vii, 252 leaves : ill. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1973

No description available.

An evaporating meniscus formed by a wetting °uid in a heated capillary slot with capillary driven °flow is numerically and experimentally investigated at the microscale and pore scale. In the microscale analysis, the contact line region of an extended evaporating thin ¯lm meniscus is numerically investigated to study the influence of °uid properties on the heat transfer. The governing equations to describe the fluid °flow, heat and mass transfer phenomena in an evaporating extended meniscus are grouped uniquely as function of °uid dependent parameters, namely the interline heat flow number and heat pipe ¯figure of merit. A physical interpretation of these parameters is presented. Numerical experiments conducted with different working °fluids show that a °uid with a high interline heat °flow parameter and heat pipe ¯figure of merit also has a high cumulative heat transfer in the micro region encompassing the evaporating thin ¯lm. In the pore scale analysis, the evaporation from a pentane meniscus in a heated capillary slot is experimentally and numerically investigated to study how the wetting characteristics are influenced with heat input. In the experimental investigation, a test set up is fabricated with a heated glass capillary slot that is partially immersed in a constant temperature bath with constant °uid level. A novel aspect of this experiment is that both the wicking height and steady state evaporation mass flow rate are measured simultaneously. Based on a macroscopic force balance, the apparent contact angle of the evaporating meniscus is experimentally estimated from the wicking height and mass flow rate. This is compared with the results obtained using evaporating thin ¯lm theory. The experimentally estimated contact angle is higher than that obtained from the thin ¯lm model but both experiment and theory show similar trends. In the numerical study, a ¯finite volume numerical model of an evaporating meniscus in a heated capillary slot (simulating the above experimental condition) is developed for predicting the wicking height and mass flow rate. This model includes: (i) one-dimensional heat transfer and °uid °flow in the liquid and vapour regions of the capillary slot, (ii) one{dimensional evaporating thin ¯lm model for the meniscus region, and (iii) two-dimensional conduction heat transfer in the capillary wall. Correlations obtained from the evaporating thin{¯lm theory in terms of cumulative heat transfer and apparent contact angle are applied to the pore level problem. The problem is solved iteratively between the micro and pore scales till convergence is achieved. The wicking height is influenced by the change in apparent contact angle and the pressure drops to flow of liquid and vapor in the capillary slot that is a function of evaporation mass °ow rate. Heat input to the capillary slot increases both the contact angle in the evaporating meniscus and the frictional pressure drops in the liquid and vapor regions. In the present study, the influence of increased contact angle is more significant and the liquid and vapor pressure drops are negligible. The trends in the wicking height, mass flow rate and conductance are similar to the experimental data. The proposed numerical approach using correlations from thin ¯lm theory to link the micro and macro scales yields results that are consistent with experimental data. The results show that the change in contact angle can degrade the ability of the liquid to wet the pore and hence result in a lower heat transfer coefficident.

Este trabalho experimental tem por objetivo apresentar os estudos experimentais realizados com jatos de líquidos evaporativos (\"flash boiling\") de iso-octano. Nos estudos, o jato emergia de um diminuto bocal que descarrega em uma grande câmara de baixa pressão. O líquido ao passar pelo bocal sofria uma expansão interna alcançando elevados graus de superaquecimento ou de metaestabilidade, já que se mantinha na fase líquida. Nos experimentos, eram controladas as condições de pressão e temperatura de injeção durante um período de alguns poucos segundos suficientes para que as condições de regime permanente fossem estabelecidas. Um dos métodos para a visualização do escoamento do jato evaporativo foi o \"Schlieren\", o qual permitia visualizar elevados gradientes de densidade como normalmente ocorrem com ondas de choque, presentes nesta investigação. Também foi empregada a técnica de visualização de \"iluminação por detrás\" para que fossem comparadas as imagens obtidas por este método com o do \"Schlieren\", bem como mostrar detalhes do fenômeno em estudo. Com isso, foi possível estudar a estrutura do processo evaporativo do jato e, com o auxílio de ferramentas de filtragem matemática e manipulação das imagens obtidas, os fenômenos compressíveis envolvidos. Os perfis dos jatos observados foram: (1) filete contínuo de líquido sem evaporação, (2) jato com fragmentações ou atomizado e (3) abrupta evaporação seguida por expansão com formação de ondas de choque. Neste último caso, a inspeção das fotografias indicou que a evaporação do líquido se dava externamente ao bocal, a partir de um núcleo metaestável de líquido, o qual apresentava o formato aproximado de um cone. Também foi aplicada a teoria de ondas oblíquas de evaporação para estudar o comportamento deste cone líquido. Os ensaios foram conduzidos com três bocais cônico-convergentes de dimensões e materiais diferentes, quais sejam: bocal de aço com diâmetro de saída de 0,3 mm, bocal de aço com 0,8 mm e bocal de vidro com 0,35 mm. / The main goal of this thesis is to present results of experiments with flashing liquid jets of iso-octane. The experiments were carried out with a liquid jet issuing from a small nozzle into a low-pressure chamber. High degrees of metastability were obtained as the liquid jet expanded within the nozzle. Injection pressure and temperature were controlled to the desired testing values for a few seconds, which were found long enough to reach and keep the steady state regime. The photographic documentation of the phenomenon was obtained from a \"Schlieren\" set up using CCD camera. The \"back-lightening\" visualization technique was also used in order to compare both image techniques and to unveil some flashing phenomenon details. Analyses of these images with the help of mathematical filters as well as other image manipulating techniques enabled a qualitative visualization of the flashing liquid jet structure and geometry leaving the nozzle. Three liquid jet regimes were observed: (1) continuous liquid jet (2) partially atomized, and (3) evaporation with the presence of shock waves. In this latter case, we speculate that the evaporation took part on the liquid jet surface, which had the approximate shape of a cone. Also it was employed the oblique evaporation wave theory to explain some of the behavior of the overall evaporation process. The tests were carried out using three conical-converging nozzles made of different materials: a 0.3 mm exit diameter steel nozzle, a 0.8 mm exit diameter steel nozzle, and a 0.35 mm exit diameter glass nozzle.

