Dissertations / Theses on the topic 'Aluminum Pipe'

A new application of heat pipes is introduced. The present research deals with the development of a heat pipe for the on-line quality control of liquid aluminum silicon foundry alloys.
Thermal analysis is a technique whereby a small quantity of a melt is allowed to solidify while its cooling curve is recorded. Analysis of the cooling curve with standard mathematical algorithms allows one to determine a number of useful parameters that characterize the liquid and solid states of the material. In aluminum-silicon casting alloys thermal analysis is often used to assess the grain size and degree of eutectic modification of the alloy before pouring.
A novel probe has been developed for conducting thermal analysis of aluminum alloy melts. The probe, which resides in the melt, need not be withdrawn as it solidifies a small sample (i.e. button) at a predetermined cooling rate. Once the cooling curve results have been acquired, the probe can be instructed to remelt the frozen button and await instructions for analyzing a fresh sample.
The operating principle of this novel device is based on heat pipe technology. In simple terms, a heat pipe consists of a condenser and an evaporator which contain a relatively small quantity of working substance fluid. As heat is absorbed by the evaporator, the liquid phase of the working substance is vaporized and subsequently condensed on the condenser walls from which heat is extracted.
It has been shown that the designed probe, which is classified as a gas loaded annular thermosyphon, is completely workable in the range of conditions typically encountered in the thermal analysis of aluminum alloys. The thermal analysis results obtained with this new technique are in a good agreement with those of conventional thermal analysis. In addition, the new method is applicable to a wider range of operating conditions and is easier to use. Based on the semi-continuous nature of the new method, it does not need pre-preparation (materials, labour, pre-heating, thermocouple installation for each test, isolation of the sampling cup, etc.) to start thermal analysis. Also, from a cooling rate point of view, the system is well controllable. Moreover, it is shown that the probe is simple in construction, easy to use, and intelligent enough to provide semi-continuous thermal analysis. There are no consumable materials and moving parts.
Thermal analysis results are reported for pure aluminum, hypoeutectic aluminum silicon (356) and eutectic aluminum silicon (413) casting alloys. Agreement in the results between the new and conventional systems is shown to be excellent. Finally, a heat transfer/solidification model of the heat pipe thermal analysis probe is derived and validated.

Previous research by Rushing et al. (2002) identified key factors contributing to the formation of pinhole leaks in copper plumbing. These factors included high chlorine, pH levels and the presence of aluminum solids. Experiments were conducted to 1) examine the interplay between these constituents, 2) confirm that the water was aggressive enough to eat a hole through a pipe, 3) examine phosphate inhibition, and 4) try to determine the scope of this pitting problem in other distribution systems and on a national level.

The first set of experiments clearly defined the controversial trends from earlier work. At certain pH values, the presence of chlorine and aluminum solids does seem to initiate pitting corrosion of copper. Although the problem is most severe at higher pH, it is likely that long-term exposure at lower values such as pH 8 could lead to pitting. There is a concentration effect of aluminum solids at pH 9.0, in that higher concentrations cause an earlier rise in the potential for copper to corrode if sufficient chlorine is present.

The second phase of experiments are the first to prove that a potable water containing aluminum, high chlorine residual, and relatively high pH can cause pinholes in copper tube. To our knowledge this is the first time the phenomenon of pinhole leaks has been reproduced in the laboratory as it occurs in the field. It therefore proves that "aggressive water" alone can cause the problem of pitting. The role of flow, pipe orientation and hypothesized surface defects was directly examined as part of this evaluation. Pitting increased with greater water usage and for sections of straight pipe exposed to hydraulic conditions near bends. Copper pipe sections polished to a mirror like finish to remove surface defects were also severely attacked.

The role of phosphate in mitigation of copper pitting corrosion was defined in a subsequent experiment using synthesized water. Phosphates did not have an effect at pH 7.7 and were found to reduce electrochemical indications of pitting in the synthetic water at the pH of 8.3. Phosphates had lesser benefits at higher pH even in synthetic water, but overall, even at pHs as high as 10, some benefits from orthophosphate dosing might be anticipated.

Effects of orthophosphate on the inhibition of copper pitting corrosion were then applied to treated water from a utility in Washington D.C., whose consumers have experienced an outbreak of pinhole leaks in household copper plumbing. After comparing electrochemical results from synthetic and actual water from the treatment plant, there was evidence of a natural inhibitor to pitting corrosion in WSSC water that is not present in the synthetic water. The higher chloride concentration in the water after ferric chloride was dosed at the treatment plant may have reduced the pitting propensity of the water. The effects of phosphates seemed to reduce the pitting propensity of real water at pH 8.3 although little benefit was seen at pH 9.1.

