A fast response thin-film heat flux sensor was used to measure the time-resolved surface heat flux and temperature from a turbulent combustion flame impinging on a surface. Using the analytical semi-infinite conduction model, the unsteady surface heat flux was calculated from the transient temperature measurements and the surface temperature was calculated from the unsteady surface heat flux measurements. Methods of comparing time-resolved heat flux and temperature data were presented and discussed. The standard analytical method for converting surface temperature to heat flux was used. Two new analytical methods were developed for converting heat flux to surface temperature. The study is the first demonstration of time-resolved temperature signals generated from time-resolved heat flux measurements. The results graphically illustrate the effects of data processing on electrical noise present in the actual signal. The effect of flame unsteadiness is also shown, especially in the time-resolved heat flux measurements, which gives insight into the behavior of a propane torch. One application is for development of feed-forward control systems in industrial processes with fast transients. / Master of Science

The problem of laminar and turbulent conjugate mixed convection flow and heat transfer in shallow enclosures with a series of block-like heat generating components is studied numerically for a Reynolds number range of zero (pure natural convection) to typically 106, Grashof number range of zero (pure forced convection) to 1015 and various block-to-fluid thermal conductivity ratios, with air as the working medium. The shallow enclosure has modules consisting of heat generating elements, air admission and exhaust slots. Two problems are considered. In the first problem, the enclosure has free boundaries between the modules and in the second problem, there are partitioning walls between the different modules. The flow and temperature distributions are taken to be two-dimensional. Regions with the same velocity and temperature distributions can be identified assuming repeated placement of the blocks and fluid entry and exit openings at regular distances, neglecting end wall effects. One half of such rectangular region is chosen as the computational domain taking into account the symmetry about the vertical centreline. On the basis of the assumption that mixed convection flow is a superposition of forced convection flow with finite pressure drop and a natural convection flow with negligible pressure drop, the individual flow components are delineated. The Reynolds number is based on forced convection velocity, which can be determined in practice from the fan characteristics. This is believed to be more meaningful unlike the frequently used total velocity based Reynolds number, which does not vanish even in pure natural convection and which makes the fan selection difficult. Present analysis uses three models of turbulence, namely, standard k-ε (referred to as Model-1), low Reynolds number k-ε (referred to as Model-2) and an SGS kinetic energy based one equation model (referred to as Model-3). Results are obtained for aiding and opposing mixed convection, considering also the pure natural and pure forced convection limiting cases. The results show that higher Reynolds numbers tend to create a recirculation region of increasing strength at the core region and that the ranges of Reynolds number beyond which the effect of buoyancy becomes insignificant are identified. For instance, in laminar aiding mixed convection, the buoyancy effects become insignificant beyond a Reynolds number of 500. Results are presented for a number of quantities of interest such as the flow and temperature distributions, local and average Nusselt numbers and the maximum dimensionless temperature in the block. Correlations are constructed from the computed results for the maximum dimensionless temperature, pressure drop across the enclosure and the Nusselt numbers.

