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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.
21

Control of emulsion drop production in flow focusing microfluidics

Kim, Haejune 15 May 2009 (has links)
Generating droplets using flow-focusing microfluidics in multiphase flows has reached its limit that it cannot generate submicrometer droplets in size. Flow focusing geometry together with an electric field has been used to make smaller droplets in microchannels. The droplet size was controllable by the flow rate ratio as well as the electric field. The droplets size decreased as the voltage increased. A Taylor cone was formed to generate very fine droplets which were less than 1mμ in diameter. The tip made smaller droplets due to the tangential force by the electric field. A small inner flow rate and high electric field were required to form a stable Taylor cone in a DC electric field. The droplet size, however, was not stable at a small water flow rate because the flow rate was not as accuate as required. When I used a modified syringe pump with more accurate flow rate control, I was able to obtain a stable set of data. A small change in droplet size occurred at low voltage. The drop size changed dramatically, when the voltage was high enough. I also observed how an AC electric field affects the droplet size. The droplet size was not solely determined by the voltage. This is because of the imbalance of the supplied flow rate and the emitted flow rate. I also found that the droplet size is related to the tip position of the dispersed phase. The droplet size decreased as the tip stretched more. Typically, the microfluidic device generated monodispese droplets in narrow size distribution. It also generated a bigger droplet followed by a smaller one consecutively at low flow rate ratio of inner and outer fluid flow ()265.0/09.0≤≤oiQQ. To understand this instability of drop formation, a numerical calculation was conducted. The simulation results showed inside of the tip still pointed downstream after it generated a big droplet. Then, the tip generated another smaller droplet while the tip was stretched. Finally, the tip moved back and began a new cycle.
22

Physical properties of emulsion stabilized by kappa casein before and after treatment with chymosin

Gerung, Anita 12 April 2006 (has links)
In order to determine the effect of lipid concentration on the properties of k-casein stabilized emulsions, butteroil was added to solutions that contained 0.3% k-casein to achieve milk fat concentrations of 3, 10, and 20%. These mixtures were adjusted to pH 6.5 and heated to 65°C. They were then homogenized at 20 and 100 MPa and particle size was measured; viscosity and yield stress were measured before and 30 minutes after the addition of chymosin. These experiments were repeated twice. Homogenization of the emulsions at 100 MPa produced smaller particles than homogenization at 20 MPa. Emulsions with 20% milk fat showed the largest particle size. Before treated with chymosin, these emulsions had the greatest viscosity and yield stress, however the differences with the other lipid concentrations were greater after chymosin treatment. A gel with yield stress less than 10 Pa occurred in emulsions with 3 or 10% milk fat. The emulsion with 20% milk fat after chymosin treatment provided the best possibility for the formation of a gel because it had the highest viscosity and yield stress. The effect of protein concentration on the properties of the emulsions was determined in emulsions that contained 20% milk fat and 0.5, 0.7, and 1.0%. These emulsions were prepared as previously described. Emulsions homogenized at 100 MPa had smaller particles than emulsions homogenized at 20 MPa. An increase in protein concentration caused the particle size to decrease. Emulsions homogenized at 100 MPa were more stable than emulsions homogenized at 20 MPa and the emulsion with 1.0% k-casein was the most stable emulsion. The protein load of k-casein stabilized emulsions ranged from 3 to 6 mg/m2. The viscosity and yield stress prior to chymosin treatment showed no properties of gelation. After treated with chymosin, these emulsions produced a weak gel with yield stress values that ranged from 14 to 16 Pa.
23

Investigation of oil adsorption capacity of granular organoclay media and the kinetics of oil removal from oil-in-water emulsions