These defined characteristics of copper pitting were then applied in a systematic evaluation of a water utility experiencing pitting corrosion in Roanoke, VA. This case study further supported the hypothesis that high levels of aluminum, chlorine, and pH may be combining to catalyze copper pitting in practice. Recommendations to alter the treatment strategies at these utilities were proposed to help mitigate the pitting corrosion problems in these areas. A national survey then confirmed pitting is occurring at a significant frequency at other large utilities across the U.S.

Master of Science

Thesis (MEng) -- Stellenbosch University, 2014.
ENGLISH ABSTRACT: Solar energy is a time dependent, high-temperature radiant energy resource. The utility of a solar thermal energy system increases if the hot temperature source is available when it is needed most. This is realized by the thermal storage of the solar energy. Thermal storage gives greater versatility to a solar energy system by decoupling the heat source from the heat sink. A large quantity of energy may be stored during the melting process in a phase change material (PCM) within a small temperature range. This molten PCM can then deliver its absorbed heat at a constant temperature in a heating application. In this study a phase change storage system (PCS) is developed and proposed for a solar water heating application. This PCS system stores more heat per unit mass than would be possible with water across the same temperature range. The heat transfer rate in and out of many PCMs is slow because of the low thermal conductivity of the PCM. However, heat transfer enhancers (HTE), such as heat pipes and fins may be added to enhance heat absorption and heat removal rates. Heat pipes have the inherent capability to transfer heat at high rates across large distances, even where the temperature difference is small. In this thesis a description is given of a PCS system consisting of paraffin wax as the PCM and which uses rectangular heat pipes in conjunction with aluminium fins to enhance heat transfer. The storage design is modular and each module has the characteristic that enhanced heat transfer in and out of the PCM is possible when the module is heated or cooled. It also has the capability to quickly absorb or alternatively to supply heat at a nearly constant temperature during the phase change of the module. A rectangular module was designed and built. The module was then analysed under controlled heat absorption and heat removal cycles. The heat up experiment involved an electrical kettle as the hot temperature source. The heat sink was a mains water heat exchanger. The experimental results were compared to those of a transient numerical model, which calculates theoretically how the module will perform thermally under the given test conditions. The numerical model of the experimental set-up was validated when it was found that the numerical model results resemble the experimental results. The numerical model was then adapted to simulate a novel solar water heater (SWH) with an additional PCS container. The improvement over previous designs is that the additional storage container can be heated to a higher temperature than the allowable geyser temperature. The system also heats up and cools down at a faster rate than would be possible without the HTEs. From the numerical simulation the size and performance of such a system is determined. This numerical analysis indicated that a phase change storage system in a SWH application will increase the hot water delivered by a given solar collector and geyser by increasing the storage capacity and by heating up the geyser overnight for early morning hot water use.
AFRIKKANSE OPSOMMING: Son energie is ‘n tyd afhanklike, hoë temperatuur radiasie energiebron. Die bruikbaarheid van ‘n sontermiese energie sisteem verhoog indien die hoë temperatuur bron beskikbaar is wanneer dit die meeste benodig word. Dit kan verwesenlik word deur die sonenergie termies te stoor. Termiese storing bied groter veelsydigheid aan ‘n sontermiese stelsel deur effektief die hittebron te ontkoppel van die hitte sink. ‘n Groot hoeveelheid energie kan, gedurende die smeltingsproses in ‘n faseveranderingsmateriaal binne ‘n nou temperatuurband gestoor word. Hierdie gesmelte materiaal kan weer op sy beurt in die waterverhittingstoepassing, die geabsorbeerde hitte teen ‘n konstante temperatuur oordra. In hierdie studie word ‘n sonwaterverwarmer stelsel wat aangepas is deur ‘n addisionele latente hittestoor daaraan te heg, voorgestel. Hierdie faseverandering hittestoor kan meer hitte stoor as wat water in dieselfde temperatuur band sou kon. Die hitteoordrag tempo na en van baie van die faseveranderingsmateriale (FVM) is egter as gevolg van die lae termiese geleidingskoëfisient, stadig. Hierdie eienskap kan gelukkig verbeter word deur hittepype en hitteoordrag verhogings materiaal soos vinne by te voeg. Hittepype het die inherente eienskap om hitte teen ‘n hoë tempo oor groot afstande, oor te dra, selfs oor ‘n klein temperatuurverskil. In hierdie tesis word ‘n ondersoek rakende ‘n faseverandering storingsisteem wat bestaan uit paraffien was as die FVM en reghoekige hittepype wat te same met met aluminium finne gebruik word om die hitteoordragtempo te verhoog, beskryf. Die stoorontwerp is modulêr en elke module het die kenmerk van hoë hitteoordrag na en van die FVM. Die module het verder ook die eienskap om vining hitte te absorbeer of hitte af te gee. Dit gebeur teen ‘n konstante temperatuur gedurende die faseverandering van die FVM. Presies so ‘n reghoekige module is ontwerp en gebou en onder beheerde hitte absorbering- en hitte verwyderingsiklusse analiseer. Tydens die verhittings eksperiment is ‘n elektriese ketel van gebruik gemaak wat gedien het as die hoë temperatuur bron. Die hitte sink was ‘n hitteruiler wat kraanwater van ‘n konstante hoogte tenk ontvang het. Die resultate van die volledige toets is met die resultate van tydafhanklike numeriese model vergelyk. Hierdie numeriese model bereken teoreties wat die module se storing verrigting onder gegewe toets omstandighede sal wees. Die numeriese model se resultate het goed vergelyk met die resultate van die eksperimente. Die numeriese model van die module is toe aangepas om ‘n sonwaterverwarmer met addisionele stoortenk wat fase verandering materiaal gebruik, te simuleer. Hierdie ontwerp is anders as vorige ontwerpe in die sin dat hoër temperature as wat die warmwatertoestel kan hanteer, in die faseverandering storingstenk, bereik kan word. Die sisteem kan ook as gevolg van die hitteoordrag verhoging materiaal, vinniger verhit of afkoel en teen ‘n vinniger tempo. Die simulasie van die sonwaterverwarmer met FVM word gebruik om die grootte en verrigting van die sisteem te bepaal. Hierdie numeriese model toon aan dat wanneer ‘n addisionele faseverandering storingstelsel in ‘n sonwaterverwarmer toepassing gebruik word, die warm water wat die verbruiker uit die sisteem kan verkry, kan verhoog. Die rede hiervoor is dat meer hitte gestoor kan word, wat beskikbaar gemaak word aan die warm water tenk.