Resumo: As atividades de uma indústria com o sistema de produção contínua possuem características próprias dependendo do processo a que se dispõe a transformar uma matéria-prima, por isso este trabalho trata de analisar as perdas na produção contínua de extração de óleo de soja por solvente, apresentando a descrição do processo e as principais indicadores de desempenho, propondo sugetões de monitoramento para melhoria dos resultados. Essa abordagem é feita comparando-se resultados propiciados por alguns autores da área com dados da área com dados levantados de uma empresa no Brasil em dois períodos distintos, incluindo análise de evolução da planta, onde a alta gerência monitora a produtividade e a qualidade dos produtos, e trata as perdas no ambiente de transformação como consumo de solvente utilizado para extração do óleo de soja e consumo de combustível para a geração de energia térmica. Conclui-se que a indústria de extração de óleo vegetal, possui diversas variáveis de controle pelo conjunto de operações necessárias à transformação, ressaltando neste caso a perda de energia térmica como prioridade de atitudes de melhorias. Dado que a tendência de aumento da capacidade de processamento de soja é evidente, pela perspectiva de crescimento da produção de soja no Brasil, deve ser considerado neste contexto, o investimento em conhecimento para as pessoas exercerem as atividades operacionais em perfeita sincronia com as informações que ocorrem no processo, garantindo o objetivo da organização de minimização das perdas, e consequente aumento do lucro e crescimento / Abstract: The activities of the industry with a continuous production system have their own characteristics depending on the process that is willing to turn a raw material, so this work is to analyzed the losses in the continuous production of soybean oil extraction solvent, presenting the description of the process and key performance indicators and propose suggestions for the improvement of monitoring results. This approach is made comparing the results obtained by some authors in the field with data collected from a company in Brazil in two distinct periods, including examination of the plant, where top management monitors productivity and product quality, and treats losses the environment of use as processing solvent used to extract the soybean oil and fuel to generate heat energy. It is concluded that the industry of oil extraction plant has several control variables the operations required for processing, emphasizing in this case the loss of thermal energy as priority actions for improvements. Since the trend of increased processing capacity of soybean is evident from the perspective of growth of soybean production in Brazil, should be considered in this context, investment in knowledge for people to exercise operational activities in perfect synchrony with the information occur in the process, ensuring the organization's goal of minimizind losses, and consequent increase in profit and growth / Orientador: Manoel Henrique Salgado / Coorientador: José de Souza Rodrigues / Banca: Rogério Andrade Flauzino / Banca: Vagner Cavenaghi / Mestre

Solid propellant gas generators that have high gas capacity are used for fast pressurization of inflatable devices or elastic shells. However, many applications such as control surface actuation, air bottle pressurization in rocket engines and safety systems of automobiles (airbags) require exit gases at near ambient temperature. A scheme suitable for short duration applications is passive cooling of gas generator gases by using a packed bed as compact heat exchanger. A study indicated that the mass flow rates of solid propellant gas generators for applications such as air bottle pressurization and control system actuators were of the order of 1 kg/s. Since pressure and enthalpy drop correlations for packed beds with mass flow rates (~1 kg/s) and packing sphere based Reynolds number (Red) ~ 9X104 were unavailable in open literature, an experimental investigation was deemed necessary. The objectives of the present study were (a) characterization of packed beds for pressure and enthalpy drop, (b) develop Euler and Nusselt number correlations at Red~105 and (c) evolve an engineering procedure for estimation of packed bed pressure and enthalpy drop. An experimental test facility with a hydrogen-air combustor was designed and fabricated for this purpose to characterize a variety of packed beds for pressure drop and heat transfer. Flow through separate packed beds consisting of 9.5mm and 5mm steel spheres and lengths ~200mm and ~300mm were studied in the sphere based Reynolds numbers (Red) range of 0.4X104 to 8.5X104. The average porosity (є) of the randomly packed beds was ~0.4. The ratios of packed bed diameter to packing diameter for 9.5mm and 5mm sphere packing were ~ 9.5 and 18 respectively. The inlet flow temperature was unsteady and a suitable arrangement using mesh of spheres was used at either ends to eliminate flow entrance and exit effects. Stagnation pressures were measured at entry and exit of the packed beds. The pressure drop factor fpd, (ratio of Euler number (Eu) to packed bed dimensions) for packed bed with 9.5mm spheres exhibited an asymptotically decreasing trend with increasing Reynolds number, and a correlation for the pressure drop factor is proposed as, fpd=Eu/ [6(1-є) (L/dp)] =125.3 Red-0.4; 0.8X104 < Red < 8.5X104 (9.5mm sphere packing). However, for packed beds with 5mm spheres the pressure drop factor fpd, was observed to increase in the investigated Reynolds number range. The correlation based for pressure drop factor is proposed as, fpd= Eu/ [6(1-є) (L/dp)] =0.0479 Red0.37; 0.4X104 < Red < 3.9X104 (5mm sphere packing). The pressure drop factor was observed to be independent of the inlet flow temperature. Gas temperatures were measured at the entry, exit and at three axial locations along centerline in the packed beds. The solid packing temperature was measured at three axial locations in the packed bed. At Red~104, the influence of gas phase and solid phase thermal conductivity on heat transfer coefficient was found to be negligible based on order of magnitude analysis and solid packing temperature data obtained from the experiments. Evaluation of sphere based Nusselt number (Nud) at axial locations in the packed bed indicated a length effect on the heat transfer coefficient, which was a function of Reynolds number and size of spheres used in packing. The arithmetic average of Nusselt numbers at different axial locations in the packed bed were correlated as Nud=3.85 Red0.5; 0.5X104 < Red < 8.5X104. The Nusselt numbers obtained in the experiments were consistent with corresponding literature data available at lower Reynolds numbers. In this experimental study Euler number correlations for pressure drop and Nusselt number correlations for heat transfer were obtained for packed beds at Red~105. An engineering model for estimation of packed bed pressure and enthalpy drop was evolved, which is useful for sizing of packed bed heat exchanger in solid propellant gas generation systems.

