Добірка наукової літератури з теми "Aluminum heat pipe"

With the rapid development of oil and gas industry, as well as geological exploration industry, the requirements on properties of aluminum alloy drill pipes are increasing. During heat assembly of aluminum alloy drill pipes, the cooling process inside the pipes has a direct impact on the connection performance of pipes. Thus, study of the convective heat transfer coefficient between the cooling water and the internal wall of aluminum alloy pipes is important. Conventional algorithms cannot easily solve the problem of determining the heat transfer coefficient at the complex structure of aluminum alloy drill pipes. Therefore, this article conducts a heat assembly experiment between aluminum alloy drill pipes and steel joints to obtain adequate, accurate temperature data. Based on these experimental data and an inverse heat conduction model, the heat transfer coefficients during the heat assembly process are determined by a finite element program and the differential evolution algorithm. The correlation curve between the cooling water flowrate and the convective heat transfer coefficient obtained in this article is important in the accurate prediction of heat transfer capacity and temperature field distribution during heat assembly at different cooling water flowrates. The analysis results show that the heat transfer coefficients are nonlinear functions of cooling water flowrates. The temperature is highest at location A1 and gradually declines backward along the axis of the drill pipe. The heat transfer coefficient gradually declines backward along the axis of the drill pipe. The increasing flowrate of cooling water will cause the convective heat transfer coefficient along the axis of the drill pipe to escalate irregularly.

Collector pipe used in solar power plant is a device for converting water from ambient temperature to the raised temperature which in turn used to rotate turbine blades. The raise in temperature is not that much when compared to thermal or nuclear power plant, so researches are going on for improving the heat carrying capacity of collector pipes. The productivity in pipe directly depends on the factors such as solar radiation incident on it, temperature distribution over the pipe, surrounding temperature, material of the pipeline used, and thickness of the pipe. When comparing to all of such parameters, the temperature distribution over the pipe is the main parameter which determines the performance of the collector pipe. For a particular type of solar collector pipe, the temperature distribution is function of length with day variation of solar incidence over it. In this work a collector pipe of length 2.2 m and 7 cm diameter is fabricated and tested under standard laboratory conditions for the uniform heat dissemination over the pipe. For keeping up the uniform temperature over the collector pipe, it is necessary to wound the pipe with metals like copper, aluminum. The results show that the heat distribution over the pipe is increased in case of copper when compared with aluminium.

The air flow rate available for cooling of notebook computers is very limited. Thus, notebook computer manufacturers desire a “passive” cooling method. Heat pipes are typically used to transport the heat from the CPU to a forced convection, air-cooled condenser. This paper describes a passive, keyboard sized aluminum Integrated Plate Heat Pipe (IP-HP) that has been developed for notebook computers. Analysis was performed to estimate the several thermal resistances in the heat pipe, including the effect of the vapor pressure drop. The modified design using a heat spreader at the evaporator significantly reduces the heat pipe resistance. Further work was done to evaluate the thermal contact resistance at the IP-HP/CPU interface. Test results show that the IP-HP can reject 18 W while maintaining the CPU 65°C above ambient temperature.

Ring-seam joint pipe is more and more widely used in advanced auto-body assembly. However, Aluminums higher conductivity, higher convection coefficient, oxidability and low plasticity in high temperature compared to convectional low carbon steel make its welding numerical simulation much more difficult. Thermal simulation is the fundamental of aluminums coupled calculations of thermo-elasto-plastic for welding. In this paper, a pipe joint of ring seam for ZL114 aluminum alloy is numerically modeled based on birth-death element method and moving-heat-source function loading method. The simulation results agree well with the experiments, which shows that the double ellipsoid heat source model is most suitable for MIG welding simulation of aluminum alloy.

The waste heat generated by high power LEDs 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 the experiment for the high efficiency of heat removal. The aluminum-acetone flat plate heat pipe is innovative proposed by our team. The high power LEDs with and without heat pipe cooling module is compared. The heat removal efficiency of the cooling module of the aluminum-acetone flat plate heat pipe reaches 77% and drops the junction temperature of LED about 36 °C. 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.

