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1
Mavi, Anele. "Computational analysis of viscoelastic fluid dynamics with applications to heat exchangers". Master's thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/30078.
Testo completoAbstract (sommario):
In this study, the computational analysis of a pressure driven viscoelastic fluid in a double pipe heat exchanger set-up is investigated. Non-Newtonian viscoelastic fluids in heat exchanger arrangements are encountered in various industrial applications such as power generation, refrigeration and in the food processing industry where the need for cooling and heating of liquids is required. The model problem is governed by complex, non-linear and coupled partial differential equations. These are solved using the semi-implicit finite difference method integrated with the Crank-Nicolson scheme. The pressure-velocity coupling in the momentum equations is resolved by employing the Semi-Implicit Method for Pressure Linked Equations (SIMPLE). To cope with numerical diffusion and numerical stability issues the treatment of convective terms using the upwind schemes is explored. In this work, the behaviour of viscoelastic fluids is rigorously examined by analysing the convective heat transfer from the viscoelastic core fluid of the double pipe heat exchanger to the Newtonian or viscoelastic shell fluid in the outer annulus. In addition, the effects of pressure, momentum, extra stresses, temperature, viscosity and relaxation time on the fluid temperature are investigated; both in the counter flow and parallel flow configurations. Graphical computational results are presented and discussed quantitatively and qualitatively with respect to several parameters involved in the problem.
2
Piper, Mark [Verfasser]. "Analysis of fluid dynamics and heat transfer in pillow-plate heat exchangers / Mark Piper". Paderborn : Universitätsbibliothek, 2018. http://d-nb.info/1168721474/34.
Testo completo
3
Bruzzano, Marco Anthony. "Investigation of a self compensating flow distribution system". Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/19284.
Testo completo
4
Chen, Li-Kwen. "Unsteady flow and heat transfer in periodic complex geometries for the transitional flow regime". Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Chen_09007dcc804bed71.pdf.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 12, 2008) Includes bibliographical references.
5
Walker, Patrick Gareth Chemical Engineering & Industrial Chemistry UNSW. "CFD modeling of heat exchange fouling". Awarded by:University of New South Wales. Chemical Engineering & Industrial Chemistry, 2005. http://handle.unsw.edu.au/1959.4/22385.
Testo completoAbstract (sommario):
Heat exchanger fouling is the deposition of material onto the heat transfer surface causing a reduction in thermal efficiency. A study using Computational Fluid Dynamics (CFD) was conducted to increase understanding of key aspects of fouling in desalination processes. Fouling is a complex phenomenon and therefore this numerical model was developed in stages. Each stage required a critical assessment of each fouling process in order to design physical models to describe the process???s intricate kinetic and thermodynamic behaviour. The completed physical models were incorporated into the simulations through employing extra transport equations, and coding additional subroutines depicting the behaviour of the aqueous phase involved in the fouling phenomena prominent in crystalline streams. The research objectives of creating a CFD model to predict fouling behaviour and assess the influence of key operating parameters were achieved. The completed model of the key crystallisation fouling processes monitors the temporal variation of the fouling resistance. The fouling rates predicted from these results revealed that the numerical model satisfactorily reproduced the phenomenon observed experimentally. Inspection of the CFD results at a local level indicated that the interface temperature was the most influential operating parameter. The research also examined the likelihood that the crystallisation and particulate fouling mechanisms coexist. It was found that the distribution of velocity increased the likelihood of the particulate phase forming within the boundary layer, thus emphasizing the importance of differentiating between behaviour within the bulk and the boundary layer. These numerical results also implied that the probability of this composite fouling was greater in turbulent flow. Finally, supersaturation was confirmed as the key parameter when precipitation occurred within the bulk/boundary layer. This investigation demonstrated the advantages of using CFD to assess heat exchanger fouling. It produced additional physical models which when incorporated into the CFD code adequately modeled key aspects of the crystallisation and particulate fouling mechanisms. These innovative modelling ideas should encourage extensive use of CFD in future fouling investigations. It is recommended that further work include detailed experimental data to assist in defining the key kinetic and thermodynamic parameters to extend the scope of the required physical models.
6
Ozden, Ender. "Detailed Design Of Shell-and-tube Heat Exchangers Using Cfd". Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608752/index.pdf.
Testo completoAbstract (sommario):
Traditionally Shell-and-tube heat exchangers are designed using correlation based approaches like Kern method and Bell-Delaware method. With the advances in Computational Fluid Dynamics (CFD) software, it is now possible to design small heat exchangers using CFD. In this thesis, shell-and-tube heat exchangers are modeled and numerically analyzed using a commercial finite volume package. The modeled heat exchangers are relatively small, have single shell and tube passes. The leakage effects are not taken into account in the design process. Therefore, there is no leakage from baffle orifices and no gap between baffles and the shell. This study is focused on shell side flow phenomena. First, only shell side is modeled and shell side heat transfer and flow characteristics are analyzed with a series of CFD simulations. Various turbulence models are tried for the first and second order discretization schemes using different mesh densities. CFD predictions of the shell side pressure drop and the heat transfer coefficient are obtained and compared with correlation based method results. After selecting the best modeling approach, the sensitivity of the results to the flow rate, the baffle spacing and baffle cut height are investigated. Then, a simple double pipe heat exchanger is modeled. For the double pipe heat exchanger, both the shell (annulus) side and the tube side are modeled. Last, analyses are performed for a full shell-and-tube heat exchanger model. For that last model, a small laminar educational heat exchanger setup is used. The results are compared with the available experimental results obtained from the setup. Overall, it is observed that the flow and temperature fields obtained from CFD simulations can provide valuable information about the parts of the heat exchanger design that need improvement. The correlation based approaches may indicate the existence of a weakness in design, but CFD simulations can also pin point the source and the location of the weakness.
7
Peronski, Lukasz. "Application of computational fluid dynamics in the design of heat exchangers for domestic central heating boilers". Thesis, University of Leeds, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612612.
