Faculty of Engineering
http://hdl.handle.net/10646/1378
2017-03-27T00:38:26ZInvestigation of the physical and chemical stability of biodiesel produced from Jatropha Curcas Species in Zimbabwe
http://hdl.handle.net/10646/2829
Investigation of the physical and chemical stability of biodiesel produced from Jatropha Curcas Species in Zimbabwe
Shonhiwa, C.S.; Nhamo, L.M.N.; Kugara, J.
Jatropha curcas L. seeds as a raw material for biodiesel production are a rapidly growing interest over the world because of their high oil content, ecological adaptability, and excellent fuel properties. Though there is an increase in productivity of biodiesel, showing solution for future energy insecurity, there still remains some concern for commercialization due to its susceptibility to degradation during long term storage. The aim of this research work is to investigate the effect of temperature and ambient condition on Jatropha biodiesel storage. A study was conducted for a period of 12 months, where Jatropha biodiesel samples were stored at different temperatures (4°C, 25°C, and 35°C) and environmental conditions (darkness, light, and air). At regular intervals, the samples were taken out to analyze acid value, density, kinematic viscosity, and fatty acid profile to monitor the quality of biodiesel. Analysis showed that acid value, density, kinematic viscosity, and fatty acid content increases with the increase in storage time of biodiesel samples. However, Jatropha biodiesel stored at 35°C, in contact with ambient air and light showed highest degradation compared to that which was stored at 25°C and 4°C. Among all the parameters studied, high temperature and air exposure are the two most important parameters which accelerate the degradation process. Light exposure had mild but significant effect on Jatropha biodiesel degradation over a long storage period.
2016-02-01T00:00:00ZA procedure for sizing pump-pipe systems with regard to minimising life cycle costs manageable on excel spreadsheets
http://hdl.handle.net/10646/2828
A procedure for sizing pump-pipe systems with regard to minimising life cycle costs manageable on excel spreadsheets
Hove, T; Mushiri, T
Pump-pipeline systems are a common feature of every industry and account for about 20% of the world’s electrical energy demand. Pump and pipe selection should happen simultaneously in pump-pipe system design rather than first sizing the pipe and then finding the pump to go with the pipe. Further, proper selection of systems should go beyond just considering only the initial cost but the total cost of ownership- the life cycle cost (LCC). In this paper a spreadsheet tool is developed for pump-pipe system technical analysis with the output design parameters facilitating LCC analysis. The program can calculate the operating point of any size of pump, at any given speed and with any pipe size and by use of appropriate cost models determine the unit cost of pumping for each system. Dimensionless pump characteristic curves that are generic for all radial flow pumps are modelled by multi-polynomial equations. Dimensional similitude can then be used to determine the actual characteristic curves for any pump of given impeller diameter and rotational speed. The system resistance curve is calculated from well-known hydraulic formulae and represented by a quadratic equation. The operating point of the pump-pipe system is obtained from a simultaneous solution of the quadratic equations representing the pump and the pipe resistance curves. Best practice technical constraints, like maximum deviation from best-efficiency point (BEP), allowable net positive suction head and maximum allowable operating hours, can be set by the designer. Operating the pump-pipe system near best efficiency point is desirable since it reduces both energy and pump maintenance costs. A pump-pipe system is selected only if it falls within designer-specified best practice constraints. The life cycle cost of each system that passes the first test is then calculated using discounting techniques and the pump-pipe system with the least LCC is adopted.
2016-02-01T00:00:00ZMechanical thermal stresses and creep analysis of boiler tubes
http://hdl.handle.net/10646/2827
Mechanical thermal stresses and creep analysis of boiler tubes
Mushiri, T
The boiler tubes are operated continuously at high temperature and pressure. Hence at high pressure for forces acting on the boiler tubes will be high. This research paper focuses on the analysis of one of the long term effect of continued application of high pressure on boiler tubes which causes creeping. By utilizing finite element modelling software, AUTODESK INVENTOR the effect of pressure with the increase in temperature distribution across the steam generator tube was evaluated. The increase of heat transfer rate across the wall caused the oxide scale thickness to grow more rapidly than normal condition. The thermal conductivity in the boiler tubes, life of boiler tubes and creep damage is also analyzed in this research paper. The AUTODESK INVENTOR result is analyzed to determine the main and interactive effects of operating conditions. The effect of steam on boilers and creep damage in comparison with temperature were researched. Optimum condition identification in order to maximize the remnant life of the tubes while minimizing the creep damage was done. Creep is the time dependent deformations that occur when a material is subjected to high level of stresses at elevated temperature for prolonged period. Matlab was also used to analyse how the failure occurs.
2016-02-01T00:00:00ZImproved flood estimation model for bridge and culvert design in Zimbabwe
http://hdl.handle.net/10646/2826
Improved flood estimation model for bridge and culvert design in Zimbabwe
Mamombe, L; Tumbare, M. J.
Economics and risk minimization in the design of infrastructure that is vulnerable to flood damage often prove to be non-commensurate objectives. To economically minimize the risk of hydraulic failure of this type of infrastructure is a noble design objective. The hydraulic design of bridges and culverts in Zimbabwe is currently hinged on empirical algorithms of flood estimation. In a changing climate and changing land use environment, the current flood estimation method seems to under-estimate the design floods as evidenced by the increasing number of bridges and culverts being overtopped by floods. This paper discusses the several shortcomings of the current method in use and proposes a new consistent but robust computerized method of flood routing based on historical flow data and statistical analysis techniques. The methodological praxis and resultant design software are intended to substantively improve the flood estimation process, producing a more precisely estimated design flood. From the results obtained, the proposed new model is more conservative than the current method used by the Ministry of Transport (MoT) by an average factor of 1.4. At ungauged sites, or at sites where the stream flow data is inadequate in quantity and quality for Flood Frequency Analysis (FFA), it is recommended that a factor of safety of 1.4 be applied to MoT current flood estimates.
2016-02-01T00:00:00Z