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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A computer simulation model of seasonal transpiration in Douglas-fir based on a model of stomatal resistance /

Reed, Kenneth Lee, January 1972 (has links)
Thesis (Ph. D.)--Oregon State University, 1972. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.
2

Simulation decision aid for power station configuration evaluation

Elliott, Kevin A. 02 March 2015 (has links)
M.Tech. / In life extending and refurbishing old power station plant, the following question must be addressed: Does one maintain current configuration, which was based on the technology of 1960, or make use of current power utility technology trends, and change the power station's configuration. This specific problem involves four existing Eskom power stations, with an approximate combined replacement value of R7 billion. All these stations have the capability of using a common steam feed range to supply superheated steam to the turbo-generator sets. This common steam feed range becomes very maintenance intensive in its "old age". Hence the need for this study into the feasibility of its refurbishment. This common steam feed range configuration was considered state-of-the-art in the mid-1900's, but is currently not the practised technology. This is primarily due to the technology advancement into reheat boilers, making control of a range type configuration impossible. Monte Carlo simulation provides an effective, holistic decision mechanism, that is free from bias, emotions and conjecture. Hence the simulation product, highlighted in this dissertation, will have solved an industrial problem finally and effectively, by ensuring that for a relatively small cost of building the simulation models, major capital expenditure estimates can be accurate, with a confidence in the return on investment. This paper discusses the use of Monte Carlo simulation modelling as an engineering analysis tool, for the analysis of two power station configuration options, i.e. with a steam feed range and without. Firstly, an investigation into the selection of which computer language to use as a development tool is presented. The Monte Carlo simulation technique is then explained, and simulation models are built of the two power station configurations. The models, which are built using SIMSCRIPT 11.5 simulation language to represent the real world in each configuration option, are then discussed. The availability analysis is developed, and conclusions and recommendations are discussed, as presented in the report to Eskom Management.
3

Hydraulic modelling of a horizontal subsurface flow constructed wetland

Bonner, Ricky January 2016 (has links)
A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 2016 / Horizontal subsurface flow constructed wetlands (HSSF CWs) are being considered in South Africa as an alternative waste water treatment technology which is low in capital costs and typically requires less operational infrastructure when compared to conventional treatment technologies. HSSF CWs may thus be a potential solution for solving the challenge of ensuring reliable access to clean water for rural communities whose municipalities may not be able to afford the construction of a waste water treatment plant as well as not being able to supply sufficient technical expertise for the operation thereof. Proper design of HSSF CWs requires a detailed investigation into the hydraulic behaviour as it has a direct effect on the treatment performance in these systems. In this study, three available hydraulic modelling methodologies for HSSF CWs were compared and these are the impulse, step change integral and step change derivative modelling methodologies. Hydraulic data were generated from planted and unplanted pilot scale HSSF CWs using residence time distribution (RTD) studies and the modelling results using each methodology were compared. It was found that each methodology was capable of suggesting a different hydraulic behaviour for the same system being studied and since it is not possible to evaluate an analytical answer to the problem independently it was not possible to determine which modelling methodology was the most accurate. Practical limitations of the experiments used to feed hydraulic data to the respective methodologies were also highlighted. Despite a well-designed sampling regime it was not possible to capture sufficient data surrounding the peak of the impulse response curve and may have impacted negatively on the modelling results. No such difficulties were encountered with the step change tracer experiments. The mathematical techniques which each methodology employs were also critically assessed. It was found that numerical differentiation in the step change derivative modelling approach introduced noise into the RTD curve and may have affected subsequent results. Ultimately each methodology has its own associated strengths and weaknesses and choice of methodology may be dictated by other factors such as cost to set up the hydraulic experiment as well as equipment availability. Tasks two and three of this dissertation dealt with how Biomimicry can be used as a tool to develop more sustainable HSSF CW designs and hydraulic modelling processes. In task two, hydraulic data generated from the first task were used to develop estimates of the velocity profiles inside a planted HSSF CW to identify regions most prone to clogging, a phenomenon which would be a serious concern for rural communities whose sole water treatment system would be the CW. Biomimetic design principles were combined with the modelling results to develop a modular system design allowing for sections of the CW to be removed for cleaning while still allowing for continuous treatment of the waste water. Task three explored the use of heat as a hydraulic tracer. Heat is considered more environmentally friendly when compared to chemicals as tracers as the CW can equilibrate to ambient conditions post study and the effluent does not require dedicated disposal infrastructure. Heat is non-conservative in these systems and processes such as absorption by the subsurface media and loss to the surroundings distort the hydraulic response curve from which the hydraulic behaviour cannot be directly obtained. In this study a mathematical model was developed which maps a heat tracer response curve to one which would be obtained if a conservative chemical tracer were used. It was tested by conducting a combined heat-chemical tracer study on an unplanted laboratory-scale HSSF CW and the predicted chemical response curve was compared with the actual experimental response curve. The model performed satisfactorily indicated by a 5% and 6% relative difference in the Peclet number (Pe) and mean of the RTD respectively. In each of these chapters, an abstract is provided which summarizes the main findings of the study. / MT2017
4

Modeling and simulation of a drum boiler-turbine power plant under emergency state control.

Usoro, Patrick Benedict January 1977 (has links)
Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / M.S.
5

THE ECONOMICS OF GAS TURBINE COGENERATION.

SMITH, STEPHEN EDGERLY. January 1982 (has links)
The technology of cogeneration is reviewed through an examination of the prime movers most commonly used for this purpose in industrial and commercial facilities. The systems characteristics which are of particular importance to the congeneration application are emphasized along with the advantages and limitations of each. A comparative examination of the methods selected for use in the evaluation of profitability in cogeneration systems is presented. The examination focuses on the interpretation of the projections made by each method and their implications for the decision to adopt cogeneration. A computer simulation model is utilized to perform a sensitivity study in order to identify the key variables determining economic viability of cogeneration. Employing a gas turbine system as a representative installation, the variables used in the sensitivity study are presented along with the justification for the assignment of the baseline and study range values. A simplified method for analyzing the profitability of cogeneration systems is developed. The technique is specifically tailored to gas turbine based cogeneration which is the technology most commonly proposed for moderate size facilities. The significance of the incremental energy consumption factor as a determinant of profitability is investigated. The application of the simplified method for comparative studies of different gas turbine systems is described and the results compared to projections made by the simulation model. Finally, the simplified method is utilized to examine the implications of regional fuel price differences and the implications of natural gas price deregulation on the profitability of gas turbine cogeneration.

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