Islam, Sonia 25 April 2007 (has links)
Produced water, a byproduct of oil and gas production, includes almost 98% of all waste generated by oil and gas exploration and their production activities. This oil contaminated waste water has a great impact on our environment and is considered to be a high-cost liability. The Department of Energy’s Oil and Gas Environmental Program is concerned with the development of new and affordable technology to clean this produced water. Organically modified clays are proposed as a good option for removal of oil from produced water. Organoclay, incorporated into a treatment process shows promise of being a cost effective method of treatment to remove crude oil from brine either as a final treatment prior to brine disposal at sea or as a precursor to desalination. Organoclay also pre-polishes the waste water before further treatment. This research studies the efficacy of using organoclay to remove oil by measuring its adsorption capacity to remove the oil from a SAE 30 (Golden West Superior) motor oil-water emulsion. A kinetic model was developed to examine the time dependent behavior of the oil adsorbing characteristics of the organoclay and to investigate how closely the experimentally obtained data matches the kinetic model. It was found that organoclay is effective in removing various percentages of oil depending on the concentrations of a SAE 30 (Golden West Superior) motor oil-water emulsion. Moreover, it was found that the experimental data closely follow the kinetic behavior of the organoclay as shown by the kinetic model. Since this research is specific to a particular type of oil, SAE 30, further research is required for verifying the adsorption capacity of organoclay in other types of oils. Moreover, it is also recommended that the adsorption capacity of the organoclay, together with conventional adsorbent such as GAC (Granular Activated Carbon), be investigated to determine if there is any further improvement in the adsorption capacity. Lastly, a detailed investigation using the actual produced water from the oil field should be conducted to determine the efficacy of the organoclay system in removing oil from water produced in the field.
24

Study on Lubricating Properties of Emulsions in EHL Contacts

Wang, Tsung-hsien 07 September 2008 (has links)
In this study, a model has been developed for the elastohydrodynamic lubrication with binary mixtures of compressible fluids, which can be used to represent emulsions with suspended deformable particles. The coupled modified Reynolds, elasticity, and rheology equations are solved simultaneously by combining the advanced multilevel method and the Newton-Raphson method. The effects of speed, load, dimensionlesss materials parameter, inlet oil volume fraction, droplet radius, surface tension group, elasticity of mixture, and equivalent viscosity models of emulsions on the lubrication characteristics of the emulsions are investigated. The speed, load, and oil volume fraction combinations studied in this study represent a broad range of operating conditions previously not investigated. The results of this study are in good agreement with the tests conducted by Kimura et al. and Zhu et al. indicating the effects of droplet radius of oil phase and the speed on the film thickness. The film thickness increases with increasing droplet size for the droplet size smaller than the film thickness. At the low oil volume fraction and low speed, the oil volume fraction increases rapidly with coordinate x to form the oil pool in the region close to the Hertzian contact area. With the increase of speed, the extent of the oil pool decreases significantly so that the oil volume fraction at the contact area decreases rapidly. Consequently, the film thickness also decreases due to the decrease in the effective viscosity of the mixture. When the speed is getting higher, the oil and water phases enter the contact conjunction so that the oil volume fraction is closer to the inlet one.
25

Hybrid composite latexes /

Jeong, Pilmoon, January 2000 (has links)
Thesis (Ph. D.)--Lehigh University, 2000. / Includes bibliographical references and vita.
26

Living-controlled free radical miniemulsion polymerization of styrene /

Pan, Gaofeng, January 2002 (has links)
Thesis (Ph. D.)--Lehigh University, 2003. / Includes bibliographical references and vita.
27

Effects of agitation in emulsion polymerization of n-Butyl methacrylate and its copolymerization with N-methylol acrylamide /

Krishnan, Sitaraman, January 2002 (has links)
Thesis (Ph. D.)--Lehigh University, 2003. / In two parts. Includes bibliographical references and vita.
28

Comparison of shear stability of mini and macroemulsion latexes with respect to particle size and number distribution

Rodrigues, Jeffrey Collin 05 1900 (has links)
No description available.
29

Dynamic modeling of continuous miniemulsion polymerization reactors

Samer, Charles J. 12 1900 (has links)
No description available.
30

Feasibility study for continuous emulsion copolymerization of ethyl acrylate and methacrylic acid

Shoaf, Glenn Lewis 12 1900 (has links)
No description available.

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