Dissertations / Theses on the topic 'Agitated'

In agitated dryers the motion of the impeller leads to shear deformation within the bed, which causes attrition. The attrition caused by the prevailing stresses and strains in a particle bed exposed to simple, well defined shear deformation in an annular shear cell has been extensively studied in the literature, however little effort has been made to better understand more complex shearing flows. A method of predicting particle breakage in agitated dryers is introduced here. The method uses models based on the Distinct Element Method (DEM), validated by torque and Positron Emission Particle Tracking (PEPT) measurements, to estimate the stress and strain rate distributions throughout the dryer bed. The attrition of Paracetamol and Aspirin under shear deformation in an annular shear cell is assessed and relationships of attrition to stress and strain developed. These relationships are combined with the stress and strain rate distributions obtained from the DEM to predict the attrition in a small-scale dryer. The attrition of Paracetamol and Aspirin in the small-scale dryer is measured experimentally and compared to the prediction. The relationship of Paracetamol attrition to stress and strain correlates well with the shear cell results; this is not the case for Aspirin. The prediction of Paracetamol attrition in the dryer therefore compares well to that measured experimentally, whereas the prediction of Aspirin attrition is less successful as the attrition resulting from the prevailing stresses and strains is not adequately described. The methodology developed here is generic and can be applied to a wide range of processes, such as dense pneumatic conveying, milling and grinding etc. III

L’argomento trattato è lo studio di due liquidi immiscibili all’interno di un recipiente agitato. Una nuova tecnica di misura delle dimensioni delle particelle viene presentata, la tecnica sperimentata è non invasiva in quanto tutti gli strumenti di misura sono stati posizionati esternamente al vessel. Il recipiente conteneva una dispersione di olio siliconico in acqua, i test sono stati condotti in assenza di coalescenza. Il sistema è agitato in un primo test da una girante Rushton e in un secondo da una girante con denti; esso consiste in un recipiente cilindrico dal diametro T=300mm in vetro, questo vessel è stato inserito in un secondo recipiente, anch’esso in vetro ma dalla geometria cubica, riempito di acqua per ridurre problemi legati alla distorsione ottica dovuta alla cilindricità delle pareti del vessel agitato. Il recipiente è stato posto tra una fotocamera ad alta velocità e una lampada avente lo scopo di illuminare la dispersione. Sono state quindi relazionate le reali dimensioni in mm delle gocce, con i pixel della fotocamera nella fase di calibrazione; la taratura è stata effettuata tramite l’utilizzo di speciali sfere solide monodimensionali. L’analisi della dispersione in esame consisteva nella cattura di più set di immagini ad intervalli di tempo prestabiliti, solo dopo che la dispersione fosse arrivata all’equilibrio. La foto sono state quindi salvate in stack ed analizzate da un apposito codice che è stato scritto per il programma di analisi di immagini utilizzato: ImageJ. La possibilità di implementare macro in ImageJ rende molto flessibile questo programma, caratteristica fondamentale in questo lavoro in quanto lo studio di questi liquidi ha richiesto un notevole numero di test per ottenere una corretta interpretazione delle dimensioni delle gocce. Segue infine l’analisi dei dati ottenuti, alcune correlazioni riportate in letteratura sono state verificate statisticamente a partire dai risultati ottenuti.

Experimental data are reported for solids suspension and distribution in four geometrically similar vessels with diameters equal to 0.31, 0.61, 1.83 and 2.67 m. Agitation was provided by a series of pitched blade turbines with impeller to vessel diameter ratios from 0.3 to 0.6 and pitched angles between 30° and 90°. The effect of impeller clearance on solids suspension was examined for a clearance range of T/4 to T/8. Dual impeller systems were also studied, covering two combinations (dual pitched and flat/pitched) and impeller spacing of half to two diameters apart. The majority of the experiments were carried out with 150-210 μm round-grained sand (density: 2630 kg ‭m-3 and settling velocity: 0.015 m s-1) and tap water. Solids concentration was varied between 0.1 to 40% by weight. Four parameters were measured; impeller speed, using an optical tachometer, power input, calculated from the shaft torque given by strain gauges, just suspension speed, ascertained both visually and by use of an ultrasonic Doppler flowmetering (UDF) technique and the local solids concentration, measured by a in-house solids concentration probe. In addition extensive flow visualisations were made with the 0.61 m vessel in order to establish both liquid and particles flow patterns during the experiments. Results from this study were compared with previous publications in order to examine the effects of some of the important geometrical variables on solids suspension and distribution. This work revealed that for the range of parameters covered, the smallest (D/T=0.3) and the largest (D/T=0.6) impellers are the most and least efficient ones for solids suspension. Distribution tests with the three geometrically similar impellers show that the results are neither correlated in terms of tip speed nor power input but are best described by the thrust force generated by the impellers. In general, dual impeller systems improve solids distribution but require more power to just suspend solids compared with a single impeller. The scaling effect proposed by Zwietering (1958) for solids suspension has been confirmed by this study for vessel up to 2.67 m in diameter. The constant tip speed rule for solids distribution, which is based on one-dimensional dispersion models was found to underestimate the power requirement in large scale applications. This study indicates that equal power per unit volume is required to achieve the same degree of homogeneity.

In this dissertation the power draw, the mass transfer and the liquid mixing behaviour of boiling and hot sparged stirred tank reactors (STRs) were investigated. The power draw characteristics of six different impellers were studied under varying operating conditions and expressed in terms of the relative power draw, RPD. Generally the impellers showed considerably higher power draw in hot gassed than in comparable cold conditions. The main phenomenon in hot systems, the evaporation of liquid into a gas bubble suddenly exposed to it, was investigated experimentally. The growth of nitrogen and air bubbles in hot water was found to be very fast and be completed typically within milliseconds after their exposure to the liquid. This was confirmed by studies applying acoustic bubble sizing techniques which were carried out together with Richard Manasseh from CSIRO, Melbourne, Australia. Experimental studies of the gas-liquid mass transfer in hot sparged STRs were carried out using a tank of 450 mm in diameter agitated by a 180 mm Rushton turbine. Experiments involving the temperature kinetics in an air-water system and absorption and desorption of ammonia were used to determine gas and also some liquid side mass transfer coefficients. The gas side coefficients kga were found to be typically in the order of 0.01 s-1. An enhancement of the liquid side mass transfer was also observed. Both Fick and Stefan-Maxwell models were employed to express gas side mass transfer coefficients. The models predict there will be a decrease of the coefficients at high concentrations. In the hot sparged tank the temperature is essentially uniform throughout the STR. Liquid mixing times have been measured for various boil-off and sparging rates. No significant deviations from the single phase or the cold gassed mixing times in this equipment were recorded.

