No description available.

Thesis (Ph. D.)--University of Canterbury, 2005. / Typescript (photocopy). Includes bibliographical references (leaves 207-214). Also available via the World Wide Web.

Orientador: Waldir Antônio Bizzo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T17:06:17Z (GMT). No. of bitstreams: 1 Fernandes_Renato_M.pdf: 7631607 bytes, checksum: 14334de2da1bd698c87a4fd0efbed3f4 (MD5) Previous issue date: 2011 / Resumo: Os queimadores a jato são caracterizados pela elevada quantidade de movimento na direção axial e elevada potência, estes queimadores são muito empregados em fornos rotativos, principalmente na indústria do cimento e da calcinação. O projeto de queimadores a jato é realizado usualmente aproximando o escoamento de ar primário no queimador por um modelo de escoamento compressível isentrópico em um bocal, esta aproximação leva a elevada divergência entre o projeto e a performance do equipamento em operação. Nesta tese foram desenvolvidos e empregados modelos de escoamento compressível com atrito, troca de calor e variação de área de seção para o escoamento do ar primário no interior do queimador, esta modelagem permite integrar todo o projeto do queimador desde a especificação de motores, sopradores, simulação da rede de tubos que compõe queimador, incluindo o manifold, válvulas de controle, placas de orifício, mangotes etc, inclusive relacionando o escoamento do ar primário com o jato formado pelo queimador através do emprego e também do desenvolvimento de índices aerodinâmicos que representem o jato. Os pontos de inovação incluem além da modelagem proposta também o desenvolvimento de modelo para escoamento em swirlers, aplicação da lei de Crocco em escoamentos com mudança súbita de área de seção, aplicação de modelos de entrainment etc. A modelagem matemática proposta foi empregada no desenvolvimento de um sistema computacional na qual foi usado para simular diversos queimadores em escala industrial, e as simulações obtidas foram comparadas com as medições de campo realizadas nos queimadores. Os resultados das simulações foram muito representativos com divergências de no máximo 5,0 % entre as propriedades do escoamento simuladas com as propriedades mensuradas, por exemplo, pressão, temperatura, vazão etc / Abstract: Jet burners are characterized by their high power and their high momentum in the axis direction. For that reason, these burners are widely used in rotary kilns, especially in the cement and calcination industry. The project of jet burners is based on the approximation of the primary air flow in the burner, through the development of an isentropic compressible flow model for one nozzle. This approximation leads to high differences between the project and the actual performance of the equipment. For the purposes of this thesis, models of compressible flow with friction, heat exchange and variable cross section area for primary air flow inside the burner were developed and applied. The application of these models makes possible the integration of the whole burner project, i.e. specification of motors, blowers, and the simulation of the burner's tubing system, which comprises manifold, control valves, orifices flow meters, hoses, etc. These models also provides means to relate the primary air flow to the jet formed by the burner, through the application and development of aerodynamic indexes that represent the jet. Besides proposed modeling techniques, innovations in this thesis include the development of a model for representing flow in swirlers, an application of the Crocco law for flow through sudden changing cross sections, application of entrainment models, etc. Mathematical modeling was applied in the development of a computational system, which was used to simulate diverse industrial burners. Resulting simulations were compared with measures taken from actual burners. Results obtained were highly representative, showing a variance of 5.0% at the most between simulated flow properties and measured properties, i.e. pressure, temperature, flow rate, etc / Mestrado / Termica e Fluidos / Mestre em Engenharia Mecânica

