Pipe Section Research Articles

Finite-Element Modeling of the Temperature Effect on Extended Avalanche Damage of Gas Main Pipelines.

The dynamic stress-strain state and fracture of a steel main gas pipe section between supports with a straight-through crack was analyzed with consideration of the temperature effect on changes in the mechanical properties of the pipe material. The numerical solution of the problem was implemented in the ANSYS-19.2/Explicit Dynamics software package. The process of fracture in a section of the gas pipeline "Beineu-Bozoy-Shymkent" with a linear crack in the temperature range of -40 °C to +50 °C at the operating pressure of 7.5 MPa and critical pressure equal to 9.8 MPa was considered. As a result, it was found that at the initial growth of the internal pressure from working pressure to critical pressure, the length of the crack doubled. At the same time, the process had a local characteristic. Further development of the crack had the nature of avalanche fracture and depended on the temperature of the steel pipeline. With increasing temperature, there was also an increase in the length of the crack at the avalanche fracture. Thus, at a temperature of 40 °C, the crack lengthened 67.75-fold; at a temperature of -10 °C, the crack lengthened 68-fold; at a temperature of +20 °C, the crack lengthened 68.25-fold; and at a temperature of +50 °C, the crack lengthened 68.5-fold. In this work, this difference was 75% of the initial crack length. This fact will be used for further development of the technique of strengthening damaged pipe sections using bandages.

Experimental investigation on flow patterns and pressure gradients of shale oil–water flow in a horizontal pipe

With the growing demand for hydrocarbon resources and the depletion of conventional oil and gas reservoirs, the development of shale oil will become popular. As the shale oil fields gradually enter the middle and late stages of exploitation, the water content reaches as high as 60–80 %. Analyzing the flow characteristics of shale oi–water flow during high water content can help optimize the range of flow parameters and improve pipeline transportation efficiency. However, research on shale oil–water flow patterns and pressure drop prediction models is still lacking. Therefore, this work conducted shale oil–water flow experiments in the multi-test section pipe flow loop, considering the temperatures (40–70 °C), mixture velocity (0.2–1.2 m/s), and water contents (60–80 %). The flow patterns of shale oil–water flow are studied, and the flow pattern maps are created. Moreover, the influence factors on pressure gradient are analyzed, including pipe diameter, water content, mixture velocity, and temperature. Eventually, the pressure drop prediction models are modified based on the pressure gradient and holdup experimental data. The results show that a thin oil film and an oil-sticking layer are adhered to the pipe wall at 40 °C and 50 °C, respectively. The mixture velocity increased from 0.4 m/s to 1.2 m/s, and the pressure gradient increased by 69.89 % when the temperature and water content are constant. The lubrication coefficient is introduced in stratified flow (ST) and three-phase stratified flow (TPS) models, and the pipe flow friction coefficient is modified in dispersed flow (DF) and intermittent flow (IF) models. Moreover, the average relative deviations between experimental data and calculated values of ST, TPS, DF, and IF modified models are 4.49 %, 4.23 %, 4.40 % and 5.17 %, respectively. Therefore, surface wettability reduces the friction between the oil phase and the pipe wall, and the oil film and oil-sticking layer increase the pipe flow resistance.

Natural frequencies and stability for Z-shaped fluid-conveying pipes with constrained-layer damping – Semi-analytic modeling with experimental validation

As the common fluid-conveying component, pipe structures are susceptible to excessive vibration due to internal fluid and external excitation. Constrained-layer damping (CLD) is commonly applied to suppress structural vibrations. However, effective modeling and vibration suppression analysis for Z-shaped fluid-conveying pipes are lacking to explore novel dynamic behaviors. This paper presents a dynamic model for analyzing the three-dimensional vibration of Z-shaped fluid-conveying pipes treated by partial CLD based on the semi-analytical method. Utilizing Timoshenko beam theory and calculating the centrifugal, Coriolis, and inertial force of fluids, the energy of straight and curved fluid-conveying pipes treated by CLD is derived. Based on the Lagrangian energy function, the equation of motion is obtained by using the Rayleigh-Ritz method. The improved artificial spring set is deployed to model the interaction of pipe sections and the non-uniform constraint distribution of clamps. Modal parameters are obtained by solving characteristic equations. The proposed method is verified by comparisons with references and modal experiment results. Frequency parameters, damping effects, and stability are analyzed under various fluid, geometric, and CLD parameters. In conclusion, a novel dynamic model is provided for analyzing the vibration and stability of the Z-shaped fluid-conveying pipe treated by CLD, which lays a foundation for vibration suppression research of fluid-conveying pipe systems.

