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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Experiment study for heat transfer of high density electronic multichip array by transient heat transfer method with with thermochromic liquid crystal

Lee, Hsu-Fu 10 July 2002 (has links)
Abstract This investigate is designated to the viewpoint that arrangement array of multichip modules are both staggered and in-line. Moreover, here we will discuss and compare the effects and differences of the relevantparameters caused by change Reynolds number (Re) in the experiment.In this experiment, I adopt ¡§transient heat transfer method with thermochromic liquid crystal¡¨ to research multichip modules array change to 3 ¡Ñ 5 and in-line or staggered multichip modules array to probe into the effects of over high density electronic multichip array space to length ratio to heat transfer effects when over high density electronic multichip array space to length ratio are S/L= 4/20,6/20,8/20 in the 8mm¡B12m¡B16mm respectively. The conditions are as following when every row center of chip convection heat transfer coefficient are measured: standard height to length ratio is H/L=10/20 and the height is 20mm. By observing the relationship of the varying parameters, as we can see in the analyze multichip of the experiment Re range form 1394 to 5025, we are able to improve thermal management. The experimentresule: (1) At higher values of Re the heat transfer effects are gain more,atteribute main flow field separation and reattachment is form behind the downstream modules. (2) In over high density multichip array 12S (S/L=6/20) proper are use for Re higher 4135 more than, at 8S (S/L=4/20)the lower Re can be thermocumulate in chip center. (3)When Re is 4135~5025,the heat transfer effects from staggered array is superior to in-line array. If Re range is 1394~3210,the thermal conduction is opposite. Therefore, Re is still the key that decides the efficacy of over high density electronic multichip array heat transfer effects.
2

Estudo da conveniÃncia da identificaÃÃo do fator de atrito e da rugosidade em redes de distribuiÃÃo de Ãgua atravÃs do mÃtodo transiente inverso com algoritmo genÃtico / Study of the friction factor identification of convenience and roughness in water distribution networks through the reverse transient method with genetic algorithm

Gabriela Celso Melo Pinheiro de Vasconcelos 10 November 2014 (has links)
A Ãgua à um recurso natural essencial para todas as formas de vida e a sua distribuiÃÃo deve ser realizada com qualidade e sem desperdÃcios. Um dos mÃtodos de otimizaÃÃo dos sistemas de distribuiÃÃo de Ãgua à baseado na simulaÃÃo (modelagem) de redes hidrÃulicas reais atravÃs de modelos computacionais capazes de prever o seu comportamento nas situaÃÃes diversas ao logo da sua vida Ãtil. As principais etapas desse mÃtodo sÃo calibraÃÃo; operaÃÃo e controle; projeto e otimizaÃÃo; e traÃado de redes. A ideia deste trabalho à aprimorar uma dessas tÃcnicas, a de calibraÃÃo, processo de identificaÃÃo dos parÃmetros das tubulaÃÃes (fator de atrito, rugosidade, diÃmetros e outros) em redes existentes, na qual os mesmos sÃo considerados desconhecidos. A metodologia adotada à o MÃtodo Transiente Inverso (MTI) com otimizaÃÃo da tÃcnica de seleÃÃo da soluÃÃo atravÃs do algoritmo GenÃtico (AG). O objetivo principal à calibrar os principais parÃmetros (fator de atrito e rugosidade) a fim de analisar a conveniÃncia de duas tÃcnicas: cÃlculo do fator de atrito pelo mÃtodo pelo MTI-AG e a partir da rugosidade (com uso da fÃrmula de Swamee, 1993). O estudo à realizado para duas redes sintÃticas tiradas da literatura, mas que representam sistemas reais. As condiÃÃes impostas para a anÃlise sÃo: duas manobras de vÃlvulas (lenta e brusca) responsÃveis pelo evento transiente, o monitoramento de cargas transientes em somente 20% dos nÃs das redes e a utilizaÃÃo de dois tipo de seleÃÃo de soluÃÃo do algoritmo genÃtico (com elitismo e sem elitismo). Os experimentos sÃo realizados a partir de trÃs programas: o primeiro calcula as condiÃÃes permanentes, o segundo fornece cargas transientes por meio do MÃtodo das CaracterÃsticas (MOC) na busca das soluÃÃes das equaÃÃes de movimento no escoamento transiente e o terceiro, que trabalha de forma conjugada com os demais, seleciona os melhores resultados atravÃs de iteraÃÃes realizadas conforme o algoritmo genÃtico, tÃcnica inspirada nos mecanismos de evoluÃÃo dos seres vivos. Os resultados encontrados indicam que independente das condiÃÃes impostas inicialmente à mais eficiente identificar o fator de atrito a partir das rugosidades absolutas do que calibrar esse fator pelo MTI-AG devido a grande variabilidade dos fatores de atrito durante a ocorrÃncia do evento transiente. / Water is an essential natural resource for all life forms and their distribution should be carried out with quality and without waste. One of the methods of optimization of water distribution systems is based on the simulation (modeling) of real hydraulic networks using computational models that can predict their behavior in various situations the logo of its useful life. The main steps of this method are calibration; operation and control; design and optimization; and route networks. The idea of ​​this work is to improve one such technique, the calibration parameters of the pipes identification process (friction factor, surface roughness, diameter and the like) existing in networks in which they are considered unknown. The methodology adopted is the Transient Inverse Method (MTI) with optimization of the solution selection technique by Genetic Algorithm (GA). The main objective is to calibrate the main parameters (friction and roughness factor) to analyze the convenience of two techniques: calculation of the friction factor by the method by MTI-AG and from the roughness (using the formula Swamee, 1993 ). The study is carried out for two taken synthetic networks of literature, but represent real systems. The conditions for the analysis are: two maneuvers valves (slow and abrupt) responsible for the transient event, the monitoring of transient loads in only 20% of the nodes of the networks and the use of two types of solution selection of genetic algorithm (with elitism and without elitism). The experiments are carried out through three programs: the first calculates the permanent conditions, the second provides transient loads through the method of characteristics (MOC) in the search for solutions of the equations of motion in the transient flow and the third, who works so combined with others, selects the best results through iterations performed according to the genetic algorithm, a technique inspired by the mechanisms of evolution of living beings. The results indicate that regardless of the conditions imposed is initially more efficiently identify the friction factor from the absolute roughness than calibrate this factor by MTI-AG due to the great variability of friction factors for the occurrence of the transient event.
3