A combined experimental and analytical investigation was conducted to evaluate a heat pipe convective cooling device consisting of sixteen small copper/water heat pipes mounted vertically in a 4 × 4 array which was 25.4 mm square. The analytical portion of the investigation focused on determination of the maximum heat transport capacity and the resistance of the individual heat pipes. The resistance of each heat pipe was found to be 2.51 K/Watt, or more than 3 times smaller than the resistance produced by a solid copper rod with the same dimensions. The maximum predicted heat rejection for the module was over 50 Watts, or a power density in excess of 7.75 Watts/cm2. In the experimental portion of the investigation, two different modules were tested. The first module utilized ten circular aluminum fins mounted on the condenser end of each heat pipe to enhance heat rejection, while the second contained only the sixteen copper/water heat pipes. The effects of flow velocity, input power, and base plate temperature on the overall thermal resistance and the heat rejection capacity were determined, as well as the pressure drop resulting from each module. The finned heat pipe array was found to have a lower overall thermal resistance and thus, a higher heat rejection capacity, but also resulted in a significantly larger pressure drop than the array without fins. The results of the heat pipe array experiments were also compared with experimental and empirical results obtained from flow over a flat plate 25.4 mm square.

In this study, the dirt adhered on the tubes of different materials (copper alloy tube, stainless steel pipe, polyethylene-aluminum composite pipe) were studied by the scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, PCR amplification, DGGE electrophoresis analyzers. Experimental results show that the microorganism in dirt on the copper alloy tube is mainly shuttle-type bacteria, and the distribution is dense. Stainless steel pipe’s dirt colony is assembling with long bacilli and cocci, polyethylene-aluminum composite pipe’s dirt is the large bacilli and density cocci. Three kinds of dirt in the pipe contains inorganic crystals with SiO2 and CaCO3, and the same type of element, but the content is differences, polyethylene-aluminum composite pipe have greater richness of microbial species, a copper alloy tube’s dirt is of little microorganisms.

A novel flat heat pipe is put forward. The novel flat heat pipe is characteristic of its integral wick structure of microgrooves, which is made of a series of thin aluminum foils folded side by side. The thermal performance of the novel flat heat pipe under the different heat loads and incline angles has been investigated experimentally. It is found that the equivalent thermal conductivity of the novel flat heat pipe can be 12.3 times higher than that of the heat pipe material. Moreover, the novel flat heat pipe with integral micro-grooved wick has good temperature uniformity. The novel flat heat pipe can play a pronounced role in heat transfer enhancement, and be expected to be good candidates for thermal management of electronic devices.

This study mainly focuses on the influence of anodic aluminum oxide (AAO) nanostructure generated on condenser section inner surface on the heat transfer performance of gravity heat pipes. AAO nanotubes were first grown by anodizing the inner wall surface of the condenser section of aluminum alloy gravity heat pipes through different anodizing voltages and treatment times. The nanostructure effect on the temperature distribution and overall thermal resistance was then investigated by using a thermal performance test system under different input heat powers. The experimental results showed that the generation of AAO nanostructure on the inner surface significantly enhances heat transfer performance; that is, the temperature difference between the evaporator and condenser sections and overall thermal resistance are reduced. Such an effect can be more significant in the case of a lower heat source. The percentage decreases in temperature difference and overall thermal resistance can be reduced by up to 58.83% and 58.79%, respectively, compared to the unprocessed heat pipe.

In this paper, 15% SiCp/2009A1 composites were subjected to multi-pass hot spinning experiments. The principle of the microstructure and properties of the materials was studied with the increase of thinning rate. The microstructures, interfaces, precipitates and their properties of the tube, which were in the states of spinning, spinning and solution heat treatment were analyzed and discussed.The research shows that it is possible to prepare spinning pipe with good shape and smooth surface by taking use of the spinning process of this paper. During the power spinning process, the force of the rotary wheel to the pipe causes the billet to produce two-way deformation, and the axial and tangential grains are obviously elongated and the flow line is formed.There are mainly Al, SiC, CuAl2and Mg2Si phases in the tube, and the spinning deformation does not change the phase composition of the composites, but the SiC distribution can be more uniform and the oxide film on the surface of the aluminum particles is broken, as a result that the oxygen element will cluster at the interface.The solution heat treatment after spinning can greatly improve the yield strength and tensile strength of SiC/Al composites with a slight decrease in plasticity. The spinning process used in this paper can not only form a composite pipe with a smaller diameter and thinner wall thickness, but it can still be applied when the diameter of the pipe blank becomes larger and the wall thickness becomes thicker.Through the research on spinning process and microstructure, the feasibility of spinning process for preparing aluminum matrix composites pipes was explored, which provided technical and theoretical support for the preparation and processing of Particulate reinforced aluminum matrix composites (PRAMCs) pipes for aviation and aerospace applications.

