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Estudo da formação de gelo durante o armazenamento a granel de vegetais congeladosUrquiola Mujica, Ana January 2018 (has links)
Este trabalho propõe um modelo de transferência de calor e massa para prever a formação de gelo em um container preenchido com legumes congelados. O problema físico é modelado como um meio poroso composto pelo próprio produto e o ar em seu entorno. O regime de convecção natural é assumido dentro do container, o qual promove o transporte de massa. Como uma primeira validação, o modelo é simulado considerando diferentes temperaturas de ar externo, causadas por flutuações da vizinhança. Resultados para quatro ciclos de temperaturas foram comparados, variando separadamente a temperatura média do ar, amplitude e frequência de oscilação. De modo geral, é observado que a temperatura do produto se comporta assim como era esperado e este resultado é diretamente associado à formação de gelo dentro do container. A formação de gelo cresce com uma maior amplitude de oscilação, porém decresce com um aumento na frequência e na temperatura média. Os parâmetros do modelo foram obtidos para dois diferentes produtos: fatias de cenouras congeladas e vagens congeladas, ambos em meio ao ar. As definições de parâmetros são oriundas de revisão bibliográfica, medições experimentais e simulações numéricas. Os parâmetros encontrados para a caracterização desses meios porosos foram similares para ambos os produtos, mesmo eles possuindo diferentes geometrias. A validação experimental foi feita para as fatias de cenoura considerando dois ciclos de temperatura O modelo numérico é capaz de prever o campo de velocidades do ar, as temperaturas do produto e a formação de gelo local. Os resultados foram validados em relação a um grupo independente de resultados numéricos, tal comparação apresentou uma boa concordância. A circulação de ar encontrada é, de fato, devido à convecção natural. O comportamento da temperatura dos produtos simulados concorda com os valores medidos e os valores de temperaturas diferem por menos de 12%. Com respeito à formação de gelo, o modelo é capaz de prevê-la corretamente nas regiões mais suscetíveis a este fenômeno. Porém, a quantidade de gelo formado prevista pelo modelo (1,56 g/semana) é menor do que a experimental (4,67 g/semana), apesar de serem de mesma ordem de magnitude. O efeito de cada parâmetro no modelo é estudado visando detectar maneiras de aprimorar o modelo. Foi encontrado que os parâmetros mais importantes para a formação de gelo total são a difusividade de massa efetiva e o coeficiente de transferência de calor convectivo dentro do container. Ajustando estes parâmetros duas vezes foi possível encontrar resultados melhores com respeito à formação de gelo (3,09 g/semana). / A model of heat and mass transfer is proposed in order to predict frost formation into a closed container filled with frozen vegetables. The physical problem is modeled as a macroporous media composed by the product itself and the surrounding air. Natural convection air flow is assumed into the container, who promotes water mass transport. As a first validation, the model is simulated for several exterior air temperatures, under environmental fluctuations (boundary conditions). Results of four temperature cycles were compared, varying average air temperature, amplitude and frequency of oscillation, one by one. As a general result, it is observed that the product temperature behavior is as expected, and it is directly associated with frost formation into the container. Frost formation increases with large amplitude of oscillation, but decreases with higher frequencies and higher mean temperatures. Model parameters were obtained for two assembling: frozen slices of carrots and air, and frozen extra thin green beans and air. Parameter definition and evaluation combines literature review, measurements and numerical simulation. In general, parameters which characterize these porous media were similar for both products, even though they display different geometries. The experimental validation is performed for carrot slices with two temperature cycles The numerical model is able to predict air velocity field, air and product temperatures, and local frost formation. Results are validated in respect to a set of independent experimental results that shown a good agreement. Air flow circulation is as expected due to natural convection. Product temperature simulated behavior agrees with measurements, and temperature values differ by less than 12%. Respect to frost formation predictions, the model predicts correctly the most susceptible regions to frost formation. However, the quantity of frost formed predicted by the model (1.56 g/ week)is lower than the experimental one (4.67g/week), despite being of the same order of magnitude. The effect of each parameter in the model is study in order to detect how to improve the model. The most important parameters affecting total frost formation are effective mass diffusivity and convective heat coefficient into the storage container. Adjusting these parameters to twice, better results in terms of frost formation could be obtained (3.09 g/ week).
