Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: 4 l. at end.

Orientadores: Paulo Roberto Gardel Kurka, Kamal A. R. Ismail / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-28T16:10:56Z (GMT). No. of bitstreams: 1 AraujoFilho_BeneditoSade_D.pdf: 5884845 bytes, checksum: 9d32465225c3d77bcef03cb8d144fad0 (MD5) Previous issue date: 1999 / Resumo: O objetivo desta pesquisa é elaborar técnicas e critérios para a projeção de desvios de calibração e estudo de confiabilidade nas medidas de termopares. Propõe-se a criação de um modelo baseado no estudo dos desvios das curvas de calibração. A distribuição qui-quadrado é utilizada na determinação dos limites das curvas de desvio em função de tempo para diversos tipos de termopares em cada temperatura específica. O modelo exponencial é escolhido para a função de distribuição de confiabilidade. Os parâmetros de desvio são determinados a partir de um procedimento que tem por base a análise de dados experimentais. Resultados de aplicação prática da metodologia proposta são apresentados para o cálculo das curvas de confiabilidade de termopares do tipo T e J. São apresentadas sugestões sobre a extensão de uso e aperfeiçoamento das técnicas desenvolvidas / Abstract: The purpose of the present work is to develop techniques and suitable criteria to be used in the prediction of calibration curve deviations and reliability of thermocouple measurements. The chi-squared distribuition is used to determine the limits of time deviation curves of different thermocouple types, at specific temperatures. The exponential model is chosen to represent the reliability distribution function. Deviation parameters are determined from a procedure based on experimental data analysis. Results of the practical application of the proposed methodology are shown for the determination of reliability curves of thermocouples of the type T and J. Improvement of the techniques as well as extention of their applications are suggested at the end of the work / Doutorado / Projetos Mecanicos / Doutor em Engenharia Mecânica

Thermocouples are generally used as devices to determine the internal temperature of any material. The purpose of the temperature measuring device is to measure the temperature which would exist at some known location if the device were not present. The thermocouples are embedded in the material in order to study the temperature-time history of the point of location. The presence of the thermocouple induces error in the temperature measured. This error becomes significant if heat is conducted into or away from the point of measurement by the sensor itself, or if the sensor insulates the point. This would result from much larger thermal conductivity of the thermocouple assembly than the surrounding material. This error in the temperature measurement will be called "conduction error."

This project was conducted in an effort to develop an inexpensive and reliable means of acquiring spatially and temporally resolved temperature data in turbulent reacting flows. Such a system would allow for increased understanding of turbulent reacting flows without the need for a costly and complex optical system. The system under study uses the responses of two thermocouples of different sizes placed in close proximity in order to determine instantaneous temperatures. This is in contrast to previous work in which compensation is performed on a single thermocouple junction in order to correct for the error caused by its heat capacity. The compensation technique that was developed did not require knowledge of the physical properties of the flow or the physical properties of the thermocouples. It did require the measured junction temperatures, the temperature gradients, and the ratio of the time constants of each thermocouple, which is related to the ratio of the diameters of the two junctions. Computer models were used to demonstrate the compensation technique itself and were used to show how this method is affected by such factors as diameter ratio, noise, size of the junctions, and the digital resolution of the voltage-to-temperature conversion. Dual junction probes were constructed and tested in non-reactive and reactive environments. Non-reactive experiments were used to calibrate the probe diameter ratio and compensation of thermocouples that were heated with a laser and then cooled appeared successful, with errors of 5% or less in the corrected temperatures. Data was taken in the exhaust duct of a step combustor and the compensated temperatures from this turbulent, combusting environment appeared realistic. Some non-physical temperatures were produced which resulted in the elimination of around 37% of the total data set. Non-physical temperatures were inconclusively attributed to a combination of spatial separation of the thermocouples, conduction losses, and to poor response of the junctions due to their size and heat capacity. Best results were obtained when the thermocouples were exposed to a non-reacting jet of heated air. In this situation, the response amplitude of the thermocouples was relatively large and the response frequency relatively low in comparison to the reacting experiments. In this case, the corrected temperature curve appeared to be physically realistic and properly in phase with the thermocouple signals. Around 10% of the data was discarded using error elimination techniques. It was decided that a workable system which was limited by the size and spatial separation of the thermocouples had been achieved. / Master of Science

