Dissertations / Theses: 'Numerical simulation of plate heat exchangers'

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Al-Azzawi, Huda Jasim Mohammed [Verfasser]. "Numerical Simulation of Heat Transfer and Fluid Flow in Additively Manufactured Plate-Fin Heat Exchangers with Wavy Fins / Huda Jasim Mohammed Al-Azzawi." Hannover : Gottfried Wilhelm Leibniz Universität, 2021. http://d-nb.info/123822203X/34.

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Sarraf, Kifah. "Echangeurs à plaques corruguées en mode monophasique et en condensation : études expérimentale, numérique et analytique, et analyse des écoulements et des transferts thermiques." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4760/document.

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Ce travail de recherche examine aux échelles globale et locale les caractéristiques thermo-hydrauliques au sein des échangeurs à plaques ondulées pour les écoulements monophasiques et en mode condensation. Il comprend deux parties :La première partie concerne l'analyse des structures d'écoulement en mode monophasique à partir d'un outil de simulations numériques, et dont les résultats sont validés à partir d'une campagne expérimentale. L'exploitation des résultats de simulations, à partir d'observables judicieusement sélectionnées, a permis de quantifier les grandes classes d'écoulement en fonction des paramètres géométriques et fluidiques de l'échangeur. Ce nouvel éclairement sur les structures d'écoulement a conduit à la proposition d'un modèle général original sur les lois de friction au sein de ces échangeurs de géométrie d'écoulement complexe.La deuxième partie concerne l'étude de la condensation de la vapeur avec et sans surchauffe en entrée de l'échangeur. Ainsi, un dispositif expérimental permettant le contrôle précis des conditions aux limites a été développé, et une métrologie spécifique, basée sur la thermographie infrarouge a également été mis au point, afin de remonter à certaines grandeurs locales le long du condenseur (titre de vapeur, coefficient d'échange thermique...). On observe ainsi une très forte variabilité des coefficients d'échanges thermiques et de la densité de flux de chaleur le long du condenseur, et la surchauffe de la vapeur tend à intensifier les transferts thermiques. Ce complément de mesures remet en question certaines hypothèses de la littérature quant à l'élaboration de corrélations sur les transferts de chaleur dans les condenseurs
This research work examines at the global and local scales the thermo-hydraulic characteristics of plate heat exchangers with corrugated chevron plates, for single-phase and condensation flows. The study is divided into two parts:The first part concerns the analysis of flow structures of single-phase flows using numerical simulations, which are validated using the results of the experimental campaign. The analysis of the simulations results, from a flow characteristic observable that has been carefully chosen, has allowed quantifying the main flow categories as a function of the heat exchanger geometric parameters and the flow characteristics. This new information on the flow structures has led to the proposal of an original generalized model of the friction law inside this type of heat exchanger with complex geometry.The second part concerns the study of condensation with and without vapor superheating at the inlet of the heat exchanger. Thus, a specific experimental setup allowing precise control of the boundary conditions has been developed. Otherwise a specific metrology, based on infrared thermography, has been set to the point in order to determine the variation of certain local quantities along the condenser (vapor mass fraction, heat transfer coefficient...). Thus, we observe a high and wide variability of the heat transfer coefficients and the heat flux density along the condenser, and the superheating of the vapor tends to increase the heat transfers. These additional measures question certain assumptions of the literature regarding the development of heat transfer correlations in plate heat condensers

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Marques, Alfredo Manuel Nobre. "Modelação e avaliação do desempenho de permutadores de calor." Master's thesis, Universidade de Évora, 2009. http://hdl.handle.net/10174/20930.

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O estudo de permutadores de calor baseado em modelos é um tipo de abordagem que, nas últimas décadas, tem merecido particular atenção, tanto pelos investigadores como em desenvolvimento de aplicações práticas, já que estes equipamentos são equipamentos imprescindíveis no funcionamento da generalidade das indústrias, sistemas de energia (centrais termoeléctricas, refinarias, etc.), sistemas de climatização e sistemas de propulsão terrestre, aeronáutica e marítima. Em instalações de máquinas marítimas, os permutadores de calor são determinantes para o bom funcionamento do navio, pois são utilizados tanto na instalação propulsora como em vários sistemas auxiliares. Nos últimos anos, por motivos de eficiência e de espaço ocupado, tem-se assistido à substituição de permutadores de calor do tipo corpo cilíndrico e feixe tubular por permutadores de calor de placas. O presente trabalho centrou-se no estudo de permutadores de calor de placas, tendo como objectivo fundamental contribuir para o desenvolvimento do estado da arte neste domínio do conhecimento, através do ensaio e modelação de permutadores de calor de placas com corrugações do tipo "chevron". Desenvolveu-se em quatro fases. A primeira fase consistiu na obtenção de valores experimentais relativos a um permutador de calor de placas e a um permutador de corpo cilíndrico e feixe tubular, integrados numa bancada de ensaio de permutadores de calor, existente nos laboratórios da ENIDH (Escola Superior Náutica Infante D. Henrique). Para idênticas condições de funcionamento compararam-se valores experimentais, tendo-se assim verificado as razões que motivaram a substituição anteriormente referida. Ainda nesta fase efectuou se a análise da incerteza experimental, bem como a avaliação das grandezas que mais contribuem para essa incerteza. A segunda fase consistiu na modelação analítica do permutador de calor de placas, através da utilização de correlações existentes na bibliografia. Uma vez que os resultados obtidos não foram satisfatórios, estabeleceram-se novas correlações através das quais se desenvolveu um modelo cujos resultados mostraram uma boa concordância com os resultados experimentais. Para condições próximas da potência máxima, foi determinada a sensibilidade do modelo desenvolvido relativamente a variações possíveis de se verificar em instalações de máquinas marítimas. A terceira fase consistiu na simulação numérica tridimensional do permutador de calor de placas, utilizando um código comercial CFD, através da qual se analisou a influência das corrugações, das condições de fronteira e dos topos das placas no comportamento do permutador de calor de placas. Apesar de serem de aplicação trabalhosa e de processamento lento, as simulações numéricas conduziram a resultados satisfatórios, do ponto de vista de engenharia, e abrem caminho para a modelação de outras geometrias de permutadores de calor. A quarta fase consistiu na análise do comportamento do permutador de calor de placas quando os fluidos envolvidos fossem, para além da água doce, a água do mar e o óleo lubrificante (típicos de instalações de máquinas marítimas. Esta análise foi efectuada através do modelo analítico, baseado nas novas correlações desenvolvidas. - ABSTRACT: The study of heat exchangers based on models is an approach that has received major attention in the last decades, both in research and in the development of applications for industrial equipments. The use of heat exchangers is universal in power stations, refineries, air-conditioning systems and propulsion systems (land, aeronautical and maritime). ln marine power plants, heat exchangers are essential for the correct operation of the ship, considering they are used in main propulsion machinery and in auxiliary systems. During the last years, for reasons of efficiency and occupied space, conventional shell and tube heat exchangers have been replaced by more efficient and compact plate heat exchangers. This work is focused on the study of plate heat exchangers, being the key objective to contribute to the development of the state of the art in this field through testing and modeling of plate heat exchanger with corrugate plate type "chevron". The present work has been developed in four phases: The first phase consisted in obtaining experimental data of plate and shell and tube heat exchangers from a heat exchanger training bench existing at ENIDH (Escola Superior Náutica Infante D. Henrique). For identical operating conditions, experimental data has been analyzed and compared and reason that motivated the replacement of the heat exchangers has been confirmed. Also, in this working phase, experimental uncertainty and evaluation of the quantities that most contribute for this uncertainty have been analyzed. The second phase consisted in the analytical modeling of the same plate heat exchangers, through the use of correlations available in the literature. Since the results obtained were not satisfactory, new correlations were developed, which resulted in a new model that showed a good agreement with experimental data. For conditions dose to the maximum power, the sensitivity of the developed model was evaluated considering possible changes in the operating conditions of real marine propulsion plants. The third phase consisted three-dimensional numerical simulation of same plate heat exchangers, using a commercial computer fluid dynamics (CFD) application. The influence of plate configuration, boundary conditions and plate tops on the behavior of plate heat exchangers has been analyzed. Despite being laborious and a computationally heavy numerical simulations led to satisfactory result, from an engineering point of view, and open new possibilities for the simulation of heat exchangers with other geometrical configurations. The fourth phase consisted in the analysis of the heat exchanger performance when different fluids like fresh water, sea water and lubricating oil, typical of marine power plants. This analysis was carried out using the model based on new correlations developed in the phase two, mentioned above.

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TITO, JOSÉ MIGUEL MAYTA. "SIMULATION OF BRAZED PLATE HEAT EXCHANGERS FOR CASCADE VAPOR COMPRESSION SISTEM." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=18986@1.