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Otimização evolucionária e topológica em problemas governados pela equação de Poisson empregando o método dos elementos de contornoAnflor, Carla Tatiana Mota January 2007 (has links)
Este trabalho apresenta o desenvolvimento e implementação computacional de técnicas de otimização de topologia para problemas governados pela equação de Poisson. O método numérico utilizado para solução numérica das equações foi o método dos elementos de contorno (MEC). Para tanto, três metodologias foram desenvolvidas. A primeira é direcionada à aplicação de algoritmos genéticos (AG) para investigar como um domínio inicialmente preenchido com cavidades aleatórias evolui durante um processo de otimização e verificar a possibilidade de se extrair topologias ótimas a partir da interpretação da solução encontrada. Os contornos externos permanecem fixos enquanto as posições e as dimensões das cavidades são otimizadas com o objetivo extremizar uma função custo especificada. O desempenho do algoritmo proposto é ilustrada com uma série de exemplos e os resultados são discutidos. A segunda metodologia apresenta um algoritmo numérico para otimização topológica baseado na avaliação da derivada topológica (DT), adotando a energia potencial total como função custo. Este procedimento é uma alternativa às tradicionais técnicas de otimização, evitando assim soluções de projeto com densidade de material intermediária. Sólidos com comportamento anisotrópico são estudados sob condições de contorno de Robin, Neumann e Dirichlet. Uma transformação linear de coordenadas é utilizada para mapear o problema original e suas condições de contorno para um novo domínio equivalente isotrópico, onde o procedimento de otimização é aplicado. A solução otimizada é então transformada de volta ao domínio original. A metodologia proposta mostrou-se particularmente atrativa para resolver esta classe de problemas já que o MEC dispensa o uso de malha no domínio, reduzindo significantemente o custo computacional. Na última parte deste trabalho foi implementada uma formulação de sensibilidade topológica para problemas de otimização de transferência de calor e massa simultâneos. Como as sensibilidades para cada equação diferencial são diferentes, utiliza-se um coeficiente de ponderação para compor a sensibilidade do problema acoplado. Isto permite a imposição de distintos fatores para cada problema, de acordo com uma prioridade especificada. Diversos exemplos são apresentados e seus resultados comparados com os da literatura, quando disponíveis, a fim de validar as formulações propostas. / This work presents the computational development and implementation of topology optimization techniques for problems governed by the Poisson equation. The boundary element method was the numerical technique chosen to solve the equations. Three different methodologies were developed aiming this objective. The first methodology is directed to the application of genetic algorithms to investigate how a domain previously populated with randomly placed cavities evolves during the optimization process, and to verify the resemblance of the final solution with a optimal design. The external boundaries remain fixed during the process, while the location and dimension of the cavities are optimized in order to extremize a given cost function. The performance of the proposed algorithm is verified with a number of examples and the results are discussed. The second methodology presents a numerical algorithm for topology optimization based on the evaluation of topological derivatives, using the total potential energy as the cost function. This procedure is an alternative to the traditional optimization techniques, avoiding design solutions containing intermediary material densities. Solids with anisotropic constitutive behavior are studied under Robin, Neumann and Dirichlet boundary conditions. A linear coordinate transformation approach is used to map the original problem into an isotropic one, where the optimization is carried out. The final solution is then mapped back to the original coordinate system. The proposed method was found to be an attractive way to solve this class of problems, since no interior mesh is necessary, which reduces significantly the computational cost of the analysis. In the last part of the present work the topological derivative approach was further developed to deal with the optimization of problems under simultaneous heat and mass transfer. Since the sensitivities for each differential equation are different, a weighting factor was used to evaluate the final sensitivities of the coupled problem. This allows the imposition of different priorities for each problem Several examples are presented and their results are compared with the literature, when available, in order to validate the proposed formulations.