Este trabalho experimental tem por objetivo apresentar os estudos experimentais realizados com jatos de líquidos evaporativos (\"flash boiling\") de iso-octano. Nos estudos, o jato emergia de um diminuto bocal que descarrega em uma grande câmara de baixa pressão. O líquido ao passar pelo bocal sofria uma expansão interna alcançando elevados graus de superaquecimento ou de metaestabilidade, já que se mantinha na fase líquida. Nos experimentos, eram controladas as condições de pressão e temperatura de injeção durante um período de alguns poucos segundos suficientes para que as condições de regime permanente fossem estabelecidas. Um dos métodos para a visualização do escoamento do jato evaporativo foi o \"Schlieren\", o qual permitia visualizar elevados gradientes de densidade como normalmente ocorrem com ondas de choque, presentes nesta investigação. Também foi empregada a técnica de visualização de \"iluminação por detrás\" para que fossem comparadas as imagens obtidas por este método com o do \"Schlieren\", bem como mostrar detalhes do fenômeno em estudo. Com isso, foi possível estudar a estrutura do processo evaporativo do jato e, com o auxílio de ferramentas de filtragem matemática e manipulação das imagens obtidas, os fenômenos compressíveis envolvidos. Os perfis dos jatos observados foram: (1) filete contínuo de líquido sem evaporação, (2) jato com fragmentações ou atomizado e (3) abrupta evaporação seguida por expansão com formação de ondas de choque. Neste último caso, a inspeção das fotografias indicou que a evaporação do líquido se dava externamente ao bocal, a partir de um núcleo metaestável de líquido, o qual apresentava o formato aproximado de um cone. Também foi aplicada a teoria de ondas oblíquas de evaporação para estudar o comportamento deste cone líquido. Os ensaios foram conduzidos com três bocais cônico-convergentes de dimensões e materiais diferentes, quais sejam: bocal de aço com diâmetro de saída de 0,3 mm, bocal de aço com 0,8 mm e bocal de vidro com 0,35 mm. / The main goal of this thesis is to present results of experiments with flashing liquid jets of iso-octane. The experiments were carried out with a liquid jet issuing from a small nozzle into a low-pressure chamber. High degrees of metastability were obtained as the liquid jet expanded within the nozzle. Injection pressure and temperature were controlled to the desired testing values for a few seconds, which were found long enough to reach and keep the steady state regime. The photographic documentation of the phenomenon was obtained from a \"Schlieren\" set up using CCD camera. The \"back-lightening\" visualization technique was also used in order to compare both image techniques and to unveil some flashing phenomenon details. Analyses of these images with the help of mathematical filters as well as other image manipulating techniques enabled a qualitative visualization of the flashing liquid jet structure and geometry leaving the nozzle. Three liquid jet regimes were observed: (1) continuous liquid jet (2) partially atomized, and (3) evaporation with the presence of shock waves. In this latter case, we speculate that the evaporation took part on the liquid jet surface, which had the approximate shape of a cone. Also it was employed the oblique evaporation wave theory to explain some of the behavior of the overall evaporation process. The tests were carried out using three conical-converging nozzles made of different materials: a 0.3 mm exit diameter steel nozzle, a 0.8 mm exit diameter steel nozzle, and a 0.35 mm exit diameter glass nozzle.

