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Goodman, Christopher L. "Modeling, validation and design of integrated carbon dioxide heat pumps and water heaters." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22560.
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Athavale, Jayati Deepak. "Evaluation of Internal Fin Geometry for Heat Transfer Enhancement in Automobile Exhaust Energy Harvesting Systems." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/54017.
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Thermoelectric generators (TEGs) are currently being explored for their potential in harvesting energy from automobile exhaust. TEGs in form of an appropriate TEG- Heat exchanger module can utilize the temperature difference between the hot exhaust gases and the automobile coolant and convert it into electrical voltage. The amount of power is anticipated to be a few hundred watts depending on the temperature gradient and the material of the TEGs.
The focus of this study is increasing the hot side heat transfer for improved performance of the thermoelectric generators using two different internal fins — louvered fins and herringbone wavy fins. The multi-louvered fins basically have 'multi flat plate' behavior and will enhance the heat transfer by deflecting the air from its original path and aligning it with the plane of the louvers. Herringbone fins are used to lengthen the path of airflow allowing for greater residence time and better mixing of the flow. They also provide for greater wetted surface area achieving higher heat transfer. The flow and heat transfer behavior inside the exhaust pipe test section with internal fins is modeled using commercial numerical software.
The thermal and flow behavior through both these internal fins depends to a large extent on geometric parameters and fin arrangement. Optimization of the fin design is considered to determine the configuration that provides highest heat transfer while providing least pressure drop across the pipe length. The heat transfer and pressure drop characteristics are compared to the baseline flow without any fin enhancement.Master of Science
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Aliev, Ruslan. "CFD Investigation of Heat Exchangers with Circular and Elliptic Cross-Sectional Channels." Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1452678890.
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Tambovtsev, Alexander. "Energieeinsparung in Kälteanlagen durch Kombination von thermostatischem Expansionsventil und innerem Wärmeübertrager." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1218482331656-43301.
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Die Erfindung der Kältemaschine macht es möglich, dass heute zu beliebiger Zeit Kälte in benötigter Menge und gewünschter Temperatur erzeugt werden kann. Aber für die Kälteerzeugung braucht man Antriebsenergie. Das Ziel dieser Doktorarbeit besteht darin, mit einer intelligenten Kombination von thermostatischem Expansionsventil (TEV) und innerem Wärmeübertrager (IWÜ) den Energieverbrauch von Kälteanlagen deutlich zu verringern, ohne dass dies zu einer Verschlechterung der Zuverlässigkeit oder wesentlichen Mehrkosten führt. Bis heute gelten die beiden bekannten Komponenten TEV und IWÜ als inkompatibel miteinander, weil die einfache Aneinanderreihung zu einem instabilen Regelverhalten führt. Nach detaillierter Analyse der Ursachen dieser Instabilität wird die Hypothese aufgestellt, dass durch eine absichtliche „Verschlechterung“ des IWÜ ein stabiler Arbeitsbereich gefunden werden kann. Bei dieser „Verschlechterung“ kann es sich z. B. um den Bypass eines Teils des Hochdruckstromes oder um eine Gleichstromanordnung der Ströme im Wärmeübertrager handeln. Diese Hypothese wurde primär durch Experimente, aber zusätzlich auch durch Simulationsrechnungen bestätigt. Dafür wurde ein Versuchsstand aufgebaut, mit welchem verschiedene Konfigurationen und Regelstrategien getestet wurden. Es wurde eine deutliche Verringerung des Energieverbrauchs gegenüber herkömmlichen Anordnungen erreicht.
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Veselská, Monika. "Provoz a řízení sprchových rekuperačních výmeníků." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227293.
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This thesis deals with the operation and management of shower recuperative heat exchangers, energy recovery from them and further use of this energy. This work is divided into four parts. The first presents the possibilities of using energy from wastewater. The second part deals with the design possibilities of energy recovery from waste water in the building, design water and sewer . The third part is devoted to the specification of the shower regenerative heat exchanger, its operation, regulation and control, culminating in economic evaluation of the proposed exchanger. The last part is a technical report and annexes drawings of the project.
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Tambovtsev, Alexander. "Energieeinsparung in Kälteanlagen durch Kombination von thermostatischem Expansionsventil und innerem Wärmeübertrager." Doctoral thesis, Technische Universität Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A23656.
