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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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Advanced computational methods for combustion of solid fuels
Strouhal, Jiří ; Vondál, Jiří (referee) ; Juřena, Tomáš (advisor)
The aim of this thesis was to create a model of thermal conversion of solid fuel. This is achieved by means of standard modelling tools included in software ANSYS Fluent in combination with user-defined functions (UDF). In first part of thesis basic approaches to CFD modelling of solid fuel combustion are presented. Building of a mathematical model and corresponding algorithms follows. Individual parts of a created model and its parts are tested on simple physical cases and then on case of experimental reactor for analysing biomass combustion.
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Hydrogen as a fuel in combustion processes
Friedel, Petr ; Brummer, Vladimír (referee) ; Vondál, Jiří (advisor)
First part of the bachelor’s thesis is focused on hydrogen as a fuel. Research was made from basic information about hydrogen, manufacturing processes, problems during storing and transporting. Another part of the research is focused on usage of hydrogen in energetics especially in combustion processes. Second part of the thesis describes modelling of chemical reactions. In this part is also composing software for chemical kinetics simulations. Combustion process of hydrogen and fuels enriched by hydrogen is simulated and described by this software.
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Heating units for family houses - algorithm for selection
Reiter, Milan ; Vondál, Jiří (referee) ; Kermes, Vít (advisor)
This bachelor’s thesis deals with the ways of heating for family houses. In the first part of this thesis are described the heat sources. The heat sources are diveded by type of fuel. In the next part of this thesis is a decription of claims for installation the heating source, the use of various fuels and chimneys. In the next part are descibed claims of an operation the heating sources. The fourth part deals with the algorithm for selecting a source of heat. Here is a description of each step of algorithm, which we need for selection of suitable heat source. In the last part of my thesis is made a presentation of the algorithm performed on a model family home. There are selected six types of heating in the house. At the end is chosen one, most economical type.
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Fluid grate design and optimalization in the function aspect point of view and economy of production
Voráč, Petr ; Vondál, Jiří (referee) ; Nekvasil, Richard (advisor)
The Master´s thesis deals with the fluid layer, with types of fluidized layer and with problems which can be solve during design of new fluidized beds. The aim was find the fluidized grid, which is the best form economical and technological point of view. In this work are compared three fluidized grids. The first was part of submission. Next two additional types were then proposed by the author of thesis. Proposals grids are discussed in detail from the design phase, through the modeling and subsequent simulation part in a computer program. The results of simulation are pressure losses. Which are compared with the recommended interval values. Afterward these tested beds are put through technical and economic analysis. The result is grade which is met both requirements.
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Simplified modelling of tube bank heat exchanger in CFD
Cacková, Tereza ; Juřena, Tomáš (referee) ; Vondál, Jiří (advisor)
The master thesis deals with the replacement of heat exchanger surfaces during simulations in the ANSYS Fluent. The aim of this work is to find a simplified model of the heat exchanger usable for flow simulations in large process and energy units, where it is not possible to model the entire heat exchanger in detail. The calculation procedures are applied to „tube bank” heat exchanger. The master thesis is divided into three parts. First part deals with pressure losses. The "porous zone" approach is used as a replacement for the heat exchanger surface. In the second part, the heat transfer by convection and conduction through the heat exchanger is replaced by the "Heat Exchanger" module. The third part examines the influence of material properties, heat source and fixed temperatures on incident radiation. All calculations resulting from the methods are performed using a script that prepares the output data in format suitable for insertion into ANSYS Fluent. A simplification, which faithfully replaces a fully modeled heat exchanger, has been found in all three parts of the thesis.