Testo completoAbstract (sommario):
The aim of this study is to investigate the possible use of commercial Computational Fluid Dynamics (CFD) software in the design process of a heat exchanger for a domestic gas boiler. Fluid flow and heat transfer CFD simulations have been performed and validated. In general, a good agreement between the CFD simulations and the experimental results was observed. The porous media approach was used for approximating the water flow resistance characteristics in the sections of the heat exchanger in the flow distribution problems. This was in cases in which the direct CFD simulations of the water flow through these sections of the heat exchanger would require very large numerical meshes and computational resources. Also a method for designing a water flow distributor for the sectional parallel now heat exchanger is proposed. The method is based on Bernoulli's equation with the flow resistance characteristics of a single section of the heat exchanger gained from the CFD simulation of the water now through a single section of this heat exchanger. The performed CFD analyses provide very useful information with regards to the operational parameters and conditions in the heat exchanger under investigation, which would otherwise be very difficult. if not impossible, to obtain. Despite the great potential usefulness of the CFD simulation In the design process of heat exchangers, it is still not always considered a clear choice for use in the boiler industry, in order to aid the design process of heat exchangers for domestic central heating boilers. This is due to the relatively high cost of the CFD analyses and the fact that the boiler industry traditionally relies on design procedures based primarily on experimental techniques
8
Vaitekunas, David A. "A generic dynamic model for crossflow heat exchangers with one fluid mixed /". Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59591.
Testo completoAbstract (sommario):
This thesis presents a generic model for crossflow heat exchangers with one fluid mixed, suitable for dynamic process simulation. A finite difference technique is used to formulate the coupled flow and energy solutions for arbitrary transients in pressure drop and temperature.The solution algorithms are presented in two forms: one-way dependence and two-way dependence: for the constant and variable property version of the model, respectively. Variable time step algorithms are also developed to predict the optimal time step for the finite difference solution. The first one uses a first order predictor method and the second one uses a combined first/second order predictor method.
Finally, the generic model is configured to model the economizer and tubular air preheater of an existing boiler. Steady-state tests validate the numerical solution against available theoretical relations and transient tests investigate the parameters in the solution and time step algorithms to determine their effect on simulation speed and accuracy.
9
Dimas, Sotirios. "A CFD analysis of the performance of pin-fin laminar flow micro/meso scale heat exchangers". Thesis, Monterey, Calif. : Naval Postgraduate School, 2005. http://bosun.nps.edu/uhtbin/hyperion-image.exe/05Sep%5FDimas.pdf.
Testo completoAbstract (sommario):
Thesis (Mechanical Engineer and M.S. in Mechanical Engineering)--Naval Postgraduate School, September 2005.Thesis Advisor(s): Gopinath, Ashok ; Sinibaldi, Jose O. "September 2005." Description based on title screen as viewed on March 12, 2008. Includes bibliographical references (p. 85-87). Also available in print.
10
Taylor, Creed. "Measurement of Finned-Tube Heat Exchanger Performance". Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4890.
Testo completoAbstract (sommario):
Finned-tube heat exchangers are predominantly used in space conditioning systems, as well as other applications requiring heat exchange between two fluids. One important widespread use is in residential air conditioning systems. These residential cooling systems influence the peak demand on the U.S. national electrical system, which occurs on the hot summer afternoons, and thereby sets the requirement for the expensive infrastructure requirement of the nations power plant and electrical distribution system. In addition to this peak demand, these residential air conditioners are major energy users that dominate residential electrical costs and environmental impact.
The design of finned-tube heat exchangers requires the selection of over a dozen design parameters by the designer. The refrigerant side flow and heat transfer characteristics inside the tubes have been thoroughly studied. However, the air side flow around the tube bundle and through the fin gaps is much more complex and depends on over a dozen design parameters. Therefore, experimental measurement of the air side performance is needed.
First this study built an experimental system and developed methodology for measuring the air side heat transfer and pressure drop characteristics of fin tube heat exchangers. This capability was then used to continue the goal of expanding and clarifying the present knowledge and understanding of air side performance to enable the air conditioner system designer in verifying an optimum fin tube condenser design.
In this study eight fin tube heat exchangers were tested over an air flow face velocity range of 5 ?? ft/s (675-1600cfm). The raw data were reduced to the desired heat transfer and friction data, j and f factors. This reduced heat transfer and friction data was plotted versus Reynolds number and compared. The effect of fin spacing, the number of rows and fin enhancement were all investigated. The heat transfer and friction data were also plotted and compared with various correlations available from open literature. The overall accuracy of each correlation to predict experimental data was calculated. Correlations by C.C. Wang (1998b, 1999) showed the best agreement with the data. Wangs correlations (1998b, 1999) were modified to fit the current studys data.
11
Keltner, Noelle Joy. "Study of PocoFoam (TM) as a heat exchanger element in cryogenic applications". Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51774.
Testo completoAbstract (sommario):
Superconductors present great potential for weight reduction and increased power delivery when compared to traditional copper power delivery systems, but current systems require cryogenic cooling systems. Traditional superconductor cooling systems consist of helium cooled by helical heat exchangers made of Oxygen Free High thermal Conductivity (OFHC) copper tube. The helium is cooled by bulky heat exchangers consisting of OFHC copper coils wrapped around a cryogenic cooler heat sink for heat transfer into the working fluid. Metal foams have recently been studied in a variety of heat transfer applications, and could greatly reduce the weight of heat exchanger modules in superconductor cooling systems while simultaneously providing increased heat transfer effectiveness. Aluminum and Copper foams have been available for several years, but more recently, graphite foams, such as PocoFoam™, have been developed which have particularly good heat transfer characteristics. Using Computational Fluid Dynamics (CFD) to model a cryogenic heat exchanger application, this study examines the effectiveness and pressure drop of several metal foam heat exchangers, and compares their performance with the traditional helical coil design for superconductor cooling applications. The CFD simulation results show that a heat exchanger with the same heat sink contact area as existing helical heat exchangers weighs up to 95 percent less and can be up to 25 percent more effective, depending on system conditions such as pressure, cryogenic cooler temperature and helium inlet temperature. Aluminum and copper foam heat exchangers had comparable weight to the PocoFoam heat exchanger, but were significantly less effective than the helical or PocoFoam heat exchanger models.
12
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.
Testo completoAbstract (sommario):
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.
13
Murphy, Daniel Lawrence. "Condensation heat transfer and pressure drop of propane in vertical minichannels". Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51802.
Testo completoAbstract (sommario):
Heat transfer and pressure drop during condensation of propane flowing through minichannels is investigated in this study. Studies of condensation of hydrocarbons are important for applications in the petrochemical industry. Insights into the mechanisms of propane condensation are required for accurate design of heat transfer equipment for use in hydrocarbon processing. At present, there is very little research on vertical condensation, especially of hydrocarbons, for the tube sizes and flow conditions of interest to the present study. An experimental facility was designed and fabricated to measure the frictional pressure drop and heat transfer coefficients during condensation of propane in plain tubes with an inner diameter of 1.93 mm. Measurements were taken across the vapor-liquid dome in nominal quality increments of 0.25 for two saturation temperatures (47°C and 74°C) and four mass flux conditions (75 – 150 kg m‾² s‾¹). The data were compared to the predictions of relevant correlations in the literature. The data from this study were also used to develop models for the frictional pressure drop and heat transfer coefficient based on the measurements and the underlying condensation mechanisms. These results and the corresponding correlations contribute to the understanding of condensation of hydrocarbons in vertical minichannels.
