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High Voltage Switchgear Thermal Distribution Analysis
Bílek, Tomáš ; Rudolf, Pavel (referee) ; Hrabovský, Jozef (advisor)
Cílem této práce je analýza teplotního pole vysokonapěťového rozvaděče. Tato analýza je založena na kombinaci experimentálního měření a CFD simulace proudění vzduchu v prostoru rozvaděče. Na základě výsledků pro referenční geometrii jsou předloženy návrhy na úpravu topologie rozvaděče, které mají za cíl snížení teploty kritických komponent rozvaděče během jeho provozu. Druhá část práce je spojena s problematikou oteplení plošných spojů, jakožto hlavních zdrojů tepla v prostoru rozvaděče. Pro popis závislosti oteplení plošného spoje na jeho charakteru byla použita statistická metoda design experimentu. Výsledky z experimentálního měření jsou podpořeny konečně prvkovým modelem kontaktu spoje.
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Assessment of three types of heat exchangers
Hlavinková, Valérie ; Toman, Filip (referee) ; Baláš, Marek (advisor)
The aim of this thesis is to assess selected three types of heat exchangers designed for emergency cooling. The theoretical part of this thesis consists of a research containing an overview of exchangers. It includes a description of the construction of exchangers, characte-ristics in terms of heat transfer and an indication of the areas of its use. The practical part deals with the thermal and hydraulic design of two tube heat exchangers and a plate heat exchanger. Finally, the evaluation of the designed exchangers is performed.
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Water cooling intensity prediction for given thickness of oxide layer
Haluza, Vít ; Hrabovský, Jozef (referee) ; Pohanka, Michal (advisor)
This diploma thesis is dealing with the impact of oxide scales on heat conduction. One of the main tools that were used are numerical simulations. Heat conduction is modelled by solving partial differential equations. Regression models and artificial neural networks are used for the prediction of the influence of oxides on cooling intensity. Determination of the conditions when the cooling was intensified and comparison of individual methods of prediction are the main results of the thesis.
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The Development of Inverse Heat Conduction Problems Focused on Very Fast Processes in Microscales
Bellerová, Hana ; Jaroš, Michal (referee) ; Dohnal, Mirko (referee) ; Raudenský, Miroslav (advisor)
The inverse heat conduction task is solved to determine boundary condition of the heat equation. This work deals with the ways how to increase the accuracy of the results obtained by solving inverse task based on the Beck sequential algorithm. The work is focused on the boundary condition changing very fast. This boundary condition is determinable with difficulty. It is shown that the placement and the type of the thermocouple play major role in accuracy of the calculation. The frequency of measuring and the discriminability of used devices also play a role as well as the setup of parameters in the inverse task. The election of mentioned parameters is described with regard to the speed of cooling. Knowledge from the theoretical part of the work is applied in the experimental part. The cooling intensity is investigated during spraying of the steel sample by water with nanoparticles Al2O3, TiO2, Fe and MWNT at three different concentrations. The experiments were carried out for three spray heights (40, 100, 160 mm), three flow rates (1, 1.5, 2 kg/min) and two types of the nozzle (full cone and solid jet). Surprisingly, the cooling intensity by using nanofluids is lower about 30% in comparison to the cooling intensity of pure water. But there was an exception. The cooling intensity of 1 wt.% of carbon nanotubes in water falling from the full cone nozzle placed in distance of 100 mm from the steel surface was higher about 174%. Finally, the reasons of the behavior of nanofluids are discussed.
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Heating Module for the Electrospinning Electrode
Lukesle, Václav ; Musil, Vladislav (referee) ; Pokorný,, Marek (advisor)
The thesis deals with the principal heating design of the electrospinning electrode. These electrodes are fed with high voltage (tens of kV), which is an essential part of the device for the nanofibres production. This thesis presents the research of possible solutions of the heating and also it analyzes some principles of the nanofibre production. Furthermore, the work presents electrical schematics and PCB of the heating module. The aim of this work is to propose such a solution of heating that makes spinning from melt realizable in the device for 4SPIN ® nanofibres production.
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Car cabin passive cooling system performance study
Viščor, Petr ; Hejčík, Jiří (referee) ; Fišer, Jan (advisor)
The work is focused on issue of passive cooling in a cabin of a car. The basic principles and mechanisms of heat transfer are described in the theoretical part and the quality of cabin environment in terms of thermal comfort and air quality is discussed as well. Next part of the work describing the principles of ventilation and air conditioning of cabins and possible methods of passive cooling are discussed. Passive cooling means decrease of temperature of cars interior, without need of energy supply from car battery, or fuel. The last part of the work includes numerical simulation of selected methods of passive cooling using the THESEUS-FE 3.0 software. Simulations were performed on model of Volkswagen Polo car and primarily were focused on testing of functionality of various methods of passive cooling.