Thermal performance of a large-diameter thin flattened heat pipe with novel composite wick structure

Flattening large-diameter cylindrical heat pipes to fabricate thin heat pipes can significantly improve their heat transfer performance in theory, but their appropriate wick structures and thermal performance are still unclear. In this work, a novel composite wick structure sintered from spiral woven mesh and orthogonal woven mesh was developed for large-diameter thin flattened heat pipes. Their diameter and thickness were 8 and 1.0 mm, respectively. Seven types of wick structures for the experimental heat pipes were designed to investigate the effects of the length and position of the orthogonal woven mesh on the thermal performance. The results indicated that based on the spiral woven mesh, sintering the orthogonal woven mesh in the evaporator and adiabatic sections of the heat pipe can significantly improve the thermal performance. Compared with the single spiral woven mesh wick, the maximum heat transport capacity of the experimental heat pipe with optimal composite wick increased by 41.67%, and the evaporation and total thermal resistances decreased by 68.41% and 61.49%, respectively. This study provided very useful guidance for improving the thermal performance of the large-diameter thin flattened heat pipes for cooling laptops.

Air-Coupled Ultrasonic Arrays for Assessment of Pipe Internal Geometry and Surface Condition.

This article explores what useful information can be retrieved from pipeline interiors using an air-coupled ultrasonic array. Experiments are performed using an array, custom array controller, and supporting electronics controlled by a Raspberry Pi 4, mounted on board a crawler robot. A 64-transducer 40-kHz array configuration is selected based on uniformity of imaging amplitude over the circumference of the pipe wall. Testing revealed joints between pipe sections could be imaged at high amplitude, and that angular displacement between sections produced a different response to a properly aligned joint, potentially enabling detection of faulty joints. The surface roughness of some pipes also provides enough backscatter to be imaged, which is useful for detecting regions of corrosion. It was also found that reflections from the pipe wall in the plane of the array allow imaging of the wall shape. This can indicate the presence of junctions, as well as detect ovality to within 1%. These in-plane wall reflections were also found to be a source of low-amplitude coherent noise throughout the imaging domain, which is of similar amplitude to small (< 10 mm) through-holes in the pipe wall.

An analytical model for permeability of fractal tree-like branched networks composed of converging–diverging capillaries

Seepage processes in tree-fractal networks have attracted extensive research, but the results of most of these studies presuppose a constant pore cross section. This research investigates fluid flow in a fractal tree-like branching network composed of five different types of circular cross section pipes and establishes the effective permeability of the network. Furthermore, the effective permeability of the fractal tree-like network is compared with that of a typical parallel channel network, and the effect of structural parameters on the seepage process of the tree-like branching network is systematically investigated. The effective permeability of all pipelines increased sharply with an increase in the internal diameter ratio at first and then decreased. Furthermore, a considerable advantage was seen in the permeability of the fractal tree network over the traditional parallel channel network, with the benefit becoming more noticeable as branching levels increased. The clear physics of the model offers a useful framework for studying seepage processes.

Evaluation of arched EPS block and geocell inclusions in trench backfill for protection of buried flexible pipes

