Global ETD Search

1	Uniform Field Distribution Using Distributed Magnetic Structure Keezhanatham Seshadri, Jayashree 13 January 2014 (has links) Energy distribution in a conventional magnetic component is generally not at a designer's disposal. In a conventional toroidal inductor, the energy density is inversely proportional to the square of the radius. Thus, a designer would be unable to prescribe uniform field distribution to fully utilize the inductor volume for storing magnetic energy. To address this problem a new inductor design, called a "constant-flux" inductor, is introduced in this thesis. This new inductor has the core and windings configured to distribute the magnetic flux and energy relatively uniformly throughout the core volume to achieve power density higher than that of a conventional toroidal inductor. The core of this new inductor design is made of concentric cells of magnetic material, and the windings are wound in the gaps between the cells. This structure is designed to avoid crowding of the flux, thus ensuring lower core energy losses. In addition, the windings are patterned for shorter length and larger area of cross-section to facilitate lower winding energy losses. Based on this approach, a set of new, constant flux inductor/transformer designs has been developed. This design set is based on specific input parameters are presented in this thesis. These parameters include the required inductance, peak and rms current, frequency of operation, permissible dc resistance, material properties of the core such as relative permeability, maximum permissible magnetic flux density for the allowed core loss, and Steinmetz parameters to compute the core loss. For each constant flux inductor/transformer design, the winding loss and core loss of the magnetic components are computed. In addition, the quality factor is used as the deciding criterion for selection of an optimized inductor/transformer design. The first design presented in this thesis shows that for the same maximum magnetic field intensity, height, total stored energy, and material, the footprint area of the new five-cell constant-flux inductor is 1.65 times less than that of an equivalent conventional toroidal inductor. The winding loss for the new inductor is at least 10% smaller, and core loss is at least 1% smaller than that in conventional inductors. For higher energy densities and taller inductors, an optimal field ratio of the dimensions of each cell (α = Rimin/Rimax) and a larger number of cells is desired. However, there is a practical difficulty in realizing this structure with a larger number of cells and higher field ratio α. To address this problem, an inductor design is presented that has a footprint area of a three-cell constant-flux inductor (α = 0.6) that is 1.48 times smaller in comparison to an equivalent conventional toroidal inductor. For the same maximum magnetic flux density, height, material, and winding loss, the energy stored in this new three-cell constant-flux inductor (α = 0.6) is four times larger than that of an equivalent conventional toroidal inductor. Finally, new designs for application-specific toroidal inductors are presented in this thesis. First, a constant-flux inductor is designed for high-current, high-power applications. An equivalent constant-flux inductor to a commercially available inductor (E70340-010) was designed. The height of this equivalent inductor is 20% less than the commercial product with the same inductance and dc resistance. Second, a constant-flux inductor design of inductance 1.2 µH was fabricated using Micrometal-8 for the core and flat wire of 0.97 mm x 0.25 mm for the conductor. The core material of this inductor has relative permeability < 28 and maximum allowed flux density of 3600 Gauss. The dc resistance of this new, constant flux inductor was measured to be 14.4 mΩ. / Master of Science constant flux constant-flux inductor low temperature co-fired ceramic low-profile magnetics quality factor transformer
2	Bench-Scale Assessment of Low Pressure Membrane Fouling: Characterization and Examination the Role of Organic Nitrogen Compounds Nguyen, Anh Hai 01 September 2010 (has links) The primary goal of this research was to improve understanding of the fouling of low pressure hollow fiber membranes used in drinking water treatment. The major difference of this study compared to other reported studies was the use of a hollow fiber membrane module at operating conditions mimicking those of full-scale practice. Two poly(vinylidene-fluoroethylene) based hollow fiber membranes (A and B) were tested. Different types of fouling indices (total, hydraulic irreversible, chemical irreversible) developed based on a resistance in series model were used to assess membrane performance. Data from bench-scale and full-scale plants were compared to validate the use of fouling indices. The impact of dissolved organic nitrogen (DON) on membrane fouling was demonstrated