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1
Scanlon, Thomas J. "Vortex shedding flowmeter pulsating flow CFD studies." Thesis, University of Strathclyde, 1992. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21339.
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The computational analysis of vortex shedding flow is presented, using the commercially available computational fluid dynamics(CFD) software package PHOENICS. In this analysis it is shown how the use of the conventional PHOENICS default first-order hybrid-upwind convective differencing scheme provides an excellent example of the effects of multidimensional false diffusion. These effects are substantially reduced with the introduction of an alternative scheme, SUCCA ( Skew Upwind Corner Convection Algorithm), for the modelling of convective transport in 2D and 3D analyses; resulting in the promotion of continuous vortex shedding for the 2D model. The mechanism of pulsating flow influence on the vortex shedding process has also been simulated. The results show that a complex transient phenomenon such as vortex shedding can be analysed using the PHOENICS code but only with the implementation of an alternative convection algorithm. The results also demonstrate the SUCCA scheme's ability to accurately represent convective transport and hence substantially reduce the effects of multidimensional false diffusion in numerical flow analyses.
2
Eesa, Muhammad. "CFD studies of complex fluid flows in pipes." Thesis, University of Birmingham, 2009. http://etheses.bham.ac.uk//id/eprint/413/.
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The flow of rheologically complex fluids in industrial equipment poses a number of challenges, not least from a modelling point of view. Research is needed to further understand and be able to predict the flow behaviour of such materials and to investigate ways of improving their processing. This work investigates the numerical modelling of complex fluids in three areas: flow and heat transfer under an externally imposed mechanical vibration, and steady-state solid-liquid flows as a first step in extending the vibration studies to these multiphase systems. Validated CFD simulations were used to study the effects of rotational and transversal mechanical vibrations on the pipe flow of viscous non-Newtonian fluids of the power-law, Bingham plastic, and Herschel-Bulkley types. Vibration frequencies in the sonic range of 0-300 Hz and linear amplitudes of 0-4 mm were used. The results showed that rotational and transversal vibrations give rise to substantial enhancements in flow for shear thinning and viscoplastic fluids, while shear thickening fluids experienced flow retardation. The flow enhancement was found to depend on vibration frequency and amplitude, fluid rheological properties, and pressure gradient. These vibrations can be effective at enhancing the flow of low to moderately viscous fluids in industries such as the confectionery industry. For extremely viscous fluids (consistency index ~10 kPa s\(^n\) and yield stress ~200 kPa), ultrasonic frequencies (> 16 kHz) were found to produce orders of magnitude enhancements in flow. These results suggest that vibration can increase the fluidity of highly viscous fluids in industrial applications such as polymer extrusion. Results are also reported for the effects of transversal vibration on heat transfer and temperature uniformity in Newtonian and non-Newtonian shear thinning fluids. Vibration was found to generate sufficient chaotic fluid motion that led to considerable radial mixing which translated into a large enhancement in wall heat transfer as well as a near-uniform radial temperature field. Vibration also caused the temperature profile to develop very rapidly in the axial direction, thus, reducing the thermal entrance length by a large factor, so that much shorter pipes can be used to achieve a desired exit temperature. These effects increased with both vibration frequency and amplitude but were more sensitive to the amplitude. Higher fluid viscosities required larger amplitudes and/or frequencies to achieve substantial temperature uniformity. These results have significant implications for processes where a wide temperature distribution over the pipe cross-section is undesirable as it leads to an uneven distribution of fluid heat treatment, such as in the thermal sterilisation of food products. A numerical study was also conducted of the laminar pipe transport of coarse spherical particles (d = 2-9 mm) in non-Newtonian carrier fluids of the power law type using an Eulerian-Eulerian CFD model. The predicted flow fields were validated by PEPT experimental measurements of particle velocity profiles and passage times, whilst solid-liquid pressure drop was validated using relevant correlations gleaned from the literature. The study was concerned with nearly-neutrally buoyant particles (density ~1020 kg m\(^{-3}\)) flowing in a horizontal or vertical pipe at concentrations up to 40% v/v. The effects of various parameters on the flow properties of such mixtures were investigated over a wide range of conditions. Whilst the effects of varying the power law parameters and the mixture flow rate for shear thinning fluids were relatively small over the range of values considered, particle size and concentration had a significant bearing on the flow regime, the uniformity of the normalised particle radial distribution, the normalised velocity profiles of both phases, and the magnitude of the solid-liquid pressure drop. The maximum particle velocity was always significantly less than twice the mean flow velocity for shear thinning fluids, but it can exceed this value in shear thickening fluids. In vertical down-flow, particles were uniformly distributed over the pipe cross-section, and particle diameter and concentration had little effect on the normalised velocity and concentration profiles. Pressure drop, however, was greatly influenced by particle concentration. These results can help in understanding and predicting the flow behaviour of such solidliquid mixtures in industrial applications, such as the conveying of particulate food suspensions.
3
Shaw, Michael James. "An assessment of CFD for transonic fan stability studies." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709038.
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Ke, Xinyou. "CFD Studies on Mass Transport in Redox Flow Batteries." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1396626452.
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5
Wang, Zhiguo. "Experimental studies and CFD simulations of conical spouted bed hydrodynamics." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/61.
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Conical spouted beds have been commonly used for drying suspensions, solutions and pasty materials. They can also be utilized in many other processes, such as catalytic partial oxidation of methane to synthesis gas, coating of tablets, coal gasification and liquefaction, pyrolysis of sawdust or mixtures of wood residues.
The main objectives of this work include both the experimental research and mathematical modelling of the conical spouted bed hydrodynamics.
For experimental research, pressure transducers and static pressure probes were applied to investigate the evolution of the internal spout and the local static pressure distribution; optical fibre probes were utilized to measure axial particle velocity profiles and voidage profiles; the step tracer injection technique using helium as the tracer and thermal conductivity cells as detectors was used to investigate the gas mixing behaviour inside a conical spouted bed. It was found that many factors might affect calibration of the effective distance of an optical fibre probe. Therefore, a new calibration setup was designed and assembled, and a comprehensive sensitivity analysis was conducted to calibrate the optical probes used in this study.
For mathematical modelling, a stream-tube model based on the bed structure inside a conical spouted bed was proposed to simulate partial spouting states. By introducing an adjustable parameter, this model is capable of predicting the total pressure drop under different operating conditions, and estimating axial superficial gas velocity profiles and gauge pressure profiles.
A mathematical model based on characteristics of conical spouted beds and the commercial software FLUENT was also developed and validated using measured experimental data. The proposed new CFD model can simulate both stable spouting and partial spouting states, with an adjustable solids-phase source term. At stable spouting states, simulation results agree very well with almost all experimental data, such as static pressure profiles, axial particle velocity profiles, voidage profiles etc. A comprehensive sensitivity analysis was also conducted to investigate the effect of all possible factors on simulation results, including the fluid inlet profile, solid bulk viscosity, frictional viscosity, restitution coefficient, exchange coefficient, and solid phase source term.
The proposed new CFD model was also used successfully to simulate gas mixing behaviours inside a conical spouted bed, and simulate cylindrical packed beds as well as cylindrical fluidized beds in one code package.
6
Pundi, Ramu Arun Mr. "CFD Studies on the Flow and Shear Stress Distribution of Aneurysms." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1247820620.
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7
Abdulkadir, Mukhtar. "Experimental and computational fluid dynamics (CFD) studies of gas-liquid flow in bends." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12218/.
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Within the oil industry there is a need to measure and predict the form of the multiphase liquid and gas flows that are present within oil production and processing pipelines. Knowledge of the flow regimes present allows the engineer to optimise the configuration of the pipeline and downstream processes to achieve the most, economic and reliable design. The applications of these technologies are collectively known as flow assurance. Within oil production systems, one component which has received little attention is the characterisation of the multiphase flow around bends under various process conditions. To predict the flow regimes in greater details requires the development of instrumentation that can measure and characterise the flow within the pipes. To circumvent this challenge, two experimental investigations were carried out in two rigs available in the Chemical and Environmental Engineering Laboratories at the University of Nottingham. These are: (1) a 67 mm internal diameter pipe joined to a 90o bend, in which air/silicone oil flows were investigated using advanced instrumentation: Electrical Capacitance Tomography (ECT), Wire Mesh Sensor Tomography (WMS), and high-speed video. The first two provide time and cross-sectionally resolved data on void fraction. The ECT probes were mounted 10 diameters upstream of the bend whilst the WMS was positioned either immediately upstream or immediately downstream of the bend. The downstream pipe was maintained horizontal whilst the upstream pipe was mounted either vertically or horizontally. The bend (R/D = 2.3) was made of transparent acrylic resin. The superficial velocities of the air ranged from 0.05 to 4.73 ms-1 and for the silicone oil from 0.05 to 0.38 ms-1. (2) a 127 mm internal diameter riser joined to a vertical 180o bend, in which measurements of film fraction and liquid film thickness distribution for an air-water system were obtained using the electrical conductance technique. The former was measured using the ring conductance probes placed 17 and 21 diameters, respectively upstream and downstream of the bend, 45o, 90o and 135o within the bend. The latter were obtained using pin and parallel wire probes. The pin probes were used for thin films measurement whilst the parallel wire probes for thick films. The bend, made of transparent acrylic resin, has a curvature ratio (R/D = 3). The superficial velocities of the air ranged from 3.5 to 16.1 ms-1 and for the water from 0.02 to 0.2 ms-1. The experimental results for the 90o bend study reveal that bubble/spherical cap bubble, slug, unstable slug and churn flows were observed before the bend for the vertical pipe and plug, slug, stratified wavy and annular flows when the pipe was horizontal. Bubble, stratified wavy, slug, semi-annular and annular flows are seen after the bend for the vertical 90o bend, the flow patterns remained the same as before the horizontal 90o bend. These results were confirmed by the high-speed videos taken around the bend. For the vertical 180o return bend, the average film fraction was identified to be higher in straight pipes than in bends. For low liquid and higher gas flow rates, due to the action of gravity drainage, film breakdown occurs at the 45o bend. A previously proposed criterion, to determine stratification after the 90o bend, based on a modified Froude number have been shown to be valid for a liquid different from that tested in the original paper. Similarly, for the 180o return bend, the condition for which the liquid goes either to the inside or outside of the bend are identified based on published material. Variations between average liquid film thickness and bend angles are reported for the vertical 180o bend. Contrary to the conclusions reached by Hills (1973) and Anderson and Hills (1974), the liquid film thickness becomes annular flow in the 180o bend at low liquid flow rates and stratified flow at higher liquid superficial velocities. In addition, a CFD code has been used to successfully model the hydrodynamics of the slug flow pattern in a riser and vertical 90o bend, using the Volume of Fluid model based on the Eulerian approach, implemented in the commercial CFD package Star-CCM+. The modelling results are validated with the experiments and also provide more detailed information on the flow such as the velocity field.
