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1
Lawther, Susan E. M. « The effects of fluid flow through faults in granite gneiss exhumed from seismogenic depths ». Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3374/.
Texte intégralRésumé :
Fault zones are ubiquitous structures throughout the Earth’s crust and as a fault evolves it can significantly influence the rheological and hydrological properties of the crust. Fluid flow through fault zones is typically associated with fault-fluid-rock interactions and these interactions can affect the mineralogy, strength and evolution of a fault zone. In this study, field mapping is combined with petro-physical and stable isotopic analyses of the fault rock to evaluate the fault-fluid-rock interactions that occur within different fault zones, and the effects of these reactions on fault zone and fault population evolution. At Passo Moro in the NW Itilian Alps, there are three sets of joints cross-cutting the granite gneiss and numerous faults have formed by reactivation of pre-existing joints. The distribution of faults at Passo Moro is ultimately controlled by the variability of joint density within the host rock and the pre-existing joint distribution also affects the likelihood of whether a fault will grow into a mature fault zone or not. Where the joint density is high, strain is unable to accumulate to significant levels to enable joint reactivation into faults, whereas where joint density is low, fault zones are isolated and thus there are no structures nearby to facilitate fault linkage. At Passo Moro the fault population has evolved in a similar way as that described by Martel (1990) whereby small faults link to form simple faults which connect to form compound fault zones. The Virgin Fault and Spaghetti Fault would be considered as small fault zones and The Ciao Ciao Fault is equivalent to a compound fault zone. All three fault zones have different fault architectures and the small faults have been affected by different fluid-rock reactions compared to the larger fault. The small faults have experienced fault zone strengthening by K-feldspar precipitation, whereas the large fault has been weakened by muscovite precipitation. The different reactions between the fault zones are primarily controlled by the water-rock ratio which in turn is governed by permeability and the volume of fluid that infiltrates the fault zone. The Virgin Fault is considered as a rock-dominated system (K-feldspar-rich) whereas The Ciao Ciao fault is a fluid-dominated system (muscovite-rich). However, stable isotopes from both fault zones record a low water-rock ratio signifying rock-dominated conditions. Therefore the mineralogy of the fault rock is not solely controlled by the permeability defined water-rock ratio. The fluid dominated conditions promoting muscovitization in the Ciao Ciao Fault were probably enabled by an open fluid system and large volumes of fluid flowing through the fault during its lifetime. Stable isotopes indicate that water-rock ratios got lower with time in the Virgin Fault implying a limited open system, whereas muscovitization and stable water-rock ratios in the Ciao Ciao Fault point towards open system behaviour. In the Ciao Ciao Fault quartz precipitation only occurs in the foliated cataclasite within the fault core. Quartz precipitation is typically associated with closed system behaviour and suggests that the foliated cataclasite periodically ceased to be open to fluids and hence experienced cycles of higher and lower permeability. Stable isotopes show that the Virgin Fault records mineral precipitation from a metamorphic-like fluid, but after fault deactivation, the fault periodically transmitted progressively more meteoric-like fluids via a micro-fracture network. The Ciao Ciao Fault records mineral precipitation from a more meteoric-like fluid compared to the Virgin Fault, and flow through micro-fracture networks is dominated by an essentially meteoric fluid. The Ciao Ciao Fault therefore does not preserve evidence of fluids from its early history. This study indicates that the geochemical reactions that occur within a fault are controlled in part by the evolutionary stage of the fault, the fault rock permeability and the volume of fluids that pass through the fault. These results have been used to propose models for how the hydraulic properties and strength of a fault (population) evolve with time. The models produced from this study help advance our understanding of the processes that occur during the timescale of the seismic cycle, and how a population of faults will evolve in terms of mineralogy, strength and fluid flow. Such information will be of use to those involved in mineralization and mining studies, the storage of nuclear waste in crystalline rock, and earthquake prediction studies.
2
Langenbruch, Cornelius [Verfasser]. « The Role of Stress Fluctuations in Seismogenic Processes : Fluid injection-induced earthquakes and scale invariance / Cornelius Langenbruch ». Berlin : Freie Universität Berlin, 2014. http://d-nb.info/1054637040/34.
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3
Tschaikowski, Max. « Fluid aggregations for Markovian process algebra ». Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-171109.
Texte intégralRésumé :
Quantitative analysis by means of discrete-state stochastic processes is hindered by the well-known phenomenon of state-space explosion, whereby the size of the state space may have an exponential growth with the number of objects in the model. When the stochastic process underlies a Markovian process algebra model, this problem may be alleviated by suitable notions of behavioural equivalence that induce lumping at the underlying continuous-time Markov chain, establishing an exact relation between a potentially much smaller aggregated chain and the original one. However, in the modelling of massively distributed computer systems, even aggregated chains may be still too large for efficient numerical analysis. Recently this problem has been addressed by fluid techniques, where the Markov chain is approximated by a system of ordinary differential equations (ODEs) whose size does not depend on the number of the objects in the model. The technique has been primarily applied in the case of massively replicated sequential processes with small local state space sizes. This thesis devises two different approaches that broaden the scope of applicability of efficient fluid approximations. Fluid lumpability applies in the case where objects are composites of simple objects, and aggregates the potentially massive, naively constructed ODE system into one whose size is independent from the number of composites in the model. Similarly to quasi and near lumpability, we introduce approximate fluid lumpability that covers ODE systems which can be aggregated after a small perturbation in the parameters. The technique of spatial aggregation, instead, applies to models whose objects perform a random walk on a two-dimensional lattice. Specifically, it is shown that the underlying ODE system, whose size is proportional to the number of the regions, converges to a system of partial differential equations of constant size as the number of regions goes to infinity. This allows for an efficient analysis of large-scale mobile models in continuous space like ad hoc networks and multi-agent systems.
4
Yerlett, T. K. « Enthalpies of fluids and fluid mixtures ». Thesis, University of Bristol, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355339.
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Idris, Muhammad Nuru. « Hydrodynamics and process modelling of fluid catalytic cracking reactors ». Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531527.
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Palabiyik, Ibrahim. « Investigation of fluid mechanical removal in the cleaning process ». Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4593/.
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The cleaning of pipework from fluids of high viscosity is a significant problem in many food and personal care industries which can cause considerable economic and environmental impact. Three stages are identified in the cleaning of straight pipes; (i) a short core removal stage of product recovery, before water breaks through the filled pipe, (ii) the 1st cleaning stage (film removal stage) when there is a continuous wavy annular film on the wall, and (iii) the 2nd cleaning stage (patch removal stage) in which the material is present as patches on the wall. The product recovery stage is found to influence the overall cleaning process. Conducting product recovery at low temperatures and high flow rates cause the formation of a wavy wall layer which leads to more rapid subsequent removal. A two step CIP protocol is proposed to decrease the environmental impact of cleaning of a viscoelastic material (toothpaste) from pipework. Applying cold water in the 1st cleaning stage and hot water in the 2nd cleaning stage results in 40 % energy saving without affecting the cleaning performance significantly compared to traditional CIP protocols used in plants. Yield stress of deposits is the key effect on the cleaning of deposits. A new dimensionless number is explored. It is physically a ratio of flow energy to the yield stress of a deposit. It has collapsed cleaning time data onto a one curve for different deposits cleaned at different velocities. It can be used to predict cleaning times of deposits or identify the governing cleaning mechanisms in cleaning. It is found that the magnitude of pressure loss in flow can be used to quantify the flow and turbulence effect on cleaning and scale up lab scale data. The results show that although fluid mechanical removal is a complex process, cleaning time of deposits can be predicted by knowing its rheology and fluid mechanical parameters of cleaning fluid.