14
Wilson, Scott E. "Investigation of Copper Foam Coldplates as a High Heat Flux Electronics Cooling Solution". Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6944.
Testo completoAbstract (sommario):
Compact heat exchangers such as porous foam coldplates have great potential as a high heat flux cooling solution for electronics due to their large surface area to volume ratio and tortuous coolant path. The focus of this work was the development of unit cell modeling techniques for predicting the performance of coldplates with porous foam in the coolant path.
Multiple computational fluid dynamics (CFD) models which predict porous foam coldplate pressure drop and heat transfer performance were constructed and compared to gain insight into how to best translate the foam microstructure into unit cell model geometry. Unit cell modeling in this study was realized by applying periodic boundary conditions to the coolant entrance and exit faces of a representative unit cell. A parametric study was also undertaken which evaluated dissimilar geometry translation recommendations from the literature. The use of an effective thermal conductivity for a representative orthogonal lattice of rectangular ligaments was compared to a porosity-matching technique of a similar lattice. Model accuracy was evaluated using experimental test data collected from a porous copper foam coldplate using deionized water as coolant. The compact heat exchanger testing facility which was designed and constructed for this investigation was shown to be capable of performing tests with coolant flow rates up to 300 mL/min and heat fluxes up to 290 W/cm2. The greatest technical challenge of the testing facility design proved to be the method of applying the heat flux across a 1 cm2 contact area. Based on the computational modeling results and experimental test data, porous foam modeling recommendations and porous foam coldplate design suggestions were generated.
15
Shanmugam, Dinesh Kumar, e dshanmugam@swin edu au. "Development of ice particle production system for ice jet process". Swinburne University of Technology. Industrial Research Institute Swinburne, 2005. http://adt.lib.swin.edu.au./public/adt-VSWT20050805.145343.
Testo completoAbstract (sommario):
This thesis presents a comprehensive study of the ice particle production process through experimentation and numerical methods using computational fluid dynamics (CFD) that can be used to produce ice particles with controlled temperature and hardness for use in ice jet (IJ) process for industrial applications. The analytical and numerical modeling for the heat exchanger system are developed that could predict the heat, mass and momentum exchange between the cold gas and water droplets. Further, the feasibility study of the deployment of ice particles produced from the ice jet system for possible cleaning and blasting applications are analyzed numerically. Although the use of Abrasive Water Jet (AWJ) technology in cutting, cleaning, machining and surface processing is a very successful industrial process, a considerable amount of secondary particle waste and contamination impingement by abrasive materials has been an important issue in AWJ process. Some alternate cryogenic jet methods involving vanishing abrasive materials, such as plain liquid nitrogen or carbon dioxide have been tried for these applications, but they also suffer from certain drawbacks relating to the quality, safety, process control and materials handling. The use of ice jet process involving minute ice particles has received relatively little attention in industrial applications. Some researches have concentrated on the studies of effects of Ice Jet outlet parameters of the nozzle and focus tube for machining soft and brittle materials. Most of the work in this area is qualitative and researchers have paid a cursory attention to the ice particles temperature and the efficiency of production of these particles. An extensive investigation to gain insight knowledge into the formulation of ice formation process parameters is required in arriving at a deeper understanding of the entire ice jet process for production application. Experimental investigations were focussed on the measurement of ice particle temperature, phase transitions, ice particle diameter, coalescence and hardness test. The change in ice particle diameter from the inlet conditions to the exit point of the heat exchanger wasinvestigated using the experimental results. These observations were extended to numerical analysis of temperature variations of ice particles at different planes inside the custom built heat exchanger. The numerical predictions were carried out with the aid of visualization studies and temperature measurement results from experiments. The numerical models were further analysed to find out the behaviour of ice particles in the transportation stage, the mixing chamber of the nozzle and focus tube. This was done to find out whether the methodology used in this research is feasible and if it can be used in applications such as cleaning, blasting, drilling and perhaps cutting. The results of the empirical studies show that ice particles of desired temperature and hardness could be produced successfully with the current novel design of the heat exchanger. At the optimum parameters, ice particles could be produced below -60�C, with hardness of particles comparable to gypsum (Moh�s hardness of 1.5 to 3). The visualization studies of the process assisted in observation of the phases of ice at various points along the heat exchanger. The results of numerical analysis were found to agree well with the experiments and were supported by the statistical model assessments. Numerical analyses also show the survival of ice particles at the nozzle exit even with high-pressure, high-velocity water/air mixture.
16
Bourke, Jason Michael. "Implications of Airflow Dynamics and Soft-Tissue Reconstructions for the Heat Exchange Potential of Dinosaur Nasal Passages". Ohio University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1448453168.
Testo completo
17
Alghamdi, Jamal Khaled. "CFD Simulation Methodology for Ground-Coupled Ventilation System". Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35736.
Testo completoAbstract (sommario):
In the past two decades, a growing interest in alternative energy resources as a
replacement to the non-renewable resources used now days. These alternatives include
geothermal energy which can be used to generate power and reduce the demands on
energy used to heat and cool buildings. Ground-coupled ventilation system is one of the
many applications of the geothermal energy that have a lot of attention in the early 80â s
and 90â s but all designs of the system where based on single case situations. On the other
hand, computational fluid dynamics tools are used to simulate heat and fluid flow in any
real life situation. They start to develop rapidly with the fast development of computers
and processors. These tools provide a great opportunity to simulate and predict the
outcome of most problems with minimum loss and better way to develop new designs.
By using these CFD tools in GCV systems designing procedure, energy can be conserved
and designs going to be improved.
The main objective of this study is to find and develop a CFD modeling strategy
for GCV systems. To accomplish this objective, a case study must be selected, a proper
CFD tool chosen, modeling and meshing method determined, and finally running
simulations and analyzing results. All factors that affect the performance of GCV should
be taken under consideration in that process such as soil, backfill, and pipes thermal
properties. Multiple methods of simulation were proposed and compared to determine the
best modeling approach.Master of Science
18
Symes, Richard. "Design and modelling of a heat recovery cycle and turbine for a low temperature hydrogen fuel cell". Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/213827/1/Richard_Symes_Thesis.pdf.
Testo completoAbstract (sommario):
This thesis examines the viability of waste heat recovery from a small scale, low temperature hydrogen fuel cell, to generate additional power using a thermodynamic cycle and micro-turbine. It investigates the optimal fluid selection for an organic Rankine cycle and models a radial inflow turbine to generate power from the cycle, which was able to improve the efficiency of the fuel cell by 5%. This work optimises the cycle and turbine designs to match the operating conditions and achieve the highest efficiency and validates the result using 3D fluid simulations.