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.

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.

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.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.14.06 «Технічна теплофізика та промислова теплоенергетика». – Національний технічний університет України «Київський політехнічний інститут імені Ігоря Сікорського», Міністерство освіти і науки України, Київ, 2018. Робота присвячена підвищенню енергетичної ефективності та спрощенню інтеграції сонячних систем на основі комбінованих сонячних колекторів у фасади і дахи будівель за рахунок використання як елемента теплопоглинальної поверхні алюмінієвих канавчатих теплових труб. Встановлено, що на ефективність роботи комбінованого сонячного колектора з алюмінієвими канавчатими тепловими трубами у режимі термосифона істотно впливають теплотехнічні характеристики теплових труб, які своєю чергою залежать від таких параметрів: діаметр парового простору, теплофізичні властивості робочої рідини, довжини зон нагріву і конденсації, а також загальна довжина алюмінієвих канавчатих теплових труб. Підвищення теплопередавальної здатності алюмінієвих канавчатих теплових труб можна досягти завдяки забезпеченню подачі гарантованої кількості теплоносія в зону нагріву та вибору оптимальних конструктивних параметрів теплових труб при відповідних режимах роботи. Аналіз розрахунків та експериментальних даних показав, що комбінований сонячний колектор з алюмінієвими канавчатими тепловими трубами дає змогу підвищити ефективність отримання електричної енергії до 18 % за рахунок охолодження фотоелектричних перетворювачів, при цьому максимальна електрична потужність комбінованого сонячного колектора становила 135 Вт/м2. Крім електроенергії, одночасно можна отримати до 457 Вт тепла з 1 м2 теплопоглинальної поверхні за температури вихідного теплоносія 25 ºС і густини сонячного потоку 900 Вт/м2. На основі теоретичного аналізу виявлено найбільш оптимальні режими експлуатації комбінованого сонячного колектора – режим функціонування за значень 30–50 ºС температурного перепаду між теплопоглинальною поверхнею та навколишнім середовищем. Нова конструкція комбінованого сонячного колектора має більш ефективну роботу порівняно з роздільними тепловими сонячними колекторами та фотоелектричними батареями за низьких температур на теплопоглинальній поверхні (нижче 50 ºС) і зазвичай за більш високих значень сонячного потоку (більше 600 Вт/м2).
Thesis for the Candidate degree in Technical Science on the specialty 05.14.06 «Technical thermophysics and industrial thermal power engineering». – National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute", Ministry of Education and Science of Ukraine, Kyiv, 2018. The work is devoted to increasing energy efficiency and simplification of integration of solar systems on the basis of the photovoltaic thermal (PV/T) collector in the facades and roofs of buildings due to use as an element of the absorbing surface of aluminum grooved heat pipes (AGHP). It is established that the efficiency of the operation of the PV/T collector with AGHP in the thermosyphon mode is significantly influenced by the thermal characteristics of the HP, which in turn depends on the following parameters: the diameter of the steam space, the thermophysical properties of the working fluid, the lengths of the heating and condensation zones, and the total length of the AGHP. Increasing the thermal conductivity of AGHP can be achieved by providing a guaranteed amount of coolant to the heating zone and selecting the optimal design parameters of the HP at the appropriate operating modes. A new approach to the implementation of PVT collectors on the basis of AGHPs is proposed. In this case, AGHPs perform a complex role – at the same time it is a highly efficient thermal conductor and a system of cooling solar cells. The design of an aluminum heat pipe with a grooved capillary structure for PVT collectors has been developed. An n-pentane is chosen as the optimum coolant for a two-phase system. The developed samples of heat pipes can provide the operation of the PVT collector in the thermal mode from 0 oC to 120 oC. In this case, the temperature range of its operation is from −40 °C to +230 °C. The analysis of calculations and experimental data showed that the PV/T collector