Outer Pipe Wall Research Articles

Detection of Two-Phase Slug Flow Film Thickness by Ultrasonic Reflection

Slug flow is a common phenomenon in closed pipes, occurring in two-phase flow where liquid and gas phases mix, impacting the custody transfer or the efficiency of chemical reactions. This study aims to detect and analyze slug flow film thickness in two-phase flow, providing detailed structural flow information. The ultrasonic or Doppler reflection method is employed to identify slug flow and detect detailed thickness. Additionally, electrical resistance tomography (ERT) is used to image and confirm the presence of slug flow. A high-speed camera records the slug flow's shape in real time, validating its existence. The ultrasonic reflection method offers high accuracy, with a measurement error rate of less than 1% based on experimental results. The study uses a homogeneous block calibration method to measure slug flow thickness. Graphical results reveal clear differences between the slug flow regime, inner pipe wall, and outer pipe wall, with the first echo of slug flow being easily observable. The accuracy of results is attributed to the combination of FPGA (Field-Programmable-Gate-Array) instruments and measurement methods, showcasing the study's novel approach. This research introduces a new perspective or novelty on slug flow in multiphase flow studies, highlighting an innovative method for detecting film thickness.

CFD analysis in effects of spacer-vane on thermal–hydraulic performance of two-phase flow in annular channel

Spacer performs a key function in the construction of nuclear rod assembly. It is utilized to ensure the appropriate spacing and firmness of the rods in assembly. In rod bundle structures, spacers are typically incorporated with vanes to promote turbulence and improve heat transfer. The aim of this work is to analyze the impacts of spacer-vane on the thermal–hydraulic performance of two-phase flow in an annular channel. CFD model of an upward flow annular channel with spacer-vane has been developed. In addition, an annular channel model with a spacer but without vane has been generated and modeled in order to examine the impact of the spacer-vane in a two-phase flow. Transient simulations were performed with flow considerations of mass flux 714.4 kg/m2s, liquid temperature 330 K, volume fraction 0.35, heat flux 197.2 kW/m2, and atmospheric pressure conditions. CFD results have been validated with experimental data. Results show that the core zone of the annulus gap exhibits the highest level of turbulent intensity, and the outer pipe wall temperature is lower for spacer-vane relative to spacer alone. It is observed that the majority of water vapor is concentrated at the center of the channel in the farthest downstream location.

CO2 Joule-Thomson effect: Application on premium connections for CCS well

CCS (Carbon Capture and Storage) is a major technology aiming to reduce greenhouse gases and reduce carbon footprint. In these applications, Oil Country Tubular Goods (OCTG) and associated premium connections are used to inject industrial CO2 into stable geological formations such as depleted oil and gas fields or saline aquifers, in liquid or dense phase to permanently store it. While current standards (API RP 5C5, ISO 13,679) allow qualification of premium connections for Oil & Gas application, no standard exists for CCS applications. In that frame, a new test methodology was developed to evaluate the impact of Joule-Thomson effect on premium connection, in the scenario of a CO2 blow-out and intermittent operation of the injection wells, such as shut-in of the subsurface safety valve (SSSV) or injection phase. To confirm that premium connections remain tight and safe after being exposed to a rapid depressurization of CO2, they have been physically tested in a horizontal load frame. The test consisted in the filling of the sample with CO2 up to a minimum of 100 bar and a temperature below 30 °C to ensure liquid state, or above 32 °C to ensure supercritical state inside the sample, and then depressurizing the sample through an orifice of 2 or 4 mm until complete drop of pressure. Minimum measured temperature on outer pipe wall reached around -50 °C before dry ice CO2 formation. Maximum measured gradient of temperature observed was around 70 °C. No leakage nor connection damages were observed during the pressure release sequences. Sealability was then confirmed during the internal pressure and external pressure test performed afterwards.

