1,521 research outputs found

    Effect of flow pattern at pipe bends on corrosion behaviour of low carbon steek and its challenges

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    Recent design work regarding seawater flow lines has emphasized the need to identify, develop, and verify critical relationships between corrosion prediction and flow regime mechanisms at pipe bend. In practice this often reduces to an pragmatic interpretation of the effects of corrosion mechanisms at pipe bends. Most importantly the identification of positions or sites, within the internal surface contact areas where the maximum corrosion stimulus may be expected to occur, thereby allowing better understanding, mitigation, monitoring and corrosion control over the life cycle. Some case histories have been reviewed in this context, and the interaction between corrosion mechanisms and flow patterns closely determined, and in some cases correlated. Since the actual relationships are complex, it was determined that a risk based decision making process using selected ‘what’ if corrosion analyses linked to ‘what if’ flow assurance analyses was the best way forward. Using this in methodology, and pertinent field data exchange, it is postulated that significant improvements in corrosion prediction can be made. This paper outlines the approach used and shows how related corrosion modelling software data such as that available from corrosion models Norsok M5006, and Cassandra to parallel computational flow modelling in a targeted manner can generate very noteworthy results, and considerably more viable trends for corrosion control guidance. It is postulated that the normally associated lack of agreement between corrosion modelling and field experience, is more likely due to inadequate consideration of corrosion stimulating flow regime data, rather than limitations of the corrosion modelling. Applications of flow visualization studies as well as computations with the k-ε model of turbulence have identified flow features and regions where metal loss is a maximu

    Modelling brittle fracture propagation in gas and dense-phase CO2 transportation pipelines

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    The development and application of a fluid–structure interaction model for simulating the transition of a through-wall defect in pressurised dense (150 bar, 283.15 K) and gas phase (34 bar, 283.15 K) CO2 pipelines into a running brittle fracture is presented. Given the economic incentives, the fracture model is employed to test the suitability of the existing stock of natural gas pipelines with the relatively high ductile to brittle transition temperatures of 0 and −10 °C for transporting CO2 in the terms of their resistance to brittle fracture propagation. The hypothetical but nevertheless realistic scenarios simulated involve both buried and above ground 10 km long, 0.6 m i.d. pipelines. Based on the assumption of no blowout of the surrounding soil upon the formation of the initial leak, the results show that the transition of the leak into a running brittle fracture in buried CO2 pipelines is far more likely as compared to above ground pipelines. In addition, gas phase pipelines are more prone to undergoing a propagating brittle fracture as compared to dense phase pipelines despite the lower operating pressures of the former. Furthermore, counter-intuitively, isolation of the feed flow following the discovery of a leak is shown to facilitate brittle fracture failure. The initial defect geometry on the other hand is shown to have a profound impact on the pipeline's resistance to propagating brittle fractures

    The transmission line method for modelling laminar flow of liquid in pipelines

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    Investigation and Enhancement Using Different Types of Pipelines for the Servo Hydraulic System with PID Controller Tuned Using Fuzzy Logic

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    This paper aims to investigate the effect of using different types of pipelines with the servo hydraulic system enhanced with PID controllers tuned by fuzzy logic. The mathematical models of several types of pipelines with different specifications (i.e. area variations in the pipe, disturbance source, etc.) are developed. The effect of the modified pipelines on the position control system at spool displacement is tested,since the servo hydraulic systems are difficult to control due to nonlinearity and complexity of their mathematical models. A  PID controller tuned using fuzzy logic technique is used to improve the servo hydraulic system response.The results show that the mathematical models of the pipelines have a significant effect on the performance of the position control system at spool displacement according to the used pipeline type.Furthermore, a more desirable time response specifications and less steady state error are achieved after using the proposed controller

    Two-Phase Flow

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    An improved computational fluid dynamics (CFD) model for predicting hydrate deposition rate and wall shear stress in offshore gas-dominated pipeline.

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    Gas hydrates in pipelines is still a flow assurance problem in the oil and gas industry, and requires a proactive hydrate plugging risk predicting model. As an active area of research, this work has developed a 3D 10m length by 0.0204m diameter horizontal pipe CFD model based on the eulerian-eulerian multiphase modelling framework to predict hydrate deposition rate in a gas-dominated pipeline. The proposed model simulates the conditions for hydrate formation with user defined functions (UDFs) for both energy and mass sources implemented in ANSYS Fluent, a commercial CFD software. The empirical hydrate deposition rates predicted by this model at varying subcooling temperatures and gas velocities are consistent with experimental results within ±10% uncertainty bound. At lower gas velocity of 4.7m/s, the model overpredicted the hydrate deposition rates of the experimental results in Aman et al. (2016) by 9–25.7%, whereas the analytical model of Di Lorenzo et al. (2018) underpredicted the same experimental results by a range of 27–33%. Consequently, the CFD model can enhance proactive hydrate plugging risk predictions earlier than the analytical model, especially at low gas productivity. Similarly, at a velocity of 8.8m/s and subcooling temperatures of 2.5K, 7.1K and 8.0K, the CFD model underpredicted the hydrate deposition rates of the regressed experimental results in Di Lorenzo et al. (2014a) by 14%, 6% and 4% respectively, and overpredicted the results by 1% at a subcooling temperature of 4.3K. From the CFD model results, we also suggest that hydrate sloughing shear stress is relatively constant, and the wall shedding shear stress by hydrate vary during deposition. Finally, the CFD model also predicted the phase change during hydrate formation, agglomeration, and deposition

    Micro-encapsulated phase change material (MPCM) slurries: characterization and building applications

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    © 2017 Micro-encapsulated Phase Change Material (MPCM) slurries, acting as the heat transfer fluids or thermal storage mediums, have gained applications in various building thermal energy systems, significantly enhancing their energy efficiency and operational performance. This paper presents a review of research on MPCM slurries and their building applications. The research collects information on the currently available MPCM particles and shells, studies of the physical, structural and thermal stability, and rheological properties of MPCM slurries, and identification/determination of the critical parameters and dimensionless numbers relating to the MPCM slurries’ heat transfer. The research suggests possible approaches for enhancing the heat transfer between a MPCM slurry and its surroundings, while several controversial phenomena and potential causes were also investigated. Furthermore, the research presents mathematical correlations established between different thermal and physical parameters relating to the MPCM slurries, and introduces a number of practical applications of the MPCM slurries in building thermal energy systems. Based on such extensive review and analyses, the research will help in identifying the current status, potential problems in existence, and future directions in research, development and practical application of MPCM slurries. It will also promote the development and application of cost-effective and energy-efficient PCM materials and thus contribute to achieving the UK and international targets in energy saving and carbon emission reductions in the building sector and beyond

    Numerical Heat Transfer and Fluid Flow 2021

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    This reprint focuses on experiments, modellings, and simulations of heat transfer and fluid flow. Flowing media comprise single- or two-phase fluids that can be both compressible and incompressible. The reprint presents unique experiments and solutions to problems of scientific and industrial relevance in the transportation of natural resources, technical devices, industrial processes, etc. In the presented works, the formulated physical and mathematical models together with their boundary and initial conditions and numerical computation methods for constitutive equations lead to solutions for selected examples in engineering
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