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Bhattacharya, Sourin. « Fluid Mechanics of Micro Cold Spray Direct Write Process ». Diss., North Dakota State University, 2012. https://hdl.handle.net/10365/26552.
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Cold spray, also known as the gas dynamic spray process, was first discovered in the 1980s while doing high speed two phase wind tunnel experiments. The principle underlying this process is that if a metal particle is accelerated to a velocity above a certain critical velocity, upon impact on a substrate the particle and substrate will undergo rapid plastic deformation and form a ?splat?. This process is currently being used for coatings applications. In this process, metal particles of diameter 5 ?m to 50 ?m are accelerated to a very high velocity (>500 m/s) and are deposited on substrates. Based on principles similar to cold spray process, we have developed a novel direct write process known as the Micro Cold Spray Direct Write (MCS-DW) process. Initial results from our experimental study have shown that conductive patterns of copper, tin and aluminum can be printed on flexible and rigid substrates using this process. The smallest feature size that can be printed using this process is 50 ?m.
In order to improve the deposition efficiency of the MCS-DW process, numerical studies were carried out to simulate the flow of aerosol particles through different nozzle geometries. It was found that a convergent capillary nozzle with a linear converging section of length 19 mm and a straight capillary of length 14 mm can be used to accelerate and focus silver particles of diameter 2 ?m. Copper particles of diameter 3 ?m can accelerate to their critical velocity by using a longer straight section of length 30 mm.
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Broggio, Jorge A. (Jorge Antonio) 1975. « Fluid damping with elastic medium in 3-D printing process ». Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9569.
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Moses, Brooks. « Simulation of multiphase fluid flows using a spatial filtering process / ». May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Tao, Zhengsu. « Characteristics of the transparent fluid assisted in-process measurement method / ». View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?MECH%202003%20TAO.
Texte intégralRésumé :
Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 106-114). Also available in electronic version. Access restricted to campus users.
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Alseamr, Nisreen. « A Theoretical Simulation of the Settling of Proppants in a Hydraulic Fracturing Process ». VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4272.
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Hydraulic fracturing is a process for the extraction of hydrocarbons from underground formations. It involves pumping a specialized fluid into the wellbore under high pressures to form and support fractures in the rock. Fracturing stimulates the well to increase the production of oil and the natural gas which are the pillars of the energy economy. Key to this process is the use of proppants, which are solid materials used to keep the fractures open. Understanding the transport of proppant particles through a fluid is important to improve the efficiency and reduce environmental impact of fracturing. An increase of the settling velocity for instance, will impede the hydraulic fracturing process by reducing well productivity, or necessitate use of chemical additives. This thesis presents a theoretical investigation of the settling velocity of proppant particles. The effect of different parameters on the settling velocity were studied by manipulating the main factors that can influence particle transport. These include size of the particle (300 μm- 2000 μm), sphericity, density (1200 kg/m3-3500 kg/m3) and concentration. These typical values were obtained from commercially available proppants currently used in industry. Various correlations were investigated, assuming the carrier (fracturing) fluid to be an ideal Newtonian and as a power law (non-Newtonian) fluid. This will help predict the settling velocity for proppant particles in order to increase well productivity, and improve hydraulic fracturing efficiency. The models show that changing the carrier fluid viscosity and particle properties such as diameter, density, sphericity, and concentration leads to a significant change in the proppant settling velocity. For instance, reduction in particle size, density, and sphericity tend to reduce the settling velocity, while increasing the concentration of the particles and the fluid viscosity reduce the settling velocity.
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Tschaikowski, Max [Verfasser], et Mirco [Akademischer Betreuer] Tribastone. « Fluid aggregations for Markovian process algebra / Max Tschaikowski. Betreuer : Mirco Tribastone ». München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1053618638/34.
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Heino, Perttu M. « Fluid property reasoning in knowledge-based hazard identification ». Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/32041.
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The study of serious accidents, which have occurred in the chemical process industry in recent times, highlights the need to understand fluid property related phenomena and the interactions between chemicals under abnormal process conditions or with abnormal fluid compositions. Consideration of these issues should be common practice in professional safety analysis work, and computer programs designed to support this work have to be able to deal with them.
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Ichinose, Matthew Hiroki. « Fluid Agitation Studies for Drug Product Containers using Computational Fluid Dynamics ». DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1980.
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At Amgen, the Automated Vision Inspection (AVI) systems capture the movement of unwanted particles in Amgen's drug product containers. For quality inspection, the AVI system must detect these undesired particles using a high speed spin-stop agitation process. To better understand the fluid movements to swirl the particles away from the walls, Computational Fluid Dynamics (CFD) is used to analyze the nature of the two phase flow of air and a liquid solution.
Several 2-D and 3-D models were developed using Fluent to create simulations of Amgen's drug product containers for a 1 mL syringe, 2.25 mL syringe, and a 5 mL cartridge. Fluid motion and potential bubble formations were studied within the liquid/gas domain inside the container by varying parameters such as viscosity, angular velocity, and surface tension. Experiments were conducted using Amgen's own equipment to capture the images of the spin-stop process and validate the models created in Fluent. Observations were made to see the effects of bubble formation or splashing during spin-down to rest.
The numerical and experimental results showed favorable comparison when measuring the meniscus height or the surface profile between the air and liquid. Also, at high angular velocity and dynamic viscosity, the container experiences instabilities and bubble formations. These studies indicate that CFD can be used as an useful and important tool to study fluid movement during agitation and observe any undesirable results for quality inspection.
15
Ruiz, Orlando E. « Numerical analysis of the dropwise evaporation process ». Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/18879.
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Cloete, Schalk Willem Petrus. « A mathematical modelling study of fluid flow and mixing in gas stirred ladles ». Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/1699.