8
Kurniawan, K. P. "Studies of fundamental process occurring in precalciners and cyclone preheater tower using CFD." Thesis, Cardiff University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531015.
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Birkby, Paul. "Numerical studies of reacting and non-reacting underexpanded sonic jets." Thesis, Loughborough University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297581.
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10
Salgado-Ayala, Rodrigo. "Studies of flow and scalar distribution in two large industrial environments." Thesis, University of Bristol, 2000. http://hdl.handle.net/1983/f2aa1bf4-08f4-41cb-a6e0-d2641c01e222.
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11
Kramer, Edward S. "COMPUTATIONAL STUDIES OF DYNAMICS OF PRESSURE-DRIVEN DROPS IN MICRO-CHANNELS." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/317.
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In particulate flows, the flow inertia impacts the motion and size distribution of the particles and this in turn, has a strong implication on global behavior of the emulsions such as their rheological properties. As such, the central goal of most of the investigations on dispersed multiphase flow, so far, has been to understand the phase distribution of particles and to correlate the global behavior of the system with this parameter. For pressure-driven particulate flows in a channel, it is known that the velocity gradient in the channel leads to a lateral force whose magnitude and direction depends on the viscosity and density ratios of the fluids and the drop deformation. This lateral (lift) force is the primary reason behind the various observed modes of phase distribution of the particles. Unfortunately, most of the studies conducted so far have been concerned with the solid particles and for flows at low to moderate Reynolds numbers. Little is known about the dynamics of deformable drops at high Reynolds numbers. The goal of this study is to bridge the gap by direct numerical simulations. A front tracking/finite difference technique is used to solve the Navier-Stokes equations in the fluids inside and outside of the drops. Initially, the drops are randomly distributed in the computational domain their evolutions are followed for a sufficiently long time so that the system reaches a quasi-steady state. The statistics about the flow then will be extracted. The flow inertia is increased incrementally by increasing the pressure gradient.
12
Beavis, Nicholas J. "Numerical studies of gasoline direct injection engine processes." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/25230.
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The GDI engine has a number of practical advantages over the more traditional port-fuel injection strategy, however a number of challenges remain the subject of continued research in an attempt to fully exploit the advantages of the GDI engine. These include complex in-cylinder flow fields and fuel-air mixing strategies, and significant temporal variation, both through an engine cycle and on a cycle-by-cycle basis. Despite advances in experimental techniques, the relative difficulty and cost of taking detailed measurements remains high, thus computational techniques are an integral part of research activities. The research work presented in this thesis has focused on the use of detailed 3D-CFD techniques for investigating physical phenomena of the in-cylinder flow field and fuel injection process in a single cylinder GDI engine with early injection event. A detailed validation of the numerical predictions of the in-cylinder flow field using both the RANS RNG k-ε turbulence model and the Smagorinsky LES SGS turbulence model was completed with both models showing good agreement against available experimental results. A detailed validation of the numerical predictions of the fuel injection process using a Lagrangian DDM and both RANS RNG k-ε turbulence model and Smagorinsky LES SGS turbulence model was completed with both models showing excellent agreement against experimental data. The model was then used to investigate the in-cylinder flow field and fuel injection process including research into: the three dimensional nature of the flow field; intake valve jet flapping, characterisation, causality and CCV, and whether it could account for CCV of the mixture field at spark timing; the anisotropic characteristics of the flow field using both the fluctuating velocity and turbulence intensity, including the increase in anisotropy due to the fuel injection event; the use of POD for quantitatively analysing the in-cylinder flow field; investigations into the intake valve, cylinder liner and piston crown spray plume impingement processes, including the use of a multi-component fuel surrogate and CCV of the formed liquid film; characterisation and CCV of the mixture field though the intake and compression strokes up to spark timing. Finally, the predicted turbulence characteristics were used to evaluate the resultant premixed turbulent combustion event using combustion regime diagrams.
13
Li, Huafeng, and s3024014@student rmit edu au. "Numerical and experimental studies of air and particle flow in the realistic human upper airway models." RMIT University. Aerospace, Mechanical & Manufacturing Engineering, 2010. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20100205.145548.
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The human upper airway structure provides access of ambient air to the lower respiratory tract, and it as an efficient filter to cleanse inspired air of dust bacteria, and other environmental pollutants. When air passes through airway passages, it constantly changes direction, which may lead to flow separation, recirculation, secondary flow and shear stress variations along the airway surface. Therefore, it is essential to understanding the air transport processes within the upper airway system. The functions are respiratory defence mechanisms that protecting the delicate tissues of the lower airway from the often harsh conditions of the ambient air. While protecting the lower respiratory system, however, the upper airway itself becomes susceptible to various lesions and infections from filtration of environmental pollutants. Inhaled particle pollutants have been implicated as a potential cause of respiratory diseases. In contrast, inhalation of drug particles de posited directly to the lung periphery results in rapid absorption across bronchopulmonary mucosal membranes and reduction of the adverse reactions in the therapy of asthma and other respiratory disorders. For this purpose, it is desirable that the particles should not deposit in the upper airways before reaching the lung periphery. Therefore, accurate prediction of local and regional pattern of inhaled particle deposition in the human upper airway should provide useful information to clinical researchers in assessing the pathogenic potential and possibly lead to innovation in inhalation therapies. With the development of the increasing computer power and advancement of modeling software, computational fluid dynamics (CFD) technique to study dilute gas-particle flow problems is gradually becoming an attractive investigative tool. This research will provide a more complete picture of the detailed physical processes within the human upper airway system. Owing to the significant advancements in computer technologies, it will allow us to efficiently construct a full-scaled model integrating the various functional biological elements including the nasal, oral, laryngeal and more generations of the bifurcation of the human upper airway system through imagining methodologies. A significant advantage of this human model is that the differences in airway morphology and ventilation parameters that exist between healthy and diseased airways, and other factors, can be accommodated. This model will provide extensive experimental and numerical studies to probe significant insights to the particle deposition characte ristics within the complex airway passages and better understanding of any important phenomena associated with the fluid-particle flow. It will also lead to an improved understanding of fluid/particle transport under realistic physiological conditions. New concepts and numerical models to capture the main features observed in the experimental program and innovative techniques will be formulated. The ability to numerically model and a better physical understanding of the complex phenomena associated with the fluid dynamics and biological processes will be one of the major medical contributions especially targeting drug delivery and health risk analysis. Its biomedical engineering significance lies in the fact that this will enable us to accurately evaluate potential biological effects by the inhaled drug particles, facilitating new drug research and development.
14
Hao, Pingjiao. "Studies of Air Dehydration by Using Hollow Fiber Modules." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1320780921.
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Viti, Valerio. "Numerical Studies of the Jet Interaction Flowfield with a Main Jet and an Array of Smaller Jets." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/11267.
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A numerical study of a proposed innovative jet interaction configuration is presented. This work aimed at improving present-day jet interaction configurations in their applications as control thrusters on hypersonic vehicles. Jet thrusters are a useful control system for fast-moving vehicles flying in the upper layers of the atmosphere because of their effectiveness and responsiveness. They produce a strong and responsive lateral force on the vehicle through the interaction of two main mechanisms. The first mechanism comes from the momentum of the injectant itself, basically the thrust of the jet. The second and subtler contribution comes from the jet interaction flowfield, the interaction of the expanding injectant with the crossflow. This interaction produces areas of high pressure ahead of the injector and areas of low pressure in the region aft of the jet. The combination of the high-pressure regions in front of and low-pressure regions aft of the injector produces an undesirable nose-down pitching moment on the vehicle. In order to counterbalance the nose-down attitude, modern-day thruster designs include a large secondary injector far aft of the center of gravity of the vehicle. The thrust of this second injector acting far aft of the primary injector neutralizes the nose-down pitching moment. This is not an efficient method to obviate the problem since it requires the vehicle to be designed to carry two large thrusters and double the quantity of fuel necessary for one thruster. In light of these considerations, this study aimed at developing a jet interaction configuration that can dispense from the need of a large secondary injector to compensate for the nose-down pitching moment. The cases studied here were first a primary jet alone and then a primary jet with pairs of smaller jets. This configuration was based on the notion that the interaction of the secondary jets, conveniently located immediately aft of the thruster, with the barrel shock and the wake of the primary jet can drastically reduce the nose-down pitching moment. Because of the complexity of the jet interaction flowfield the investigation of the feasibility and the assessment of the efficiency of the new jet interaction configurations combined the present numerical effort with experimental studies of jet interaction flowfields performed in the supersonic wind tunnel at Virginia Tech.
During the present numerical study the jet interaction flowfield associated with the sonic injection of a gas into a high-speed crossflow was simulated by numerically solving the Reynolds Averaged Navier Stokes (RANS) equations. Turbulence was modeled through a first-order model, the Wilcox's 1988 k-w turbulence model. The computations made use of the finite volume code General Aerodynamic Simulation Program (GASP) Version 4. For simplicity and to keep the study general, the jet interaction flowfield was studied on a flat plate instead of a body of revolution as on a vehicle. Calculations were run for a number of jet interaction configurations consisting of a primary jet alone, a primary jet and one pair of secondary jets, and a primary jet and two pairs of secondary jets. The flow conditions of the simulations ranged from a Mach number of 2.1 up to a Mach number of 4.5 and jet total pressure to freestream static pressure ratios of 14 to 680. A large effort was dedicated to the development of an efficient computational grid that could capture most of the flow-physics with a minimum number of cells. To this end , Chimera or overset grids were employed in the simulation of the secondary injectors. Grid convergence was shown to be achieved for the case of single injection by conducting a thorough convergence study. The discretization error was calculated through a modified Richardson extrapolation to be low. The numerical solutions were compared to the experimental results in order to assess the capability of RANS equations and of first-order turbulence models to properly simulate the complex flowfield. The k-w turbulence model proved to be reliable and robust and the results it provided for this type of flowfield were accurate enough from an engineering standpoint to make informed decisions about the configuration layout. In spite of the overall good performance, the k-w turbulence model failed to correctly predict the flow in the regions of strong adverse pressure gradients. Comparisons with experimental results showed that the separation region was often under-predicted thus highlighting the need to employ better turbulence models for more accurate results. The RANS equations were found accurate enough to provide physical mean-flow solutions. Further, the numerical simulations provided information about the detailed physics of the flowfield that is impossible to obtain through experimental work. The analysis of the numerical solutions highlighted the existence of a complex system of counter-rotating trailing vortices that are responsible for the mixing of the injectant with the freestream. The typical features of the flowfield created by an under-expanded jet exhausting in a quiescent medium were visible in the jet interaction flowfield with the difference of the existence of a crossflow and a non-uniform back-pressure. The region of low pressure aft of the injector was shown to be generated by the detachment of the barrel shock from the surface of the flat plate that leaves a large volume to be filled by the surrounding fluid.