Studium tepelných vlastností materiálů / Study of Thermal Properties of Materials

Štefková, Pavla January 2012 (has links)
The doctoral thesis deals with study of thermal properties of materials. Behavior of homogeneous matters at different temperatures is well described in theory and experimentally verified. Overall effect of all components of mixture and other influences related with material creation affect behaviour and properties of heterogeneous matters. For study of thermal properties can be used transient method of measurement which provide a picture about overall influence of all components of mixture on studied heterogeneous material and among others enable determination of thermophysical properties of whole macroscopic system in observed temperature range. Properties of solid matters, thin foil and liquids can be measured by means of pulse and step-wise transient method which is used for experimental activity in the thesis. It is contact measurement method and its principle is based on small quantity of heat generating inside the specimen and temperature response measuring. Theoretical part of thesis is focused on creation of method for determination of thermophysical parameters. The base is differential equation of the heat conduction. Its solution is temperature function. Three methods of evaluation are described mathematically. They start from general relations designed for study of fractal structure physical properties (maximum of function method, differential method and multi-parametric non-linear regression method).
4

In-Pile Thermal Conductivity Measurement Methods for Nuclear Fuels

Fox, Brandon S. 01 May 2010 (has links)
Measuring nuclear fuel thermal conductivity in-pile can provide much needed data for understanding fuel performance during irradiation and yield thermophysical property data needed for simulation codes and fuel databases. The objective of this research is to develop and compare two in-pile thermal conductivity methods in a laboratory setting using surrogate fuel materials. A steady-state radial heat flow method was investigated to understand its viability as an in-pile steady-state thermal conductivity technique. By using Joule heating to simulate volumetric heat generation within a surrogate fuel rod, thermal conductivity was measured with two thermocouples at different radial positions within the rod. Examinations were completed on two batches of surrogate materials over the temperature range of 500 to 700 °C. The selected surrogate rod was fabricated from the only material identified to possess the required thermal conductivity and electrical resistivity required for the selected laboratory approach. Evaluations estimated a measurement uncertainty of 12% and values were within 33% of values obtained using laboratory material property measurement systems for this surrogate material. Results indicate that the selected surrogate rod material limited the ability to assess this approach at higher temperatures in a laboratory setting. A transient needle probe method adapted from American Standard Test Method standards was also used to measure temperature-dependent thermal conductivity of surrogate fuel rod materials for temperatures ranging from room temperature to 400 °C. The needle probe has a heating element and a temperature sensor contained in a metal sheath, and it is inserted into the surrogate fuel rod whose thermal conductivity is to be measured. The thermal conductivity is calculated from the power applied to the heating element, and the temperature rise detected in the sample. Needle probes were designed and fabricated using materials recommended for in-pile application. Scoping room-temperature values obtained using the needle probe method were within acceptable accuracies defined by the ASTM needle probe reference standard. Temperature-dependent values were within 2% of values for the well-characterized ASTM recommended reference material, fused silica. A measurement uncertainty under 6% was calculated for the needle probe method. As a result of this study, the needle probe method was selected for additional testing at the Idaho National Laboratory for anticipated testing in Materials Test Reactors. This would result in the first-ever transient in-pile thermal conductivity sensor.
5