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering Johannesburg, 11 October 2016 / Refractory lining failure of damaged magnesia bricks and used alumina bricks was investigated by XRF, XRD, SEM-EDS analysis and computational thermochemistry (phase diagrams). In addition, the effect of oxygen partial pressure towards the refractory lining and alkali sulphate ratio were also determined. The presence of low melting phases of KCl, (Na, K) Cl, K2SO4 and CaSO4 compromised the refractoriness of the magnesia bricks because they are liquid at temperatures below clinkerisation temperature (1450 °C). Sodium oxide and potassium oxide in the kiln feed and chlorine and sulphur in the kiln gas atmosphere migrated into the magnesia brick and react to form KCl, (Na, K) Cl and K2SO4. Components of the magnesia brick, CaO reacted with the excess sulphur in the kiln gas atmosphere forming CaSO4. The presence of these impurity phases indicated that the magnesia bricks suffered chemical attack. Potassium and part of components of high-alumina brick reacted to form K2 (MgSi5O12) impurity phase. Phase diagram predictions indicated that the presence of sodium at any given concentration automatically results in liquid formation in the high alumina brick. This confirms that the chemical attack is also the cause of the failure of the high alumina brick. The analysis of the microstructures of both unused and damaged magnesia bricks revealed that the fracture was predominantly intergranular whereas, in high alumina brick, the fracture was transgranular. The absence of evidence of micro-cracks in both magnesia and alumina bricks rules out thermal shock as a failure mechanism. The absence of clinker species and phases in the examined magnesia and alumina bricks indicated that corrosion by clinker diffusion was absent. The partial pressure of oxygen is low (1.333×10−4 atm), it indicates the stability of Fe3O4 and Mn3O4 and therefore does not favour the oxidation of Fe3O4 to formation of Fe2O3 and Mn3O4 to formation of Mn2O3. The values of alkali sulphate ratio indicated that the kiln operating conditions were favourable for chemical attack to occur. / MT2017

This research examines the drying of hardwood timber with particular reference to seasoning blackbutt (Eucalyptus pilularis) in a solar kiln. The aims of this research were to develop an optimised drying schedule for drying blackbutt and to develop and validate a mathematical model for a solar kiln. In the first stage of this study, the cross-grain physical and mechanical properties were determined for blackbutt timber so that an optimised schedule (based on drying within a limiting strain envelope) can be developed using model predictive control techniques for drying 43 mm thick (green) blackbutt timber boards in solar kilns. This optimised schedule has been developed and tested in the laboratory. The drying time was 10% shorter for this schedule than the original schedule, compared with an expected reduction in drying time of 14% (relative to the original schedule). Overall the quality was slightly better and the drying time was shorter for the optimised schedule compared with the original schedule. A complete solar kiln model has been developed and validated based on comparisons between the predicted and the measured internal air temperatures, relative humidities and timber moisture contents. The maximum difference between the actual and predicted moisture contents was 0.05 kg kg-1. The agreement between the predicted and measured temperatures of the internal air is reasonable, and both the predictions and measurements have a similar cyclical pattern. The generally good agreement between the model prediction of the final moisture content and its measurement may be due to the careful measurement of the boundary conditions such as the solar energy input. The key uncertainties were identified as the heat exchanger output, the measurement of the initial moisture content, the amount of accumulation of condensate on the floor, and the estimation of sky temperature. The significant uncertainty (18%) in the estimation of the initial moisture content is a key reason for the mismatch between the model prediction and the measurements. In terms of operating variables, the energy release rate from the heat exchanger had the greatest effect on the simulated performance, followed by the water spray and venting rates. The simulation suggested that a material with a lower transmissivity to thermal radiation may effectively lower radiation losses, improving the kiln performance, so such materials for glazing is a high priority.

No description available.