The simulations showed that the innovative configuration with one primary jet and an array of smaller secondary jets can effectively decrease the nose-down pitching moment by as much as 160%. In some cases, it also increased the total normal force acting on the flat plate (namely the thrust) by as much as 3%. This effect was found to be caused by the reduction in size and intensity of the low-pressure region aft of the primary injector.Ph. D.
16
Karimpourian, Bijan. "CFD modelling and experimental studies on the fluid flow and heat transfer in copper heat sink design /." Västerås : Department of Public Technology, Mälardalen University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-197.
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Schwarz, Eva [Verfasser]. "CFD-based studies of active wind turbine load control by means of trailing edge flaps / Eva Schwarz." München : Verlag Dr. Hut, 2021. http://d-nb.info/1238423051/34.
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Zhou, Linxiao. "Numerical Studies on Thermal-hydraulic Behaviour of CO2 Energy Piles." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/28015.
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Geothermal energy piles (GEPs), buried into the soil, are typically integrated with the circulating pipe inside the piles, where the most common heat transfer fluid (HTF) is water. However, water cannot operate under a sub-zero-degree cold environment without using the antifreeze additive. Carbon dioxide (CO2), which is newly introduced as HTF to save energy by its density difference of flow and circulation, has a more extensive operation range and can operate below zero degrees Celsius as the fluid phase.
In this study, GEPs are modelled using a finite element method (FEM) to present the fundamental thermal performance of GEPs under 10-hour daily operation time, and to evaluate the thermal performance of CO2 and H2O in the energy pile system. It is further highlighted the thermo-hydraulic influence acting in the vicinity of GEPs caused by groundwater seepage in fully saturated soil. The concept of the Ragone plot is introduced to evaluate the system, where HTF Péclet number and groundwater Péclet number are considered as the respective main variables.
Our numerical results indicated the potential of CO2 as the HTF in similar energy systems. To meet the same energy demand or acquire the same system power efficiency, CO2 GEP could respectively reach up to 4 times the power efficiency and 10 times the energy density than that of water. Moreover, the study on GEPs was extended to coupled hydrothermal analyses. An effective thermal design considering thermohydraulic interaction has the potential to increase the overall thermal performance of GEPs, especially when the groundwater Péclet number is around 1. This research contributes to energy extraction analyses of GEPs by demonstrating thermal performance on the Ragone plot. With the same cutoff efficiency, the GEP with the relatively high groundwater Péclet number could reach more than 10 times the energy density than that with deficient groundwater flow.
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Mekala, Samuel J. "CFD studies of reactive flow with thermal and mass diffusional effects in a supercritical packed bed catalytic reactor." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/461182.
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Packed bed reactors are widely used in various chemical processes. Fundamental understanding of the heat and mass transfer phenomena in the packed beds is essential for better modelling of these processes. Theoretical models used to describe the flow in packed beds generally assume an effectively homogeneous systems ignoring the complexities of flow in the void spaces of the packed beds. These details may however be influencing significantly the various phenomena in the system. To enhance this understanding, Computational Fluid Dynamics (CFD) is used to obtain detailed flow, temperature and concentration profiles in packed bed with multiple species undergoing heat and mass transfer with accompanying reaction in a heterogeneous catalytic reactor model. CFD is a simulation tool that through solving of momentum, mass and energy balances around complex geometries gives advanced view of fluid flow and transport mechanisms in the catalytic reactor.
In this thesis work, fluid flow and heat and mass transfer phenomena in packed beds is solved using CFD codes, developing a modelling strategy to design heterogeneous reaction packed bed equipment. Supercritical transesterification reaction process, for which experimental data was available from earlier experimental work was available was taken as a reference processes for simulation models. Due to the complexity of this process which involves various transport phenomena, and extreme operating conditions, each of the transfer process occurring in the packed bed is studied distinctly.
A state-of-the art and a literature review is presented for CFD applications in packed beds, supercritical fluids and transesterification reaction. The governing equations and accompanying complementary models used in the simulations are presented. Physical properties of the reaction components methanol, triolein, diglyceride, mono-glyceride, fatty acid methyl esters, and glycerol at supercritical conditions are estimated. A geometrical model of heterogeneous catalytic reactor, which is a cylindrical tube filled with cylindrical particles arranged randomly, is developed representing a laboratory pilot unit. A 120-degree segment of packed bed tube is generated and validated against a complete wall-segment bed. Mesh influence over the flow is checked for different mesh refinement and a mesh of optimal refinement, independent of the mesh is selected for further study.
As the packed bed is heated from the walls, wall-to-fluid heat transfer in packed beds is analysed, and CFD obtained results are used to review the radial flow effects in packed bed flow. The results are also related with empirical correlations analysing comparable trends.
Particle-to-fluid mass transfer in packed beds is also studied with the triolein diffusion from particles to analyse the diffusional effects in the bed. For an analogous energy transfer, particle-to-fluid heat transfer is also studied. CFD obtained results are compared against previously published experimental data/empirical correlations. Mixed (free + forced) convection in packed beds at high pressure is also studied. Numerical results obtained are presented and compared against experimental data on mass transfer for supercritical extraction.
Applicability of available reaction kinetics for transesterification reaction is studied. Packed bed models are prepared for one-step irreversible and three-step reversible reaction kinetics, for different temperatures and space-times. Numerical results are compared against experimental results, and flow, concentration and conversion profiles are obtained and analysed. Effects of the two kinetic models is studied for different temperatures and space-times.Los reactores de lecho empacado son ampliamente utilizados en diversos procesos químicos. La comprensión de los fenómenos de transferencia de calor y masa en estos equipos es esencial para una mejor modelización de sus procesos. Los modelos teóricos utilizados para describir el flujo en lechos de relleno generalmente asumen sistemas homogéneos haciendo caso omiso de las complejidades de flujo en el espacio intersticial del relleno. Estos detalles pueden sin embargo influir significativamente en los diversos fenómenos que ocurren en el sistema. La Dinámica de Fluidos Computacional (CFD) puede utilizarse para profundizar en el conocimiento de estos fenómenos obteniendo información detallada del flujo, la temperatura y la concentración de reactivos y productos en el interior del relleno, resultado de los fenómenos de transferencia de calor y masa con reacción química en un modelo de reactor catalítico heterogéneo. En este trabajo de tesis, los fenómenos de flujo y transferencia de calor y masa en lechos empaquetados se resuelve mediante códigos CFD, desarrollando una estrategia de modelado útiles para diseñar reactores de lecho empacado. Se seleccionó como referencia del modelo computacional un proceso de reacción de transesterificación supercrítica, para el que se disponía de resultados experimentales previamente obtenidos. Debido a la complejidad de este proceso que implica varios fenómenos simultáneos, y las condiciones de funcionamiento extremas del proceso seleccionado, cada uno de los fenómenos de transferencia fueron estudiados individualmente. Este trabajo incluye un estado de la técnica y revisión de la literatura para aplicaciones de CFD en lechos empacados, fluidos supercríticos y procesos de transesterificación. Se presentan las ecuaciones fundamentales y los modelos complementarios utilizados en el modelado numérico. Se estiman las propiedades físicas de reactivos y productos participantes en el proceso (metanol, trioleína, diglicérido, monoglicérido, ésteres metílicos de ácidos grasos y glicerol) en condiciones supercríticas. Se presenta un modelo geométrico de reactor catalítico heterogéneo, que es un tubo cilíndrico lleno de partículas cilíndricas dispuestas al azar, basado en el reactor la planta piloto usada en el estudio experimental previo. Se generó un modelo de 120º de la circunferencia del reactor de lecho empacado, en el cual se llevaron a cabo estudios de independencia de malla sobre los resultados. Se estudian los efectos de la transferencia calor pared-fluido, y los resultados obtenidos con CFD son utilizados para revisar los efectos de flujo radial sobre el flujo dentro del lecho empacado. Los resultados obtenidos son comparados contra correlaciones empíricas, obteniendo tendencias similares. También se estudió la transferencia de materia partícula-fluido a través de comparación contra correlaciones empíricas y análisis de la convección mixta (natural+forzada) a alta presión. La reacción de transesterificación fue implementada en el modelo computacional usando un modelo cinético de un paso y un modelo cinético de tres pasos, para diferentes temperaturas y tiempos de residencia. Los resultados son comparados con datos experimentales previamente obtenidos por el grupo de investigación.
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Bylund, Anna, and Jennie Pettersson. "Hävstångsinstrument : en lönsam investering för småsparare." Thesis, Högskolan i Gävle, Avdelningen för ekonomi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-6975.
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Syfte: Syftet med denna uppsats är att undersöka finansiella institutioners syn på hävstångsinstrument och utifrån detta utreda om instrumenten är ett bra investeringsalternativ för småsparare. Metod: Uppsatsen har en kvalitativ inriktning då tre intervjuer har genomförts för att besvara syftet. De finansiella institutionerna som intervjuades är Handelsbanken, CMC Markets och SIP Nordic fondkommission. Vidare har studien en deduktiv infallsvinkel där teorier används som grund för det empiriska materialet. Utifrån intervjuer och tidigare studier har en slutsats sedan utformats för att besvara syftet. Resultat & Slutsats: Uppsatsens resultat talar för att hävstångsinstrumenten är ett bra alternativ för småsparare som är intresserade, risktoleranta och aktivt söker kunskap. Småsparare som har dessa egenskaper och dessutom har ett bra kompletterande sparande kan därför med fördel investera i dessa instrument. För småsparare som inte har den risktolerans och kunskap som krävs för ett lyckat resultat, kan dock andra sparalternativ vara ett bättre val. Förslag till fortsatt forskning: Då resultatet av denna uppsats är baserat på finansiella institutioners syn på hävstångsinstrument, vore det intressant att utreda samma sak men att då basera det empiriska materialet på intervjuer eller enkäter med småsparare som använder instrumenten. Detta skulle i sådana fall ge forskaren svar på hur instrumenten uppfattas av småspararna själva. Uppsatsens bidrag: Tidigare forskning inom detta område finns enbart i liten utsträckning. Därmed bidrar vår studie med att öka kunskapen om hävstångsinstrument. Uppsatsen ger en bred bild av hävstångsinstrument som sparalternativ och bidrar med att ge en förståelse för vilka hävstångsinstrumenten passar till.