Ce travail avait pour objectif la réalisation d'une pile de puissance de technologie aluminium-air. Cette technologie résulte de l'association d'une anode en aluminium et d'une cathode à réduction de l'oxygène de l'air. L'électrolyte employé est un électrolyte alcalin très concentré. Après une étude bibliographique consacrée à ces systèmes, les divers éléments de la pile ont été choisis ; une première formulation d'électrolyte permettant de limiter la corrosion de l'anode sans affecter les performances de la pile a été déterminée. Une pile de test de format réduit appelé cellule Pi nous a permis d'étudier l'influence de différents additifs et de déterminer la formulation optimale de l'électrolyte par plan d'expérience. La pile est alors constituée d'une anode en aluminium de pureté dépassant 99,99 %. L'électrolyte aqueux contient 4 mol/L de potasse et 0,075 mol/L de stannates de potassium. Les stannates sont les inhibiteurs de la corrosion de l'aluminium en milieu alcalin concentré les plus efficaces mais leur mode d'action n'est pas connu. Afin de préciser ce mode d'action nous avons dans un premier temps étudié le comportement de l'aluminium dans les électrolytes alcalins concentrés par différentes techniques telles que l'émission acoustique et l'électrode à disque et à anneau tournant. La technique d'émission acoustique a ensuite été brièvement appliquée à l'étude du mode d'action des stannates. Une dernière partie concerne l'étude d'un phénomène oscillatoire original apparu lors d'une décharge de pile à basse température
Aluminum-air batteries result from the association of an aluminum anode and an air cathode. Ln the present study, we had to elaborate a primary battery of great power density from such technology. We used a concentrated alkaline electrolyte to reach the power requirements. After a bibliographic survey concerning aluminum-air batteries, we determined a tirst electrolyte formulation so as to inhibit as much as possible the aluminum corrosion, without performance loss. Using a small-size test cell, we studied the influence of various additives to reach an optimal electrolyte composition from the design of experiments methodology. Our aluminum-air battery is thus composed of an aluminum anode of purity beyond 99. 99 %. The aqueous electrolyte contains 4 M potassium hydroxide and 0. 075 M potassium stannates. The stannates consist of the best aluminum corrosion inhibitors in strong alkaline medium, but their mode of action remains fuzzy. We attempted to give more insight into the inhibition mechanisms studying the behavior of aluminum in concentrated potassium hydroxide, using the acoustic emission and the rotating ring-disk electrode techniques. The former technique has then been used to evaluate the stannates mode of action. The last part of the manuscript concerns the study of oscillations which appear when the aluminum-air baUery is discharged at low temperature