The diploma thesis deals with the processing of digestate, which is the remaining material after biogas production. It aims to experimentally prove how chosen operational parameters of antifoaming agents influence digestate foaming associated with the vacuum evaporating technology. Based on the research of available antifoamers and the issue of digestate foaming itself, it was observed how three selected antifoamers (i.e. rapeseed oil, silicone antifoamer Erbslöh Schaum-ex and oleic acid), together with the decrease in the pH factor of the evaporating digestate, influence the final foam production. For the purposes of the research, an apparatus simulating the vacuum evaporating process was set up in which the heated sample was brought to boil by gradual pressure decrease. The process of foaming was observed in a transparent cylinder of a testing culumn. The essential part of the experimental activity is represented by a planned experiment which by means of a DoE (Design of experiments) method proved rapeseed oil to be very efficient. In contrast, other antifoamers, as well as the influence of the pH factor decrease, manifested themselves as insignificant factors, while the oleic acid even supported the foaming. The supplementary measurements led to a more detailed research of the effects of rapeseed oil and to the construction of a mathematical model describing how the concentration of rapeseed oil undermines the amount of generated foam. The main contribution of the thesis is firstly the evidence that rapeseed oil plays an important part in the reduction process of digestate foaming and secondly the determination of minimum substance concentration leading to the foaming reduction of a particular sample which is considered efficient enough to enable functioning of a vacuum evaporator. The thesis has also experimentally demonstrated the influence of some polymer organic flocculants which have been proved to support the foaming.

The photoactive component of a polymeric organic solar cell can be produced by drying a mixture consisting of a volatile solvent and non-volatile polymers. As the solvent evaporates, the polymers demix and self-assemble into microscale structures, the morphology of which plays a pivotal role in determining the efficiency of the resulting device. Thus, a detailed understanding of the physical mechanisms that drive and influence structure formation in evaporating solvent-polymer mixtures is of high scientific and industrial value. This thesis explores several problems that aim to produce novel insights into the dynamics of evaporating solvent-polymer mixtures. First, the role of compositional Marangoni instabilities in slowly evaporating binary mixtures is studied using the framework of linear stability theory. The analysis is non-trivial because evaporative mass loss naturally leads to a time-dependent base state. In the limit of slow evaporation compared to diffusion, a separation of time scales emerges in the linear stability problem, allowing asymptotic methods to be applied. In particular, an asymptotic solution to linear stability problems that have slowly evolving base states is derived. Using this solution, regions of parameter space where an oscillatory instability occurs are identified and used to formulate appropriate conditions for observing this phenomenon in future experiments. The second topic of this thesis is the use of multiphase fluid models to study the dynamics of evaporating solvent-polymer mixtures. A two-phase model is used to assess the role of compositional buoyancy and to examine the formation of a polymer-rich skin at the free surface. Then, a three-phase model is used to conduct a preliminary investigation of the link between evaporation and phase separation. Finally, this thesis explores the dynamics of a binary mixture that is confined between two horizontal walls using a diffusive phase-field model and its sharp-interface and thin-film approximations. We first determine the conditions under which a homogeneous mixture undergoes phase separation to form a metastable bilayer. We then present a novel mechanism for generating a repeating lateral sequence of alternating A-rich and B-rich domains from this bilayer.

Please read the abstract in the dissertation.pdf of this document / Dissertation (MEng (Industrial Engineering))--University of Pretoria, 2007. / Industrial and Systems Engineering / MEng / unrestricted

Aesthetic criticism very often has been overlooked and considered a lesser form. However, many interpretations, applications and discernments can be obtained from this kind of art writing. Using Osvaldo Sánchez's work as a case study, this thesis examines how writerly art criticism offers an active reading framework of the work of art by using philosophical, literary and poetic constructions. In this regard, I will see how the "writerly" condition has contributed compelling insights to the History of Aesthetics, highlighting the connections and disconnections between Sánchez and other writerly critics, which demonstrates the significance of developing a flexible, available and aesthetic learning model of art appreciation. I will analyze as well various models of experience, subjective and objective, that release certain "openness" as a premise for their existences. Here are included the Kantian sublime, Heidegger's ontological Being, the surrealist cultivation of chance, Kaprow's happenings, and the attitude of disinterest developed by the vanishing poets as defended by the scholar Rafael Hernández Rodríguez. I will show that, by choosing an accommodating approach to discover forms of knowledge, an assortment of valuable empirical content can be found. Finally, I investigate the writerly work of Cuban critic Osvaldo Sánchez that does not adopt a fixed critical pattern. Instead, Sánchez's art writing passes through fields, providing us with a heuristic methodology in which the aesthetic emerges not as a preconditioned set of principles/procedures, but as a true lived experience.