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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
Desenvolveu-se um modelo de simulação para trocadores de calor de placas soldadas (BPHE – Brazed Plate Heat Exchanger) operando em regime permanente em um sistema de refrigeração em cascata por compressão de vapor, ou seja, condensador, trocador de calor intermediário (ou condensador em cascata) e evaporador. O modelo adota o método de análise local, onde o trocador de calor é dividido em uma série de pequenos volumes de controle, para os quais as equações de troca de calor e de conservação de massa e de energia são aplicadas. Para o calculo dos coeficientes locais de transferência de calor e fator de atrito foram utilizadas correlações disponíveis na literatura, considerando as regiões de escoamento monofásico ou bifásico em cada um dos trocadores, Estas correlações cobrem valores de fluxo de calor entre 2,5 kW/m2 e 185 kW/m2, temperaturas de saturação entre 5 graus Celsius e 30 graus Celsius, e aplicam-se a geometrias com ângulos de corrugação entre 20 e 60 graus. Um programa computacional foi desenvolvido em FORTRAN para o cálculo do desempenho térmico dos trocadores de calor e das correlações de asida dos dois fluidos. Na simulação foram consideradas conhecidas as condições de entrada dos fluidos e a geometria do trocador. As propriedades termo-físicas dos fluidos foram calculadas utilizandose a mais recente versão do padrão NIST de referência de propriedades termodinâmicas e de transporte (REFPROP 9.0), permitindo a simulação dos trocadores de calor operando com uma vasta gama de refrigerantes. Os resultados da simulação foram comparados com os dados experimentais (condensador e evaporador) levantados por outros autores para os refrigerantes R22 e R290, tendose obtido boa concordância. Uma analise de sensibilidade para os trocadores de calor, utilizando os novos refrigerantes R1234yf e R1234ze, foi também realizada.
A simulation model of brazed plate heat exchangers (BPHE) operating in steady-state in a cascade vapor compression refrigeration system has been developed. For this system the heat exchangers were the condenser, intermediate heat exchanger or cascade-condenser and evaporator. The model adopts a local analysis method, where the heat exchanger is divided into a series of small control volumes, to which the heat transfer rate equations and the fundamental of conservation of mass and energy equation. Local heat exchanger coefficients and friction factor are calculated using correlations available in literature, considering regions of single-phase or twophase flow for each one of the heat exchangers. These correlations have heat flux values ranging from 2,5kW/m2 to 185kW/m2, saturation temperatures from 5 degrees Celsius to 35 degrees Celsius and were applied to geometries with corrugation angle ranging from 20 degrees to 60 degrees. In order to calculate the thermal performance of the heat exchangers and the output conditions of the two fluids a computational program was developed in FORTRAN. This simulation considers known inlet conditions of the fluids and the geometry of the heat exchanger. The thermophysical properties of the refrigerants fluids were calculated using the version 7 of REFPROP, a package by NIST (National Institute of Standards and Technology), that allow for the simulation of heat exchangers with a wide operating range of refrigerants. The simulation results were compared with experimental data (condenser and evaporator) for R22 and R290 refrigerants, obtaining a good agreement. A sensibility analysis for heat exchangers, using the new R1234yf and R1234ze has also been carried out.

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Galati, Chiara. "Experimental and numerical study of flow distribution in compact plate heat exchangers." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19928/1/GALATI_Chiara.pdf.

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This PhD work was motivated by the CEA R&D program to provide solid technological basis for the use of Brayton power conversion system in Sodium-cooled Fast nuclear Reactors (SFRs). Multi-channel compact heat exchangers are necessary for the present application because of the low heat transfer capacity of the gas foreseen. In ASTRID project, a minimum size of Na channels section is required to avoid the plugging risk. However, this induces very low pressure losses in the bundle. Considering an additional inlet flow condition, a real risk of bad flow distribution remains. As a result, the thermal performance and thermal loading of the heat exchanger degrades due to it. The main goal of this work was to overcome the flow maldistribution problem by means of an innovative design of sodium distribution system (PATENT FR1657543), the development of a numerical strategy and the construction of an experimental database to validate all theoretical studies. The innovative sodium distribution system consists on an inlet header which tries to guide the evolution of the impinging jet flow while a system of bifurcating pre-distribution channels increases pressure drops in the bundle. Lateral communications between pre-distribution channels are introduced to further homogenize the flow. Two experimental facilities have been conceived to study the flow behavior in bifurcating channels and in the inlet header, respectively. At the same time, their effect on the flow distribution between channels is evaluated. The acquired PIV aerodynamic database allows to validate the numerical models and to prove the design basis for the proposed distribution system. Once having validated the CFD turbulence models and the strategy to study the flow maldistribution in the SGHE module, a decisive and trustworthy optimization of each component of the sodium distribution system has been performed. Finally, an optimal configuration has been proposed for the actual phase of ASTRID project.

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Protheroe, Michael. "Simulation of variable fluid-properties plate heat exchanger for educational purposes thesis submitted in partial fulfilment of the Masters degree in Engineering, Auckland University of Technology, October 2003." Full thesis. Abstract, 2003. http://puka2.aut.ac.nz/ait/theses/ProtheroeM.pdf.

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Rastan, Hamidreza. "Investigation of the heat transfer of enhanced additively manufactured minichannel heat exchangers." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264278.

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Mini-/microchannel components have received attention over the past few decades owing to their compactness and superior thermal performance. Microchannel heat sinks are typically manufactured through traditional manufacturing practices (milling and sawing, electrodischarge machining, and water jet cutting) by changing their components to work in microscale environments or microfabrication techniques (etching and lost wax molding), which have emerged from the semiconductor industry. An extrusion process is used to produce multiport minichannel-based heat exchangers (HXs). However, geometric manufacturing limitations can be considered as drawbacks for all of these techniques. For example, a complex out-of-plane geometry is extremely difficult to fabricate, if not impossible. Such imposed design constraints can be eliminated using additive manufacturing (AM), generally known as three-dimensional (3D) printing. AM is a new and growing technique that has received attention in recent years. The inherent design freedom that it provides to the designer can result in sophisticated geometries that are impossible to produce by traditional technologies and all for the redesign and optimization of existing models. The work presented in this thesis aims to investigate the thermal performance of enhanced minichannel HXs manufactured via metal 3D printing both numerically and experimentally. Rectangular winglet vortex generators (VGs) have been chosen as the thermal enhancement method embedded inside the flat tube. COMSOL Multiphysics, a commercial software package using a finite element method (FEM), has been used as a numerical tool. The influence of the geometric VG parameters on the heat transfer and flow friction characteristics was studied by solving a 3D conjugate heat transfer and laminar flow. The ranges of studied parameters utilized in simulation section were obtained from our previous interaction with various AM technologies including direct metal laser sintering (DMLS) and electron-beam melting (EBM). For the simulation setup, distilled water was chosen as the working fluid with temperaturedependent thermal properties. The minichannel HX was assumed to be made of AlSi10Mg with a hydraulic diameter of 2.86 mm. The minichannel was heated by a constant heat flux of 5 Wcm−2 , and the Reynolds number was varied from 230 to 950. A sensitivity analysis showed that the angle of attack, VG height, VG length, and longitudinal pitch have notable effects on the heat transfer and flow friction characteristics. In contrast, the VG thickness and the distance from the sidewalls do not have a significant influence on the HX performance over the studied range. On the basis of the simulation results, four different prototypes including a smooth channel as a reference were manufactured with AlSi10Mg via DMLS technology owing to the better surface roughness and greater design uniformity. A test rig was developed to test the prototypes. Owing to the experimental facility and working fluid (distilled water), the experiment was categorized as either a simultaneously developing flow or a hydrodynamically developed but thermally developing flow. The Reynolds number ranged from 175 to 1370, and the HX was tested with two different heat fluxes of 1.5 kWm−2 and 3 kWm−2 . The experimental results for the smooth channel were compared to widely accepted correlations in the literature. It was found that 79% of the experimental data were within a range of ±10% of the values from existing correlations developed for the thermal entry length. However, a formula developed for the simultaneously developing flow overpredicted the Nusselt number. Furthermore, the results for the enhanced channels showed that embedding VGs can considerably boost the thermal performance up to three times within the parameters of the printed parts. Finally, the thermal performance of the 3D-printed channel showed that AM is a promising solution for the development of minichannel HXs. The generation of 3D vortices caused by the presence of VGs ii can notably boost the thermal performance, thereby reducing the HX size for a given heat duty.

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Paniagua, Sánchez Leslye. "Three-dimensional numerical simulation of fluid flow and heat transfer in fin-and-tube heat exchangers at different flow regimes." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/277561.