A novel heat pipe (HP) manufacturing method has been developed based on an additive layer manufacturing technique called “selective laser melting” or SLM. This innovation is expected to benefit current applications of aluminium/ammonia heat pipes in space and terrestrial projects as well as many new HP applications. The project was jointly sponsored by the Northumbria University and Thermacore, a world leading heat pipe manufacturing company in the UK, and formed the feasibility stage of a much larger program in Thermacore aiming to develop the next generation of HPs for space applications. In this project, sinter-style aluminium SLM HPs have been produced and tested to prove their functionality and to provide an overall image of the new production process with regard to the major involved parameters. During the project several properties of the new heat pipes e.g. wick porosity, permeability and pore size; wall density, hardness, vibration resistance and optimum SLM build parameters have also been determined by the existing or especially developed rigs in Thermacore or Northumbria University laboratories including scanning electronic microscope (SEM), vibration table, permeability measurement rig, etc. Converting the SLM products into functional heat pipes involves many other steps which have also been completed and explained. At the end of the project two successful functional samples were obtained and clear and precise answers were found to the project questions. SLM process was proved to be capable of producing functional heat pipes. Functional sinter-style heat pipes are proved to be producible by SLM. A numerical design tool is now available to evaluate SLM produced heat pipes and major challenges of this new HP production process including the density of the solid structures and possible contamination of the materials have been identified. Also a reasonably good overall image of this new HP production process and the new HPs has been provided in this project through the conducted measurements and experiments. The contribution of this project to knowledge is supported by two papers published in prestigious heat pipe journals and one paper presented in the 16th international heat pipe conference.

Orientador: Eugênio José Zoqui
Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-16T10:27:34Z (GMT). No. of bitstreams: 1 Cicero_RenatodeSouza_M.pdf: 4231594 bytes, checksum: f0889ace44452237f6ef4aac57f6652d (MD5) Previous issue date: 2010
Resumo: As tubulações de alumínio de saída de água dos motores diesel estão apresentando cavitação, devido ao seu design. Atualmente a tubulação de alumínio de saída de água recebe a anodização dura, porém a liga Al - Si - 10 Mg não é favorável a anodização por ter o silício. O silício, por sua vez, dificulta a formação da camada de óxido e com isso a camada de anodização não será uniforme, principalmente na região interna da tubulação de água. A camada de anodização está sendo mal depositada devido ao processo ser manual e com isso as tubulações de água que apresentaram cavitação foram analisadas em microscópio eletrônico de varredura, a fim de caracterizar a espessura da camada anodizada. Observou-se comparativamente que a camada de anodização não é uniforme. A pintura KTL é um tratamento superficial que consiste em um processo de três etapas, sendo a primeira de um pré-tratamento: desengraxe, lavagem, decapagem e fosfatização. A segunda é a Pintura Eletroforética Catódica (KTL) e por último a terceira que é a cura acelerada em estufa com temperatura e tempo controlado. A pintura KTL foi realizada pela teoria da eletroquímica que se subdivide em quatro fenômenos: Eletrólise, Eletroforese, Eletrocoagulação e por fim a eletroosmose. Na análise realizada comparativamente a camada de KTL é uniforme em toda a extensão da tubulação de alumínio de saída de água dos motores Diesel. Com este resultado comparativo, a pintura KTL se faz necessária na tubulação de alumínio (Al - Si - 10 Mg) de saída de água dos motores Diesel para que se minimize o efeito da cavitação
Abstract: The pipes aluminum water outlet of the diesel engines is experiencing cavitation, due to its design. currently, aluminum pipe water outlet receives the hard anodized, but the Al - Si - Mg 10 is not favorable to have the anodizing because silicio. The silicio, in turn, hinders the formation of the oxide layer and thus the layer of anodizing is not uniform, especially in the inner water pipe. Water pipes that had cavitation were examined in a scanning electron microscope in order to characterize the thickness of the anodized layer. It was noted that the comparatively anodizing layer is not uniform. KTL painting is a surface treatment that consists of a three-step process, the first being a pre-treatment: degreasing, washing, pickling and phosphating. The second is the Cathodic Electrophoretic Painting (KTL) and finally the third which is accelerated healing in a greenhouse with controlled temperature and time. KTL painting was done by the theory of electrochemistry which is divided into four phenomena: Electrolysis, Electrophoresis, Electro coagulation and finally the electroosmosis. In the analysis performed compared to KTL layer is uniform throughout the length of aluminum pipe water outlet of diesel engines. With this result comparison, KTL painting is needed in the tubing of aluminum (Al - Si - 10 Mg) output of diesel engines for water to minimize the effect of cavitation
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Automobilistica

