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CFD modelling of the initial phase of fouling inside convective section of a combustion facility
Zlámal, Filip ; Juřena, Tomáš (referee) ; Strouhal, Jiří (advisor)
The aim of this thesis was to create, based on the knowledge obtained from research, a CFD simulation of initial phase of fouling of solid particles during the combustion of solid fuels. The introduction of the work summarizes the mechanisms of fouling by solid particles. The introduction of the work summarizes the mechanisms of fouling by solid particles. Approaches to modelling the impact and deposition of particles are also described. A model is built, which is implemented in the ANSYS Fluent software with the addition of user-defined functions. The model is tested on a model of the convective part of an experimental device for burning solid fuels.
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Perspective trends in hydrogen production methods
Leitkep, Jan ; Juřena, Tomáš (referee) ; Brummer, Vladimír (advisor)
Bachelor’s thesis is focused on perspective methods of hydrogen production. First chapters are focused on research of hydrogen resources, methods of hydrogen production and spectrum of its worldwide utilization in present. In this part of the bachelor’s thesis percentage representations of hydrogen resources are stated. Methods of hydrogen production from these resources are described and processes utilizing hydrogen are introduced. Subsequently, the properties of hydrogen fuel are summarized. Following chapters are focused on perspective methods of hydrogen production, hydrogen storage, perspectives of its future usage as a fuel, price of hydrogen produced by these methods and environmental impact of these methods.
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Transport and thermophysical data for thermic sanitation calculation of agricultural seeds
Vávra, Dan ; Brummer, Vladimír (referee) ; Juřena, Tomáš (advisor)
The bachelor's thesis focuses on properties that are important for thermal sanitation. Commonly used seed treatment methods are summarized in the theoretical part. Furthermore, seeds‘ transport and thermo–physical properties are written out and described. To the present day, the properties of wheat seeds have been determined, while there are fewer publications for pea seeds. The available properties were determined by research for wheat and pea seeds. Furthermore, the experimental procedures for obtaining wheat properties were verified and then the procedures were applied to pea seeds. In the experiments, values were obtained for porosity, bulk density, true density, static angle of repose and specific heat capacity for certain humidity. The results are written out with total measurement uncertainties. The values of properties were discussed.
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Flue gas condensation in a domestic wood pellet boiler
Koreň, Denis ; Jecha, David (referee) ; Juřena, Tomáš (advisor)
The diploma thesis deals with the analysis of flue gas condensation with the possibility of using flue gas humidification in a domestic wood pellet boiler. The review is focused on flue gas humidification in condensing solid fuel boilers and on water vapour condensation in the presence of non-condensable gases. A description of the wood pellet boiler with balance calculations of flue gas temperature and composition is given. The flue gas condensation in the boiler heat exchanger section is analysed on a CFD model developed in ANSYS Fluent. Experimental measurement data are used to validate the developed model. The CFD simulations are evaluated with respect to heat transfer and flue gas condensation rate. The effect of turbulators and flue gas humidification is taken into account. The thesis concludes with an evaluation of flue gas humidification in solid fuel boilers in terms of thermal efficiency, reduction of particulate emissions in the flue gas and boiler design.
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Parametric Generator of Heat Exchanger Tube Bundle Mesh for OpenFOAM
Petrů, Martin ; Juřena, Tomáš (referee) ; Turek, Vojtěch (advisor)
This thesis deals with the basics of computational fluid dynamics (CFD), the reasons for its use, and the related necessity to create computational meshes. The next part of the thesis focuses on assessing the quality of computational meshes and, briefly, on computational methods of CFD. The available mesh generators are also compared, and an overview of meshing capabilities is provided. The following is basic information about the OpenFOAM software and its capabilities, in particular the creation of meshes using the blockMesh application. The following part of the thesis is focused on the description of the developed application and its functions for generating a high-quality computing mesh of a tube bundle heat exchanger for the OpenFOAM software. In conclusion, a steady flow simulation verifies the correctness of the created mesh and its sufficient quality.
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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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Extrapolation of diagrams of resistance coefficients using virtual experiment
Koreň, Denis ; Vondál, Jiří (referee) ; Juřena, Tomáš (advisor)
As a part of pneumatic breaking systems, disc valves are used for very small actuations of the valves, for which no values for pressure losses are found in literature. The correct design shall be made conditional on the total pressure loss of system, a part of which also occurs in the flow of the given valve. The work is initially devoted to a description of the calculation of the resistance coefficient and the characteristics of the physical processes during the flow in the idealized valve. Consequently, design of the model for the flow at the entrance into the valve end at the exit from the valve, including the setting of the simulations in the Fluent, is clarified. An important part of the work are sensitivity tests of the model to Reynolds number, to the model of turbulence and the mesh resolution near the wall. In addition, the results of simulations for various relative scales of the model are compared with experimental data given in the literature. The outputs of the work are the resistance coefficients, which extrapolate the data in the available resources, especially for valves with small relative actuation (h/Dh
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Usage of flue gas as a source of CO2 for algae cultivation in bioreactors
Slonek, Jaroslav ; Juřena, Tomáš (referee) ; Brummer, Vladimír (advisor)
This master`s thesis is focused on possibility of use of flue gas as source of CO2 for algae cultivation in bioreactors. The first part of the master`s thesis is devoted to a qualitative and quantitative description of flue gas sources as CO2 source for algae cultivation. In the thesis industry sectors with the largest share of CO2 emissions on a global scale and in the Czech republic are summarized. On the basis of these data it was possible to determine cheap sources of CO2 for algae cultivation producing valuable biomass and other bio-products. The composition of flue gas from these sources was discussed in this section also with given expected outlook within the following years. The next part of the thesis is devoted to the influence of flue gas properties on algae cultivation. The impact of flue gas individual parameters on cell growth rate, quality and composition of biomass is described there. The description and design of the bioreactor is processed in the next part of the thesis. The experimental part of the thesis was performed on a bioreactor with similar properties. The next part of the thesis describes the effect of light on algae cultivation and the design of a regulation scheme for bioreactor light source. The experimental part of the thesis describes methods used to determine the concentrations of flue gas substances that could pass from flue gas into cultivation medium for algae cultivation to measure the changing composition of the flue gas in the closed experimental bioreactor system. The processed data from experimental measurements are presented and are discussed. The change in the composition of the culture medium for algae (without the presence of algae) due to flue gas aeration was monitored in the experimental part. It includes also the measurement of the change in the composition of the flue gas in time. All obtained and collected information are then summarized and discussed in the final part of the master`s thesis.
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CFD modelling of granular flow in rotary kiln
Slowik, Roman ; Vondál, Jiří (referee) ; Juřena, Tomáš (advisor)
This work deals with modeling the flow of particulate matter in rotary kilns. For this purpose, a combined CFD and Discrete Element Method (DEM) model was used. Using Ansys Fluent software, several simulations were performed in order to determine the mean residence time and movement of the material in the rotary drum dryer. Results of the computational model were used to develop a regression model of the mean residence time and compared to the values as given by empirical equations. Furthermore, a simplified sensitivity analysis was performed for the selected input parameters of the model such as the stiffness constant, air mass flow rate and the particle size.
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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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