bluuebunny/crossref_metadata_2025_split huggingface dataset:
Waste Heat Recovery for Offshore Applications
Authors: Pierobon Leonardo , Kandepu Rambabu , Haglind Fredrik 
Published: October 2013

With increasing incentives for reducing the CO2 emissions offshore, optimization of energy usage on offshore platforms has become a focus area. Most of offshore oil and gas platforms use gas turbines to support the electrical demand on the platform. It is common to operate a gas turbine mostly under part-load conditions most of the time in order to accommodate any short term peak loads. Gas turbines with flexibility with respect to fuel type, resulting in low turbine inlet and exhaust gas temperatures, are often employed. The typical gas turbine efficiency for an offshore application might vary in the range 20–30%. There are several technologies available for onshore gas turbines (and low/medium heat sources) to convert the waste heat into electricity. For offshore applications it is not economical and practical to have a steam bottoming cycle to increase the efficiency of electricity production, due to low gas turbine outlet temperature, space and weight restrictions and the need for make-up water.
A more promising option for use offshore is organic Rankine cycles (ORC). Moreover, several oil and gas platforms are equipped with waste heat recovery units to recover a part of the thermal energy in the gas turbine off-gas using heat exchangers, and the recovered thermal energy acts as heat source for some of the heat loads on the platform. The amount of the recovered thermal energy depends on the heat loads and thus the full potential of waste heat recovery units may not be utilized. In present paper, a review of the technologies available for waste heat recovery offshore is made. Further, the challenges of implementing these technologies on offshore platforms are discussed from a practical point of view. Performance estimations are made for a number of combined cycles consisting of a gas turbine typically used offshore and organic Rankine cycles employing different working fluids; an optimal media is then suggested based on efficiency, weight and space considerations. The paper concludes with suggestions for further research within the field of waste heat recovery for offshore applications.
An Experimental Investigation of Turbulent Flow in Concentric Annulus Using Particle Image Velocimetry Technique
Authors: Rodriguez Corredor Fabio Ernesto , Bizhani Majid , Ashrafuzzaman Mohammad , Kuru Ergun 
Published: October 2013

Fully developed turbulent flow in a concentric annulus is encountered in many engineering problems including food, chemical as well as oil industry applications. Because of nonlinear radial variation of total shear stress with the distance from the pipe wall, the analysis for the flow in annulus is more complex than in a round tube or parallel plate channel.
In this study, fully developed turbulent flow of water through a horizontal flow loop with concentric annular geometry (inner to outer pipe radius ratio = 0.4) was investigated. Reynolds number range varied from 17,700 to 66,900.
Velocity near the wall region was measured using high resolution particle image velocimetry (PIV) system. Axial mean velocity profile was found to be following the universal wall law (i.e., u+ = y+) close to the wall (for y+ < 10) and log law away from the wall (y+>10).
For all the cases investigated, radial positions of the maximum velocity and zero shear stress were very close to each other (± 0.5 mm). The difference between the both locations were found to be varying from 1.3 to 3.3% ( 2% on the average).
Sand Erosion in Multiphase Flow for Low-Liquid Loading and Annular Conditions
Authors: Vieira R. E. , Kesana N. R. , McLaury B. S. , Shirazi S. A. 
Published: October 2013

Low-liquid loading (LLL) and annular gas-liquid flow patterns are commonly encountered in gas transportation pipelines. They may also occur in other off-shore production facilities such as gas/condensate production systems. Experience gained from production of hydrocarbons has shown that severe degradation of production equipment will occur due to sand entrained in gas-dominant multiphase flows.
Sand erosion in multiphase flows is a complex phenomenon since several factors influence the particle impact velocity with the wall. In order to give a more comprehensive understanding of the particle erosion process in this particular scenario and to improve the current semi-mechanistic models, erosion and sand distribution measurements were conducted on 76.2 mm (3 inch) and 101.6 mm (4 inch) diameter pipes in a large scale multiphase flow loop with varying gas (air) and liquid (water) velocities generating low-liquid loading and annular conditions. Particle sizes used in the experiments were 150 and 300 microns with the latter being sharper than the former. Erosion measurements were made at sixteen different locations on a 76.2 mm (3 inch) standard elbow using ultrasonic technology, whereas Electrical Resistance (ER) probes were used for the measurements in a 101.6 mm (4 inch) diameter pipe. The experiments were primarily performed in the upward vertical orientation but a few measurements were performed in the horizontal orientation. Results suggest that the erosion is an order of magnitude higher when the pipe is oriented vertically compared to horizontal orientation. Also, the location of maximum erosion is identified for these flow patterns and it is not dependent on the pipe inclination.
A Novel Impact Damper Consisting of a Linear Chain of Particles
Authors: Gharib Mohamed , Ghani Saud 
Published: October 2013