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West, Zachary John. "Studies of Jet Fuel Autoxidation Chemistry: Catalytic Hydroperoxide Decomposition & High Heat Flux Effects." University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1322764905.
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Pieterse, Jacobus Erasmus. "CFD investigation of the atmospheric boundary layer under different thermal stability conditions." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80024.
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Thesis (MScEng)--Stellenbosch University, 2013.ENGLISH ABSTRACT: An accurate description of the atmospheric boundary layer (ABL) is a prerequisite for computational fluid dynamic (CFD) wind studies. This includes taking into account the thermal stability of the atmosphere, which can be stable, neutral or unstable, depending on the nature of the surface fluxes of momentum and heat. The diurnal variation between stable and unstable conditions in the Namib Desert interdune was measured and quantified using the wind velocity and temperature profiles that describe the thermally stratified atmosphere, as derived by Monin- Obukhov similarity theory. The implementation of this thermally stratified atmosphere into CFD has been examined in this study by using Reynoldsaveraged Navier-Stokes (RANS) turbulence models. The maintenance of the temperature, velocity and turbulence profiles along an extensive computational domain length was required, while simultaneously allowing for full variation in pressure and density through the ideal gas law. This included the implementation of zero heat transfer from the surface, through the boundary layer, under neutral conditions so that the adiabatic lapse rate could be sustained. Buoyancy effects were included by adding weight to the fluid, leading to the emergence of the hydrostatic pressure field and the resultant density changes expected in the real atmosphere. The CFD model was validated against measured data, from literature, for the flow over a cosine hill in a wind tunnel. The standard k-ε and SST k-ω turbulence models, modified for gravity effects, represented the data most accurately. The flow over an idealised transverse dune immersed in the thermally stratified ABL was also investigated. It was found that the flow recovery was enhanced and re-attachment occurred earlier in unstable conditions, while flow recovery and re-attachment took longer in stable conditions. It was also found that flow acceleration over the crest of the dune was greater under unstable conditions. The effect of the dune on the flow higher up in the atmosphere was also felt at much higher distances for unstable conditions, through enhanced vertical velocities. Under stable conditions, vertical velocities were reduced, and the influence on the flow higher up in the atmosphere was much less than for unstable or neutral conditions. This showed that the assumption of neutral conditions could lead to an incomplete picture of the flow conditions that influence any particular case of interest.
AFRIKAANSE OPSOMMING: 'n Akkurate beskrywing van die atmosferiese grenslaag (ABL) is 'n voorvereiste vir wind studies met berekenings-vloeimeganika (CFD). Dit sluit in die inagneming van die termiese stabiliteit van die atmosfeer, wat stabiel, neutraal of onstabiel kan wees, afhangende van die aard van die oppervlak vloed van momentum en warmte. Die daaglikse variasie tussen stabiele en onstabiele toestande in die Namib Woestyn interduin is gemeet en gekwantifiseer deur gebruik te maak van die wind snelheid en temperatuur profiele wat die termies gestratifiseerde atmosfeer, soos afgelei deur Monin-Obukhov teorie, beskryf. Die implementering van hierdie termies gestratifiseerde atmosfeer in CFD is in hierdie studie aangespreek deur gebruik te maak van RANS turbulensie modelle. Die handhawing van die temperatuur, snelheid en turbulensie profiele in die lengte van 'n uitgebreide berekenings domein is nodig, en terselfdertyd moet toegelaat word vir volledige variasie in die druk en digtheid, deur die ideale gaswet. Dit sluit in die implementering van zero hitte-oordrag vanaf die grond onder neutrale toestande sodat die adiabatiese vervaltempo volgehou kan word. Drykrag effekte is ingesluit deur die toevoeging van gewig na die vloeistof, wat lei tot die ontwikkeling van die hidrostatiese druk veld, en die gevolglike digtheid veranderinge, wat in die werklike atmosfeer verwag word. Die CFD-model is gevalideer teen gemete data, vanaf die literatuur, vir die vloei oor 'n kosinus heuwel in 'n windtonnel. Die standaard k-ε en SST k-ω turbulensie modelle, met veranderinge vir swaartekrag effekte, het die data mees akkuraat voorgestel. Die vloei oor 'n geïdealiseerde transversale duin gedompel in die termies gestratifiseerde ABL is ook ondersoek. Daar is bevind dat die vloei herstel is versterk en terug-aanhegging het vroeër plaasgevind in onstabiele toestande, terwyl vloei herstel en terug-aanhegging langer gevat het in stabiele toestande. Daar is ook bevind dat vloei versnelling oor die kruin van die duin groter was onder onstabiele toestande. Die effek van die duin op die vloei hoër op in die atmosfeer is ook op hoër afstande onder onstabiele toestande gevoel, deur middel van verhoogte vertikale snelhede. Onder stabiele toestande, is vertikale snelhede verminder, en die invloed op die vloei hoër op in die atmosfeer was veel minder as vir onstabiel of neutrale toestande. Dit het getoon dat die aanname van neutrale toestande kan lei tot 'n onvolledige beeld van die vloei toestande wat 'n invloed op 'n bepaalde geval kan hê.
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Campioli, Theresa Lynn. "Computational Studies of Penetration and Mixing for Complex Jet Injectors to Aid in Design of Hypersonic Systems." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28132.
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A computational study of sonic light-gas jet injection into a supersonic cross flow was conducted. The scope of the numerical analysis encompassed many studies that affect how the flow-field is numerically modeled and the behavior, specifically mixing, of the flow-field itself. A single, round injector was used for the Baseline design. Simulated conditions involved sonic injection of helium heated to 313 K into a Mach 4 air cross-stream with average Reynolds number 5.77 e+7 per meter and a freestream momentum flux ratio of 2.1. Experiments at these conditions were available for comparison. The primary numerical flow solver employed was GASP v. 4.2. The Menter Shear Stress Transport (SST) turbulence model was used, since the algorithm has good capability of solving both wall-bounded and free-shear flows. The SST model was able to capture the mixing behavior of the complex flow-field. Important numerical parameters that affect the capabilities of the numerical solver were studied for the Baseline injector. These sensitivity studies varied the choice of turbulent Prandtl number, Schmidt number, freestream turbulence intensity, boundary layer size, steady and unsteady approaches and computational software packages. A decrease in the turbulent Prandtl number resulted in better mixing behavior of the prediction and better agreement with the experiment. An increase in the turbulent Schmidt number had a small adverse effect on the predictions. The mixing characteristics remained constant with an increase in freestream turbulence intensity. The best Baseline prediction was then compared to three different injector configurations: an aerodynamic ramp consisting of four injectors in an array, a diamond injector both aligned and yawed 15° to the oncoming flow. The Computational Fluid Dynamics (CFD) tools were more accurate compared to experiment in the prediction of the aeroramp injector than the diamond-shaped injectors. The aeroramp injector slightly improved mixing efficiency over the Baseline injector at these conditions. Both of the diamond-shaped injectors had similar mixing as the Baseline injector but did not predict significant improvement in penetration for the analyzed conditions. Additional studies involving the interaction of transverse injection with impinging oblique shock waves were performed. The impingement of a shock upon light gas jet injection increased mixing. The closer the shock is to the injection point, the larger the effect on mixing and vorticity. The last analyses involved a numerical comparison of a non-reacting model to a reacting hydrogen-air model. The reacting analysis prediction had an improved spreading rate and larger counter-rotating vortex pair with downstream distance over the non-reacting analysis. The mixing was not significantly altered by the addition of hydrogen-air reactions to the numerical equations. The numerical tools used are capable of reasonable accuracy in predicting the complex flow-field of jet injection into a supersonic freestream with proper choice of models and parameters. Numerical modeling offers a way to study the entire flow-field thoroughly in a cost and time efficient manner.Ph. D.
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Nijemeisland, Michiel. "Verification Studies of Computational Fluid Dynamics in Fixed Bed Heat Transfer." Digital WPI, 2000. https://digitalcommons.wpi.edu/etd-theses/318.
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Computational Fluid Dynamics (CFD) is one of the fields that has strongly developed since the recent development of faster computers and numerical modeling. CFD is also finding its way into chemical engineering on several levels. We have used CFD for detailed modeling of heat and mass transfer in a packed bed. One of the major questions in CFD modeling is whether the computer model describes reality well enough to consider it a reasonable alternative to data collection. For this assumption a validation of CFD data against experimental data is desired. We have developed a low tube to particle, structured model for this purpose. Data was gathered both with an experimental setup and with an identical CFD model. These data sets were then compared to validate the CFD results. Several aspects in creating the model and acquiring the data were emphasized. The final result in the simulation is dependent on mesh density (model detail) and iteration parameters. The iteration parameters were kept constant so they would not influence the method of solution. The model detail was investigated and optimized, too much detail delays the simulation unnecessarily and too little detail will distort the solution. The amount of data produced by the CFD simulations is enormous and needs to be reduced for interpretation. The method of data reduction was largely influenced by the experimental method. Data from the CFD simulations was compared to experimental data through radial temperature profiles in the gas phase collected directly above the packed bed. It was found that the CFD data and the experimental data show quantitatively as well as qualitatively comparable temperature profiles, with the used model detail. With several systematic variances explained CFD has shown to be an ample modeling tool for heat and mass transfer in low tube to particle (N) packed beds.
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Alsharif, Aesam. "Development and computational studies of multi-channel adsorbent hollow fibre for the removal of volatile organic compounds." Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760926.