Liquid-liquid extraction has long been known as a unit operation that plays an important role in industry. This process is well known for its complexity and sensitivity to operation conditions. This thesis presents an attempt to explore the dynamics and control of this process using a systematic approach and state of the art control system design techniques. The process was studied first experimentally under carefully selected. operation conditions, which resembles the ranges employed practically under stable and efficient conditions. Data were collected at steady state conditions using adequate sampling techniques' for the dispersed and continuous phases as well as during the transients of the column with the aid of a computer-based online data logging system and online concentration analysis. A stagewise single stage backflow model was improved to mimic the dynamic op.eration of the column. The developed model accounts for the variation in hydrodynamics, mass transfer, and physical properties throughout the length of the column. End effects were treated by addition of stages at the column entrances. Two parameters were incorporated in the model namely; mass transfer weight factor to correct for the assumption of no mass transfer in the. settling zones at each stage and the backmixing coefficients to handle the axial dispersion phenomena encountered in the course of column operation. The parameters were estimate.d by .. minimizing the differences between the experimental and the model predicted concentration profiles at steady state conditions using non-linear optimisation technique. The estimated values were then correlated as functions of operating parameters and were incorporated in·the .. model equations. The model equations comprise a stiff differential~algebraic system. This system was solved using the GEAR ODE solver. The calculated concentration profiles were compared to those experimentally measured. A very good agreement of the two profi1es was' achieved within a percent relative error of ±2.S%.The developed rigorous dynamic model of the extraction column was. \ls~d to derive linear time-invariant reduced-order models that relate the input variables (agitatorsjJeed, . solvent feed flowrate and concentration, feed concentration andflowrate) to the output variables (raffinate concentration and extract concentration) using the asymptotic method of system identification. The reduced-order models were shown to be accurate in capturing the dynamic behaviour of the process with a maximum modelling prediction error of I %. The simplicity and accuracy of the derived reduced-order models allow for control system design and analysis of such complicated processes. The extraction column is a typical multi variable process with agitator speed and solvent feed flowrate considered as manipulative variables; raffinate concentration and extract concentration as controlled variables and the feeds concentration and feed flowrate as disturbance variables. The control system design of the extraction process was tackled as multi-loop decentralised S1S0 (Single Input Single Output) as well as centralised MIMO (Multi-Input Multi-Output) system using both conventional and model-based control techniques such as IMC (Internal Model Control) and MPC (Model Predictive Control). Control performance of each control scheme was. studied in terms oJ stahilit~, speed of response, sensitivity to modelling errors (robustness), setpoint tracking capabilities ahd load rejection. For decentralised control, multiple loops were assigned to pair .each manipulated variable with each controlled variable according to the interaction analysis and other pairing criteria such as relative gain array (RGA), singular value analysis (SVD) and Jacobi eigenvalue criterion. Loops namely Rotor speed-Raffinate concentration and Solvent flowrateExtract concentration showed weak interaction. Multivariable MPC has shown more effective performance compared to other conventional techniques since it accounts for loops interaction, time delays, and input-output variables constraints

The drying of pharmaceutical powders following their isolation via crystallization and filtration is examined using a laboratory-scale agitated filter dryer (AFD). Vacuum contact and through-circulation convective drying with and without agitation of aspirin powders with pure and mixed solvents are studied through an integrated experimental and modelling approach. Experiments were carried out under different operating conditions by using aspirin particles and water/water-ethanol as typical solid-solvent systems. Two approaches were used to study the drying behaviour of aspirin: 100 µL small-scale drying using thermal gravimetric analysis (TGA) and 5 L medium-scale drying in a laboratory AFD. While the TGA tests provided a better understanding of drying kinetics as functions of temperature, vacuum level, solvent type and particle size, the AFD study revealed the effects of industry-relevant operating parameters (such as the heating rate, vacuum level, agitation speed and regime, gas flow rate, and initial solvent content) on the drying of aspirin particles. In the TGA experiments, the constant and falling rate periods are observed for drying with pure water, while only the falling rate period is observed for pure ethanol and water-ethanol mixed solvents. In the laboratory-scale AFD experiments, drying cycle time is found to decrease with increasing agitation speed, vacuum level, heating power supplied and gas flow. The critical solvent content is determined by identifying the transition point on the temperature-time and the torque-time plots during the drying process. Particle size distribution and morphology analysis of aspirin particles before and after drying with agitation indicate that the particles tend to agglomeration at lower stirring speeds while they are prone to attrition at higher speeds. An increase of the circularity of the particles with the increase of the agitation speed is observed due to attrition effect. Drying models based on a lumped-parameter (LPM) approach are developed for the static and agitated bed vacuum contact drying and combined LMP and distributed-parameter model (DPM) for the convective drying. Within this modelling approach, only one parameter that is the critical solvent content needs to be estimated from experimental results compared to other LPMs which greatly reduced the degree of parameter estimation. These computationally expedient models can be used for the prediction of drying time in a fast and reliable way. The model equations are implemented in gPROMS software and the models are applied to simulate the experiments carried out in the 5 L AFD. The vacuum contact drying experiments were also simulated using a DPM embedded in the gPROMS software. The modelling results of LPM were compared with that obtained using the DPM. Overall, a good agreement between the calculated and measured drying curves is obtained and the measured drying times are well predicted at varied drying conditions. This research presented the following improvements over the current studies on powder bed drying with limited research on organic crystalline materials and mixed solvent: holistic studies on drying behaviour with varied external drying conditions as well as internal material properties using different scale apparatus: TGA and AFD. Over the previous LPMs on powder bed drying, the modelling approach presented the following improvements: the models developed in this work need less parameter estimation. Three consistent approaches to measure the required parameter at the laboratory scale have been described in this work. The models provide a potential for industrial application on AFD drying.

Many daily life products consist of mixtures of oil and water. When an immiscible material is dispersed an interface in-between the two phases is created which gives rise to rheological phenomena which can be exploited for product formulation; this is the case in products such as hand-creams and food products. Furthermore emulsions are used to transport hydrophobic materials, for example, many pharmaceuticals are injected as emulsions into the bloodstream. The performance of such products depends on their microstructure, which is determined by its formulation and how its constituents are mixed together; therefore the microstructure depends on the properties of the dispersed phases, the emulsifier used, the equipment used and its processing conditions. Emulsified products are seldom mono-dispersed due to the complex drop breakup mechanism in the turbulent fields inside the equipment in which the phases are forced together. The chaotic breakup mechanism of highly viscous dispersed phases yield complex and broad drop size distributions (DSD) as a result of the dominating viscous cohesive stresses inside the parent drop. Former studies have used the Sauter mean diameter and/or the size of the largest drop as the characteristic measure of central tendency of the DSD to correlate their results and to prove mechanistic or phenomenological models; however these parameters in isolation are insufficient to characterise the whole DSD of highly polydisperse emulsions. In this dissertation a vast amount of silicon oils of different viscosity were used as dispersed phase to study the effect of various processing conditions and formulations on the resulting DSD. The effect of several formulation and processing parameters were studied for two different mixing devices: stirred vessels and in-line high-shear mixers. (1) For stirred vessels, the effect of stirring speed, continuous phase viscosity and dispersed phase volume fraction were studied in combination with the viscosity of the dispersed phase for steady-state systems. (2) For in-line high-shear mixers a model that links batch and multi-pass continuous emulsification for multimodal DSD was derived from a transient mass balance. Processing parameters such as time and volume, flow rate and number of passes through the mixer, and stirring speed were studied for a wide dispersed phase viscosity range. The analytical methodology implemented included the use of one or more probability density functions to describe the shape of the DSD. The models proposed gave reasonable approximations of the Sauter mean diameter and allowed to study the drop size changes and the relative amount of different types of drops resulting from different breakup mechanisms.

