Thesis (Ph.D.)--New Mexico State University, 2007. / Adviser: N. Nirmalakhandan. Includes bibliographical references.

Thesis (Ph.D.) - University of Glasgow, 1985. / BLL : D80152. Ph.D. thesis submitted to the Department of Mechanical Engineering, University of Glasgow, 1985. Includes bibliographical references. Print version also available.

Thesis (Ph. D.)--University of California, Santa Cruz, 1993. / Typescript. Includes bibliographical references (leaves 214-226).

Master-Arbeit Univ. St. Gallen, 2005.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, Cape Town, 2007 / An investigation was performed into a new desalination plant operating on the principles of distillation through the utilisation of solar energy only. The need for such a system is due to the high energy requirements of current large scale desalination systems and that, in the future, more and more desalinated water will be required to sustain life in certain areas. A conceptual design of such a plant was completed and it proved its feasibility by providing an in depth explanation of the principles that govern its operation. A computer model, in the form of a MathCAD program, was developed to simulating this process flow. The accuracy of the program was investigated with the help of a pilot plant. It is shown that such a full scale plant would produce, in the region of Saldanha Bay, a town on the Western Coast of South Africa, 5000m3 ofpotable water a day with a solar absorption/evaporation area of 1,87knlrequiring only 1,75kWh per cubic meter of water produced. Its electrical energy requirements can be provided using solar panels allowing the plant to remain independent of external electrical supplies. This electrical energy requirement is less than 33% of the least energy intensive alternative method, reverse osmosis. Since the production rate is dependent on the absorption/evaporation area the plant can be scaled to fit the specific production rate required.

Cartas al editor

The salt expulsion caused by the freezing of seawater and the drainage of brine from the ice creates a convectively mixed layer, which extends to the bottom in shallow coastal regions. This buoyancy flux at the surface was simulated in laboratory experiments by percolating salt water through a porous membrane into a tank. Shadowgraph images show that a down-slope flow is induced when the bottom of the tank is set at an angle. Velocity maxima in the slope flow, measured from the movement of injected dye ranged from 0.09 to 0.66 cm/s. Fluid densities were determined using thermistors and small-volume conductivity micro-cells developed for this purpose. For bottom slope angles between 2.2° and 5.5°, and at computed salt fluxes between 1.82★10⁻⁵ and 1.63★10⁻⁶ g/cm²/s, the salinity profiles showed slope flow depths between 7 and 17 mm with a rise in salinity of 0.24 to 0.92 ppt above those in the mixed layer. Entrainment at a density interface without shear, using this experimental arrangement, agreed closely with predicted results by Bo Pedersen. Using the entrainment model for a turbulent gravity current, entrainment factors computed from the data of the slope flow experiments were up to two orders of magnitude larger than those predicted for flows in a quiescent environment. This is contrary to visual evidence of the experiments or to Arctic field data, which indicate low rates of entrainment. This suggests that a different model is required to explain the interaction between such flows and the turbulent environment. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Cyclic electrodialysis is a novel separation process in which a modified membrane stack is operated in a periodic unsteady-state manner. Repeated reversals of polarity could avoid the main problems encountered in conventional electrodialysis; fouling and scale formation on the membranes. In cyclic electrodialysis the standard electrodialysis stack is converted into an adsorption-desorption stack with only one set of flow channels, the other set being replaced by storage compartments. Thesr compartments are in the form of three-layer membranes consisting of an anion and a cation selective membrane enclosing a core of non- selective material. The depleted and enriched products are produced successively in the single set of channels instead of simultaneously in adjacent channels. The process is potentially applicable for commercial desalination of brackish water to make it potable, to remove harmful ions from discharge waters, or to concentrate ionic solutions for recovery of valuable materials. Previously reported experiments with aqueous NaCl solutions in a closed (batch) system showed that a large separation factor could be obtained in cyclic electrodialysis. Batch operation is somewhat analogous to total reflux in distillation. The present work extends the earlier work to potentially more useful operating conditions in which feed is supplied and product removed. A constant-rate model has been developed for the process and used extensively throughout the work as a simple and efficient tool to compare various operating cycles and modes of operation. Scattered articles in the literature on the resistance of an electrodialysis stack have been compiled to develop a stack resistance model. Good agreement was obtained between the model predictions and measured values of resistance. Experimental apparatus is described and the effects of the following eight system parameters are reported: (i) Demineralizing path length (ii) Production rate (iii) Pause time (iv) Applied voltage (v) Initial concentration (vi) No-pause operation (vii) Pure-pause operation (vii) Semi-symmetric operation Large separations were achieved for asymmetrical paused operation with long demineralizing path, long pause time, high applied voltage, low feed concentration and small production rate. Despite the strong trade-off between production rate and separation, a separation factor as high as 50 was obtained at the highest production rate used. This value is higher than that obtained in commercial plants currently in use. The process looks promising and is worth further consideration. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

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