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Optimisation topologique des transferts de chaleur et de masse : application aux échangeurs de chaleur / Topological optimization of heat and mass transfer : application to heat exchangersMarck, Gilles 21 December 2012 (has links)
Les transferts de chaleur et de masse sont deux phénomènes physiques à la base de nombreux systèmes thermiques employés dans des secteurs variés tels que l'industrie, le bâtiment ou encore les énergies renouvelables. Les présents travaux de recherche envisagent différentes méthodologies d'optimisation de configurations assurant le transfert de flux de chaleur, couplé ou non à un écoulement fluide, au sens topologique du terme. Les équations aux dérivées partielles décrivant les phénomènes physiques sont discrétisées avec la méthode des volumes finis. La première partie du manuscrit examine successivement trois classes différentes de méthodes: la théorie constructale, les automates cellulaires et les méthodes par pénalisation. Le même cas académique, portant sur le refroidissement d'un volume fini générant de la chaleur, est résolu au moyen de ces trois méthodes, ce qui permet ainsi de comparer les performances de chaque algorithme. Cette comparaison démontre l'ascendant des méthodes par pénalisation sur les deux premiers types, tant structurellement que quantitativement, et permet également d'établir des solutions basées sur des compromis dans le cadre d'optimisations multi-objectifs. Par conséquent, la seconde partie envisage l'application de cette approche à des configurations réalisant des transferts de chaleur conducto-convectifs en régime laminaire. L'utilisation de paramètres de pénalisation en conjonction avec les volumes finis requiert une régularisation de la dissipation visqueuse le long de l'interface fluide/solide. Une approche bi-objectif est développée visant à minimiser la puissance dissipée par le fluide, tout en maximisant l'énergie thermique récupérée sur le système. Les solutions obtenues adoptent des configurations non-triviales qui sont divisibles en quatre classes topologiques différentes. La thèse ouvre ainsi un nouveau champ d'investigation pour l'optimisation d'écoulements couplés à la problématique du transport de chaleur. / Heat and mass transfers are two physical phenomena at the base of many thermal systems involved in various fields, such as industries, buildings or renewable energies. The present researches tackle different optimization methodologies of structures subject to heat transfers, coupled with a fluid flow or not, in the topological sense of the term. The partial differential equations describing the physical phenomena are discretized thanks to the finite volume method. The first part of the thesis successively studies three different classes of approaches: constructal theory, cellular automaton, and the solid isotropic material with penalization method. The same academic case, aiming at the optimal cooling of a finite-size volume generating heat, is tackled by means of these three methods, allowing the comparison of the performances of each algorithm. This comparison shows that the method based on the material penalization performs better than the first two approaches, structurally and quantitatively, and also establishes solutions based on a trade-off in the frame multi-objective optimization. Consequently, the second part applies this method to configurations subject to heat and mass transfers with laminar flows. The use of penalization parameters in conjunction with the finite volume method requires a regularization of the viscous dissipation along the solid/fluid interfaces. A bi-objective approach is implemented in order to minimize the total power dissipated by the fluid, while maximizing the thermal energy recovered from the system. The solutions show non-trivial configurations that can be categorized in four different topological classes. The present researches open a new investigation field for fluid flows coupled with the problem of heat transport.
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Improving the Energy Efficiency of Ethanol Separation through Process Synthesis and SimulationHaelssig, Jan B. January 2011 (has links)
Worldwide demand for energy is increasing rapidly, partly driven by dramatic economic growth in developing countries. This growth has sparked concerns over the finite availability of fossil fuels and the impact of their combustion on climate change. Consequently, many recent research efforts have been devoted to the development of renewable fuels and sustainable energy systems. Interest in liquid biofuels, such as ethanol, has been particularly high because these fuels fit into the conventional infrastructure for the transportation sector.
Ethanol is a renewable fuel produced through the anaerobic fermentation of sugars obtained from biomass. However, the relatively high energy demand of its production process is a major factor limiting the usefulness of ethanol as a fuel. Due to the dilute nature of the fermentation product stream and the presence of the ethanol-water azeotrope, the separation processes currently used to recover anhydrous ethanol are particularly inefficient. In fact, the ethanol separation processes account for a large fraction of the total process energy demand.