Thermal energy storage via the latent heat of suitable phase change materials has the advantages of higher energy storage density and relatively isothermal behaviour compared to sensible heat storage systems. Glauber's salt (Na₂S0₄∙10H₂0) is one of the most extensively studied phase change materials for solar energy systems because of its low price, suitable phase change temperature and high latent heat. However, segregation due to incongruent melting behaviour leading to loss in the heat storage efficiency upon repeated melting-freezing cycling is a serious problem which has severely limited application of Glauber's salt. In this study Glauber's salt was encapsulated in 25 mm diameter hollow spheres and agitated in different systems including a liquid fluidized bed, rotating drum and rotating tube to reduce or eliminate the Toss in its heat storage efficiency. The encapsulated mixture consisted of 96% Glauber's salt and 4% borax by weight with 5% by volume air space in the capsules. Some capsules containing 25%, 15% and 5% by weight excess sodium sulfate and 10% by weight excess water were also prepared, to test the effect of sodium sulfate concentration under different agitation conditions. The heat storage capacity of 5756 capsules, agitated by fluidizing with water in a pilot plant size (0.34 m diameter) column, showed a decrease over the first three cycles to about 60% of that theoretically possible, but there was no further decrease over the next 93 cycles under fluidization conditions. The heat storage efficiency was found to be improved by increasing the superficial water velocity and by decreasing the cooling rate. Heating rate had little or no effect. The fluidized capsules provide enhanced heat transfer rates to or from the heat storage medium, enabling the energy to be charged or discharged in about one hour with realistic inlet and outlet temperatures. The high heat transfer rates are an important advantage for the system and may open new areas of applications for thermal energy storage by encapsulated phase change material. Economic analysis of the liquid fluidized bed heat storage system shows that operating costs are almost negligible compared to fixed capital costs. The heat storage efficiency of capsules decreased to 38.4% of the theoretical capacity or 67% of the corresponding agitated (fluidized) system in only 7 cycles under fixed bed conditions, and the efficiency decreased with further cycling. 97.5% of the original heat storage-capacity was recovered within three cycles when these capsules were refluidized. Performances of the regular and different composition capsules were tested in the rotating tube, with rotation around a fixed horizontal axis passing through the capsules' centers, and in the rotating drum, with impact due to collisions in addition to rotation. The results showed that full rotation of a capsule around a horizontal axis improves the heat storage efficiency. However, full recovery of the theoretical capacity was not possible, even under vigorous mixing conditions. The efficiencies in the rotating tube were similar to those in the rotating drum for capsules subject to the same number of rotations around a horizontal axis. At high rotation speeds centrifugal force had a negative influence, especially in the rotating tube. On the basis of heat storage capacity per unit volume or weight of phase change material, 47% by weight sodium sulfate concentration was found to be optimal for the rotating drum and the rotating tube cases. Some small scale experiments were performed to determine the relative importance of different factors in the loss of heat storage capacity. Sodium sulfate concentration gradients in the capsules with different thermal cycling histories were found by thermogravimetric analysis. The results showed that bulk segregation of anhydrous sodium sulfate is not the only reason for the loss of heat storage capacity in systems using Glauber's salt. Microencapsulation of anhydrous sodium sulfate beneath a layer of Glauber's salt crystals is at least as important. Experiments to determine the degree of subcooling, believed to be another factor in the loss of heat storage capacity, showed that a mixture of 96% Glauber's salt and 4% borax by weight undergoes subcooling of about 5 K in gently agitated capsules. Nucleation and crystallization temperatures both increase with increased agitation.<br>Applied Science, Faculty of<br>Chemical and Biological Engineering, Department of<br>Graduate

L’industria di processo è basata su diverse operazioni unitarie, le quali possono essere divise in due gruppi principali: il primo contenente quelle volte alla produzione vera e propria dei prodotti, mentre le rimanenti hanno come scopo la separazione dei prodotti d’interesse da quelli ritenuti di scarto. Per questo motivo, un corretto dimensionamento delle apparecchiature coinvolte è strettamente consigliato. Tuttavia, in situazioni complesse come i sistemi bifase, ciò non è sempre possibile. Infatti, lo scambio di materia che avviene tra il liquido e il gas non può essere calcolato analiticamente con formule puramente teoriche, ma al contrario, diversi dati sperimentali sono richiesti. Per questo motivo, spesso il dimensionamento di questo tipo di reattori è spesso fatto a tentativi, senza seguire una procedura ingegnerizzata. Per risolvere questo problema, diversi studi stanno cercando di costruire una corretta procedura per predire, in modo più accurato possibile il valore del coefficiente di scambio volumetrico. Il valore di questo parametro, infatti, è strettamente richiesto nella soluzione dei bilanci di materia che permettono il dimensionamento dell’apparecchiatura. In particolare, questo parametro può essere ricavato da misurazioni sperimentali. Tuttavia, diverse metodologie impiegate restituiscono risultati differenti. Per questo motivo, la letteratura contiene numerosi articoli con risultati significativamente diversi tra di loro. Tuttavia, metodi di misurazione più efficaci sono stati introdotti. Tra questi si ricorda il Dynamic Pressure Method, il quale sarà utilizzato in questo elaborato per la valutazione del coefficiente di trasporto di materia volumetrico. Inoltre saranno proposte diverse correlazioni come un utile strumento per il dimensionamento di fermentatori industriali con più di una girante.