Passive control is preferred due to its simplicity and low power consumption. A common passive control device is the Impact Damper which consists of a freely moving mass constrained by two stops inside a container mounted on the primary system. Researchers attempted to develop the impact damper for many decades. Their objective was to decrease the high accelerations, contact forces and noise levels.
In this paper, a novel type impact damper consisting of linear chain of different sizes spherical balls is introduced. The Linear Particle Chain (LPC) impact damper is based on dissipating the kinetic energy of the primary system by placing a small ball between each two large balls in the chain arrangement. The small ball will have numerous collisions with the larger balls when the primary system is excited. This behavior leads to dissipate part of the kinetic energy at each collision with the large balls.
The LPC impact damper is validated by comparing its responses with the single unit conventional impact damper. The free vibration of a single degree of freedom system equipped with the damper is studied. It has been shown that the LPC impact damper is more efficient than the conventional impact damper. A parametric study is conducted to investigate the effective number of balls and the efficient geometry of the impact damper to be used in a specific available space in the primary system.
Thermal-Mechanical Analysis of a Low-Enriched Uranium Foil Based Annular Target for the Production of Molybdenum-99
Authors: Govindarajan Srisharan G. , Solbrekken Gary L. , Allen Charlie W. 
Published: October 2013

One of the US Department of Energy’s Global Threat Reduction Initiative (GTRI) goals is the elimination of the use of high enriched uranium (HEU) for the production of the radioisotope molybdenum-99 (Mo-99). One strategy to achieve this goal is to use an irradiation target that utilizes a low-enriched uranium (LEU) foil. This paper considers an annular target geometry, where an LEU foil of open cross section is sandwiched between two concentric aluminum tubes. A recess is cut on the inner tube to hold the LEU foil and facilitate assembly. The target must contain the fission products until it can be opened and the LEU foil removed for further processing. The thermal contact resistance between the LEU foil and the aluminum tube cladding needs to be low enough to ensure that the LEU temperature does not exceed the operating temperature specified by the reactor safety case.
Numerical models using the commercial finite element code Abaqus FEA are used to explore the potential for gaps opening between the LEU-foil and the aluminum tubes, and the stresses developed in the aluminum tubes during heat generation in the target during irradiation. Parametric studies are conducted using constructed analytic models to explore the impact of the ratio of heat transfer coefficients between the inner and the outer tubes and the inner-to-outer tube thickness ratio. It is concluded that the current annular target design is safe at high LEU heat generation rates and the use of these targets will likely not compromise the reactor safety.
CFD Simulation and Optimization of the Center-to-Ends Oxidation Furnace Airflow Distributor Geometry to Investigate Uniform Airflow
Authors: Heidari Amir , Montazerinejad Sara , Badrnejad Ramin 
Published: October 2013

In this paper different rectangular and trapezoidal ducts have been simulated to optimize airflow uniformity inside the oxidation furnace by computational fluid dynamics (CFD) technique. The optimizations have been done in different duct geometries to satisfy homogenous air flow pattern over the whole process room. Results have shown that airflow uniformity is the main factor for the best quality of the produced fiber during oxidation. Oxidation process is primarily an exothermic reaction, so consistent and uniform airflow is essential to successfully remove heat of oxidation from each filament across the web to obtain quality product.
In our study, the oven geometry is very simple and consists of multi zones and provides a homogenous airflow parallel to the fiber hand. It is noticeable that airflow turbulence is minimized to prevent cosmetic damage to fiber tows. Results demonstrate our optimized air-distributor designs provide the requested uniform airflow and eliminate non ventilated dead zones between the boxes.
Application of Tornado-Flow Fundamental Hydrodynamic Theory to the Study of Blood Flow in the Heart and Main Vessels: Design of New Implantable and Accessory Devices for Cardiovascular Surgery
Authors: Bockeria Leo A. , Kiknadze Gennady I. , Agafonov Andrei V. , Gachechiladze Ivan A. , Gorodkov Alexander Y. 
Published: October 2013