In the conventional ethanol separation process, ethanol is recovered using several distillation steps combined with a dehydration process. In this dissertation, a new hybrid pervaporation-distillation system, named Membrane Dephlegmation, was proposed and investigated for use in ethanol recovery. In this process, countercurrent vapour-liquid contacting is carried out on the surface of a pervaporation membrane, leading to a combination of distillation and pervaporation effects. It was intended that this new process would lead to improved economics and energy efficiency for the entire ethanol production process.
The Membrane Dephlegmation process was investigated using both numerical and experimental techniques. Multiphase Computational Fluid Dynamics (CFD) was used to study vapour-liquid contacting behaviour in narrow channels and to estimate heat and mass transfer rates. Results from the CFD studies were incorporated into a simplified design model and the Membrane Dephlegmation process was studied numerically. The results indicated that the Membrane Dephlegmation process was more efficient than simple distillation and that the ethanol-water azeotrope could be broken. Subsequently, a pilot-scale experimental system was constructed using commercially available, hydrophilic NaA zeolite membranes. Results obtained from the experimental system confirmed the accuracy of the simulations.
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Modelagem de um absorvedor tubular em espiral de Brometo de Lítio-ÁguaGALLO, Aida Marelyn Avendaño 29 January 2016 (has links)
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Previous issue date: 2016-01-29 / PRH-PB203 EQUIPAMENTOS/PETROBRAS / O processo de transferência de calor e massa dentro de um absorvedor tubular em espiral
de Brometo de Lítio-Água (LiBr/H2O), resfriado com água em contracorrente, foi simulado
usando um modelo matemático não linear. Para a simulação criou-se um programa em Matlab,
usando o método numérico iterativo. Na calibração da malha física foram utilizadas condições
de trabalho do absorvedor e o coeficiente de transferência de massa efetivo, Kef, obtidos da
literatura. O coeficiente de transferência de calor global, U, foi calculado usando a resistência
térmica global dentro do absorvedor. Para o cálculo do coeficiente de transferência de massa e
de calor da interface solução-vapor se utilizaram correlações de analogia de transferência de
calor e massa. As distribuições da temperatura e concentração da solução de LiBr/H2O, e a
temperatura da água de resfriamento ao longo do comprimento do absorvedor foram
determinadas utilizando o programa desenvolvido e os resultados obtidos apresentaram uma
boa concordância quando comparados com dados reportados na literatura. Finalmente, foi
analisada a influência da variação de alguns dos parâmetros, tais como temperatura e vazão de
entrada da água de resfriamento, comprimento do absorvedor e material do tubo absorvedor
dentro do absorvedor utilizando o programa desenvolvido. Os resultados obtidos mostraram
que o programa desenvolvido permite predizer o comportamento do processo de transferência
de massa e calor dentro do absorvedor em espiral de LiBr/H2O, além de representar uma
ferramenta para o dimensionamento e/ou otimização deste componente. / The mass and heat transfer process in a spiral tubular absorber of the Water/Lithium
Bromide (LiBr/H2O), cooled with in counter-current, was simulated using a nonlinear
mathematical model. For the simulation was developed a program in Matlab, using the iterative
numerical method. For the calibration of physical mesh were used absorber working condition
and effective mass transfer coefficient, Kef, obtained from the literature. The global heat transfer
coefficient, U, was calculated using the global thermal resistance within the absorber. For the
calculation of the mass and heat transfer coefficient of the interface vapor-solution are used
analogy correlations of mass and heat transfer. The temperature distribution and concentration
of LiBr/H2O, and the cooling water temperature along of the length of the absorber were
determined using the program developed, and the result obtained showed good agreement when
compared to the data reported in the literature. Finally, the influence of the variation the some
parameters were analyzed, such as inlet temperature and mass flow of cooling water, length
of the absorber and material absorber tube within the absorber using the developed program.
The result obtained showed that this program allowed to predict the behavior of the mass and
heat transfer process in the absorber spiral of the LiBr/H2O, also represents a tool for the design
and/or optimization of this component.