with AGHP allows to increase the efficiency of obtaining electric energy up to 18 % due to the cooling of the PV, while the maximum electric power PV/T collector was 135 W/m2. In addition to electricity, simultaneously, it is possible to get up to 457 W of heat from 1 m2 of heat-absorbing surface, at a temperature of the output coolant 25 oС and a density of solar flux of 900 W/m2. On the basis of theoretical analysis, the most optimal modes of operation of the PV/T collector were identified – the most optimal one is the mode of PV/T collector functioning at values of 30–50 oC of the temperature difference between the absorbent surface and the environment. The new PV/T collector design has a more efficient performance compared to separate thermal solar collectors and photoelectric batteries at low temperatures on an absorbent surface (below 50 oC), and usually at higher solar flux values (over 600 W/m2). The first developed programs and methods of research of PVT collectors in artificial and natural light developed an engineering methodology for calculating the thermal characteristics of PVT collector with AGHPs during their operation in a thermosyphon mode. The recommendations for the production of PVT collectors and their use in solar power systems are given. The results of the work in the future can be used at the enterprises of LLC «Effectprof» (Kyiv), PC Sumy SPO M.V. Frunze (Sumy), PE Scientific-Implementation Firm "Thermal Technologies" (Kiev), which are engaged in the development, manufacture and implementation of heat-exchange equipment and energy-efficient systems. For further implementation, it is necessary to carry out works on designing and manufacturing an industrial design of PVT collector or facade PVT collector and to conduct tests in the field.
Диссертация на соискание ученой степени кандидата технических наук по специальности 05.14.06 «Техническая теплофизика и промышленная теплоэнергетика». – Национальный технический университет Украины «Киевский политехнический институт имени Игоря Сикорского», Министерство образования и науки Украины, Киев, 2018. Работа посвящена повышению энергетической эффективности и упрощению интеграции солнечных систем на основе комбинированных солнечных коллекторов в фасады и крыши зданий за счет использования в качестве элемента теплопоглощающей поверхности алюминиевых канавчатых тепловых труб. Установлено, что на эффективность работы комбинированного солнечного коллектора с алюминиевыми канавчатыми тепловыми трубами в режиме термосифона существенно влияют теплотехнические характеристики тепловых труб, в свою очередь зависят от следующих параметров: диаметр парового пространства, теплофизические свойства рабочей жидкости, длины зон нагрева и конденсации, а также общая длина алюминиевых канавчатых тепловых труб. Повышение теплопередающих способности алюминиевых канавчатых тепловых труб можно достичь благодаря обеспечению подачи гарантированного количества теплоносителя в зону нагрева и выбора оптимальных конструктивных параметров тепловых труб при соответствующих режимах работы. Анализ расчетов и экспериментальных данных показал, что комбинированный солнечный коллектор с алюминиевыми канавчатыми тепловыми трубами позволяет повысить эффективность получения электрической энергии до 18% за счет охлаждения фотоэлектрических преобразователей, при этом максимальная электрическая мощность комбинированного солнечного коллектора составляла 135 Вт/м2. Кроме электроэнергии, одновременно можно получить до 457 Вт тепла с 1 м2 теплопоглощающей поверхности при температуре исходного теплоносителя 25 °С и плотности солнечного потока 900 Вт/м2. На основе теоретического анализа выявлены наиболее оптимальные режимы эксплуатации комбинированного солнечного коллектора – режим функционирования при значениях 30–50 °С температурного перепада между теплопоглощающей поверхностью и окружающей средой. Новая конструкция комбинированного солнечного коллектора имеет более эффективную работу по сравнению с раздельными тепловыми солнечными коллекторами и фотоэлектрическими батареями при низких температурах на теплопоглощающей поверхности (ниже 50 °С) и обычно при более высоких значениях солнечного потока (более 600 Вт/м2).

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.

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.