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Escalating energy and environmental issues are driving researchers and industries throughout the world to study gas separation. Being common toxic gases, volatile organic compounds (VOCs) must be removed from the atmosphere. When compared to the conventional adsorption process, e.g. packed bed to separate VOC, the adsorbent hollow fibre has exhibited advantages in low-pressure drop, easy operation and lower capital cost with high adsorption performance. This research investigates the optimisation and development of single and multi-channel adsorbent hollow fibres to improve the mechanical properties, flexibility, adsorbent loading and enhance adsorption capacity. These fibres are made up of an adsorbent (13X zeolite, HiSiv 1000 zeolite powder and HiSiv 3000 zeolite powder) held together with a polymer (polyethersulfone) binder through wet/wet spinning followed by a phase inversion process. Single adsorbent hollow fibres were optimised by changing the ratio of adsorbent to the polymer, the viscosity of polymer/adsorbent/solvent mixtures, the pre-treatment temperature and by adding a pore former. This optimal recipe of polymer/adsorbent/solvent mixtures was then used to fabricate tri-lobe and hexagonal multi-channel adsorbent hollow fibre. The adsorption performance and mechanical properties of these multi-channel fibres were compared to those of the single adsorbent hollow fibres. Dynamic adsorption challenges were carried out using n-butane as the VOC model gas to provide breakthrough curves using a flame ionisation detector (FID) hydrocarbon analyser. Scanning electron microscopy (SEM) was used to characterise the surface and porous structures of the different adsorbent hollow fibres formation. Adsorption isotherm experiments were also used to measure the surface area of adsorbent hollow fibres. In order to understand the transport mechanism of gases through adsorbent hollow fibres, single and multi-channel fibres were modelled using a computational fluid dynamics (CFD) using COMSOL software 5.2, thus enabling the prediction of breakthrough time and mass transfer for the new geometries of adsorbent hollow fibre.
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Xue, Song. "Fan-Shaped Hole Film Cooling on Turbine Blade and Vane in a Transonic Cascade with High Freestream Turbulence: Experimental and CFD Studies." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/77979.
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The contribution of present research work is to experimentally investigate the effects of blowing ratio and mainstream Mach number/Reynolds number (from 0.6/8.5X10⁵ to 1.0/1.4X10⁶) on the performance of the fan-shaped hole injected turbine blade and vane. The study was operated with high freestream turbulence intensity (12% at the inlet) and large turbulence length scales (0.26 for blade, 0.28 for vane, normalized by the cascade pitch of 58.4mm and 83.3mm respectively). Both convective heat transfer coefficient, in terms of Nusselt number, and adiabatic effectiveness are provided in the results.
Present research work also numerically investigates the shock/film cooling interaction. A detailed analysis on the physics of the shock/film cooling interaction in the blade cascade is provided.
The results of present research suggests the following major conclusions. Compared to the showerhead only vane, the addition of fan-shaped hole injection on the turbine Nozzle Guide Vane (NGV) increases the Net Heat Flux Reduction (NHFR) 2.6 times while consuming 1.6 times more coolant. For the blade, combined with the surface curvature effect, the increase of Mach number/Reynolds number results in an improved film cooling effectiveness on the blade suction side, but a compromised cooling performance on the blade pressure side. A quick drop of cooling effectiveness occurs at the shock impingement on the blade suction side near the trailing edge. The CFD results indicate that this adiabatic effectiveness drop was caused by the strong secondary flow after shock impingement, which lifts coolant away from the SS surface, and increases the mixing. This secondary flow is related to the spanwise non-uniform of the shock impingement.Ph. D.
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Shirai, Haruhiko. "Studies on energy harvesting using vibration in natural environment with magnetic powder." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263779.
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Chiti, Fabio. "Lagrangian studies of turbulent mixing in a vessel agitated by a Rushton turbine : positron emission particle tracking (PEPT) and computational fluid dynamics (CFD)." Thesis, University of Birmingham, 2008. http://etheses.bham.ac.uk//id/eprint/1607/.
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Stirred vessels are used in a wide variety of process industries such as fine chemicals, pharmaceuticals, polymers and foods. In order to design efficient mixing vessels, a deep understanding of the blending processes is required. In cases where the fluid is not completely transparent, traditional optical laser based techniques are ineffective. One of the most promising techniques to study opaque systems is based on the detection of a tracer that emits gamma rays. Positron Emission Particle Tracking (PEPT) has been developed at the University of Birmingham and has been used in a wide range of applications including stirred tanks. However, for agitated vessels, any attempt of validation of the PEPT technique versus other techniques cannot be found. Hence, this work aims to validate and explore the potential of Lagrangian data in a well known mixing system such as a standard baffled vessel stirred by a Rushton turbine. As part of the validation, comparison with Eulerian PIV/LDA data has been also undertaken and some underestimation of the high velocities in the system was found in the impeller region. By using a selective interpolation algorithm of the tracer locations, this problem was greatly reduced although a perfect match with optical technique is not feasible. As further contribution to Lagrangian studies of mixing processes, Computational Fluid Dynamics (CFD) simulations have been undertaken to give both Eulerian and Lagrangian velocities and particle paths. However, it has been shown that traditional approaches to Lagrangian numerical simulation are unable to produce good trajectories that can be compared to experimental data. A novel three-step approach was suggested and implemented in order to achieve good paths, which then have been compared to the experimental trajectories. Qualitative and quantitative analysis of experimental Lagrangian data showed that the trajectories are erratic and follow random paths; furthermore, frequency analysis applied to portions of trajectories does not reveal any dominant low frequency in the system. Finally, circulation studies were undertaken in order to characterise mixing processes. This focused on tracking the tracer every time it leaves and returns a control volume proving the value of analysing time and return length distributions, since it was possible to compare the circulation times achieved in PEPT with published work. The trajectography approach used in this work is the first attempt at using trajectories from PEPT as a tool to characterise mixing performance rather than only using the data to find Eulerian velocities and vector plots.
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Jiang, Zhaochen [Verfasser], Evangelos [Gutachter] Tsotsas, and Dominique [Gutachter] Thévenin. "Experimental and simulation studies of mesoscale phenomena in gas-solid fluidized beds PTV and CFD-DEM / Zhaochen Jiang ; Gutachter: Evangelos Tsotsas, Dominique Thévenin." Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2020. http://d-nb.info/1219937827/34.
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Jiang, Zhaochen Verfasser], Evangelos [Gutachter] [Tsotsas, and Dominique [Gutachter] Thévenin. "Experimental and simulation studies of mesoscale phenomena in gas-solid fluidized beds PTV and CFD-DEM / Zhaochen Jiang ; Gutachter: Evangelos Tsotsas, Dominique Thévenin." Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2020. http://d-nb.info/1219937827/34.
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Fimbres, Weihs Gustavo Adolfo UNESCO Centre for Membrane Science & Technology Faculty of Engineering UNSW. "Numerical simulation studies of mass transfer under steady and unsteady fluid flow in two- and three-dimensional spacer-filled channels." Publisher:University of New South Wales. UNESCO Centre for Membrane Science & Technology, 2008. http://handle.unsw.edu.au/1959.4/41453.
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Hollow fibre and spiral wound membrane (SWM) modules are the most common commercially available membrane modules. The latter dominate especially for RO, NF and UF and are the focus of this study. The main difficulty these types of modules face is concentration polarisation. In SWM modules, the spacer meshes that keep the membrane leaves apart also help reduce the effects of concentration polarisation. The spacer filaments act as flow obstructions, and thus encourage flow destabilisation and increase mass transfer enhancement. One of the detrimental aspects of the use of spacers is an increase of pressure losses in SWM modules. This study analyses the mechanisms that give rise to mass transfer enhancement in narrow spacer-filled channels, and investigates the relationship between flow destabilisation, energy losses and mass transfer. It shows that the regions of high mass transfer on the membrane surface correlate mainly with those regions where the fluid flow is towards the membrane. Based on the insights gained from this analysis, a series of multi-layer spacer designs are proposed and evaluated. In this thesis, a Computational Fluid Dynamics (CFD) model was used to simulate steady and unsteady flows with mass transfer in two- and three-dimensional narrow channels containing spacers. A solute with a Schmidt number of 600 dissolving from the wall and channel Reynolds numbers up to 1683 were considered. A fully-developed concentration profile boundary condition was utilised in order to reduce the computational costs of the simulations. Time averaging and Fourier analysis were performed to gain insight into the dynamics of the different flow regimes encountered, ranging from steady flow to vortex shedding behind the spacer filaments. The relationships between 3D flow effects, vortical flow, pressure drop and mass transfer enhancement were explored. Greater mass transfer enhancement was found for the 3D geometries modelled, when compared with 2D geometries, due to wall shear perpendicular to the bulk flow and streamwise vortices. Form drag was identified as the main component of energy loss for the flow conditions analysed. Implications for the design of improved spacer meshes, such as extra layers of spacer filaments to direct the bulk flow towards the membrane walls, and filament profiles to reduce form drag are discussed.
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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.
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Yossefi, Danny. "Early stages of combustion development in internal combustion engines using linked CFD and chemical kinetics computations : illustrated by studies of a natural gas burning engine." Thesis, University of Exeter, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296284.
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Tridas, Eric Miguel. "Experimental and Numerical Investigation of an Electrospray RF Ion Funnel." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4243.
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Using experimental techniques along with computational fluid dynamics and electrodynamic simulations the performance of the first of three focusing elements in an electrospray macromolecular patterning system was assessed. The performance of this element, the ion funnel, was analyzed by varying the parameters and electric field applied to the system including electrospray emitter to atmosphere-vacuum interface capillary distance, temperature of the desolvating heater, injection rate of solution and the voltage applied to the jet disruption element. Results indicated that processes involved in injecting larger droplets into the chamber resulted in a less effective transmission of the ions through the funnel. Droplet diameter was increased by increasing flow rate and was decreased by increasing the desolvation heater. Varying the voltage applied to the jet disrupting element indicated a peak transmission voltage, when using a 20 mil interface capillary,of 175 V and when using the 30 mil capillary of 180 V. Numerical simulations were in agreement with these values although the widths of these transmission curves were much narrower than the experimental curves.
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Rodríguez, Pérez Ivette. "Unsteady laminar convection in cylindrical domains: numerical studies and application to solar water storage tanks." Doctoral thesis, Universitat Politècnica de Catalunya, 2006. http://hdl.handle.net/10803/6689.
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Los dispositivos de almacenamiento de energía térmica son ampliamente usados en diversos sistemas térmicos caracterizados por un desfase temporal entre la producción de energia y su consumo, como es el caso de los sistemas de energía solar térmica. El diseño optimizado de estos equipos puede representar un considerable aumento en el rendimiento térmico de la instalación de la cual forman parte. En la línea de optimización de sistemas y equipos térmicos, en los últimos años la Mecánica de Fluidos Computacional (CFD) se ha consolidado como una herramienta básica, proporcionando a investigadores e ingenieros un método para ensayar virtualmente sus diseños, disminuyendo los costes en términos de tiempo, recursos y personal. Es en esta línea se encuentran las principales aportaciones de esta tesis, la cual tiene como principal objetivo la simulación numérica de procesos de convección laminar en régimen transitorio y dominios cilíndricos para su aplicación al estudio de los fenómenos de transferencia de calor y dinámica de fluidos que tienen lugar en los tanques de almacenamiento de energía.Se presenta la metodología seguida para la resolución de las ecuaciones gobernantes de la transferencia de calor y dinámica de fluidos en coordenadas cilíndricas, mostrando las principales particularidades de su discretización para este tipo de geometrías y se detalla el tratamiento realizado para resolver estas singularidades dentro del código numérico. Posteriormente, se expone la metodología para la solución de flujos transitorios e incompresibles y se realiza un riguroso proceso de verificación del código y las soluciones numéricas obtenidas.