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This thesis aims at unifying two distinct branches of work within the Heat Transfer Technological Center (CTTC). On one side, extensive experimental work has been done during the past years by the researchers of the laboratory. This experimental work has been complemented with numerical models for the calculation of fin and tube heat exchangers thermal and fluid dynamic behavior. Such numerical models can be referred to as fast numerical tool which can be used for industrial rating and design purposes. On the other hand, the scientists working at the research center have successfully developed a general purpose multi-physics Computational Fluid Dynamics (CFD) code (TermoFluids). This high performance CFD solver has been extensively used by the co-workers of the group mainly to predict complex flows of great academic interest. The idea of bringing together this two branches, comes from the necessity of a reliable numerical platform with detailed local data of the flow and heat transfer on diverse heat exchanger applications. Being able to use local heat transfer coefficients as an input on the rating and design tool will lead to affordable and accurate prediction of industrial devices performance, by which the center can propose enhanced alternatives to its industrial partners. To accomplish these goals, several contributions have been made to the existing TermoFluids software which is in continuous evolution in order to meet the competitive requirements. The most significant problematics to adequately attack this problem are analyzed and quite interesting recommendations are given. Some of the challenging arising issues involve the generation of suitable and affordable meshes, the implementation and validation of three dimensional periodic boundary condition and coupling of different domains with important adjustments for the study of cases with different flow physics like time steps and thermal development. Turbulence is present in most of engineering flows, and refrigeration evaporator heat exchangers are not an exception. The presence of many tubes (acting like bluff bodies for the flow) arranged in different configurations and the fact that the flow is also confined by fins, create complex three dimensional flow features that have usually turbulent or transition to turbulent regime. Therefore, three dimensional turbulent forced convection in a matrix of wall-bounded pins is analyzed. Large Eddy Simulations (LES) are performed in order to assess the performance of three different subgrid-scale models, namely WALE, QR and VMS. The Reynolds numbers of the study were set to 3000, 10000 and 30000. Some of the main results included are the pressure coefficient around the cylinders, the averaged Nusselt number at the endwalls and vorticity of the flow. The final part of the thesis is devoted to study the three dimensional fluid flow and conjugated heat transfer parameters encountered in a plate fin and tube heat exchanger used for no-frost refrigeration. The numerical code and post processing tools are validated with a very similar but smaller case of a heat exchanger with two rows of tubes at low Reynolds for which experimental data is available. The next analysis presented is a typical configuration for no-frost evaporators with double fin spacing (for which very few numerical data is reported in the scientific literature). Conjugated convective heat transfer in the flow field and heat conduction in the fins are coupled and considered. The influence of some geometrical and flow regime parameters is analyzed for design purposes. In conclusion, the implementations and general contributions of the present thesis together with the previous existent multi-physics computational code, has proved to be capable to perform successful top edge three dimensional simulations of the flow features and heat transfer mechanisms observed on heat exchanger devices.
Esta tesis tiene como objetivo unificar dos ramas de trabajo dentro del Centro Tecnológico de Transferencia de Calor (CTTC). Por un lado, se ha realizado un amplio trabajo experimental durante los últimos años. Este trabajo experimental se ha complementado con modelos numéricos para el estudio de intercambiadores de calor de tipo aleta-tubo. Tales modelos numéricos pueden considerarse una herramienta numérica de bajo coste empleada con propósitos de diseño principalmente. Por otro lado, los científicos que trabajan en el centro han desarrollado con éxito un código de Dinámica de Fluidos Computacionales (TermoFluids). Este código de alto rendimiento ha sido ampliamente utilizado principalmente para predecir flujos complejos de gran interés académico. La idea de unir a estas dos ramas, proviene de la necesidad de una plataforma numérica fiable con datos locales propios del flujo y de la transferencia de calor en diversas aplicaciones de intercambiadores de calor. Ser capaz de generar coeficientes locales de transferencia de calor para abastecer con datos propios los modelos existentes de bajo coste, permitirá la correcta predicción del rendimiento de dichos dispositivos. Para lograr estos objetivos, se han hecho varias contribuciones al código TermoFluids que está en continua evolución. Algunas de las mayores cuestiones que se plantean implican la generación de mallas adecuadas y asequibles, la implementación y validación de la condición de contorno periódica tridimensional y el acoplamiento de los diferentes dominios para el estudio de casos con diferentes comportamientos físicos, como desarrollo transitorio e inercia térmica. La turbulencia está presente en la mayoría de los flujos de ingeniería, y los intercambiadores de calor de evaporadores para refrigeración no son una excepción. La presencia de muchos tubos (que actúan como obstáculos para el fluido) colocados en diferentes configuraciones y el hecho de que el flujo también está confinado por aletas, crean características de flujo tridimensionales complejas que tienen generalmente régimen turbulento o en transición. Por lo tanto, se analiza la convección forzada turbulenta en una matriz de pines delimitados por paredes. simulando las grandes escalas de turbulencia y modelando las pequeñas (LES) con el fin de evaluar el desempeño de los tres modelos seleccionados, a saber WALE, QR y VMS. Los números de Reynolds establecidos para el estudio son 3000, 10000 y 30000. Algunos de los principales resultados que se incluyen son el coeficiente de presión alrededor los cilindros, el número de Nusselt promedio en las paredes y la vorticidad del flujo. La parte final de la tesis se dedica a estudiar el flujo tridimensional y los parámetros de transferencia de calor encontrados en un intercambiador de calor de tipo aleta-tubo utilizado para la refrigeración doméstica en equipos de 'no-escarcha'. Las implementaciones del código y el postproceso numéricos se validan en un caso muy similar para un intercambiador de calor con dos filas de tubos a bajos Reynolds para el cual se dispone de datos experimentales. El siguiente análisis que se presenta es una configuración típica para evaporadores 'no-escarcha' con paso de aleta doble (para el que se tiene muy poca información numérica en la literatura). Se considera el acoplamiento conjugado de la transferencia de calor convectiva entre fluido y sólido y conductiva dentro de la aleta. La influencia de algunos parámetros geométricos y de régimen de flujo se analizan con propósitos de diseño. En conclusión, las contribuciones generales de esta tesis junto con el código computacional ya existente, ha demostrado ser capaz de realizar con éxito simulaciones tridimensionales para predecir las características del flujo y los mecanismos responsables de la transferencia de calor en intercambiadores de calor de tipo aleta-tubo

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Panse, Satchit Pradip. "A Numerical Investigation of Thermal-Hydraulic Characteristics in Three Dimensional Plate and Wavy Fin-Tube Heat Exchangers for Laminar and Transitional Flow Regimes." Thesis, Montana State University, 2005. http://etd.lib.montana.edu/etd/2005/panse/PanseS0805.pdf.

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The plate fin-and-tube heat exchangers are used in wide variety of industrial applications, particularly in the heating, air-conditioning and refrigeration industries. In most cases the working fluid is liquid on the tube side exchanging heat with a gas, usually air. The current study is focused on two fin configurations, the plain plate-fin and the wavy-fin. These two fin configurations are numerically investigated in both staggered and in-lined tube layouts. The present investigation ranges from laminar flow regime into the sub-critical or transitional flow regime. The suitability of the eddy viscosity turbulence models for the flow representation in the transitional flow regime is discussed in this study. This study reveals that the flow distinction between plain and wavy fin has a profound influence on the heat transfer and flow friction performance of these configurations when compared on the basis of tube layouts. The obtained results also indicate that the number of tube rows plays an important part for the overall heat exchanger performance and an optimum choice for the number of tube rows must be made in order to achieve the critical balance between high heat transfer performance and low pressure drop. It was observed that for an optimum number of tube rows, increasing the longitudinal or transverse tube pitch causes a decrease in the thermal and hydraulic performance of the heat exchanger. For the transitional flow regime, the k-Ï‰ turbulence model was found to be more suitable than the k-Îµ based turbulence models. This suitability of the k-Ï‰ turbulence model was linked to the better near wall treatment by this model as compared to the k-Îµ based models. The results for the fin pitch study indicated that the decrease in the fin pitch causes a decrease in both heat transfer and flow friction characteristics for the transitional flow regime. The results also suggested that for the transitional flow regime, for an equal wavy height, the thermal and hydraulic performance is increased as the wavy angle is increased. On the other hand, for an equal wavy angle, it is decreased as the wavy height is increased.

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ZHANG, JIEHAI. "NUMERICAL SIMULATIONS OF STEADY LOW-REYNOLDS-NUMBER FLOWS AND ENHANCED HEAT TRANSFER IN WAVY PLATE-FIN PASSAGES." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1109015881.

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Godoy, Sérgio Machado de. "Eficiência térmica de trocadores de calor compactos através de simulação numérica." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18147/tde-19012011-140852/.

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Um novo método numérico, para o cálculo da performance térmica de trocadores de calor com fluxos cruzados é apresentado. Dados referentes a efetividade - número de unidades de transferência (\'épsilon\' - NUT) para vários arranjos de escoamento, padronizados e complexos, foram obtidos usando esta metodologia. Os resultados foram validados através da comparação dos resultados com soluções analíticas conhecidas, para trocadores de calor de fluxos cruzados com um ou múltiplos passes, possuindo de uma até várias fileiras de tubos, e com soluções aproximadas utilizando séries infinitas, para trocadores com ambos os fluidos não misturados. Todos os resultados obtidos apresentaram erros muito pequenos, em relação às soluções analíticas e aproximadas. Dados para efetividade, para arranjos complexos de escoamento são apresentados.
A new numerical methodology for thermal performance calculation in cross-flow heat exchangers is developed. Data related to effectiveness - number of transfer units (\'épsilon\' - NTU) for several standard and complex flow arrangements are obtained using this methodology. The results are validated through comparison with analytical solutions for one or more pass cross-flow heat exchangers with one to four rows and with approximate series solution for an unmixed-unmixed heat exchanger, obtaining in all cases very small errors. New effectiveness data for some complex configurations are provided.

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Quenum, Alphonse Codjo. "Étude de l'encrassement des échangeurs de chaleur en géométrie plane modélisation et simulation expérimentale par dépôt de glace." Vandoeuvre-les-Nancy, INPL, 1998. http://www.theses.fr/1998INPL139N.

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L’objet du présent rapport est l'étude de l'encrassement des échangeurs de chaleur à plaques. On s'intéresse à l'encrassement par changement de phase, et plus particulièrement à la solidification dans une phase liquide. Ce travail comporte deux parties : une première partie, qui est une étude numérique, permet d'explorer l'influence de certains paramètres (débit, température), le type de refroidissement (symétrique ou asymétrique), ainsi que l’aspect stationnaire et instationnaire du refroidissement et de la solidification. La seconde partie, qui est expérimentale, a permis d'analyser l'influence des paramètres tels que (débits et températures des deux fluides) sur l'évolution du dépôt de glace les résultats expérimentaux ont permis en outre de faire une application du critère entropique de l'étude thermodynamique de l'encrassement, développée sur la géométrie plane.

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Ali, Samer. "Concept innovant d'échangeur/réacteur multifonctionnel par contrôle dynamique passif par générateurs de vorticité flexibles." Thesis, Valenciennes, 2015. http://www.theses.fr/2015VALE0034/document.

