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The influence of the combustion air temperature on parameters of the combustion process
Šimeček, Radek ; Hudák, Igor (referee) ; Skryja, Pavel (advisor)
Tato diplomová práce se zabývá předehřevem spalovacího vzduchu a jeho vlivem na parametry spalovacího procesu. V teoretické části je zpracován přehled nejčastějších znečišťujících látek z průmyslového spalování. Je popsána aktuálně platná relevantní legislativa v Evropské unii a jsou porovnány její implementace do národní legislativy v České republice a v Německu. Dále je provedena klasifikace hořáků z hlediska různých kritérií a rešerše předchozí práce v oblasti předehřevu spalovacího vzduchu. Na zkušebně hořáků byla provedena experimentální studie dvou různých hořáků na zemní plyn při konstantním tepelném příkonu 750 kW se spalovacím vzduchem předehřátým až na 250 °C. Výsledky odhalily pozitivní vliv předehřevu na účinnost spalování. Množství emisí NOx a CO naopak rostlo s teplotou spalovacího vzduchu.
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Design of heating water heat exchanger, capacity 200 MW
Vašíček, Jakub ; Kól, Přemysl (referee) ; Baláš, Marek (advisor)
The thesis is focused on the design proposal of thermal heaters for heating water in heat-exchanger station with a total output of 200 MW. The aim of the work is conceptual design of heat exchangers, thermal and hydraulic design of individual heaters and preview of flow of mass and energy. The outputs of the work are written calculations, design drawing of one heater and design of a heater arrangement in exchanger station. The objectives of the work are filled completely. The work is focused on issues directly related to the actual design of heat exchangers, does not give a general overview of the topic. Thermal calculation is limited to the calculation of heat transfer surfaces for condensation of steam and condensate hypothermia.
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Heat flux calculation during boiling process – application for cooling of combustion chamber
Földváry, István ; Pačíska, Tomáš (referee) ; Vondál, Jiří (advisor)
There is a water-cooled combustion chamber at the Institute of Process and Environmental Engineering, which is used for testing of burners. Effective cooling is a particularly significant problem. It is also necessary to ensure accurate measurement of wall heat flux extracted by the cooling water. Therefore the main aim of the thesis is calculation of the minimum flow rate of cooling media required for safe operation of the combustion chamber. A comprehensive review of the heat transfer mechanisms was performed. Description is provided for the basic characteristics of phase changes with an emphasis on detailed analysis of mechanisms of boiling and evaporation. The presence of boiling at the water-side wall in the inner mantle was verified in the calculation part. Computation of the heat transfer coefficient was done by using the similarity methods. Temperature of the wall was then evaluated. A control on the presence of nucleate boiling was performed and the required minimum flow rate was determined for each section of the chamber.
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Characteristic parameters of oxygen-enhanced combustion process
Dřímal, Jiří ; Hudák, Igor (referee) ; Bělohradský, Petr (advisor)
The thesis is focused on the experimental investigation of the oxygen enhanced combustion technology (OEC), which uses the combustion air with higher concentration of oxygen, i.e. more than 21 %. The OEC technology is used in those industrial applications, which requires higher thermal efficiency, increased productivity, improved character of the flame, reduced equipment cost, lower volume of exhaust gases and improved product quality. Although this technology involves a number of advantages, it is appropriate to mention some of its disadvantages such as refractory damage, inconsistent heating, increased pollutant emission or flame disturbance and/or flashback. The combustion tests of OEC were carried out at the burners testing facility that enables to test many types of burners (gaseous, liquid, or combined). The two-staged low-NOx burner fired by natural gas was used during the tests. The observed parameters include the effect of oxygen concentration in the combustion air on the NOx emissions, heat flux into the wall of the combustion chamber, in-flame temperature distribution in the horizontal symmetry plane of the combustion chamber and also the shape and dimensions of the flame. The combustion tests of the air-enrichment, air-oxy/fuel and O 2 lancing OEC methods were carried out at the burner thermal input of 750 kW and air excess of 1,1 for two combustion regimes, namely one-staged and two-staged fuel supply.