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Thesis (MScEng (Process Engineering))--Stellenbosch University, 2008.A full scale, three dimensional, transient, mathematical model was developed to simulate fluid flow and mixing in gas stirred ladles. The volume of fluid (VOF) and discrete phase (DPM) models were used in combination to account for multiphase aspects, and a slightly modified version of the standard - model was employed for turbulence modelling. The model was validated to compare well against published physical modelling results. Model results were interpreted from the fundamental grounds of kinetic energy transport within the ladle. This approach led to the specification of three key measures of mixing efficiency: The rate and efficiency of kinetic energy transfer from the buoyant gas to the bulk steel as well as the total kinetic energy holding capacity of the ladle. These measures describe the quantity of mixing in any specific ladle setup, whereas the traditional measure of mixing time reflects mixing quality, i.e. the degree of kinetic energy distribution through the entire ladle. The model was implemented in designed experiments to assess various operating and design variables pertaining to mixing quantity and quality. Considerable time was invested in finding the correct balance between numerical accuracy and computational time so that the model could be used to generate the required data within the given time frame. Experiments on the operating variables drew an important distinction between factors influencing the shape and the strength of gas induced flow patterns. Flow pattern strengthening variables, such as gas purge rate, significantly affected the quantity of mixing, but had a limited effect on mixing quality. Variables such as mass loading that influence the shape of the flow patterns had much larger potential to influence both the quantity and quality of mixing. Minimization of turbulence losses in the region of the plume eye was identified as the primary outcome of ladle design. It was shown that a taller vessel allowed more distance over which the plume could disperse, thereby reducing velocity gradients and subsequent turbulence generation at the free surface. Multiple tuyere systems yielded similar improvements by dividing the gas flow into several weakened plumes. Surface wave formation was investigated as an added mixing mechanism and demonstrated to be impractical for application in full scale gas stirred ladles. The conditions for resonance between the surface wave and the bubble plume were met only in vessels with a very low aspect ratio. Performance improvements offered by swirl in these ladles could easily be replicated in more practical ways. This study demonstrated the potential of mathematical modelling as a tool for in-depth investigation into fluid flow and mixing in the hostile environment of a full scale gas stirred ladle. Scaled-down cold models are the only alternative and can offer no more than a reasonably reliable predictive framework. The ease of flow data extraction from the numerical model also proved invaluable in facilitating a fundamental understanding of the effects of various important independent variables on ladle hydrodynamics. At this stage of development, however, the model is recommended for use on a comparative basis only. Two important developments are required for complete quantitative agreement: The inclusion of turbulence modulation by the bubbles and the increased turbulence kinetic energy dissipation rate in the vicinity of the free surface. A general strategy was developed to account for these effects and it compared favourably with published cold model results. Further research is required to generalize this approach for application in full scale gas stirred ladles.
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Schmidt, Eric Andrew. « Characterizaton of a fiber suspesion jet in a co-flow dilution process ». Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/7090.
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Ivchenko, Alexander. « Incorporation of OpenFOAM software into Computational Fluid Dynamics process in Volvo Technology ». Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-16356.
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In this thesis work the feasibility of using open source OpenFOAM software as a solver part for Computation Fluid Dynamics in Volvo Technology is studied. Since the structure of the case in OpenFOAM is rather complex, one of the main purposes of this thesis work was also to make the process of using OpenFOAM as user-friendly as possible. The general conclusion that can be drawn from this work is that a very streamlined workflow can be, and has been, designed and created.
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Kumar, Suman. « Computational fluid dynamics (CFD) and physical modelling of a metal refining process ». Thesis, University of Greenwich, 2003. http://gala.gre.ac.uk/6213/.
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Impeller-stirred mixing is one of the most important processes employed throughout the chemical, metallurgical and allied industries. The research reported in this thesis is focused on impeller stirred mixing associated with the refining of lead bullion. The aim of this process is to sequentially remove contained impurities such as copper, antimony, silver and bismuth. This occurs in hemispherical vessels, called kettles, where reagents are initially added to the lead bath to form surface dross that contains both the required impurity and a large amount of lead oxide. This dross is then continuously mixed back into the bath to remove the lead oxide and capture more of the required impurity. A key requirement for this process is to obtain and remove dross that contains a high concentration of the impurity. Although this process has been in operation for many years, there is very little known on how the fluid dynamics associated with the mixing process affects final dross content. The aim of this research is to fully investigate the lead refining process using scientific analysis methods that help understand the mixing process and provide design tools which can be used to optimise process conditions. The three methods of analysis used are: (1) Direct readings from a real kettle, (2) Physical modelling (using water), and finally (3) Computational Fluid Dynamics (CFD). The use of physical modelling, exploiting the techniques of similitude, to predict vortex was also validated. An Acoustic Doppler Velocimeter (ADV) probe was used for the velocity measurement at various locations inside the water model and this gave valuable insight about the flow phenomena occurring inside the refining kettle. A particular important finding was that when fluid is stirred above certain rotational speed the vortex depth becomes independent of the Reynolds number of the operation. With regards CFD technology, the Volume of Fluid (VOF) method was used to capture the free surface and the Lagrangian Particle Tracking (LPT) and Algebraic Slip Model (ASM) to simulate the dross phase. Appropriate methods were also used to represent the moving impeller region. Validation of simulation results against experimental data was very encouraging. Computed vortex depth showed the similar trend as observed during the experiments on the physical model. A design strategy was developed that integrates results from both physical and computational modelling to allow optimal process conditions to be predicted at the kettle design stage. The use of this integrated physical and computational modelling methodology successfully helped eliminate surface swirl by introducing baffles to the kettle. The design and introduction of these flow controllers was also validated to ensure that it optimised the dross mixing process and final impurity content in the dross.
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Madani, Ario. « Fractionation of particle suspensions in a viscoplastic fluid : towards a novel process ». Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/35985.
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The focus of this thesis is the separation or sorting of particle suspensions in a yield stress or viscoplastic fluid. Although the process is applicable to most industrial suspensions, the motivation of the work stems from pulp and paper industry,i.e. papermaking and microfibrillated cellulose (MFC) suspensions. The work is presented in four different yet complementary studies.
In the first study, the concept of particle fractionation in a viscoplastic fluid is introduced. Here this novel principle is demonstrated, batch wise, by measuring
the difference in centrifugal force required to initiate motion of an initially stable particle suspension in a gel. The criteria for motion is delineated as the ratio of the centrifugal force to yield stress as a function of particle size and orientation. Demonstration experiments are given to illustrate that the separation process is very efficient. In the second and third studies we demonstrate the principle on two industrial suspensions, i.e. a SBK (semi-bleached kraft) papermaking fibre and MFC. With papermaking fibres, it is shown that efficient separation, based upon cell wall thickness can be achieved. With MFC, it is shown that the process is more efficient than traditional separation techniques, i.e hydrocyclone and pressure screen. In the final study, we speculate regarding the conditions required to make a continuous process based upon the batch testings. Here, it is identified that a spiral Poiseuille flow would be sufficient to achieve separation. The questions addressed in this study are what is the size of the unyielded region for this flow field and what is the bound for transition to turbulent flow. It was found that the magnitude of the swirling flow does not affect the size of the plug and the axial
velocity is decoupled from the rotational rate. In addition, the yielded region is always formed in the middle of the annular gap. To address the flow state, a linear stability analysis was performed using the method of normal modes. The flow was found to be linearly stable for all conditions tested.
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Fei, Yang. « Computational fluid dynamics and process co-simulation applied to carbon capture technologies ». Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/11521/.