19
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.
Testo completoAbstract (sommario):
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.
20
Beale, Steven Brydon. "Fluid flow and heat transfer in tube banks". Thesis, Imperial College London, 1992. http://hdl.handle.net/10044/1/8103.
Testo completo
21
Lowdon, A. "Flow induced vibrations of tube arrays in heat exchangers". Thesis, University of Newcastle Upon Tyne, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234773.
Testo completo
22
Hassan, Marwan. "Dynamics of loosely supported heat exchanger tubes /". *McMaster only, 2001.
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23
Gerova, Klementina. "Thermo-fluid effects associated with modelling subscale automotive heat exchangers". Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/9875.
Testo completoAbstract (sommario):
Automotive components are tested extensively in wind tunnels by automotive manufacturers and race teams. This is usually achieved using an accurate scale model representation of the component within the wind tunnel. Automotive heat exchangers, however, are comprised of numerous intricate geometries and are therefore impractical to produce at model scale. Instead they are simply modelled as pressure drops, achieved using a thin mesh or honeycomb of known porosity. Most commercial computational fluid dynamics solvers ignore the geometry of the heat exchanger and instead model it as a discontinuity with a known pressure drop and heat transfer. The pressure drop across an automotive heat exchanger, however, was found to vary with both the coolant temperature and the angle of inclination of the heat exchanger. This thesis initially presents a relationship between the pressure drop coefficient and the inclination angle for varying media porosities. Mathematical relationships for inclination angles of 0°, 15°, 30° and 45°. were derived relating this pressure drop coefficient to the porosity of the media. Weighted least squares is proposed over ordinary least squares when obtaining the Forchheimer equation coefficients from experimental measurements. Investigation extends into the thermo-fluid effects on a full scale automotive heat exchanger when inclined at 0 °, 15°, 30° and 45°. It was found, depending on the angle, that there was a difference in the pressure drop of up to 10% between the unheated and heated (100 C) heat exchanger. Based on the proposed mathematical relationship, this correlated to a 4% decrease in porosity in order to accurately model the automotive heat exchanger at subscale. The thesis concludes with experimental and numerical investigation into the heat transfer on a hydrodynamically and thermally developing ow within a radiator channel. Laser doppler anemometry measurements recorded a 1.5% increase in the centreline velocity compared to 0.8% obtained from numerical simulation.
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Van, der Westhuizen Nicolé. "Gradient calculations of non-orthogonal meshes in the finite volume method / N. van der Westhuizen". Thesis, North-West University, 2013. http://hdl.handle.net/10394/9722.
Testo completoAbstract (sommario):
The handling of gradient calculations on non-orthogonal meshes in the Finite Volume Method (FVM) is important in the modelling of complex geometries, since different implementation methods have an influence on the accuracy and the stability of the solution. The application in the current study is the numerical solution of heat conduction in a complex geometry. It finds relevance in many engineering applications such as the Micro-Channel Heat Exchanger (MCHE) that acts as a recuperator in a High Temperature Reactor (HTR) power generation cycle. A program based on the FVM was developed in Excel for the solution of the diffusion equation on a non-orthogonal mesh. A test case of heat conduction in a rectangular block, meshed with a tetrahedral mesh, was solved with the Excel code. The same test case was solved with OpenFOAM. The results of the two codes were compared. Small differences were found and their origins were traced to slightly different implementation methods. Knowledge of the differences in implementation between the two codes resulted in a better understanding of the aspects that influenced accuracy and stability. Computations on meshes with the presence of mesh skewness and non-orthogonal mesh lines at boundaries were performed and an accompanying decrease in accuracy was observed. The results showed that the standard FVM as implemented in the Excel code and in OpenFOAM will need advanced methods to compensate for mesh skewness and non-orthogonality found at boundaries. During the study, a deeper knowledge and understanding was gained of the challenge of obtaining accurate solutions of heat conduction on non-orthogonal meshes. This knowledge may lead to the overall improvement of the simulation of heat transfer models in general and for the MCHE specifically.Thesis (MIng (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2013.
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Sarde, Deepti R. "Thermal/fluid characteristics of elliptic cross-section filament box-lattices as heat exchanger surfaces". abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1436470.
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El-Sherif, K. M. "Axial heat transfer in a packed bed heat exchangers using fluid near its critical point". Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374464.
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Cole, Brian D. "Transient performance of parallel-flow and cross-flow direct transfer type heat exchangers with a step temperature change on the minimum capacity rate fluid stream. /". Online version of thesis, 1995. http://hdl.handle.net/1850/11924.
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Van, Zyl Marilize. "Prediction of flow-induced vibration in shell-and-tube heat exchangers". Diss., University of Pretoria, 2004. http://hdl.handle.net/2263/28055.
Testo completoAbstract (sommario):
Please read the abstract (Summary) in the 00front part of this documentDissertation (M Eng (Mechanical Engineering))--University of Pretoria, 2006.
Mechanical and Aeronautical Engineering
unrestricted
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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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Perry, Jeffrey L. "Fouling in silicon microchannel designs used for IC chip cooling and its mitigation /". Online version of thesis, 2008. http://hdl.handle.net/1850/6211.
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Nabati, Hamid. "Numerical Analysis of Heat Transfer and Fluid Flow in Heat Exchangers with Emphasis on Pin Fin Technology". Doctoral thesis, Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-14409.