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Le but de cette étude est d’étudier l’utilisation d’interactions fluide-structure (FSI) pour améliorer le transfert de chaleur et les performances de mélange dans des échangeurs-réacteurs multifonctionnels, et d’évaluer des configurations pour lesquelles l’objectif est de produire et de maintenir un régime dynamique auto-entretenu d’oscillations des générateurs de tourbillons flexibles. Dans un premier temps, deux études numériques ont été réalisées pour des écoulements laminaires bidimensionnels. Les résultats montrent qu’un minimum de trois générateurs de tourbillons alternés est nécessaire pour produire une instabilité qui engendre les oscillations de larges amplitudes. L’ajout de deux promoteurs coplanaires en amont déstabilise l’écoulement en créant des forces périodiques agissant sur les générateurs de tourbillons en aval. Il en résulte une augmentation de la vitesse réduite qui impose un blocage en fréquence des oscillations des générateurs de tourbillons en aval. Dans cette configuration, des oscillations de larges amplitudes sont obtenues pour uniquement deux générateurs de tourbillons en aval. Les oscillations des générateurs de tourbillons produisent une vorticité intense qui a une incidence positive que le transfert de chaleur et sur le mélange. Dans un second temps, une configuration tridimensionnelle HEV incluant des générateurs de tourbillons trapézoïdaux flexibles orientés a 45◦ vers l’amont est étudiée par simulations numériques. Une analyse FFT réalisée sur les coefficients issus d’une analyse POD montre un pic fréquentiel correspondant aux formations et lâchers tourbillonnaires périodiques. Cette fréquence dominante correspond bien au mode propre d’oscillation des générateurs de tourbillons et engendre ainsi de larges amplitudes d’oscillations
The aim of this study is to investigate the use of fluid-structure interaction (FSI) to improve heat transfer and mixing performances in multi-functional heat exchangers/reactors, and to evaluate configuration designs where the main target is to produce and maintain self-sustained oscillations of flexible vortex generators. At first, two dimensional laminar flow studies are numerically investigated. The results show that a minimum of three alternating flaps is needed to produce an instability that leads to large displacement oscillations. However, the introduction of two co-planar flaps upstream destabilizes the flow by creating periodic forces that act on the alternating downstream flaps. Hence, this results in artificially increasing the reduced velocity that will induce the alternating flaps to be in a lock-in state. Thus in this case, large displacement amplitudes are created with two alternating flaps only. The free flaps oscillations produce vortices of higher strength which have a positive impact on heat transfer and mixing. Secondly, a three dimensional HEV configuration with flexible trapezoidal vortex generators inclined with an angle of 45◦ with respect to the wall and reversed opposite to the flow direction is numerically investigated. Fast Fourier Transformation is applied on the temporal variation of the Proper Orthogonal Decomposition (POD) coefficientswhich displays a dominant peak in the flow and corresponds to the vortices periodic formation and detachment. This dominant frequency synchronizes well with the structural oscillation frequency and the fundamental frequency of the tabs reaching a lock-in state and leading to large oscillation amplitudes

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Brum, Ruth da Silva. "Teoria Construtal e desempenho térmico de Trocadores de Calor Solo-Ar." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/153247.

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Trocadores de Calor Solo-Ar (TCSA) são dispositivos usados para melhorar o condicionamento térmico de ambientes construídos. Eles funcionam através da ventilação do ar por um ou mais dutos enterrados, utilizando o solo como fonte ou sumidouro de calor. Em virtude da defasagem entre as temperaturas do ar e das camadas superficiais da Terra, é possível resfriar o ar no verão e aquecê-lo no inverno. Seus princípios de operação baseiam-se na mecânica dos fluidos e transferência de calor, áreas onde a teoria Construtal tem sido usada para melhorar o desempenho, ou reduzir imperfeições, de vários sistemas térmicos, após uma estratégica análise de suas geometrias (ou de seu design), também chamada de método Design Construtal que se fundamenta na lei construtal. Dessa lei, projetos em engenharia devem começar, por exemplo, descobrindo as arquiteturas que facilitam o escoamento entre uma fonte pontual e um volume, ou vice-versa. Explorando esses conceitos para TCSA, onde a corrente é o calor que flui entre os dutos e o solo, esta tese objetiva centralmente avaliar o desempenho térmico desses dispositivos em função de possíveis desenhos de suas estruturas. Particularmente, isso foi feito: (1) usando um duto e variando seu diâmetro e vazão de ar; (2) inserindo novos dutos, até um total de cinco, mantendo a vazão de ar constante, e estudando diversas disposições geométricas. Numericamente, foram empregados dois modelos testados e validados a partir de dados experimentais, que foram simulados no código comercial de dinâmica dos fluidos computacional, FLUENT, o qual baseia-se em métodos de volumes finitos. As geometrias e malhas foram geradas no software GAMBIT. Dos resultados numéricos, esta tese também avançou desenvolvendo novos modelos para o conceito de potencial térmico instantâneo, que é uma medida das diferenças de temperatura entre a saída e a entrada dos dutos de TCSA. Descobriu-se que estes modelos podiam ser simplificados em termos de funções senoidais, facilitando análises e definições analíticas subsequentes, criando um quadro resumo para grandes volumes de dados simulados. Das avaliações dos resultados nos estudos com um duto, foram encontradas faixas para a obtenção de rendimentos térmicos anuais estimados em pelo menos 80%, com mudanças no diâmetro e/ou vazão do ar. Analisando múltiplos dutos, foram reveladas melhorias significativas de rendimento com: (1) o aumento no número de dutos; (2) a redução, até certos limites, da razão entre os espaçamentos verticais e horizontais entre eles; (3) a ampliação da razão entre o volume da instalação e o volume do domínio computacional. Destaca-se, ainda, que em todos os casos foram calculados balanços energéticos, com a estimativa das taxas (e quantidade) de calor trocado, bem como da energia elétrica consumida pelos ventiladores, mostrando sua viabilidade no condicionamento de ar com redução do consumo de energia elétrica.
The Earth-Air Heat Exchangers (EAHE) are devices used to improve the thermal conditions of built environments. They work by blowing the air inside buried ducts to use the soil as heat source or sink. Due to a phase difference between the air and ground temperatures, it is possible to cool the air in the summer and heat it in the winter. These operating principles are based on the areas of fluid mechanics and heat transfer, where the Constructal theory has been used to improve the performance, or reduce imperfections, of several thermal systems, after a strategic evaluation of their geometries (or their design), also called Constructal Design method, which is anchored by the constructal law. From this law, engineering projects should begin, for example, finding the architectures which ease the flow between a source point and a volume, or vice versa. Bringing these concepts to EAHE, where the current is the heat which flows between the ducts and the soil, this thesis mainly aims to assess the thermal performance of EAHE due to possible designs of their layouts. Particularly, this was done by: (1) adopting one duct and varying its diameter and/or the air flow; (2) using up to five ducts, keeping the air flow constant, and studying various geometric shapes. Numerically, two models were used, which have been tested and validated from experimental data, and the simulations were done in the CFD software FLUENT, which is based in the finite volume methods. The geometries and meshes were generated by the software GAMBIT. From the numerical results, this thesis also pursued developing new models for the concept of the instantaneous thermal potential, which is a measure of the temperatures differences between the ducts outlet and inlet. It was found that these models can be simplified in terms of sinusoidal functions, helping analysis, definitions, and creating a framework to summarize large volumes of simulated data. From the evaluation of the data in the studies with one duct, ranges for changes in their diameter and/or air flow were found to obtain at least 80% of estimated annual efficiency. Analyzing multiple ducts, significant improvements in efficiency were also obtained by: (1) increasing the number of ducts; (2) reducing, to some extent, the ratio between their vertical and horizontal spacings; (3) increasing the ratio between the installation volume and the computational domain. It should also be highlighted that in all cases the energy balances were computed, to find the rates (and amounts) of exchanged heat, as well as the electric energy consumed by the fans, showing the economic viability of using EAHE as devices for air conditioning.

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15

Eder, Robert. "Ein Beitrag zur Entwicklung neuartiger keramischer Wärmeübertrager für Rekuperatorbrenner." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2015. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-158628.

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Die Effektivität keramischer Wärmeübertrager kann durch eine feinere Strukturierung der Oberflächen gesteigert werden. Dies kann durch die Integration textiler Urformen anstatt der konventionell im Schlickguss hergestellten gröberen Geometrien erfolgen. Für Strukturierungen in Form von wandgebundenen Halbbögen werden die Ergebnisse umfangreicher experimenteller und numerischer Untersuchungen zu den wärmetechnischen und strömungsmechanischen Eigenschaften vorgestellt. Basierend auf den Erkenntnissen der mittels numerischer Simulation durchgeführten Parameterstudie werden verschiedene Empfehlungen für eine optimierte Anordnung der Halbbögen gegeben, um das Verhältnis von Wärmeübergang zur Druckverlust zu verbessern. Die experimentellen Ergebnisse belegen die Richtigkeit der gewählten Randbedingungen und Vereinfachungen im numerischen Modell. Des Weiteren wurden die Strömungsstrukturen mit laserdiagnostischen Messmethoden umfangreich charakterisiert.

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16

MANSOURI, KACEM. "Etude theorique et experimentale du transfert de chaleur en regime periodique pour un ecoulement force a plan directeur." Nantes, 1995. http://www.theses.fr/1995NANT2085.