Mechanically agitated vessels are widely used for various mixing operations within a wide range of industries including the chemical, pharmaceutical, food and petroleum industries. They are used for liquid blending, solid-liquid mixing, gas dispersion in liquids, heat/mass transfer enhancement and chemical reaction. Mixing is intrinsically a Lagrangian process and, whilst Eulerian data are essential, Lagrangian information is necessary for its complete description. Possible approaches of generating Lagrangian data can, in principle, employ numerical simulations or experimental techniques based on Lagrangian tracking to provide the trajectories of fluid elements or solid particles. In this work a set of tools are developed for the analysis and theoretical validation of Lagrangian single and multi-phase flow data obtained from tracer trajectories in mechanically agitated vessels. Whilst theoretical procedures developed here exploit a large range of mathematical and statistical concepts with Shannon entropy being an example, the computational data analysis often involved handling and sequential processing of multidimensional matrices containing several millions of data points. Computational codes were developed for performing Lagrangian statistical data analysis, Lagrangian-Eulerian data conversion, Shannon entropy analysis, multi-phase mixing studies and detailed Eulerian multi-plane investigations. The implementation and power of these tools are demonstrated by analysing a wide range of measurements acquired using the technique of positron emission particle tracking (PEPT) during the mixing of Newtonian and non-Newtonian fluids, as well as the mixing of highly concentrated solid-liquid systems. These multi-phase suspensions included monodisperse, binary and polydisperse solid-liquid suspensions. Experimental measurements obtained in these systems are unique and valuable in their own right as, for the first time, it has been possible to determine the full 3D velocity and concentration fields of liquid and solid phases within opaque dense slurries of this type containing up to 40 wt% solids.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010.<br>Thesis submitted in partial fulfilment of the requirements for the Degree of MASTER OF SCIENCE IN ENGINEERING (MINERAL PROCESSING) in the Department of Process Engineering at the University of Stellenbosch<br>ENGLISH ABSTRACT: The use of dimensional analysis to scale-up mechanically agitated flotation processes and to identify deficiencies in froth flotation plants was explored. The full range of operating variables was considered, such as particle size distribution, reagent suite, conditioning time, retention time, machine geometry, aeration, solids suspension, power requirements and turbulence. Dimensional analysis offers a methodology to combine variables into dimensionless groups to guide the scale-up process based on the notion of similarity. Ten dimensionless groups were developed and combined with metallurgical variables, such as liberation, reagents dosage and flow diagrams to produce a scale-up and evaluation tool, applicable to any mechanically agitated flotation process. In many hydrodynamic studies, the researchers considered hydrodynamic variables based on rotor diameter. In this case the hydrodynamic variables based on rotor diameter represent mechanism “ability”, while parameters based on cell diameter are considered “requirement”. Dimensionless groups have also been applied to the definition of basic parameters of the kinetic constant, such as floatability, bubble surface area flux and froth recovery factor. It also showed that the bubble surface area flux has a maximum with increased aeration, where similar models do not show this dependence. Analysis by computational fluid dynamics and Perspex modelling revealed valuable insight into the inner working of the Wemco flotation machine, such as air dispersion, turbulence levels, separation zones and solids concentration. Design changes to the rotor, disperser, hood and geometrical lay-out produced a marked improvement in flotation conditions. It also supported certain dimensionless numbers measured in full scale plants. Case studies confirmed that almost all flotation plants, irrespective of the minerals floated, suffer from the same deficiencies. Dimensional similitude offers a unique tool to identify these deficiencies and to predict the effect of recommended improvements. In almost every case where the fundamental requirement of similarity was applied, an improvement in performance was observed. Finally a new algorithm is proposed for the scale-up of flotation plants and the application is demonstrated in the design and testing of a pilot plant.<br>AFRIKAANSE OPSOMMING: Die gebruik van dimensionele analise in die opskaal van flottasieprosesse en die identifisering van flottasieaanlegprobleme is ondersoek. Die volle bereik van bedryfsveranderlikes is ondersoek, soos partikelgrootte, kondisioneringstyd, retensietyd, geometrie, lugvloei, suspensie van vastestowe, turbulensie en drywingsvereistes. Dimensielose analise is die proses waardeur veranderlikes deur wiskundige manipulasie gekombineer word in dimensielose groepe. Tien dimensielose groepe is ontwikkel en is tesame met metallurgiese veranderlikes soos vrystelling, reagensdosering en vloeidiagramme gekombineer om gebruik te word om gelykvormigheid te bewerkstellig. Hierdie proses is van toepassing op enige flottasieproses gebaseer op meganies geagiteerde toerusting. Dimensielose groepe is ook gebruik in die definisie en kwantifisering van turbulensie, agitasie, geometrie, suspensie van vastestowe, verspreiding van lug en drywingsvereistes. Daarbenewens is die groepe gebruik in die definisie van die basiese veranderlikes van die kinetiese konstante soos lugborreloppervlakvloed, suspensie, en herwinning in die skuimfase. Die groepe is ook gebruik in die bewys dat die lugborreloppervlakvloed ´n maksimum het met toename in lugvloei. In baie gevalle word hidrodinamiese veranderlikes uitgedruk in terme van die rotordiameter en in hierdie studie word dit beskou as meganisme “vermoë”. Die hidrodinamiese veranderlikes gebaseer op sel-diameter word beskou as “behoefte”. Berekeningsvloeidinamika en Perspex modellering het waardevolle insig verskaf in die binne-werking van die Wemco flottasiemasjien soos lugverspreiding, turbulensie en partikelkonsentrasie en is ook gebruik om sekere dimensielose getalle wat in volskaalse aanlegte gemeet is, te verifieer. Gevallestudies het bevestig dat feitlik alle flottasieaanlegte, ongeag die soort mineraal, gebuk gaan onder dieselfde afwykings. Dimensionele analise bied ‘n eenvoudige benadering om hierdie afwykings te identifiseer en om die effek van veranderings te voorspel. In alle gevalle waar die beginsels van gelykvormigheid slaafs gevolg is, het n merkbare verbetering in prestasie voorgekom. Ten slotte is ´n nuwe opskaleringsalgoritme ontwikkel en is die toepassing daarvan gedemonstreer deur die ontwerp en toets van ´n loodsaanleg, gebaseer op die Wemco geometrie.

Conjugate flow and heat transfer has been investigated in an unbaffled pilot-scale stirred tank reactor with a plain jacket. The vessel volume was 25 litres with a nominal capacity of 20 litres. Experiments and three-dimensional CFD simulations have been conducted on this vessel. The experiments involved heating, boiling, and cooling of methanol as well as water. The heat transfer medium in the jacket was an oil mixture called ‘DW-Therm’. The CFD simulations of some aspects of these experiments have been broken down into jacket-only and process-only simulations, followed by a fully conjugate simulation. The link between flow patterns, pressure drop and heat transfer in conventional jackets of stirred tank reactors has been analysed. The experiments and CFD simulations have been performed using a range of DW-Therm inlet temperatures. The CFD results were compared with experimental data of temperature measurements and with the use of engineering correlations found in the literature to predict heat transfer coefficients from the experimental data. The simulations produced values of total heat transferred by the jacket within 10% of the experimental results. The simulations of boiling inside the vessel approximated a constant process temperature which was used to investigate the jacket-only phenomena. The process-only and the conjugate simulations simulated heating of water inside the vessel. Mathematical analysis as well as and industrially and academically used correlations from the literature were used to estimate heat transfer coefficients for boiling and external heat loss. These correlations for overall heat transfer coefficients overlook maldistribution of heat transfer coefficients in jackets that use a liquid heat transfer medium. This is industrially important because it provides new information to consider when maintaining highly temperature-dependent processes, in which adequate heat transfer to or from the process is required. This could be for a variety of reasons, from maintenance of product quality to preventing runaway reactions.

This study aims at understanding the effect of fluid rheology on gas dispersion and mixing in mechanically agitated vessels. Bulk flow is linked with the two-phase flow in the impeller region and the power drawn by the rotating agitator(s). A base case study using a Rushton Disc Turbine in water is initially reported. Model Newtonian, viscoelastic and shear-thinning fluids (corn syrup, Boger fluids and Carbopol solutions respectively) and a typical fluid (CMC solution) were then used to determine the effects of fluid rheology on flow phenomena and power consumption for single agitators (Disc Turbines and Angle-Bladed Impellersl dual combinations thereof, and InterMIGs under gassed and ungassed conditions in a 0.61 m diameter vessel. Similar experiments were performed in smaller vessels. The relative effectiveness of all the agitator configurations studied at achieving bulk liquid mixing was also determined using a redox reaction technique. The most energy efficient configuration proved to be a large Disc Turbine combined with an equisized Angle-Bladed Impeller (pumping upwards) in both the gassed and ungassed cases. The results presented in this thesis are also related to process design considerations and a technique which predicts the agitator rotational speed and diameter required for achieving optimal mass transfer is developed.