Numerical investigation of thermo-hydraulic performance in an annular heat exchanger with sinusoidal vortex generators

This study investigates thermal performance enhancement by utilizing vortex generators (VGs). VGs come in many designs, and this paper proposes optimizations for the sinusoidal vortex generator (SVG) when used in an annular conduit to improve heat transfer with minimal pressure drop. Two vital parameters of the SVG are analyzed, namely, blockage ratios (BRs) (0.1 and 0.2) and attack angles (α) (0–90°). The investigated fluid regime is turbulent, with the Reynolds number (Re) ranging from 5973 to 11,947. Three rows of SVGs are fitted on the surface of the inner pipe, where constant heat flux is applied, while the outer pipe wall is entirely insulated. The results indicate that the highest Nusselt number is enhanced by 20.4% over the smooth pipe when the case with BR = 0.2 and α = 90° is used at Re = 5973. However, the friction factor increases by 56.5% for the same case. Two types of transverse vortices are identified, where one type has its rotational axis normal to the inner pipe surface, and the other has its rotational axis parallel to the inner pipe surface. Those vortices with the axis perpendicular to the pipe surface merge with the fluid above the SVG to develop longitudinal vortices in different BRs and α. The case with BR = 0.2 and α = 15° yields the greatest average performance evaluation criterion (PEC) compared to other tested cases with a value of 1.054. This study finds that SVGs can contribute to a more efficient annular pipe-based heat transfer system.

Measurement Method for Fluid Pressure Fluctuation in Fluid-Conveying Pipe Using PVDF Piezoelectric Film Sensor

As a representative fluid-transporting system, fluid-conveying pipes play an essential role in many fields. For a fluid-conveying pipe system in operation, fluid pulsation in pipes contains much information about fluid flow parameters (flow velocity, fluid pressure, etc.). Therefore, the measurement of fluid pulsation is important for understanding the internal fluid flow. To use polyvinylidene fluoride (PVDF) piezoelectric film sensors to indirectly measure the pressure fluctuation of the internal fluid, we simulated a fluid-conveying pipe with PVDF piezoelectric film sensors attached to the outer pipe wall. The simulation results showed that the variation of voltage signal of PVDF, circumferential stress and strain of the pipe wall, and the pressure fluctuation of internal fluid were highly positively correlated, which proved that the PVDF piezoelectric film sensor can be applied to indirectly measure the pressure fluctuation of internal fluid. We also studied the influences of flow velocity pulsation and mechanical vibration caused by the pipeline pump during operation. It is found that the flow velocity pulsation had little influence on the measurements of the variation of circumferential stress and strain of the pipe wall and the internal fluid pressure fluctuation. When both ends of the pipe were fixed by hoops, mechanical vibration had little influence on the measurement of the variation of circumferential stress and strain of the pipe wall as well as the fluid pressure fluctuation. Finally, simulation results were verified by experiments.

Development and evaluation of miniature electrodes for electrochemical measurements in a CO2 top of line corrosion environment

ABSTRACTTop of line corrosion (TLC) is a degradation mechanism which establishes itself in ‘wet gas’ pipelines under significant temperature difference between the internal fluid and the outer pipe wall. Laboratory evaluation of TLC is based predominantly on the mass loss method which is an averaging approach. Hence, a real-time and spatially resolved corrosion response would add an extra dimension in terms of corrosion measurement. This work presents a new apparatus to explore the ability of a miniature three-electrode cell to provide instantaneous corrosion measurements in a TLC scenario. The electrochemical system is integrated into a buoyancy-driven flow TLC setup and is used to monitor instantaneous corrosion rates for X65 carbon steel over 20h through a combination of linear polarisation resistance, electrochemical impedance spectroscopy and Tafel measurements. The electrochemical responses are compared with gravimetric results under identical conditions and generating repeatable, accurate and instantaneous data to provide more insight into TLC mechanism.