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Ce travail a pour objet l'analyse du couplage conduction-convection forcee en regime thermique variable, dans le cas d'un ecoulement fluide entre plaques paralleles epaisses. Il s'agit de preciser la fonction de transfert obtenue pour une excitation periodique imposee a l'entree du fluide. L'etude comprend trois parties: la premiere est consacree a l'analyse theorique dans le cas d'un ecoulement laminaire a plan directeur. Le couplage est traite en ecrivant l'egalite des flux et des temperatures a l'interface (condition limite dite de type 4). Une solution analytique a ete developpee moyennant l'hypothese d'un profil de vitesse uniforme (slug flow). Ce probleme est egalement resolu a l'aide du modele quasi-stationnaire, le couplage a l'interface est alors assure en introduisant la notion de coefficient de convection. La deuxieme partie concerne la simulation numerique d'un ecoulement fluide en regime laminaire entre deux plaques paralleles. Le champ dynamique est considere etabli parabolique. La reponse thermique est etudiee en fonction des differents parametres du probleme, tels que la frequence du signal d'entree et les caracteristiques thermophysiques du fluide et du solide. Le modele numerique utilisant une formulation explicite aux differences finies est valide par rapport a la solution exacte developpee dans la premiere partie. En regime turbulent, des profils classiques de distribution de vitesse et de viscosite sont utilises dans un modele pseudo-laminaire. Les resultats sont alors compares a ceux obtenus simplement par l'utilisation du nombre de nusselt. La troisieme partie est relative a l'etude experimentale d'un ecoulement d'eau dans un canal rectangulaire de section 300 x 20 mm#2 et de longueur 3 m. Les parois sont en acier inoxydable de 5 mm d'epaisseur. Le fluide aborde le canal ainsi defini avec une temperature d'entree evoluant selon une loi temporelle periodique. On s'interesse a la distribution de temperature longitudinale dans l'axe du canal et a la paroi. En pratique, nous disposons de deux parametres, a savoir le nombre de reynolds et la frequence du signal d'entree. Les resultats experimentaux sont confrontes aux modeles precedents

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17

Li, Guo-jen, and 李國楨. "The numerical simulation of thermofluids and entropy generation in plate heat exchangers." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/54426938301597817615.

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碩士
國立中央大學
機械工程研究所
98
In this study, a three dimensional calculation with real-size geometry of K070 chevron plate heat exchanger which consisted of thee flow channels have been conducted. The characteristics of flow, pressure drop and heat transfer in plate heat exchangers are investigated numerically. Also, the analyses of second law of thermodynamics (i.e. entropy generation) are presented. The numerical simulations are carried out using ANSYS FLUENT with water as working fluid in the Reynolds number (Re) range from 300-12000, which cover laminar and turbulent regime, and numerical results were validated with empirical and analytical correlations. The numerical friction factors are found in good agreement within 5% for turbulent flow and average error of 11% for laminar flow with empirical correlations. Nusselt number (Nu) correlations of cold and hot water side which obtained by numerical results have been proposed. Values of numerical Nu correlations agree within empirical and analytical correlations. Deviations of computed Nu with empirical and analytical correlations are up to 36%. The analyses of entropy generation indicate that the optimal Re of K070 plate heat exchangers is 3900. A model of three channels chevron plate heat exchanger considered conjugate heat transfer has been established. It can be useful to verify the design concepts in the early research and development.

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18

Liu, Min Sheng, and 劉敏生. "Numerical Simulation of 3-D Turbulent Flow and Heat Transfer in Plate Finned-Tube Heat Exchangers." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/07845506593497081497.

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19

Wu, Mu-Cheng, and 吳目誠. "Numerical simulation of the thermal and hydraulic characteristics of the plate finned-tube heat exchangers." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/97565344022276791459.

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碩士
國立成功大學
機械工程研究所
83
Fluid flow and heat transfer in a plate-fin and tube heat exchanger were studied numerically. Flow is incompressible, three-dimensional and laminar. A commercial PHOENICS code which is based on the SIMPLE algorithm are used to solve a set of nonlinear partial differential equations. The effects of different geometrical parameters such as tube arrangement, tube row numbers, fin pitch (8-12 fins per inch), tube diameter, and tube spacing are investigated in detail for the Reynolds number (based on the fin spacing and the frontal velocity) ranging from 60 to 900. The local information of pressure and heat transfer coefficient can offer important message for basic research and the design of heat exchanger. The average heat transfer coefficient of staggered arrangement is higher 15﹪- 27﹪than that of in-lined arrangement , while the pressure drop of staggered configuration is higher 20﹪- 25﹪than that of in- lined configuration. Average Nusselt number is decreased as the number of tube row is increased from 1 to 6. It is also found that the number of tube row has a small effect on the average heat transfer coefficient as the row numbers are greater than 4. For staggered arrangement, as the tube diameter increases from 3/8〞to 7/8〞, the average heat transfer coefficient increase 56﹪, and the pressure drop increases 2.3 times. For in-lined arrangement, the tube diameter effect has little influence on average heat transfer coefficient, but the pressure drop increases as the tube diameter increases. When the tube spacing is decreased from 44 mm to 28 mm, the average heat transfer coefficient is increased 62﹪and 32﹪for staggered and in-lined arrangement, respectively ; the pressure drop is increased 100 ﹪and 72﹪.

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20

Shih, Po Jen, and 施博仁. "Experimental Analysis and Numerical Simulation in the Effects of Viscous on the Performance of Plate Heat Exchangers." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/09063968499003037216.

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21

Shu-WeiChang and 張書維. "Three Dimensional Numerical Simulation of Parallel Plate Stack Heat Exchanger in Beta-type Stirling Engine." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/92097027817994095145.

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碩士
國立成功大學
機械工程學系
102
Three Dimensional Numerical Simulation of Parallel Plate Stack Heat Exchanger in Beta-type Stirling Engine Author : Shu-Wei Chang Advisor : Chang-Da Wen National Cheng Kung University Department of Mechanical Engineering SUMMARY This study considers three dimensional parallel plate stack in beta-type Stirling engine to observe the effect of dimensionless width and kinetic Reynolds number on time-space average friction coefficient and Nusselt number of the heat exchanger. Correlations among these parameters are eventually built and will be helpful to design better Stirling engine heat exchanger. Key words: Beta-type Stirling Engine, Parallel Plate Stack Heat Exchanger, Oscillatory flow, Three Dimensional Numerical Simulation. INTRODUCTION In recent years, the study of low temperature difference and focus type solar Stirling engine are booming. The heat exchanger performance becomes more important to the engine overall efficiency. In previous numerical investigations of Stirling engine heat exchanger, two dimension numerical simulation and straight pipe are often chosen for discussion. In this research three dimensional wall boundary condition is taken into consideration and the numerical simulation is conducted. This research is mainly analyzed the effect of the dimensionless width and kinetic Reynolds number of the parallel plate stack in beta type Stirling engine. The friction coefficient and Nusselt number of the heated plate are investigated. The “annular effect” (i.e. the maximum axial velocity in a fast oscillatory flow) can be clearly observed near the wall either in velocity or temperature field in three dimensional model. The change of dimensionless width do not affect the annular effect, but when kinetic Reynolds number arises, the annular effect becomes more apparent and important near the wall. At last, correlations are established to express time-space average friction coefficient and Nusselt number with dimensionless width and kinetic Reynolds number. The importance of dimensionless width and kinetic Reynolds number on time-space average friction coefficient and Nusselt number are observed and analyzed. METHOD The main purpose of this research is to carry out the simulation in parallel plate stack in beta type Stirling engine and conduct the analysis for the fluid flow and the heat transfer. The oscillatory flow in the Stirling engine is driven by the sinusoidal displacer under three dimensional wall boundary condition. The commercial software Ansys is first used to establish the physical model and mesh. The whole model is then numerically simulated by Fluent. Because of the large change near the plate entrance and the exit, the method of discretization should use higher order to discrete continuity, momentum, energy equation. QUICK (Quadratic Upwind Interpolation for Convective Kinematics) scheme is employed to discrete the convection term, and the second-order central difference method is adopted for the diffusion term. SIMPLE (Semi-Implicit Method for pressure-Linled Equation) scheme is chosen as the simulation method for iteration. The tested kinetic Reynolds number ranges from 100 to 1000. The dimensionless width is examined from 4 to 40. Then the corresponding friction coefficient and Nusselt number at different kinetic Reynolds number and dimensionless width are found. RESULTS AND DISCUSSION From the results, the “annular effect” is also discovered in three dimensional simulation, not only in velocity field but also in temperature field. The maximum time-space average Nusselt number occurs near the wall. The “annular effect” is more visible with higher kinetic Reynolds number, but independent of the dimensionless width. The comparison of results between two dimensional model and the symmetry plane in three dimensional model is obtained. Also the results of overall plate in three dimension are compared and studied. From Figure 1, a correlation is obtained to calculate time-space average friction coefficient of the parallel plate stack in beta type Stirling engine with kinetic Reynolds number and dimensionless width. Time-space Nusselt number is divided into two distributions. One is with dimensionless width below 10 which is shown in Figure 2 and the other is above 10 which is shown in Figure 3. Figure 1 The correlation to express time-space average friction coefficient with dimensionless width and kinetic Reynolds number. Figure 2 The correlation to express time-space average Nusselt number with dimensionless width below 10 and kinetic Reynolds number. Figure 3 The correlation to express time-space average Nusselt number with dimensionless width above 10 and kinetic Reynolds number. CONCLUSION The purpose of this research is to analyze the flow and heat transfer characteristics of three dimensional parallel plate stack heat exchanger in beta type Stirling engine by numerical simulation. By changing dimensionless width and kinetic Reynolds number, the influence of the three dimensional walls on flow and heat transfer are investigated. Then Nusselt number and friction coefficient of the whole plate are further discussed. Findings from this study are as follows. 1. The “annular effect” exists not only in velocity field but also in temperature field for the reciprocating flow in three dimensional stack plate. 2. Friction coefficient of the symmetry plane exists a constant difference with two dimensional results. Nusselt number of the symmetry plane is consistent with two dimensional results at long dimensionless width. However, while kinetic Reynolds number increases, the dimensionless width needs to be longer. 3. Time-space average friction coefficient of the whole plate is independent of dimensionless width. It becomes lower with higher kinetic Reynolds number. A maximum time-space average Nusselt number of the whole plate is found at dimensionless width 10 regardless of the change of kinetic Reynolds number. 4. At last, correlations are established to express time-space average Nusselt number and friction coefficient with dimensionless width and kinetic Reynolds number. It will be helpful to design better heat exchanger in Stirling engine.