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Die Erfindung der Kältemaschine macht es möglich, dass heute zu beliebiger Zeit Kälte in benötigter Menge und gewünschter Temperatur erzeugt werden kann. Aber für die Kälteerzeugung braucht man Antriebsenergie. Das Ziel dieser Doktorarbeit besteht darin, mit einer intelligenten Kombination von thermostatischem Expansionsventil (TEV) und innerem Wärmeübertrager (IWÜ) den Energieverbrauch von Kälteanlagen deutlich zu verringern, ohne dass dies zu einer Verschlechterung der Zuverlässigkeit oder wesentlichen Mehrkosten führt. Bis heute gelten die beiden bekannten Komponenten TEV und IWÜ als inkompatibel miteinander, weil die einfache Aneinanderreihung zu einem instabilen Regelverhalten führt. Nach detaillierter Analyse der Ursachen dieser Instabilität wird die Hypothese aufgestellt, dass durch eine absichtliche „Verschlechterung“ des IWÜ ein stabiler Arbeitsbereich gefunden werden kann. Bei dieser „Verschlechterung“ kann es sich z. B. um den Bypass eines Teils des Hochdruckstromes oder um eine Gleichstromanordnung der Ströme im Wärmeübertrager handeln. Diese Hypothese wurde primär durch Experimente, aber zusätzlich auch durch Simulationsrechnungen bestätigt. Dafür wurde ein Versuchsstand aufgebaut, mit welchem verschiedene Konfigurationen und Regelstrategien getestet wurden. Es wurde eine deutliche Verringerung des Energieverbrauchs gegenüber herkömmlichen Anordnungen erreicht.
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Nattes, Pierre-Henri. "Optimisation d'un cycle au CO2 dans le domaine du transport frigorifique." Thesis, Paris, CNAM, 2018. http://www.theses.fr/2018CNAM1190.
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L’objectif de cette étude est d’optimiser un cycle frigorifique au CO2 pour une application dans le transport frigorifique. Les performances de l’unité doivent être supérieures à celles d’une machine avec une injection de vapeur et un compresseur bi-étagé déjà commercialisé. Suite à l’étude de plusieurs solutions, un éjecteur couplé à un échangeur interne semble la solution la plus intéressante.Un banc expérimental est créé à partir de l’unité possédant une injection de vapeur. L’éjecteur est muni d’une aiguille pour pouvoir assurer une recherche de la haute pression optimale. L’échangeur interne est équipé d’un by-pass pour modifier la puissance échangée. Un ensemble de points d’essais est testé avec deux températures d’évaporation : 0 °C et -20 °C, et trois températures de source chaude : 30 °C, 38 °C et 50 °C.L’éjecteur avec aiguille est capable de s’adapter à différentes températures extérieures en modifiant la haute pression. L’échangeur interne permet d’augmenter les performances du cycle mais présente une limite, la température au compresseur devient élevée et présente un risque de détérioration de ses performances ou de l’huile.Avec le cycle présentant un éjecteur, une amélioration du coefficient de performance est observée pour les points avec une température d’évaporation de 0 °C mais celle-ci chute drastiquement pour les températures d’évaporation de -20 °C. Une analyse exergétique du cycle confirme les faibles performances de celui-ci pour des températures d’évaporation négatives.À partir des résultats expérimentaux, des modèles numériques sont mis en place. Les échangeurs, vannes de détente sont modélisés de manière conventionnelle. Pour le compresseur, le modèle de Winandy est modifié afin de fonctionner pour un compresseur bi-étagé avec injection de vapeur. L’éjecteur est modélisé à travers un modèle unidimensionnel basé sur des transformations simplifiées décrites à travers des rendements isentropiques. Tous les modèles sont validés mais ceux des échangeurs ont un temps de calcul CPU trop important pour pouvoir être utilisés sur une modélisation dynamiqueThe aim of this study is to optimize a CO2 cooling cycle for transport application. The efficiency of the unit needs to be superior that of a cycle with vapor injection and a two stages compressor. The solution proposed is to install an ejector with an internal heat exchanger.A test bench is created from a pre-existing unit. Tests are made for two evaporation temperatures: 0 °C and -20 °C and three external temperatures: 30 °C, 38 °C and 50 °C. The ejector is equipped with a needle to seek the optimal high pressure. The internal exchanger is equipped with a by-pass to modify the thermal power exchanged.The ejector with needle can change the high pressure to seek the optimal conditions. The internal heat exchanger increases the efficiency of the cycle but the rising of temperature at the compressor can degrade its efficiencies or the oil. The new cycle increases the COP for evaporation temperature of 0 °C but the COP is lower than without ejector for evaporation temperature of -20 °C. An exergetic analysis shows that indeed the cycle is less efficient for low evaporation temperature.From the experimental results, numerical models are created to realize a system simulation and to test different scenarii to drive the unit. Exchangers and valves modeled with conventional tools. Wynandy’s model is adapted to be used on a two-stage compressor with vapor injection. The ejector is modeled with a one-dimensional model, based on simplified transformations described with isentropic efficiencies. All models seem to work but the CPU time is too high to use the exchanger models for dynamic simulation
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Buřič, Jan. "Vnitřní prostředí a výplně otvorů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-239950.
