Aluminium recycling requires 95% less energy than primary production with no loss of quality. The Black Dross (BD) produced during secondary aluminium production contains high amounts of water-soluble compounds, therefore it is considered as a toxic waste. In the present work, salt removal from BD by thermal treatment has been investigated in laboratory scale. The optimum conditions for treatment were established, i.e., temperature, gas flow rate, holding time, rotation rate, and sample size. The overall degree of chloride removal was established to increase as a function of time and temperature. Even Pretreated Black Dross (PBD) was evaluated as a possible raw material for the production of a calcium aluminate-based ladle-fluxing agent to be used in the steel industry. The effects of different process parameters on the properties of the produced flux were experimentally investigated, i.e. CaO/Al2O3 ratio, temperature, holding time, and cooling media. The utilization of PBD as the alumina source during the production of a calcium aluminate fluxing agent shows promising results. The iron/steel industry is responsible for 9% of anthropogenic energy and process CO2 emissions. It is believed that the only way to a long-term reduction of the CO2 emissions from the iron/steel industry is commercialization of alternative processes such as Direct Reduction (DR) of iron oxide. Detailed knowledge of the kinetics of the reduction reactions is, however, a prerequisite for the design and optimization of the DR process. To obtain a better understanding of the reduction kinetics, a model was developed step-by-step, from a single pellet to a fixed bed with many pellets. The equations were solved using the commercial software COMSOL Multiphysics®. The final model considers the reaction rate and mass transfer inside the pellet, as well as the mass transfers and heat transfer in the fixed bed. All the models were verified against experimental results, and where found to describe the results in a satisfying way. / <p>QC 20161128</p>

Poor heat and mass transfer inside the adsorbent bed of thermal wave adsorption cooling cycles cause low system performance and is an important problem in the adsorbent bed design. In this thesis, a new adsorbent bed is designed, constructed and tested to increase the heat and mass transfer in the adsorbent bed. The adsorbent bed is constructed from a finned tube in order to enhance the heat transfer. Additionally, the finned bed geometry is theoretically modeled and the model is solved time dependently by using Comsol Multiphysics software program. The distributions of dependent variables, i.e. temperature, pressure and amount adsorbed, are simulated and plotted in Comsol Multiphysics. In the model, the dependent variables are computed by solving the energy, mass and momentum transfer equations in a coupled way and their variations are investigated two-dimensionally. The results are presented with multicolored plots in a 2-D domain. Furthermore, a parametric study is carried out for determining factors that enhance the heat and mass transfer inside the adsorbent bed. In this parametric study, the effects of several design and operational parameters on the dependent variables are investigated. In the experimental study, the finned tube is tested using natural zeolite-water and silica gel-water working pairs. Temperature, pressure and amount adsorbed variations inside the adsorbent bed at various operating conditions are investigated. After that, a second adsorbent bed with a larger size is constructed and tested. The effect of the particle diameter of the adsorbent is also investigated. The experimental and theoretical results are compared.

L'objectif de ce travail est d'étudier expérimentalement la formation du capillaire durant le perçage et le soudage par faisceau laser, et de développer une simulation numérique permettant de reproduire la dynamique de formation et d'évolution du capillaire. Nous avons fait le choix d'utiliser comme matériau test le Zinc, en raison de ses propriétés thermodynamiques. Afin de simplifier le problème, nous avons étudié dans un premier temps le mécanisme de perçage. Deux méthodes expérimentales ont été utilisées pour caractériser l'évolution de la géométrie du capillaire : La méthode DODO (Direct Observation of Drilled hOle ) permet de visualiser le capillaire après perçage pour différentes durées et la méthode Zn-Quartz permet d'observer directement son évolution temporelle par camera rapide à travers une lame de quartz. Puis nous avons utilisé cette évolution pour mettre au point une simulation du mécanisme de perçage. Après avoir étudié le dépôt de puissance à l'intérieur d'un capillaire en tenant compte des réflexions multiples et estimé l'importance de la perte d'énergie et de matière lors du processus, nous avons développé une simulation en utilisant le logiciel Comsol Multiphysics couplant l'équation thermique, l'équation de Navier Stokes et prenant en compte le déplacement du métal fondu sous l'action de la pression de recul. Dans ce cas, on observe la formation d'un bourrelet important au bord du trou et une augmentation de la profondeur du capillaire. Ensuite nous avons étudié la formation du capillaire durant le soudage laser, c'est-à-dire avec déplacement de la source. A partir des techniques mises en œuvre pour l'étude du perçage nous avons obtenu l'évolution de la forme du capillaire dans le cas du soudage Zn/Quartz. Nous avons réalisé une simulation relativement simple en supposant la géométrie et la température du capillaire connues a priori. Nous avons constaté qu'un modèle simple, modélisant uniquement les transferts thermiques par conduction, permet de bien simuler la forme de la zone fondue pour les couples Zn/Zn et Zn-quartz.