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22

Hsieh, Wu-Lun, and 謝武倫. "Three-dimensional Numerical Analysis of Plate-Fin Heat Exchangers." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/41003746414814974596.

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碩士
元智大學
機械工程學系
94
This paper has investigated the performance of the plate-fin heat exchangers numerically. The validity of the used CFD software was confirmed first by comparing the obtained numerical results of the fin surface temperature distribution and the region of the condensation on the fin surface with the measured data by previous experiments. The results of this thesis can be used as a guildline of the designers of heat exchangers. The parameters studied in the present work include the relative humidity of the inlet air, the height of the fin, the width of the fin, the space between the fins, the thickness of the fin, the velocity of the inlet air and the base temperature of the fin. From the simulation results, it has been observed that the corresponding fin performance becomes worse with higher relative humidity of the inlet air, lower height of the fin, smaller width of the fin, narrower space between the fins, thinner of the fin, faster velocity of the approaching air and highter base temperature of the fin. It is also found that the most influential parameter is the thickness of the fin.

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23

Park, Won Cheol. "Numerical simulation of sub-cooled flow boiling /." Diss., 2003. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3086962.

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24

Dai, Hong-Yu, and 戴鴻宇. "A numerical study for fluid in chevron type plate heat exchangers." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/47822373906259243441.

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碩士
義守大學
機械與自動化工程學系碩士班
96
In this work, the flow characteristic in the plate heat exchanger is investigated. The cross-corrugated channel is formed by two opposite directions of chevron plates. A CFD (Computational Fluid Dynamics) codes FLUENT is employed to simulate the flow through the channel. Water is used as the working fluid and the range of the Reynolds number is from 1500 to 5500.Eleven turbulence models provided by FLUENT are implemented for calculation. The numerical results are validated by the experimental measurements. The results show the accuracy of prediction by the turbulence model k –ε realizable with Enhance wall-function is the best among the turbulence models. The velocity fields and pressure drops in different locations are presented and discussed. The differences between the numerical predictions and experimental measurement are less than 18% for all eleven models in the range of study.

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25

Tzeng, Guang-bin, and 曾廣彬. "Numerical analysis of flow and flow maldistribution in plate heat exchangers." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/17050219316906468581.

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碩士
國立中央大學
機械工程研究所
98
In the present study, the thermal convection characteristics and pressure drop in a corrugated chevron plate of real-size plate heat exchangers have been investigated. A commercial CFD code FLUENT is employed to simulate the water through the channel. The consequence of comparison the different turbulent model with empirical correlations for friction factor shows that Realizable k-ε model has better accuracy, the maximum error is only 8%. This study also test the performance of three thermal boundary conditions (constant wall temperature, heat flux and convection type conditions), and find the convection boundary condition is the most realistic for a plate heat exchanger. Through a series of verification, the accuracy of numerical model in this work has been established. The numerical result shows the flow and temperature pattern and flow maldistribution. The flow patterns are cross flow for the plates of K070 and K050 when Reynolds number is 302. When Reynolds number increases upto 4075, the zig-zag flow could be found for the cases of K070 and K050. On the other hand, The flow pattern is kept as cross flow type for K200 plate for whole range of Reynolds number (from 302 upto 4178). The K200 case has the most severe maldistribution among theee plates. Based on numerical study, adjust the layout of corrugation can reduce the level of flow maldistribution. The simulation results can provide a valuable design guide on improving the performance the plate heat exchanger.

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26

Kuo-ChiangHu and 胡國強. "Three-dimensional Numerical Analysis of In-line Plate Finned-tube Heat Exchangers." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/73840515248861476615.

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碩士
國立成功大學
機械工程學系專班
100
The present study applies the Three-dimensional numerical analysis methods to predict the average heat transfer coefficient and heat transfer coefficient under the isothermal situation on a vertical square fin of the two-tube plate finned-tube heat exchangers for in-line arrangements and various fin spacings . And further with compare the numerical inverse scheme with the experimental data in the literature to predict the average heat transfer coefficient and heat transfer coefficient under the isothermal situation . In additions, the present study also applies the commercial software ‘Icepak’in conjunction with the present experimental data to obtain the inter-fin flow field of the plate finned-tube heat exchanger and temperature measurements at various measurement locations of the fin. Results show that and in nature convection increase with increasing the fin spacing S. These values can respectively approach their corresponding asymptotic values obtained from a single square fin as S . However, and in mixed convection increase with increasing the S and air velocity. Furthermore, in order to prove the reliability of the present heat transfer coefficient under the isothermal situation results . Compared with some of the experimental formula and inverse scheme results can be obtained to verify their accuracy and reasonableness.

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27

許幼新. "Semi-Empirical Numerical Analysis of Plate Heat Exchangers Using Supercritical Carbon Dioxide." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/34378760269056099381.

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28

Zhu, Yan-Cheng, and 朱彥丞. "Numerical Analysis of Two Phase Flow and Flow Maldistribution in Plate Heat Exchangers." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/80161816770246004966.

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碩士
國立中央大學
機械工程研究所
100
In the recent years, most of investigations of two phase flow distribution in plate heat exchanger (PHE) were experimental study. Due to complexity of flow and thermal structure inside PHE, researchers used simpler flat/circular tubes to represent the real plate in PHE. This study used the Computational fluid dynamics software ANSYS FLUENT to model an industrial type of K050 chevron corrugation PHE and simulated the two phase flow distribution. Several eﬀects were studied, including two phase flow, flow maldistribution, the operating condition and the direction of the inflow distributor. This paper was divided into two parts. First, the air/water two phase flow was investigated for effect of various direction of air inflow distributor (12 clock, 3 clock, 4 clock, 5 clock, 6 clock and 9 clock) in the single channel PHE. Simulation results showed that the direction of 3, 4 and 6 clocks generated better flow distribution. At low Reynolds number (Rel =500), the case of 3 clock had the most uneven flow distribution, while better flow distribution was observed for the case of 6 clock. At medium Reynolds number (Rel =1500), all the three cases (3, 4, 6 clocks) improved their flow distribution with reduced standard deviation of flowrate. It can be concluded that the increase of the Reynolds number which transformed the flow into turbulent and improved the flow distribution across channels inside PHE. At the high Reynolds number (Rel =3000), the case of 4 clock had the best even flow distribution. Finally, consider the effects of the flow passages on the hot/cold sides and the pressure drop, air inflow at 4 clock of the distributor was recommended. The second part was investigation for the improvement of two phase flow distribution in a 10-channel PHE with an inflow distributor. Numerical results showed that at the multi-channels PHE without the distributor, the flow must operated at higher Reynolds number in order to have better flow distribution. If the PHE operated under Reynolds number lower than 1500, the vapor-liquid distribution can very uneven. With the inflow distributor added, the maldistribution of the vapor phase improved significantly. Yet the flow distribution of liquid phase only worked at low Reynolds number condition. As Reynolds number increased, the inflow distributor was not that effective for liquid flow distribution.

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29

Lai, Chien Hung, and 賴建宏. "Experimental Analysis and Numerical Simulation in Various Types of Heat Exchangers." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/06039270172363093277.

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碩士
中原大學
機械工程研究所
82
To enhance the efficiency of a plate heat exchanger,it is necessary to modify the dimension and shape of the flowing channel inside the heat exchanger.To achieve this goal,the first step of the study is to analyze the variation of flowing field in the plate heat exchanger.The second step requires to select an optimized structure,and finally,to evaluate the performance of heat exchangers form experiments. To evalate the efficiency of plate heat exchangers,we selected three testing models which have different channel inclination angles of 37,45 and 60.The experimental results showed that the one with the angle of 45 has the maximum heat transfer rate.The results form the numerical simulation by FIDAP also showed a similar trend as those given by experiments .Hence,we can confirm that the optimized design of the inclination angle in the duct structure of the plate heat exchanger is 45. In the study of performance in finned tube heat exchangers ,the experimental data showed that in the air side the heat transfer coefficient increases while the fin's density,the number of fins per unit length, increases.We can conclude that for finned tube heat exchangers, the higher fin's density gives the better heat tranfer performance.

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30

Randow, Jakob. "Heat Flux Analysis of Deep Borehole Heat Exchangers." 2020. https://htwk-leipzig.qucosa.de/id/qucosa%3A73812.

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In urban areas with limited space, deep borehole heat exchangers (DBHE) are coupled with ground source heat pump systems (GSHPS) to extract geothermal energy for building heating purposes. They can exploit more heat than common shallow systems. In this thesis, the open source software OpenGeoSys (OGS) has been utilized to analyse the long-term behavior and temperature evolution in and around single and multiple DBHEs. Moreover, an analysis to reduce the computation time has been applied. This way, the simulation time could be shortened by almost 75% by adjusting the tolerance of the non-linear solver and using an automatic time stepping in a first step. With larger element sizes, which still provide a sufficient result precision, the required duration could be shortened to less than 2% compared to the first method. Especially between the top and the bottom a layer size of 100 m is sufficient. The thickness around the top and bottom, however, should be small to avoid numerical inaccuracies. In the first years of operation most of the energy is extracted by the lower parts of the DBHE. Throughout the years, the contribution along the depth becomes more homogeneous and more soil is influenced. In summer, the top approximately 900 m are not contributing to the heat extraction but instead losing heat to the soil because of a low energy demand, which leads to high inflow temperatures. Considering the results of the in- and outflow temperature evolution, a single DBHE should be preferred over multiple systems. Nonetheless, those can multiply the extractable heat in a certain area and could be more economical.:List of Figures . . . v List of Tables . . . vii 1 Introduction . . . 1 2 Theoretical Background . . . 4 2.1 BHE equations . . . 5 2.2 Thermal Resistance . . . 6 2.3 Exchange Area . . . 10 2.4 Coefficient of Performance . . . 10 2.5 OpenGeoSys Pipe Network Feature . . . 12 3 Modeling Scenarios . . . 14 3.1 Model Setups . . . 15 3.2 Model Verification . . . 16 3.3 Model Environment . . . 20 3.4 Initial and Boundary Conditions . . . 22 3.5 Investigation on Computation Time Influences . . . 24 4 Results and Discussion . . . 30 4.1 In- and Outflow Temperature Evolution . . . 30 4.2 Energy Distribution . . . 34 4.3 Soil Heat Flux . . . 40 4.3.1 Winter in 2nd year . . . 41 4.3.2 Summer in 2nd year . . . 44 4.3.3 Winter in 30th year . . . 47 4.3.4 Summer in 30th year . . . 49 4.4 DBHE Heat Flux . . . 51 4.5 Soil Heat Flux in the Multiple DBHE Case . . . 55 4.5.1 Line Setup . . . 56 4.5.2 Square Setup . . . 61 4.6 Numerical Inaccuracies . . . 65 5 Conclusion . . . 68

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31

Wei, Chen Li, and 陳力維. "Numerical Simulation of Heat Transfer Distributions around Plate-Mounted Obstacles." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/40287857458156671754.