Agitated behaviours in dementia elderly predispose to negative outcomes. Music intervention is an evidence-based intervention that could help to ease the situation. The integrative and systematic review studies provide evidence that music intervention is effective in reducing agitated behaviours in dementia elderly. The assessment of the implementation potential, the feasibility and transferability demonstrate the music intervention can be implemented in local setting. An evidence-based guideline based on the reviewed papers is developed to use in local HK hospitals or nursing homes. With the help of an effective communication plan to the stakeholders, it is believed that the intervention can be smoothly implemented. Further evaluation helps to review the potentials for sustaining the intervention in the long run.<br>published_or_final_version<br>Nursing Studies<br>Master<br>Master of Nursing

An apparent inverse dependence of oxidation rate on temperature was discovered between approximately 270&deg;C and 295&deg;C using 60% tin-40% lead alloy as a result of a preliminary investigation carried out to determine the effect of temperature on the oxidation and drossing rates of stirred tin-lead alloy melts. This effect was found to be dependent on time and the composition of the alloy, and coincided with a considerable rise in drossing rate. Furthermore the oxidation rate of stirred 60% tin-40% lead alloy showed a very unusual increasing rate with time. Therefore a systematic study was carried out to determine the factors which control the oxidation and drossing rates of liquid tin-lead alloys, pure tin and pure lead at temperatures between approximately 200&deg;C and 400&deg;C. The results of the study are reported in two parts. In the first part the effects of time, temperature, the concentration of tin in the alloy, stirring rate and the effects of additions of up to 0.2% of copper, cadmium, zinc, aluminium, antimony silver and phosphorus on the weight gain and the weight of dross formed using stirred tin-lead alloys are reported. It was found that except for a phosphorus addition of 0.01% which reduces the weight gain of stirred 60% tin-40% lead alloy by at least 50%, the additions generally show only minor effects on the weight gain dependence of the alloy on temperature. The oxidation kinetics of stirred 60% tin-40% lead alloy have been interpreted using the Arrhenius equation. Drosses were examined and analysed using scanning electron microscopy, metallography, X-ray diffraction, X-ray photoelectron spectroscopy and atonic absorption spectrophotometry. In the second part of the study the effects of temperature and air pressure on the oxidation kinetics of static melts of 60% tin-40% lead alloy, pure tin and solid lead were determined using an electromicrobalance. Generally parabolic kinetics were observed indicating that the oxidation processes involved are diffusion controlled. It was also found that the oxidation gate of static melts of 60% tin-40% lead alloy at 270&deg;C exceeds that at 295&deg;C using an air pressure of 250 Pa although this effect is eliminated by reducing the air pressure to 50 Pa. Furthermore the oxidation rates of liquid 60% tin-40% lead alloy, pure tin and solid lead were in general higher using the lower air pressure of 50 Pa. The results obtained in this part of the study have also been inteipreted using the Arrhenius equation. Furthermore the oxide layers were examined and analysed using scanning electron microscopy and X-ray diffraction techniques. It appears that changes in the morphology of the oxide layer on liquid 60% tin-40% lead alloy may account for the observed changes in the oxidation rate of the alloy with, temperature and air pressure. A comparison of the oxidation rates of static and stirred melts of 60% tin-40% lead alloy show clearly that the oxidation rate of the stirred alloy is controlled by the additional surface area exposed as a result of drossing. Furthermore the nature of the oxide layer appears to have a significant effect on the drossing rate of the alloy. It was also shown by calculation that the observed time dependence of the fall in weight gain of stirred 60% tin-40% lead alloy with temperature could be explained in terms of the total surface area of the alloy exposed to the atmosphere.

Pour stopper un emballement thermique dans un réacteur chimique, un moyen efficace consiste à introduire une faible quantité d'un inhibiteur liquide appelé « killer » dans la cuve agitée. Tout au long de cette thèse, l'approche expérimentale a été fortement couplée à la modélisation numérique par Computational Fluid Dynamics (CFD). La première partie du manuscrit porte sur l'hydrodynamique des réacteurs partiellement chicanés incluant la prise en compte du vortex central qui se forme à leur surface. L'utilisation d'une approche numérique multiphasique, non-homogène a permis de modéliser la déformation de la surface-libre, et la faisabilité de cette méthode innovante a été démontrée par un très bon accord entre prédictions numériques et données expérimentales. Dans une deuxième partie, l'introduction d'un jet de liquide sur la surface libre a été couplée à l'hydrodynamique du réacteur. Les résultats numériques, obtenus avec une approche Eulerienne-Lagrangienne, ont également montré un bon accord avec les données expérimentales. Ces résultats ont permis de modéliser la trajectoire du jet, de quantifier sa pénétration dans la cuve agitée, et de définir de nouveaux critères de mélange. Enfin, les méthodes numériques validées à l'échelle pilote ont été étendues à l'échelle industrielle et ont permis de proposer des améliorations concrètes pour une meilleure sécurité des réacteurs industriels étudiés.

Reproduction de : Thèse de doctorat : Génie des procédés et de l'environnement : Toulouse, INPT : 2007. Reproduction de : Thèses de doctorat : Chemical and biomolecular engineering : Sydney, University of Sydney : 2007.<br>Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. 277 réf.

To quench a thermal runaway reaction in a chemical rector, an efficient approach is the introduction of a small quantity of a liquid inhibiting agent, named a “killer”, into the mixing vessel. In this thesis, an experimental approach has been coupled tightly with numerical modelling using Computational Fluid Dynamics (CFD). The first part of this thesis is devoted to a study of the hydrodynamics of partially-baffled mixing vessels, including the free-surface deformation caused by the central vortex. The use of an inhomogeneous, multiphase approach allowed simulation of the free-surface deformation. The capability of this novel method was demonstrated by very good agreement between the numerical predictions and experimental data. In the second part, liquid jet injection at the free-surface was coupled with the vessel hydrodynamics. Numerical results, obtained using an Eulerian-Lagrangian approach, have again shown good agreement with experimental data. These results allowed the jet trajectory to be modelled and its penetration into the agitated vessel was quantified. New mixing criteria were introduced that are specific to this application. Finally, the numerical methods validated at the pilot scale were applied at the industrial scale and allowed the proposal of practical improvements to the safety of the synthesis reactors studied