with model waters containing humic substances and several model organic nitrogen compounds. Three different natural water sources normalized to the same organic content were tested. Fouling indices determined from the resistance in series model approach were more applicable for natural waters than for model waters. Fouling was proportional to throughput for both raw and pretreated water and at different flux rates. Pretreatment (coagulation) reduced hydraulic irreversible fouling. Most fouling was reversed by hydraulic and chemical cleaning. Specific flux and fouling indices of the bench-scale system were higher than those of the full-scale system but the fouling index ratios were comparable suggesting a similar fouling nature. A minimum of a few days of testing is recommended for longer-term membrane performance assessment. The impact of high DON concentration on membrane fouling was insignificant. Membrane fouling was dependant on foulant properties other than, or in addition to, molecular size and the DON/DOC ratio. With three different natural water sources normalized to a similar organic content, membrane fouling was specific to membrane type and water source. High initial total and hydraulic irreversible fouling rates did not lead to high chemical irreversible fouling rates. It is not possible to generalize the impact of different water sources on membrane fouling. Membrane surface anlyses showed that hydraulically irreversible organic foulants were detected as mostly hydrocarbons/polysaccharides, humic substances and peptide/protein. Humic substances and peptide/protein were found to be organic foulants regardless of their molecular weight and origin. Chemical cleaning with chlorine solution was effective in removing all inorganic foulants and most organic foulants. backwash constant flux fouling low pressure membrane NOM Civil and Environmental Engineering
3	Constant-Flux Inductor with Enclosed-Winding Geometry for Improved Energy Density Cui, Han 11 September 2013 (has links) The passive components such as inductors and capacitors are bulky parts on circuit boards. Researchers in academia, government, and industry have been searching for ways to improve the magnetic energy density and reduce the package size of magnetic parts. The "constant-flux" concept discussed herein is leveraged to achieve high magnetic-energy density by distributing the magnetic flux uniformly, leading to inductor geometries with a volume significantly lower than that of conventional products. A relatively constant flux distribution is advantageous not only from the density standpoint, but also from the thermal standpoint via the reduction of hot spots, and from the reliability standpoint via the suppression of flux crowding. For toroidal inductors, adding concentric toroidal cells of magnetic material and distributing the windings properly can successfully make the flux density distribution uniform and thus significantly improve the power density. Compared with a conventional toroidal inductor, the constant-flux inductor introduced herein has an enclosed-winding geometry. The winding layout inside the core is configured to distribute the magnetic flux relatively uniformly throughout the magnetic volume to obtain a higher energy density and smaller package volume than those of a conventional toroidal inductor. Techniques to shape the core and to distribute the winding turns to form a desirable field profile is described for one class of magnetic geometries with the winding enclosed by the core. For a given set of input parameters such as the inductor's footprint and thickness, permeability of the magnetic material, maximum permissible magnetic flux density for the allowed core loss, and current rating, the winding geometry can be designed and optimized to achieve the highest time constant, which is the inductance divided by resistance (L/Rdc). The design procedure is delineated for the constant-flux inductor design together with an example with three winding windows, an inductance of 1.6 µH, and a resistance of 7 mΩ. The constant-flux inductor designed has the same inductance, dc resistance, and footprint area as a commercial counterpart, but half the height. The uniformity factor α is defined to reflect the uniformity level inside the core volume. For each given magnetic material and given volume, an optimal uniformity factor exists, which has the highest time constant. The time constant varies with the footprint area, inductor thickness, relative permeability of the magnetic material, and uniformity factor. Therefore, the objective for the constant-flux inductor design is to seek the highest possible time constant, so that the constant-flux inductor gives a higher inductance or lower resistance than commercial products of the same volume. The calculated time-constant-density of the constant-flux inductor designed is 4008 s/m3, which is more than two times larger than the 1463 s/m3 of a commercial