitor temperature-related parameters during the accelerator operations. This enables to warn for critical malfunctions and to prevent possible damages. Monitoring needs to meet various requirements, such as multiplexing capabilities, distributed sensing possibilities, and robustness in harsh environments. Fiber Bragg Grating sensors (FBGs) have been proven to be an ideal solution that meets all these requirements. This study aims to validate the use of FBGs for direct measurement of RF BIH. A section of the beam pipe in the CERN Large Hadron Collider was modeled in terms of impedance, and the resulting RF BIH was computed based on the traveling beam. The results of the numerical simulation were compared with experimental data obtained by FBGs installed along the beam pipe. The analysis shows that FBGs can be a valuable beam diagnostic tool for monitoring accelerated high energy particle beams by measuring RF BIH and may provide useful insights for improving the design and operation of future accelerators. The study highlights the significant advancements of FBG technology in direct temperature measurement and assessment of RF BIH and serves as a promising solution for mitigating RF BIH in the demanding environment of particle accelerators.

FLUID FLOW AND HEAT TRANSFER CHARACTERISTICS OF A CENTERED-WICK HEAT PIPE WITH ADDITIONAL WORKING FLUID: EXPERIMENTAL STUDY WITH VISUALIZATION

This article describes the experimental study of the centered-wick heat pipe with additional working fluid. A semi-transparent heat pipe is employed, and the heat transfer experiments are conducted in three orientation modes: horizontal, vertical, and sideways. The wick structure is a sintered copper powder, and the working fluid is water. The heat pipe has a small gap between the wick structure and the container wall. In each orientation mode, a condenser section of the heat pipe is water-cooled with a cooling jacket, and an evaporator section is heated with a heater. Fluid-flow and phase-change phenomena in the heat pipe are captured by using a video camera, and the temporal changes in the temperatures of the heat pipe are obtained by using thermocouples. Due to the additional working fluid, liquid slugs are found in vapor flow channels. The liquid slugs can be categorized into two types: a dynamic liquid slug and a static liquid slug. The experimental results demonstrate that the dynamic and static liquid slugs are distributed more effectively in the horizontal orientation mode. Thus, the thermal resistance of the heat pipe tends to be smaller and the maximum heat input to the heat pipe is larger in the horizontal orientation mode than in the other two orientation modes. The experimental results also confirm that the small gap is effective in the horizontal orientation mode. The additional working fluid is stored in the gap, which increases the thermal performance of the heat pipe.

Fluid Flow and Heat Transfer Characteristics of a Centered-wick Heat Pipe with Additional Working Fluid: Experimental Study with Visualization

This article describes the experimental study of the centered-wick heat pipe with additional working fluid. A semi-transparent heat pipe was employed, and the heat transfer experiments were conducted in three orientation modes: horizontal, vertical, and sideways orientation modes. The wick structure was a sintered copper powder, and the working fluid was water. The heat pipe had a small gap between the wick structure and the container wall. In each orientation mode, a condenser section of the heat pipe was water-cooled with a cooling jacket, and an evaporator section was heated with a heater. Fluid-flow and phase-change phenomena in the heat pipe were captured by using a video camera, and the temporal changes in the temperatures of the heat pipe were obtained by using thermocouples. Due to the additional working fluid, liquid slugs were found in vapor flow channels. The liquid slugs can be categorized into two types: a dynamic liquid slug and a static liquid slug. The experimental results demonstrated that the dynamic and static liquid slugs were distributed more effectively in the horizontal orientation mode. Thus, the thermal resistance of the heat pipe tended to be smaller and the maximum heat input to the heat pipe was larger in the horizontal orientation mode than in the other two orientation modes. The experimental results also confirmed that the small gap was effective in the horizontal orientation mode. The additional working fluid was stored in the gap, which increased the thermal performance of the heat pipe.

Effect of Welding Thermal Cycle on the Forming in a Section of Straight-Seam Pipes with Large Diameters

Effect of Welding Thermal Cycle on the Forming in a Section of Straight-Seam Pipes with Large Diameters

Full-scale tests of transporting pipeline sections : A review and consequences to our investigations

Hydrocarbon transport pipelines' safe operation is an economic and environmental interest. These pipelines are typically designed for static loads, but during their long-time operation - due to pressure changes and environmental impacts - they are also subject to cyclical loads. The individual pipe sections are connected by girth welds, which represent potential sources of hazards in terms of damage. In order to assess the reliability of girth welds, full-scale tests are carried out under simple and complex loads. The purpose of this article is twofold. On the one hand, summarize the full-scale tests on transmission pipelines, with special attention to the tests on girth welds; on the other hand, based on this, draw conclusions for the design and implementation of our own full-scale tests.

