The utilisation of alternate sources of energy has reached critical levels due to the constantly growing demand for energy and the diminishing of fossil fuels. The production of hydrogen through the Hybrid Sulphur process is a possible alternative that may contribute towards alleviating the pressure on the world's energy resources. The two-step thermochemical cycle for decomposing water into hydrogen and oxygen offers the potential to obtain acceptable thermal efficiencies, while still using common and inexpensive chemicals. The process mainly makes use of two unit process operations: an electrolyser and a chemical decomposition reactor. This research project focuses on the concept design of the decomposition reactor operated adiabatically as a multi-stage reactor system with inter-stage heating, in order to simplify the reactor design. This approach allows for the independent evaluation of the reaction kinetics and the heat transfer mechanism. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2009.

No description available.

A parallel implicit adaptive-mesh-refinement scheme is proposed for the solution of the Navier-Stokes equations as applied to two-dimensional steady-state hypersonic laminar flows in conjunction with an equilibrium high-temperature equation of state. A finite-volume discretization is applied to the governing equations. Limited piecewise-linear solution reconstruction and Riemann solvers (Roe and HLLE, both modified for a general equation of state) are used to evaluate the inviscid fluxes. The gradients in the viscous fluxes are calculated using diamond-path reconstruction. The system of non-linear algebraic equations resulting from the finite-volume discretization are solved using an inexact Newton method with GMRES to solve the update step of the Newton method. GMRES is preconditioned with Schwarz preconditioning with local block-fill incomplete lower-upper factorization. Multigrid and pseudo-transient continuation are used for startup. Numerical results, including flows at Mach numbers of 7.0, are discussed and demonstrate the validity and efficiency of the scheme.

A parallel implicit adaptive-mesh-refinement scheme is proposed for the solution of the Navier-Stokes equations as applied to two-dimensional steady-state hypersonic laminar flows in conjunction with an equilibrium high-temperature equation of state. A finite-volume discretization is applied to the governing equations. Limited piecewise-linear solution reconstruction and Riemann solvers (Roe and HLLE, both modified for a general equation of state) are used to evaluate the inviscid fluxes. The gradients in the viscous fluxes are calculated using diamond-path reconstruction. The system of non-linear algebraic equations resulting from the finite-volume discretization are solved using an inexact Newton method with GMRES to solve the update step of the Newton method. GMRES is preconditioned with Schwarz preconditioning with local block-fill incomplete lower-upper factorization. Multigrid and pseudo-transient continuation are used for startup. Numerical results, including flows at Mach numbers of 7.0, are discussed and demonstrate the validity and efficiency of the scheme.

No description available.

No description available.

Operation of SiGe BiCMOS Technology Under Extreme Environments Tianbing Chen 96 pages Directed by Dr. John D. Cressler "Extreme environment electronics" represents an important niche market and spans the operation of electronic components in surroundings lying outside the domain of conventional commercial, or even military specifications. Such extreme environments would include, for instance, operation to very low temperatures (e.g., to 77 K or even 4.2 K), operation to very high temperatures (e.g., to 200 C or even 300 C), and operation in a radiation-rich environment (e.g., space). The suitability of SiGe BiCMOS technology for extreme environment electronics applications is assessed in this work. The suitability of SiGe HBTs for use in high-temperature electronics applications is first investigated. SiGe HBTs are shown to exhibit sufficient current gain, frequency response, breakdown voltage, achieve acceptable device reliability, and improved low-frequency noise, at temperatures as high as 200-300 C. A comprehensive investigation of substrate bias effects on device performance, thermal properties, and reliability of vertical SiGe HBTs fabricated on CMOS-compatible, thin-film SOI, is presented. The impact of 63 MeV protons on these vertical SiGe HBTs fabricated on a CMOS-compatible SOI is then investigated. Proton irradiation creates G/R trap centers in SOI SiGe HBTs, creating positive charge at the buried oxide interface, effectively delaying the onset of the Kirk effect at high current density, which increases the frequency response of SOI SiGe HBTs following radiation. The thermodynamic stability of device-relevant epitaxial SiGe strained layers under proton irradiation is also investigated using x-ray diffraction techniques. Irradiation with 63 MeV protons is found to introduce no significant microdefects into the SiGe thin films, regardless of the starting stability condition of the SiGe film, and thus does not appear to be an issue for the use of SiGe HBT technology in emerging space systems. CMOS device reliability for emerging cryogenic space electronics applications is also assessed. CMOS device performance improves with cooling, however, CMOS device reliability becomes worse at decreased temperatures due to aggravated hot-carrier effects. The device lifetime is found to be a strong function of gate length, suggesting that design tradeoffs are inevitable.