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The aim this diploma thesis is the design of heating and hot water in the building of a primary school in Trhové Sviny. The first part dealt with the issue of indoor environment and windows. The second part deals with a separate proposal heating and hot water in primary school. As a heat source was designed gas boiler, the second variant hot transfer station. The third part consists of technical reports and drawings of the specified object. The fourth part deals with the assessment of surface condensation on the surface of the window panes.
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Isafiade, Adeniyi Jide. "Interval based MINLP superstructure synthesis of heat and mass exchange networks." Doctoral thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/5315.
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Includes abstract.Includes bibliographical references (leaves 153-157).
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This study presents a new technique for synthesizing heat and mass exchange networks. The method involves generating superstructures using the temperature/composition interval concept from the physical insight approach. The superstructures are partitioned into temperature/composition intervals using the supply and target temperatures/compositions of either the hot/rich or cold/lean set of streams. The opposite kind of streams are made to participate (float) in all the intervals defined. Their ability to exchange heat/mass in these intervals is however subject to thermodynamic feasibility. The resulting superstructure is optimised as a mixed integer non linear programming (MINLP) model. The superstructure is hot/rich streams based if hot/rich streams are used to define the intervals otherwise it is cold/lean stream based.
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Nagavarapu, Ananda Krishna. "Binary fluid heat and mass exchange at the microscale in internal and external ammonia-water absorption." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45777.
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Absorption space-conditioning systems are environmentally benign alternatives to vapor compression systems and have the capability of being driven by waste heat. However, a lack of practically feasible and economically viable compact heat and mass exchangers is a major limitation in the success of this technology. The viability of the absorption cycle depends upon the performance of the absorber, which experiences large heat and mass transfer resistances due to adverse temperature and concentration gradients during the phase change of the binary mixture working fluid, resulting in large overall component sizes. Understanding of the coupled heat and mass transfer during binary fluid mixture absorption at the microscales is critical for the miniaturization of these components, which will enable broad implementation of this technology.
The proposed study aims to achieve this by investigating ammonia-water absorption for two distinct flow configurations: external falling films and internal convective flows. For the falling-film absorption case, ammonia-water solution flows around an array of small diameter coolant tubes while absorbing vapor. This absorber is installed in a test facility comprising all components of a single-effect absorption chiller to provide realistic operating conditions at the absorber. Local temperature, pressure, and flow measurements will be taken over a wide range of operating conditions and analyzed to develop a heat and mass transfer model for falling-film ammonia-water absorption. A microscale convective flow absorber will also be investigated. This absorber consists of an array of parallel, aligned alternating shims with integral microscale features, enclosed between cover plates. These microscale features facilitate flow of various fluid streams and the associated heat and mass transfer. The use of microchannels induces high heat and mass transfer rates without any active or passive surface enhancement. The microscale absorber for small-scale applications will be evaluated over a wide range of operating conditions on a single-effect absorption heat pump breadboard test facility. The study will conclude with a comparison of the two flow configurations for absorption, with recommendations for their application in future miniaturization efforts
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Sara, Hanna. "Analysis and valorization of new thermal management systems for a vehicle powertrain application." Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0019/document.