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In the energy supply sector, coal will still remain as a dominate role in the foreseeable future because: it is comparatively cheap and widely distributed around the world and more importantly, carbon capture and storage (CCS) technologies make it possible to depend on coal with almost zero emission of carbon dioxide (CO2). CCS involves capturing and purifying CO2 from the emission source and then sequestering it safely and securely to avoid emission to the atmosphere. Both the post-combustion and the oxy-fuel technologies can be applied to existing power plants for CCS retrofit. Accurate prediction of the performance of a CCS plant plays an important role in reducing the technical risk of future integration of CCS with existing power plants. This research combines the fundamental computational fluid dynamics (CFD) and system process simulation technologies so that an efficient co-simulation strategy can be achieved. A 250 kWth coal combustion facility combined with a CO2 post capture plant is taken to test the conception of the CFD and process co-simulation approach. The CFD models are employed to account for the combustion facility and the predicted results on the outlet gas compositions, temperatures and mass flow rates are used to generate reduced order models to linked to the model for the PACT CO2 post capture plant so that a pilot scale whole plant model is achieved and validations have been made where it is possible. Afterwards, the a large scale conventional air-coal firing power plant is taken into investigation: the CFD models for the boiler and the process models for the whole plant have been developed. Further, the potential of retrofitting this power plant to oxy-firing is evaluated using a CFD and process co-simulation approach. The CFD techniques are employed to simulate the coal combustion and heat transfer to the furnace water walls and heat exchangers under air-firing and oxy-firing conditions. A set of reduced order models has been developed to link the CFD predictions to the whole plant process model in order to simulate the performance of the power plant under different load and oxygen enrichment conditions in an efficient manner. Simulation results of this 500 MWe power plant indicate that it is possible to retrofit it to oxy-firing without affecting its overall performance. Further, the feasible range of oxygen enrichment for different power loads is identified to be between 25% and 27%. However, the peak temperature on the superheater platen 2 may increase in the oxy-coal mode at a high power load beyond 450 MWe.
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McCarney, Jonathan Paul. « Reactions and process separations in environmentally benign media ». Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/30362.
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Bezzo, Fabrizio. « Design of a general architecture for the integration of process engineering simulation and computational fluid dynamics ». Thesis, Imperial College London, 2001. http://hdl.handle.net/10044/1/7142.
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Park, Chang Shin. « A dynamic behavior of pulp floc and fibers in the papermaking process ». Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/7044.
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Gebart, Rikard. « Analysis of heat transfer and fluid flow in the resin transfer moulding process ». Doctoral thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 1992. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26582.
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This thesis contains an analysis of fluid flow and heat transfer problems in the resin transfer moulding (RTM) process for manufacturing of polymer based fibre composites and it consists of five separate papers. The permeability of unidirectional fabrics, that are often used in advanced composites, is considered in Paper A and a theory for the permeability dependence on the micro geometry is developed. The theory is based on lubrication theory for narrow gaps which is motivated by the fact that most of the flow resistance comes from a small region where the fibres are closest to each other. Despite this limitation the results agree excellently with numerical results. 'Me best performance of the theory is expected at high fibre volume fractions (Vf) but the dependence on Vf is surprisingly good even at as low values as 0.3. Although the theory is formulated for an idealised geometry it can be used to predict the variation of the anisotropic permeability tensor with fibre volume fraction in real fabrics after fitting of three model parameters. Paper B is a study of the influence from different process parameters on the void content in the laminate. The void content is shown to be reduced strongly by an applied vacuum during mould filling. The main mechanism for void formation appears to be mechanical entrapment at the flow front. The voids are convected by the flow so that their concentration is highest close to the flow front. Microscopy investigation of the bubbles show that they are of two basic types, large spherical bubbles in the interstices between fibre bundles and smaller cylindrical bubbles inside the fibre bundles. The positive influence of vacuum compared to no vacuum can be explained as a combined effect of an increased mobility due to larger volume changes during mould filling and compression by the increased pressure during cure. In Paper C a comparison is made between the mould filling times for different injection strategies. The possible alternatives for a normal laminate are point injection, edge injection and peripheral injection. Theoretical results are derived that can be used to estimate the mould filling time with the different alternatives. In addition, fundamental theoretical results are derived from the governing equations showing the scaling of the mould filling time with the process parameters. This analysis also shows that the flow front motion during mould filling is only a function of the anisotropy of the reinforcement and the location of the gates. Paper D presents an analysis of the non-uniform flow at the flow front during impregnation of a stack of fabrics consisting of layers with different flow resistance. A detailed derivation of the theory and an analytical solution to the equations are presented in an addendum to Paper D. The theoretical model is compared with experimental results and is found to describe the experiment qualitatively well. The resulting permeability of a stack of different fabrics is derived from the basic equations and is found to be a weighted average of the permeability in the individual layers. This result is compared with experiments with different stacking sequences and it is found that the stacking sequence has no influence on the resulting permeability as expected from the theory. Experimental results in excellent agreement with Darcy's law are also presented for the case with radial flow and with unidirectional flow. Finally, Paper E is a theoretical study of the curing behaviour of thick laminates. A general solution independent of the cure kinetic model is derived. The solution is valid for low exothermal peak temperatures and it is characterised by two dimensionless numbers. The first parameter is the ratio between the time scales for the reaction and for heat conduction, the second parameter is the ratio between the processing temperature and the adiabatic temperature rise. The general solution is specialised to a second order autocatalytic cure model so that the results can be compared to numerical results. The agreement between the numerical and the analytical solution is excellent for small exothermal peak temperatures, as expected. The particular model used also serves as an example of the additional dimensionless parameters that are introduced by a specific kinetic model.Godkänd; 1993; 20070426 (ysko)
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Chen, Zhong. « Cutting fluid aerosol generation and dissipation in machining process : analysis for environmental consciousness ». Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17929.
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Cossey, Aaron Mitchell. « Computational fluid dynamic analysis of the purification process of the neutrino detector KamLAND ». Thesis, [Tuscaloosa, Ala. : University of Alabama Libraries], 2009. http://purl.lib.ua.edu/118.
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Lee, Brenda Ching Tsia. « The linking of process modeling of hopper-bottomed clarifier and computational fluid dynamics ». Thesis, Swansea University, 2009. https://cronfa.swan.ac.uk/Record/cronfa42841.
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MURER, MAURO. « Computational Fluid Dynamics simulations of Laser Metal Deposition process exploring open source software ». Doctoral thesis, Università degli studi di Pavia, 2021. http://hdl.handle.net/11571/1447833.
Texte intégralRésumé :
Laser Metal Deposition (LMD) is an innovative technology adopted in Additive Manufacturing (AM) processes and its use is becoming more and more popular in various application fields, such as part manufacturing, repair, and prototype fabrication. This technique is capable of creating several layers of solidified material, by the simultaneous delivery of metal powders and the laser beam, and offers an effective way to produce complicated geometries thanks to its high flexibility. However, complex physical phenomena occur during the additive process, which have a great impact on the success of the process, and many of these have yet to be fully understood. With the aim of shedding light on these aspects, a detailed numerical study, focused on LMD technology, will be conducted using three-dimensional models based on Com- putational Fluid Dynamics (CFD).