Experimental study on pipeline internal corrosion based on a new kind of electrical resistance sensor

In this paper, a ring pair electrical resistance sensor (RPERS) has been developed for an internal-pipeline corrosion on-line monitoring system. The RPERS was divided into six segments along the circumference. The corrosion depth of each segment could be measured by using three alternating excitation currents injected into the sensor from different angles. In order to simulate and monitor the pipeline internal corrosion, a corrosion monitoring system which contained RPERS, wire electrical resistance sensor (WERS), thermocouples and a corrosion coupon was established. First, the corrosion processes in 3.5% sodium chloride solution with the temperature varied from 30°C to 60°C were studied. The temperature differences between the inner and outer pipe wall surfaces were measured by the top segment of RPERS. The test results revealed that the performance of RPERS is better than that of WERS in term of metal loss measurement. Then, carbon dioxide mixed with water vapour was pumped into the system with the temperature varied from 50°C to 80°C. In the scenarios, top of the line corrosion (TLC) occurred and was monitored by RPERS. The monitoring results demonstrated that the gas temperature and the temperature difference were important factors for TLC in sweet conditions.

Entry flow in curved pipes: turbulent boundary layer approach

ABSTRACTThe development of secondary boundary layer for a steady entry of fluid flow in a horizontal curved pipe is analysed using the turbulent boundary layer approach. Outside the boundary layer (within the central core), the inviscid fluid motion is treated by using the Euler and the continuity equations, whereas inside the boundary layer, the Pohlhausen method is applied, assuming a one-seventh power law of velocity for solving the integrals of the Navier–Stokes equations. The growth of the secondary boundary layer is slow with an increase in azimuthal angle, while it is gradual along the outer pipe-wall with an increase in radial angle and becomes abruptly faster near the separation point. The wall shear stress decreases with azimuthal angle, whereas it increases with radial angle attaining a peak and then decreases to zero at the separation point along the outer pipe-wall.

CFD study of an air–water flow inside helically coiled pipes

CFD is used to study an air–water mixture flowing inside helically coiled pipes, being at the moment considered for the Steam Generators (SGs) of different nuclear reactor projects of Generation III+ and Generation IV. The two-phase mixture is described through the Eulerian–Eulerian model and the adiabatic flow is simulated through the ANSYS FLUENT code. A twofold objective is pursued. On the one hand, obtaining an accurate estimation of physical quantities such as the frictional pressure drop and the void fraction. In this regard, CFD simulations can provide accurate predictions without being limited to a particular range of system parameters, which often constricts the application of empirical correlations. On the other hand, a better understanding of the role of the centrifugal force field and its effect on the two-phase flow field and the phase distributions is pursued.The effect of the centrifugal force field introduced by the geometry is characterized. Water is pushed by the centrifugal force towards the outer pipe wall, whereas air accumulates in the inner region of the pipe. The maximum of the mixture velocity is therefore shifted towards the inner pipe wall, as the air flows much faster than the water, having a considerably lower density. The flow field, as for the single-phase flow, is characterized by flow recirculation and vortices. Quantitatively, the simulation results are validated against the experimental data of Akagawa et al. (1971) for the void fraction and the frictional pressure drop. The relatively simple model of momentum interfacial transfer allows obtaining a very good agreement for the average void fraction and a satisfactory estimation of the frictional pressure drop and, at the same time, limits the computational cost of the simulations. Effects of changes in the diameter of the dispersed phase are described, as its value strongly affects the degree of interaction between the phases. In addition, a more precise treatment of the near wall region other than wall function results in a better definition of the liquid film at the wall, although an overestimation of the frictional pressure drop is obtained.