product. To validate the concept of constant-flux inductor, various ways of fabrication for the core and the winding were explored in the lab, including the routing process, lasing process on the core, etching technique on copper, and screen printing with silver paste. The most successful results were obtained from the routing process on both the core and the winding. The core from Micrometals has a relative permeability of around 22, and the winding is made of copper sheets 0.5 mm thick. The fabricated inductor prototype shows a significant improvement in energy density: at the same inductance and resistance, the volume of the constant-flux inductor is two times smaller than that of the commercial counterpart. The constant-flux inductor shows great improvement in energy density and the shrinking of the total size of the inductor below that of the commercial products. Reducing the volume of the magnetic component is beneficial to most power. The study of the constant-flux inductor is currently focused on the dc analysis, and the ac analysis is the next step in the research. / Master of Science constant-flux time constant magnetic field uniformity factor high-density inductor high-density transformer high-density magnetic distributed core distributed winding
4	Focused flow during water infiltration into ethanol-contaminated unsaturated porous media Jazwiec, Alicja N. 06 1900 (has links) The increasing commercial and industrial use of ethanol, i.e., in biofuel and gasoline, has generated increased incidents of vadose zone contamination by way of ethanol spills and releases. This has increased the interest in better understanding infiltration behaviours of ethanol in unsaturated porous media and the multiphase interactions in the vadose zone. Solute-dependent capillarity-induced focused flow (SCIFF) is a vertical, highly focused flow infiltration behaviour first reported by Smith et al. (2011) in butanol-contaminated sands. Through the use of highly controlled laboratory experiments, this thesis research investigates focused flow (SCIFF) and related behaviours through water infiltration into ethanol-contaminated unsaturated sand. Focused flow behaviours (SCIFF) were demonstrated through the infiltration of water into an ethanol-contaminated unsaturated sand using both constant flux and constant head methodologies. The observation of focused flow behaviours in ethanol-contaminated sand supported the primary hypothesis of this work. The secondary hypothesis was also supported, as focused flow behaviours were not observed, rather stable semicircular infiltration patterns were observed during ethanol infiltration into water-wet sand. Comparisons between constant flux and constant head application methods under similar flow rates and fluid volumes produced similar results. The zone of lower saturation, or the “halo effect” reported in previous literature, was strongly expressed during water infiltration in ethanol-contaminated sand. This halo effect is affected by the maximum (at 40% to 50%) of aqueous concentration of ethanol. This maximum enhances the zone of lower saturation and stabilizes the solute front. The SCIFF focused flow also overcame the effects of minor heterogeneities in the sand. However, additional laboratory and modelling work is required to further understand the extent of SCIFF behaviour. / Thesis / Master of Science (MSc) / Understanding the behaviour and interaction of water and contaminants in soils is important as environmental contamination and spills can have devastating environmental impacts. In recent decades, ethanol spills and accidental releases onto ground surface have increased as the commercial and industrial use of ethanol has increased. The goals of this work were to qualitatively visualize and quantify the unique nature of water infiltration into the ethanol-contaminated soil and understand the complex mechanisms behind water-ethanol interactions. This research showed that water infiltration creates an uncommon vertical, focused pattern when flowing into sand contaminated by ethanol. However, when ethanol is applied to standard water-wet sand, that behaviour is not observed. This work provided greater insight into the nature of ethanol-contaminated soils. These findings furthered the understanding needed to evaluate impacts that ethanol contamination can have on remedial efforts and the rate of migration of contaminants to groundwater. focused flow SCIFF vadose zone infiltration ethanol unsaturated zone flow cell porous media rainulator constant flux tension infiltrometer constant head soil physics hydrology hydrogeology