Data centers are computing infrastructure facilities used by industries with large data processing needs and the rapid increase in power density of high performance computing equipment has caused many thermal issues in these facilities. Systems-level thermal management requires modeling and analysis of complex fluid flow and heat transfer processes across several decades of length scales. Conventional computational fluid dynamics and heat transfer techniques for such systems are severely limited as a design tool because their large model sizes render parameter sensitivity studies and optimization impractically slow. The traditional proper orthogonal decomposition (POD) methodology has been reformulated to construct physics-based models of turbulent flows and forced convection. Orthogonal complement POD subspaces were developed to parametrize inhomogeneous boundary conditions and greatly extend the use of the existing POD methodology beyond prototypical flows with fixed parameters. A flux matching procedure was devised to overcome the limitations of Galerkin projection methods for the Reynolds-averaged Navier-Stokes equations and greatly improve the computational efficiency of the approximate solutions. An implicit coupling procedure was developed to link the temperature and velocity fields and further extend the low-dimensional modeling methodology to conjugate forced convection heat transfer. The overall reduced-order modeling framework was able to reduce numerical models containing 105 degrees of freedom (DOF) down to less than 20 DOF, while still retaining greater that 90% accuracy over the domain. Rigorous a posteriori error bounds were formulated by using the POD subspace to partition the error contributions and dual residual methods were used to show that the flux matching procedure is a computationally superior approach for low-dimensional modeling of steady turbulent convection. To efficiently model large-scale systems, individual reduced-order models were coupled using flow network modeling as the component interconnection procedure. The development of handshaking procedures between low-dimensional component models lays the foundation to quickly analyze and optimize the modular systems encountered in electronics thermal management. This modularized approach can also serve as skeletal structure to allow the efficient integration of highly-specialized models across disciplines and significantly advance simulation-based design.

