The behavior of aluminum alloy ship deck panels under the thermal loads of Vertical Take-off-and Landing (VTOL) capable aircraft has become a question of interest with the introduction of new primarily aluminum alloy ships to the U.S. Naval Fleet. This study seeks to provide an initial investigation of this question by examining the transient transfer of heat through aluminum alloy ship deck panels under application of the local heat transfer similar to that of a VTOL aircraft exhaust plume core in typical operation. In this study, a jet stream intended to replicate the key physics of the core of a VTOL aircraft plume was impinged onto the upper surface of aluminum alloy corrugated deck panel test specimen. Temperature measurements are taken via thermocouples on the face of the specimen opposite the impingement to evaluate heat transfer through the specimen. This data is used to assess the effects of variation in the geometry of the corrugation between specimen. Qualitative temperature distributions were also gathered on the impingement surface via thermal imaging. A quantitative assessment of the heat paths for transverse and vertical heat transfer was made based on a thermal resistance model, leading to a conceptual description of predominant heat flow paths in the specimen, specifically weld lines between the corrugation and the flat plate surfaces. In support of this, thermal images indicated that the weld lines provided paths for heat to be pulled away from the center of heat application more rapidly than over the rest of the surface. Ultimately, heat transfer through the specimen was found to be more dependent on the flow conditions than the variations in geometry of the deck panels due to the low variation in thermal resistance across the plate. A recommendation is made based upon this observation to use the deck panels similarly to heat exchanges by adding a small amount of through-deck airflow in the areas of high heat load. / Master of Science

High Efficiency Deep Grinding (HEDG) combines high depths of cut, high grinding wheel speeds with high work piece feed rates to deliver a very high stock removal process that can produce components free of surface damage. High contact temperatures are a characteristic of the process and this produces a mass of hot grinding sparks being ejected from the grinding zone. Neat oil cutting fluids are typically used in HEDG due to their excellent lubricity, but the high grinding wheel speeds employed leads to high levels of highly volatile cutting fluid mist in the machine canopy. This mist can mix with the hot grinding sparks being ejected from the grinding zone to create a potential fire hazard. The project aim was to produce a cutting fluid application strategy for the HEDG regime, focusing on establishing the thermal characteristics of cutting fluids in order to determine the optimum cutting fluid for the HEDG process. The cutting fluid application strategy also involved investigating the optimum means by which to apply the cutting fluid, based on minimising amount of cutting fluid used in the process and in reducing the potential fire hazard. The characteristics that have a thermal impact on the grinding process are the cooling, lubrication, ignition and misting properties of the fluid. A series of tests were established to investigate these properties and therefore allow different fluids to be compared and contrasted for their suitability for the HEDG regime based. Once an optimal cutting fluid had been established, the project then investigated the optimal method of applying this fluid, with particular reference to the type and design of the nozzle used to apply the fluid to the grinding zone. As part of these trials, a series of benchmark tests were also conducted using long established cutting fluid application techniques to enable the benefits of the new strategy to be evaluated. The project concluded that high viscosity neat oil ester based cutting fluids were the best fluids to be used in the HEDG regime due to they excellent lubricity and low misting properties coupled to their relatively high resistance to ignition when compared to neat mineral oils. The studies also found that using a high viscosity ester based fluid and then applying it using a coherent jet nozzle, significant reductions in the grinding powder and specific grinding energy could be achieved whilst significantly lowering the amount of mist in the machine, thus reducing the potential fire hazard and the volume of cutting fluid used by the process.