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Effect of building construction on thermal load of space
Výravská, Zdeňka ; Ell, Jiří (referee) ; Tesař, Zdeněk (referee) ; Rubina, Aleš (advisor)
This master’s thesis focuses on effect of outer building construction on thermal load of space. The effect of translucent and non-translucent construction is discussed. The project of air-conditioning system is prepared for the two alternatives of the translucent construction, including the purchase price of the airconditioning system and glazing and the savings on summer cooling. Afterwards the period of the recovery of investment is calculated. The plan of the airconditioning system is connected to my bachelor’s thesis “Airconditioning in the car showroom”, the subject of which was the plan of the airconditioning system of the car showroom.
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Heat transfer in the tubular exchangers
Horvát, Petr ; Krištof, Ondřej (referee) ; Svěrák, Tomáš (advisor)
Shell and tube heat exchangers and their use in cooling processes are the major topic of this thesis. The theoretical part of the thesis starts with the mechanisms of heat transfer and then deals with shell and tube heat exchangers. Their position, design specifications and equations for calculations are given. In the experimental part, the heat transfer on semi-operating shell and tube heat exchangers with baffles and glass or silicon carbide heat exchange surface is examined by cooling the humid air by 50% propylene glycol in tubes. For four or five coolant flows and three airflows, input and output flow temperatures including relative air humidity were measured. Differences in exchanged heat between the exchangers were negligible due to the low local air heat transfer coefficient, although silicon carbide has two orders of magnitude better thermal conductivity than glass. Much higher efficiency was performed by the carbide heat exchanger because the difference between air outlet temperature and liquid inlet temperature was one and half times higher for the glass heat exchanger. That was reflected in a decrease in mean temperature difference, which resulted in a 16 % higher experimental heat transfer coefficient compared with the glass surface. The theoretical model using the j factor, the correction factors for the baffles, and the correction for air humidity condensation have proven to be appropriate. For the glass surface, for the highest air flow rates the model gives an appropriate heat-transfer coefficient; at lower flow rates it gives slightly higher values. For the silicon carbide surface, it gives a lower heat-transfer coefficient because the model failed to consider a lower mean temperature difference. The results also evaluate the heat loss through the shell and the heat exchanged in addition by air humidity condensation.
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Influence of Bottom Preheating in Rework of Assembled PCB
Čechák, Ondřej ; Bžoněk, Tomáš (referee) ; Starý, Jiří (advisor)
This bachelor's thesis introduces the problematics of physical mechanisms of heat transfer and the correlative mathematical formulas and the use of mentioned problematics in the technology of bottom preheating in the rework of assembled printed circuit boards. It explains the importance and reasons of use of this technology, not merely in the professional production. It focuses on expert analysis of the appliances based on their properties and clarifies the differences in basic types of the devices. The emphasis is then laid on a practical testing of the technical parameters of the preheating devices as well as on an experimental design and a practical testing of a local bottom printed circuit board preheater.
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New Elements of Heat Transfer Efficiency Improvement in Systems and Units
Turek, Vojtěch ; Klemeš,, Jiří (referee) ; Odstrčil, Miloslav (referee) ; Jegla, Zdeněk (advisor)
Zvýšení efektivity výměny tepla vede k poklesu spotřeby energie, což se následně projeví sníženými provozními náklady, poklesem produkce emisí a potažmo také snížením dopadu na životní prostředí. Běžné způsoby zefektivňování přenosu tepla jako např. přidání žeber či vestaveb do trubek ovšem nemusí být vždy vhodné nebo proveditelné -- zvláště při rekuperaci tepla z proudů s vysokou zanášivostí. Jelikož intenzita přestupu tepla závisí i na charakteru proudění, distribuci toku a zanášení, které lze všechny výrazně ovlivnit tvarem jednotlivých součástí distribučního systému, bylo sestaveno několik zjednodušených modelů pro rychlou a dostatečně přesnou predikci distribuce a také aplikace pro tvarovou optimalizaci distribučních systémů využívající právě tyto modely. Přesnost jednoho z modelů byla dále zvýšena pomocí dat získaných analýzou 282 distribučních systémů v softwaru ANSYS FLUENT. Vytvořené aplikace pak lze využít během návrhu zařízení na výměnu tepla ke zvýšení jejich výkonu a spolehlivosti.
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