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CFD simulation of fluid-induced vibration
Kubíček, Radek ; Vondál, Jiří (referee) ; Buzík, Jiří (advisor)
The presented diploma thesis focuses on flow-induced vibrations of a tube. The main aim and benefit is the analysis of tube stiffness in contact with the other one and the following use of obtained values and characteristics in CFD simulations. The work can be divided into three parts. The first part is about the current state of knowledge of flow-induced vibrations. It introduces the basic mechanisms of vibration and methods for their suppression. The second part deals with the determination of stiffness of defined geometry tube including the collision with the other tube. The final part demonstrates and evaluates the application of obtained characteristics in CFD simulations.
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Algorithm for automatic selection of suitable equipment type from heat exchanger database
Havlů, Michal ; Kohoutek, Josef (referee) ; Jegla, Zdeněk (advisor)
Thesis is devoted to development of an database algorithm for selection (or necking selection) of suitable type of heat exchanger for given industrial application. Database creates a part of multipurpose calculation system containing three individual modules: (i) module for selection (or necking selection) of type of heat exchanger for given application, (ii) module for thermal-hydraulic design or rating of heat exchanger, (iii) module for calculation of investments and operating cost. Thesis describes details of method for selection of suitable heat exchanger type for given application and presents and discuss individual criteria for selection process which influence values in tables of priorites for given equipment. These tables are unavoible part of selection algorithm. Details of software application of selection algorithm are also presented in the thesis. Description of behaviour of individual types of heat exchanger creates important part of thesis. Practical application of developed selection algorithm is demonstrated on several industrial examples.
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Fluid Flow in Nonstandard Process and Power Equipment
Chýlek, Martin ; Babička Fialová, Dominika (referee) ; Turek, Vojtěch (advisor)
Flow distribution has big importance in equipment with limited tube rows because it provides correct operation and sometimes specific flow distribution for technology purposes is needed. This thesis is focusing on flow analysis in these units using computational fluid dynamics (CFD). For analysis of such systems models with varying tube rows and varying perforated segment lengths were created. Analysis showed significant impact of flow manifold layout along with tube layout and number of tubes. Simplified 1D model using static pressure regain coefficient was created which provides much shorter computational times. Comparison of 1D and CFD models was made to determine field of their usage.
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The effect of boiler tube bundle fouling on its service life
Volná, Kateřina ; Ing. Zdeněk JŮZA, Ph.D., MBA (referee) ; Naď, Martin (advisor)
Fouling of tube bundles in boilers on the flue gas side affects not only the service life, but also the boiler heat output and increases maintenance and operating costs. Therefore, it is necessary to minimize or completely eliminate this process. This thesis focuses on comparison of the service life and the heat output of the tube bundles with and without deposit in the coal fired boiler. Simulations of flue gas flow in area of tube bundles with and without deposit are performed using ANSYS Fluent software, which shows that the surface of tube bundles with deposit is much less heated than the surface without deposit. The thermal loads of tubes obtained by the CFD analysis are applied to the model, which is created in the program ANSYS Mechanical, where the calculation of the temperature field in the cross section of the pipe is realized. The effect of fouling on creep life and heat output is then evaluated based on simulation results. The results show that fouling increases creep life, but significantly reduces heat output of heavily fouled tubes. Hence the flue gas flows at a higher temperature to the rest of the tube bundle, and the service life of those tubes will therefore probably decrease.
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Influence of calculation accuracy on final parameters of heat exchanger
Matyska, Stanislav ; Radil, Lukáš (referee) ; Foral, Štěpán (advisor)
The aim of this thesis is to make the design of the heat exchanger more accurate. It is assumed that the division of the tube bundle of the heat exchanger to a plurality of parts by the transferred thermal output can achieve more accurate values. The first part of this thesis is dedicated to the sorting of the heat exchangers according to different criteria, and a brief description of most of them. It describes what are their functions and what are the demands placed on them. Next, there is given a detailed description of the tubular heat exchanger, specifically the mantle one because it is fundamental for this thesis. To investigate the influence of calculation accuracy, there is selected a reference heat exchanger, which processes the study. There are described the main characteristics for the reference heat exchanger (transferred thermal output, heat transfer fluids, their temperature on inputs and outputs) and its construction (geometry of the heat exchanger, number of tubes, tube geometry). The thesis also discusses the influence of calculation accuracy of the heat exchanger at its parameters. In the next part, there is made a basic calculation of the tube bundle length and the pressure losses of the proposed heat exchanger. Here are assembled the theoretical basis for the calculation by dividing the tube bundle. Specific calculations are performed so that the tube bundle of the heat exchanger is divided into a selectable number of parts by the transferred thermal output. In each section, there is performed a calculation of the length of the specific tube bundle part. Individual lengths are added up and finally put together the entire tube bundle length. At the end of this section, there are calculated the pressure losses in the heat exchanger in a similar manner as for the calculating the total length of the tube bundle. In conclusion of this thesis there are described and clarified the results of the calculations. It examines the difference between the results of the reference and the proposed heat exchanger.