Orientador: Gustavo Habermann
Banca: Douglas Silva Domingues
Banca: Luciano Pereira
Resumo: O Alumínio (Al) é um dos elementos mais abundantes na crosta terrestre. Solos ácidos (pH < 5.0) compreendem cerca de 40% das terras agriculturáveis no mundo, e sob essas condições, o Al se encontra na forma de Al3+, que é tóxico para a maioria das plantas. Na presença de Al, observa-se uma redução nos parâmetros de trocas gasosas e de hidratação foliar, que podem estar diretamente relacionadas com a diminuição no transporte de água radicular. Aquaporinas são proteínas integrais da membrana plasmática que facilitam o transporte de água transmembranar e, nas raízes, estas podem contribuir com mais de 50% na condutividade hidráulica. Portanto, uma diminuição na abundância de aquaporinas poderia acarretar em um menor transporte de água até a folha. No presente estudo, cultivamos plantas de limoeiro 'Cravo' (Citrus limonia), durante 90 dias em solução nutritiva com Al. Em seis épocas, coletamos dados de trocas gasosas, potencial hídrico, conteúdo relativo de água na folha e verificamos a expressão de três genes de aquaporinas nas raízes: PIP1-1, PIP1-2 e PIP2. Confirmamos uma menor hidratação da folha pela redução do conteúdo relativo da água (CRA) e potencial hídrico (w), bem como diminuição na assimilação de CO2 (A), condutância estomática (gs), transpiração (E) e condutividade hidráulica estimada da raiz até a folha (KL) em plantas expostas ao Al. Além disso, plantas submetidas ao Al apresentam uma atenuação no perfil transcricional de PIP1-1 e PIP2 e um aumento na expressão d... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Aluminum (Al) is one of the most abundant elements of the Earth's crust. Acidic soils (pH <5.0) comprise about 40% of the world arable land, and under these conditions, Al is in the form of Al 3+, which is toxic to most plants. In the presence of Al, there are reduction in the gas exchange parameters and leaf hydration, which m ay be directly related to the decrease in root water transport. Aquaporins are integral prote ins of the plasma membrane that facilitate water transport and they can contribute to more tha n 50% of the root hydraulic conductivity by transmembrane pathway. Therefore, a decrease in aquaporin abundance in the roots may lead to lower water transport up to the leaf. In a 90-day study, we cultivated 'Rangpur' lime plants ( Citrus limonia ) in nutrient solution with Al. At six time points, we measured gas exchange, water potential ( Ψ w), relative water content (RWC) in the leaves and we also assessed the expression of three aquaporin genes in the roots, PIP1-1, PIP1-2 and PIP2 . We confirm lower leaf hydration by a reduction in RWC and Ψ w, as well as decreased CO 2 ( A ) assimilation, stomatal conductance ( gs ), transpiration ( E ), and estimated hydraulic conductivity from the root to the leaf ( K L ) in plants exposed to Al. In addition, plants submitted to Al presented an attenuation in the tra nscriptional profile of PIP1-1 and PIP2, and an increase in the expression of PIP1-2, of which only PIP1-1 presented a correlation with A and gs in the Al tr... (Complete abstract click electronic access below)
Mestre

Actuellement, le développement à grande échelle des piles à combustible à membrane échangeuse de protons est limité par l’utilisation importante de platine ainsi que par une faible durabilité des dispositifs. Les électrodes conventionnelles, dénommées Pt/C, sont constituées de nanoparticules de platine déposées sur un support composé de nanoparticules de carbone. Le but de cette thèse est de proposer, élaborer et tester en pile à combustible complète des nanostructures composées de nanotubes de platine autosupportés afin d’augmenter la durée de vie des dispositifs et de réduire la quantité de platine utilisée. Afin de réaliser de telles nanostructures, un moule d’alumine nanoporeuse constitué de nanopores verticaux est élaboré par oxydation électrochimique d’aluminium. Cette matrice de nanopores permet de réaliser une croissance confinée de nanotubes de platine par évaporation de métal sous vide ou par des dépôts électrochimiques. Une membrane de Nafion® est par la suite pressée à chaud et l’alumine est dissoute. Des nanotubes de platine autosupportés sont ainsi obtenus à la surface de la membrane. Afin de comprendre le fonctionnement de ces électrodes en pile à combustible complète, une méthode de quantification des pertes limitant les performances d’électrodes standards de Pt/C a été utilisée. La nanostructuration des électrodes permet d’augmenter significativement la durée de vie des dispositifs et de diminuer les pertes de transport d’oxygène. La principale limitation mise en évidence est des pertes cinétiques importantes en raison de la faible surface spécifique de platine développée
The two main drawbacks of Proton Exchange Membrane Fuel Cells (PEMFC) are the low electrode durability and the high platinum loading (electrocatalyst for oxygen reduction reaction). Currently, PEMFC electrodes, named as Pt/C, are made of platinum nanoparticles supported by carbon nanoparticles. The aim of this PhD work is to propose, elaborate and test in complete fuel cell new electrode nanostructure consists in self-supported platinum nanotubes. We target a reduction in the platinum loading and an increase in the electrode durability. In order to control nanostructure geometries, a porous alumina mold is used. This template is obtained by electrochemical anodization and vertically aligned nanopores are obtained. Platinum is subsequently deposited onto pore walls by e-beam evaporation or electrochemical deposition processes. After the hot pressing of the Nafion® proton exchange membrane, the porous alumina mold is etched and platinum nanotubes are stuck and self-supported onto the membrane. A part of this work is dedicated to the quantification of performances losses of Pt/C electrodes and nanostructured electrodes in complete fuel cell test operating conditions. Nanostructured electrodes exhibit high durability and easy oxygen access on catalyst surface compared to Pt/C electrodes. However, some losses kinetics remains due to the low catalyst specific area