The particle flow problem regarding the coupling between the fluid phase (i.e., the carrier gas) and the solid phase (i.e., a metallic material powder) is first investigated using OpenFOAM, an open source software widely used in the CFD community. In particular, two different numerical approaches are investigated: the first approach is based on an Eulerian method to describe the carrier gas flow combined with a Lagrangian method to describe the particle flow (LE method), and the second approach is based on a pure Eulerian method to model both the carrier gas and the particle flow (EE method). Simulations results show the main features of the two approaches considered in terms of reliability in reproducing the key geometrical and physical features of the LMD process, together with a comparison with experimental evidences.
On the other hand, the thermal problem, that describes the interaction between particles flow and the laser beam, play a crucial role and cannot be neglected. For this purpose, the time-dependent Navier-Stokes equations for incompressible flows are coupled with the energy equation in order to represent the temperature field, whereas the Lagrangian description of the particle dynamic is enriched accounting the thermal evolution, and the consequent phase changing of the metallic powder due to the particle-laser interaction. This model is developed in a C++ in-house code using the open source Finite Element library deal.II and it is validated through consolidated results available in the literature. Furthermore, different schemes able to solve the Navier-Stokes equations, coupled with the heat transfer equation, are implemented and compared, so as to prove both accuracy and efficiency.
Then, with the aim of investigating the LMD process in detail, and in particular the thermal behaviour of the powder exiting from the nozzle, a sensitivity analysis is performed in terms of the parameters most meaningful from a technological viewpoint, i.e., the nozzle inclination, the carrier gas and powder flow rate, and the laser power. The results of such an analysis show that it is possible to predict both the configuration and the energy distribution that character- izes the flow of the powder leaving the nozzle until it reaches the substrate. In particular, the influence of both laser power and nozzle geometry to phase change conditions of powder flux are analyzed in order to improve the set up of the printing process, which can lead to increased productivity and less material waste.
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Lai, Ying Hoi. « Computational study of the transparent window for the water beam assisted form error in-process optical measurement method / ». View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?MECH%202009%20LAI.
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Zhang, Zhi. « On the Study of a Liquid Steel Sampling Process ». Doctoral thesis, KTH, Tillämpad processmetallurgi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-24385.
Texte intégralRésumé :
The liquid steel sampling method is one of the commonly used procedures in monitoring the steelmaking process. Besides it can be used for analyzing the dissolved alloys, hydrogen content and oxygen content, it can be also employed to monitor the inclusion characteristics at the steelmakings. Here, a crucial point is that the steel sampler should be filled and the metal solidifies without changing the inclusion characteristics. Therefore, the objective of this work is to fundamentally understand the liquid steel sampling process by means of analyzing and modeling the two-phase flow during the sampler filling process, and verifying the mathematical model by using the experimental data. The present dissertation presents an experimental and theoretical study of the filling process of both the lollipop-shaped sampler and the rectangular-shaped sampler. Firstly, a physical modeling by using a water model has been carried out to fundamentally investigate the flow pattern inside the sampler vessels during its filling. The flow patterns were obtained by a PIV system. Then, a mathematical model has been built to theoretically understand the phenomena. The commercial CFD code was used. Here, different turbulence model have been compared between the realizable k-ε turbulence model and Wilcox k-ω turbulence model. It concludes that the Wilcox k-ω turbulence model agrees well with the PIV measurements.HH Thus, the preferred it was further employed to predict the turbulent flow inside the production lollipop-shaped sampler fillings. It is important to find that the average collision volume in the production steel sampler without solidification at filling is about 30 times higher than that in a ladle furnace. In the end, the whole sampling system was modeled. The initial solidification during the filling was taken into account. Focus was on the influence of the initial solidification on the inclusion concentrations. A discrete phase model was used to simulate the movement of inclusions in the liquid steel. Some selected different sized primary inclusions that exist in the ladles at a steelmaking process were simulated. The same method of studying the filling procedure of the lollipop-shaped sampler was further applied to comprehensively investigate the rectangular-shaped sampler.QC 20100908
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Polton, Richard. « Numerical grid generation and its application in the solution of a model of the Vacuum-Arc Remelting (VAR) process ». Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323918.
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Bezuidenhout, Johan Jacobus. « Computational fluid dynamic modelling of an electric smelting furnace in the platinum recovery process ». Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/2022.
Texte intégralRésumé :
Thesis (MScEng (Process Engineering))--Stellenbosch University, 2008.The electric smelting furnace is found at the heart of the platinum recovery process where the power input from the electrodes produces a complex interplay between heat transfer and fluid flow. A fundamental knowledge of the dynamic system hosted by the electric furnace is valuable for maintaining stable and optimum operation. However, describing the character of the system hosted by the electric furnace poses great difficulty due to its aggressive environment. A full-scale threedimensional Computational Fluid Dynamics (CFD) model was therefore developed for the circular, three-electrode Lonmin smelting furnace. The model was solved as time dependent to incorporate the effect of the three-phase AC current, which was supplied by means of volume sources representing the electrodes. The slag and matte layers were both modelled as fluid continuums in contact with each other through a dynamic interface made possible by the Volume of Fluid (VOF) multi-phase model. CO-gas bubbles forming at electrode surfaces and interacting with the surrounding fluid slag were modelled through the Discrete Phase Model (DPM). To account for the effect of concentrate melting, distinctive smelting zones were identified within the concentrate as assigned a portion of the melting heat based on the assumption of a radially decreasing smelting rate from the centre of the furnace. The tapping of slag and matte was neglected in the current modelling approach but compensation was made for the heating-up of descending material by means of an energy sink based on enthalpy differences. Model cases with and without CO-gas bubbles were investigated as well as the incorporation of a third phase between the slag and matte for representing the ‘mushy’ chromite/highly viscous slag commonly found in this region. These models were allowed to iterate until steady state conditions has been achieved, which for most of the cases involved several weeks of simulation time. The results that were obtained provided good insight into the electrical, heat and flow behaviour present within the molten bath. The current density profiles showed a large portion of the current to flow via the matte layer between the electrodes. Distributions for the electric potential and Joule heat within the melt was also developed and showed the highest power to be generated within the immediate vicinity of the electrodes and 98% of the resistive heat to be generated within the slag. Heat was found to be uniformly distributed due the slag layer being well mixed. The CO-gas bubbles was shown to be an important contributor to flow within the slag, resulting in a order of magnitude difference in average flow magnitude compared to the case where only natural buoyancy is at play. The highest flow activity was observed halfway between electrodes where the flow streams from the electrodes meet. Consequently, the highest temperatures are also observed in these regions. The temperature distribution within the matte and concentrate layers can be characterized as stratified. Low flow regions were identified within the matte and bottom slag layer which is where chromite and magnitite deposits are prone to accumulate. The model results were partially validated through good agreement to published results where actual measurements were done while also falling within the typical operating range for the actual furnace. The modelling of the electric furnace has been valuably furthered, however for complete confidence in the model results, further validation is strongly recommended.
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Glasse, Benjamin [Verfasser]. « Monitoring of Metal Working Fluid Emulsion Quality by in-process Light Spectroscopy / Benjamin Glasse ». Berlin : epubli GmbH, 2015. http://d-nb.info/1074331206/34.