Three-Level Safety Evaluation of Suspended Sections of Underwater Buried Pipelines

The uneven riverbed, as well as the impact and erosion suspended on by water flow, make the underwater crossing pipeline vulnerable to exposure and suspension. Under the influence of water flow, the span of a suspended pipe section steadily grows, jeopardizing the integrity of pipeline operation. In order to investigate the mechanical properties and failure behavior of the suspended section of the crossing pipeline under the influence of water impact, according to the failure mechanism of the pipeline, the statics and dynamics analysis of the pipeline is carried out, and the graded safety evaluation technique of the crossing pipeline with suspended section is presented. First, a “static strength safety evaluation under static load condition” (level 1) is carried according to the mechanical features and stress state of the pipeline's suspended section. Second, the "resonance safety evaluation under dynamic load" (Level 2) is carried in accordance with the correlation between the natural vibration frequency of the suspended pipeline and the vortex emission frequency of water flow. Finally, the periodical change process of the pipeline's alternating stress is studied, the fatigue damage and fatigue life of the pipeline are solved, and the "fatigue strength safety evaluation under dynamic load condition" (level 3) is performed. Thus, a three-level safety assessment procedure for pipelines crossing the suspended section is suggested. The pipe stabilizing measures that fall short of the safety evaluation are suggested, and based on the calculation example, a specific calculation process is provided. This information serves as a theoretical guide for the safety evaluation of the suspended section of the underwater crossing pipeline.

Decay of secondary motion downstream bends in turbulent pipe flows

Decay of secondary motion downstream 180° pipe bends is investigated using large-eddy simulations for the bend radii of 1≤rB/dh≤3.375 at a Reynolds number of Reh=10 000. The velocity and turbulence characteristics are validated against experimental data for a straight pipe section as well as against experimental and direct numerical simulations data for a 90° pipe bend. As the bend radius decreases, a larger magnitude of turbulence intensity is induced immediately downstream of the bend, and for the largest magnitude, the highest gradient of the decay turbulence intensity is observed. As a result, the recovery length needed to reestablish the velocity profile downstream of the pipe bend decreases. Turbulence is transported at a higher rate, indicating that the recovery of the velocity profile is driven by turbulence transport. Secondary motions are induced by the curvature of the pipe bend, and as the bend radius decreases, the magnitude of the secondary motion increases. The results show how the secondary motion decay in magnitude as the flow moves downstream the pipe bend. At the outlet of the bend, secondary motions are dominating at the walls and within the bulk flow. As the fluid moves further downstream, the secondary flows dominate close to the walls, and at a length of x/dh=5, a negligible difference in secondary motion is observed for the different bend radii.

Acoustic emission monitoring of abrasion and corrosion in double-walled pipelines

At KRONOS TITAN, double-walled pipelines are used in production of Titandioxid. An abrasive medium is transported in the inner pipe at high temperatures. In the outer pipe, cooling water ensures that the process is cooled down. During the process, it is important that no abrasion leads to complete wall erosion and thus to leakage between the inner and outer pipe. During a test campaign lasting several months, a section of such a pipe was instrumented with acoustic emission measurement system on the outer pipe and the abrasion process in the inner pipe was monitored with AE until the removal of the pipe section. Different AE-signal parameters (Events, Hits, Energy and Frequency) were investigated regarding their suitability and are discussed in this contribution. The results of the acoustic emission measurements with regard to the location and progress of damages were then compared and verified with classic NDT test results.

An experiment generates a specified mean strained rate turbulent flow: Dynamics of particles

This study aimed to simulate straining turbulent flow empirically, having direct similarities with vast naturally occurring flows and engineering applications. The flow was generated in 100<Reλ<500 and seeded with passive and inertial particles. Lagrangian particle tracking and particle image velocimetry were employed to extract the dynamics of particle statistics and flow features, respectively. The studies for axisymmetric straining turbulent flow reported that the strain rate, flow geometry, and gravity affect particle statistics. To practically investigate mentioned effects in the literature, we present the behavior of both passive and inertial particles from the novel experiment conducted on initially homogeneous turbulence undergoing a sudden axisymmetric expansion. We represent the result with two different mean strains and Reynolds–Taylor microscales. However, this study, in contrast to the previous studies, considers the fields of inertial particles in the presence of gravity. The result discloses that the novel designed and conducted experiments simulated the flow satisfactorily. Then, the particle behavior in such flow showed the effectiveness of the flow distortion on particle dynamics such as velocity root mean square and Reynolds stress. Straining turbulence flow is subject to many industrial applications and physics studies, such as stagnation points, external flow around an airfoil, internal flow in changeable cross section pipe, expansion in the engine mixing chamber, and leading edge erosion. This study's conclusion could apply constructively to these areas.

Energy and exergy analysis and optimization of a novel heating, cooling, and electricity generation system composed of PV/T-heat pipe system and thermal wheel

The present study aims to compare the energy and exergy performances of photovoltaic/thermal-thermal wheel (PT) and photovoltaic/thermal-heat pipe-thermal wheel (PHT) systems. These systems are able to preheat/precool the outside air in the cold/hot season and supply part of the electricity needed by a building. In the PT system, the ambient air exchanges heat directly with the photovoltaic panels, while in the PHT system, the evaporator section of heat pipes located under the panels transfers the heat received from the panels to the air stream through the condenser section of heat pipes. The annual useful energy and exergy produced by the system were taken as objective functions, the two-objective optimization of the systems was performed, and the performances of the optimal systems were assessed. Overall annual analysis of outcomes showed that the highest useful energy output is achieved by the optimal PT system which outperforms by 2.1% than that of the optimal PHT system, while the maximum useful exergy yield is attained by the optimal PHT system, which is 5.1% higher than that of the optimal PT system. The thermodynamic performance improvement of the PHT system is due to the electricity production increment by recovering the waste heat of photovoltaic panels.