La pile à combustible alimentée par de l'hydrogène issu de la bio-masse est un système prometteur pour remplacer le moteur de combustion interne à base des carburants fossiles. La production embarquée d'hydrogène par reformage de bioéthanol répond aux critères d'une source d'hydrogène renouvelable, d'un transport et stockage aisé pour un carburant comme le bioéthanol et d'une émission nette de CO2 négligeable. Le taux de CO dans le flux d'hydrogène qui alimente la PAC doit être <10ppm pour éviter l'empoisonnement du catalyseur en Pt sur l'anode. Des catalyseurs de type monolithe ont été développés et testés sous la condition de PROX en présence de CO2 et H2O entre 100 et 300ʿC. Le système Pt/alumine présente une bonne activité et sélectivité en présence de H2O par rapport aux systèmes CuCeO2. . Différentes voies réactionnelles sont proposées après une étude du mécanisme par spectroscopie infrarouge in situ (DRIFTS). Une étude cinétique est réalisée sur ce catalyseur. Le réacteur de purification (PROX) a été développé et dimensionné en parallèle puis intégrés dans une unité pilote de puissance 5kWe, dans le cadre d'un contrat européen sur reformage du bioéthanol

碩士
國立臺灣科技大學
機械工程系
102
In fulfilling consumer’s requirement on reducing size and weight of mobile devices, especially the notebook, tablet, and cell phone, has generated a urgent demand for manufacturing the light-weight Aluminum heat pipe. Thus, the purpose of this study is to design and manufacture the Al heat pipe that uses pure water as the working medium. Obviously, the major advantages in utilizing Al heat pipe include the lighter weight and cheaper cost compared to the traditional copper heat pipe. However, there are several technical challenges, such as the welding, corrosion, and compatibility issues in using Al as the heat pipe container. Firstly, a thin copper layer is attached closely to the inside wall of Al pipe for preventing the direct contact with water; thus the corrosion and compatibility issues between water and Al can be solved. Also, the YAG laser welding technology is introduced for sealing two ends of Al heat pipe. Furthermore, the systematic procedures for manufacturing and testing this Al heat pipe are proposed and set up successfully. Later, the amount of working medium and the flattened thickness of heat pipe are investigated for identifying the optimum values to yield the highest maximum heat transfer rate. Consequently, it is found that the maximum heat transfer rate enlarges for an increasing working-medium amount under a normal flattened thickness. Nevertheless, a decrease on maximum heat transfer rate is observed for the case of filling too much water when the height of vapor channel inside the heat pipe is less than 0.9 mm. Besides, the results illustrate that heat dissipating capability (30 watts) of the optimized heat pipe is almost identical to that of the traditional copper heat pipe with a 2.2 mm flattened thickness. Therefore, it is suggest that determining the optimized amount of working medium should take into account the cross-sectional geometry of heat pipe. In summary, this study presents a reliable and systematic scheme to fabricating the Al heat pipe.

D.Ing. (Mechanical Engineering)
The local buckling of axially loaded thin walled circular aluminium tubes is investigated in this work. Various buckling modes can be identified depending on certain geometrical ratios. Tubes with a thickness to diameter ratio of between 0,016 and 0,1 will buckle according to the so called axi-symmetric mode which is a very efficient collapse mechanism for energy absorbing purposes. Although there are numerous analytical solutions for this collapse mode the results are not fully descriptive. A finite-element model was developed and is described in this work. With this model it is possible to analyse the collapse mechanism in detail and the results obtained compare favourably with experimental values. When a relatively long thin walled tube is loaded axially it will undergo Euler buckling. This is not an effective collapse mechanism for energy absorbing purposes and a concept that overcomes this disadvantage is presented. With this energy absorber it is possible for axially loaded longthin walled circular tubes to collapse into a mode that resembles the axi-symmetric collapse mode. A finite element model was developed and successfully used to analyse the proposed concept. The results obtained correlate well with experimental values. A low speed impact test rig was designed, manufactured and commissioned. This rig was used to conduct dynamic tests on the proposed energy absorber and it was concluded that the proposed concept is viable for applications that require an inexpensive, reliable energy absorber with a long strokelength.