Testo completoAbstract (sommario):
One of the most important industrial processes is heat transfer, carried out by heat exchangers in single and multiphase flow applications. Despite the existence of well-developed theoretical models for different heat transfer mechanisms, the expanding need for industrial applications requiring the design and optimization of heat exchangers, has created a solid demand for experimental work and effort. This thesis concerns the use of numerical approaches to analyze and optimize heat transfer and fluid flow in power generation industry, with emphasis on pin fin technology. This research begins with a review on heat transfer characteristics in surfaces with pin fins. Different pin fins shapes with various flow boundaries were studied, and thermal and hydraulic performances were investigated. The impact of parameters such as inlet boundary conditions, pin fin shapes, and duct cross-section characteristics on both flow and heat transfer were examined. Two important applications in power generation industry were considered for this study: power transformer cooling, and condenser for CO2 capturing application in oxy-fuel power plants. Available experimental data and correlations in the literature have been used for models validation. For each case, a model based on current configuration was built and verified, and was then used for optimization and new design suggestions. All numerical modeling was performed using commercial CFD software. A basic condenser design was suggested and examined, supplemented by the use of pin fin technology to influence the condensation rate of water vapour from a CO2/H2O flue gas flow. Moreover an extensive review of numerical modeling approaches concerning this condensation issue was conducted and presented. The analysis results show that the drop-shaped pin fin configuration has heat transfer rates approximating those of the circular pin configuration, and the drop-shaped pressure losses are less than one third those of the circular. Results for the power transformer cooling system show those geometrical defects in the existing system are easily found using modeling. Also, it was found that the installation of pin fins in an internal cooling passage can have the same effect as doubling the radiator’s height, which means a more compact cooling system could be designed. Results show that a condensation model based on boundary layer theory gives a close value to experimental correlations. Considering a constant wall temperature, any increase in CO2 concentration results in lower heat transfer coefficients. This is a subsequence of increased diffusivity resistance between combustion gas and condensing boundary layer. Also it was shown that sensitivity of heat transfer rate to inlet temperatures and velocity values decreased when these parameters increased. The application of numerical methods concerning the condensation process for CO2 capturing required significant effort and running time as the complexity of multiphase flow was involved. Also data validation for the CO2/H2O condenser was challenging since this is quite a new application and less experimental data (and theoretical correlations) exist. However, it is shown that models based on numerical approaches are capable of predicting trends in the condensation process as well as the effect of the non-condensable CO2 presence in the flue gas. The resulting data, conclusions, applied methodology can be applied to the design and optimization of similar industrial heat exchangers, such as oil coolers which are currently working at low efficiency levels. It can also be used in the design of electronic components, cooling of turbine blades, or in other design applications requiring high heat flux dissipation. Finally, the finding on water vapour condensation from a binary mixture gas can be referenced for further research and development in this field.
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Muzychka, Yuri Stephan. "Analytical and experimental study of fluid friction and heat transfer in low Reynolds number flow heat exchangers". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0015/NQ38258.pdf.
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袁大偉 e Da-wai David Yuen. "Dynamic analysis of triple heat exchangers by the finite element method". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1989. http://hub.hku.hk/bib/B31209051.
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Li, Zhongfu. "Investigation on a solar powered absorption air-conditioning system with partitioned hot water storage tank /". Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk:8888/cgi-bin/hkuto%5Ftoc%5Fpdf?B23295144.
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Balantrapu, Kiran. "Thermal/fluid characteristics of cylindrical-filament open-cell box-lattice structures as heat exchanger surfaces". abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1433298.
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Baldwin, Stephen. "A study of heat and fluid flow phenomena on the gas side of circular-tube plate-fin heat exchangers". Thesis, Coventry University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329038.
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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.
Testo completoAbstract (sommario):
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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李仲付 e Zhongfu Li. "Investigation on a solar powered absorption air-conditioning system with partitioned hot water storage tank". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31242030.
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Rauthan, Kanishk. "Investigation of surface textures on thermal and pressure drop performance of plate-fin heat exchangers". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2022. https://ro.ecu.edu.au/theses/2597.
Testo completoAbstract (sommario):
Firstly, I would like to show my sincere gratitude to my supervisors Dr. Ferdinando Guzzomi and Dr. Ana Vafadar for their immeasurable guidance and support throughout the duration of the project. Dr. Guzzomi and Dr. Vafadar have always had an open-door policy for me which helped me accomplish my goals on or before the deadlines.
I highly appreciate Dr. Ferdinando Guzzomi for listening to and putting up with my ridiculous ideas and vision towards the project and pointing me in the right course of direction. I would like to thank Dr. Guzzomi for giving me the creative freedom and putting his trust on me with the project, allowing me to think outside the box and making my ideas a reality.
I would also like to show my heartfelt appreciation towards Dr. Ana Vafadar for listening to my confusion every week and to draw meaning out of my words. Your feedback along with the constructive criticism has been highly valuable throughout this journey and has kept me in check. Your constant support and faith in me have allowed me to finish the project on time and with significant contributions to the area of my research.
Dr. Kevin Hayward has also played a key role in the completion of this project. His feedback and suggestions towards my manuscripts and reports and numerous data analysis techniques have been critical in making this work presentable.
From the bottom of my heart, I would like to say a big thank you to Mr. Adrian Davis, Dr. Michael Stein and Joshua Bolton for their technical and literacy support throughout my bachelors and master’s project. Without your guidance and wisdom, none of this would have been possible.
A special thanks goes to my fellow researchers Aakash Shaun Hurry and Prashan Perera for all the cake and coffee I’ve had in the past 2 years and for the lovely discussions we had regarding our projects. I highly appreciate their immense support through times of doubt and uncertainty. I would also like to thank the ECU-Motorsports team specially Adam Honeycombe and Mario Leone for allowing me to use the facilities within the motorsports workshop and to be a part of the team and experience the Aus-West competition. I will cherish these memories and friendships forever.
Last but not the least, my biggest gratitude goes towards my uncle and aunt for their unconditional love and support throughout my bachelors and masters. I would not be where I am without their constant support. I would also like to thank my family and friends back in India who have helped me through this journey and allowed me to accomplish my goals.
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Soria, Guerrero Manel. "Parallel multigrid algorithms for computational fluid dynamics and heat transfer". Doctoral thesis, Universitat Politècnica de Catalunya, 2000. http://hdl.handle.net/10803/6678.
Testo completoAbstract (sommario):
The main purpose of the dissertation is to contribute to the development of numerical techniques for computational heat transfer and fluid flow, suitable for low cost (loosely coupled) parallel computers. It is focused on implicit integration schemes, using finite control volumes with multigrid (MG) algorithms.Natural convection in closed cavities is used as a problem model to introduce different aspects related with the integration of the incompressible Navier-Stokes equations, such as the solution of the pressure correction (or similar) equations that is the bottleneck of the algorithms for parallel computers. The main goal of the dissertation has been to develop new algorithms to advance in the solution of this problem rather than to implement a complete parallel CFD code.
An overview of different sequential multigrid algorithms is presented, pointing out the difference between geometric and algebraic multigrid. A detailed description of segregated ACM is given. The direct simulation of a turbulent natural convection flow is presented as an application example. A short description of the coupled ACM variant is given.
Background information of parallel computing technology is provided and the the key aspects for its efficient use in CFD are discussed. The limitations of low cost, loosely coupled cost parallel computers (high latency and low bandwidth) are introduced. An overview of different control-volume based PCFD and linear equation solvers is done. As an example, a code to solve reactive flows using Schwartz Alternating Method that runs particularly well on Beowulf clusters is given.
