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ABSTRACT Glass fiber reinforced polypropylene pipes were fabricated from 6-10 layers of “Plytron” GN638T 25mm wide glass fiber pre-impregnated polypropylene tapes using filament winding/tape laying process, in-situ consolidation on a 1000mm long mandrel. Infrared heater and heat gun were used in heating the incoming tapes and the substrate at the nip point. The effects of process pressure and temperature on the mechanical properties were investigated by testing samples of test laminates and fabricated pipes for their mechanical properties. Results indicated that the mechanical properties of the test samples and pipes were affected by changes in process temperature and pressure, with an optimum process pressure and temperature being 16.8KPa and 2800C respectively. The cost analysis of the fabricated pipes indicated that the materials and method of production employed in this research could be utilized to an economic advantage when compared with the prices of the same type of pipes in SA market.

The accurate prediction of pipe contraction pressure loss is important in the design of pipe system such as heat exchangers, particularly when close control of the flow distribution in a network of pipes is required. The prediction of contraction pressure loss depends heavily on experimental data. Large discrepancies in these predictions are evident in the literature. Experimental results giving pres!? re loss coef fici ents for a range of Reyno 1 ds numbers of 4x 10 -2x 10 and area ratios of 0.135 - 0.692 are presented and compared with predictions from a method developed that allows for velocity profile variation through the contraction. The results show a Reynolds number dependence and good agreement between predicted and measured values. It is also important to be able to predict the variation of pressure loss coefficient with variations in the small-bore inlet geometry, referred to as the inlet sharpness. There are no know experimental data for the effects of inlet sharpness on the pipe contraction loss coefficient, but there are data for intakes set flush in a plane wall which are used as approximations. Experimental data showing the variation of pressure loss coefficient with inlet sharpness up to 13.4% are presented and compared with approximate data. The comparison shows significant differences. A three beam laser doppler anemmeter has been used to measure the detailed flow field for an area ratio of 0.332 and a Reynolds number of 153.8 x 10. The mean velocity, turbulent intensity and Reynolds stress distributions are presented for twenty-two axial stations between four large-bore diameters upstream to fourteen small-bore diameters downstream of the contraction. These experimental measurements are compared with computer predictions using the FLUENT code with the k-e- turbulence model. The general trends in the flow are predicted, however there are significant differences in the detailed flow field which are highlighted.

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Current water-cooling technology used in the metallurgical industry poses a major safety concern. In addition, these systems are expensive to operate and result in significant energy losses. / The purpose of the research presented in this thesis was to develop a viable cooling system based on novel heat pipe technology which addresses these problems. This technology employs boiling as the means to store and transfer heat energy. The large heat extraction capacity of the device is owed to two design features: firstly, a separate return line that generates a column of liquid working fluid which drains into the evaporator by gravity, and secondly, a helical flow modifier in the evaporator that stabilizes annular two-phase flow. / A full-scale copper tapblock and launder were designed with water-based heat pipe cooling systems. These systems were successfully tested under industrial heat loading conditions, using a gas burner to simulate the heat loads. / The tapblock cooling system was able to dissipate 142 kW per heat pipe, at heat fluxes as high as 2.4 MW/m2. These values are the largest to date using the novel water-based heat pipe technology. The launder system was the first to incorporate horizontal heat pipes, as well as have multiple evaporators feeding a single condenser. / The cooling systems used in both experiments were fundamentally safer than watercooling systems, being operated at low pressures and with only several kilograms of water exposed to the heat source. The cooling water requirements of these systems represent a reduction of 80-95% compared to conventional water-cooling, with increased potential for energy recovery. / During the testing, dry-out and film boiling were identified as the main limitations. It was found that film boiling occurs when the flow in the evaporator is not great enough to generate a helical motion. The dry-out limitation was achieved when the velocity of the flow within the evaporator was too great, causing a large pressure gradient that opposes the gravity head of the return line. / Both of these limitations are related to the configuration of the evaporator, i.e. the return line and the flow modifier. A methodology was developed to model the evaporator numerically using computational fluid dynamics. This methodology can be used to understand how the design parameters of the evaporator affect the flow patterns during operation.