During solidification of non-eutectic alloys, non-isothermal phase change causes dendritic growth of solid front with liquid phase entrapped within the dendritic network producing the mushy region. Solidification causes rejection of solute at the solid-liquid interface and within the mushy zone, causing a sharp concentration gradient to build up across the mushy region. At the same time, a temperature gradient is present as a result of externally imposed boundary conditions as well as due to evolution of latent heat, giving rise to the so-called “double-diffusive” or thermo-solutal convection. Depending on the relative density of the solute being rejected in the liquid phase during solidification process, thermal and solutal buoyancy can either aid or oppose each other. Rejection of a heavier solute leads to aiding thermo-solutal convection situation whereas the rejection of lighter solute causes the thermal and solutal buoyancy to oppose each other. If the thermal and solutal buoyancies oppose each other, flow instability arises adjacent to the mush-bulk liquid interface regions. Thus, there may be a wide variety of convection situations present in the solidifying domain for different combinations of solution concentrations and externally imposed boundary conditions. The situation becomes even more complex if the solid phase movement along with the bulk flow is involved in the process, leading to multiphase convection. Detachment of solid phase from the solid/liquid interface can be caused by remelting (solutal and/or thermal) and shearing action of a convecting liquid adjacent to the interface. Depending on the drag of the bulk flow and the density of the solid phase relative to that of the bulk liquid, these detached particles can either float or sediment. The redistribution of the rejected solute by means of diffusion (at a local scale) and thermo-solutal convection (at system level length scales) causes heterogeneous orientation of mixture constituents over the solidifying domain popularly known as macro-segregation. From the point of view of manufacturing, severe form of macro-segregation or heterogeneous species distribution is an undesirable phenomenon and hence, a thorough understanding of the species redistribution by means of diffusion and convection during solidification process is very important. Most of the earlier studies on double diffusive convection during solidification involved fixed dendrites. However, the advection of solid particles during the solidification process can generate major instability in the flow pattern while modifying the solid front growth, and hence the macro-segregation pattern considerably. With this viewpoint in mind, the overall objective of the present work is to address these wide-varieties of single phase and multi phase flow situations and their effect on solid front growth and macro-segregation during directional solidification of non-eutectic binary alloys, numerically as well as experimentally. Different configurations of directional solidification processes involving double diffusive convection have been studied for two different kinds of non-eutectic solutions. While solidification of hypoeutectic solutions leads to aiding type double diffusive convection, the solidification of hyper-eutectic solutions is characterized by opposing type double diffusive convection. Solidification of hypo-eutectic solution generally involves single phase flow, while most of the hyper-eutectic solidification involves movement of solid phase (i.e. multiphase flow). As far as the modeling part is concerned, transport phenomena during solidification with multiphase convection are not common in existing literature. This work is a first attempt to develop a solidification model with multiphase flow based entirely on macroscopic parameters. As a first step, a generalized macroscopic framework has been developed for mathematical modeling of multiphase flow during solidification of binary alloy systems. The complete set of equivalent single-domain governing equations (mass, momentum, energy and species conservation) are coupled with the phase (solid and liquid) velocities. A generalized algorithm has been developed to determine solid detachment and solid advection phenomena, based on two critical parameters, namely: critical solid fraction and critical velocity. While the first of these two parameters (critical solid fraction) represents the strength of the dendritic bond, the second (critical velocity) stands for the intensity of flow to create drag force and solutal remelting at the dendrite roots. A new approach for evaluating liquid/solid fraction by using fixed grid enthalpy updating scheme, that accounts for multiphase flow and, at the same time, handles equilibrium and non equilibrium solidification mechanisms, has been proposed. The newly developed model has been validated with existing literatures as well as with experimental observations performed in the present work. The experimental results were obtained by using PIV as well as laser scattering techniques. Side cooled as well as top cooled configurations are studied. Single phase convection is observed for the case of hypo-eutectic solution, whereas hyper-eutectic solutions involve convection with movement of solid phase. For the case of bottom cooled hyper-eutectic solution, finger-like convection leading to freckle formation is observed. For all the hyper-eutectic cases, solid phase movement is found to alter the convection pattern and final macrosegregation significantly. The numerical results are compared with experimental observations both qualitatively as well as quantitatively.

No description available.