Different alternatives for latency-tolerant parallel multigrid are examined, mainly the DDV cycle proposed by Brandt and Diskin in a theoretical paper. One of its main features is that, supressing pre-smoothing, it allows to reduce the each-to-neighbours communications to one per MG iteration. In the dissertation, the cycle is extended to two-dimensional domain decompositions. The effect of each of its features is separately analyzed, concluding that the use of a direct solver for the coarsest level and the overlapping areas are important aspects. The conclusion is not so clear respect to the suppression of the pre-smoothing iterations.
A very efficient direct method to solve the coarser MG level is needed for efficient parallel MG. In this work, variant of the Schur complement algorithm, specific for relatively small, constant matrices has been developed. It is based on the implicit solution of the interfaces of the processors subdomains. In the implementation proposed in this work, a parallel evaluation and storage of the inverse of the interface matrix is used. The inner nodes of each domain are also solved with a direct algorithm. The resulting algorithm, after a pre-processing stage, allows a very efficient solution of pressure correction equations of incompressible flows in loosely coupled parallel computers.
Finally, all the elements presented in the work are combined in the DDACM algorithm, an algebraic MG equivalent to the DDV cycle, that is as a combination of a parallel ACM algorithm with BILU smoothing and a specific version of the Schur complement direct solver. It can be treated as a black-box linear solver and tailored to different parallel architectures.
The parallel algorithms analysed (different variants of V cycle and DDV) and developed in the work (a specific version of the Schur complement algorithm and the DDACM multigrid algorithm) are benchmarked using a cluster of 16 PCs with a switched 100 Mbits/s network.
The general conclusion is that the algorithms developed are suitable options to solve the pressure correction equation, that is the main bottleneck for the solution of implicit flows on loosely coupled parallel computers.
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Lyra, P. R. M. "Unstructured grid adaptive algorithms for fluid dynamics and heat conduction". Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637967.
Testo completoAbstract (sommario):
This work is concerned with the development of reliable and versatile computational tools for the numerical simulation of two-dimensional heat conduction and incompressible and compressible laminar fluid flow problems. Issues related to adaptive techniques, discretisation methodologies (upwind or centred type) and the design of high-resolution shock-capturing schemes are investigated in this thesis. Three distinct research works have been pursued here. In the first work, attention is focused on the construction of an adaptive finite element procedure with mesh refinement, by mesh enrichment, in time and space, and with automatic time stepping for the heat conduction problem in a stationary medium. The Galerkin finite element method and the Euler-backward time marching scheme are used as the basis to obtain the steady-state and transient approximate solutions. Particular emphasis concentrates on the design of the adaptive strategy and the combined influence of time and spatial adaptation. The second task is concerned with the derivation of adaptive remeshing strategies for both steady and unsteady solution of the incompressible Navier-Stokes equations in primitive variables. A Petrov-Galerkin formulation, which automatically introduces streamline upwinding and allows equal order interpolation for all variables, combined with either an explicit or implicit time integration represents the general discretisation methodologies adopted. The adaptive redefinition of the mesh, the error estimate and specific features, such as the presence of singularities on the solution and accumulation of interpolation errors inherent to a transient remeshing, are carefully analysed with some remedies proposed to deal with such difficulties. In the final part of the thesis, the most relevant mathematical-physical properties of the first order hyperbolic model equations are discussed. The utilisation of upstream or centred discretisation and several ways to produce high-resolution schemes to deal with this class of problems are described and compared for one-dimensional test cases. With regard to upwind discretisation techniques, the most popular flux difference splitting, flux vector splitting and some recently proposed hybrid splitting methodologies are considered.
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Iverson, Jared M. "Computational fluid dynamics validation of buoyant turbulent flow heat transfer". Thesis, Utah State University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1550153.
Testo completoAbstract (sommario):
Computational fluid dynamics (CFD) is commonly implemented in industry to perform fluid-flow and heat-transfer analysis and design. Turbulence model studies in literature show that fluid flows influenced by buoyancy still pose a significant challenge to modeling. The Experimental Fluid Dynamics Laboratory at Utah State University constructed a rotatable buoyancy wind tunnel to perform particle image velocimetry experiments for the validation of CFD turbulence models pertaining to buoyant heat-transfer flows. This study validated RANS turbulence models implemented within the general purpose CFD software STAR-CCM+, including the k – ε models: realizable two-layer, standard two-layer, standard low-Re, v2 – f, the k- ω models from Wilcox and Menter, and the Reynolds stress transport and Spalart - Allmaras models. The turbulence models were validated against experimental heat flux and velocity data in mixed and forced convection flows at mixed convection ratios in the range of 0.1 ≤ Gr/Re2 ≤ 0.8. The k- εε standard low-Re turbulence model was found most capable overall of predicting the fluid velocity and heat flux of the mixed convection flows, while mixed results were obtained for forced convection.
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Iverson, Jared M. "Computational Fluid Dynamics Validation of Buoyant Turbulent Flow Heat Transfer". DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/2025.
Testo completoAbstract (sommario):
Computational fluid dynamics (CFD) is commonly used to visualize and understand complicated fluid flow and heat transfer in many industries. It is imperative to validate the CFD computer models in order to avoid costly design choices where experimentation cannot be used to ratify the predictions of computer models. Assessments of CFD computer models in the literature conclude that significant errors occur in computer model predictions of fluid flow influenced by buoyancy forces.
The Experimental Fluid Dynamics Laboratory at Utah State University constructed a wind tunnel with which to perform experiments on buoyancy induced fluid flow. The experiments measured the heat transfer and fluid velocity occurring in the buoyant flows to be used to validate computer models. Additional experimental measurements at the inlet and around the walls from each experiment allowed the computer models to simulate the fluid flow with realistic boundary conditions.For this study, four experiments were performed, including two cases where the buoy- ancy influence was significant, and two where it was not. For each set of two cases, one experiment was performed where the heat transfer occurred from a wall of the wind tunnel held at constant temperature and in the other experiment the wall temperature fluctuated axially.
This study used the experimental data to validate computer models available in the general purpose CFD software STAR-CCM+, including the k − ε models: realizable two- layer, standard two-layer, standard low-Re, v2 − f, the k − ω models from Wilcox and Menter, and the Reynolds stress transport and Spalart–Allmaras models. The k − ε stan- dard low-Re model was found most capable overall of predicting the fluid flow and heat transfer that occurred in the flows where the buoyancy influence was significant. For the experimental cases where the buoyancy influence was less significant, the validation results were inconsistent.
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Mastrippolito, Franck. "Optimisation de forme numérique de problèmes multiphysiques et multiéchelles : application aux échangeurs de chaleur". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC043/document.