CFD investigations of particle segregation and dispersion mechanisms inside a polyolefin 8-leg loop reactor of industrial scale

The formation of polymer slugs inside loop reactors has long been a troubling issue for the polyolefin industry using slurry-phase process. The mechanism of solid phase segregation occurring in the slurry flow has been reported as one of the root causes of the formation of large polymer slugs. However, the mechanism of solid phase dispersion, which counters the solid phase segregation and retards slug formation, has not been fully understood yet especially from the aspect of fluid dynamics. Therefore, in this study we apply computational fluid dynamic (CFD) simulations to provide insightful details about these two competing mechanisms inside an 8-leg loop reactor of industrial scale. The simulations adopt the transient Eulerian–Eulerian two fluid model incorporated with the kinetic theory of granular flow to describe the slurry flow consisting of propylene in liquid state and solid polypropylene particles. The solid particles with an average diameter of 2.5 mm are found to segregate from the slurry mixture due to the centrifugal force induced by the bend geometry, forming thick particulate ropes close to the outer pipe wall. These particulate ropes are dispersed inside the vertical legs by the secondary flow, which exhibits the flow structure as a single vortex on the cross sections. The competition between the segregation and dispersion mechanisms results in numerous slurry clusters of varying solid contents. While they are circulated by the axial flow pump, the loop reactor shows fluctuating profiles of solid volume fractions and liquid velocity as well as the pump pressure output with respect to time. The simulation results reveal that the variations of pump pressure output, which is equivalent to the pump power consumption, are resultants from the varying frictions exerted by the slurry clusters. In addition, our simulation results suggest that operating loop reactors with small particle sizes can suppress the solid segregation mechanism as well as improve the uniformity of particle distributions, which consequently retards the formation of large slugs.

A211 励磁制御渦電流試験法による配管減肉検査のためのプローブ設計と評価(OS2 保全・設備診断技術(3))

Remote Field Eddy Current Testing (RFECT) can detect defects in a wider range of a specimen than conventional ECT, and is used for inspection of outer pipe wall thinning using inner coils. The aim of this study is to apply surface coil RFECT to pipe wall thinning and to propose the design of probe that can evaluate thinning with various size. Experiments and numerical analyses are performed on SUSS 16 austenitic stainless steel plates with slots. First, numerical analyses are verified through the comparison with experimental results. Then, the survey of probe parameters is performed, such as distance of between exciting and pick-up coils, and the test frequency. Capability of the optimized probe shows that surface coil RFECT can be used as a screening tool of inspection of pipe wall thinning.

Research on the Optimal Design of Soccer Robot Based on the Mechanical Analysis

Leakage causes of branch pipe of unit thermal networks were discussed based on macroscopic observation, chemical composition analysis, metallurgical microstructure inspection, mechanical property tests, SEM and EDS analysis. The experimental results showed that frequent contact of outer pipe wall with corrosion media and thermal fatigue load led to early crack of the pipe. During compression test, the crack propagated under increased compression stress and burst finally. Suggestions were provided to prevent similar events happening.

Outsourcing of Concrete Filled Steel Tube Strengthened CFST Axial Compression Short Columns Finite Element Analysis

A new composite strengthening method that the CFST short column was strengthened with concrete filled steel tube was presented. Through the finite element analysis of five specimens with strengthening circular concrete filled steel tube columns and a specimen without strengthening circular concrete filled steel tube to explore the impact of the outer layer of concrete strength grade, external pipe wall thickness for the ultimate bearing capacity of concrete filled steel tube columns. The results show that with the increase of the outer pipe wall thickness, double concrete filled steel tube column yield strength and ultimate strength have increased. As the outer concrete strength grade increased as the specimen bearing capacity increased. When the concrete strength grade greater than C40, the improvement of concrete strength for specimen ultimate bearing capacity is not great.