The study of the hydrodynamic structure of Tornado-like swirling viscous flows has proved that these flows possess a strictly organized laminar structure which can be exhaustively described using the exact solution of nonstationary Navier-Stocks and Continuity equations [6]. The flows of this type belong to the class of quasi-potential self-organizing swirling flows that serve the restoration of equilibrium in nature. These flows are characterized by a high efficiency of medium transportation while the energy losses are minimized. This is manifested in a significant decrease of hydrodynamic resistance and special organization of the boundary layer. Recent studies performed in Bakulev Research Center for Cardiovascular Surgery (Moscow, RF) have proved that the structure of blood flow corresponds to the class of Tornado-like swirling flows. This allows modeling the optimum geometry of the surgically reconstructed flow channel of the heart and major arteries in order to exclude excessive flow disturbances. Most currently used substituting implantable devices contacting with the blood do not take into account the peculiar hydrodynamic properties of blood flow in the heart and great vessels. This leads to the formation of undesirable disturbance of the hydrodynamic flow structure, i.e. stagnant or separation zones, which can create conditions for thrombus formation and hyperplasia. Therefore, the exact solution can serve as a basis for the design of implantable devices contacting with blood flow without significant distortion of its structure. The following devices have been proposed.
- The aortic valve prosthesis, whose flowing surface has a convergent circular cross-section in the open position. Use of this prosthesis should provide significant reduction in the intensity of anticoagulant therapy after implantation.
- Blood vessel prosthesis with radial elasticity and convergent shape in accordance with the replaced section of artery.
- Circulatory assist device, whose working chamber contains directing profile on the inner surface corresponding to the Tornado-like flow streamlines.
- Hydrodynamic bench for physical modeling of the Tornado-like flow with specified characteristics, allowing testing of implantable devices contacting with blood flow under physiological conditions. The implantable devices for cardiovascular surgery designed on the basis of exact solutions of nonstationary hydrodynamics equations for the Tornado-like swirling flows will be more effective and safe, will reduce the rehabilitation time, and improve the quality of life of patients after surgery.
Lead From Behind: Enabling Partnerships to Bring Clean Water to Caliche, Honduras
Authors: Doudican Brad , Elbin Wyatt , Huelskamp Bethany 
Published: October 2013

The common model for engineers’ engagement in philanthropic development work is to find a community with a technical need, design the solution, raise funds for the solution, construct the solution, and hand the solution over to the community. While this approach has yielded many completed projects around the world, there are limits to the efficacy, sustainability, and long-term enabling potential to this approach. The Dayton Service Engineering Collaborative, or DSEC, takes an alternative approach to philanthropic community development which is demonstrated via a case study in bringing clean water for drinking and agricultural purposes to Caliche, Honduras.
Caliche, an impoverished village of approximately 350 people located in central Honduras, had access to a mountain spring as a source of water until a 2009 earthquake sent the spring’s flow underground. As of late 2011, the village did not have a clean source of drinking water, utilizing collected rainwater and surface water ponds for all of their water needs. Waterborne illness and malady was prevalent, with severe consequences to the young and the elderly. After a survey of the geography, the resources of the local people, and partner institutions, a community-scale biosand filtration system with requisite delivery structures was proposed, accepted, and brought to design fruition.
Design and implementation of a solution to the technical problem of water delivery and treatment, while rigorous and complex, is not out of the realm of practice for technical groups working in communities such as Caliche. The innovation in this project, however, was the “lead from behind” approach in the context of a best practice called asset-based community development. A multi-partner initiative led first and foremost by the community leadership, and through local institutions and power structures, was managed from distance. In addition to DSEC, partners in this project included a multi-national non-governmental organization (NGO), a financial investor, the Honduran government, several missionaries, the Caliche Water Council, a local landowner, the Caliche leadership known as the Patronado, and the local church. DSEC provided technical leadership and project oversight, ensuring that not only were the technical obstacles overcome, but that the community and local authorities were empowered to tackle future development projects with independent vision. It is through this enabling approach that impact beyond the immediate project is attained, and where DSEC believes the leadership potential of the engineer is fully realized.
Introduction of Mass Points Into the Finite Element Method for the Dynamic Behavior Modeling of Rotating Machine
Authors: Dougdag Mourad , Ouali Mohammed 
Published: October 2013

The dynamic modeling of the rotating machines system is required to understand their dynamic behavior and the associated vibration problems. Fortunately, this modeling has seen a great development, since the use of Timoshenko or Euler-Bernoulli beam, followed by the Jeffcott and Laval rotor until using fine and complex techniques these days.
Unfortunately, this development remains still insufficient to describe in a realistic way the dynamic behavior, in particular the rotor.
Nowadays, the using of the finite element method, which is considered as the powerful numerical tool, gave a great help. This method can model as real as possible the phenomena that influence the rotor behavior, but this tool remains inapplicable to describe its behavior when it undergoes at the same time motion, deformations and the faults effects.
To resolve these problems, a number of mathematical artifices are used, but, these methods are some times very difficult or are too complex and the result obtained is not always as good as it hopes. In fact, the deformed rotor resolution method is reduced to a modal solution, which does not show the real deformations during time in many cases.
In order to simplify the resolution and to show rotor movement with deformation under faults effects, a method is proposed to allow a better approach of this problem. This method is based on subdividing the structure to mass-point sections that make possible to consider the rotational motion with deformations of the rotors.
In this work, the above method is implemented on engineering simulation software dedicated for rotordynamics, and the calculation results are validated against experimental data of fault simulations in rotors as presented in the following sections of this paper.
Hydrogen Airships: A Necessary Return Because of High Costs of Helium
Authors: Dumas Antonio , Trancossi Michele , Madonia Mauro 
Published: October 2013