Testo completoAbstract (sommario):
Les échangeurs de chaleur sont utilisés dans de nombreux secteurs industriels. L'optimisation de leurs performances est donc de première importance pour réduire la consommation énergétique. Le comportement d'un échangeur est intrinsèquement multiéchelle : l'échelle locale de l'intensification des phénomènes de transfert thermique côtoie une échelle plus globale où interviennent des phénomènes de distribution de débit. Un échangeur de chaleur est également le siège de différents phénomènes physiques, tels que la mécanique des fluides, la thermique et l'encrassement. Les présents travaux proposent une méthode d'optimisation multiobjectif de la forme des échangeurs, robuste, pouvant traiter les aspects multiéchelles et multiphysiques et applicable dans un contexte industriel. Les performances de l'échangeur sont évaluées par des simulations de mécanique des fluides numérique (CFD) et par des méthodes globales (є-NUT). Suite à une étude bibliographique, une méthode de métamodélisation par krigeage associée à un algorithme génétique ont été retenus. Des méthodes de visualisation adaptées (clustering et Self-Organizing Maps) sont utilisées pour analyser les résultats. Le métamodèle permet d'approcher la réponse d'un simulateur (CFD) et d'en fournir une prédiction dont l'interrogation est peu onéreuse. Le krigeage permet de prendre en compte une discontinuité et des perturbations de la réponse du simulateur par l'ajout d'un effet de pépite. Il permet également l'utilisation de stratégies d'enrichissement construisant des approximations précises à moindre coût. Cette méthode est appliquée à différentes configurations représentatives du comportement de l'échangeur, permettant de s'assurer de sa robustesse lorsque le simulateur change, lorsque l'aspect multiéchelle est pris en compte ou lorsque une physique d'encrassement est considérée. Il a été établi que l'étape de métamodélisation assure la robustesse de la méthode et l'intégration de l'aspect multiéchelle. Elle permet aussi de construire des corrélations à l'échelle locale qui sont ensuite utilisées pour déterminer les performances globales de l'échangeur. Dans un contexte industriel, les méthodes d'analyse permettent de mettre en évidence un nombre fini de formes réalisant un compromis des fonctions objectif antagonistesHeat exchangers are used in many industrial applications. Optimizing their performances is a key point to improve energy efficiency. Heat exchanger behaviour is a multi-scale issue where local scale enhancement mechanisms coexist with global scale distribution ones. It is also multi-physics such as fluid mecanics, heat transfer and fouling phenomenons appear. The present work deals with multi-objective shape optimization of heat echanger. The proposed method is sufficiently robust to address multi-scale and multi-physics issues and allows industrial applications. Heat exchanger performances are evaluated using computational fluid dynamics (CFD) simulations and global methods (є-NUT). The optimization tools are a genetic algorithm coupled with kriging-based metamodelling. Clustering and Self-Organizing Maps (SOM) are used to analyse the optimization results. A metamodel builts an approximation of a simulator response (CFD) whose evaluation cost is reduced to be used with the genetic algorithm. Kriging can address discontinuities or perturbations of the response by introducing a nugget effect. Adaptive sampling is used to built cheap and precise approximation. The present optimization method is applied to different configurations which are representative of the heat exchanger behaviour for both multi-scale and multi-physics (fouling) aspects. Results show that metamodelling is a key point of the method, ensuring the robustness and the versatility of the optimisation process. Also, it allows to built correlations of the local scale used to determine the global performances of the heat exchanger. Clustering and SOM highlight a finite number of shapes, which represent a compromise between antagonist objective functions, directly usable in an industrial context
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Sridharan, Harini. "COUPLED DYNAMICS OF HEAT TRANSFER AND FLUID FLOW IN SHEAR RHEOMETRY". University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1597346164780318.
Testo completo
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Gomaa, Abdalla Galal. "Thermo-fluid characteristics of fin-and-tube heat exchangers with various fin details for air conditioning applications". Thesis, Northumbria University, 2002. http://nrl.northumbria.ac.uk/3513/.
Testo completoAbstract (sommario):
The need for more efficient air conditioning systems requires an in depth understanding about the performance of its components. One of the key components in the air conditioning plant is the fin-and-tube cooling coil, which is investigated here. The main focus of the work is concerned with the analysis of fin-and-tube cooling coils having two classes of passive enhancement techniques known as corrugated and turbulated fins with particular reference of developing flow region. Initially, two-dimensional modelling was done to establish the scope of later three-dimensional modelling in terms of dominant variables, meshing strategies and convergence criteria. The results gave key insights into required modelling strategies needed for the more complex three-dimensional problem of the composite fin-and-tube cooling coil. Three-dimensional CFD modelling of fin-and-tube cooling coils having turbulated, corrugated and flat-fin geometries have been investigated with particular reference to the dry-hot arid climate. Five modelling approaches have been considered based on an isothermal fin-and-tube, periodic boundaries, conjugate heat transfer, tube-row temperature gradient and the effect of manufacturing defects. The last three approaches are novel contributions to this field of research. The influences of the key design parameters of fin pitch, fin material, and fin thickness have also been investigated parametrically for all fin types. To provide confidence in these models, experimental studies on these cooling coils were carried out to acquire data for comparison between the predicted and measured values of heat transfer and friction, and to investigate the effect of range of design conditions on the cooling coils performance. The detailed results of this work can be used to optimise the air-conditioning coil designs. The turbulated fin coil was found to give the highest values of Nusselt number at given friction factor followed by the corrugated fin coil. At a given pressure drop (dP = 52 N/m2 corresponding to 14, = 2.3 m/s), the heat transfer coefficient of the corrugated and turbulated fin coils was higher than that of flat fin by 16 % and 36 % respectively. For typical operating conditions, the corrugated and turbulated fin coils required core volumes of 19 % and 40 % less than that of flat fin coil respectively for the same performance. The cooling coils employing corrugated and turbulated fin geometries contribute significantly to the energy conservation and volume reduction of the air conditioning plant.
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Faggembauu, Débora. "Heat transfer and fluid-dynamics in double and single skin facades". Doctoral thesis, Universitat Politècnica de Catalunya, 2006. http://hdl.handle.net/10803/6690.
Testo completoAbstract (sommario):
Una proporción muy importante del presupuesto energético total de los países europeos es destinado al consumo energético del sector de la edificación, tanto en el ámbito doméstico como terciario. Debido a que esta tendencia continúa en aumento, es de vital importancia optimizar los edificios tanto desde el punto de vista de las envolventes térmicas, como de las instalaciones térmicas y las condiciones de operación y funcionamiento.Esta tesis incide fundamentalmente en el diseño eficiente de la fachada, ya que éste es uno de los principales elementos que determinan el comportamiento térmico de los edificios. No sólo actúa como barrera entre las condiciones externas e internas, sino que el diseño eficiente de la misma, contribuye en forma relevante a la reducción del consumo de calefacción, aire acondicionado, ventilación e iluminación. Asimismo, es un elemento que incide notablemente en las condiciones de salubridad y confort.