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Cole, Pamela Anne. « Cleaning of toothpaste from process equipment by fluid flow at laboratory and pilot scales ». Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4128/.
Texte intégralRésumé :
Cleaning studies were performed to remove toothpaste by fluid flow at different temperatures and velocities to mimic CIP (Cleaning-In-Place) processes on toothpaste coated coupons at laboratory scale and fully filled pipeline at pilot scale (different lengths and diameters). The cleaning time was reduced by increasing the velocity and temperature of the water, however no further time benefit was seen above 40°C. The adhesive force for different pastes calculated from micromanipulation data followed the same trend as cleaning times on the laboratory cleaning rig. This cleaning data for the different paste formulations had a logarithmic relationship with the viscosity term from the Herschel-Bulkley rheological model. Removal of toothpaste from pipes occurred by the core of the paste being removed from the centre of the pipe to leave a thin coating on the pipe wall, which was then eroded by flow. Pipes of lengths between 0.3 m and 2 m (47.7 mm diameter pipe) showed no difference in cleaning time. The rate limiting process was removal of the thin wall coating and therefore not a function of length. An inverse wall shear stress relationship with cleaning time was found to represent all the data, at all scales and under all conditions.
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Burström, Per E. C. « CFD-modelling of the SNCR process in iron ore grate-kiln plants ». Licentiate thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17047.
Texte intégralRésumé :
LKAB (Luossavaara-Kiirunavaara AB) is an international company that producesiron ore products for the steel industry; their main product is iron ore pellets.The aim with this research project is to numerically investigate if it is possible to use selective non-catalytic reduction (SNCR) technologies in grate-kiln pelletizingplants for NOx reduction. The technique had, to the best knowledge of the author, never been used in this context before despite that it is commonly used in cement and waste incineration plants. The investigation is done in several stages: 1) Reveal if the technique is possible to use with the two most commonly reagents ammonia and urea. 2) Derive a chemistry model for cyanuric acid so that this reagent also can be scrutinized. 3) Compare the reagents urea and cyanuric acid in the grate-kiln pelletizing process.A CFD model of parts of the real grate was created and numerical simulations with the commercial code ANSYS CFX was carried out solving the flow field. A model for spray injection into the grate was then included in the model enabling a study of the overall mixing between the injected reagent droplets and the NOx polluted air. It is shown that the SNCR technique with ammonia does not work in the grate-kiln process. Urea on the other hand can be used under some conditions and also cyanuric acid. The results lay grounds for a continued development of the proposed chemistry model.Godkänd; 2012; 20120201 (burper); LICENTIATSEMINARIUM Ämnesområde: Strömningslära/Fluid Mechanics Examinator: Professor Staffan Lundström, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Dr Henrik Wiinikka, ETC, Piteå Tid: Fredag den 2 mars 2012 kl 10.15 Plats: E231, Luleå tekniska universitet
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Wang, Zhe. « The Correlation between the Penetration Force of Cutting Fluid and Machining Stability ». Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-theses/779.
Texte intégralRésumé :
The purpose of this thesis is to investigate the correlation between the penetration force of cutting fluids and machining stability. General studies are made to understand the classification of cutting fluids based on their chemical compositions. It is summarized why the proper selection of cutting fluid for different machining processes is important. The role of cutting fluids in machining process is documented as well as other related issues such as delivery methods, storage, recycling, disposal and failure modes. The uniqueness of this thesis is that it constructs a new mathematical model that would help to explain and quantify the influence of the penetration force of cutting fluid on machining stability. The basic principles of milling process, especially for thin wall machining are reviewed for building the mathematical model. The governing equations of the mathematical model are derived and solved analytically. The derived solutions are used to construct the stability charts. The results show that there is a direct correlation between the machining stability and the changes of the penetration force of the cutting fluid. It is shown that the machining stability region is narrowed as the penetration force of the cutting fluid increases while other machining variables are assumed to be constant. This narrowness of the stability region is more obvious at spindle speed over 6000 rpm.
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Pamidi, Taraka Rama Krishna. « Process Intensification by Ultrasound Controlled Cavitation ». Licentiate thesis, Luleå tekniska universitet, Drift, underhåll och akustik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-73856.
Texte intégralRésumé :
Process industries are cornerstones in today’s industrialized society. They contribute significantly in the manufacturing of various goods and products that are used in our day-to-day life. Our society’s paradigm of consumerism accompanied by a rise in global population drives an ever increasing demand for goods. One of many strategies developed to satisfy these demands and at the same time improve production capabilities is known as process intensification. As an example, this can be accomplished by implementation of devices using the principle of hydrodynamic and acoustic cavitation. High-intensity cavitation in the ultrasonic range can change the physical and chemical properties of a wide range of substances and hence, improve the production rate or quality. Despite the generally accepted benefits of hydrodynamic and acoustic cavitation, applications in the process industry are yet limited. The reasons are that the method requires extensive optimization, which depends on multiple process parameters and encounters problem in the implementation on a larger scale. Scalable cavitation reactor concepts for industrial applications need to meet challenges like stability and robustness, energy efficiency and high flow rates. This thesis focuses on the methodology for the design and optimization of a flow through cavitation reactor. An ultrasound reactor concept has been developed and tested for two different applications: i) Fibrillation processes typical for paper and pulp industry; ii) Metal leaching of mineral concentrates. Simulations were carried out using a commercially available software for multiphysics modeling which combines acoustics, structural dynamics, fluid dynamics and piezoelectrics. However, the optimization procedure requires extensive experimental work in parallel with multi-physical simulations. In general, the application leads to hydrodynamic initiation of small gas bubbles in the fluid to be excited and collapsed by high-intensity ultrasound. This transient collapse of the cavitation bubbles provides both mechanical and chemical effect on materials. The developed reactor has a power conversion efficiency of 36% in batch mode and is well suited for a scale-up. In flow-through mode, the cavitation effect improves extensively and provides stable results. Energy efficiency requires hydrodynamic initiation of cavitation bubbles, high acoustic cavitation intensity by multiple excitation frequencies adapted to the optimized reactor geometry, as well as optimal process pressure and temperature with respect to the materials to be treated. The impact of flow conditions and hydrodynamic cavitation is significant and almost doubles the yield at the same ultrasonic power input. In the case of fibrillation of cellulose fibers, results obtained indicate that generated cavitation intensity changes the mechanical properties of the fiber wall. In the case of leaching, experiments show that six hours of exposure gave a 57% recovery of tungsten from the scheelite concentrate at 80°C and atmospheric pressure. Future research will focus on different types of excitation signals, extended reactor volume, increased flow rates and use of a higher process temperature.
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Wallace, Carol Leigh. « The investigation into the formation of coke in relation to the fluid catalytic cracking process ». Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248295.
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Wopat, Kathryn K. « Development of a to-scale fluid mixing visualization process for analysis of cold-flow mixing ». Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98752.
Texte intégralRésumé :
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (page 34).