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Thermal Metrology for Waste Heat Systems: Thermoelectrics to Phase Change MaterialsCollier S Miers (6640934) 25 June 2020 (has links)
This dissertation presents the development of two unique measurement platforms. <br><br>The first system is a high-temperature Z-Meter. This system is designed to simultaneously measure the electrical resistivity, Seebeck coefficient, and thermal conductivity of a thermoelectric sample to accurately determine the figure of merit, ZT, for that material. It is designed to operated at sample temperatures of up to 1000C, and with temperature gradients on the order of 500C across the sample. This system also provides <i>in situ</i> load monitoring for contact pressure and allows the user to adjust loading during the experiment. <br><br>The second part of this dissertation focuses on the development of enhanced composite phase change material (PCM) heat sinks to improve passive thermal management in mobile electronics. We present a new design for a composite PCM heat sink and utilize off-the-shelf PCMs to show characterize the performance. In order to accurately investigate the performance enhancement of these designs, we develop a turn-key thermal management evaluation platform to allow the user complete control over the power profiles and cycling applied to the test chip, as well as providing <i>in situ</i> temperature monitoring within the chip. The proposed package designs show significant improvement in the length of time extended before reaching the cut-off temperature within the heatfluxes tested, 6 - 14 W/cm^2, and accomplish this while weighing less than the equivalent sensible heat storage design.<br><br><br><br>
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ON HEAT TRANSFER MECHANISMS IN SECONDARY COOLING OF CONTINUOUS CASTING OF STEEL SLABHaibo Ma (11173431) 23 July 2021 (has links)
<p>Secondary cooling during continuous casting is a delicate
process because the cooling rate of water spray directly affects the slab
surface and internal quality. Undercooling may lead to slab surface bulging or
even breakout, whereas overcooling can cause deformation and crack of slabs due
to excessive thermal residual stresses and strains. Any slab which does not
meet the required quality will be downgraded or scrapped and remelted. In order to remain competitive and continuously
produce high-quality and high-strength steel at the maximum production rate,
the secondary cooling process must be carefully designed and controlled. Efficient
and uniform heat removal without deforming or crack the slab is a significant
challenge during secondary cooling. In the meantime, the on-site thermal
measurement techniques are limited due to the harsh environment. In contrast, experimental measurements
are only valid for the tested conditions, and the measurement process is not
only labor-intensive, but the result might be inapplicable when changes in the
process occur. On the other hand, the high-performance computing (HPC)-powered
computational fluid dynamics (CFD) approach has become a powerful tool to gain
insights into complex fluid flow and heat transfer problems. Yet, few
successful numerical models for heat transfer phenomena during secondary
cooling have been reported, primarily due to complex phenomena. </p>
<p> </p>
<p>Therefore, the current study has proposed two
three-dimensional continuum numerical models and a three-step coupling
procedure for the transport of mass, momentum, and energy during the secondary
cooling process. The first numerical model features the simulation of water
spray impingement heat and mass transfer on the surface of a moving slab considering
atomization, droplet dispersion, droplet-air interaction, droplet-droplet
interaction, droplet-wall impingement, the effect of vapor film, and droplet
boiling. The model has been validated against five benchmark experiments in
terms of droplet size prior to impingement, droplet impingement pressure, and
heat transfer coefficient (HTC) on the slab surface. The validated model has
been applied to a series of numerical simulations to investigate the effects of
spray nozzle type, spray flow rate, standoff distance, spray direction, casting
speed, nozzle-to-nozzle distance, row-to-row distance, arrangement of nozzles,
roll and roll pitch, spray angle, spray water temperature, slab surface
temperature, and spray cooling on the narrow face. Furthermore, the simulation
results have been used to generate a mathematically simple HTC correlation,
expressed as a function of nine essential operating parameters. A graphic user
interface (GUI) has been developed to facilitate the application of
correlations. The calculated two-dimensional HTC distribution is stored in the universal
comma-separated values (csv) format, and it can be directly applied as a boundary
condition to on-site off-line/on-line solidification calculation at steel mills.