Esta metodología se aplica al estudio del comportamiento de los tanques de almacenamiento de energía estratificados. Un aspecto básico del funcionamiento de estos equipos es la calidad de la energía almacenada. Esta calidad viene determinada por el grado de estratificación térmica, en la cual influyen diferentes factores como la mezcla que ocurre debido a las corrientes de fluido que entran durante los procesos de carga y descarga térmica y también debido al intercambio de calor con el ambiente. En este sentido, en este trabajo se analiza la estratificación térmica para diferentes condiciones de trabajo y configuraciones por medio de las simulaciones numéricas multidimensionales. Para medir el grado de estratificación se han tenido en cuenta diferentes parámetros y como resultado del estudio, se propone un parámetro adimensional basado en un análisis exergético. Esta exergía adimensional ha permitido comparar el funcionamiento de los tanques en las diferentes situaciones analizadas y se ha mostrado útil para cuantificar la calidad de la energía almacenada.
Por otra parte, se estudia el comportamiento térmico de los tanques de almacenamiento durante su modo de operación estático y considerando las pérdidas de energía al ambiente. Este estudio tiene como objetivo fundamental caracterizar el proceso de enfriamiento del fluido en tanques que forman parte de sistemas solares térmicos para el rango de bajas y medianas temperaturas. Se presenta la metodología seguida para el análisis, desde la identificación de los números adimensionales que definen el problema, la formulación de un modelo zonal para la predicción del comportamiento térmico, el estudio paramétrico llevado a cabo y el posterior post-proceso de los resultados con el objetivo de proporcionar los parámetros necesarios para alimentar el modelo zonal. El modelo propuesto, junto con las correlaciones obtenidas, predicen correctamente el comportamiento del fluido, constituyendo una alternativa interesante para reproducir el proceso de enfriamiento del fluido en los tanques durante largos periodos de tiempo.
Thermal storage devices are widely used in many thermal systems and applications that are characterised by the delay between energy production and consumption, such as thermal solar systems. The improvement in their design and optimisation is a key aspect in the thermal optimisation of the system, where a good preformance of the storage tank can represent a considerable increase in the overall efficiency of the installation. In the subject of optimisation of thermal equipment, Computational Fluid Dynamics have been consolidated as an indispensable tool providing researchers and engineers with a method to test virtually their prototypes with low effort in time, personnel and resources. This thesis is focused in the numerical simulation of unsteady laminar convection in cylindrical domains and its application to the study of the heat transfer and fluid flow that take place in stratified storage tanks.
The first part of this document is devoted to present the methodology followed for the numerical resolution of the governing equation of heat and fluid flow in cylindrical coordinates. The main particularities of the discretisation of the equations in these geometries, as well as the solution procedure for incompressible and transient flow problems are also presented. Special emphasis is given to the verification of the code, the appropriateness of the discretisation adopted and the verification of the numerical solution obtained.
The second part of this thesis is focused on the study of the heat transfer and fluid flow phenomena that take place in stratified storage tanks, including the performance measures and modeling efforts of these devices. The quality of the energy stored is determined by the degree of the thermal stratification of the storage tank, which is affected by several factors such as the mixing due to the inlet streams during load and unload, the heat losses to the environment, among others. In this sense, thermal stratification analysis is carried out by means of the virtual prototyping of the tanks for different working conditions and configurations. In order to measure the performance of the tanks, different parameters are considered. The analysis led to the proposition of a new exergy-based parameter as a tool for assessing and comparing storage tanks. The usefulness of this parameter for quantifying the quality of the energy stored is also shown.
Furthermore, the thermal behaviour of storage tanks during the static mode of operation considering the heat losses to the environment is also analysed. The study is addressed to characterise the cool down of the fluid inside storage tanks for solar thermal systems in the low-to-medium temperature range. The methodology followed, from the identification of the significant non-dimensional parameters that define the problem, the formulation of a zonal prediction model, a parametric numerical study by means of detailed multidimensional CFD computations and the post-processing of the results in order to feed the global model are exposed in detail. Zonal model presented, together with the correlations given are in good agreement with the numerical results and constitute an alternative for the prediction of the long-term performance of the storage tanks during the cooling process.
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Barbouche, Naziha. "Réponse biologique de cellules animales à des contraintes hydrodynamiques : simulation numérique, expérimentation et modélisation en bioréacteurs de laboratoire." Thesis, Vandoeuvre-les-Nancy, INPL, 2008. http://www.theses.fr/2008INPL075N/document.
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La réponse globale de cellules animales à des contraintes hydrodynamiques lors de leur culture en suspension dans des réacteurs agités a été étudiée grâce à une approche intégrative couplant les outils du génie biochimique à ceux de la mécanique des fluides numérique. En premier lieu, la description de l’hydrodynamique moyenne et locale de deux systèmes de culture agités de laboratoire, spinner et bioréacteur, a été réalisée. Puis, l'étude des cinétiques macroscopiques de cellules CHO cultivées en suspension, en milieu sans sérum et sans protéine, a été réalisée avec différentes vitesses d’agitation, pour évaluer l'impact de l'agitation sur les vitesses de croissance et de mort cellulaires, ainsi que de consommation des substrats et de production des métabolites et de l'interféron-gamma recombinant. Des caractérisations supplémentaires des cellules (apoptose, protéines intracellulaires) et de l'interféron ont également été réalisées. Les effets de l'intensification de l'agitation ont été représentés avec plusieurs corrélations globales reliant : (i) en milieu contenant du pluronic, l'intégrale des cellules viables au nombre de Reynolds, et la proportion de cellules lysées à la valeur moyenne de l'énergie de dissipation, <[epsilon]? (ii) en milieu sans pluronic, les vitesses spécifiques de croissance et de mort cellulaires à <[epsilon]. De plus, l'analyse par CFD de la distribution spatio-temporelle des contraintes indique que la lyse cellulaire, observée dans le réacteur aux conditions extrêmes d'agitation, serait plutôt liée à des valeurs locales très élevées de [epsilon], ainsi qu’à la fréquence d'exposition des cellules dans ces zones énergétiques. Un modèle hydro-cinétique original, couplant l’hydrodynamique locale aux cinétiques cellulaires de croissance et de mort, et basé sur l’intermittence de la turbulence permet la prédiction de la lyse massive observée en réacteur sous certaines conditions. Pour confirmer le fait que les effets liés à l'intensification de l'agitation sont bien le résultat d'une augmentation des contraintes hydrodynamiques, et non d'une amélioration du transfert d'oxygène, ce dernier a été mesuré et modélisé par couplage avec une simulation numérique de type Volume Of Fluid , concluant en une absence de limitation d'oxygène. Enfin, la conception, le dimensionnement et la caractérisation hydrodynamique d'un réacteur innovant de type Couette-Taylor, sont proposées pour la mise en œuvre de cultures perfusées dans un environnement hydrodynamique mieux contrôléThe global response of animal cells to hydrodynamic stress when cultivated in suspension in stirred tank reactors was studied. To do this, an integrative approach coupling biochemical engineering and fluid mechanics tools were used. First, the description of the global and local hydrodynamics of two bench-scale agitated reactors, a spinner flask and a bioreactor, was carried out. Then, macroscopic kinetics of CHO cells cultivated in a serum and protein-free medium were obtained at various agitation rates, in order to evaluate the impact of agitation on cellular growth and death, as well as substrates consumption and metabolites and recombining IFN-[gamma] production. IFN-[gamma] and cells physiological state were more precisely characterised by glycosylation, apoptosis state and intracellular proteins measurements. The effects of the agitation increase were represented by several global correlations that related: (i) in a medium containing Pluronic F68, the Integral of the Viable Cells Density to the Reynolds number, and the proportion of lysed cells with the average value of energy dissipation rate <[epsilon]? (ii) in a medium without pluronic, specific cell growth and death rates to <[epsilon]. Moreover, CFD analysis of the stress distribution indicated that the cellular lysis observed in the bioreactor at the highest agitation rate, would be related to very high local values of [epsilon], and to the exposure frequency of the cells in these energetic zones. An original hydro-kinetic model based on the intermittency of turbulence and coupling the local hydrodynamics with cell growth and death kinetics, allowed the prediction of the massive cell lysis observed in the bioreactor under some mixing conditions. To decouple shear stress effects from oxygen transfer improvement, the oxygen transfer coefficient was experimentally measured and modelled using a Volume Of Fluid numerical simulation. Our results indicated the absence of an oxygen limitation, which confirmed that this cell response resulted from the hydrodynamic stress increase alone. Lastly, an innovative continuous and perfused Couette-Taylor reactor, allowing a better-controlled hydrodynamic environment was designed and sized. Its hydrodynamic description was carried out using CFD calculations
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Torre, J. P. "QUENCHING RUNAWAY REACTIONS: HYDRODYNAMICS AND JET INJECTION STUDIES FOR AGITATED REACTORS WITH A DEFORMED FREE-SURFACE." Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2007. http://tel.archives-ouvertes.fr/tel-00565878.
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Pour stopper un emballement thermique dans un réacteur chimique, un moyen efficace consiste à introduire une faible quantité d'un inhibiteur liquide appelé « killer » dans la cuve agitée. Tout au long de cette thèse, l'approche expérimentale a été fortement couplée à la modélisation numérique par Computational Fluid Dynamics (CFD). La première partie du manuscrit porte sur l'hydrodynamique des réacteurs partiellement chicanés incluant la prise en compte du vortex central qui se forme à leur surface. L'utilisation d'une approche numérique multiphasique, non-homogène a permis de modéliser la déformation de la surface-libre, et la faisabilité de cette méthode innovante a été démontrée par un très bon accord entre prédictions numériques et données expérimentales. Dans une deuxième partie, l'introduction d'un jet de liquide sur la surface libre a été couplée à l'hydrodynamique du réacteur. Les résultats numériques, obtenus avec une approche Eulerienne-Lagrangienne, ont également montré un bon accord avec les données expérimentales. Ces résultats ont permis de modéliser la trajectoire du jet, de quantifier sa pénétration dans la cuve agitée, et de définir de nouveaux critères de mélange. Enfin, les méthodes numériques validées à l'échelle pilote ont été étendues à l'échelle industrielle et ont permis de proposer des améliorations concrètes pour une meilleure sécurité des réacteurs industriels étudiés.