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碩士
國立成功大學
機械工程學系
89
Abstract This study presents the numerical Simulation of local heat transfer coefficient distributions around plate-mounted obstacles. The turbulent governing equations are solved by a Control-Volume-based finite-difference method with power-law scheme and the well know turbulence model and its associate wall function to describe the turbulent structure. The velocity and pressure terms of momentum equations are solved by SIMPLE (Semi-Implicit Method for Pressure-Linked Equation) method. An orthogonal non-uniform staggered grids are used for the establishment of mesh grids. The parameters studied include geometries（cylinder、square cylinder），the entrance flow Reynolds number （Re = 2100、3500、4200、5000）and the obstacles space（S = d , 2d , 4d）; whereas the plate-mounted obstacles characteristic length（H）and hydraulic diameter（d） is fixed at 20mm， and the working medium is air. The flow field numerical calculations indicate that the downstream attachment length becomes shorter when the space between two cylinders decreases. At the same obstacles’ number and space, it is obvious that the downstream wake region of the cylinder obstacle is smaller than that of the square, it means that the drag force of the cylinder obstacle is smaller than that of the square one. In addition，the downstream outlet velocity profile shows no obvious change with different obstacles’ number with the same Reynolds number and geometry conditions. As to the heat transfer effect，the heat transfer coefficient between two obstacles and around the second obstacle increases with increasing the obstacles’ space. As might be expected, the predicted heat transfer coefficient increasing with increasing Reynolds number from Re = 2100 to 3500 or 4200 due to the increasing of eddy intensity. Surprised, as Reynolds number Re 3500, the enhancement of heat transfer is not significant.

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32

Huang-ChiaTseng and 曾竑嘉. "Numerical and experimental study on natural convection heat transfer characteristics of plate finned tube heat exchangers with various fin shapes." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/hm65p5.

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33

Lin, Chia-Yu, and 林家瑜. "Numerical Simulation of Shallow Geothermal Energy with fractal U-type ground coil heat exchangers." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/94p7u9.

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碩士
淡江大學
航空太空工程學系碩士班
106
In the generation of ever-changing technology, the use of energy is increasing. Green buildings, smart grids, etc. are all required to use electricity. This study will focus on the analysis of the thermal performance of drilling U-tube soil heat exchangers and try to change the shapes and material of the pipes, then find out ways to increase the efficiency of the soil heat exchanger. The project will use the commercial software ANSYS Fluent to create geometric shapes and meshes, and use the Fluent solver to perform simulation calculations. Finally, the results will be imported into Tecplot for analysis and discussion. We maintain the cross-sectional area of the U-tube for fractal structures and change the material of the tube wall for better heat dissipation. According to the analysis of the simulation results, fractal star pipes have the lowest outlet temperatures in both the PVC material and the carbon steel material. And the star tube increasing the most heat transfer efficiency from the carbon steel material. The round pipe which use the carbon steel pipe, which the outlet temperature has been lower than the star tube using PVC material. So we can change the tube’s material to reduce the temperature in the tube except to the reference mentioned in the use of different backfill material.

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34

Tsa, Chia-Ju, and 蔡佳儒. "Numerical Simulation of Heat Transfer on Micro-Plate Thermal Shear Stress Sensor." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/15325857486379605972.

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碩士
國立成功大學
航空太空工程學系碩博士班
96
A numerical method is applied to simulate the fluid fields in the two -dimensional flat-plate to investigate the relationship between the wall shear stress and the heat transfer rate. The governing equations are incompressible Navier-Stokes equations with the energy equation. The artificial compressibility method is applied to solve the flow fields. In the numerical method, the third-order upwind finite volume method is used to solve the convection term, the second order central difference scheme is used to solve the diffusive term, and a two-step Runge-Kutta method is applied to time matching. For the temperature field, a finite difference method with implicit time marching is used. 　　In physical problems, first, the viscous flow past a flat plate and the viscous flow with the temperature boundary layer are simulated and verified. Finally, the flow and temperature fields of lay up a chip of heat on a flat-plate are simulated. The relationships between wall shear stress and heat-transfer rate under different velocities are investigated. About the relationships of shear stress and heat-transfer rate, it found that the wall shear stress is ratio to the cube of the heat-transfer rate for the steady-state flow. And the unsteady flow, two extra terms need to be added to the relationship.

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35

Hung, Yi-Li, and 洪一力. "Numerical Simulation of Turbulent Flow and Heat Transfer over a Blunt Flat Plate in a Channel." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/19329034642529043188.

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碩士
國立成功大學
機械工程學系碩博士班
91
This study presents the Numerical Simulation of Turbulent Flow and Heat Transfer Over a Blunt Flat Plate in a Channel, based on the experiment results of Djilali (1991) and extension of the laminar flow calculation of Yanaoka (2002) to the turbulent flow. The numerical simulation of steady, two-dimensional, turbulent flow and heat transfer is adopted to test the accuracy of the theoretical model. The turbulent-governing equations are resolved by a Control-Volume based finite-difference method with power-law scheme, and the well-known turbulence model and its associate wall function to describe the turbulent structure. The SIMPLE algorithm is adopted to solve the pressure — velocity coupling. The parameters studied include the Reynolds number (Re = 6870, 11700, 17900), Solid blockage ratio BR (BR = 0.1, 0.15) and surface temperature of blunt flat plate (Ts = 343K、353K、363K). The numerical calculations indicate that reattachment length Xr increases with an increase of Reynolds number in the range studied of Reynolds number, the error of the reattachment length is with in 10 ％ comparing with the experimental results. The flow in the recirculation region becomes three—dimensional characteristics. The predicted mean flow field is found to be in good agreement with wall grows to the downstream with an increase of Reynolds number. This vortex structure has great effects upon heat transfer.

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36

(5930039), Mario Tindaro Migliorino. "Numerical and Theoretical Modeling of Thermoacoustic Instabilities in Transcritical Fluids." Thesis, 2019.

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Enhancements of gas turbine engines efficiency are critical for the development of the next generation of clean and efficient aircraft. With the increase in combustion temperatures, cooling of the turbine blades poses one of the most important thermal management issues. The current and most adopted solution is to flow cooling air bled from the compressor through channels inside turbine blades. Fuel preheating, meant to increase combustion efficiency, could be used to cool such air flow in fuel-air heat exchangers. However, when fuel thermodynamic states approach supercritical pressures and temperatures, large amplitude oscillations have been known to occur with catastrophic hardware failures. For this reason, the use of supercritical fuels in fuel-air heat exchangers has been avoided, thereby reducing the fuel's cooling potential and the overall efficiency of the aircraft. Engine manufacturers desire a model capable of predicting the onset of such disruptive thermoacoustic oscillations. To this goal, we study theoretically and numerically transcritical thermoacoustic oscillations, i.e., thermoacoustic instabilities manifesting themselves when a fluid is heated close to its critical point, where abrupt changes of thermodynamic properties appear. Details of this work will be on the development of a transcritical thermoacoustic theory and on numerical results from linear stability analysis and high-fidelity Navier-Stokes simulations. Meeting the needs of industry and with the intent of pushing technological and scientific barriers, we propose to exploit such powerful oscillations for energy conversion through the use of the first-ever-built transcritical thermoacoustic engine.

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37

Huang, Yu-Chi, and 黃佑騏. "The Forced Convection Numerical Simulation using Finite Volume Method in the Entrance Region of a Parallel Plate Channel with Constant Heat Flux." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/40240006240377022501.