Theatre is widely unrecognized for the compelling influence it has held in society throughout history. In this thesis, I specifically examine the implications surrounding the social protest theatre of black and Jewish American minority communities in the first half of the twentieth century. I discuss how their historical circumstance, culture, and idiosyncratic natures caused them to choose agitated propaganda theatre as an avenue for protest. I delve into the similarities in circumstance, but their theatre case studies separate the two communities in the end. I present case studies of each community, beginning with anti-lynching plays of the 1920s that were written by black American playwrights both in response to white supremacist propaganda theatre and to assert a dignified representation of the black community. However, their plays and protest movement never developed a larger popular following. My next minority theatre case study is an examination of 1930s Jewish labor drama created in protest of popular anti-Semitic theatre and poor labor conditions. The Jewish community differs from the black community in their case because the racist propaganda was produced by a man who was Jewish. Another difference is that their protest theatre was on the commercial stage by this point because of a rise in a Jewish middle class and improvement of circumstance. Both the Jewish protest theatre and labor reform movements were more successful. My conclusion is a summation of black and Jewish American theatre of the era with a case study of collaboration between the communities in George Gershwin’s operetta about black Americans, Porgy and Bess. I conclude that these two communities eventually departed from circumstance and therefore had differing theatrical, political, and social experiences in America during the 1930s.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010.<br>ENGLISH ABSTRACT: Hydrocarbons provide excellent feed stocks for bioconversion processes to produce value added products using various micro-organisms. However, hydrocarbon-based aerobic bioprocesses may exhibit transport problems where the bioconversion is limited by oxygen supply rather than reaction kinetics. Consequently, the overall volumetric oxygen transfer coefficient (KLa) becomes critical in designing, operating and scaling up of these processes. In view of KLa importance in hydrocarbon-based processes, this work evaluated KLa measurement methodologies as well as quantification of KLa behavior in aerated agitated alkane-solid-aqueous dispersions. A widely used KLa measurement methodology, the gassing out procedure (GOP) was improved. This improvement was done to account for the dissolved oxygen (DO) transfer resistances associated with probe. These resistances result in a lag in DO response during KLa measurement. The DO probe response lag time, was incorporated into the GOP resulting in the GOP (lag) methodology. The GOP (lag) compared well with the pressure step procedure (PSP), as documented in literature, which also incorporated the probe response lag time. Using the GOP (lag), KLa was quantified in alkane-solid-aqueous dispersions, using either inert compounds (corn flour and CaCO3) or inactive yeast cells as solids to represent the micro-organisms in a hydrocarbon bioprocess. Influences of agitation, alkane concentration, solids loading and solids particle sizes and their interactions on KLa behavior in these systems were quantified. In the application of an accurate KLa measurement methodology, the DO probe response lag time was investigated. Factors affecting the lag, which included process conditions such as agitation (600-1200rpm), alkane concentration (2.5-20% (v/v), alkane chain length (n-C10-13 and n-C14-20), inert solids loading (1-10g/L) and solids particle sizes (3-14μm) as well as probe characteristics such as membrane age and electrolyte age (5 day usage), were investigated. Kp, the oxygen transfer coefficient of the probe, was determined experimentally as the inverse of the time taken for the DO to reach 63.2% of saturation after a step change in DO concentration. Kp dependence on these factors was defined using 22 factorial design experiments. Kp decreased on increased membrane age with an effect double that of Kp decrease due to electrolyte age. Additionally, increased alkane concentration decreased Kp with an effect 7 times higher compared to that of Kp decrease due to increased alkane chain length. This was in accordance to Pareto charts quantification. KLa was then calculated, using the GOP (lag), according to equation [1] which incorporates the influence of Kp. Equation 1 is derived from the simultaneous solution of the models which describe the response of the system and of the probe to a step change in DO. 1 1 * L p p p K at K t L p p La C K e K ae C K K = -  - - -  -   [1] The KLa values documented in literature from the PSP and KLa calculated by the GOP (lag) showed only a 1.6% difference. However KLa values calculated by the GOP (lag) were more accurate than KLa calculated by the GOP, with up to >40% error observed in the latter according to t-tests analyses. These results demonstrated that incorporating Kp markedly improved KLa accuracy. Consequently, the GOP (lag) was chosen as the preferred KLa measurement methodology. KLa was determined in n-C14-20-inert solid-aqueous dispersions. Experiments were conducted in a stirred tank reactor with a 5L working volume at constant aeration of 0.8vvm, 22ºC and 101.3kPa. KLa behavior across a range of agitations (600- 1200rpm), alkane concentrations (2.5-20% (v/v)), inert solids loadings (1-10g/L) and solids particle sizes (3-14μm) was defined using a 24 factorial design experiment. In these dispersions, KLa increased significantly on increased agitation with an effect 5 times higher compared to that of KLa increase due to interaction of increased alkane concentration and inert solids loading. Additionally, KLa decreased significantly on increased alkane concentration with an effect 4 times higher compared to both that of increased solids particle sizes and the interaction of increased agitation and solids particle size. In n-C14-20-yeast-aqueous dispersions, KLa was determined under narrowed process conditions better representing typical bioprocess conditions. KLa behavior across a range of agitations (600-900rpm), alkane concentrations (2.5-11.25% (v/v)) and yeast loadings (1-5.5g/L) using a 5μm-yeast cell was defined using a 23 factorial design experiment. In these dispersions, KLa increased significantly on increased agitation. Additionally, KLa decreased significantly on increased yeast loading with an effect 1.2 times higher compared to that of KLa decrease due to interaction of increased alkane concentration and yeast loading. In this study, the importance of Kp for accurate KLa measurement in alkane based systems has been quantified and an accurate and less complex methodology for its measurement applied. Further, KLa behavior in aerated alkane-solid-aqueous dispersions was quantified, demonstrating KLa enhancement on increased agitation and KLa depression on increased alkane concentration, solids loading and solids particle sizes.<br>AFRIKAANSE OPSOMMING: Koolwaterstowwe dien as uitstekende voervoorraad vir ´n verskeidenheid van mikroorganismes wat aangewend word in biologiese omsettingsprosesse ter vervaardiging van waardetoevoegende produkte. Hierdie biologiese omsettingsprosesse word egter vertraag weens die gebrek aan suurstoftoevoer onder aerobiese toestande. Die tempo van omsetting word dus beheer deur die volumetriese suurstofoordragkoeffisiënt (KLa) eerder as die toepaslike reaksiekinetika. Die bepaling van ´n akkurate KLa word dus krities tydens die ontwerp en opskalering van hierdie prosesse. Met dit in gedagte het hierdie studie die huidige metodes om KLa te bepaal geëvalueer en die gedrag van KLa in goed vermengde en belugde waterige alkaanmengsels met inerte vastestowwe, soos gisselle, in suspensie ondersoek. ´n Deesdae populêre metode om KLa te bepaal, die sogenaamde gasvrylatingsprosedure (GOP) is in hierdie studie verbeter. Die verbetering berus op die ontwikkeling van ´n prosedure om die suurstofoordragsweerstand van die pobe wat die hoeveelheid opgeloste suurstof (DO) meet, in berekening te bring. Hierdie weerstand veroorsaak ´n vertragin in the responstyd van die probe. Die verbeterde metode, GOP (lag), vergelyk goed met die gepubliseerde resultate van die drukstaptegniek (PSP) wat ook die responstyd in ag neem. GOP (lag) is ingespan om KLa te gekwantifiseer vir waterige alkaan-vastestof suspensies. Inerte componente soos mieliemeel, kalsiumkarbonaat en onaktiewe gisselle het gedien as die vastestof in suspensie verteenwoordigend van die mikroörganismes in ´n koolwaterstof bio-proses. Die invloed van vermengingstempo, alkaan konsentrasie, vastestof konsentrasie en partikelgrootte asook die interaksie van al die bogenoemde op KLa is kwatitatief bepaal in hierdie studie. Faktore wat die responstyd van die DO probe beïnvloed is ondersoek. Hierdie faktore is onder meer vermengingstempo (600-1200opm), alkaankonsentrasie (2.5-20% (v/v)), alkaankettinglengte (n-C10-13 en n-C14-20), vastestofkonsentrasie (1-10g/L) en partikelgrootte (3-14 μm). Faktore wat die eienskappe van die probe beïnvoed, naamlik membraan-en elektrolietouderdom (5 dae verbruik), is ook ondersoek. Kp, die suurstofoordragskoeffisiënt, is bepaal deur ´n inkrementele verandering in die suurstofkonsentrasie van die mengsel te maak en die tyd vir 63.2% versadiging van die probelesing te noteer. Die genoteerde tyd is die response tyd van die probe en Kp, die inverse van hierdie tyd. Die afhanklikheid van Kp op die bogenoemde faktore is ondersoek in ´n 22 faktorieël ontwerpte reeks eksperimente. Kp toon ´n afname met ´n toename in membraanouderdom. Hierdie afname is dubbel in grootte as dit vergelyk word met die afname relatief tot die toename in elektrolietouderdom. Verder toon Kp ´n afname met ´n toename in alkaankonsentrasie. Hierdie afname is 7 keer groter relatief tot die afname gesien met die toename in alkaan kettinglengte. Hierdie is in goeie ooreenstemming met Pareto kaarte as kwantifiseringsmetode. KLa is bereken met die inagname van Kp volgens vergelyking [1]: 1 1 * L p p p K at K t L p p La C K e K ae C K K = -  - - -  -   [1] Vergelyking [1] is afgelei vanaf die gelyktydige oplossing van die bestaande modelle wat die responstyd van die pobe vir ´n stapverandering in DO bereken. Die KLa waardes van die PSP metode uit literatuur verskil in die orde van 1.6% van dié bereken deur vergelyking [2]. Hierdie verskil is weglaatbaar. Die KLa waardes verkry uit die GOP metode wat nie Kp in berekening bring nie, verskil met meer as 40% van die huidige, verbeterde metode volgens die statistiese t-test analiese. Dit bewys dat die inagname van Kp ´n merkwaardige verbetering in die akuraatheid van KLa teweeg bring. GOP (lag) kry dus voorkeur vir die berekening van KLa verder aan in hierdie studie. KLa is bereken vir n-C14-20-water mengsels met inerte vastestofsuspensies. Die eksperimente is uitgevoer in ´n 5L geroerde reaktor met ´n konstante belugting van 0.8vvm (volume lug per volume supensie per minuut), 22ºC en 101.3kPa. Die gedrag van KLa met betrekking tot vermengingstempo (600-1200opm), alkaankonsentrasie (2.5-20% (v/v)), vastestofkonsentrasie (1-10g/L) en partikelgrootte (3-14μm) is ondersoek in ´n 24 faktorieël ontwerpte reeks eksperimente. Verder is die invloed van vloeistofviskositeit en oppervlakspanning op KLa ondersoek in ´n 23 faktorieël ontwerpte reeks eksperimente. KLa het ´n beduidende toename getoon met ´n toename in vermengingstempo. Hierdie toename was 5 keer groter as die toename relatief tot die interaksie van alkaan-en vastestofkonsentrasie. KLa het ook beduidend afgeneem met ´n toename in alkaankonsentrasie. Die toename was 4 keer groter as die toename relatief tot die toename in partikelgrootte en die interaksie van vermengingstempo en partikelgrootte. In n-C14-20-water mengsels met gisselsuspensies is KLa bepaal onder kondisies verteenwoordigend van tipiesie biologiese omsettingsprosesse. Die gedrag van KLa met betrekking tot vermengingstempo (600-900opm), alkaankonsentrasie (2.5-11.25% (v/v)) en giskonsentrasie (1-5.5g/L) met ´n partikelgroote van 5μm is ondersoek in ´n 23 faktorieël ontwerpte reeks eksperimente. Hierdie eksperimente het ´n beduidende toename in KLa met ´n toename in vermengingstempo getoon sowel as ´n beduidende afname met ´n toename in giskonsentrasie. Hierdie afname is in die orde van 1.2 keer groter in vergelyking met die interaksie van alkeen- en giskonsentrasie. Hierdie studie bring die kritieke rol wat Kp speel in die akkurate bepaling van KLa in waterige alkaansisteme met inerte vastestofsuspensies na vore. Dit stel verder ´n metodiek voor vir die akurate meting van en kwantifisering van beide Kp en KLa onder aerobiese toestande met betrekking tot vermengingstempo, alkaankonsentrasie, vastestofkonsentrasie en partikelgrootte.