Many airship projects have been presented during last years. Most of them are slowed in their realization because of very high costs of Helium.
This paper presents an economic and energetic comparison between Helium filled airships and Hydrogen filled ones under the hypothesis of buying 20 MPa compressed Helium and local production of photovoltaic hydrogen by electrolysis.
The economic evaluation comprises the costs of PV plant for hydrogen production and docking and distribution systems for both gasses.
Analysis of uncertainty has been performed to evaluate economic parameters and payback time of the investments.
Comparison of Numerical and Experimental Results of Small Scale Compressed Gas Blast Experiments Involving a Surrogate Head Form
Authors: Grimm Matthew V. , Muci-Küchler Karim H. , Hinz Brandon J. , Walsh Shawn M. 
Published: October 2013

Exposure to a shock wave from an explosive blast can result in injury to the human body even if external signs of trauma are not present. Gaining a better understanding of the mechanisms contributing to those injuries can result in the design of better personal protective equipment (PPE). Compressed gas blast experiments can be conveniently used to explore the mechanical response of PPE systems and instrumented surrogate head forms to blast loading scenarios in a laboratory environment. Likewise, numerical simulations can be used to study relevant field variables related to the compressed gas blast and its effects on the target. In this regard, experimental data is needed to validate simulation results.
This paper presents an experiment that uses a small scale compressed gas blast generator to explore the pressure distribution around a surrogate head form due to blast loading. The compressed gas blast generator is an open-end shock tube which creates a shock wave when the diaphragm that separates the high pressure and low pressure (ambient air) regions ruptures. The overpressures on selected locations of the surrogate head form were measured with piezoelectric pressure sensors and the data was processed to obtain positive phase durations and positive phase impulses. The surrogate head form was positioned off-axis from the exit of the compressed gas blast generator to preclude the discharge flow from affecting the overpressure measurements. A three-dimensional Coupled Eulerian-Lagrangian (CEL) model of the experiment described above was prepared in Abaqus/Explicit. Selected numerical and experimental results were compared and there was good agreement between them.
Numerical Simulation of Steady and Unsteady Compressible Multiphase Flows
Authors: Li Huiying , Vasquez Sergio A. 
Published: October 2013

The present work concerns the development of an advanced numerical approach to simulate steady and unsteady compressible multiphase flows in the CFD solver FLUENT. Compressible multiphase flows can be simulated under the framework of either the multiphase Mixture/VOF or the Eulerian multifluid model. The governing equations solved are the mixture (Mixture or VOF model) or phase (Eulerian multifluid model) momentum, energy, species transport equations and phase volume fraction equations. Turbulence effects are accounted for using a range of multiphase turbulence models. For the compressible multiphase model, it assumes that only one phase is a compressible gas/gaseous mixture with multiple species. In gas-liquid flows, all the liquid phases can be compressible /incompressible liquid, while in gas-solid flows the solid phase can be treated as a granular flow. To ensure numerical stability and obtain physical solutions, the absolute pressure is limited in a way to satisfy the constraints for both incompressible and compressible flows that may exist in different regions. The compressible effects are taken into account by adding extra terms related to sound speed and phase volume fractions in both the phase volume fraction and the pressure-correction equations. For flow conditions at inlets and exits, only pressure and mass-flow-rate boundaries are applicable. The mixture Mach numbers are defined and used to determine the subsonic or supersonic flows and thermal boundary conditions.
The compressible multiphase model have been successfully used to simulate steady and unsteady, sub- and super-sonic compressible multiphase flows in a wide range of 2D and 3D multiphase systems. The examples presented in the paper include: (1). Gas-liquid separation in a vertical cylindrical container; (2). Transient pressure variations in compressible liquid and gas-liquid flows of water hammers; (3). Sub- and super-sonic gas-liquid two-phase flows in a nozzle; (4). Cavitating and ventilated super-cavitating flows; and (5). 3D gas-liquid flows in a three-stream injector. The solver robustness and convergence performance will be discussed. The solutions will be compared with available experimental data or numerical solutions. Emphasis will be focused on the solver performances on simulations of compressible multiphase flows. Overall, the results obtained from the present compressible multiphase model are in line with analytical/CFD solutions or available experimental data. The numerical approach is reasonably fast and robust, and suitable for practical compressible multiphase applications.