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La gestion thermique est un des moyens de réduction de la consommation spécifique d’un véhicule. Avec le réchauffement climatique, les normes de dépollution deviennent de plus en plus sévères et les constructeurs automobiles cherchent à améliorer le rendement des véhicules. Le but de ces travaux de recherche est de valoriser, par simulation numérique, les nouveaux systèmes de gestion thermique en fonction du cycle d’homologation et de la température ambiante.Un modèle de simulation 1-D du moteur et de ses circuits de refroidissement et de lubrification ont été développés en utilisant le logiciel GT-Suite. Quatre cycles d’homologation ont été choisis : NEDC, WLTC, AH et AU. De plus, un nouveau cycle a été proposé durant cette étude. Le bilan d’énergie effectué pendant les différentes phases des cycles souligne l’importance du stockage et de la récupération d’énergie.Le stockage d’énergie dans un volume eau et/ou d’huile abouti à l’amélioration de la montée en température des deux fluides. Plusieurs configurations ont été proposées comme, par exemple, un carter d’huile multifonctionnel.Ainsi, une réduction importante de la consommation en carburant est obtenue.La récupération de chaleur au sein des gaz d’échappement est ensuite mise en oeuvre. L’échangeur est caractérisé sur un banc d’essais puis modélisé. Le réchauffement indirect et direct d’huile abouti à une réduction importante des frottements et de la consommation. Une configuration est proposée afin de contrôler la température maximale de l’huile.Finalement, différentes stratégies comme : le type d’huile, l’isolation du moteur, une température de régulation plus élevée etc… ont été étudiées et valoriséesThermal management proved itself in improving the fuel efficiency of the engine. Nowadays, automotive companies tend to apply different strategies to answer the greenhouse severe laws. The PhD aim is to valorize and analyze the different thermal management strategies with numerical simulations over different driving cycles and ambient conditions. A 1-D simulation code of the engine and its hydraulic circuits were built using GT-Suite. Four known driving cycles were chosen: NEDC, WLTC, AH and AU. In addition, an in-house developed driving cycle was introduced. An energy balance made over the different stages of the driving cycles underlines the importance of the heat storage and the exhaust heat recovery strategies.Heat recovery was applied over the coolant and the oil at ambient temperatures of -7°C and 20°C. Hot coolant storage and hot oil storage led to improve the coolant and lubricant initial temperatures respectively. Different configurations (total of 7) were proposed and studied. A multifunctional oil sump was introduced. Important fuel consumption savings were obtained. Exhaust heat recovery was then valorized. Heat exchanger was characterized over experimental setup then added to the engine model. Indirect and direct heating of the lubricant as well as both strategies back to back were tested. Remarkable friction reduction and fuel savings were obtained. Special configuration was proposed to control the lubricant high temperature instead of the bypass on the exhaust line. The study ended by valorizing minor strategies as the oil’s grade influence, the engine insulation, high temperature set point …
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Silva, Thadeu Alfredo Farias 1961. "Atenuação témica interna nos grupos geradores de energia utilizando trocadores de calor de água gelada controlada." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266690.
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Orientador: Elias Basile TambourgiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-21T04:26:11Z (GMT). No. of bitstreams: 1 Silva_ThadeuAlfredoFarias_M.pdf: 5396797 bytes, checksum: fb0ca3ed2816b12c4c4ee60aeceb38e7 (MD5) Previous issue date: 2012
Resumo: Este trabalho apresenta o dimensionamento e cálculos do trocador de calor duplo-tubo de cotato indireto e troca direta, aplicado nas instalações dos geradores elétricos a combustão, com o objetivo de analisar a viabilidade de um projeto para tratamento do ar quente gerado dentro das estruturas metálicas ou canópias. Os dados coletados basearam-se no levantamento de registros de temperatura internas e externas dos geradores, velocidade, pressão e vazão do ar quente nos dutos de saída e por último a utilização de equações da termodinâmica para obtenção dos resultados. Acrescentam-se ainda aos cálculos as propriedades dos fluidos, as dimensões dos tubos e as propriedades térmicas da tubulação do aço, materiais estes utilizados na sua construção. Comparadas as curvas de registros levantadas, obteve-se as temperaturas médias de entrada e saída e interna do motor com média de 27,694°C, 40,814°C e 33,383°C, respectivamente. No caso das curvas de registros da vazão e a diferença de pressão apresentaram pouca oscilação, sendo consideradas como constantes e iguais a 20,496 m3/h e 80,138 Pa, respectivamente. Após os balanços energéticos, o trocador de calor de duplo-tubo ficou determinado como sendo: diâmetro do tubo interno 3 ½ polegada e diâmetro do tubo externo de 6 polegadas, ambos de aço carbono com 13,52 pés de comprimento linear de troca de calor. Usando uma vazão de 1,4 m3/h de água a 23°C, obteve-se uma taxa de troca de calor no sistema de 0,4719 Btu/h. A contribuição deste trabalho é possível com a determinação da taxa de calor trocada no sistema do trocador de calor e assim garantir-se que esta opção de instalação pode ser controlada para obter-se a atenuação térmica interna nos grupos geradores de energia