Gas viscosity is one of the gas properties that is vital to petroleum engineering. Its role in the oil and gas production and transportation is indicated by its contribution in the resistance to the flow of a fluid both in porous media and pipes. Although viscosity of some pure components such as methane, ethane, propane, butane, nitrogen, carbon dioxide and binary mixtures of these components at low-intermediate pressure and temperature had been studied intensively and been understood thoroughly, very few investigations were performed on viscosity of naturally occurring gases, especially gas condensates at low-intermediate pressure and temperature, even fewer lab data were published. No gas viscosity data at high pressures and high temperatures (HPHT) is available. Therefore this gap in the oil industry still needs to be filled. Gas viscosity at HPHT becomes crucial to modern oil industry as exploration and production move to deep formation or deep water where HPHT is not uncommon. Therefore, any hydrocarbon encountered there is more gas than oil due to the chemical reaction causing oil to transfer to gas as temperature increases. We need gas viscosity to optimize production rate for production system, estimate reserves, model gas injection, design drilling fluid, and monitor gas movement in well control. Current gas viscosity correlations are derived using measured data at low-moderate pressures and temperatures, and then extrapolated to HPHT. No measured gas viscosities at HPHT are available so far. The validities of these correlations for gas viscosity at HPHT are doubted due to lack of experimental data. In this study, four types of viscometers are evaluated and their advantages and disadvantages are listed. The falling body viscometer is used to measure gas viscosity at a pressure range of 3000 to 25000 psi and a temperature range of 100 to 415 oF. Nitrogen viscosity is measured to take into account of the fact that the concentration of nonhydrocarbons increase drastically in HPHT reservoir. More nitrogen is found as we move to HPHT reservoirs. High concentration nitrogen in natural gas affects not only the heat value of natural gas, but also gas viscosity which is critical to petroleum engineering. Nitrogen is also one of common inject gases in gas injection projects, thus an accurate estimation of its viscosity is vital to analyze reservoir performance. Then methane viscosity is measured to honor that hydrocarbon in HPHT which is almost pure methane. From our experiments, we found that while the Lee-Gonzalez-Eakin correlation estimates gas viscosity at a low-moderate pressure and temperature accurately, it cannot give good match of gas viscosity at HPHT. Apparently, current correlations need to be modified to predict gas viscosity at HPHT. New correlations constructed for HPHT conditions based on our experiment data give more confidence on gas viscosity.

The High Temperature Integrated Multi-Modular Thermal Reactor is a small modular reactor that uses an enhanced conductivity BeO-UO2 fuel with supercritical CO2 coolant to drive turbo-machinery in a direct Brayton cycle. The core consists of several self-contained pressurized modules, each containing fuel elements in pressurized channels surrounded by a graphite moderator, and Brayton cycle turbo-machinery. Each module is subcritical by itself, and when several modules are brought into proximity of one another, a single critical core is formed. The multi-modular approach and use of BeO-UO2 fuel with graphite moderator and supercritical CO2 coolant leads to an inherently safe system capable of high efficiency operation. The pressure channel design and multi-modular approach eliminates engineering challenges associated with large pressure vessels. The subcriticality of the modules ensures inherent safety during construction, transportation, and after decommissioning. Serpent, a continuous-energy Monte-Carlo reactor physics burnup calculation code, was used to develop a critical configuration of the subcritical modules using UO2 fuel enriched with 5 wt% 235U with a 5 wt% BeO additive. The core lifetime was found to be 14.6 years operating at 10 MWth, though the U enrichment and power can be altered to achieve desired core lifetimes. Negative fuel and moderator temperature coefficients of reactivity were found that could maintain safety during operation. The multi-modular design was found to be beneficial compared to a core with all fuel elements in one module. Batch battery type refueling was found to be beneficial and the feasibility of controlling the reactor was demonstrated through the use of control shells that surround each module. The HT-IMMTR design is an inherently safe, highly efficient, economically competitive, and most important, feasible reactor design that takes advantage of proven technologies to facilitate the demonstration of a successful commercial deployment.

The behaviors of high temperature corrosion on hot-dip aluminized on 9Cr-1Mo and 310 stainless steels when catalyzed by NaCl and cyclic heating environment were studied experimentally. The corrosion behavior and morphological development were investigated by weight gain kinetics, metallographs, depths of attack, metal losses, and X-ray analyses. The results of 310SS deposited with salt mixtures show that weight gain kinetics in simple oxidation reveals a steady-state parabolic rate law after 3 hr, while the kinetics with salt deposits display multi-stage growth rates. NaCl is the main corrosive specie in high-temperature corrosion involving mixtures of NaCl/Na2SO4 and is responsible for the formation of internal attack. Uniform internal attack is the typical morphology of NaCl-induced hot corrosion, while the extent of intergranular attack is more pronounced as the content of Na2SO4 in the mixture is increased. The thermal-cycling test results of 310SS deposited NaCl and coated 7wt%Si/93wt%Al show that the aluminized layers have good corrosion resistance during the first four cycles of testing, while degradation occurs after testing for five cycles. The reason for degradation of aluminized layers is attributed to the formation of interconnecting voids caused by aluminum inward diffusion, chloridation/oxidation cyclic reactions and the penetration of molten NaCl through the voids into the alloy substrate. The 9Cr-1Mo steels coated with 7wt%Si/93wt%Al oxidized at 750, 850, and 950°C in static air show that oxidation kinetics followed a parabolic rate law at 750 and 850 °C. The cracks propagated through the FexAly layer due to the growth of brittle FeAl2 and Fe2Al5 at 750 and 850°C. The voids condensed in the interface of intermetallics and substrate are attributed to the Kirkendall effect. At 950°C, the fast growing aluminide layer has a different expansion coefficient than oxide scale, leading to scale cracking, oxygen penetration, and internal oxidized, evidenced by a rapid mass gain.