This paper presents an experimental investigation examining the novel idea of employing curved expanded-Polystyrene (EPS) blocks that arch around the upper section of buried flexible pipes to reduce the pressures acting on them and hence resulting deformation/deflections. Large-scale testing was performed to examine key performance indicators for reinstated trenches with buried 250-mm diameter plastic pipe (0.75-m invert depth) when subjected to cyclic surface loading simulating vehicular traffic. The real-scale model tests investigated unreinforced and geocell-reinforced trenches with conventional rectangular and differently shaped EPS block inclusions placed above the crown or fitting snugly around the upper section of the buried pipes. Compared to conventional rectangular EPS block, the curved-arched EPS block produced greater reductions in the pressures acting on the buried pipes, resulting in substantially smaller pipe deformation/deflections. The geocell layer overlying the EPS block significantly reduced the pressures bearing on the highly compressible EPS material, thereby reducing its compression and the trench surface settlement. Optimum trench reinstatements incorporated both the geocell layer and a 75-mm thick curved-arched EPS block fitted around the top section of the pipe. Doubling the EPS block thickness produced only modest reductions in the pipe deflections, but significantly increased the trench surface settlement.

Application of the interval approach to determine the exploitation time of pipelines

The fundamental problem from the point of view of pipeline exploitation in KGHM Polska Miedz S.A. is the very high overwearing of the pipes used for the transport of tailings, as well as determining the time of trouble-free operation of pipe system components. Failures involve significant financial outlays, severe restrictions on operation and in some cases even stopping operation. For this reason, it is vital to monitor the condition of the transport systems, as well as to determine the permissible service life of the pipe sections, after which segments at risk should be replaced or turned over in order to extend their further operation. This paper focuses on the application of interval numbers to assess the durability of piping systems. The calculations were made using classical interval numbers by using code written in INTLAB libraries. The correctness of the solutions obtained was verified using the Monte Carlo method, assuming a uniform distribution of random variables.

ANALYTICAL SOLUTION OF THE DIFFERENTIAL EQUATION OF HEAT CONDUCTIVITY FOR DAMAGED THERMAL INSULATION OF PIPELINES

For heat supply systems of Ukraine, the determination and forecasting of thermal energy losses during the transportation of heat carrier is an urgent problem. The thermal lines of the heating networks are long and its insulation is damaged. Installation of heat energy metering devices at all sources and all consumers (i.e. buildings) without exception allows determining and forecasting real heat losses in the heat network, but this is a difficult task, not all consumers and sources are actually covered by heat consumption accounting. The task of determining heat losses is also relevant for energy management systems of heat supply systems, energy companies and industry. The solution to the problem is proposed by a separate mathematical modeling of the temperature state of the section of the damaged insulating layer with the determination of the heat flow through it. It is proposed to solve the problem by the method of analytical solution of the differential equation of heat conduction with boundary conditions of the third kind. With the uniform distribution of characteristic damages along the total length of the pipeline, knowing the limits of damage influence, the share of insulation damage and the number of damages on the pipeline, it is possible to determine the real heat flow from the outer surface of the pipelines, including coefficient of increase of heat losses on the section of the heat pipe in relation to those determined by regulatory documents. Traditionally, one-dimensional models or determinations of the two-dimensional temperature field and actual heat fluxes in a cross-section to the axis of a characteristic damaged section of insulation are considered. But this does not take into account the two-dimensionality of the temperature field of the damaged layer of insulation along the length (that is, along the axis) of the pipeline. Therefore, the purpose of this work is to develop a methodology for determining heat losses through pipelines, taking into account the damage to their insulation and the distribution of characteristic damages along the length. The following simulation was carried out for one of the areas. Also, experimental and numerical studies using the finite difference method in combination with the method of running variable directions for similar models confirmed the coincidence of the analytical solution of the proposed model and the finite difference model within the permissible error.

Numerical simulation analysis of high-temperature bent sodium heat pipes

Abstract High-temperature bent heat pipes are safety-level heat transfer components used in heat pipe cooled reactor, and their applications are becoming increasingly widespread. In this study, a comprehensive three-dimensional numerical model was established to evaluate the effects of different bending angles and radii on the performance of high-temperature heat pipes. The model solved for the temperature, pressure, and velocity fields in the wall, wick, and evaporator, considers the compressibility effect of the vapor. The study investigated parameters such as vapor pressure, vapor velocity, radial secondary flow field, wall temperature, wick temperature, and equivalent thermal resistance of powder sintered core sodium heat pipes with bending angles of 45°, 90°, 135°, 180°, and a bending radius under 90°. The results showed that when sodium vapor enters the bent pipe, the vapor flow deviates towards the outer side, resulting in higher vapor pressure at the outer side than the vapor pressure at the inner side, and the generation of radial secondary vortex. This leads to higher temperature in the evaporator and adiabatic sections of the bent heat pipe, while lower temperature in the condenser. Fractal patterns are observed in the outer and inner wall temperature curve in the adiabatic section, with lower temperatures on the inner side and higher temperatures on the outer side. The bent heat pipe exhibits higher equivalent thermal resistance than that of a straight heat pipe, and the equivalent thermal resistance increases with increasing bending angle, and the equivalent thermal resistance decreases with increasing bending radius.