Abstract: This paper presents the design and calculation of the heat exchanger double-tube indirect and direct exchange, applied on the premises of the combustion electric generators, in order to analyze the feasibility of a project for the treatment of hot air generated within the metal structures or canopies. The data collected were based on survey records of internal and external temperature of generators, speed, pressure and flow of hot air in the ducts output and finally the use of equations of thermodynamics to obtain the results. It is further added to the calculations the fluid properties, the dimensions of the pipes and the thermal properties of the steel pipe, these materials used in its construction. Comparing the curves of records raised, there was obtained the average temperatures of the inlet and outlet and the internal engine ° C mean 27.694, 40.814 ° C to 33.383 ° C, respectively. In the case of records of flow curves and pressure difference showed little change, being considered as constant and equal to 20.496 80.138 m3/he Pa, respectively. After the energy balances the heat exchanger double-tube was determined to be: diameter of the inner tube 3 ½ inch diameter and 6 inch outer tube, both made of carbon steel with 13.52 feet long linear heat exchange . Using a flow rate of 1.4 m3 / h of water at 23 ° C, there was obtained a rate of heat exchange in the system of 0.4719 Btu / hr. The contribution of this work it is possible to determine the rate of heat exchanged in the heat exchanger system and ensure that there is attenuation in internal thermal energy generators
Mestrado
Sistemas de Processos Quimicos e Informatica
Mestre em Engenharia Química
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Vikberg, Tommy. "Industrial Wood Drying : Airflow Distribution, Internal Heat Exchange and Moisture Content as Input and Feedback to the Process." Doctoral thesis, Luleå tekniska universitet, Träteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26339.
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At a sawmill, the most energy demanding process is the wood drying. The drying process also has a great impact on quality parameters determined for the boards in the final sorting and thereby affects the sales value to a great extent. The objective of the work described in this compilation thesis was to find ways to improve the industrial wood drying process through better input, feedback and process itself. As input and feedback to the drying process, ways to improve the accuracy in estimating the moisture content (MC) was investigated. For the drying process itself, an investigation of the airflow distribution in a batch kiln at several different fan speeds was performed. Potential energy savings by introducing a new kiln layout was also investigated.To estimate the green MC, i.e. the MC of boards prior to drying, the average green MC of batches rather than individual boards were considered since large batches are handled in the drying anyway. Two different methods were investigated, one method in which the MC of the heartwood was presumed to be constant and a certain relation between the heartwood and sapwood basic density was present. In the other method, the average basic density was estimated as a function of the logs diameters. It was found that both methods worked satisfactory.To improve the accuracy in measuring the MC of the dried boards two approaches were used. The first approach was to combine different measurement techniques, i.e. microwaves and X-rays, to predict the same properties with a multivariate approach. By adding X-ray measurements to microwave measurements, the amount of boards with a predicted MC deviating less than 1% MC from the oven dry reference increased with 7%. The second approach was to investigate the potential of increasing the measurable board area by compensating for the vicinity of the boards edge with aid of a function developed through final element simulations. It was shown that this was possible although the magnitude of the improvement will depend on the actual measurement setup.The airflow distribution in drying was investigated by industrial trials in which the air speed was measured simultaneously at 20 spots throughout the load with the air circulating fans run at a number of different speeds. It was found that the airflow distribution did not change remarkably as a function of the fan speed and once the airflow is measured at a certain fan speed, the effect of changing the fan speed can be estimated using the fan affinity laws. Finally, potential energy savings with a new kiln layout was investigated through drying simulations and associated determinations of the drying air condition in the kiln. It was found that heat savings of roughly 30% could be accomplished in comparison to a kiln with no heat recovery.Godkänd; 2015; 20150527 (tomvik); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Tommy Vikberg Ämne: Träfysik/Wood Physics Avhandling: Industrial wood drying Airflow distribution, Internal Heat Exchange and Moisture Content as Input and Feedback to the Process Opponent: Professor Mihaela Campean, Transilvania University of Brasov, Brasov, Romania Ordförande: Professor Diego Elustondo, Avd för träteknologi, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet, Skellefteå Tid: Fredag 9 oktober kl 10.00 Plats: Hörsal A i Skellefteå, Luleå tekniska universitet
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Parida, Pritish Ranjan. "Optimization and Fabrication of Heat Exchangers for High-Density Power Control Unit Applications." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/77165.