This research examines the drying of hardwood timber with particular reference to seasoning blackbutt (Eucalyptus pilularis) in a solar kiln. The aims of this research were to develop an optimised drying schedule for drying blackbutt and to develop and validate a mathematical model for a solar kiln. In the first stage of this study, the cross-grain physical and mechanical properties were determined for blackbutt timber so that an optimised schedule (based on drying within a limiting strain envelope) can be developed using model predictive control techniques for drying 43 mm thick (green) blackbutt timber boards in solar kilns. This optimised schedule has been developed and tested in the laboratory. The drying time was 10% shorter for this schedule than the original schedule, compared with an expected reduction in drying time of 14% (relative to the original schedule). Overall the quality was slightly better and the drying time was shorter for the optimised schedule compared with the original schedule. A complete solar kiln model has been developed and validated based on comparisons between the predicted and the measured internal air temperatures, relative humidities and timber moisture contents. The maximum difference between the actual and predicted moisture contents was 0.05 kg kg-1. The agreement between the predicted and measured temperatures of the internal air is reasonable, and both the predictions and measurements have a similar cyclical pattern. The generally good agreement between the model prediction of the final moisture content and its measurement may be due to the careful measurement of the boundary conditions such as the solar energy input. The key uncertainties were identified as the heat exchanger output, the measurement of the initial moisture content, the amount of accumulation of condensate on the floor, and the estimation of sky temperature. The significant uncertainty (18%) in the estimation of the initial moisture content is a key reason for the mismatch between the model prediction and the measurements. In terms of operating variables, the energy release rate from the heat exchanger had the greatest effect on the simulated performance, followed by the water spray and venting rates. The simulation suggested that a material with a lower transmissivity to thermal radiation may effectively lower radiation losses, improving the kiln performance, so such materials for glazing is a high priority.

La recherche de doctorat ici présentée porte sur l’histoire et sur l’évolution du paysage végétal montagnard nord-apenninique et de son lien avec les activités anthropiques qui l’ont façonné au fil du temps. Notre idée de thèse est née grâce au projet international AGRESPE (réseAu Gestion de Ressources Environnementales passéeS et Patrimonialisation paysagèrE), dirigé par Marie Bal du laboratoire de Géographie GEOLAB UMR/CNRS 6042 de l’Université de Limoges. Le travail de thèse a été mené en cotutelle avec l’Université de Modena et Reggio Emilia (Italie).Le paysage végétal des Apennins du Nord a fait l'objet de nombreuses recherches scientifiques sur le paléo-environnement, représentées surtout par des études polliniques (ex. Cruise 1990a, 1990b ; Lowe, 1992 ; Watson, 1996 ; Vescovi et al, 2010a, 2010a, 2010b ; Branch, 2013), mais il présente encore des lacunes sur les recherches paléoenvironnementales et paléoécologiques de haute résolution spatiale. À cause de facteurs liés aux conditions physiques de la montagne et aux intérêts des chercheurs, la recherche archéologique (notamment celle pastorale) n’est pas très développée par rapport aux études de la plaine (Fontana, 1997 ; Cardarelli et Malnati, 2006 ; Ferrari et al., 2006). Ce manque d'études sur les relations entre les sociétés et leur environnement dans les Apennins nous a donc encouragés à en découvrir davantage. Au sein de ce secteur montagnard nous avons choisi deux montagnes clés : le Monte Cimone et le Corno alle Scale. Faisant partie de deux parc régionaux, ces zones d’étude sont caractérisées par des hêtraies qui, jusqu’au milieu du XXe siècle, ont été gérées en taillis pour la production de bois de chauffage et de charbon. La limite altitudinale de la forêt est plus basse que celle écologique potentielle. Au Monte Cimone elle est localisée à 1700 m, tandis que dans la zone du Corno alle Scale elle est située à environ 1600 m. Au-dessus de la limite forestière il y a des bruyères à myrtille et des prairies qui, à l’instar du passé, sont aujourd’hui destinées au pâturage. / This PhD thesis concerns the reconstruction and the development of the Late Holocene plant landscape of two mountain areas of the Northern Apennines: the area of Monte Cimone and the area of Monte Corno alle Scale, located in the two regional parks. Previous research in the two study areas consists of quite numerous pollen analyses at regional scale while studies at local-scale, such as archaeoanthracology and pedoanthracology, are scarce.We have therefore decided to study these two mountain areas through pedoanthracology that is the taxonomic identification of wood charcoals contained in soils. Moreover, archaeoanthracology was applied to charcoal platforms and consists in the analysis of charcoals contained in the platforms which were used until the mid-20th century to produce charcoal. In the methodology used in this thesis are also included field surveys with the aim of locate and geolocalize ancient pastoral structures, witnesses of pastoral activities at high elevations.The main objectives of this research were: - to reconstruct the plant landscape; - to understand how human activities (e.g. pastoralism and forest exploitation) have transformed the landscape; to study the fire history; - to identify the variations of tree and timberline in the past.In the Monte Cimone area, nine pedoanthracological trenches were cut between 1650 m and 2078 m of elevation, and about 4000 charcoals were analyzed; moreover, 10 pastoral structures were found and georeferenced. In the Corno alle Scale area, eight pedoanthracological trenches were cut between 1600 m and 1860 m of elevation, and more than 2000 charcoals were analyzed; no pastoral structure were identified here. In each study area, four charcoal platforms were sampled with a total of 1200 charcoals analysed. Overall, 33 C14datings were performed on charcoals. Almost all C14 dates of soil charcoal are concentrated in the Late Holocene and only two are from the Early Holocene. The anthracomass of the low elevation sampling points (e.g. 962.8 mg/kg) is higher than the anthracomass of the high elevation sampling points (e.g. 1.6 mg/kg). The charcoals are evidence of the past presence of Ericaceae, Fabaceae, Juniperus sp., Abies alba, Quercus sp./Castanea sp., Prunus sp., Betula sp., Taxus baccata, Fagus sylvatica, Fraxinus sp. And Acer sp.The main results of this research show a plant landscape during the last 3000 years that is very similar to the current one with little variations in the tree and timberline. Charcoal platforms analysis has shown a beech charcoal production during the centuries between the 15th and mid-20th centuries. Estimation of the wood size used suggest a well-run exploitation of the timber resource. The two main activity in high mountain, pastoralism and charcoal production, seem to have played an important role in the shaping the current plant landscape.

