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In this study the unique properties of microfluidic flow have been exploited to generate efficient mass-transfer in continuous segmented flow to investigate an alternative approach for performing chemical extractions. The concept of extraction-enhancement, by incorporation of a solid absorbent in the extracting phase, was explored. Proof-of-principle studies focused on the use of molecularly imprinted polymers (MIPs) to increase the effectiveness of conventional approaches. Laser machining and micro-milling were used to prepare PTFE microfluidic separation devices. Importantly, this included the design and integration of a continuous-flow microfluidic liquid phase separator. Propranolol selective molecularly imprinted polymer microspheres (3.6 µm) were prepared by precipitation polymerisation. MIP performance was assessed using conventional (equilibrium batch rebinding) and segmented-flow liquid-liquid systems. Interfacial mass transfer processes that occur during segmented flow were characterised with respect to flow variables, fluid properties and channel geometries. Segment aspect ratio and flow velocity, together with channel diameter and curvature, were shown to be important. The MIP was shown to possess high affinity and selectivity for the template (propranolol). Incorporation of the MIP into a segmented flow extraction regime was shown to significantly enhance the extent of analyte extraction. Mathematical optimisation approaches showed good correlation with experimental data. On-chip phase separation was demonstrated to be 100% efficient for particle-containing and particle-free immiscible flows. The discovery of soluble MIP species possessing similar binding characteristics to their insoluble counterparts may further improve the kinetics of the reported solid-liquid-liquid extractions. It was successfully demonstrated that a solid phase material can be incorporated into an organic phase to enhance extraction from an aqueous sample either in continuous segmented flow or under equilibrium conditions. The integration of the segmented flow approach with an on-chip liquid phase separator provides a novel platform for the development of unique and highly-efficient continuous flow devices for molecular enrichments, separations and manipulations.

The aim of this research project is to improve the thermal performance of passive flat plate solar collectors using a novel cost effective enhanced heat transfer technique. The project work focuses on the process of energy conversion from the collector to the working fluid. This is accomplished by employing an aluminium grid placed in the channels of a collector to induce a gradient of heat capacitance. This novel technique is tested both theoretically by means of simplistic designs using Computational Fluid Dynamics (CFD) and experimentally using two unglazed collectors. One collector has the aluminium net inserted in its channels and it is tested against an identical conventional collector in order to have a direct comparison at the same time. The obtained CFD data and the experimental findings are coupled and show a good agreement. All the obtained results are validated with the literature. The results both theoretical and experimental demonstrate an enhancement in the heat transfer coefficient by 9 % resulting to an increase in the output temperature of the working fluid in the collector with the metallic insertion. Other parameters such as the Nusselt and Raleigh numbers supported these findings. Three novel expressions that correlate the Nusselt and the Rayleigh number, for different heat fluxes, were developed using data from CFD and experimental results. These correlations can be applied on any flat plate collector with an aluminium grid in its pipes, in order to predict its performance. Furthermore an existing lumped parameters model that predicts the output temperature of a collector was simplified and improved.

An analysis is made for tho laminar film condensation on a rotating axisymmetrical general curved body of which the cylinder, the disc and the cones are special examples. The body rotates about a vertical axis and the film is assumed to drain under the influence of gravitational and centrifugal accelerations. The problem is formulated as a solution of the Navier-Stokes and energy equations. A differential equation which governs the growth of the condensate film is obtained and solved to yield one equation which is applicable to all rotating axisymmetrical bodies. The equation involves the geometry of the body and requires a single integration for the complete solution. Theoretical results of condensate layer thickness and heat transfer coefficients are given for a curved body whose generator forms a circular are of 90 for a speed range of 0.1 to 10(^6) rev/min. It is shown that when the curvature is neglected, the analysis over estimate the local film thickness by 71 per cent. Experimental results for the curved body confirm the theoretical findings. However, due to the formation of roll-waves on the condensate layer and hence a departure from the laminar model, the experimental results for the heat transfer coefficient were 1.055 to 1.440 times greater than the theoretical predictions. No detachment of drops from the film of condensate was observed at the experimental speed range of 0.0 to 1000 rev/min. and the condensate drained as a film along the generator. The criterion for the detachment of drops given by Howe is re-appraised and a new criterion which states that "the non-dimensional film thickness η, should be equal to or greater than 1.8 for the onset of the detachment of dropq" is proposed.