Numerical Analysis of Heat Transfer and Fluid Characteristics in Long Distance HTS Cable

Abstract Japanese national project, called “Materials & Power applications of Coated Conductors (M-PACC)”, started in FY2008. In this project, high temperature superconducting (HTS) cable using REBCO tapes has been developing. These HTS cables are expected as a compact size with large capacity and low loss power transmission. In the future, it is supposed that these cables will be installed in power grid for replacing existing power cables. Under the operating HTS cable in the power grid, it is necessary that the REBCO tapes in the long distance cable are kept cooling at low temperature stably and efficiently by liquid nitrogen (LN2). In this paper, the flow characteristic, such as pressure drop of LN2 flowing in the long distance HTS cable, and the heat transfer characteristic against heat generation, such as AC loss, and heat leak from cryostat-pipes were analytically estimated with varying the volumetric flow and the diameter of outer pipe wall which are parameters easy to control in cable system design. As a result, it was confirmed that the volumetric flow increasing is affective to extending the maximum distance which can be transmitted but it required increasing discharge pressure too. This increasing discharge pressure can be restricted without affecting the longitudinal distribution of the HTS temperature by expanding of the diameter of outer pipe wall.

Subsea Corrosion/Erosion Monitoring

Young Technology Showcase Detection and monitoring are important prognostic means in preserving material integrity and reducing the life cycle cost of industrial infrastructure, ships, aircraft, ground vehicles, pipelines, oil installations, etc. Having better control of your infrastructure’s condition will enable you to optimize profitability and lower maintenance cost. Hence, monitoring an oil and gas pipeline will not only work as a precaution, but can also give information on when replacement or repair is necessary, thereby maximizing uptime. There is a huge need for reliable monitoring of pipe wall thickness, both topside and subsea. Even in topside applications, the conditions of operation may be hostile and problems such as large temperature variations, lack of space, fluid loading issues, and a host of other factors make development of such a tool a challenging task. Going subsea makes it even more demanding when you have to take into account factors such as high pressure and limited access. Over the past years, ClampOn has offered a corrosion/erosion monitor (CEM) for topside installations. Major advantages of this technology are its noninvasiveness, high repeatability, lack of any transducer movement, and high coverage. The measurement principle is based on dispersion of ultrasonic-guided wave modes, and by using electromagnetism, these waves are transmitted along the pipe wall without the sensor being in direct contact with the metallic surface. This makes it an excellent candidate for subsea use. It is installed on the outer pipe wall to produce real-time wall thickness information, not as a spot measurement, but as a unique average path wall thickness. With several successful installations topside, the ClampOn CEM has also found applications subsea, with the first unit installed at 2300 m in the Gulf of Mexico in February and another 10 units to follow in the future. Corrosion and erosion in subsea installations is detected by several methods. In topside applications, the alternatives are both more reliable and many. In subsea applications, the more hostile environment makes the detection of corrosion and erosion a more challenging task. Piggable pipelines are normally inspected at regular intervals and tracking of pipeline integrity is in general not problematic. Some unpiggable pipelines can be inspected using cable-operated tools, but such inspections are expensive and may require a shutdown of production. Subsea production templates, flow jumpers, manifolds, and flow lines can today only be inspected by preinstallation of corrosion/erosion sensors or by use of sensors controlled by remotely operated vehicles (ROVs).

Ranking sections of main gas pipelines according to corrosion damage based on field polarization measurements

Free-corrosion potentials are measured and potentiodynamic and potentiostatic anodic polarization curves are recorded on an electrode made of pipe steel in soils close to different sections of the Urengoi-Surgut-Chelyabinsk main gas pipeline. The data obtained are compared to the type of corrosion destruction of the pipe, which was determined with the use of magnetic intrapipe defectoscopy. It is proposed to rank sections of main gas pipelines according to corrosion cracking damage of the outer pipe wall estimated by polarization measurements.

Non-intrusive corrosion-erosion monitoring for subsea applications

Detection and monitoring of corrosion and erosion are essential prognostic means in preserving material integrity and reducing the life-cycle cost of industrial infrastructure, ships, aircrafts, ground vehicles, pipelines, oil installations, etc. Even topside, the operating conditions can be extremely difficult, facing problems like pipe surface roughness, fluid loading, temperature variations, and a host of other factors that make development of a robust wall thickness assessment tool a challenging task. Deploying a monitoring system subsea makes the application even more demanding when factors such as high pressure and limited access must be taken into account. The ClampOn Corrosion-Erosion Monitor has already been successfully installed at several locations topside and is now in its final stages of the subsea development. Non-invasiveness, high repeatability and high coverage are among its advantages, making it an excellent candidate for subsea use. The technology is based on the dispersion of ultrasonic guided wave modes. By using electromagnetism these waves can be transmitted through the pipe wall without the sensor being in direct contact with the metallic surface. It is installed on the outer pipe wall to produce real-time wall thickness information, not as a spot measurement, but as a unique average path wall thickness.