5	Development of High-throughput Membrane Filtration Techniques for Biological and Environmental Applications / Development of High-throughput Membrane Filtration Techniques Kazemi, Amir Sadegh 11 1900 (has links) Membrane filtration processes are widely utilized across different industrial sectors for biological and environmental separations. Examples of the former are sterile filtration and protein fractionation via microfiltration (MF) and ultrafiltration (UF) while drinking water treatment, tertiary treatment of wastewater, water reuse and desalination via MF, UF, nanofiltration (NF) and reverse-osmosis (RO) are examples of the latter. A common misconception is that the performance of membrane separation is solely dependent on the membrane pore size, whereas a multitude of parameters including solution conditions, solute concentration, presence of specific ions, hydrodynamic conditions, membrane structure and surface properties can significantly influence the separation performance and the membrane’s fouling propensity. The conventional approach for studying filtration performance is to use a single lab- or pilot-scale module and perform numerous experiments in a sequential manner which is both time-consuming and requires large amounts of material. Alternatively, high-throughput (HT) techniques, defined as the miniaturized version of conventional unit operations which allow for multiple experiments to be run in parallel and require a small amount of sample, can be employed. There is a growing interest in the use of HT techniques to speed up the testing and optimization of membrane-based separations. In this work, different HT screening approaches are developed and utilized for the evaluation and optimization of filtration performance using flat-sheet and hollow-fiber (HF) membranes used in biological and environmental separations. The effects of various process factors were evaluated on the separation of different biomolecules by combining a HT filtration method using flat-sheet UF membranes and design-of-experiments methods. Additionally, a novel HT platform was introduced for multi-modal (constant transmembrane pressure vs. constant flux) testing of flat-sheet membranes used in bio-separations. Furthermore, the first-ever HT modules for parallel testing of HF membranes were developed for rapid fouling tests as well as extended filtration evaluation experiments. The usefulness of the modules was demonstrated by evaluating the filtration performance of different foulants under various operating conditions as well as running surface modification experiments. The techniques described herein can be employed for rapid determination of the optimal combination of conditions that result in the best filtration performance for different membrane separation applications and thus eliminate the need to perform numerous conventional lab-scale tests. Overall, more than 250 filtration tests and 350 hydraulic permeability measurements were performed and analyzed using the HT platforms developed in this thesis. / Thesis / Doctor of Philosophy (PhD) / Membrane filtration is widely used as a key separation process in different industries. For example, microfiltration (MF) and ultrafiltration (UF) are used for sterilization and purification of bio-products. Furthermore, MF, UF and reverse-osmosis (RO) are used for drinking water and wastewater treatment. A common misconception is that membrane filtration is a process solely based on the pore size of the membrane whereas numerous factors can significantly affect the performance. Conventionally, a large number of lab- or full-scale experiments are performed to find the optimum operating conditions for each filtration process. High-throughput (HT) techniques are powerful methods to accelerate the pace of process optimization—they allow for multiple experiments to be run in parallel and require smaller amounts of sample. This thesis focuses on the development of different HT techniques that require a minimal amount of sample for parallel testing and optimization of membrane filtration processes with applications in environmental and biological separations. The introduced techniques can reduce the amount of sample used in each test between 10-50 times and accelerate process development and optimization by running parallel tests. Membrane filtration Ultrafiltration Downstream bio-processing High-throughput (HT) testing Wastewater treatment Hollow-fiber membranes Humic acids High-throughput filtration Design-of-experiments (DOE) Process optimization Microscale filtration Microfluidic flow control system Stirred well filtration SWF High-throughput hollow-fiber module HT-HF Constant TMP Constant flux Multi-modal filtration Bioseparation MMFC MS-PS-CFF PEG Dextran FITC-Dextran BSA DNA IgG α-lactalbumin Biomolecule separation Module hydrodynamics Concentration polarization Membrane fouling Micromixing Omega™ membrane Microscale processing Fouling test PVDF membrane Surface modification Polydopamine Membrane cleaning Membrane backwashing Sodium alginate Polyethersulfone PES Hydraulic permeability Membrane permeability ZeeWeed® membrane Filtration ionic strength Filtration pH Solution conditions Water treatment Environmental separations Biological separations

1

Page generated in 0.0672 seconds