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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.
31

Dynamic and Steady State Behaviour of an Extractive Distillation Column

O`Neill, Dwayne L. 05 1900 (has links)
<p>This project was the second part of a long-term study into the control of an extractive distillation unit. A fifteen stage extractive distillation column was re-built and operated over a range of operating levels. Overhead product acetone composition was limited to approximately 0.94 mole fraction acetone due to tray liquid priming. A steady state simulation was developed to aid in a better understanding of the process. Murphree vapour tray efficiencies were adjusted within the simulation to match experimental and simulated product composition results. The simulation was used to accurately predict unfitted experimental results. Dynamic behaviour of the column was studied by relating product composition responses to changes in disturbance and manipulated variables. Dynamic behaviour was analysed by frequency response and real time response fitting. Experimental data was relatively noisy. First order transfer function models with dead time, fitted in the real time domain, were satisfactory.</p> / Master of Engineering (ME)
32

Two-Layer Slot Coating: Study of Die Geometry and Interfacial Region

Taylor, David Shawn January 1997 (has links)
<p>The two-layer slot coating method is commonly used in industry to apply multiple layers of miscible liquids onto a moving substrate. Previous experimental work using a standard flat die face geometry has shown that tiny recirculations exist within the coating bead. Recirculations near the interfacial region may cause convective mixing of the two liquid layers and thus, defects in the final coated material. Previous studies on the interfacial region between the two miscible liquids have assumed that diffusional and convective mixing of the two layers can be ignored and that an 'interface' of zero surface tension exists between the two layers. This work attempts to show that observable mixing does occur between layers of miscible liquid and that the convective mixing can be minimized by changing the geometry of the die face between the two slots.</p> <p>Flow visualizations using particles and two different coloured dyes were performed on the standard square die face geometry. Result show that vortices exist in the coating bead under all the test conditions, either at the downstream shoulder of the die or in the interfacial region near upstream feed slot. The presence of the vortices at these positions, as well as the position of the separation line, was partially determined by the ratio of top layer viscosity to bottom layer viscosity, among other factors.</p> <p>Visualizations were also done using various geometries for the centre block: knife, groove, and bullet referring to the shape of the different blocks. The knife geometry decreased the performance of the two slot coater, causing problems such as oscillations of the upstream meniscus and invasions of the top layer into the bottom layer feed slot. The performance of the groove geometry was very similar to the standard square geometry except for the occurrence of an extra tiny vortex inside the groove itself. The bullet centre block eliminated the vortices in the interfacial region and provided limited control of the region's shape and position.</p> <p>The commercial CFD package FIDAP<sup>TM</sup> was used to simulate a two dimensional Newtonian model of the two slot coating bead under the same operating conditions used in the experiments. Variations in liquid properties across the interfacial region were calculated by defining viscosity as a function of false species concentration, where the isoconcentration contours were then used to define the interfacial region. The simulation showed excellent agreement with the square and groove geometries, and reasonable agreement with the knife and bullet geometries The simulations indicate that a vortex forms in the interfacial region near the upstream feed slot for viscosity ratios of 4:1 to 10:1. The vortex caused convective mixing between the liquid layers for all geometries; however, the mixing was reduced or eliminated by the knife, groove and bullet geometries at a viscosity ratio of 10:1.</p> / Master of Engineering (ME)
33

A Numerical Study of Thermal Buoyancy in Axisymmetric Laminar Vertical Jets

Judd, Ross 09 1900 (has links)
<p>A numerical study of thermal buoyancy in a laminar axisymmetric jet issuing into similar stagnant receiving media is presented. The boundary layer equations governing steady incompressible laminar flow are solved using a finite difference technique developed by Tomich. The results show the predominant effect of positive thermal buoyancy is to increase axial velocity. This effect increases for increasing Prandtl and Grashof numbers. Comparison between the reported numerical solution and the perturbation solution of Mollendorf and Gerhardt shows the latter solution does not adequately describe buoyant flow. Morton's entrainment formulation, on the other hand, is shown to predict the correct scaling factor relating two buoyant flows.</p> / Master of Engineering (ME)
34