Studium pasivní stabilizace teploty kompozitních stavebních materiálů / Study of passive stabilisation of building materials temperature

Šebek, Jan January 2010 (has links)
The topic of presented master’s thesis was study of passive stabilization of building materials temperature. The main goal of this thesis was measuring and characterization of the thermal properties of building materials, which are used to PCM technology. PCM technology is based on utilization of latent heat of phase change. At the beginning of this thesis it was needed to define physical principle of phase change, then the most usable PCM chemicals (e.g. paraffin, Glauber’s salt, hexahydrate calcium chloride) and their basic physical properties (especially thermo-physical), background research of building materials with PCM and also the methods of thermo-physical properties measurement. It was also needed to characterize measured building materials and define theirs thermal parameters; because the values of thermal parameters of measured samples were compared to these values. In the experimental part of my thesis are measurements of material thermal analysis, which are methods, where the properties of materials are studied as they change with temperature. I had used to differential scanning calorimetry, transient pulse method and other methods, which are usable for thermo-physical properties measuring and characterization. I have been much interested in properties of measured material, which were specific heat capacity, temperature diffusivity, heat conductivity and phase change temperature (the melting point of PCM). At the end of my thesis the findings of all methods were finally summarized, compared and commented.
6

Mesure de propriétés monophasiques de milieux poreux peu perméables par voie instationnaire / Transient methods to determine one-phase flow properties of poorly permeable porous media

Profice, Sandra 07 March 2014 (has links)
Parmi la multitude des données pétrophysiques utilisées pour décrire une formationgéologique, certaines permettent spécifiquement d'en prédire la capacité de production,à savoir : la porosité, la perméabilité intrinsèque et le coefficient de Klinkenberg.Dans le cas particulier des gas shales, ces trois propriétés essentielles sont extrêmementdifficiles à mesurer précisément, compte tenu de la complexité de cesroches. Cette thèse s'inscrit dans la continuité de travaux menés au laboratoire I2M départementTREFLE, sur l'analyse et l'amélioration de la méthode Pulse Decay, quiconstitue la méthode de mesure transitoire classiquement utilisée dans l'industriepétrolière pour identifier une ou plusieurs des propriétés d'intérêt. Les multiplespoints faibles de la méthode Pulse Decay sont ici présentés, de même que les pointsforts de la nouvelle méthode issue du perfectionnement de la méthode Pulse Decay,à savoir la méthode Step Decay, développée au laboratoire I2M et brevetée en partenariatavec TOTAL. Plus précisément, les performances de la méthode Step Decaysont ici étudiée aussi bien numériquement qu'expérimentalement, en condition homogène,comme en condition hétérogène. Ce manuscrit fournit également les résultatsd'une analyse portant sur la méthode Pulse Decay sur broyat, qui forme une alternativepossible à la méthode Pulse Decay sur carotte mais dont la fiabilité est fortementremise en question. / Among the multitude of petrophysical data used to describe a geological formation,some of them allow specifically to predict the production capacity, namely: the porosity,the intrinsic permeability and the Klinkenberg coefficient. In the particular case ofgas shales, these three essential properties are extremely difficult to measure precisely,because of the complexicity of these rocks. This thesis is the continuity ofworks led in I2M laboratory-TREFLE department, on the analysis and the improvementof the Pulse Decay method, which is the classical transient method of measurementused in the oil&gas industry to identify one or several of the properties ofinterest. The numerous weaknesses of the Pulse Decay method are here presented,as the strengths of the new method derived from the improvement of the Pulse Decaymethod, namely the Step Decay method, developed in I2M laboratory and patentedin partnership with TOTAL. More exactly, the performances of the Step Decaymethod are here studied numerically as well as experimentally, in homogeneouscondition, as in heterogeneous condition. This manuscript provides also the results ofan analysis dealing with the Pulse Decay method on cuttings, which forms a possiblealternative to the Pulse Decay method on plug but which reliability is highly questioned.

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