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Sušovský, Martin. "Parametrická studie výměníku tepla pomocí CFD." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417779.
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In this paper is carried out basic design and calculation of tube heat exchanger with a straight tube bundle with installed systém of disk and doughnut baffles. The calculation included pressure losses and heat transfer coefficient of tubular space and shell side. Then CFD model was made for parametric study, which was focused on influence of change of the baffles geometry on the heat output of the exchanger and the pressure loses on the shell side.
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Fadel, Mariam. "Designing a new electrochemical cell for the study of enzyme that reduces CO2." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0491.
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Le monoxyde de carbone déshydrogénase (CODH) catalyse la réduction réversible du dioxyde de carbone par son site actif. En utilisant une méthode électrochimique appelée voltammétrie de film protéique, nous étudions le mécanisme enzymatique de CODH en immobilisant l'enzyme à une surface d'électrode de graphite où le transfert direct d'électrons est possible. Traditionnellement, pour empêcher la déplétion du substrat à l'électrode, les électrochimistes utilisent des électrodes tournantes (RDE). Cependant, comme la CODH est très active, même la RDE ne peut pas empêcher l'épuisement, ce qui masque les caractéristiques cinétiques importantes de l’enzyme. Nous ne pouvons pas résoudre le problème avec RDE, puisque nous l’utilisons déjà à la vitesse maximum. Par conséquent, nous devons concevoir une nouvelle cellule électrochimique. Pour cela, nous avons utilisé des simulations de dynamique des fluides computationnelles pour explorer diverses géométries afin d'en trouver une appropriée. Nous avons commencé par valider notre méthode numérique avec la solution théorique bien définie de la cellule réelle de RDE. Après la bonne validation, nous avons déterminé les vitesses de transport de masse au sein de plusieurs géométries et à basé sur l'optimisation des paramètres géométriques, nous avons atteint notre conception appropriée. Ce nouveau prototype a une électrode graphite uniformément accessible avec un taux de transport trois fois plus rapide que le RDE à des vitesses de solution acceptables. Nous avons construit, mis en place avec succès le système pour caractériser ses performances de transport, et trouvé un excellent accord entre les résultats numériques et expérimentauxCarbon monoxide dehydrogenase (CODH) catalyzes the reversible reduction of carbon dioxide by its active site. Thus, CODH participates in the first step of fuel production. Using an electrochemical method called protein film voltammetry, we study the enzymatic mechanism of CODH by immobilizing the enzyme at a graphite electrode surface where direct electron transfer is possible. Traditionally, to prevent depletion of the substrate at the electrode, electrochemists use rotating electrodes (RDE). However, since CODH is very active, even RDE cannot prevent depletion, which masks the important kinetic characteristics of the enzyme and complicates the analysis of the enzymatic response.We cannot solve the problem with RDE, since we already use it at maximum speed. Therefore, we must completely change our approach and design a new electrochemical cell. For this, we used computational fluid dynamics (CFD) simulations to explore various geometries to find a suitable one. We began by validating our numerical method with the well-defined theoretical solution of the real cell of RDE. After good validation, we determined the mass transport velocities within several proposed geometries of the flow cell of hydrodynamic channel and jet electrodes. Based on the optimization of geometric parameters, we have achieved our proper design of jet electrode. This new prototype has a uniformly accessible graphite electrode with a transport rate three times faster than the RDE at acceptable solution speeds. We have successfully built and implemented the system to characterize its transport performance. We found an excellent agreement between the numerical and experimental results
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Torré, Jean-Philippe. "Quenching runaway reactions : hydrodynamics and jet injection studies for agitated reactors with a deformed free-surface." Phd thesis, Toulouse, INPT, 2007. http://oatao.univ-toulouse.fr/7658/1/torre.pdf.
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To quench a thermal runaway reaction in a chemical rector, an efficient approach is the introduction of a small quantity of a liquid inhibiting agent, named a “killer”, into the mixing vessel. In this thesis, an experimental approach has been coupled tightly with numerical modelling using Computational Fluid Dynamics (CFD). The first part of this thesis is devoted to a study of the hydrodynamics of partially-baffled mixing vessels, including the free-surface deformation caused by the central vortex. The use of an inhomogeneous, multiphase approach allowed simulation of the free-surface deformation. The capability of this novel method was demonstrated by very good agreement between the numerical predictions and experimental data. In the second part, liquid jet injection at the free-surface was coupled with the vessel hydrodynamics. Numerical results, obtained using an Eulerian-Lagrangian approach, have again shown good agreement with experimental data. These results allowed the jet trajectory to be modelled and its penetration into the agitated vessel was quantified. New mixing criteria were introduced that are specific to this application. Finally, the numerical methods validated at the pilot scale were applied at the industrial scale and allowed the proposal of practical improvements to the safety of the synthesis reactors studied
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Sander, Zachary Hugo. "Heat Transfer, Fluid Dynamics, and Autoxidation Studies in the Jet Fuel Thermal Oxidation Tester (JFTOT)." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1355367856.
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Zhou, Chun. "CHEMICAL DURABILITY STUDIES OF IONOMERS AND MODEL COMPOUNDS FOR FUEL CELL APPLICATIONS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1199478916.
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Mück, Wolfgang. "Studies on the AdS/CFT correspondence." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0025/NQ51904.pdf.
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Dahlby, Mikael, and Sjöberg Robin Gustafson. "Studie av ventilation i simhall : Med fokus på klorbaserade luftföroreningar." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-12786.
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Allmänna bad bidrar i hög grad till att främja allmänhetens hälsa och välbefinnande. De erbjuder möjlighet till motion och rekreation för människor i alla åldrar. För att badgäster ska trivas och må bra krävs det att vatten- och luftkvalitet håller hög nivå. I syfte att förhindra spridning av sjukdomsalstrande organismer mellan badgäster används klor som en central komponent för att desinficera vattnet. Kloret lämnar dock restprodukter efter sig, främst trikloramin som påverkar människors hälsa negativt. Trikloramin samlas över vattenytan och stannar kvar i andningszonen om inte föroreningarna transporteras bort via luftrörelser. I Nolhaga simhall sker fram till 2018 en ombyggnad av anläggningen. Rapporten berör den nya ventilationslösning som kommer att användas till motionsbassängen. För att studera hur denna lösning fungerar och hur god luftväxling den skapar över vattenytan har en modell av simhallen skapats i CAD-program. Luftflöden har sedan simulerats i en förenklad CFD modellen och jämförts med ett röktest i en liknande simhall. Utöver den lösning som är tänkt att byggas har ett alternativ med kompletterande frånluftsdon i golvnivå simulerats. Resultatet indikerar att lufthastigheter över vattenytan ligger inom de rekommendationer som finns angivna. Luften har en tendens att röra sig i lokalen med ett återcirkulerande beteende där tilluften följer taket in i hallen för att sedan gå ner vid bakre väggen och tillbaka över vattenytan. Luftrörelserna följer detta beteende oberoende om frånluftsdonet är placerat i golv- eller taknivå. Någon skillnad i mängd bortfört trikloramin kan inte säkerställas med de metoder som använts i rapporten. Röktestet gav inte ett tillräckligt tydligt resultat för att några kopplingar till simulering ska kunna göras. Brist på tid, förkunskaper och erfarenhet inom området gör att osäkerheten kring de resultat som nåtts är stor. Mer arbete inom CFD och badhusventilation krävs för att öka trovärdigheten.
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Brännlund, Ann. "Flödessimuleringar av utskov för smoltutvandring : En studie av nedströmspassage vid Sikfors vattenkraftverk." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-85427.
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År 2004 infördes EU:s ramdirektiv för vatten i svensk lagstiftning vilket har inneburit att vattendragets funktion som vandringsväg för fisk behöver upprätthållas eller säkras, även efter att dammar byggts. För vattenkraftverksdammar kan detta ske genom att dammarna rivs eller förses med olika typer av anordningar för passage upp- och nedströms dammen. Vid Sikfors vattenkraftverk finns en ledarm för att leda smolten till ett utskov för passage nedströms dammen. Studier har dock visat att smolten dör i för stor utsträckning vid passage via utskovet, och projektets syfte har därför varit att ta fram en modell för flödet över utskovet. Modellen har ställts upp för tre volymflöden, 18, 30 och 59 m3/s och vattendjup, vattenhastighet och flödesbeteende har analyserats för volymflödena. Geometrin en bit uppströms dammen, luckan och skibordet byggdes upp i Designmodeler utifrån ritningar. För att underlätta simuleringarna delades geometrin i två delar, där den första delen innefattar geometrin en bit uppströms dammen samt luckan medan den andra geometrin innefattar skibord och uppkastare och nedslagsplats. Simuleringen gjordes i ANSYS CFX och vattenytan modellerades som en fri yta med luft och vatten som fluider i modellen. Luckans öppning varierades med volymflödet, utifrån data från vattenkraftverket. Det lägsta vattendjupet över luckan blev 5 cm vid slutet av luckan för ett volymflöde på 18 m3/s, medan för 30 m3/s blev det lägsta vattendjupet 10 cm vid slutet av luckan. Den högsta vattenhastigheten över luckan blev 8,5 m/s för 30 m3/s i mitten av luckan medan samma hastighet blev 8,3 och 8,9 m/s för volymflöde på 18 respektive 59 m3/s. För skibordet blev det lägsta vattendjupet 15 cm och 30 cm för 18 respektive 30 m3/s. Vattenhastigheten för samtliga volymflöden för skibordet överstiger 12 m/s, vilket är den högsta rekommenderade hastigheten för nedströmspassage. För 30 och 59 m3/s kastas vattnet över ingången till fisktrappan, medan för 18 m3/s påverkas flödet vid ingången utav flödet från utskovet. Vattendjupet för 30 m3/s borde vara tillräckligt för att smolten inte ska få skrapskador, medan 18 m3/s kan vara för lågt volymflöde. Ingen tendens för virvlar eller turbulens syns för luckan eller skibordet för något volymflöde, så flödesbeteendet borde inte vara ett problem för smolten. Vattenhastigheten för skibordet överskrider den högsta rekommenderade hastigheten, men hastigheten är inte mycket högre än rekommenderat och under en kort period, så det borde inte vara den enskilda orsaken till smoltens låga överlevnadsgrad. Den numeriska modellen har ställts upp för tre volymflöden, och kontrollerats mot teoretiska beräkningar och mot parametrar för meshkvalitet, som visar att modellen är bra uppställd. Analysen har visat att vattendjup och vattenhastighet är beroende av volymflödet över utskovet, och att skillnaden är större för vattendjupet. Flödesbeteendet visar ingen tendens till turbulens eller virvlar, och flödesbeteendet följer ett typiskt beteende för kanalströmning.
