Chemical and Biomolecular Engineering - Theses

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    An investigation of the compression moulding and extrusion of polyethylene foam
    Buczma, Eugene ( 1979)
    The processes of compression moulding and extrusion of polyethylene foam using chemical blowing agents were investigated. Both high and low density polyethylenes together with the chemical blowing agents azodicarbonamide, Porofor S-44, 4,4'-oxybis(benzenesulphonyl hydrazide) and N,N'-dinitrosopentamethylenetetramine were used. The same mechanisms were found to be operative in both processes. The nucleation of cells was related to the decomposition of the chemical blowing agent used. Secondary nucleation of the diffusing gas was effected by the use of a very fine particle size silica. The processes of gas diffusion and gas dissolution in the melt were shown to be important in explaining the cell structure obtained. These were related to gas sorption studies. Very fine cellular structures could be obtained by compression moulding by using fast heating and cooling cycles. This reduced diffusion resulting in low foam density and fine cell size. The dielectric constant of the foam was related to foam density by the use of mixture formulae. Tensile properties were found to be dependent on cell size and, foam density.
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    The sorption of ammonia on brown coal
    Oussa, Awad Rizk ( 1978)
    This thesis is a report of an investigation carried out by the author between 1st April 1969 to 31st October 1973 on a full time basis and from 1st December 1975 to 31st July 1978 on a part time basis. The research project was conducted by the author in the Department of Chemical Engineering, University of Melbourne, and on the premises of Australian Char Pty. Ltd., Morwell. The project was based on the premise that useful information on the brown coal-ammonia system can be obtained from sorption isotherms. The author designed and assembled the apparatus with this in mind, and developed a method of obtaining a self-consistent and meaningful interpretation of the sorption isotherms. Thermodynamic data for the ammonia sorption process was derived and used to develop a preliminary model for the ammonia-brown coal system. No separate literature review has been presented in the thesis, though frequent reference to the literature has been made in the discussions in each chapter. Finally, the experimental details have been included in the appendices at the end of the thesis.
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    The effect of return bends on the heat transfer from an internally flowing turbulent air stream in smooth tubes
    Batterham, Robin John ( 1968)
    The aim of the project was to investigate the effect of an 180° bend on the heat transfer from an internally flowing turbulent air stream. The presence of a bend was shown to increase the local heat transfer rate in the bend and in the upstream and downstream regions of the bend. (For complete summary open document)
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    Gas bubble behaviour in liquid systems
    La Nauze, Robert David ( 1972)
    The formation phenomena of carbon-dioxide bubbling into water through 1/16”, 1/8” and 3/16” diameter orifices was recorded photographically for gas flow rates between 1 and 30 cm3/s for system pressures up to 300 psig. It was shown that for the same volumetric flow rate, determined at system conditions, increased system pressure causes smaller but more frequent bubbles to be formed. Bubbling at high mass flow rates is characterised by a large degree of interaction and coalescence near the orifice. A detailed analysis of mathematical models of the formation process was undertaken. This study highlighted fundamental inadequacies in an existing two stage growth model. A more realistic model of formation was developed which included terms for the inertia of the liquid surrounding the bubble and the gas momentum. Within the constraints of a single bubble analysis, the model shows good agreement with the experimental results for volume and flow rate and predicts the correct trend for frequency and pressure fluctuations across the orifice. The influence of liquid circulation on bubble growth at high system pressure is discussed and several theoretical approaches to the problem have been outlined.