Thermal treatment is the most common method used by industry to ensure food is safe for consumption and to increase its storage life. To ensure safety, food is often overprocessed which can significantly affect its nutritional value as well as taste and flavour attributes. In this study, the heating and mixing efficiency of a bespoke vessel used for heat treatment of complex foodstuffs (250 litre ‘Vesuvio’ vessel manufactured by Giusti Ltd) was investigated. Enzymatic Time Temperature Integrators (TTIs) were used to determine the heat treatment efficiency. TTIs are small unattached measurement devices which contain a thermally labile enzyme: determination of the degree of degradation of the enzyme at the end of the thermal process enables the integrated temperature history to be obtained. TTIs can be used for process validation, particularly when the processing environment is inaccessible for fixed devices such as thermocouples. The reliability and accuracy of the TTIs was determined by exposure to various non isothermal industrially relevant temperature profiles using a Peltier stage and Polymerase Chain Reaction (PCR) device. The integrated temperature histories obtained by the TTIs’ correlated generally well with data obtained from thermocouples installed in parallel, although the error increases with holding time of the heat treatment. The work showed that the TTIs can be used reliably over a range (e.g. Enzymatic TTI made from the α-amylase from the Bacillus Licheniformis can reliably used from 5 to 30 minutes at 85°C) which is relevant for conditions of thermal pasteurisation of interest to this study. The range of time temperature profiles that enzymatic TTIs can monitor depends on the thermal resistance of the enzyme. The heat treatment efficacy of the ‘Vesuvio’ vessel was evaluated using TTIs and two thermocouples fixed onto the vessel wall and impeller shaft at the centre of the vessel. In addition to the plain or ‘free’ TTIs, a new TTI was developed where it was placed at the centre of an open structure to prevent intimate contact between the surface of the TTI and the vessel wall (‘Golf Ball’ and ‘Tie Clip’ TTIs). The food fluid could, however, penetrate the structure. The parameters examined in the study were fluid rheology, fill level (100% and 120% filling level) and the heating options (steam heating via wall jacket or direct injection). The study showed that the thermal process efficiency is lowered as the fluid viscosity increases when the wall jacket was used alone; this was observed by greater differences between the temperatures recorded by the thermocouples between the centre and the vessel wall. This was overcome by using direct steam injection into the vessel contents. Overfilling the vessel was also found to affect performance. The ‘free’ TTIs were found to have a higher thermal treatment than the TTIs which could not directly contact the wall. Under perfect mixing conditions, the ‘free’ TTIs and the TTIs placed inside the open structure should both give close results. However, this is not the case and it can be seen that the discrepancy increases when the mixing conditions worsen (increase of the fluid viscosity, no use of steam injection). The reliability of the TTIs as a validation tool is dependent upon their following the same path as the food fluid, i.e. they should be isokinetic and follow the fluid streamlines. To investigate this issue, the flow of both fluid and TTIs was examined on a reduced scale version of the ‘Vesuvio’ vessel using Particle Image Velocimetry (PIV) and Positron Emission Particle Tracking (PEPT). The effect of changing fluid rheology, agitation speed and filling level were investigated on the basis of a scaling at constant power per unit mass. The PIV experiments showed that the flow was laminar/transitional through bulk of vessel, with significant flow instabilities at the free surface and at the trailing edge of the impeller. Bulk mixing can therefore be expected to occur by laminar mechanisms with some mixing by eddy diffusion present at the free surface. The mixing pattern was not affected by rheology or agitation speed, however, overfilling of the vessel appeared to move the centre of the fluid rotation to above the impeller shaft, as verified using PEPT. PEPT was also applied by inserting either the free tracer into the fluid or placing it within a TTI. Significant differences in the path taken by the TTI and the fluid were observed when the TTI had a significant settling velocity in the fluid. Hence TTIs cannot be assumed to give reliable results in low viscosity fluids (e.g. water).