碩士
國立高雄第一科技大學
機械與自動化工程所
98
In the new generation of technology products, the gradual rise of the world''s energy efficient technology, environmental protection and recycling trends. The light metal has become an industry application. The views of the general structure of materials, aluminum, magnesium and titanium is the most common light metal, and these three light metal is also widely used in automotive, aerospace and information products, such as 3C industries. In recent years, emerging materials of metal foam is the most developed structure, especially the most common foamed aluminum. But copper, nickel, steel and titanium foam metal is still the development of state. As the foamed aluminum for low melting point (about 750℃) Materials, welding is not easy to effectively. Therefore, this experiment will filled foamed aluminum tube on SS400 low carbon steel and increase its weld ability. As the same research SS400 carbon steel pipe welded with foamed aluminum mechanical properties. This study will attempt to use two different pairs of SS400 carbon steel pipe welded with foamed aluminum welding patterns within the study. First, the establishment of plasma welding and hybrid welding test, and examine the characteristics of these two differences in the quality of welding. Finally, the study employs Taguchi methods coupled with principal component analysis, fuzzy-based Taguchi-PCA to develop the multiple quality characteristics process optimization of pulsed plasma welding and pulsed CO2 laser-TIG arc hybrid welding of SS400 carbon steel pipe welded with foamed aluminum.

碩士
國立臺南大學
機電系統工程研究所
103
High power light emitting diode array is an important product to promote energy conservation and reduce carbon emissions. But as the LED power increases, the heat flux increases. However, increasing of in the heat flux will lead the LED package to be damaged, and causes the LED brightness reducing. The waste heat generated by high power LED is hardly effectively dissipated, therefore, it results in a serious problem in the luminous efficiency. The most important issue of the LED research is to find a potential design of heat removal and solve the problem of LED over-heating. The purpose of this study is to design the LEDs combined with the cooling module of the aluminum-acetone flat plate heat pipe by experiment for the high efficiency of heat removal. The high power LEDs with heat pipe cooling module, heat sink cooling module and without cooling module are compared. We find that the heat removal efficiency (80.93%) of the aluminum-acetone flat plate heat pipe cooling module is better than the one of heat sink module obviously. The cooling module of the aluminum-acetone flat plate heat pipe has proven to be effective in solving the heat concentration problems associated with the LED chips. In short, the phase change cooling module will apply on the electronic component of high heat concentration for more effective cooling method.

碩士
國立雲林科技大學
電機工程系
103
With the rapid technology development, in industry, it has become prevalent to use automated optical inspection to replace the time and labor consuming manual inspection. Generally, most pipe manufactures adopt visual (manual) inspection and its maximum recognition rate can only reach 70%. Besides, it results in the loss of companies’ cost and labor power in the long term; moreover, a deeper understanding of its full pipe processing process reveals that if the defect of visual inspection cannot be improved, the production efficiency and quality of the product will be disable to make further progress. In this thesis, to capture images, the experimental platform is desktop with image capture module, rotating mechanism, line-scan camera and coaxial light. This thesis aims to detect the defect of aluminum pipes by capturing the surface images via line-scan camera. The reason to use line-scan camera rather than area scan camera lies in its high shooting speed and feature of flattening the cylinder surface which is beneficial for image analysis. In the inspection process, the rotating mechanism rotates the aluminum pipes for the image capture module to catch images. After that, the image processing is implemented to remove complex background and display only defect images then to proceed image analysis via different ways. In this thesis, three different ways are applied and introduced: i. Defect detection by grayscale standard deviation ii. Defect detection by gray-level co-occurrence matrix then classify via support vector machines iii. Defect detection by edge detection via fuzzy theory The result shows that the three ways have each correspondent defect type. The share key point is whether the image capture processing can be unaffected to complex background and capture way and the handling methods is rather important as well. If the result can be unaffected, the defect recognition and finding rate can reach over than 95%.