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Ejectors and it's utilization in industry
Zejda, Vojtěch ; Hájek, Jiří (referee) ; Vondál, Jiří (advisor)
This work aims at introducing ejector pumps. It describes the working principle, advantages and disadvantages and restrictions of their usage in various applications. Main disadvantage of ejectors is the low efficiency which limits the usage only in specific applications where it is not considered to be a crucial factor. Therefore, examples of usage of various ejectors in industrial processes are listed further. Last but not least, in these examples are also demonstrated difficulties and reasons why it is favourable to use an ejector rather than other types of pumps. Further off, this work deals with design methods of ejectors and compares their suitability. It appears that not all the methods are suitable for ejector design, because it depends greatly on presumed shape of a certain ejector. In the end, there is compared energy intensity of an ejectors and common centrifugal pumps and confirms energy disadvantage of ejectors.
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Design optimization of water-cooled thermocouple probe
Dohnal, Miloslav ; Vondál, Jiří (referee) ; Hájek, Jiří (advisor)
The object of this bachelor’s thesis is to create a computational model of an existing (basic) structure water-cooled thermocouple probe, to calculate and evaluate the quality of existing cooling probe and to propose possible design modifications to improve the cooling effect of the probe tip. Verify and evaluate design modifications by further calculation. The calculation will be carried out using computational fluid dynamics (CFD method). On the contrary, the aim of this work is not to create another text tool for students dealing with CFD topics. The first part describes the meaning and history of the CFD methods, then mentions the work on the principle of thermocouple probes and its application in practice. The second part of the work is devoted to problem solving. It describes the reason for the introduction of model situations when calculating the cooling effect of thermocouple probes and calculation indicates what type of flow occurs inside the thermocouple probe. It further describes the results of calculations for several approximations gradually increasing accuracy of the resulting solution of the problem and assessing the quality of cooling in the probe tip current (basic) structure. The final part deals with design changes for better cooling effect especially in the probe tip, which is verified by further calculation as well.
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Velocity profile measurement downstream of swirler
Zejda, Vojtěch ; Hájek, Jiří (referee) ; Vondál, Jiří (advisor)
A burner is very important device in process furnaces that significantly affect the production of emissions during the combustion process. One of the key things in development of the modern low-NOX burners is the evaluation of flow field downstream of an axial blade swirler inside the burner. The computational fluid dynamics (CFD) is often used to predict the attributes of the flow. Predicted values should be validated with measurement. It is the reason why the velocity fields for several choosen swirlers were measured. The hot wire anemometry was choosen and the dual-sensor probe was used during the measurement. The data can be then used for CFD validation. This thesis describes procedure of measurement set-up. The experimental facility was designed according to the anemometry method. The new probe traversing system was designed, which provides desired accuracy. Five different swirlers were measured. Large data set, need for customized post-processing and control over calculation procedures lead to new software design. For each swirler the velocity profiles were gathered and the swirl numbers calculated. That final data were transferred in to graphical format. Uncertainty of measured data was calculated. Results show counter-rotating flow in some areas closed to the swirler. Some drawbacks of current measurement set-up are discussed. Based on the thesis reader can obtain the information and knowledge for consequent measurements of swirl burners velocity profiles.
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Stress-strength analysis of an impeller shaft using fluid-structure interaction modelling
Zifčáková, Barbora ; Vondál, Jiří (referee) ; Juřena, Tomáš (advisor)
This master’s thesis deals with numerical simulations of type FSI (Fluid Structure Interaction). Software used is ANSYS Fluent and ANSYS Mechanical. The aim of this thesis is to study the interaction between fluid flow in the mixing tank used in pharmaceutical industry to process eggshells and the agitator whose shaft has deformed during operation. CFD part consists of both one-phase and multi-phase transient simulations. The impact of solid body deformation on fluid flow is neglected hence only one-way Fluid Structure Interaction is considered for the simulations. Fluid flow in the tank and stress-strain behavior of the shaft is evaluated both in quasi-steady state and during start-up of the device. Computations showed that the impact of eggshells on agitator is negligible during operation (in quasi-steady state) unlike the behavior during start-up of the device when stresses and strains of the shaft are significantly higher. Possible reasons why the shaft deformed are presented and further numerical simulations are discussed and suggested.
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