Measurement of two phase flow concentration with a novel pressure difference method. I: Principle

Traditionally, the measurement of the concentration of a two-phase flow by gauging differential pressure is subject to pressure loss due to the flow friction along the pipe wall. A novel pressure difference method against this issue was proposed in this paper. A theoretic model is developed for the method, from the principle of hydrostatics of particle gravitational settlement. The method was essentially validated with an experiment of particle settling in a stand-alone pipe section by sealing the two terminals to form a static gas-solid two phase medium and supported with a numerical simulation based on a Lagrangian model as well. Inherently, the method is expected to measure the concentration of a two phase flow in a pneumatic conveying pipe, correspondingly by setting a flow branch which contains an erect settlement tube with two dynamically shutting valves to form a transient static particle deposition segment.

Numerical simulation analysis of stable flow of hydrate slurry in gas-liquid-solid multiphase flow

The study of multiphase flow characteristics of hydrate slurry was crucial for controlling the risks associated with hydrate slurry transport in deep-water oil and gas operations. Currently, multiphase flow research on the hydrate slurry flow system focuses on two-phase (solid-liquid) flow studies in single short straight pipes or elbows. This paper established a geometric model based on an experimental loop of high-pressure natural gas hydrate slurry. The Euler model contained n momentum equations and continuity equations for each term, and the Euler model can couple the pressure term with the surface exchange coefficients. Therefore, Euler model was suitable to deal with complex fluid motion problems. Such as bubble flow problem, floating problem, particle suspension problem and fluidized bed problem. In this paper, the hydrate particles in the grout were set as regular round spheres and do not decompose, so the Euler model was suitable for the simulation of the gas-liquid-solid three-phase flow of hydrate grout in the loop. The Euler model was used to simulate the three-phase (gas-liquid-solid) expansion in the loop, focusing on the influence of hydrate slurry inlet flow rate, inlet hydrate volume fraction, liquid phase viscosity and pipe diameter on slurry flow characteristics. The results are as follows:1) Based on orthogonal experiments, pipe diameter has the most significant impact on the pressure drop of the entire pipe section, while liquid phase viscosity has the greatest impact on the average aggregation particle diameter of hydrate on the cross section.2) The distribution of hydrate phase is related to the direction of the loop. Under the influence of gravity, hydrates are primarily dispersed in the liquid phase, with a high concentration in the solid-liquid mixing zone, tend towards the gas phase zone. Hydrate particles are symmetrically distributed in the vertical cross-section, with smaller particle diameters in the solid-liquid mixing zone compared to the gas phase and liquid phase zone 3). In the elbow section, centrifugal force and density difference cause hydrate particles to aggregate towards the lower pipe wall on the outside of the elbow. This results in the disappearance of the liquid phase zone, higher hydrate concentration on the outside of the elbow, and smaller hydrate particle diameter in the solid-liquid mixing zone compared to the gas phase zone.4). Throughout entire loop, the viscosity of the slurry in the solid-liquid mixing zone was the highest, and the volume fraction of hydrate particles was symmetrical both vertically and horizontally. To validate the simulation results, high-pressure multiphase flow hydrate generation experiments were conducted in a 6 MPa hydrate slurry experimental loop. The stable flow pressure drop value of the slurry was compared to the simulation results. The relative error between the simulated and experimental pressure drops is less than 15%, falling within an acceptable range and matching the experimental results. This proved that the multiphase simulation technique of hydrate slurry gas-liquid-solid in the loop can effectively guide the safe transportation of hydrate slurry under actual working conditions.