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The demand for more power and performance from electronic equipment has constantly been growing resulting in an increased amount of heat dissipation from these devices. Thermal management of high-density power control units for hybrid electric vehicles is one such application. Over the last few years, the performance of this power control unit has been improved and size has been reduced to attain higher efficiency and performance causing the heat dissipation as well as heat density to increase significantly. However, the overall cooling system has remained unchanged and only the heat exchanger corresponding to the power control unit (PCU) has been improved. This has allowed the manufacturing costs to go down. Efforts are constantly being made to reduce the PCU size even further and also to reduce manufacturing costs. As a consequence, heat density will go up (~ 200 – 250 W/cm2) and thus, a better high performance cooler/heat exchanger is required that can operate under the existing cooling system design and at the same time, maintain active devices temperature within optimum range (<120 – 125 °C) for higher reliability.
The aim of this dissertation was to study the various cooling options based on jet impingement, mini-channel, ribbed mini-channel, phase change material and double sided cooling configurations for application in hybrid electric vehicle and other similar consumer products and perform parametric and optimization study on selected designs. Detailed experimental and computational analysis was performed on different cooling designs to evaluate overall performance. Severe constraints such as choice of coolant, coolant flow-rate, pressure drop, minimum geometrical size and operating temperature were required for the overall design. High performance jet impingement based cooler design with incorporated fin-like structures induced swirl and provided enhanced local heat transfer compared to traditional cooling designs. However, the cooling scheme could manage only 97.4% of the target effectiveness. Tapered/nozzle-shaped jets based designs showed promising results (~40% reduction in overall pressure drop) but were not sufficient to meet the overall operating temperature requirement. Various schemes of mini-channel arrangement, which were based on utilizing conduction and convection heat transfer in a conjugate mode, demonstrated improved performance over that of impingement cooling schemes. Impingement and mini-channel based designs were combined to show high heat transfer rates but at the expense of higher pressure drops (~5 times). As an alternate, mini-channel based coolers with ~1.5 mm size channels having trip strips or ribs were studied to accommodate the design constraints and to enhance local as well as overall heat transfer rates and achieve the target operating temperature.
A step by step approach to the development of the heat exchanger is provided with an emphasis on system level design. The computational based optimization methodology is confirmed by a fabricated test bed to evaluate overall performance and compare the predicted results with actual performance.
Additionally, one of the impingement based configuration (Swirl-Impingement-Fin) developed during the course of this work was applied to the internal cooling of a turbine blade trailing edge and was shown to enhance the thermal performance by at least a factor of 2 in comparison to the existing pin-fin technology for the conditions studied in this work.Ph. D.
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Milovanović, Nebojša. "A study of controlled auto ignition (CAI) combustion in internal combustion engines." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/19906.
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Controlled Auto Ignition (CAI) combustion is a new combustion principle in internal combustion engines which has in recent years attracted increased attention. In CAI combustion, which combines features of spark ignition (SI) and compression ignition (CI) principles, air/fuel mixture is premixed, as in SI combustion and auto-ignited by piston compression as in CI combustion. Ignition is provided in multiple points, and thus the charge gives a simultaneous energy release. This results in uniform and simultaneous auto-ignition and chemical reaction throughout the whole charge without flame propagation. CAI combustion is controlled by the chemical kinetics of air/fuel mixture with no influence of turbulence. The CAI engine offers benefits in comparison to spark ignited and compression ignited engines in higher efficiency due to elimination of throttling losses at part and idle loads. There is a possibility to use high compression ratios since it is not knock limited, and in significant lower NOx emission (≈90%) and particle matter emission (≈50%), due to much lower combustion temperature and elimination of fuel rich zones. However, there are several disadvantages of the CAI engine that limits its practical application, such as high level of hydrocarbon and carbon monoxide emissions, high peak pressures, high rates of heat release, reduced power per displacement and difficulties in starting and controlling the engine. Controlling the operation over a wide range of loads and speeds is probably the major difficulty facing CAI engines. Controlling is actually two-components as it consists of auto-ignition phasing and controlling the rates of heat release. As CAI combustion is controlled by chemical kinetics of air/fuel mixture, the auto-ignition timing and heat release rate are determined by the charge properties such as temperature, composition and pressure. Therefore, changes in engine operational parameters or in types of fuel, results in changing of the charge properties. Hence, the auto-ignition timing and the rate of heat release. The Thesis investigates a controlled auto-ignition (CAI) combustion in internal combustion engines suitable for transport applications. The CAI engine environment is simulated by using a single-zone, homogeneous reactor model with a time variable volume according to the slider-crank relationship. The model uses detailed chemical kinetics and distributed heat transfer losses according to Woschini's correlation [1]. The fundamentals of chemical kinetics, and their relationship with combustion related problems are presented. The phenomenology and principles of auto-ignition process itself and its characteristics in CAI combustion are explained. The simulation model for representing CAI engine environment is established and calibrated with respect to the experimental data. The influences of fuel composition on the auto-ignition timing and the rate of heat release in a CAI engine are investigated. The effects of engine parameters on CAI combustion in different engine concepts fuelled with various fuels are analysed. The effects of internal gas recirculation (IEGR) in controlling the auto-ignition timing and the heat release rate in a CAI engine fuelled with different fuels are investigated. The effects of variable valve timings strategy on gas exchange process in CAI engine fuelled with commercial gasoline (95RON) are analysed.