The proposed numerical model and the generic methodology for HTC correlations should
benefit the steel industry by expediting the development process of HTC
correlations, achieving real-time dynamic spray cooling control, supporting
nozzle selection, troubleshooting malfunctioning nozzles, and can further
improve the accuracy of the existing casting control systems.</p>
<p> </p>
<p>In the second numerical model, the volume-averaged
Enthalpy-Porosity method has been extended to include the slurry effect at low
solid fractions through a switching function. With the HTC distribution on the
slab surface as the thermal boundary condition, the model has been used to
investigate the fluid flow, heat transfer, and solidification inside a slab
during the secondary cooling process. The model has been validated against the
analytical solution for a stationary thin solidifying body and the simulation
for a moving thin solidifying body. The effects of secondary dendrite arm
spacing, critical solid fraction, crystal constant, switching function
constant, cooling rate, rolls, nozzle-to-nozzle distance, and arrangement of
nozzles have been evaluated using the validated model. In addition, <a>the solidification model has been coupled with the
predictions from the HTC correlations, and the results have demonstrated the availability
of the correlations other than on-site continuous casting control. </a>Moreover,
the model, along with
the three-step coupling procedure, has been applied to simulate the initial
solidification process in continuous casting, where a sufficient cooling rate
is required to maintain a proper solidification rate. Otherwise, bulging or
breakout might occur. The prediction is in good agreement with the
measured shell thickness, which was obtained from a breakout incident. With the help of
HPC, such comprehensive simulations will continue to serve as a powerful tool
for troubleshooting and optimization.</p>
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EXPERIMENTAL AND NUMERICAL ANALYSIS OF ENVIRONMENTAL CONTROL SYSTEMS FOR RESILIENT EXTRA-TERRESTRIAL HABITATSHunter Anthony Sakiewicz (15339325) 22 April 2023 (has links)
<p> As space exploration continues to advance, so does the drive to inhabit celestial bodies. In<br>
order to expand our civilization to the Moon or even other planets requires an enormous amount of research and development. The Resilient Extra-Terrestrial Habitat Institute is a NASA funded project that aims to develop the technology needed to establish deep-space habitats. Deep-space inhabitation poses many challenges that are not present here on earth. The Moon, for example, has temperatures that range from -233−123°C. Aside from the extreme temperatures, a variety of thermal loads will need to be handled by the Environmental Control and Life Support System (ECLSS). Aside from the research and architecture of the International Space Station’s ECLSS, very little information is known about disturbances related to the thermal management of extra- terrestrial habitats.<br>
</p>
<p>RETHi is developing a Cyber-Physical Testbed (CPT) that represents a one-fifth scale<br>
prototype of a deep space habitat. In order to answer difficult research questions regarding ECLSS and thermal management of a deep-space habitat, a heat pump was modeled and validated with the physical part of the CPT. Once validated, the heat pump model is able to accurately predict the steady state behavior given the indoor and outdoor conditions of the testbed. When coupled with the interior environment (IE) model, it gives insight into the system’s requirements and response. Experimental testing was conducted with the heat pump in order to validate the model. After the model was validated, a series of parametric studies were conducted in order to investigate the effects of varying thermal loads and dehumidification. Since the groundwork was laid through model development and experimentation, future work consists of designing a more versatile heat pump to test a variety of disturbance scenarios. Although the heat pump model is specifically designed for the CPT, it proves to be versatile for other closed and pressurized environments such as aircraft and clean rooms according to the analysis of dehumidification and dependence on pressure. </p>
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3D PRINTING SUPPRESSORFOR SMALL ARMSUSING FUSEDDEPOSITIONMODELINGRichard Collin Sinclair (15349201) 29 April 2023 (has links)
<p> </p>
<p>Metal 3D printing is the industry standard for manufacturing experimental suppressors due to the limitations of conventional, subtractive machining methods. Long print times, difficulty sintering, and cleaning of metal 3D printed suppressor components limit the development time. Plastic printed components are able to be produced quicker, safer, and at a lower cost than their metal 3D printed counterparts. Reducing the time and cost of manufacturing will allow for an increased pace of innovations in suppressor design.</p>
<p><br></p>