Torrefaction is a process by which low energy density biomass is converted to a higher energy density biofuel, called char. Small-scale torrefaction systems are a promising technology for developing countries where large amounts of biomass go underutilized due to inaccessibility and transportation costs. A by-product of torrefaction is volatile gas, thus, a system may be built to harness this otherwise wasted energy and use it to power the treatment of biomass. An efficient fuel-mixer and combustor system which recycles this volatile gas is central to the overall torrefaction system efficiency. In order to analyze the mixing efficiency in a swirl-type mixer such as the design proposed for the small-scale torrefaction system, a project was designed to visualize mixing in an annular mixer. A to-scale cold-mixing system was constructed from two cylinders, three pump systems, as well as an imaging system using a retrofitted green laser. The final model is a tested and proven system for flow imaging of two cold flows within a to-scale fuel-mixer.
by Kathryn K. Wopat.
S.B.
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Nisal, Tejas V. « Monitoring of Surface Grinding process using Acoustic Emission (AE) with emphasis on Cutting Fluid selection ». University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1404341563.
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Yang, Ke. « Anaerobic treatment of a metalworking fluid and overcoming the toxic effects on the biodegradation process ». Thesis, University of Oxford, 2016. http://ora.ox.ac.uk/objects/uuid:fae32f24-e9f6-48df-9135-8ccca639dd86.
Texte intégralRésumé :
Metalworking fluids (MWFs) are petroleum emulsions employed for metal machining processes as coolants and lubricants. To date, they have been irreplaceable in modern heavy and manufacturing industries, with annual usage exceeding two billion litres worldwide. However, the large amount of MWFs, the highly concentrated complex recalcitrant and toxic petroleum components contained in them continue to cause significant concern in terms of sustainable routes of end-of-life treatment and disposal. Compared with other treatment methods, the anaerobic treatment method has significant advantages, such as the low capital, operating and maintenance costs and energy recovery. This latter factor has the potential benefit of generating bio-energy from waste organic matter whilst aerobic route leads to CO2 emission. However, the bio-toxicity of MWFs is a huge challenge in terms of employing bio-treatment of waste MWFs. In this study, the anaerobic biodegradability of a typical MWF was investigated employing an activated sludge experimental system. Furthermore, the toxic effects of the MWF on the anaerobic ecosystem, particularly on methanogen species, were investigated using bio-molecular analytical methods and a biosensor. In order to overcome its toxicity, the indigenous anaerobic bacteria isolated from spent MWFs were employed in the treatment of the MWF since they were assumed to be acclimated to the conditions. The major findings include: (1) approximately 80% of the MWF (5,000mgCOD/L) was found to be anaerobically biodegradable, with around 35% of the biodegraded COD could be converted to methane; (2) the MWF appeared to be toxic to the anaerobic ecosystem, especially to methanogen species; and (3) however, treatment employing the anaerobic bacteria successfully reduced the toxicity of the MWF and enhanced the methane production in the process.
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Vallespin, David. « Development of a process and toolset to study UCAV flight mechanics using computational fluid dynamics ». Thesis, University of Liverpool, 2011. http://livrepository.liverpool.ac.uk/6593/.
Texte intégralRésumé :
The work carried out during this project used a computational Fluid Dynamics code to generate aerodynamic tabular models and aircraft manoeuvre simulations. As an outcome of this work, a validation of the aerodynamic prediction tools and an assessment of tabular models for aircraft flight dynamics applications was made. The Stability and Control Unmanned Combat Air Vehicle has been used as a demonstration case. Validation of computational fluid dynamics methods was carried out for highly nonlinear flow topologies using wind tunnel measurements. Integral data, pressure tap measurements and particle image velocimetry information was compared against the predictions over two configurations. Each one had a different leading edge shape distributed along the span of the model. One was sharp throughout with varying leading edge thickness and the other one was mainly rounded. Results showed a good agreement in longitudinal force and moment predictions for low angles of attack. High angles were dominated by a double vortex structure which was very sensitive to incidence angle and leading edge shape. Some wind tunnel effects were noticed in the measurements when predictions were made with and without sting. Overall the numerical predictive capabilities for low and high angles of attack were deemed good for the purpose of flight dynamics model generation. Two methods for predicting manoeuvering flight aircraft loads are presented in this thesis. A tabular aerodynamic model based on numerical predictions was generated for the sharp configuration. Kriging interpolation was used to populate a model consisting of tables of lateral and longitudinal aerodynamic characteristics. Further to this, longitudinal dynamic derivatives were predicted for the test case in hand using forced oscillation numerical predictions. Aircraft geometric characteristics were approximated based on real aircraft data. A set of controls were designed and implemented for the purpose of manoeuvering flight predictions. A code was implemented to predict realistic aircraft manoeuvres based on an existing program. At the core of this method was a commercial optimisation Matlab code called DIDO. Using this and the nonlinear, six degree of freedom equations of motion, purposedly designed aircraft manoeuvres were predicted. The motions were then replayed using time-accurate simulations and the predicted loads were compared against the tabular predictions. In this manner, the validity of the tables of aerodynamic data were benchmarked against a more reliable and expensive numerical method. The static based predictions showed good agreement with the replays for slow manoeuvres at low angles of attack. As manoeuvres became more aggressive, noticeable disagreement was present in the aircraft loads, particularly in the lateral characteristics during periods of large rates of change in attitudes. Hysteresis effects during manoeuvering flight were seen to produce large spreads in data in the angle of attack domain which the predicted dynamic derivatives were unable to capture.
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Steigmiller, Daniela [Verfasser]. « Application of Process Analytical Technology for Investigation of Fluid Bed Granulation and Active Coating during Process Development and Scale-up / Daniela Steigmiller ». Bonn : Universitäts- und Landesbibliothek Bonn, 2012. http://d-nb.info/1044866624/34.
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Illes-Smith, Peter C. « A study of the modelling, dynamic simulation and control of the modern fluid catalytic cracking process ». Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330143.
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Sims, Jesse N. L. « Exploration of fluid intake practices in endurance running ». Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/226656/1/Jesse_Sims_Thesis.pdf.
Texte intégralRésumé :
Utilising a survey based approach, this thesis aimed to understand how fluid intake practices differ among endurance runners and characterise how fluid practices may reflect performance outcomes. The findings from this study indicate that collectively there is no difference between sex when exploring fluid intake beliefs and behaviours towards hydration optimisation strategies. This suggests that human behaviour is influential in understanding fluid intake practices in endurance runners. Fluid intake optimisation strategies are highly individualised and further research is still required to shape the avenue for future fluid intake recommendations.
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Ma, Rui. « Development and experimental validation of a CFD model for Pd-based membrane technology in H2 separation and process intensification ». Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-dissertations/544.