The parallel-competing iodide-iodate reaction scheme has been used to study micromixing phenomena in baffled and unbaffled vessel of 0.29 m diameter (T) agitated by a Rushton turbine (D=1/3T) under turbulent conditions in a semi-batch mode. Firstly it was confirmed that by using successive injections, this reaction scheme is very efficient for such a study. Using this technique for the rest of the programme of work the first experiments were undertaken in the “standard baffled geometry”. Four agitator speeds giving mean specific energy dissipation rates, T ε , from ~0.2 W/kg to ~1.2 W/kg were used. For a given speed, addition at five different static feed locations, one just above the liquid surface and four submerged, were investigated. The four sub-surface feeding positions were associated with different local specific energy dissipation rates, εT, ranging from less than T ε , very close to the top of the liquid, to much greater close to the impeller. The point closest to the impeller was chosen to be such that feeding was estimated to be at the point of (εT)max. For the maximum speed, the segregation index, Xs, as a measure of the amount of 'waste product', was ~20% with feed onto the top of the liquid (as preferred industrially because of its convenience) or if slightly submerged. This 'waste' was reduced to ~5% by feeding at (εT)max. The distribution of εT was estimated from numerical solutions of the incorporation model combined with relationships arising from turbulence concept. A comparison was also made with results reported in the literature using the same reaction for two new devices developed for improved micromixing. By feeding at the carefully chosen position close to the impeller, the results with the Rushton turbine were as good as or better than with the special devices even at the comparatively low T ε of ~1.2 W/kg. It was estimated that the ratio of T T ε /ε (=φ) gave a maximum circumferentially averaged value of φ of ~90. The iodide-iodate technique was then used to ascertain the effectiveness of micromixing in a standard baffled reactor when feeding with pipes rotating with the impeller and discharging continuously into the region of (εT)max. The results when compared with those obtained using the fixed pipe at the equivalent position showed a significant intensification. Overall, a seven-fold reduction in ‘waste product’ was found between the most convenient fixed feed pipe position above the liquid surface and the rotating pipes, even at the modest T ε of ∼1.0 W/kg. This study is the first to use feeding continuously into the region of (εT)max. Thus an angular resolved (εT)max could be estimated from the incorporation model compared to a circumferentially averaged (εT)max obtained with a fixed pipe. The former was ∼3.0 times the latter, in close agreement with recent PIV based measurements. Finally the same geometry but without baffles was studied. The power number Po was measured and found to be Po=0.8, much less than Po=4.3 for the baffled tank. Visual decolourisation to give the macromixing time θm revealed evidence of a poor mixing region corresponding to the forced vortex region. The poor mixing in this region was confirmed by micromixing experiments. At the same T ε of 0.18 W/kg in the two cases, the values of segregation index, Xs, were found to be from ∼50% to 40% less than those III obtained with the baffled configuration except in the region close to the impeller where similar Xs values were found. These results are considered surprising, the unbaffled vessel proving much more effective for micromixing then expected. However, these improvements are limited by the very low maximum specific power input of 0.18 W/kg achievable with this configuration. Using the same micromixing model, all local (εT) values were > T ε . Clearly, this result is wrong. It is postulated that the swirling vortex flow past the fixed feed tube may give rise to a high very localised εT value. Clearly, further experimental and modelling work is required to gain a better understanding of the flow structure and micromixing in unbaffled vessels.

<p>Patienten med demens behöver vårdas av personal med erforderlig utbildning. Omvårdnaden av dess patienter är i högsta grad lika viktig som den medicinska vården. I syfte att belysa omvårdnad som förebygger och åtgärdar oro och agitation hos patienter med demenssjukdom användes en systematisk litteraturstudie. Intresseområdet definierades och en fråga ställdes till litteraturen relaterad till syftet, kriterier för avgränsning av artiklar, fastställdes, sökningar genomfördes i databaser och genom manuell sökning i tidskrifter. Relevanta artiklar granskades utifrån kvalitet och bevisvärde. Följande kategorier framkom genom innehållsanalys: Integritets stödjande vård, Bemötande av plockbeteende, Patient centrerad omvårdnad, Minskande av tvång och konfrontation, Konkreta omvårdnadsåtgärder/strategier och teknik. Kommunikation som var anpassad till patientens nivå av kognitiv förmåga och omvårdnadsplan, var det viktigaste. En arbetsmetod som var tillbakadragande/avledande/lämna ifred teknik, var en användbar arbetsmetod som minskade oro och agitation. Det viktigaste var att ha ett bemötande, anpassat med den specifika kunskap i omvårdnad/bemötande som finns.</p><br><p>Patients with dementia are in need of care by educated personal with required knowledge. Nursing is indeed just as important as medical care. To highlight nursing as a way to prevent and measure anxiety and agitation in patients with dementia a systematic literature study was carried out. Subject of interest was defined and a question related to the aim of the study was put to the literature, inclusion criteria were chosen. The literature search was carried out in Databases and manually in magazines. Relevant articles were examined from the perspective of quality and degree of evidence. The following categories appeared thru content analyse: Support of integrity, Refutation of a picking behaviour, Patient centred care,, Reducing compulsion and confrontation, Tangible nursing measures, techniques and strategies. Communication adapt to the patients level of understanding and nursing planning was found most important. Attitude of withdrawal/diversion/leave alone were useful working methods that may less anxiety and agitation. The main thing is however an adjustable encounter with the patient, using the specific knowledge of nursing measures.</p>

abstract Background: Dementia affected patients have increasing problems with memory , impaired language ability, which affects communication and behaviour is considerable. These difficulties may provide an outlet for aggression, agitation and anxiety, and are common in dementia, which is exhausting for patients and their relatives and carers. Behavioural changes are common condition in patients with dementia and affects quality of life and cause unnecessary suffering . Pharmacological treatment that is inserted to relieve these symptoms have many side effects. Printed out more knowledge about non- pharmacological nursing interventions that can facilitate care for patients , relatives and carers are great. Aim: To describe non- pharmacological nursing interventions in dementia care . Method: A general literature review of thirteen scientific papers compiled and described in a result. Results: Compilation resulted in two themes,  Music in dementia care and Stimulation in dementia care and four subthemes, Singing in the care, Listening to music, Activities and Consolation and fillip that showed a dominant positive effect on dementia affected patients and carers and there by create opportunities for caring in dementia care . Conclusion: The different nursing interventions may be useful in dementia care when they show a dominant positive effect on various behavioural changes, it seems memory stimulant and promotes communication between patients and carers which favours caring . Keywords: Agitated behaviour, dementia, non- pharmacological, literature review, nursing.<br>Sammanfattning Bakgrund: Demensdrabbade patienter har tilltagande besvär med minnet, försämrad språkförmåga, vilket påverkar kommunikationen och beteende avsevärd. Dessa svårigheter kan ge utlopp till aggressivitet, oro och ångest och är vanliga vid demenssjukdomar vilket är ansträngande för både patienter, anhöriga och vårdare. Beteendeförändringar är vanligt förekommande tillstånd hos patienter med demens och påverkar livskvalitet och medför onödigt lidande. Farmakologisk behandling som sätts in för att lindra dessa symtom har många biverkningar. Behov utav ökad kunskap kring icke- farmakologiska omvårdnadsåtgärder som kan underlätta omvårdnaden för både patienter, anhöriga och vårdarna är stor. Syfte: Att beskriva icke- farmakologiska omvårdnadsåtgärder i demensvård. Metod: En allmän litteraturöversikt av tretton vetenskapliga artiklar som sammanställdes och beskrivs i ett resultat. Resultat: Sammanställningen resulterade i 2 teman, Musik i demensvård och Stimulans i demensvård och 4 subteman, Sång i omvårdnaden, Att lyssna på musik, Aktivitet och Tröst och stumulans som påvisade en dominerande positiv effekt på demensdrabbade patienter samt vårdarna och därigenom gynnande för vårdandet i demensvård. Slutsats: De olika omvårdnadsåtgärder kan vara användbara inom demensvården då dem visar på en dominerande positiv påverkan på olika beteendeförändringar, verkar minnesstimulerande samt främjar kommunikation mellan patienter och vårdare vilket gynnar vårdandet. Nyckelord: Agiterat beteende, demens, icke- farmakologisk, litteraturöversikt, omvårdnad