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Coupled model of transformer
Adamec, Lukáš ; Huzlík, Rostislav (referee) ; Vlach, Radek (advisor)
The bachelor's thesis deals with the creation of a coupled model of transformer in the Matlab system. The coupled model connects two basic physical domains - electricity and heat transfer. It all starts with the selection of suitable equivalent circuit diagrams that represent the electrical and thermal properties. Their connection is then called as coupled model, which captures their mutual influence. An important part of the thesis is the identification of elements (thermal resistances and capacities, stray inductance, etc.) of equivalent circuit. Open-circuit and short-circuit tests are used to identify electrical elements, thermal elements are then determined from the temperature curves of the sub-parts of the transformer – core and winding. The goal of the thesis is that the output of the coupled model corresponds as closely as possible to the behavior of a real transformer. Compliance is verified by the final simulation.
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Rozložení tepelných toků na stěnu tokamaku způsobených okrajovými nestabilitami
Kripner, Lukáš ; Cahyna, Pavel (advisor) ; Urban, Jakub (referee)
Edge localized modes (ELMs) are a concern for future magnetic fusion devices, such as ITER, due to the large transient heat loads they generate on the plasma facing components. A very promising method of ELM suppression is an application of resonant magnetic perturbations (RMP); however, such application leads to localized places of higher heat fluxes called footprints. Both ELMs and RMP could limit the operational lifetime of the device. In this thesis, we analyze the temporal and spatial distribution of footprints using the tangle distance method in the aim to prevent a transient overheating. We also analyze quasi-double-null configuration of the ITER plasma which can be expected to be the most susceptible to overheating of the upper wall. Based on the modelling, the potentially dangerous configurations of the RMP have been shown. Using the ELM filament model included in the LOCUST GPU code, we study temporal and spatial distribution of the heat fluxes caused by ELMs in the axially symmetric and the asymmetric magnetic field. The results are compared with published experimental observations. Powered by TCPDF (www.tcpdf.org)
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Thermomechanical tire model
Vaníček, Jan ; Štětina, Josef (referee) ; Porteš, Petr (advisor)
This diploma thesis is about thermomechanics of passenger car tires. The research part dealing with existing tire models is followed by the practical part. The practical part is based on the designs of thermomechanical models. The first model determines a dependence of temperature on the air pressure inside a tire when a temperature changes. The second thermomechanical model captures all the heat fluxes which affect a tire while a vehicle is in motion. The third thermomechanical model calculates temperatures of parts of the tire during driving tests. All models are programmed in MATLAB.
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Mathematical simulation of temperature profile in the subsoil and creation of a model corresponding its real state
Charvátová, Pavlína ; Katunský,, Dušan (referee) ; Ostrý, Milan (referee) ; Čupr, Karel (advisor)
Increasing demands for low heat losses and energy intensity of a building influence energy calculations. Higher demands are placed on the accuracy of the calculations. An important part of the thermal engineering calculations is the determination of the correct boundary conditions. An important input factor is primarily the indoor and outdoor environment, and temperature is the most important parameter for these types of enviromnent. It is not always the temperature of the external environment, but the environment that is adjacent to the soil or to unheated or differently heated spaces. The possibilities of modeling temperatures below the object are described in the standard ČSN EN ISO 10211. This standard specifies details for a geometric model for the numerical calculation of heat flows to assess the total heat loss of buildings or parts thereof, as well as to derive linear and point heat transfer factors. Furthermore, to calculate minimum surface temperatures to assess the risk of surface condensation and to determine the surface temperature factors. These are two different computational models. Therefore, it would be appropriate to simplify these calculations by simplifying the boundary conditions, namely to conduct an isotherm at a certain level below the terrain, which will be considered as a boundary condition, which is also based on long-term experience with "frost-free" depth. This calculation would be unambiguous, clear and simple.
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Effect of activator type on rheology of alkali-activated slag
Markusík, David ; Smilek, Jiří (referee) ; Bílek, Vlastimil (advisor)
This work deals with rheology of alkali-activated slag pastes (AAP) because of importance of these properties in building connectors for processing and application. The effects of different concentrations of sodium and potassium hydroxides activation solutions on the rheological properties of prepared AAP are examined. For the basic characterization of activation solutions, rotational and rheological measurements of AAS were made, and were compared to measurements from the flow table. Dependences of setting time on the activator concentration and rheological and calorimetric monitoring of hydration progress were also investigated. The findings prove a major influence of concentration and activator type on any determinations made. In pastes activated by potassium hydroxide, fluidity increases with increasing concentration, which correlates with increases in values on the shake table. In case of sodium hydroxide, with the increasing concentration, fluidity increases up to 25 wt. %. The following sharp reduction in fluidity correlates to the values on the flow table as well as with the storage modulus courses from oscillation measurements. In the first minutes after mixing, there was evidence of a sharper increase in yield point for pastes with higher activator concentrations.
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