Doctoral Theses
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The Doctoral Theses collection contains digital copies of AUT doctoral theses deposited with the Library since 2004 and made available open access. All theses for doctorates awarded from 2007 onwards are required to be deposited in Tuwhera Open Theses unless subject to an embargo.
For theses submitted prior to 2007, open access was not mandatory, so only those theses for which the author has given consent are available in Tuwhera Open Theses. Where consent for open access has not been provided, the thesis is usually recorded in the AUT Library catalogue where the full text, if available, may be accessed with an AUT password. Other people should request an Interlibrary Loan through their library.
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Browsing Doctoral Theses by Supervisor "Al Jumaily, Ahmed"
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- ItemFunctionally Coated Titanium Plate and Its Performance as Bipolar Plate Material for Hydrogen Fuel Cells(Auckland University of Technology, 2023) Mahenthiran, DhelipanA fuel cell is an electrochemical device which converts a hydrogen containing chemical into electricity with less environmental impact. But cost is a major hurdle to commercialisation of fuel cells. Bipolar plate accounts for 80% of weight and 45% of the cost of the Proton Exchange Membrane Fuel cell (PEMFC) stack. Bipolar plate is the multifunctional component responsible for electrical conduction from anode to cathode, distributing reactant gas to electrode, removing heat from the active region and preventing coolant – reactant gas cross-over. Graphite has long been used as Bipolar Plate because it performs most of the required functions but weight, cost, brittleness and poor machinability makes it a poor choice for portable applications. Metal plates are a better alternative to graphite as these can satisfy most of the qualities of bipolar plate (High electrical and thermal conductivity, easily stamped to get desired shape and good mechanical strength) but are prone to corrosion in the fuel cell environment and need protective coating. While major automakers use noble metal as the coating material, the need for non-noble coating is immense. Even though various researches have been done on non-noble metal coatings, very few reports are available on carbon based coatings and their long term significance for fuel cell performance. The performance of Titanium Nitride (TiN) and amorphous carbon (a-C) coatings are compared along with a novel tungsten carbide carbon (WCC) coating as bipolar coating materials. The corrosion current density and Interfacial Contact Resistance (ICR) of WCC coating are less than 1 µA/cm2 and 10 mΩ.cm2 respectively. This makes WCC the only coating material that satisfies the US DOE (Department of Energy) target 2025 for bipolar plate. The other coating materials satisfy or are on a par with DOE target either for corrosion resistance or ICR but not both. A die and punch was designed to fabricate plates using ANSYS software. The fabricated stamped plate showed no cracks and the thickness distributions at the critical spots were comparable with the simulation. The novel coating was extensively tested in the simulated fuel cell environment and coated on the stamped plate to study their long term performance in fuel cell single stack. The fuel cell performance of the coated plate was analysed and the peak power density of WCC was 0.321 W/cm2 at 0.8 A/cm2, while bare Ti shows peak power of 0.21 W/cm2 at 0.63 A/cm2. The long term performance of the bipolar plate in fuel cell environment was determined by maintaining fuel cell at constant current mode 0.50A/cm2 for 500 hours. The need for non-noble protective coating is immense for bipolar plate application. In this research it is successfully coated and tested in fuel cell environment, achieving all the objectives.
- ItemAn Investigation Into the Nano Fluids Physiochemical Properties Due to Ultrasonic Perturbation for Near Wellbore Remediation(Auckland University of Technology, 2021) M Veloo, VickneswaranResearch on nanofluids has been conducted extensively. However, to the best of our knowledge the protocol to produce nanofluid which will enhance the physio-chemical properties using external perturbation such as ultrasound and their effect on mass transfer kinetics during near well remediation is not established for field implementation for the oil and gas industry. In this thesis, a comprehensive study has been conducted to investigate the effect of ultrasonic amplitude variation on nanofluids physio-chemical properties. The study includes nanofluids formulation, preparation, optimization, ultrasonication at various amplitude, physio-chemical properties characterization, mass transfer kinetics evaluation and theoretical simulation. The physio-chemical properties characterization was carried out using various established scientific methods outlined in the thesis. The changes in the physio-chemical properties have significant effects on the mass transfer kinetics of near wellbore remediation process for hydrocarbon production improvement. Thus, laboratory experiments simulating the near wellbore remediation and enhance recovery process using the sonicated nanofluids at various amplitudes under isothermal and non-isothermal were carried out using filter cake dissolution and sand packed column flow tests. Filter cake is a layer formed by solid particles in drilling fluid against porous zones due to differential pressure between hydrostatic pressure and wellbore pressure. The mass transfer kinetics evaluation was established for the experimental work. The experiments indicated that the optimum mass transfer enhancement achieved for this study when the nanofluids sonicated at 60% amplitude under non-isothermal conditions. This condition enables us to produce nanofluids with lowest interfacial tension, viscosity, mean average particle size and contact angle properties. The experimental results for the filter cake dissolution for the best-case scenario was compared with theoretical simulation using Ansys Fluent (version.15). The comparative plot of filter cake dissolution rate for both the experimental and Ansys Fluent simulation showed the best similar correlation trend achieved with the 60% amplitude under the non-isothermal condition. Thus, we could establish a general correlation between the key physio-chemical properties, ultrasonic amplitude, and the mass transfer kinetics during the near wellbore remediation process in the petroleum industry.