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碩士
國立臺灣海洋大學
機械與機電工程學系
103
In the numerical analysis of engineering world, there are three commonly used numerical schemes, namely, Finite-volume, finite-difference, and finite-element methods. The finite volume method (Finite Volume Method, FVM) is the most common one in the thermal-fluid field. The flow area of interest is divided into many non-overlapping control volumes in the FVM and each grid node is surrounded by a control volume. An integral process is performed for each control volume so that conservation laws (such as mass, momentum, and energy) could be satisfied within each control volume specified. Due to its conservation nature, the FVM approach is applied in the discretization and the solution of the governing equations in this thesis. The FVM with SIMPLE algorithm by Patanker is used in this thesis. Several MATLAB programs are developed to study a steady two dimensional laminar forced convection flow with constant wall heat flux in a parallel plate channel. Staggered grid configuration is used in the numerical solutions. Velocity, pressure,temperature, local Nusselt number, and friction coefficient are solved numerically. Fully developed and developed flow are both studied. Results are compared with those of analytic solutions or empirical correlations available. The numerical results of MATLAB are also compared with those of commercial code Fluent. Firstly, the applicability of staggered grid is examined. The grid size is optimized for different Reynolds numbers up to 1000. The MATLAB program developed is then run for both fully developed and uniform velocity inlet. Hydrodynamical and thermal entry length are obtained and compared with those empirical correlations in the literature. Local friction coefficient and Nusselt number are numerically calculated and compared with those analytic solutions available or Fluent results. The applicability of the MATLAB program developed in this thesis using staggered grid is well justified through above comparisons for solving this type of forced convection problem. Secondly, this thesis also compare the results of the FVM and the Fluent numerical simulation. Except in the computation time, both the FVM and the Fluent numerical simulation could achieve satisfactory results. It is proposed that different thermal boundary conditions (such as variable wall temperature, variable wall heat flux), rectangular or circular pipe, or different algorithms, such as SIMPLEC, could be studied in the future.

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38

Liang, Gu-Fan, and 梁谷帆. "Numerical Simulation Investigate of Thermal and Flow Characteristics of Plate-fin Heat Sink in Rectangular Channel Flow with installation of Horizontal Single and Twin Piezoelectric Fans." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/a2j5w6.

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碩士
國立臺北科技大學
車輛工程系所
100
The thermal and flow characteristic of plate-fan heat sink in rectangular channel flow with installation of piezoelectric fans which is investigated numerically by Fluent. Twin piezoelectric fans are installed on the flow passage of the channel. The effect of distance between end of (a), distance between tip of piezoelectric fans and front of heat sink (Lg), configuration of piezoelectric fans and rectangular channel flow of height (Hw) and fin number of heat sink (n),Twin piezoelectric fans can be in phase and out of phase. The results show that the heat transfer can be enhanced of Nusselt number by install single and twin piezoelectric fans properly. The better performance is obtained as Hw=15mm, piezoelectric fans is installed in front of heat sink position as Lg=5mm and twin piezoelectric distance between a=20mm.The efficiency of inserting piezoelectric fans in case of 10 fins is better than of 14 fins. The efficacy of inserting piezoelectric fans increases when the width of heat sink flow channel increases.

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39

Philip, Sarah Jobin. "Investigation of Heat Transfer Rates Around the Aerodynamic Cavities on a Flat Plate at Hypersonic Mach Numbers." Thesis, 2011. http://etd.iisc.ernet.in/2005/3900.

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Aerodynamic cavities are common features on hypersonic vehicles which are caused in both large and small scale features like surface defects, pitting, gap in joints etc. In the hypersonic regime, the presence of such cavities alters the flow phenomenon considerably and heating rates adjacent to the discontinuities can be greatly enhanced due to the diversion of flow. Since the 1960s, a great deal of theoretical and experimental research has been carried out on cavity flow physics and heating. However, most of the studies have been done to characterize the effect downstream and within the cavity. In the present study, a series of were carried out in the shock tunnel to investigate the heating characteristics, upstream and on the lateral side of the cavity. Heat flux measurement has been done using indigenously developed high resistance platinum thin film gauges. High resistance gauges, as contrary to the conventionally used low resistance gauges were showing good response to the extremely low heat flux values on a flat plate with sharp leading edge. The experimental measurements of heat done on a flat plate with sharp leading edge using these gauges show good match with theoretical relation by Crabtree et al. Flow visualization using high speed camera with the cavity model and shock structures visualized were similar to reported in supersonic cavity flow. This also goes to state that in spite of the fluctuating shear layer-the main feature of hypersonic flow over a cavity ,reasonable studies can be done within the short test time of shock tunnel. Numerical Simulations by solving the Navier-Stokes equation, using the commercially available CFD package FLUENT 13.0.0 has been done to complement the experimental studies.

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40

Eder, Robert. "Ein Beitrag zur Entwicklung neuartiger keramischer Wärmeübertrager für Rekuperatorbrenner: Ein Beitrag zur Entwicklung neuartiger keramischer Wärmeübertrager für Rekuperatorbrenner." Doctoral thesis, 2014. https://tubaf.qucosa.de/id/qucosa%3A22957.

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Die Effektivität keramischer Wärmeübertrager kann durch eine feinere Strukturierung der Oberflächen gesteigert werden. Dies kann durch die Integration textiler Urformen anstatt der konventionell im Schlickguss hergestellten gröberen Geometrien erfolgen. Für Strukturierungen in Form von wandgebundenen Halbbögen werden die Ergebnisse umfangreicher experimenteller und numerischer Untersuchungen zu den wärmetechnischen und strömungsmechanischen Eigenschaften vorgestellt. Basierend auf den Erkenntnissen der mittels numerischer Simulation durchgeführten Parameterstudie werden verschiedene Empfehlungen für eine optimierte Anordnung der Halbbögen gegeben, um das Verhältnis von Wärmeübergang zur Druckverlust zu verbessern. Die experimentellen Ergebnisse belegen die Richtigkeit der gewählten Randbedingungen und Vereinfachungen im numerischen Modell. Des Weiteren wurden die Strömungsstrukturen mit laserdiagnostischen Messmethoden umfangreich charakterisiert.:0 Verwendete Symbole und Formelzeichen IV 1 Einleitung 1 1.1 Motivation 1 1.2 Lösungsansatz 2 1.3 Zielstellung und Struktur der Arbeit 4 2 Stand der Technik 5 2.1 Vorwort 5 2.2 Kennzahlen zur Charakterisierung von Rekuperatoren und Wärmeüber-trageroberflächen 6 2.3 Strömungszustände und Strömungsprofile 13 2.3.1 Grenzschichten von Strömungen 13 2.3.2 Laminare Strömung zwischen zwei parallelen Platten und im Rechteckkanal 14 2.3.3 Turbulente Strömung zwischen zwei parallelen Platten 15 2.3.4 Kenngrößen, Längen- und Zeitmaße von turbulenten Strömungen 16 2.4 Umströmung von Zylindern und Wärmeübergang an Zylindern 19 2.4.1 Quer angeströmter Zylinder, Wirbelablösung und Kármánsche Wirbelstraße 19 2.4.2 Hufeisenwirbel um einen wandgebundenen Zylinder 25 2.4.3 Zylinder in Wechselwirkung miteinander und Zylinder in Tandempaarung 27 2.4.4 Quer angeströmter Zylinder parallel zu einer Wand 28 2.5 Weitere den Wärmeübergang steigernde Strukturen 29 2.5.1 Rohrbündel 30 2.5.2 Stabrippen – „pin fins“ 31 2.5.3 Zweidimensionale Rippengeometrien 33 2.5.4 Gedrehte Bleche und andere Einbauten in Rohrquerschnitten 36 2.5.5 Turbulatoren 38 2.5.6 Poröse Körper 39 2.5.7 Drähte als wärmeübergangsteigernde Struktur 40 2.6 Wärmeübertrager für Industriegasbrenner 41 3 Numerische und experimentelle Untersuchungen der neuentwickelten Wärmeübertragerstruktur 45 4 Numerische Untersuchungen bezüglich des Strömungsfelds um die Bogenstrukturen 49 4.1 Randbedingungen und Vernetzung der numerischen Simulation 49 4.2 Bemerkungen zum Turbulenzmodell 54 4.3 Validierung des numerischen Modells am leeren Kanal 59 4.4 Ergebnisse für die Grundgeometrie 63 4.5 Parameterstudie zur Anordnung und Anzahl der Bögen 70 4.5.1 Variation der Bogendichte 70 4.5.2 Variation der Anordnung der Bögen zueinander bei konstanter Bogendichte 75 4.5.3 Variation der Kanalhöhe bei konstanten Randbedingungen 78 4.5.4 Variation der Kanalhöhe bei umgekehrten Randbedingungen 80 4.5.5 Variation des Bogendurchmessers D 82 4.5.6 Bemerkung zum Anstellwinkel 83 5 Experimentelle Untersuchungen zum Wärmeübergangskoeffizienten 85 5.1 Versuchsaufbau 85 5.2 Versuchsdurchführung und Auswertung 88 5.3 Vergleich des Versuchsstandes mit Untersuchungen für Spaltströmungen 90 5.4 Referenzmessungen mit metallischen Wärmeübertragerstrukturen 93 5.4.1 Ergebnisse für die Grundgeometrie 93 5.4.2 Variation der Kanalhöhe 96 5.4.3 Variation der Kanalhöhe bei umgekehrten Randbedingungen 97 5.5 Messung mit keramischen Strukturen 98 6 Experimentelle Untersuchungen zum Strömungsverhalten 101 6.1 Versuchsaufbau 101 6.2 PIV-Messungen 104 6.2.1 Allgemeines zum Messprinzip 104 6.2.2 Messaufbau 105 6.2.3 Versuchsergebnisse 106 6.3 LDA-Messungen 111 6.3.1 Allgemeines zum Messprinzip und zur Versuchsdurchführung 111 6.3.2 Validierung des Versuchsstandes 114 6.3.3 Strömungsprofile aus der LDA-Messung 117 6.3.4 Wirbelablösung im Bogennachlauf 130 6.3.5 Skalen der Strömung 144 7 Anwendungsbeispiel: Rekuperatorbrenner 151 7.1 Brennerprototyp und Versuchsdurchführung 151 7.2 Versuchsergebnisse und Auswertung 153 8 Zusammenfassung und Ausblick 157 9 Literaturverzeichnis 161 10 Anhang 173 10.1 Messtechnik des Windkanals 173 10.2 PIV-Messtechnik 175 10.3 LDA-Messtechnik 176 10.4 Versuche mit dem Rekuperatorprototypen 177

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