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In this thesis experiments were carried out to achieve the desired objectives of investigating the performance of a novel confined plunging liquid jet reactor incorporating an annular riser. Air entrainment measurements were made using different confining tubes and the induced flow in the annular tube surrounding the confining tube was measured. The oxygen transfer achieved was also determined and compared with other contacting devices. A literature survey regarding the theoretical and experimental work relevant to unconfined and confined systems, air-lift column and mass transfer has been carried out. The experiments include novel equipment utilized to make the lab measurements including air entrainment and novel air-lift column measurements. The theoretical part of the thesis contains a new model derivation to predict the liquid flow rate in the annular riser, which compares well with the experimental measurements. The objective of the first pilot plant experiments is to make air entrainment rate measurements and to investigate the effect of main variables on air entrainment rate. This enables the research to develop a better understanding of the Confined Plunging Liquid Jet Reactor (CPLJR) as an aeration process, of interest of Kuwait Institute for Scientific Research (KISR) and Kuwait, that can be used in various systems such as wastewater treatment as an aerobic activated sludge process, fermentation and gas-liquid reactions.

This thesis describes an investigation into the formation of a laminar liquid jet and its disintegration into droplets in another immiscible liquid. Measurements on jet length, jet diameter and drop diameter are reported. It was found that the diameter of the jet can expand or contract depending upon the nozzle diameter, nozzle velocity and physical properties of the phases. A mathematical model was developed in this investigation to predict the jet diameter at varying distances from the nozzle tip. The results showed good agreement with the corresponding experimental values. In liquid-liquid systems an understanding of drop size distribution is important because this affects interfacial area, relative velocity and mass transfer coefficients. An investigation has been carried out to determine the effects of drop diameter, drop velocity and concentration driving force. on the mass transfer coefficient. To reduce the error in determining the interfacial area inherent in calculation of drop size distributions in liquid-liquid contactors, Das's technique for the production of monosized droplets was employed using waterlacetic acid / kerosene system available in the laboratory. To highlight the effect of drop diameter on mass transfer, a spray column containing kerosene as the continuous phase was used. The total flow of the dispersed phase was kept constant while diameter of drops was varied. The results showed that the mass transfer coefficient increases with the increase in drop diameter and drop velocity. These results were analysed and it is concluded that it is the change in drop velocity that effects the values of mass transfer coefficient. To further investigate this behaviour a ternary system (Toluene/Methanol/Water) was employed. The dispersed phase in the form of a drop (Distilled water) is introduced and the drop extracts methanol from the continuous phase, the drop diameter increases and the density decreases. When the density of the drop becomes less than that of the continuous phase the drop becomes stationary and then starts to rise. For the extraction of methanol using drops of distilled water as the dispersed phase, the mass transfer initially is high this amount reduces with time and approaches a steady state. A discussion of the results is presented in terms of drop velocity. As the drop diameter increases, drop velocity decreases and value of mass transfer coefficient decreases.

In order to study the oil/water interface, model monodisperse emulsions were produced using a microfluidic device. The device contains a series of channels of oil and water, designed to converge so that the aqueous phase imparts sufficient shear on an oil stream to cause it to break and form droplets. Monodisperse emulsions of diameter 15 to 120 μm have been created by varying the aqueous emulsifier concentration, the flow rates of each phase, the channel geometry, and the oil viscosity PFG-NMR echo attenuation curves of the monodisperse emulsions contain modulations attributed to a diffusion-diffraction effect arising from restricted diffusion within the uniform structures. The position of the minima in the dispersed phase echo data is used to size the emulsions. The dispersed and continuous phase atenuation curves are plotted for a single emulsion, demonstrating different form facPtors due to the bounding structure.

This work is concerned with thin layers of fluid on an inclined, flat, solid substrate. and the movement of solid-liquid-air contact lines under the action of gravity. We consider two-dimensional, axisymmetric and three-dimensional geometries. Using lubrication theory to simulate the movement of the fluid and contact lines numerically, we investigate the dependence of the running speed on parameters such as the plate inclination and microscopic slip length. We also find the shape of the free surface of the fluid, as well as the shape of the boundary line (in the three-dimensional case) and can compare these to experimental finding.

Meniscus distortion and fracture during shear occurs frequently in non-Newtonian fluids. Similar instabilities at the free surface of fluids undergoing shear banding have been reported; in some cases the sample was expelled from the cell. In this thesis, the distortion of the free surface of such a shear banding fluid is calculated by balancing the surface tension against the second normal stresses induced in the two shear bands, and simultaneously requiring a continuous and smooth meniscus. It is shown that solutions of worm-like micelles typically retain meniscus integrity when shear banding, but in some cases can lose integrity for a range of average applied shear rates over which one expects shear banding. This meniscus fracture would lead to ejection of the sample as the shear rate is increased within the shear banding range. It is shown further that solutions of entangled polymer are expected to display a propensity for fracture because of their much larger second normal stresses. These calculations are consistent with available data in the literature. Also considered is the meniscus distortion of a three-band configuration, as has been observed in some worm-like micellar solutions in a cone and plate geometry.

This thesis is aims to describe the physicochemical characteristics of microcapsules used in the pesticide industry for the controlled delivery of pesticides to crops.

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