Heat transfer characteristics of an aluminum plate pulsating heat pipe (PHPs) were investigated experimentally. Sizes, consisting of parallel and square channels as well as different cross-sections and different number of turns were considered. Acetone was used as working fluid. The characterization had been done for various heating mode orientations, cooling conditions, and internal structures via flow visualization and thermal performance tests. The flow visualization showed that the aluminum plate PHPs can maintain the heat transfer characteristics of the liquid and the vapor slug as well as the conventional tubular PHPs. The trend of flow pattern changed from the intermittent oscillation to unidirectional circulation. It was also observed that the PHPs’ thermal performance improved as heating power increased. The gravity greatly influenced the thermal performance of plate PHPs. Increasing the cooling temperature decreased the thermal resistance of the plate PHPs. Increasing the number of turns and the area of channel cross-section improved the heat transport capability of plate PHPs for some specific scenarios. A heat sink with a plate PHP was developed for comparing with the pure metal and conventional heat pipe solutions. The result showed that the plate PHPs solution performed well, and had the potential to replace previous solutions in some cases.

An investigation of the effect of using aluminum and titanium as the case material in a flat heat pipe (FHP) configuration is presented. In the heat pipe analyzed, the working fluid and the wick material were water and nickel foam, respectively. Identical configurations, dimensions, boundary and initial conditions were assumed in the numerical analysis for the two case materials. The flat heat pipe was subjected to a non-uniform heat input in the evaporator for a short period of time, and the condenser was cooled by natural convection and radiation effects. In both cases, non-uniform temperature distributions with peak values at the center of the evaporator side were observed. The titanium heat pipe gave a comparatively higher temperature range. The low thermal conductivity of titanium was understood to be responsible for the elevated temperature at the evaporator side. Consequently, it was also verified that for a low temperature range of operation and a short period of transient heat input, the aluminum heat pipe presented a better performance than the one with titanium as the case material. Discussions of the selection of the working fluids for the heat pipes based on the dimensionless merit number and other quantitative and qualitative parameters are also presented.

Aluminum heat pipes have traditionally been incompatible with water and water-based fluids because they quickly react with the casing to generate non-condensable hydrogen gas (NCG). The NCGs inhibit the operation of evaporation and condensation based devices, eventually plugging the condenser end of the heat pipe. The heat pipe is then unable to remove heat from the condenser and the device fails. Terdtoon [1] found that these events often happen so rapidly between aluminum and water that measurements cannot even be taken. The present work tested two different, patented inorganic aqueous solutions (IAS) in a flat heat pipe setup. Grooved aluminum plates were used as the heat pipe wick and the tests were run with the heating section raised above the condenser. Compatibility between the working fluid and aluminum heat pipe was established by running the device to dryout and then reducing the heat flux to check for hysteresis. De-ionized water (DI water) was also tested, as a baseline, to establish that it did indeed fail as expected. Operating performance of each mixture was obtained from zero heat input until dryout was reached for multiple angles of inclination. The data show that both IAS mixtures are compatible with aluminum heat pipes and exhibit performance similar to that of a copper and water heat pipe. IAS and aluminum heat pipes could replace existing copper and water devices and deliver similar performance while reducing overall weight by more than three times. An IAS and aluminum heat pipe could also replace existing aluminum and ammonia combinations, currently favored in aerospace applications, to allow for increased performance and a larger operating temperature range while maintaining low device weight.

Heat pipes are widely used heat transfer devices in the electronic cooling area. In this paper, a novel pulsating heat pipe (PHP) design, which combines features of PHP and capillary microstructures, is presented to enhance heat transfer of electronic printed circuit boards (PCB). Test prototype fabrication is initiated by making dual-radius serpentine channels on a 4.0mm thick aluminum plate, followed by compressing 4.67mm diameter copper tube into the grooves, and completed by generating a millimeter sized liquid channel with micro-grooves in the PHP along the longitudinal direction. Because of this design, the planar PHP is able to circulate operating liquid by both capillary pump and oscillation motions, which eliminate the dry state in the evaporator section and supply sufficient coolant at high heat loads. Demonstrations of heat transfer performance indicate that the planar PHP has high effective thermal conductivity and low evaporator temperature fluctuations, and oscillation continuity is the key factor to reduce the temperature difference between the evaporator and condenser.