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Ávila, Márcio Turra de. "Estudo de motor de combustão interna, do Ciclo Otto, movido a etanol previamente vaporizado." Universidade de São Paulo, 1994. http://www.teses.usp.br/teses/disponiveis/18/18135/tde-09102015-153544/.
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O etanol (álcool etílico) tem sido cada vez mais estudado e testado como combustível alternativo para substituição do uso de alguns derivados de petróleo em motores de combustão interna. O presente trabalho procura abordar o emprego do etanol na forma vaporizada em motores do ciclo Otto, objetivando a obtenção de melhores níveis de rendimento térmico total. Deste modo, um motor para teste de octanagem (motor CFR) foi equipado com um vaporizador de álcool instalado no coletor de escapamento, e após uma série de ensaios, várias análises puderam ser feitas. Essas considerações procuraram se ater a aspectos como rendimento térmico, relação ar/combustível, ângulo de avanço da centelha, temperatura de escape, assim como potência e eficiência volumétrica, levando em conta, sempre, a sua influência no funcionamento geral do motor. Ficou constatado que o motor movido a etanol vaporizado apresenta rendimento consideravelmente maior, menor consumo de combustível e funcionamento mais suave que aqueles verificados quando o mesmo motor e alimentado com álcool líquido.The ethanol (ethyl alcohol) has been studied more and more as alternative fuel to replace some petroleum derivatives for internal combustion engines. The attached study examines the application of vaporized ethanol for Otto cycle engines, searching for better levels of total thermal efficiency. Therefore, an engine for test of octane number (CFR motor) was equipped with an alcohol vaporizer installed inside the escape pipe, and after many experiences, several analysis were made. The various analysis included aspects as thermal efficiency, air/fuel ratio, advance ignition, escape temperature, power and volumetric efficiency, always considering their influence on the operation of the engine. It was confirmed that the engine moved by vaporized ethanol presents higher thermal efficiency, smaller fuel consumption and smoother working than in case of alimentation by liquid alcohol.
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Foral, Štěpán. "Výměníky tepla Sodík - Oxid uhličitý pro JE se sodíkem chlazeným rychlým reaktorem (SFR)." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229965.
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This master’s thesis deals with a design of Na-CO2 heat exchanger. There is a comparison of shell and tube heat exchanger with PCHE in the first part. Further the shell and tube heat exchanger with internally finned tubes was chosen as the basic conception. There was performed an optimization of construct and operations parameters for this concept. The optimization was performed on the basis of thermal and hydraulic calculations. Further there were performed calculations for ensuring of safe operation of the heat exchanger. The conclusion of the diploma thesis deals with comparison of the designed heat exchanger with similar projects.
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Boulanger, Adrien. "Exemples de systèmes dynamiques : comptage en mesure infinie, enlacement sur le tore et échanges d'intervalles affines." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS250.
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On étudie dans cette thèse plusieurs systèmes dynamiques de nature géométrique. Le premier chapitre est consacré à l’étude de la fonction orbitale associée à certains groupes kleiniens de co-volumes infinis. Le deuxième chapitre est de nature plus topologique et discute les liens entre nombres d’enlacement et systèmes dynamiques. Le dernier chapitre concerne l’étude d’un exemple d’échanges d’intervalles affines, généralisation naturelle des échanges d’intervallesWe study in this thesis some geometric flavoured dynamical systems. The first chapter is dedicated to the asymptotic study of the orbital function associated to Kleinian groups of infinite co-volume. The second one is more topologic and deals with the notion of linking number and its dynamical related aspects. The last chapter is about the study of affine interval exchanges through a particular example
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Haddad, Elie. "Modélisation zéro-D des écoulements à l’admission d’un moteur à combustion interne. : Application au boîtier papillon et au refroidisseur d’air suralimenté." Thesis, Ecole centrale de Nantes, 2016. http://www.theses.fr/2016ECDN0020.