The thesis deals with a computer modelling by means of the commercial software COMSOL Multiphysics. The thesis is structured into three topical sections. The first part is dedicated to the programme characteristics and its development. In the second part the brief characteristics of working with the programme COMSOL Multiphysics is presented which should make the user´s first steps in working with software easier. The last part of thesis shows the specific demonstration of the created multiple physics task taken from the field of plasma physics. This task is solved by means of continuous simulation of a computer modelling based on the drift-diffusion approximation of low temperature plasma. The proposal of the paper for the proceedings of the conference ,,Technical Computing Prague 2012" is also a part of this thesis.

This thesis proposes a novel air flow sensor based on PZT material which is used to measure air velocity in an experimental tunnel or indoor ventilation. The work focuses on designing and verifying the sensor model through finite element analysis (FEA) simulation using COMSOL Multiphysics software. This thesis is devoted to developing a sensor model with a focus on a low-velocity range up to 2 m/s and high sensitivity. The design of the sensor should be robust and reliable for different flow patterns, temperature, and atmospheric pressure variation. The sensor model consists of a fixed cylinder which connects with a bilayer cantilever made of PZT and PDMS material. The laminar flow from the sensor inlet is transformed into the turbulent flow when passing by the fixed cylinder. This structure of bilayer cantilever is designed to generate self-induced oscillation on PZT to overcome the charge leakage over the sensor impedance. Resonance optimization of the sensor structure is investigated to obtain better SNR and performance by adjusting the dimension of the cantilever. From the conducted simulation results, the relationship between the dominant frequency of output voltage generated by PZT and air velocity can be described linearly. In conclusion, it is shown that proposed sensor has a sensitivity of 0.1 m/s and a range of 0.2 to 2 m/s.

This work is focused on computer simulations of fractal capacitors. The geometry of capacitors and its influence is investigated. Simulations are realized in programs Matlab, SolidWorks and Comsol Multiphysics. There are also several specific examples of different geometrics of capacitors their comparisons and assessment.

Many industries have entered a new global phase which takes the environment in mind. The gas turbine industry is no exception, where the utilization of green fuels is the future to spare the environment from carbon dioxide and NOx emissions. Hydrogen has been identified as a fuel which can fulfil the global requirements set by governments worldwide. Combustion instabilities are not inevitable during gas turbine operations, especially when using a highly reactive and diffusive fuel as hydrogen. These thermoacoustics instabilities can damage mechanical components and have economic consequences in terms of maintenance and reparation. Understanding these thermoacoustic instabilities in gas turbine burners is of great interest. COMSOL Multiphysics offers a robust acoustic module compared to other available acoustic simulation programs. In this thesis, an Acoustic finite element model was built representing an atmospheric combustion rig (ACR), used to test the burners performance and NOx emissions. Complementary computational fluid dynamics (CFD) simulations were performed for 100 % hydrogen as fuel by using the Reynolds average Navier-Stokes (RANS) lag EB k - epsilon turbulence model. Necessary data was successfully imported to the Acoustic finite element model. Different techniques of building the mesh were used in COMSOL Multiphysics and NX. Similar results were obtained, proving that both mesh tools work well in acoustic simulations. Two different ways of solving the eigenvalue problem in acoustics were implemented, the classic Helmholtz equation and Linearized Navier-Stokes equations, both in the frequency domain. The Helmholtz equation proved to be efficient and detected multiple modes in the frequency range of interest. Critical modes which lived in the burner and the combustion chamber were identified. Defining a hard and soft wall boundary condition at the inlets and outlet of the atmospheric combustion rig gave similar eigenfrequencies when comparing the two boundary conditions. The soft wall boundary condition was defined with a characteristic impedance, giving a high uncertainty whether the results were trustworthy or not. A boundary condition study revealed that the boundary condition at the outlet was valid for modes living in the burner and combustion chamber. Solving the eigenvalue problem with the Linearized Navier-Stokes equations proved to be computationally demanding compared to the Helmholtz equation. Similar modes shapes were found at higher frequencies, but pressure perturbations were observed in the region where the turbulence was dominant. A prestudy for a stability analysis was established, where the ACR and the flame was represented as a generic model. Implementing a Flame Transfer Function (FTF), more specifically a linear n - tau model, showed that the time delay tau is most sensible for a parametric change and hence needs to be chosen cautiously