Pumping Characteristics of Reciprocating Asymmetric Baffles in a Pipe

Bancroft, Timothy J. January 1975 (has links)
<p>Reciprocating asymmetric baffles in a pipe can produce a time averaged pressure difference and hence can be used to form the basis of a valveless pump.</p> <p>This report describes the production of characteristic curves of head versus flow rate for a range of variables in a 50.8 mm I.D. tube agitated by reciprocated asymmetric baffles. The effect of amplitude and frequency of oscillation on the pumping of tap water is reported. Baffle length and fitting of arifices to the pump are two other modifications considered. The pumping characteristics for two fluids other than tap water, namely glucose and a filter pulp slurry, are also described.</p> / Master of Engineering (ME)
35

The Simulation of and Convergence Studies

Prowse, Richmond Daniel 10 1900 (has links)
<p>The first section of this dissertation is concerned with simulation of the steady state behavior of an industrial multi-component reboiled absorber by two different mathematical models. The formulation of each model, an equilibrium tray and a Murphree tray efficiency model respectively, results in large sets of non-linear algebraic equations which must be solved on a digital computer. The physical property procedures employed to evaluate the parameters in each equation set are discussed and data from converged model studies are quantitatively compared to known plant data. Agreement between predicted and known data is good. The two models are also compared to a simulation model formulated by a previous investigator, Petryschuk.</p> <p>In the second section of this dissertation, the unstable convergence characteristics associated with application of sequential substitution procedures to the solution of absorber model equation sets are discussed. An idealized binary component absorber model was formulated and the convergence behavior associated with application of a modified sequential substitution procedure, block relaxation, to the model equations was analyzed by Jacobian matrix techniques. Several conclusions are presented regarding the interaction between model specifications and physical property parameters and the convergence of the chosen iteration procedure. Further, the convergence of several multi-component absorber models obtained from the literature and of the reboiled absorber model of this dissertation was studied and several conclusions drawn as to the use of the block relaxation convergence technique.</p> / Doctor of Philosophy (PhD)
36

Mass Transport and Chemical Kinetics of Platelot Adhesion to Biomaterials

Brophy, James M. 09 1900 (has links)
<p>The operating procedure for Couette flow apparatus capable of evaluating the thromboresistance (by examination of platelet adhesion) of materials was standardized. It was established that operating at room temperature instead of at the normal physiological temperature, 37°C, did not affect platelet adhesion and that a continued exposure to a shear rate of 19 secֿ¹ for 40 minutes did not damage the platelets. The radioisotope evaluation technique gave consistent results with the direct counting method.</p> <p>Platelet diffusivity in the presence of red cells was found to be one or two orders of magnitude greater than the one predicted by Brownian motion and to be dependent on shear rate and hematocrit.</p> <p>A theoretical model for platelet adhesion was developed for the diffusion limited case and described the experimental data for collagen coated glass.</p> <p>Glass, polystyrene, sulphonated polystyrene and polyurethane reached equilibrium values of platelet adhesion after 2-10 minutes. The equilibrium values of these surfaces were not distinguishable. Albumin coated glass reached an equilibrium value in less than 2 minutes that was substantially lower than the other surfaces investigated. Platelet adhesion to collagen, as predicted by the diffusional model, continued to increase with time.</p> / Master of Engineering (ME)
37

Performance of a Multistage Fluidized-Bed Ion-Exchange Contractor with Fluid-Diode Downcomers

