3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item A simplified model for spontaneous combustion in coal stockpiles(2009-11-09T12:12:19Z) Brooks, Kevin SethItem The lightning transient behaviour of a driven rod earth electrode in multi-layer soil(2007-03-07T13:11:44Z) Nixon, Kenneth JohnThe work presented extends and contributes to research in earthing and lightning protection and focuses on the transient behaviour of a driven rod earth electrode. Although previous work in this area has produced practical guidelines and models that may be used for lightning protection system design and analysis purposes, there has not been an investigation into the commonly encountered scenario of multiple layers of di erent soil types, particularly where high current densities cause ionisation to occur in the surrounding soil. In the research presented, the behaviour of a practical driven rod earth electrode subjected to peak impulse currents of up to 30 KA is analysed. Measurements obtained using a large-scale experiment arrangement are compared against results obtained using a time-domain circuit model simulation. It is shown that a single apparent resistivity value calculated from the steady state resistance equation and the measured steady state resistance can be used as a simpli cation for modelling the lightning current transient behaviour of a driven rod earth electrode in multi-layer soil. This represents a unique and valuable contribution to engineers working in the eld of earthing and lightning protection.Item Effects of a simulated slag phase on mixing and mass transfer rates in a creusot-loire uddeholm converter model(2006-10-31T10:38:14Z) Chaendera, AdmireAn experimental study of the effects of a slag phase on mass transport in a onefifth water model of a 100ton CLU-converter was conducted. The study was a follow up to earlier investigations conducted in the absence of a simulated slag phase. Kerosene (10% by volume) was used to represent the slag phase in the cold model experiments. The presence of a slag phase increased the mixing time of a tracer solution in the bath. The mixing time, defined at 99.66% bath homogeneity, was found to increase with bath height and a lowering gas flow rate. The functional relationship, Tmix = 4.39Q-0.73W0.24H1.12, was established as expressing the effect of gas flow rate (Q), bath weight (W), and bath height (H) on the mixing time (Tmix). The mixing time increased by an average of 16.3% after slag inclusion. The mass transfer parameter [(Reloc,r)0.25(Ret)0.32] values obtained in the absence of a slag phase decreased by an average of 32.2% with slag inclusion. Calculated mass transfer coefficients increased with gas flow rate and a decrease in bath height. The relationship, K Q0.08, showing derived mass transfer coefficient (K) dependence on the gas flow rate (Q) was established. The proportionality constant in the equation was observed to vary with bath height, gas flow rate and sample location. Contour maps representing variation of mass transfer coefficients in the bath regions were produced.