Texte intégralRésumé :
Syngas production and hydrogen separation technologies are very mature, and also extremely important for energy and chemical industries. Furthermore, these processes are the most expensive elements for many applications such as hydrogen production from renewable sources. Enhancing or intensifying these very mature technologies is very challenging, but would have tremendous impact on the performance and economics of many processes. Traditional Integrated Gasification Combined Cycle (IGCC) for syngas production need to include a carbon capture process in order to regulate their carbon dioxide emission as more and more countries and regions have implemented carbon tax policy. Integration of this process with Pd membrane has long been considered a key component to make it more feasible. With these two technologies combined together, we can produce high purity hydrogen while capturing carbon dioxide and toxic gases from the syngas product. Besides, although manufacturing the membrane reactor is expensive, after considering the carbon tax factor, it actually is more economically preferable compare with the traditional Pressure Swing Adsorption (PSA) process. Most research on Pd membrane technology has been conducted at lab scale; nonetheless, the contribution of a palladium membrane technology to economic and societal development requires its commercialization, diffusion and utilization. To generate enough incentives for commercialization, it is necessary to demonstrate the scalability and robustness of the membranes in industrial settings. Consequently, a multitube membrane module suitable for IGCC system was designed and manufactured and sent to National Carbon Capture Center (NCCC) for testing. This work developed a Computational Fluid Dynamics (CFD) model for the module and validated the model utilizing the pilot-scale experimental data generated under industrial conditions. The model was then up-scaled and used to determine the intrinsic phenomena of palladium membrane scale up. This study reveals the technical/engineering requirements for the effective design of large-scale multitube membrane modules. Mass transfer limitations and concentration polarization effects were studied quantitatively with the developed model. Methods for diminishing the concentration polarization effect were proposed and tested through the simulations such as i) increasing convective forces and ii) designing baffles to create gas recirculation. For scaled-up membrane modules, mass transfer limitation is an important parameter to consider as large modules showed severe concentration polarization effects. IGCC systems produce H2 from coal combustion; other ways of H2 production include steam-reforming processes, using natural gas or bio-ethanol as the reactant. The product contains a mixture of H2, CH4, CO, CO2 and steam. Thus, steam-reforming processes are often followed by a Pressure Swing Adsorption (PSA) unit in order to obtain pure hydrogen. Palladium membrane, on the other hand, can be integrated with steam-reforming processes and achieve the simultaneous production and purification of H2 in a single unit by reaching process intensification. Higher H2 production rate can be reached by process intensification as one of the products H2 is constantly being removed. Temperature control is a very important topic in steam reforming processes, as the reaction is overall highly endothermic; although implementing an in-unit membrane improves H2 production rate, it also makes the temperature control more difficult as the reaction equilibrium is altered by the removal of one of the products H2. Hereby, an experimental study of catalytic membrane reactor (CMR) was carried out along with both isothermal and non-isothermal CFD simulations that are validated by the experimental data in order to visualize the temperature distribution inside the reactor and understand the influence of the operating conditions including temperature, pressure and the sweep gas flow patter on the permeate side.
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Wu, Liushun. « Study on some phenomena of slag in steelmaking process ». Doctoral thesis, KTH, Mikro-modellering, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32740.
Texte intégralRésumé :
The present work is to study slag phenomena in steelmaking process. In order to attain thegoal, a number of high temperature experiments and simulation experiments were carried out. Four master slags were used to study the effect of CaF2 on slag viscosity. Experimentalresults indicated the effect of CaF2 on slag viscosity depended strongly on the composition ofmaster slag. For high basicity slags, CaF2 mainly suppressed the precipitation of solid phasesat lower temperatures, leading to a lower viscosity compared to CaF2-free slags. For slagswith higher SiO2 contents, CaF2 both lowered the viscosity of the liquid phase and suppressedthe precipitation of solid phases. The viscosities of solid-liquid mixtures were experimentally determined for silicon oilparaffinsystem at room temperature and solid-liquid oxide mixture at steelmakingtemperature. The results of both measurements indicated that the increasing trend of mixturesviscosity with particle fraction can be described by Einstein-Roscoe equation.Silicone oils of different viscosities were used to simulate slag foaming. The experimentalresults showed, at a constant viscosity, the foaming height increased first with superficialvelocity before reaching a maximum value. Thereafter, the foaming height decreased with thefurther increase of the superficial velocity. Similar, a maximum foaming height was observedat an optimum viscosity when a constant superficial gas velocity was applied. Based on theexperimental data, a semi-empirical equation of foaming height was developed. Thepredictions of the model agreed well with experiment data. The model could also reasonablywell explain the industrial pilot trial experiments. Water-silicon oils model and liquid alloy (Ga-In-Sn)- 12% HCl acid model were employed tosimulate the formation of open-eyes in a gas stirred ladle. The experimental results indicatedthat the viscosity of the top liquid and the interfacial tension between the two liquids had onlylittle effect on the open-eye size. A semi-empirical model was developed to describe the sizeof open-eye as functions of the gas flow rate, bath height and slag height. The two sets ofparameters obtained for the water and Ga-In-Sn models were very different. Industrial trialswere also conducted to examine the applicability of the models. Liquid alloy model couldwell predict the formation of an open-eye during ladle treatment. Two cold models, sodium tungstate-oil model and water-oil model, were carried out tosimulate the formation of droplets in a gas stirred ladle. The experimental results showed thatthe gas flow rate and interfacial tension had strong impact on the size of droplets. A semiempiricalmodel was developed to describe the size of droplets for water model. Meanwhile,the parameter obtained for water model can be used for sodium tungstate-silicone oil system.The results indicate the model has strong compatibility.QC 20110419
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Charmchi, Isar. « Computational Fluid Dynamics (CFD) Modeling of a Continuous Crystallizer ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Trouver le texte intégralRésumé :
Crystallization is one of the most important separation and purification processes in chemical and especially in pharmaceutical industries. Currently most crystallization processes in the industry are based on batch crystallization; however, due to the variation of product quality per batch, efforts
are made to move to continuous processes instead. In this
respect, micro and meso scale reactors represents a promising technology due to enhanced heat and mass transfer rates, which, translated to particle generation,
provide control of size, morphology, and composition. In this
study, a meso-scale continuous crystallizer has been characterized and optimized.
A stirred tubular continuous-crystallizer has been characterized and optimized
in which the crystallization of active pharmaceutical ingredients (APIs) can
be performed under controlled conditions. The crystallizer is formed by two tubes,
one for nucleation and the other one for growth, in order to separate different phenomena
to control better the process and hence the crystal size distribution. The
optimized nucleation tube has a length of 35 cm and a diameter of 3 cm with a
long axial blade across the tube with the length of 30 cm and 2.5 cm of diameter.
The phenomena of mixing helps to achieve homogeneous supersaturation along the
tube to prevent growth during the nucleation and enables narrow residence time
distribution of the crystals in the tube with the help of gravity to achieve narrower
crystal size distribution.
Computational
fluid dynamics (CFD) is used to optimize the process. CFD is the
application of numerical methods to solve systems of partial differential equations
related to
fluid dynamics. The continuity and the momentum equations are the
most commonly applied equations within CFD, and together they can be used to
calculate the velocity and pressure distributions in a
fluid.
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Norrell, Jeffery Lee. « A mixed mode thermal/fluids model for improvements in SLS part quality, machine design, and process design / ». Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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