Actualmente, existe un gran auge del uso de fachadas completamente hechas de vidrio, este tipo de construcción presenta una serie de ventajas arquitectónicas y estéticas, pero desde el punto de vista térmico pueden representar problemas de sobrecalentamientos y pérdidas de energía importantes, tanto en las áreas mediterráneas como en otras zonas climáticas. En este sentido, las fachadas de doble piel, compuestas por dos capas separadas por un canal de aire, usado para evacuar o aprovechar la energía solar absorbida por la fachada, pueden representar una opción de diseño válida para solventar esta problemática. Asimismo, este tipo de diseño puede producir unas condiciones de confortabilidad adecuadas debido a la reducción de las temperaturas de las superficies interiores de las fachadas.
El objetivo de esta tesis es el de contribuir al estudio de sistemas pasivos en general, y fachadas avanzadas en particular. Para ello, se ha desarrollado una herramienta numérica para la simulación de fachadas de edificios de simple y doble piel. La principal característica de este código es la de asumir un comportamiento unidimensional y transitorio. Las ecuaciones gobernantes (continuidad, momentum y conservación de la energía) son resueltas mediante la aplicación del método de volúmenes finitos. Las fachadas incluyen elementos arquitectónicos novedosos, como materiales de cambio de fase, aislamiento transparente, superficies selectivas y colectores solares con acumuladores integrados en la superficie de las fachadas. En la tesis, se describen las características de los modelos físicos y matemáticos implementados y se definen parámetros instantáneos e integrados que describen el comportamiento térmico de las fachadas.
Los modelos numéricos implementados han sido sujetos a procesos de verificación y validación en diferentes formas: i) por comparación de los resultados numéricos con los obtenidos para situaciones simplificadas que cuentan con solución analítica, ii) por comparación con parámetros globales tabulados en la literatura de ciertas configuraciones de fachadas, y iii) por comparación de los resultados numéricos con los obtenidos experimentalmente en celdas de ensayo sometidas a diferentes condiciones climáticas.
Se presentan resultados de estudios paramétricos de diferentes configuraciones de fachadas y aplicaciones del código numérico para la optimización del diseño de fachadas de edificios emblemáticos del entorno. Como acciones futuras, se prevé la conexión de este tipo de simulaciones con otras de más alto nivel, bidimensionales, para optimizar zonas concretas de las fachadas.
A significant proportion of the total national energy budget of european countries goes toward energy consumption in buildings, therefore the efforts addressed to optimize building's thermal behaviour are of vital importance. In this sense, facades play a fundamental role. Not only do they act as barriers between external and internal conditions, but they can also help to reduce the consumption of energy for heating, ventilation and air conditioning. Moreover, they can help to produce healthy and comfortable indoor conditions. The use of large, transparent areas in facades is a common current practice. Despite the architectural interest of these glazed areas, in Mediterranean climatic conditions they are responsible for building overheating. In these zones, double-skin envelopes made up of two layers of glass separated by an air channel -to collect or evacuate the solar energy absorbed by the facade- are considered to be a design option that could resolve this issue. In other climatic conditions, large heat losses may constitute the most determinant factor. Anyway, the comfort parameters are influenced by the large transparent areas, also in this design aspect, double skin facades may contribute to obtain more comfortable and pleasant living spaces.
The objectives of this thesis are to give a step forward in the study and numerical analysis of passive systems in general, and advanced facades in particular. A one-dimensional and transient numerical code for the simulation of double and single skin facades including advanced technological elements, like phase change materials, transparent insulation and facade integrated collectors-accumulators has been developed. The features of the physic and mathematical models implemented are described and instantaneous or integratedperformance parameters describing thermal behaviour of the facades are defined. The numerical models implemented within the numerical tool have been subjected to a verification and validation process in different forms: by comparing the numerical results with those obtained for simplified situations with analytical solutions, with tabulated global performance coefficients of simple façade configurations and with the results of other building simulation codes. Experimental research has been carried out in test cells situated at different geographical locations, thus they were subjected to different climatic conditions. The main objective of the developed numerical code is to simulate advanced facades in order to assess the long term performance, and to account with a virtual tool to test passive designs, including challenging innovations.
The applications of the numerical tool described in this thesis, for the optimisation of facades of real buildings are presented. As future actions, the link of the one-dimensional simulations produced by this numerical tool with a multi-dimensional simulation of specific zones of the facades is foreseen.
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Nijemeisland, Michiel. "Verification Studies of Computational Fluid Dynamics in Fixed Bed Heat Transfer". Digital WPI, 2000. https://digitalcommons.wpi.edu/etd-theses/318.
Testo completoAbstract (sommario):
Computational Fluid Dynamics (CFD) is one of the fields that has strongly developed since the recent development of faster computers and numerical modeling. CFD is also finding its way into chemical engineering on several levels. We have used CFD for detailed modeling of heat and mass transfer in a packed bed. One of the major questions in CFD modeling is whether the computer model describes reality well enough to consider it a reasonable alternative to data collection. For this assumption a validation of CFD data against experimental data is desired. We have developed a low tube to particle, structured model for this purpose. Data was gathered both with an experimental setup and with an identical CFD model. These data sets were then compared to validate the CFD results. Several aspects in creating the model and acquiring the data were emphasized. The final result in the simulation is dependent on mesh density (model detail) and iteration parameters. The iteration parameters were kept constant so they would not influence the method of solution. The model detail was investigated and optimized, too much detail delays the simulation unnecessarily and too little detail will distort the solution. The amount of data produced by the CFD simulations is enormous and needs to be reduced for interpretation. The method of data reduction was largely influenced by the experimental method. Data from the CFD simulations was compared to experimental data through radial temperature profiles in the gas phase collected directly above the packed bed. It was found that the CFD data and the experimental data show quantitatively as well as qualitatively comparable temperature profiles, with the used model detail. With several systematic variances explained CFD has shown to be an ample modeling tool for heat and mass transfer in low tube to particle (N) packed beds.
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Kent, Russell Malcolm. "Modelling fluid flow and heat transfer in some volcanic systems". Thesis, Lancaster University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306912.
Testo completo
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Aliev, Ruslan. "CFD Investigation of Heat Exchangers with Circular and Elliptic Cross-Sectional Channels". Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1452678890.
Testo completo