Made available in DSpace on 2014-06-11T19:26:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-07-23Bitstream added on 2014-06-13T20:07:34Z : No. of bitstreams: 1 canizella_r_me_bauru.pdf: 668494 bytes, checksum: ab160da0c27972ddf4f1aa98cece12c9 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As atividades de uma indústria com o sistema de produção contínua possuem características próprias dependendo do processo a que se dispõe a transformar uma matéria-prima, por isso este trabalho trata de analisar as perdas na produção contínua de extração de óleo de soja por solvente, apresentando a descrição do processo e as principais indicadores de desempenho, propondo sugetões de monitoramento para melhoria dos resultados. Essa abordagem é feita comparando-se resultados propiciados por alguns autores da área com dados da área com dados levantados de uma empresa no Brasil em dois períodos distintos, incluindo análise de evolução da planta, onde a alta gerência monitora a produtividade e a qualidade dos produtos, e trata as perdas no ambiente de transformação como consumo de solvente utilizado para extração do óleo de soja e consumo de combustível para a geração de energia térmica. Conclui-se que a indústria de extração de óleo vegetal, possui diversas variáveis de controle pelo conjunto de operações necessárias à transformação, ressaltando neste caso a perda de energia térmica como prioridade de atitudes de melhorias. Dado que a tendência de aumento da capacidade de processamento de soja é evidente, pela perspectiva de crescimento da produção de soja no Brasil, deve ser considerado neste contexto, o investimento em conhecimento para as pessoas exercerem as atividades operacionais em perfeita sincronia com as informações que ocorrem no processo, garantindo o objetivo da organização de minimização das perdas, e consequente aumento do lucro e crescimento / The activities of the industry with a continuous production system have their own characteristics depending on the process that is willing to turn a raw material, so this work is to analyzed the losses in the continuous production of soybean oil extraction solvent, presenting the description of the process and key performance indicators and propose suggestions for the improvement of monitoring results. This approach is made comparing the results obtained by some authors in the field with data collected from a company in Brazil in two distinct periods, including examination of the plant, where top management monitors productivity and product quality, and treats losses the environment of use as processing solvent used to extract the soybean oil and fuel to generate heat energy. It is concluded that the industry of oil extraction plant has several control variables the operations required for processing, emphasizing in this case the loss of thermal energy as priority actions for improvements. Since the trend of increased processing capacity of soybean is evident from the perspective of growth of soybean production in Brazil, should be considered in this context, investment in knowledge for people to exercise operational activities in perfect synchrony with the information occur in the process, ensuring the organization's goal of minimizind losses, and consequent increase in profit and growth

Thesis (MTech (Faculty of Engineering))--Cape Peninsula University of Technology, 2009.Included bibliographical references (p. 98-99).

Orientador: Kamal Abdel Radi Ismail / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-14T07:25:07Z (GMT). No. of bitstreams: 1 Paixao_LouryvalCoelho_M.pdf: 3782849 bytes, checksum: a8900089f4a65a6ee50cdc15b2dba208 (MD5) Previous issue date: 2009 / Resumo: O processo de solidificação de um material de mudança de fase em uma região anular ao redor de um cilindro resfriado pela passagem de um fluido em seu interior é estudado numérica e experimentalmente, objetivando aplicações em sistemas de armazenamento de calor latente. A solução do problema de mudança de fase é feita utilizando o método de imobilização de fronteiras, onde se aplica a transformada de coordenadas de forma que no novo sistema a fronteira móvel e irregular seja fixa e paralela às demais. O método de volumes finitos é usado para discretização das equações do modelo matemático que em seguidas são resolvidas computacionalmente. Os experimentos são realizados para 4 temperaturas e 3 números de Reynolds do fluido de trabalho: -5, -10, -15, -20ºC e 741, 1484, 2280 respectivamente. Posteriormente, foi introduzido um promotor de turbulência helicoidal para aumentar o coeficiente de transferência de calor onde foram realizados 6 experimentos para temperaturas de -10, -15ºC e, com os mesmos números de Reynolds anteriores. Os resultados experimentais foram comparados com os resultados numéricos. / Abstract: The process of solidification of a material of change of phase in a region annular around of a cylinder cooled by fluid passing in its interior is studied numerical and experimentally, objectifying applications in systems of storage of latent heat. The boundary immobilization technique is used for solving for phase-change problem. The coordinate transformation is performed so that in the new system the moving and irregular boundary become fixes and parallel to the others. The finite-volume methodology is used discretization of the equation from the mathematical model witch are than solved by a computer program. The experiments are made for 4 temperatures and 3 Reynolds numbers of the fluid: 741, 1484, and 2280 respectively. A turbulence promoter was insert inner tube to enhancement the coefficient of heat transference, where 6 experiments were made to -10 and -15ºC temperature with the previous Reynolds numbers. The experimental results had been compared with the numerical results. / Mestrado / Termica e Fluidos / Mestre em Engenharia Mecânica