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La modélisation système d’un moteur à combustion interne est une étape indispensable à la procédure d’évaluation des performances du moteur avant sa mise au point au banc d’essais. En se passant du montage et du démontage des pièces et des capteurs, ainsi que du coût d’opération d’un banc moteur, la simulation permet de réduire le temps et le coût général. Par ailleurs, il est indispensable d’avoir un modèle de simulation fiable qui permet de reproduire le comportement du moteur avec précision et avec un temps de calcul réduit. Ce mémoire se concentre sur deux éléments du système d’admission d’un moteur à combustion interne à allumage commandé : le boîtier papillon, et le Refroidisseur d’Air Suralimenté. De nouveaux modèles à zéro dimension sont développés en se basant sur les résultats du banc d’essai du laboratoire. Tout d’abord un banc d’essai de boîtier papillon est utilisé pour isoler l’écoulement à travers le papillon des phénomènes qui ont lieu dans le moteur et qui pourraient affecter les mesures ou se superposer. Ensuite un banc moteur est utilisé et des essais en régime stabilisé et transitoire sont effectués. Les nouveaux modèles sont introduits dans un logiciel de simulation Amesim et validés par comparaison avec un champ complet de mesures sur le banc moteur. Le nouveau modèle de boîtier papillon améliore la précision et permet de prendre en compte les différentes conditions de fonctionnement du moteur. Le nouveau modèle d’efficacité thermique du Refroidisseur d’Air Suralimenté permet de déterminer la température d’air en sortie de cet élément sous différentes conditions ainsi qu’en régime stabilisé et transitoire. Les nouveaux modèles développés contribuent donc à l’amélioration de la modélisation 0D du système d’admission d’un moteur à combustion interne à allumage commandéThe modeling of an internal combustion engine is an essential step in the process of evaluation of the engine’s performance before using an engine test bench. The simulation allows saving time and costs, which would otherwise result from all the experimental procedures like the use of sensors, the mounting and dismounting of parts and the operational cost of an engine test bench. Nonetheless, it is essential to have a reliable simulation model that can reproduce the engine’s behavior accurately and with a reduced calculation time. This thesis focuses on two elements of the intake system in a spark ignition internal combustion engine: the throttle body, and the charge air cooler. New zero-dimensional models are developed based on experimental results from the laboratory’s test benches. First, an isolated throttle body test bench is used in order to isolate the flow through the throttle valve from external phenomena which occur in an engine and could affect the reliability of the measurements. Then, an engine test bench is used, in order to perform steady and unsteady experiments. The new models are introduced into the simulation software Amesim and validated by comparison with a field of measurements across the whole engine’s range on the test bench. The new model of throttle body improves accuracy and allows taking into account the different operating conditions of the engine. The new thermal efficiency model of the charge air cooler determines the air outlet temperature of this element under different conditions and in steady and unsteady states. Thus, the new models developed contribute to improving the zero dimensional modeling of the intake system of a spark ignition internal combustion engine
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Chi-yu, Liu, and 劉起宇. "Experimemtal Analysis in Convective Heat Transfer for an Internally Finned Tube Heat Exchanger." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/44358804774156170183.
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碩士國立高雄海洋科技大學
輪機工程研究所
99
Abstract The purpose of this study is to investigate the heat transfer as well as friction characteristics of a double pipe heat exchanger with internal fins. A counterflow arrangement is made for the hot water and cold water which serve as the working fluids. Smooth, four-fin, and eight-fin tubes are tested with an inclination angle of 0°, 30°, 60° and 90° in the test. In addition, with a well-stirred design, the hot water is kept around 70 ℃ in the hot bathing constant-temperature reservoir whereas the cold water temperature is set at 20 ℃. The temperature and pressure differences are recorded as the working fluids are pumped through the test unit. For a fully developed flow, the tested Reynolds number ranges from 250 to 750. The effects of flow velocities and fin numbers on the Nusselt number and friction factor of the tested heat exchangers are determined. It is shown that the heat transfer characteristics of the exchanger with fins is better than that with smooth tube. The more the fins installed in exchanger, the better the heat transfer performance will be. In addition, the inclination of the heat exchanger will enhance the heat transfer especially in natural convection.