Influence of Boiler Load Swing Rates on Effective Stresses of Drum Boiler Riser Tubes

In this paper, different rates of steam flow (swing rates) are used to demonstrate the transient changes in both the drum-boiler steam pressure and the wall temperature levels in addition to stresses in the walls of steam risers. A MATLAB code was written to integrate the nonlinear dynamic governing equations for solving the water volume, the drum pressure, and the steam quality at the exit of the riser tubes. The same code is also used for calculating the steam riser inner and outer wall temperatures based on the inner wall heat transfer coefficient. The temporal riser pipe pressure and the inner and outer pipe wall temperatures have been incorporated into an ANSYS model for calculating the effective combined thermal and pressure-caused stresses numerically. The combined effective stress fluctuation for the highest swing rate (40%) is found to be too low to induce any damage in the riser tube. The controlled pressure level has been compared with an actual pressure reading from an existing drum boiler under operating conditions for the purpose of validating the control parameters employed in the study. An optimization method for reducing the steam pressure overshoot level in the boiler is also proposed.

Laminar, transitional and turbulent annular flow of drag-reducing polymer solutions

Mean and rms axial velocity-profile data obtained using laser Doppler anemometry are presented together with pressure-drop data for the flow through a concentric annulus (radius ratio κ = 0.506) of a Newtonian (a glycerine–water mixture) and non-Newtonian fluids—a semi-rigid shear-thinning polymer (a xanthan gum) and a polymer known to exhibit a yield stress (carbopol). A wider range of Reynolds numbers for the transitional flow regime is observed for the more shear-thinning fluids. In marked contrast to the Newtonian fluid, the higher shear stress on the inner wall compared to the outer wall does not lead to earlier transition for the non-Newtonian fluids where more turbulent activity is observed in the outer wall region. The mean axial velocity profiles show a slight shift (∼5%) of the location of the maximum velocity towards the outer pipe wall within the transitional regime only for the Newtonian fluid.

The Cooling of PEFC with Pentane Boiling in Minichannels: A Study of Flow Instabilities Using Neutron Radiography Visualization

Polymer electrolyte fuel cells (PEFC) operate best at a steady temperature of about 80°C and have a very low heat flux compared to other heat transfer applications. Two-phase pentane cooling of bipolar plates is studied in order to optimize fuel cell cooling in transport applications. High-speed visualizations of boiling pentane in a circular steel tube (D i = 1.1 mm, D o = 2 mm) have been performed in a Neutrograph instrument at the Institut Laue-Langevin in Grenoble, France. The heat and mass flux were both very low and appropriate for cooling of PEFC. The spatial resolution of the images is approximately 0.15 mm and the maximum frequency is 154 Hz. In the images, the liquid-vapor differentiation is clearly visible. Time resolved measurements of the outer pipe wall temperature, synchronized with the images, show that at low mass flow rates, the pipe wall is high above the saturation temperature and the pipe filled with vapor and liquid slugs. At higher flow rates, the wall is superheated when filled with liquid, and at saturation temperature during boiling when exposed to a liquid-vapor mixture. An irregular switch between these two states was observed. The superheated wall is shown to be consistent with the superheated liquid in the pipe in both stable and time-dependent states. Unfortunately, the strong γ-radiation produced by the neutrons has a substantial effect on the onset of boiling, which is why comparisons with non-irradiated systems might be difficult. Simplified steady and time-dependent models are proposed to explain the measured wall temperature instabilities and superheat.