Gas sensors are today used in many different application areas, and one growing future market is battery operated sensors. As many gas sensor components are heated, one major limit of the operation time is caused by the power dissipated as heat. AppliedSensor is a company that develops and produces gas sensor components, modules and solutions, among which battery operated gas sensors are one targeted market. The aim of the diploma work has been to simulate the heat transfer on a hydrogen gas sensor component and its closest surroundings consisting of a carrier mounted on a printed circuit board. The component is heated in order to improve the performance of the gas sensing element. Power dissipation occurs by all three modes of heat transfer; conduction from the component through bond wires and carrier to the printed circuit board as well as convection and radiation from all the surfaces. It is of interest to AppliedSensor to understand which factors influence the heat transfer. This knowledge will be used to improve different aspects of the gas sensor, such as the power consumption. Modeling and simulation have been performed in FEMLAB, a tool for solving partial differential equations by the finite element method. The sensor system has been defined by the geometry and the material properties of the objects. The system of partial differential equations, consisting of the heat equation describing conduction and boundary conditions specifying convection and radiation, was solved and the solution was validated against experimental data. The convection increases with the increase of hydrogen concentration. A great effort was made to finding a model for the convection. Two different approaches were taken, the first based on known theory from the area and the second on experimental data. When the first method was compared to experiments, it turned out that the theory was insufficient to describe this small system involving hydrogen, which was an unexpected but interesting result. The second method matched the experiments well. For the continuation of the project at the company, a better model of the convection would be a great improvement.

<p>Gas sensors are today used in many different application areas, and one growing future market is battery operated sensors. As many gas sensor components are heated, one major limit of the operation time is caused by the power dissipated as heat. AppliedSensor is a company that develops and produces gas sensor components, modules and solutions, among which battery operated gas sensors are one targeted market.</p><p>The aim of the diploma work has been to simulate the heat transfer on a hydrogen gas sensor component and its closest surroundings consisting of a carrier mounted on a printed circuit board. The component is heated in order to improve the performance of the gas sensing element.</p><p>Power dissipation occurs by all three modes of heat transfer; conduction from the component through bond wires and carrier to the printed circuit board as well as convection and radiation from all the surfaces. It is of interest to AppliedSensor to understand which factors influence the heat transfer. This knowledge will be used to improve different aspects of the gas sensor, such as the power consumption.</p><p>Modeling and simulation have been performed in FEMLAB, a tool for solving partial differential equations by the finite element method. The sensor system has been defined by the geometry and the material properties of the objects. The system of partial differential equations, consisting of the heat equation describing conduction and boundary conditions specifying convection and radiation, was solved and the solution was validated against experimental data.</p><p>The convection increases with the increase of hydrogen concentration. A great effort was made to finding a model for the convection. Two different approaches were taken, the first based on known theory from the area and the second on experimental data. When the first method was compared to experiments, it turned out that the theory was insufficient to describe this small system involving hydrogen, which was an unexpected but interesting result. The second method matched the experiments well. For the continuation of the project at the company, a better model of the convection would be a great improvement.</p>

Made available in DSpace on 2016-12-12T20:25:12Z (GMT). No. of bitstreams: 1 Maico Jeremias da Silva.pdf: 5502697 bytes, checksum: 292822b79334828b19d2d99087aae96b (MD5) Previous issue date: 2015-07-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work discusses the behaviour of the convection heat transfer coefficient in plane fins with variation of air flow velocity and fin spacing. The differential equation that governs heat transfer in fins is discretized by the finite volume method, which enables computation of the fin thermal characteristics, such as temperature distribution, heat transfer and fin efficiency. The determination of the convection coefficient, important parameter for thermal analysis, is performed by applying a heuristic optimization method, known as Particle Swarm Optimization, which combines data measured from experimental analysis conducted in wind tunnel with the aforementioned heat transfer numerical approximation of fins. / Este trabalho analisa os efeitos da velocidade do escoamento de ar e do espaçamento entre aletas no coeficiente de convecção forçada sobre as superfícies de aletas planas. As equações diferenciais que definem a transferência de calor em aletas são discretizadas pela técnica de volumes finitos possibilitando a determinação das características térmicas da aleta, tais como perfil de temperatura, calor transferido e eficiência térmica. A determinação do coeficiente de convecção, parâmetro fundamental para análises térmicas, é realizada mediante a aplicação de um método de otimização heurístico, conhecido como Método do Enxame de Partículas, que combina os dados obtidos da análise experimental realizada em túnel de vento com a aproximação numérica da troca de calor na aleta descrita acima