Made available in DSpace on 2014-12-17T14:58:15Z (GMT). No. of bitstreams: 1 MayaraSCFL_DISSERT.pdf: 5165682 bytes, checksum: c5b249c3b897f27db4e517452be9b9ce (MD5) Previous issue date: 2012-04-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Composites based on PEEK + PTFE + CARBON FIBER + Graphite (G_CFRP) has increased application in the top industries, as Aerospace, Aeronautical, Petroleum, Biomedical, Mechanical and Electronics Engineering challenges. A commercially available G_CFRP was warmed up to three different levels of thermal energy to identify the main damage mechanisms and some evidences for their intrinsic transitions. An experimental test rig for systematize a heat flux was developed in this dissertation, based on the Joule Effect. It was built using an isothermal container, an internal heat source and a real-time measurement system for test a sample by time. A standard conical-cylindrical tip was inserted into a soldering iron, commercially available and identified by three different levels of nominal electrical power, 40W (manufacturer A), 40W (manufacturer B), 100W and 150W, selected after screening tests: these power levels for the heat source, after one hour of heating and one hour of cooling in situ, carried out three different zones of degradation in the composite surface. The bench was instrumented with twelve thermocouples, a wattmeter and a video camera. The twelve specimens tested suffered different degradation mechanisms, analyzed by DSC (Differential Scanning Calorimetry) and TG (Thermogravimetry) techniques, Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Rays (EDX) Analysis. Before and after each testing, it was measured the hardness of the sample by HRM (Hardness Rockwell M). Excellent correlations (R2=1) were obtained in the plots of the evaporated area after one hour of heating and one hour of cooling in situ versus (1) the respective power of heat source and (2) the central temperature of the sample. However, as resulting of the differential degradation of G_CFRP and their anisotropy, confirmed by their variable thermal properties, viscoelastic and plastic properties, there were both linear and non-linear behaviour between the temperature field and Rockwell M hardness measured in the radial and circumferential directions of the samples. Some morphological features of the damaged zones are presented and discussed, as, for example, the crazing and skeletonization mechanism of G_CFRP / Comp?sitos baseados em matrizes polim?ricas de PEEK e PTFE, refor?adas com fibra de carbono e grafite (G_CFRP) apresentam crescente aplica??o e desafios ? Engenharia nas ind?strias Aeroespacial, Aeron?utica, de Petr?leo, Biom?dica, Mec?nica e Eletr?nica. Um comp?sito G_CFRP foi aquecido em tr?s n?veis de energia t?rmica para identificar os principais mecanismos de dano e algumas evid?ncias em suas transi??es de mecanismos. Uma bancada experimental foi desenvolvida para sistematizar o fluxo t?rmico com base no Efeito Joule. Foi constru?da usando-se um recipiente isot?rmico, uma fonte quente interna e um sistema de medidas em tempo real para ensaiar um corpo-de-prova (CP) de cada vez. Uma ponta c?nica-cil?ndrica foi inserida em um ferro de soldar, comercialmente dispon?vel e identificado por tr?s diferentes n?veis de pot?ncia el?trica, 40W (fabricante A), 40W (fabricante B), 100W e 150W, selecionados ap?s ensaios piloto: estes n?veis de pot?ncia para a fonte quente, ap?s uma hora de aquecimento e uma hora de resfriamento in situ, promoveu tr?s zonas diferentes de degrada??o na superf?cie do comp?sito. A bancada foi instrumentada com doze termopares, um watt?metro e uma c?mera de v?deo. Os doze C.P. ensaiados apresentaram diferentes mecanismos de degrada??o, analisados pelas t?cnicas de Calorimetria Diferencial Explorat?ria (DSC) e Termogravimetria (TG), e pelas an?lises de Microscopia Eletr?nica de Varredura (MEV) e Energia Dispersiva de Raios-X (EDS). Antes e ap?s cada ensaio, foram feitos ensaios de dureza Rockwell M (HRM). Excelentes correla??es (R2=1) foram obtidas nas curvas da ?rea evaporada ap?s uma hora de aquecimento e uma hora de resfriamento in situ versus (1) a respectiva pot?ncia da fonte quente e (2) a temperatura central do C.P. entretanto, como resultado da degrada??o diferencial do G_CFRP e da sua anisotropia, confirmadas por suas propriedades t?rmicas vari?veis, propriedades viscoel?sticas e viscopl?sticas, houve comportamentos linear e n?o-linear entre o campo de temperatura e a HRM medidos nas dire??es radial e circunferencial dos C.P. Algumas peculiaridades morfol?gicas das zonas de dano s?o apresentadas e discutidas, como, por exemplo, os mecanismos de dano por crazing e esqueletiza??o do G_CFRP