Pipe to annular flow conversion: Numerical study

Large Eddy Simulation (LES) of turbulent flow at the entrance to an annular pipe section has been performed. The flow over a single circular rod, coaxially immersed in a circular pipe is considered. The Reynolds number, based on mean velocity and hydraulic diameter of the annular section, is ReDh=40530. The study aims to gain insights into the turbulence characteristics of the primary and secondary separation bubbles, developing on a side surface of the rod. Key findings include tiny toroidal vortices in the primary bubble's front, forming a vortex train with intermittently shed vortex structures. Large-scale helical stripes have been reproduced at the entrance to the annular section. Tilting of the axially-oriented streaks was observed close to the rod surface. It resulted in a slight anisotropy of the normal Reynolds stresses. The LES data could refine classic Reynolds-averaged Navier-Stokes-based turbulence models.

Güneş Kollektörlerinde Elips Kesitli Boru Kullanımının İncelenmesi

Güneş enerjisi sıcak su üretimi, ısı enerjisi üretimi, elektrik enerjisi gibi farklı alanlarda yaygın bir şekilde kullanılmaktadır. Güneş enerjisinden faydalanmak için kullanılan termal güneş kollektörleri enerji üretiminde oldukça önemli bir yer tutmaktadır. Sıcak su üreten güneş enerji sistemlerinde yüksek verim elde etmek için birçok yöntem bulunmaktadır. Bu çalışmada termal güneş kollektörlerinde verimi artırmak için güneş enerjili su ısıtma sistemlerinde farklı şekillere sahip akışkan borularının etkisi incelenmiştir. Bu amaçla soğurucu plakaya temas eden dairesel kesitli boru yerine elips kesitli boru kullanılarak soğurucu plakaya temas eden yüzey alanı arttırılmış ve artırılan temas yüzeyinin etkisi araştırılmıştır. Analizler ANSYS Fluent yazılımında yapılarak elips kesitli boruda su sıcaklığının dairesel kesitli boruya oranla daha yüksek olduğu görülmüştür. Elips şeklindeki borudaki suyun çıkış sıcaklığı 304,16 K iken dairesel kesitli boruda suyun çıkış sıcaklığı 296,082 K bulunmuştur. Elips boru kesitli güneş kollektörününde verim değerinin, dairesel boru kesitli güneş kollektöründen %8,078 daha yüksek olduğu bulunmuştur.

Research on the Characteristics of Flow Velocity of a Piped Car when Starting in a Straight Pipe Section under Different Loads

It is of great significance to explore the flow velocity characteristics of piped cars when they are started under different loads. In this paper, the flow velocity characteristics of the water flow around a piped car when it is started in the straight pipe section are studied through physical experiments. The masses of the piped cars are 1.5 kg, 1.9 kg, and 2.3 kg, respectively. The results show that, with the increase in the load of the pipeline car, the axial flow velocity in the front section increases, the absolute values of radial flow velocity and circumferential flow velocity increase, and the gradient of flow velocity increases. The positive radial flow velocity and negative circumferential flow velocity regions increase, and the distribution of positive and negative radial flow velocities and circumferential flow velocities is obvious. The gradients of axial, radial, and circumferential flow velocities in the annular section all increase, and the contour spacing becomes smaller and more densely distributed. The absolute values of the radial and circumferential flow velocities increase. The regional demarcation of axial flow velocity in the rear section is more obvious, and the average value of axial flow velocity in the high-flow-velocity area behind the vehicle increases. Additionally, the gradient of flow velocity increases. The absolute values of radial velocity and circumferential velocity increase, the gradient of velocity increases, and the velocity distribution is obviously regional. This study supplements and improves the theoretical study of a piped car when it is started and has certain reference value for the research and application of the hydraulic transport technology of the barrel-loading pipeline.