This work investigates the feasibility of applying high temperature oxygen separation to the sulphuric acid decomposition process, a step used in large scale hydrogen production processes currently under development. Porous and dense membranes are both considered. Equilibrium calculations show yttria-stabilised zirconia (YSZ), combined with platinum electrodes, to be a candidate membrane. Process simulations show the potential sulphur dioxide yield increases that could be achieved through the use of a high temperature oxygen separation membrane in two different configurations. Bespoke experimental apparatus was designed, procured and assembled in order to investigate the oxygen flux through YSZ membranes in the presence of sulphur dioxide, during external voltage application. Experiments were performed in the 700 - 900°C temperature range. Results show that oxygen permeation through YSZ membranes occurs under these conditions. A decrease in oxygen permeation with time was observed and attributed to sulphur dioxide adsorption on to the platinum electrodes. Future work would concentrate on using variable applied voltages to reduce this performance decrease.

A modelling technique for simulating the time averaged properties in boundary flows has been formulated. The technique solves the time averaged equations representing conservation of momentum, mass and heat transfer with an approximate mathematical method; and makes use of an interactive scheme, involving manipulation of the mesh into which the flow is divided, to reduce errors from the mathematical method. This technique has been used to simulate the time averaged momentum, mass and heat transfer rates in a series of radial wall jet flows. It has been shown that the technique can predict- momentum, mass and heat transfer rates in flow situations similar to those commonly found in industry. However, accurate simulation of the turbulent transfer processes in a chemically reacting Methane, Carbon Monoxide and Oxygen flow was found to be impossible, because of deficiences in the reaction model. From these results it was deduced that to accurately simulate the transfer processes in complex flows, involving chemical or ionic reactions, a more sophisticated modelling technique should be constructed. It is recommended that this technique be based upon the exact turbulent transport equations.

A multistage distillation column in which mass transfer and a reversible chemical reaction occurred simultaneously, has been investigated to formulate a technique by which this process can be analysed or predicted. A transesterification reaction between ethyl alcohol and butyl acetate, catalysed by concentrated sulphuric acid, was selected for the investigation and all the components were analysed on a gas liquid chromatograph. The transesterification reaction kinetics have been studied in a batch reactor for catalyst concentrations of 0.1 - 1.0 weight percent and temperatures between 21.4 and 85.0 °C. The reaction was found to be second order and dependent on the catalyst concentration at a given temperature. The vapour liquid equilibrium data for six binary, four ternary and one quaternary systems are measured at atmospheric pressure using a modified Cathala dynamic equilibrium still. The systems with the exception of ethyl alcohol - butyl alcohol mixtures, were found to be non-ideal. Multicomponent vapour liquid equilibrium compositions were predicted by a computer programme which utilised the Van Laar constants obtained from the binary data sets. Good agreement was obtained between the predicted and experimental quaternary equilibrium vapour compositions. Continuous transesterification experiments were carried out in a six stage sieve plate distillation column. The column was 3" in internal diameter and of unit construction in glass. The plates were 8" apart and had a free area of 7.7%. Both the liquid and vapour streams were analysed. The component conversion was dependent on the boilup rate and the reflux ratio. Because of the presence of the reaction, the concentration of one of the lighter components increased below the feed plate. In the same region a highly developed foam was formed due to the presence of the catalyst. The experimental results were analysed by the solution of a series of simultaneous enthalpy and mass equations. Good agreement was obtained between the experimental and calculated results.

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