Law, Yiu-Fook Conrad 02 1900 (has links)
<p>A study was carried out on the operational and mass-transfer performance of a multistage fluidized-bed continuous countercurrent ion-exchange contractor with fluid-diode downcomers. For the mass-transfer study, the ion-exchange system Na+/H+ with Dowex-50W-x8 resin was used. The total solution concentration used was 0.06 meq/ml.</p> <p>The fluid-diode downcomer design significantly reduces the bypassing of liquid up the downcomer. Easy start-up and shut-down were observed and the resin was evenly distributed on each mass-transfer stage. The effects of fluid-diode lateral displacement, weir height, weir shape and resin particle size on the operational performance (in terms of liquid-bypassing and resin fluidization) of the solid-liquid contactor were investigated.</p> <p>A one-quarter replicate of a factorial experimental design to 7 factors at 2 levels successfully and efficiently revealed the main factors and interactions which significantly affect the overall stage efficiency of the ion-exchange column operation. The significant main factors are resin feed-rate, process solution flow-rate, weir length and weir height. The significant interactions are between resin feed-rate and weir length, process solution flow-rate and weir length, and weir height and weir length.</p> <p>The mass-transfer study has shown that the solid-liquid contact time in the contactor determines the overall stage efficiency. The composition dependence of the mass-transfer coefficients in both the solid and liquid sides also plays a role in affecting the overall mass-transfer.</p> <p>The relative specific volumes calculated from the experimental results justify further development of the present contactor in the consideration from industrial scale applications. The present type of contactor is simple in design and requires simple control strategy, providing operational stability, and large solid and liquid handling capacity.</p> / Master of Engineering (ME)
38

Emulsion Polymerization of Vinyl Acetate: Particle Size and Molecular Weight Distributions

Keung, John Chue-Kwok 04 1900 (has links)
<p>Emulsion polymerization of vinyl acetate was studied in a batch reactor system. The particle size distribution of the polyvinyl acetate particles was determined by electron microscopy. 'In Situ Polymerization' technique was used to harden the polymer particles before microscopic examination. A light transmission spectrophotometer was calibrated for particle size measurement with the data obtained from election microscopy. A one-parameter exponential function was found to be a good approximation for the polyvinyl acetate particle size distribution. A convenient method which involves the measurement of turbidities at two wavelengths was proposed to determine the particle size distribution.</p> <p>The second part of this thesis deals with the kinetics of vinyl acetate emulsion polymerization. It was found that a rate model similar to Case 1 of Smith-Ewart's theory was able to predict the polymerization rate. A model previously developed in this laboratory was able to predict the molecular weight development in vinyl acetate emulsion polymerization. The logarithmic-normal distribution was a reasonably good approximation for the polyvinyl acetate molecular weight distribution.</p> / Master of Engineering (ME)
39

Stochastic Digital Control of a Continuous Stirred Tank Reactor

Hong, Man Huynh 03 1900 (has links)
<p>A continuous stirred tank reactor is interfaced to a minicomputer and software is written for the different purposes of this study. The model building procedure is based on a three-step iterative approach (identification, estimation and diagnostic checking) using data collected by a minicomputer under open-loop and closed-loop conditions. A stochastic feedback controller is designed from the identified model and implemented using a minicomputer. A comparison run between this stochastic controller and a well tuned PI controller is made. A modified stochastic controller is suggested. The effect of sampling interval on discrete process models is developed, and the optimal choice of sampling interval for digital control is discussed.</p> / Master of Engineering (ME)
40

The Effect of Lime Treatment on the "Soluble" Organics in Domestic Wastewater

Coss, James 12 1900 (has links)
<p>Gel Chromatography has been used in this study to investigate the effect of lime treatment on pure compounds and wastewater samples. Using pure compounds, it was found that porous glass gel, even after coating with carbowax, is unsuitable because of its adsorptive and ion exchange tendencies. With Sephadex gel, proteins and wastewater samples showed a strong dependence on sample inorganic content. While use of an ionic eluant provided consistent elution behavior with proteins and carbohydrates on Sephadex; best elution behavior with wastewater samples was obtained with distilled water eluant.</p> <p>Chemical treatment at high pH of pure compounds revealed that proteins and polysaccharides are not hydrolysed. However, ribonucleic acid is hydrolysed, and some proteins and humic acid can be precipitated from solution. Lime treatment of wastewater has indicated that the removal of "soluble" organics is highly pH and time dependent. Up to 40% organic removal was obtained by precipitation or adsorption mechanisms. Gel filtration analysis of these samples indicated that lime treatment at different pH levels and residence times has a selective effect on organic fractions. Optimum level for turbidity and phosphate removal with lime is roughly pH I I with greater than 80% removal achieved.</p> / Master of Engineering (ME)

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