This graduation thesis addresses questions to thermal profile measurement of PBGA package during solder reflow process. The first part of thesis deals with problem of reflow process and reliability factors of solder joint connection. Next part analyses operation principles of thermocouples that are commonly used for temperature measurement. The experimental part deals with methods of thermocouples fixation during tests and measurements of dummy PBGA package. There was realized a method of dummy PBGA thermal profiles measurement and sample testing with and without simulated thermal load on PBGA package. The end of thesis concerns on possibilities of thermal profiles evaluation by using PWI method and thermal profile optimization of reflow process.

Ce travail présente des résultats expérimentaux obtenus dans une cavité différentiellement chauffée de 4 m de hauteur. Dans cette étude, des cartographies de température (microthermocouples) et de vitesse (LDV 2D et PIV standard) ont été établies pour des écoulements de convection naturelle turbulente à grands nombres de Rayleigh (4,0×1010 ≤ RaH ≤ 1,2×1011) tout en respectant l'approximation de Boussinesq. L'exploitation des résultats expérimentaux a, entre autre, permis de caractériser la stratification thermique au centre de la cavité ainsi que son évolution en fonction du nombre de Rayleigh pour différentes émissivités des parois passives. En outre, cette caractérisation a permis de connaitre les répartitions des flux échangés à la paroi, la typologie des écoulements au voisinage des parois actives et dans le plan vertical médian, ainsi que le cheminement du fluide dans la partie haute de la cavité. Ces résultats sont ensuite comparés à ceux obtenus dans d'autres cavités différentiellement chauffées de moindres dimensions étudiées antérieurement au laboratoire. L'ensemble de ces résultats montre une grande cohérence et nous permet de déterminer des lois d'évolution de la vitesse maximale atteinte dans la cavité et du transfert de chaleur aux parois en fonction du nombre de Rayleigh en régime laminaire et turbulent. En parallèle, une étude numérique 2D a été réalisée. Son objectif est d'étudier l'influence du rayonnement de surface ou volumique sur la structure de l'écoulement et sur les modes de transfert de chaleur. A cette fin, un module de transferts radiatifs a été implanté dans un code Volumes Finis de convection naturelle turbulente existant. La modélisation de la turbulence est réalisée par une approche LES avec un modèle de diffusivité de sous maille adapté à la convection naturelle. La partie rayonnement est traitée à l'aide d'un modèle de gaz gris par bande, associé à une méthode aux ordonnées discrètes. Une analyse de l'influence du rayonnement de parois et/ou de gaz sur les écoulements turbulents de convection naturelle est réalisée pour un nombre de Rayleigh de 1,21011.

The Purpose of this thesis is to experimentally demonstrate an inversion analysis technique, developed by Dr. Jay Frankel (UTK), that utilizes transient temperature data from probes embedded at known locations in a material. This allows one to determine thermal properties (thermal diffusivity and thermal conductivity) of the material, surface temperature, and the surface heat flux as they change with time. Dr. Frankel’s inversion method can be used to determine surface temperature and heat flux of a one-dimensional semi-infinite slab based on the transient data from one or two embedded probes, if the thermal conductivity and thermal diffusivity of the material are known. Frankel’s theory suggests that the thermal properties of the material can be determined if transient data from two thermocouple (TC) probes at known locations and the heat flux at the surface are known. This thesis investigates finding the thermal properties and surface temperature of materials using a two embedded thermocouple approach. As an initial check to the inversion analysis, the theoretical temperature solution for a one-dimensional semi-infinite slab was used. This validated that the analysis could converge to the constant thermal properties for the theoretical material. An experiment was run again to provide data for the materials copper and aluminum. Using a real material is fundamentally different from using theoretical determined (analytical) data, because the thermal properties for a real material vary with temperature. Since the inversion analysis converged to a constant solution for the theoretical temperatures, it was believed that the real material will converge to a solution. However, it was seen that the thermal diffusivity for the real materials never converged to the expected value. Although, when a constant handbook value for the thermal diffusivity is used to calculate the thermal conductivities from the experimental temperature data collected from the internal probes, the inversion analysis resulted in good agreement with experiment.