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Simplified flow distribution modelling
Rebej, Miroslav ; Vondál, Jiří (referee) ; Turek, Vojtěch (advisor)
Tato diplomová práce se zaměřuje na modelování proudění tekutiny v paralelních distribučních systémech, kde hraje důležitou roli rovnoměrnost distribuce tekutin. Pro tento účel je vytvořen vlastní CFD kód. Kód je napsán v programovacím jazyce Java a používá ke zlepšení výkonu knihovny třetích stran, které se vyznačují přímým přístupem ke hardwarovým a systémovým prostředkům. Kód se také vyznačuje určitými zjednodušeními, u nichž se očekává, že sníží výpočetní časy. Vliv použitých zjednodušujících opatření je vyhodnocen porovnáním výsledků simulací proudění na několika geometriích s údaji získanými z podrobných modelů CFD. Geometrie použitých svazků trubek se odlišují různými uspořádáními toku a trubek a také různým počtem trubek.
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Flow Induced Vibration Fatigue Analysis of Tube Bundle
Buzík, Jiří ; Vincour, Dušan (referee) ; Lukavský, Jiří (referee) ; Vejvoda, Stanislav (advisor)
The aim of the dissertation thesis is the control of the tube bundle on the cyclic fatigue caused by the flow past tube bundle. Fatigue due to flow is caused by flow-induced vibrations. Examined vibrations are caused by the mutual interaction of two phases (solid and liquid). The present work is focused mainly on the interaction of tube bundles with fluid. The current level of knowledge in this field allows to predict mainly static respectively quazi-static loading. These predictions are based on methods of comparing key vibration variables such as frequencies, amplitudes or speeds (see TEMA [1]). In this way, it is possible to determine quickly and relatively precisely the occurrence of a vibrational phenomenon, but it is not possible to quantitatively assess the effect of these vibrations on the damage of to the tube beam and to predict its lifespan, which would require the determination of the temperature field and the distribution of forces from the fluid on the beam. The aim of the work is to evaluate the-state-of-the-art, to perform a numerical simulation of the flow of fluids in the area of shell side under the inlet nozzle. Current methods of numerical analyses very well solve this problem, but at the expense of computing time, devices and expensive licences. The benefit of this work is the use of user-defined function (UDF) as a method for simulating interaction with fluid and structure in ANSYS Fluent software. This work places great emphasis on using the current state of knowledge for verifying and validation. Verifying and validation of results include, for example, experimentally measured Reynolds and Strouhal numbers, the drag coefficients and for example magnitude of pressure coefficient around the tube. At the same time, it uses the finite element method as a tool for the stress-strain calculation of a key part on tube such as a pipe-tube joint. Another benefit of this work is the extension of the graphical design of heat exchanger according to Poddar and Polley by vibration damages control according to the method described in TEMA [1]. In this section, the author points out the enormous influence of flow velocity on both the tube side and the shell side for design of the heat exchanger to ensure faultless operation. As an etalon of damage, the author chose a heat exchanger designated 104 from the Heat Exchanger Tube Vibration Data Bank [3]. With this heat exchanger, vibrational damage has been proven to be due to cutting of the tubes over the baffles. The last part outlines the possibilities and limits of further work.
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CFD simulation of fluid-induced vibration
Kubíček, Radek ; Vondál, Jiří (referee) ; Buzík, Jiří (advisor)
The presented diploma thesis focuses on flow-induced vibrations of a tube. The main aim and benefit is the analysis of tube stiffness in contact with the other one and the following use of obtained values and characteristics in CFD simulations. The work can be divided into three parts. The first part is about the current state of knowledge of flow-induced vibrations. It introduces the basic mechanisms of vibration and methods for their suppression. The second part deals with the determination of stiffness of defined geometry tube including the collision with the other tube. The final part demonstrates and evaluates the application of obtained characteristics in CFD simulations.
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Simplified flow distribution modelling
Rebej, Miroslav ; Vondál, Jiří (referee) ; Turek, Vojtěch (advisor)
Tato diplomová práce se zaměřuje na modelování proudění tekutiny v paralelních distribučních systémech, kde hraje důležitou roli rovnoměrnost distribuce tekutin. Pro tento účel je vytvořen vlastní CFD kód. Kód je napsán v programovacím jazyce Java a používá ke zlepšení výkonu knihovny třetích stran, které se vyznačují přímým přístupem ke hardwarovým a systémovým prostředkům. Kód se také vyznačuje určitými zjednodušeními, u nichž se očekává, že sníží výpočetní časy. Vliv použitých zjednodušujících opatření je vyhodnocen porovnáním výsledků simulací proudění na několika geometriích s údaji získanými z podrobných modelů CFD. Geometrie použitých svazků trubek se odlišují různými uspořádáními toku a trubek a také různým počtem trubek.
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The effect of boiler tube bundle fouling on its service life
Volná, Kateřina ; Ing. Zdeněk JŮZA, Ph.D., MBA (referee) ; Naď, Martin (advisor)
Fouling of tube bundles in boilers on the flue gas side affects not only the service life, but also the boiler heat output and increases maintenance and operating costs. Therefore, it is necessary to minimize or completely eliminate this process. This thesis focuses on comparison of the service life and the heat output of the tube bundles with and without deposit in the coal fired boiler. Simulations of flue gas flow in area of tube bundles with and without deposit are performed using ANSYS Fluent software, which shows that the surface of tube bundles with deposit is much less heated than the surface without deposit. The thermal loads of tubes obtained by the CFD analysis are applied to the model, which is created in the program ANSYS Mechanical, where the calculation of the temperature field in the cross section of the pipe is realized. The effect of fouling on creep life and heat output is then evaluated based on simulation results. The results show that fouling increases creep life, but significantly reduces heat output of heavily fouled tubes. Hence the flue gas flows at a higher temperature to the rest of the tube bundle, and the service life of those tubes will therefore probably decrease.
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