Ansys, Flux or COMSOL are examples of software-tools that can be used to study magnetic noise, caused by magnetic forces in the air-gap, in induction motors. The project team wanted to use COMSOL in this thesis. The electromagnetical domain needs to be coupled to the mechanical domain to complete the study. The air-gap forces, calculated in the electromagnetical model using the Rotating Machinery module, can be exported to the Acoustic-Solid Interaction module in COMSOL to enable the vibro-acoustic analysis. An electromagnetical model of an induction motor is developed in two-dimensions in the finite element method based software-tool COMSOL Multiphysics in this thesis. Simulation results obtained in the frequency domain are compared with results achieved in the software-tool FEMM. Simulation results of the phase inductance, distribution of the flux density and the torque are compared. The simulated torque in COMSOL is validated with the torque derived based on an equivalent lumped model of the induction motor. A time-dependent simulation of the motor is made at 4.7% slip and 1A (peak) supply. The obtained torque is 0.33Nm. The same value is achieved in the frequency study in COMSOL. The corresponding value is 0.003Nm higher in FEMM. The evaluated air-gap forces at 4.7% slip can be used for studying vibro-acoustics in COMSOL. / Ansys, Flux eller COMSOL är exempel på datorprogram som kan användas för att studera magnetiskt brus, orsakad av magnetiska krafter i luftgapet, i induktionsmotorer. Projektgruppen ville använda COMSOL i det här examensarbetet. För att kunna utföra studien måste den elektromagnetiska domänen kopplas till den mekaniska domänen. Luftgapskrafterna, beräknade i den elektromagnetiska modellen genom att använda modulen för roterande maskiner, kan exporteras till modulen Acoustic-Solid Interaction för att möjliggöra den vibro-akustiska analysen. En elektromagnetisk modell av en induktionsmotor är utvecklad i två dimensioner i finita elementmetoden-baserade programvaran COMSOL Multiphysics i det här examensarbetet. Simuleringsresultat från frekvensdomänen jämförs med resultat som uppnås med datorprogramvaran FEMM. Simuleringsresultat för fas-induktansen, fördelningen av flödestätheten och momentet jämförs. Det simulerade momentet i COMSOL valideras med momentet som härleds utifrån induktionsmotorns motsvarande ekvivalenta schema. En tidsberoende motor-simulering genomförs vid 4.7% slip, matad med 1A (topp-värde). Det erhållna momentet är 0.33Nm. Samma värde erhålls i frekvensstudien i COMSOL. Värdet är 0.003Nm högre i FEMM. De beräknade luftgapskrafterna vid 4.7% slip kan användas för att göra en vibroakustisk studie i COMSOL.

Spintronics is a spin-electronic field where the electron spinangular momentum, in conjunction with charge, is used to read andwrite information in magnetic sensors and logic circuits, e.g. hard disk drive (HDD), magnetic random access memory (MRAM) and broadband TeraHertz (THz) emitters. To realize the THz operations of the spin logic circuits THz manipulation of the magnetic state is pivotal. This THz manipulation of the magnetic state in anti-ferromagnetic magnetic materials can be realized by coupling the materials with THz antennas. On the other hand, these antennas enhance the THz amplitude of spin-electronic THz emitters when coupled with its output. Therefore, these THz antennas can not only be coupled with the input of magnetic logics to improve the efficiency of magnetic sate manipulation in logic devices but also with the output of the spintronic THz emitters to enhance the generated THz signal amplitude. In this project, we have examined four types of antennas: h-dipole, spiral, bow-tie, and a sub-THz antenna. All the antennas are placed on top of a MgO substrate material for simplicity. However, a bow-tie antenna is also fabricated on an antiferromagnetic substrate of TmFeO3 to check this antenna’s reliability to manipulate its magnetic state. We have studied the impact of antenna geometries on the generated electric field amplitude. We have optimized each antenna for maximum electric field norm profile, with an increase of 30% for the h-dipole and spiral antennas, and an increase of 100% for the bow-tie antenna. However, in this project we were not able to find any general conclusions about what geometrical parameters can further amplify the generated electric field. None of the antennas generated a large enough peak-to-peak electric field amplitude to manipulate the magnetic state of anti-ferromagnetic materials. However, they did successfully amplify the spintronic THz emitter output and could certainly be useful in that regard.

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