<p>Utilizing Finite Element Analysis (FEA) in combination with Computational Fluid Dynamics (CFD) will expedite the process of designing 3D printed plastic suppressors. Solidworks FEA determined the maximum stress applied to the blast chamber of the plastic suppressor. ANSYS Fluent CFD simulations were used to qualitatively compare the sound pressure levels of an unsuppressed and suppressed 22LR pistol. Comparing the results of the CFD simulations gave insight into the effectiveness of the selected baffle structure.</p>
<p><br></p>
<p>A prototype 3D printed suppressor was optimized for strength according to manufacturing practices for printed plastic small arms. Testing occurred at an indoor range where peak impulse noise was measured for an unsuppressed 22LR pistol and a plastic printed suppressor. The printed suppressor reduced the small arms impulse noise from 150.5 dB(spl) to 132.4 dB(spl). Impulse noises below the pain threshold of 140 dB(spl) do not require hearing protection for operation. Utilizing FEA, CFD, and FDM prototyping methods in this work has laid the foundation for future works in the rapid prototyping and optimizations of suppressors for small arms.</p>
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Etudes expérimentales des transferts de masse et de chaleur dans les parois des constructions en bois, en vue de leur modélisation. Applications aux économies d'énergie et au confort dans l'habitat / Experimental studies on heat and mass transfer in walls of timber constructions, for validation of computational models. Application to energy savings and indoor comfortRafidiarison, Helisoa Mamy 17 July 2012 (has links)
Les matériaux hygroscopiques, et tout particulièrement le bois et ses dérivés possèdent des propriétés complexes rendant difficile la modélisation des transferts couplés de chaleur et de masse dans les parois incluant ces matériaux. De ce fait, très peu d'outils numériques sont aujourd'hui capables de prédire correctement la performance hygrothermique de l'habitat bois. L'objectif de ce travail est de caractériser expérimentalement les transferts chaleur-masse dans les parois des constructions bois afin de valider un outil numérique destiné à simuler le comportement hygrothermique des parois comportant des matériaux hygroscopiques. Dans un premier temps, les notions théoriques et les études antérieures sur les transferts couplés chaleur - masse sont présentés. Ensuite, nous donnons un descriptif détaillé du dispositif expérimental conçu pour caractériser les transferts couplés chaleur-masse dans les parois. Les expériences de caractérisation des performances hygrothermiques des parois fournies par les industriels partenaires du projet TRANSBATIBOIS dans lequel s'inscrit cette thèse sont également abordées. Nous détaillons par la suite les expériences réalisées ainsi que la phase de confrontation des résultats expérimentaux avec les résultats prédits par le code numérique BuildingPore et l'outil commercial WUFI. La troisième partie de ce travail est consacrée aux expérimentations à l'échelle de l'enveloppe. Nous y présentons une analyse de la performance hygrothermique et des consommations énergétiques des constructions bois à travers le suivi de modules-test exposés au climat extérieur. La dernière partie du travail est consacrée aux dispositifs de suivi de bâtiments. / Coupled heat and moisture transfer through hygroscopic materials, particularly wood and wood-based products are difficult to model. This is partly due to some specific and complex properties of these materials that are often not included in numerical models. Currently, only a few numerical models are able to predict accurately the hygrothermal performance of wooden building envelope. The aim of this work is to assess the heat and moisture transfer in wooden building envelope through experiments and validate the prediction capacity of a numerical model developed to simulate hygrothermal behavior of envelope including wooden materials. After giving a theoretical reminder of the coupled heat and moisture transfer through building envelope and reporting the results of previous studies in this field, we will give details of the experimental investigation on heat and moisture transfer through timber walls. Firstly, the experimental apparatus used for the wall tests is presented. Then, we will analysis the hygrothermal performance of wooden walls provided by the partners of the TRANSBATIBOIS project in which this work was achieved. Experimental works achieved for Buildingpore model validation and results of the comparisons between experimental assessment and numerical predictions with Buildingpore and WUFI are also reported. The third part of this study deals with the experimental assessment of wooden building envelopes exposed to climatic conditions. An analysis of the hygrothermal performance and the energy consumption of wooden test-cells is performed and reported in this part. The latest part concerns experimental works on buildings.
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