No description available.

This research examines the drying of hardwood timber with particular reference to seasoning blackbutt (Eucalyptus pilularis) in a solar kiln. The aims of this research were to develop an optimised drying schedule for drying blackbutt and to develop and validate a mathematical model for a solar kiln. In the first stage of this study, the cross-grain physical and mechanical properties were determined for blackbutt timber so that an optimised schedule (based on drying within a limiting strain envelope) can be developed using model predictive control techniques for drying 43 mm thick (green) blackbutt timber boards in solar kilns. This optimised schedule has been developed and tested in the laboratory. The drying time was 10% shorter for this schedule than the original schedule, compared with an expected reduction in drying time of 14% (relative to the original schedule). Overall the quality was slightly better and the drying time was shorter for the optimised schedule compared with the original schedule. A complete solar kiln model has been developed and validated based on comparisons between the predicted and the measured internal air temperatures, relative humidities and timber moisture contents. The maximum difference between the actual and predicted moisture contents was 0.05 kg/kg. The agreement between the predicted and measured temperatures of the internal air is reasonable, and both the predictions and measurements have a similar cyclical pattern. The generally good agreement between the model prediction of the final moisture content and its measurement may be due to the careful measurement of the boundary conditions such as the solar energy input. The key uncertainties were identified as the heat exchanger output, the measurement of the initial moisture content, the amount of accumulation of condensate on the floor, and the estimation of sky temperature. The significant uncertainty (18%) in the estimation of the initial moisture content is a key reason for the mismatch between the model prediction and the measurements. In terms of operating variables, the energy release rate from the heat exchanger had the greatest effect on the simulated performance, followed by the water spray and venting rates. The simulation suggested that a material with a lower transmissivity to thermal radiation may effectively lower radiation losses, improving the kiln performance, so such materials for glazing is a high priority.