Two-phase loops are extremely efficient devices for passively transporting heat over long distances with low temperature drop. The heat acquisition component of a two-phase loop, the evaporator, is commonly made from conventional metal materials (aluminum, copper, etc.) and has cylindrical geometry. Neither characteristic is optimally suited for close integration to common electronic or photonic heat sources, which generally have flat interfaces and are constructed from low thermal expansion coefficient (CTE) semiconductor materials. This paper describes the development of a ceramic flat plate evaporator for cooling processor chips in network computers used onboard Navy submarines. The unique requirements of submarines give added motivation for the advantages offered by two-phase loops. The ceramic flat plate evaporator is constructed of low CTE, high thermal conductivity material and thus enables a low thermal resistance interface between the heat source and the working fluid of the loop heat pipe. Alumina and aluminum nitride flat plate evaporators were integrated into a water-based two-phase loop and thermally tested to a heat flux of 30 W/cm2.

The ongoing development of faster and smaller electronic components has led to a need for new technologies to effectively dissipate waste thermal energy. The pulsating heat pipe (PHP) shows potential to meet this need, due to its high heat flux capacity, simplicity, and low cost. A 20-turn flat plate PHP was integrated into an aluminum flat plate heat sink with a simulated electronic load. The PHP heat sink used water as the working fluid and had 20 parallel channels with dimensions 2 mm × 2 mm × 119 mm. Experiments were run under various operating conditions, and thermal resistance of the PHP was calculated. The performance enhancement provided by the PHP was assessed by comparing the thermal resistance of the heat sink with no working fluid to that of it charged with water. Uncharged, the PHP was found to have a resistance of 1.97 K/W. Charged to a fill ratio of approximately 75% and oriented vertically, the PHP achieved a resistance of .49 K/W and .53 K/W when the condenser temperature was set to 20°C and 30°C, respectively. When the PHP was tilted to 45° above horizontal the PHP had a resistance of .76 K/W and .59 K/W when the condenser was set 20°C and 30°C, respectively. The PHP greatly improves the heat transfer properties of the heat sink compared to the aluminum plate alone. Additional considerations regarding flat plate PHP design are also presented.

The heat dissipated by convection from the fins of the heat pipe condenser section is strongly limited by the thermal barrier of the oxide layer formed on their aluminum surface. A lot of work has been done to enhance the heat transfer coefficient of this heat pipe section by changing the fins roughness. The present experimental study demonstrates the enhancement in heat transfer coefficient by applying a more conductive coating on the condenser fins surface. A comparison between a conventional technique consisting of applying a rougher surface and this new technique is performed. Results clearly show the performance of the heat pipe exhibits a better enhancement in the case of a more conductive coating than a rougher one. The orientation of the heat pipe is also investigated to demonstrate the effect of gravity on the enhancement so observed. Hydrodynamics inside the heat pipe is considered to explain the findings.

Abstract A flexible micro heat pipe radiator, fabricated by sintering an array of aluminum wires between two thin aluminum sheets, was developed as part of a program to conceptulize, develop, and test lightweight, flexible radiator fin structures for use on long-term spacecraft missions. A detailed experimental investigation was conducted to determine the temperature distribution, maximum heat transport capacity, and radiation efficiency of these micro heat pipe radiators in a radiation environment. Experimental results from three Aluminum-Acetone micro heat pipe radiators with wire diameters of 0.635 mm, 0.813 and 1.016 mm are presented, evaluated and discussed. The results of the experimental program indicted that the maximum heat transport capacity and radiation efficiency, both increased with increasing wire diameter. The maximum heat transport capacity of the micro heat pipe radiator utilizing a wire diameter of 0.635 mm was 15.2 W. The radiators utilizing wire diameters of 0.813 mm and 1.016 mm never reached the maximum heat transport capacities for the given test conditions. In the tests, temperature distributions were recorded for several sink temperatures and indicated that as the sink temperature decreased the radiation efficiency decreased for a given heat input. The maximum heat transport capacity increased with increasing evaporating temperature for the micro heat pipe radiator utilizing a wire diameter of 0.635 mm. Comparison of micro heat pipe radiators with and without working fluid, indicated that significant improvements in temperature uniformity and radiation efficiencies could be obtained, especially at high heat fluxes. A maximum radiation efficiency of 0.95 was observed. In general, while some variation in performance was observed, all three micro heat pipe radiators were found to be capable of meeting the thermal requirements of long-term missions.