Mikrovågsuppvärmning är en viktig process som används i många industriella tillämpningar. Användningen av mikrovågsuppvärmning inom industri är dock inte lika utbredd som den har potential till att vara på grund av orsaker som säkerhet, strålning och brist på kunskap. Arbetets mål är att få ökad förståelse för hur materialegenskaper som permittivitet, termisk ledningsförmåga och elektrisk ledningsförmåga påverkar upphettning i mikrovågsugn. För att åstadkomma detta utförs simuleringar samt experiment på grafit som undersöks under mikrovågsuppvärmning i kiln anpassad för mikrovågsugn. Resultaten jämförs med liknande simulationer av det dielektriska materialet regolit. Händelsen simuleras först i COMSOL Multiphysics varefter korresponderande laboration utförs i verkligheten. För att åstadkomma fungerande simulation i COMSOL kalibreras den med hjälp av en tidigare utförd simulation av kiln i mikrovågsugn samt med COMSOLs egna Microwave Heating-tutorial. Under arbetets gång läggs mycket energi på att optimera simuleringen utefter diverse problem, exempelvis att simulationen är väldigt krävande. Slutligen uppnås fungerande simuleringar som relaterade väl till det riktiga experimentet.

Sickle cell disease (SCD) is a severe genetic disease, affecting over 100,000 in the United States and millions worldwide. Individuals suffer from stroke, acute chest syndrome, and cardiovascular complications. Much of these associated morbidities are primarily mediated by blockages of the microvasculature, events termed vaso-occlusive crises (VOCs). Despite its prevalence and severity, the pathophysiological mechanisms behind VOCs are not well understood, and novel experimental tools and methods are needed to further this understanding. Microfluidics and computational fluid dynamics (CFD) are rapidly growing fields within biomedical research that allow for inexpensive simulation of the in vivo microenvironment prior to animal or clinical trials. This study includes the development of a CFD model capable of simulating diseased and healthy blood flow within a series of microfluidic channels. Results will be utilized to further improve the development of microfluidic systems.

Partial discharge (PD) is a micro discharge that occurs in defected regions within the insulating media. As these discharges are the main culprits that cause dielectric material aging, PD measurements have been used for assessing insulating materials, including solids, liquids, and gases for power applications. There are various methods and sensors available for measuring PD sensitive to specific characteristics and operable over a wide range of frequencies. Most PD measurement techniques provide patterns that enable PD interpretation more comfortable for users. For example, in AC applications, the phase-resolved partial discharge (PRPD) technique provides identifiable patterns for distinguishing various types of PDs. However, the establishment of meaningful patterns to multiple types of PD in DC systems requires more sensitive and accurate measurements of individual PD pulses with noise rejection functionality due to the lack of phase-resolved information. Investigating of the transient phenomena such as individual PD pulses requires well-designed circuits with sufficiently large bandwidths. Waveshapes can be easily disturbed by background noise and deformed by the frequency response of measuring circuits and data acquisition systems (DAQ). Noises are unwanted disturbances that could be suppressed by suitable filters or mathematical methods. Measurement circuits and DAQ systems consist of transmission lines, sensors, cables, connectors, DAQ hardware, and oscilloscopes. Therefore, matching the impedance of all components guarantees a reflectionree path for traveling signals and addresses most of the challenges relevant to transient measurements. In this dissertation, we proposed and designed an appropriate testbed equipped with high bandwidth transmission line and electromagnetic field sensors suitable for investigating PD under DC electrical stresses. We comprehensively used finite element analysis simulations through the COMSOL Multiphysics software to design the dimensions and evaluate the frequency response of the testbed, transmission line, and electromagnetic sensors. Furthermore, based on the new testbed, DC PD measurements were performed using conventional and non-conventional sensors. Finally, various types of DC PD were statistically classified based on the proposed testbed.

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Yes / A mass transfer model was developed for CO2 capture from a binary gas mixture of N2/CO2 in hollow fibre membrane contactors under laminar flow conditions. The axial and radial diffusions through membrane and convection in tube and shell sides with chemical reaction were investigated. COMSOL software was used to numerically solve a system of non-linear equations with boundary conditions by use of the finite element method. Three different amine solutions of monoethanolamine (MEA), diethanolamine (DEA) and n-methyldiethanolamine (MDEA) were chosen as absorbent in lumen to consider the mass transfer rate of CO2 and compare their removal efficiency. The modelling results were compared with experimental data available in the literature and a good agreement was observed. The CFD results revealed that MEA had the best performance for CO2 removal as compared to DEA and MDEA under various operating conditions due to the different CO2 loading factor of absorbents. Furthermore, efficiency of CO2 removal was highly dependent on the absorbent concentration and its flow rate, increasing of the gas flow rate caused a reduction in gas residence time in the shell and consequently declined CO2 mass transfer. The modelling results showed the influence of the absorbent concentration on the CO2 mass transfer has improved due to availability of absorbent reactants at the gas-liquid interface.

The aim in this project is to find a design space for a condenser type bushing given by HitachiEnergy. The design space shows which combinations of air and silicon-rubber (SiR) conductivity remain under a specified electric field strength value. This range of value represents how humidity affects air and SiR conductivity. Hitachi energy provided two different models, one with foils and one without foils. The design space for these models consists of how humidity affects the conductivity of both air and SiR. The values of air conductivity are gathered from different studies with different air humidity and external effects that affect the conductivity such as high aerosol concentration and high radon concentration. The values used for simulation will be approximated because of the different external effects and will range from 10^(−12)–10^(−13) S/m for humid conditions, 10^(−14) S/m for average humidity conditions and 10^(−15)–10^(−16) S/m for dry conditions. The range of SiR conductivity and the correlated weather conditions was given by Hitachi Energy and range from 10^(−11)–10^(−15) S/m where 10^(−11) S/m is for humid conditions, 10^(−12)–10^(−14) S/m for average humidity conditions and 10^(−15) S/m for dry conditions. For each of these combinations of conductivity the maximum electric field strength is calculated using COMSOL Multiphysics and compared to the threshold value of 2 kV/mm. Using these parameters the maximum electric field strength on the sheds of the bushing was calculated using COMSOL Multiphysics for all combinations of SiR and air conductivity. The results shows a pattern for both models. SiR conductivity must be higher or equal to the air conductivity to be below the threshold of 2 kV/mm.