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Bäckström, Markus. "Utbildning för hållbar utveckling på CFL : Studenten som betydande miljöaspekt." Thesis, Linköping University, Department of Thematic Studies, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2321.
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Hållbar utveckling är ett av FN:s överordnade mål och även den Svenska regeringen har antagit detta som ett prioriterat mål för samhällsutvecklingen. Regeringen har genom en rad åtgärder försökt integrera begreppet hållbar utveckling i den statliga förvaltningen bl a genom styrdokument som skall hjälpa myndigheterna, men även genom att ställa konkreta krav på att myndigheterna inför miljöledningssystem.
Den nystartade distansutbildningsmyndigheten Nationellt centrum för flexibelt lärande (CFL) blev under 2002 införlivade i projektet "Miljöledning i statlig förvaltning" och genomförde en miljöutredning under 2002 där de mest betydande miljöaspekterna presenterades. Man ansåg emellertid att kunskap till viss del saknades inom den egna organisationen för att kunna genomföra en tillfredställande analys på området. Syftet med denna studie är att inom ramen för indirekt miljöpåverkan analysera vilken form av miljöutbildning som bedrivs på myndigheten och utifrån detta utvärdera i vilken utsträckning CFL har möjlighet att generera positiv miljöpåverkan.
I studien har fyra anställda på myndigheten CFL intervjuats för att kartlägga om begreppet hållbar utveckling är förankrat och integrerat i organisationen, vilken typ av miljöundervisning som bedrivs på myndigheten idag och kartlägga vad de fyra anser om de styrdokument som skall stödja dem i utbildningen. En enkät har även skickats ut till respondenterna efter genomförda intervjuer för att yterligare säkerställa de resultat som genererades i intervjuerna. För att undersöka myndighetens förutsättningar för att generera positiv miljöpåverkan har även en kortare dokumentanalys genomförts på myndighetens miljöpolicy.
Av studien framkommer att den miljöutbildning som bedrivs på myndigheten idag i stor utsträckning kan likställas vid normerande miljöundervisning. I och med att denna undervisningsform tillämpas får det till följd att myndigheten inte genererar den positiva miljöpåverkan man har möjlighet att göra. Studien visar också att respondenterna har svårt att se sambanden och knyta ihop de aspekter som ingår i hållbar utveckling, d.v.s. ekonomiska, ekologiska och sociala frågor. Hållbar utveckling är inte heller integrerat i tillräckligt stor omfattning i myndighetens verksamhet och därmed beaktas inte de indirekta miljöeffekterna myndigheten orsakar i tillräcklingt stor omfattning. Inte heller miljöpolicyn är anpassad för att ta upp den indirekta miljöpåverkan som myndigheten orsakar.
Slutsatsen i studien är att myndigheten först och främst måste integrera begreppet hållbar utveckling i högre utsträckning i verksamheten för att generera positiv miljöpåverkan och samtidigt beakta den indirekta miljöpåverkan man orsakar. För att detta skall vara möjligt måste man öka den interna kunskapen angående miljöfrågor och hållbar utveckling bland personal. I detta sammanhang kan Ledningsens roll inte underskattas utan måste tydligt visa att man menar allvar. Det är viktigt att beslut, strategier och riktlignjer genomlyses med utgågspunkt från indirekta och direkta miljökonsekvenser för att verksamheter vid CFL skall kunna bli långsiktigt hållbara.
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Roos, Anders. "Simulering av värmeförluster för kopparrör : En studie av värme- och strömningsparametrar för rörströmning." Thesis, Karlstad University, Faculty of Technology and Science, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-6086.
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Att använda fjärrvärme till lågenergihus kan vara olämpligt pga. höga kulvertförluster jämfört med kulvertförluster för traditionella hus. Detta beror på att det låga värmebehovet i lågenergihusen ger en hög returtemperatur i ledningarna. Ett steg för att öka värmebehovet och göra fjärrvärme mer attraktivt för lågenergihus är att börja värma upp vitvaror (tvätt-, diskmaskin och torktumlare) med fjärrvärme istället för att använda traditionella eluppvärma vitvaror. Vid installation av dessa vitvaror tillkommer en rördragning vars värmeförluster är önskvärda att hålla nere för att dels säkerställa önskad temperatur till vitvarorna men även för att hålla nere internvärmen i huset.
I studien har olika rördimensioner och isoleringstjocklek analyserats för att se hur värmeförlusterna beror på strömningsparametrar. Av analysen ska de bästa alternativen för val av rör tas fram för en rördragning i luft respektive i betong. För att beräkna värmeförlusterna har simuleringsmodeller tagits fram i CFD-programmet (Computational fluid dynamics) Comsol Multiphysics. Studien är indelad i två delar. Första delen analyserar fem stycken standardrör med givna rördimensioner och isoleringstjocklek. Den andra delen av studien analyserar värmeförlusterna beroende på varierad isoleringstjocklek för de två minsta rördiametrarna hos standardrören.
Resultatet i första studien visar att värmeförlusterna ökar med ökande rördiameter och att rörströmningen inte har någon betydande påverkan för värmeförlusterna. Andra studien visar att redan vid halva standardisoleringstjockleken kan värmeförlusterna minskas med 91 % jämfört med ett oisolerat rör. Simuleringarna visar att en rördragning i betong ger större värmeförluster än vid en rördragning i luft. Det beror på att betongen med dess ledningsförmåga förbättrar värmeavgivningen från röret mer än vad egenkonvektionen påverkar värmeförlusterna för en rördragning i luft.
Vid val av vilket standardrör som skall användas med hänsyn till lägsta värmeförlust, är den minsta rördiametern bäst för en rördragning i luft. I betong däremot är värmeförlusterna lika stora för både det minsta röret och det mellersta standardröret. Skillnaden mellan de två rören är rördiametern samt att det är tjockare isolering på det mellersta röret.
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Podola, David. "Parametrická studie zařízení pro zpětné získávání tepla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230445.
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This diploma thesis deals with the impact of changes in operating and geometrical parameters of regenerative heat exchanger on the efficiency of decentralized ventilation units with heat recovery. Decentralized ventilation unit can be used for ventilation of family houses or smaller administration buildings. Output of this work is to determine the efficiency of a particular produced model of decentralized ventilation unit and overview of the possibilities increased efficiency of heat recovery of this units.
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Norniella, Francisco Olga. "Inclusive Jet Production Studies at the Tevatron using the CDF Detector." Doctoral thesis, Universitat Autònoma de Barcelona, 2007. http://hdl.handle.net/10803/3386.
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QCD es una teoría que gobierna la interacción fuerte entre quarks y gluones dentro de los hadrones, por ejemplo, protones y neutrones. Esta teoría tiene dos características: libertad asintótica y color confinamiento. La dependencia de la constante de acoplamiento con la escala es tal que esta decrece con la distancia entre partones. Esto permite realizar precisos cálculos teóricos a una gran escala de energía usando teoría de perturbaciones (pQCD). Además, la fuerza de la interacción incrementa con la distancia entre partones y gluones obligando que estos estén confinados en hadrones.En el acelerador Tevatron, protones y antiprotones colisionan a una alta energía. En estas colisiones se producen jets de hadrones colimados en la misma dirección de los quarks y gluones que han colisionado. La medida de la sección eficaz de producción de jets centrales constituye una prueba de las predicciones de pQCD en más de ocho órdenes de magnitud. Además la medida también es sensible a la distribución de los partones dentro del proton (PDFs). Medidas de la producción de jets a grandes rapidititis son importantes porque ayudan a restringir la incertidumbre en esas distribuciones de los partones en una región donde no se espera señal de nueva física.
Esta tesis presenta la medida de producción de jets usando datos recogidos por el experimento CDF, uno de los detectores que estudia las colisiones en Tevatron. La medida esta hecha con un algoritmo muy preciso para buscar jets, relativamente nuevo en colisionadores hadrónicos. La medida esta comparada con predicciones de pQCD, donde los efectos de efectos no-perturbativos han sido incluidos. Los resultados demuestran que hay un excelente acuerdo entre la medida y la teoría, no mostrando señal de nueva física. Además, las incertidumbre es la medida son mas pequeñas que la teoría, cosa que indica que estas medidas pueden ser usadas para restringir las PDFs.
QCD is the gauge theory that governs the strong interactions between quarks and gluons inside hadrons like, for example, protons and neutrons. It shows two well established characteristics, related to the non-abelian nature of the theory, that dominate its phenomenology: asymptotic freedom and color confinement. The dependence of the strong coupling with the hard scale is such that it decreases with decreasing the distance between partons. This allows performing precise theoretical calculations at large energy transfer using perturbative QCD (pQCD). In the other hand, the strength of the interaction increases with the distance between partons and thus colored quarks and gluons are forced to be confined inside colorless hadrons.
At the Tevatron at Fermilab, protons and antiprotons collide at very high energy. In those collisions, collimated jets of hadrons are produced along the direction of struck quarks and gluons in the final state. The measurement of the inclusive jet production cross section provides a stringent test of pQCD predictions over almost nine orders of magnitude. In addition, the measurement is sensitive to the parton distribution in the proton (PDFs). Jet measurements at large rapidities are important because they constrain the gluon density in a region where no effect from new physics is expected.
This PhD. Thesis presents a measurement of the inclusive jet production cross section using the new data collected by the CDF experiment in Run II, one of the detectors at Tevatron. The longitudinally invariant kT algorithm has been used in order to search for jets in the final state. The measurement is compared to pQCD NLO calculations where non-perturbative effects from the underlying event and the fragmentation of partons into jets of hadrons have been taken into account. The results show an excellent agreement between the measurements and the theory, without presenting signal for new physics. In addition the systematic uncertainties in the measurements are smaller than in the theory, indicating that these measurements can be used to constrain the PDFs.
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Takeda, Yohei. "Studies on Synthesis and Properties of CF3-Substituted π-Conjugated Molecules." 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120820.
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