Performance of Grouted Splice Sleeve as A Connection for Wall Panels

A grouted sleeve is a mechanical coupler used to join steel bars. It can be used to join precast concrete walls. Most grouted sleeves are pricey proprietary products. This study investigated the behaviour of a grouted sleeve made of steel pipe sections. The grouted sleeve was used as a wall panel connection. The specimens were subjected to three types of loads: tensile, shear, and flexural. The performance of the specimens was evaluated based on the load-displacement responses. For satisfactory bond strength, a bar embedded length of 11 times the bar diameter was required. The grouted sleeve performed well in tension but poorly in shear load. The service shear load was just one-third of the total load capacity. Thus, the grouted sleeve was not recommended for resisting shear load without shear keys to strengthen the joint.

Research on Strain of Unequal Wall Thickness Pipeline of the X80 Pipeline under Lateral Load

X80 steel is a material with high strength and good toughness, which is widely used in long-distance natural gas pipelines. Pipelines will have different wall thicknesses, depending on the safety level requirements of different regions. Two sections of pipes with different wall thickness form unequal wall thickness of pipeline (UWTP) that is joined together by welding. UWTP pass through some geohazard areas, such as landslides. The frequency of landslides is extremely high in mountainous areas, which can seriously affect the safe operation of UWTP. In this paper, a model of a 12.8 mm wall pipe section and a 15.6 mm wall pipe section are linked by girth welds. The strain between the pipe section and the weld was quantitatively analyzed. The results show that the strain at the girth weld in the 3 o’clock direction of the pipe increases sharply. The strain in the 9 o’clock direction of the pipe is generally lower than the strain in the 3 o’clock direction. The strain value of the 12.8mm wall thickness pipe section is generally greater than the strain value of the 15.6mm wall thickness pipe section.

Numerical simulation of air flow and distribution in the blast system of blast furnace

A three-dimensional geometric model of the blast system of the 5500 m3 blast furnace was established in this study. The velocity distribution of the blast system was calculated by OpenFOAM, and the velocity distribution at cross sections of the round pipe and the branch pipe was analysed. The main conclusions are as follows: (1) When the hot air enters the branch pipe, the air flow speed gradually increases and reaches its maximum value (approximately 266.7 m/s) at the tuyere outlet. (2) When the hot air enters the round pipe from the main pipe, there is momentum loss. When the hot air further reaches the opposite side of the junction between the round pipe and the main (Tuyere 1#), the speed of the hot air in the round pipe decreases to the minimum. (3) The maximum air flow average speed of the tuyere outlet is located at Tuyeres 20# and 21# at the junction of the main pipe and the round pipe, which can reach 264.5 m/s. The minimum air flow average velocity of the tuyere outlet is located at Tuyeres 19# and 22#, approximately 258.5 m/s.

Performance analysis of flat plate heat pipe and heat pump heating device based on solar energy

To solve the problem of poor heating performance of air source heat pumps when the air temperature is relatively low, this paper proposes a flat heat pipe and heat pump heating device based on solar energy. The device can store solar energy and continuously replenish the heat pump. The performance of the device is studied through experiments and simulation calculations. The results show that the difference in temperature between the evaporating section and the condensing section of the flat heat pipe is about 1°C, which shows that the heat pipe has good thermal conductivity. The device can produce a temperature rise of 7~61°C for the air entering the heat pump, which can realize the purpose of heat replenishment for the heat pump. Under the premise of no heat supply, the device can continuously heat -5°C fresh air to 5°C within 3.6 hours through the storage of solar energy. It shows that the device has good heat storage capacity. The above research shows that the device can realize the function of continuous replenishment of air source heat pump by solar energy, and has certain practical application value.

Design and Experimentation of a Hydrokinetic Turbine for Electricity Generation in Closed Pipes

In the present research work, a device for electrical energy generation to be used in water pipelines has been designed, simulated, and tested. To achieve this, a study of the most influential parameters involved in the experiment has been carried out and both, the turbine model and the geometry of the experimental test pipe, have been selected through CFD simulations. Next, the Design of Experiments (DOE) has been used to obtain the configuration with a higher energy extraction from running water. Finally, the turbine and the test pipe section have been manufactured by 3D printing and the experimental tests have been carried out with the optimal configuration to validate the results obtained in the CFD simulations. To simulate the exchange of energy between the water and the turbine, the CFD software SIMULIA XFlow has been used.