No description available.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2010 / Development of safe storage for reactive combustible materials to prevent possible human and environmental hazards as well as ensure and enhance industrial safety can significantly benefit from mathematical modelling of systems. In the recent past, models with varying degrees of sophistication have been developed and applied to the problem of predicting thermal criticality conditions, temperature and concentration profiles of such system. In this thesis, a model showing the temperature history of an nth order exothermic oxidation reaction in a slab of combustible material with variable pre-exponential factor, taking the consumption of the reactant into account in the presence of a convective heating and oxygen exchange at the slab surface with the ambient is presented Both transient and steady state problems are tackled The critical regime separating the regions of explosive and non-explosive paths of a one step exothermic chemical reaction is determined The governing nonlinear partial differential equations are solved numerically by method of lines (MOL), with finite difference schemes used for the discretisation of the spatial derivatives. Moreover, both fourth order Runge-Kutta numerical integration coupled with shooting methods and perturbation techniques together with a special type of Hermite-Pade series summation and improvement method were employed to tackle the steady state problem. The crucial roles played by the boundary conditions in determining the location ofthe maximum heating were demonstrated. In chapter one, the relevant applications together with previous published work on the problem were highlighted The basic mathematical theory and equations needed to tackle the problem were derived in Chapter two. In chapter three, the transient model problem was formulated, analysed and discussed. The steady state problem was formulated and solved in Chapter four. Furtherwork and concluding remarks were highlighted in Chapter five.

D.Ing.

M.Tech. / The study presented, investigated the acid leaching behavior of calcines emanating from conventional roasting and microwave assisted roasting of sulphide ores. The aim was to investigate a possible change in the mineral composition of the calcine produced and to investigate the leaching behavior of the calcine produced by conventional and microwave assisted roasting. Two sulphide concentrates were received, pyrite concentrate from OTJIHASE concentrator and sphalerite concentrate from ZINCOR. The mineralogical study was done using the XRD (PANalytical X-PertPro X-Ray diffractometer) to determine the mineral composition of the concentrate and the head grade of each concentrate was determined with an Atomic Absorption Spectrometry (AAS) machine for copper, iron and zinc. The concentrates were wet screened at 500, 355, 212, 150, 106 and 75 μm screens for size distribution and for the purpose of the study it was required that 80% of concentrate should pass the 75 μm screen since after roasting, the calcine obtained were to be acid leached. Conventional roasting was carried out at temperatures of 500oC, 700oC, 850oC and 1000oC at durations of 5min, 10min, 20min, 30min, 1hour and 2hours, while microwave assisted roasting carried out at powers of 200W, 400W, 600W, 800W and time intervals of 3s, 10s, 30s, 30min and 1hour

No description available.

Friction stir welding is a relatively new joining process. The heat transfer involved is crucial in determining the quality of the weld. Experimenrtal data, though important, does not provide enough information about the heat transfer process and experiments can be costly and time consuming. A numerical model, using the finite element method, was developed to stimulate the heat transfer in the workpiece in which the heat generation due to friction and plastic deformation was modelled as a surface heat flux boundary condition. This model was applied to Aluminium AL6082-T6 and Titanium Ti6A1-4V for different welding condiitions. Results were validated with experimental results. The model was shown to give better predictions of the maximum temperatures at locations in the workpiece than the overall temperature trend. A parametric study was also performed on the Aluminium model in order o predict temperature fields of the workpiece for welding conditions that were additional to those undertaken experimentally. It was found that rotational speed had a larger effect on the change in temperature than the feed rate. From the parametric study it was also clear that lower rotational speeds (300 to 660 rpm) had a greater effect on the change in temperature than the higher rotational speeds (840 to 1200 rpm). It was concluded that the model was well suited for the estimation of temperatures involved in the FSw of Aluminium Al6082-T6 but was not as accurate when applied to the FSW of Titanium.

An experiment was designed and carried out on the fundamental, but poorly understood problem of oscillating flow past a single, transverse, circular cylinder. This is an approximation of the flow about a single element in a matrix-type regenerator used in Stirling-cycle engines. The experimental rig was designed and built to allow tests to be carried out for the wide range of fluid flow parameters characteristic of various Stirling engines. The influence of these parameters on convective heat transfer rates was measured so the approximate effects of these same parameters on a Stirling engine regenerator could be determined. The main conclusion from the experiment was that average Nusselt numbers, based on test-cylinder diameter and subject to flow conditions similar to those found in Stirling engine regenerators, were 40 to 80% higher than those predicted by a steady flow correlation, for a given Reynolds number. This may be due to the high levels of turbulence generated near the test-cylinder. A secondary conclusion is that the compression and expansion of the working fluid due to a 90 degree phase angle difference between the motion of the pistons raises convective heat transfer rates from the test-cylinder substantially over the 180 degree phase angle, or "sloshing" motion case. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

A two-phase experimental loop was designed and built to simulate the operating conditions of the SLOWPOKE reactor. Void growth was measured for both upflow and downflow for velocities between 0.07 to 0.46 m/s and at a pressure of 155 kPa. The buoyancy effect causes the Onset of Significant Void, OSV, to occur at higher subcooling for downflow than for upflow. This effect is maximum close to the bubble rise velocity (0.23 m/s) and decreases at higher velocities. The results indicate that bubble detachment is not the only critical parameter affecting OSV. The OSV correlations from the literature did not predict the experimental results well. Investigation of the heat transfer mechanisms indicates that fully developed sub cooled boiling occurs prior to OSV. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The main task of this diploma thesis is a draft design low-regenerative feedwater heater. There is conducted thermal and hydraulic calculation of this device. After that there is detaily described the method for controlling the temperature of the outlet water. Conclusion includes calculations for sizing wall thickness of the main tires. Projection drawing is part of the work as a supplement.

This research has a small portion focused on interior serpentine channels, with the primary focus on improving the effectiveness of the film cooling technique through the use of a new approach to film cooling. This new approach uses a set of three holes sharing the same inlet and diverging from the central hole to form a three-legged, or tripod, design. The tripod design is examined in depth, in terms of geometric variations, through the use of flat plate and cascade rigs, with both transient and steady-state experiments. The flat plate tests provide a simplified setting in which to test the design in comparison to other geometries, and establish a baseline performance in a simple flow field that does not have the complications of surface curvature or mainstream pressure gradients. Cascade tests allow for testing of the design in a more realistic setting with curved surfaces and mainstream pressure gradients, providing important information about the performance of the design on suction and pressure surfaces of airfoils. Additionally, the cascade tests allow for an investigation into the aerodynamic penalties associated with the injection hole designs at various flow rates. Through this procedure the current state of film cooling technology may be improved, with more effective surface coverage achieved with reduced coolant usage, and with reduced performance penalties for the engine as a whole. This research has developed a new film hole design that is manufacturable and durable, and provides a detailed analysis of its performance under a variety of flow conditions. This cooling hole design provides 40% higher cooling effectiveness while using 50% less coolant mass flow. The interior serpentine channel research provides comparisons between correlations and experiments for internal passages with realistic cross sections. / Ph. D.