碩士
臺灣大學
土木工程學研究所
98
To investigate the behavior of a laterally loaded pile, a series of model pile tests were conducted at the National Center for Research on Earthquake Engineering (NCREE). An aluminum model pile in a box without and with soils was tested. Tests with the pile only were performed to determine the pile’s flexural rigidity while tests with the pile in saturated sands were conducted to record the pile-head load-deflection responses and the curvatures along the pile shaft. To analyze the test data of this model test, the moment distributions of the pile were firstly computed by multiplying the curvatures with the flexural rigidity. Then, an optimization method with Lagrange multipliers was adopted to fit the moment curves to polynomials. Afterward, the displacement, slope and shear of the pile, as well as the soil reactions can be obtained through integration and differentiation of the moment function. Besides, the p-y curves can be thus constructed by relating the soil reactions to the displacements of the pile. To understand the characteristics of the experimental p-y curves obtained, the initial subgrade modulus and the secant subgrade reaction modulus of the p-y curves were investigated. Simple empirical equations were further proposed to simplify the experimental p-y curves. Finally, numerical analyses with the experimental p-y curves were performed by SAP2000 for verification and give satisfactory results.

碩士
國立勤益科技大學
資訊管理系
105
As the development of the society and the improvement of living standards, the oil prices continue to rise which makes people pay attention to the environmental protection, health and recreation. In addition, there are more and more people ride the bicycle and their requirements of bicycle are getting more advanced and lighter. To make the bicycle more advanced and lighter, it is necessary to use smaller number and diverse modes for scheduling. This study mainly aims at the stability of the quality of the aluminum alloy pipe fittings during the process of CNC machining. After discussing with the expert, we will use the quality function deployment method, and through the relationship matrix, indicating the problem and the strength of the solution. Then by using TRIZ / engineering parameter, contradictory matrix and forty principle of invention, we will find out the specific design scheme and processing parameters of the solving method of improving CNC process problem. Finally, we use the machining experiments and tests to find the best program and processing parameters to improve the aluminum pipe fittings CNC process quality.

碩士
國立臺灣師範大學
工業教育學系
99
In this study, a two-step synthesis with a water-soluble dispersant of chitosan was used to produce stable suspensions of Al2O3/water nanofluid as the working fluid of the heat pipe. The thermal conductivity and rheological properties of the alumina/water nanofluids were evaluated. The optimal amount of added dispersant for the Al2O3/water nanofluid was determined. This study presents a discussion of the effects on the thermal performance of the heat pipe of the charged amount of working fluid, the tilt angle and length of the heat pipe, the heating power of the evaporator section, and the weight fraction of nanoparticles. The experimental results show that the optimal concentration of dispersant was 0.2wt.% to follow-up heat pipe thermal performance experiments under the dispersion properties and thermal conductivity simultaneously were considered. In thermal performance experiments, the optimal thermal performance of the heat pipe occurs when the tile angle of the heat pipe and the charged amount of working fluid are 30∘and 20 %~40 %, respectively. The shorter heat pipe is suitable for use in low heating power, and the longer heat pipe is suitable for use in high heating power applications under the same cooling condition. The 30 cm heat pipe can enhance the thermal performance efficiency by 18.72 %~43.78 %, the 45 cm heat pipe by 13.13 %~50.72 %, and the 60 cm heat pipe by 7.44 %~17.67 % when compared with deionized water as the working fluid of the heat pipe. This study confirmed that the Al2O3/water nanofluid has superior heat transport performance in the heat pipe compared with deionized water, and has considerable potential for use in the development of high performance heat pipes.

碩士
中原大學
機械工程研究所
105
This thesis is conducted with the study on the heat transfer performance of gravity heat pipes with anodized aluminum oxide nano-surface. The main purpose is to experimentally investigate the influences of aluminum oxide nanotube length and diameter on the temperature distribution, thermal resistance, and dryout phenomenon of gravity heat pipes under different thermal powers input. First, the anodic oxidation method is used to generate anodic aluminum nanotubes on the inner wall-surface of the evaporation section of aluminum gravity heat pipes. Then, nano-surfaces with different nanotube lengths and diameters are obtained by controlling the anodic oxidation time and voltage. Further, the shape of those nanotubes are observed by using the FE-SEM. Finally, these gravity heat pipes are placed in a thermal test system so as to measure the temperature, calculate the thermal resistance, and record the dryout phenomenon. The results show that the increase in the anodic oxidation time could increase the length of an anodized aluminum nanotube under a particular thermal power input. Increasing the nanotube length reduces the temperature change between the evaporation section and condensation section and the thermal resistance; moreover, the dryout phenomenon is delayed. In addition, the increase in the anodic oxidation voltage could increase the nanotube diameter. Increasing the nanotube diameter also reduces the temperature change between the evaporation section and condensation section and the thermal resistance; however, the increase in diameter does not seem to affect the dryout phenomenon. In summary, if the anodic oxidation treatment is applied to the inner wall surface of the evaporation section of a gravity heat pipe, the heat transfer performance could be obviously improved. The heat transfer performance of the gravity heat pipe could further be enhanced by increasing the anodic oxidation time and voltage.