The Purpose of this thesis is to experimentally demonstrate an inversion analysis technique, developed by Dr. Jay Frankel (UTK), that utilizes transient temperature data from probes embedded at known locations in a material. This allows one to determine thermal properties (thermal diffusivity and thermal conductivity) of the material, surface temperature, and the surface heat flux as they change with time. Dr. Frankel’s inversion method can be used to determine surface temperature and heat flux of a one-dimensional semi-infinite slab based on the transient data from one or two embedded probes, if the thermal conductivity and thermal diffusivity of the material are known. Frankel’s theory suggests that the thermal properties of the material can be determined if transient data from two thermocouple (TC) probes at known locations and the heat flux at the surface are known. This thesis investigates finding the thermal properties and surface temperature of materials using a two embedded thermocouple approach. As an initial check to the inversion analysis, the theoretical temperature solution for a one-dimensional semi-infinite slab was used. This validated that the analysis could converge to the constant thermal properties for the theoretical material. An experiment was run again to provide data for the materials copper and aluminum. Using a real material is fundamentally different from using theoretical determined (analytical) data, because the thermal properties for a real material vary with temperature. Since the inversion analysis converged to a constant solution for the theoretical temperatures, it was believed that the real material will converge to a solution. However, it was seen that the thermal diffusivity for the real materials never converged to the expected value. Although, when a constant handbook value for the thermal diffusivity is used to calculate the thermal conductivities from the experimental temperature data collected from the internal probes, the inversion analysis resulted in good agreement with experiment.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 109-111).

The thermocouple systems used for the measurement of surface temperature in high temperature applications such as advanced aerospace propulsion systems and diesel engine systems are expected to perform in rapidly fluctuating and extremely high heat fluxes corresponding to high temperatures (in excess of 1400 K) and high speed flows. Traditionally, Pt/Pt-Rh based thin film thermocouples have been used for surface temperature measurements. However, recent studies indicated several problems associated with these thermocouples at temperatures exceeding 1000 K, some of which include poor adhesion to the substrate, rhodium oxidation and reaction with the substrate at high temperatures. Therefore, there is an impending demand for thermoelectric materials that can withstand severe environments in terms of temperature and heat fluxes. In this study, thin films of titanium carbide and tantalum carbide as well as two families of conducting perovskite oxides viz., cobaltites and manganates (La(1-x)SrxCoO3, M(1-x)Cax MnO3 where, M=La,Y) were investigated for high temperature thin film thermocouple applications as alternate candidate materials. Thin films of the carbides were deposited by r.f. sputtering while the oxide thin films were deposited using pulsed laser ablation. Sapphire (1102) was used as substrate for all the thin film depositions. All the thin films were characterized for high temperature stability in terms of phase, microstructure and chemical composition using x-ray diffraction, atomic force microscopy and electron spectroscopy for chemical analysis respectively. Electrical conductivity and seebeck coefficients were measured in-situ using a custom made device. It was observed that TiC/TaC thin film thermocouples were stable up to 1373 K in vacuum and yield high and fairly stable thermocouple output. The conducting oxides were tested in air and were found to be stable up to at least 1273 K. The manganates were stable up to 1373 K. It was observed that all the oxides studied crystallize in a single phase perovskite structure. This phase is stable up to annealing temperatures of 1373 K. The predominant electrical conduction mechanism was found to be small polaron hopping. Stable and fairly high electrical conductivities as well as seebeck coefficients accompanied with phase, structure, composition and microstructure stability indicate that these materials hold excellent promise for high temperature thin film thermocouple applications. / Master of Science