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Quantification of the thermohydraulic characteristics of the flexible element using experimental data
Sochorec, Rostislav ; Kilkovský, Bohuslav (referee) ; Jegla, Zdeněk (advisor)
The diploma thesis aims to establish thermo-hydraulic properties of a flexible tube described by its Darcy friction factor and film heat transfer coefficient respectively. A flexible tube (corrugated stainless steel tube) is an easily shapeable stainless steel component used to build various piping connections, in a place of more common copper or plastic made tubes. It can also be used to build heat exchangers thanks to its signature properties. The investigated product is the one developed and manufactured by the Czech company Flexira s.r.o. and sold under the brand name xConnect System. Its thermo-hydraulic properties are established by an experiment, which is based on real utilizations by Laboratory of Energy Intensive Processes in NETME (New Technologies for Mechanical Engineering) Centre at Brno University of Technology. The investigated case is a coil-shaped element serving a purpose of a water-to-water heat exchanger. The text contains a literature survey of the chosen flexible tube and a description of a draft and development of the specific experimental test based off the established theory. The obtained results are then analysed, for the purpose of establishing a functional dependence, which can then be used to calculate a film heat transfer coefficient.
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Thermal Losses of the Biomass Boiler
Suchánková, Lenka ; Milčák, Pavel (referee) ; Kracík, Petr (advisor)
The bachelor thesis focuses on the heat loss of the solid fuel boiler, especially on the loss of heat conduction and transfer to the surroundings. In order to minimalize thermal leaks through the boiler walls, materials with good isolation capabilities must be selected when designing. In Microsoft Excel, a universal mathematical model was created to calculate the heat flux flowing through the flat wall of the boiler, from which temperatures can be obtained on the inside of the wall. The work describes the calculation method on which the model is based and its correctness is verified on an experiment based on sensing of temperature fields of wall sur-faces of equipment burning biomass by thermal camera. The model can be used for a wall with up to 9 layers of material, where the wall can be cooled (heat loss) by air and water.
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Precipitation nowcasting for the warm part of the year
Mejsnar, Jan ; Sokol, Zbyněk (advisor) ; Jaňour, Zbyněk (referee) ; Žák, Michal (referee)
Current precipitation nowcasting systems primarily use the extrapolation of observed radar reflectivity. I used the extrapolation and studied limits of the forecast using the concept of the decorrelation time (DCT). I used data from two radars covering the territory of the Czech Republic from warm parts of four years and calculated DCT in dependence on several selected conditions describing the state of the atmosphere. I found that the mean DCT for the extrapolation is 45.4 minutes. On average the increase of the DCT in comparison when the persistence forecast is employed is 13.4 minutes. However, in dependence on current conditions the DCT may increase or decrease in more than 40 %. I also explored time evolution of the DCT during two storm events. I found that the DCT may significantly change in time, which is the consequence of changing character of the atmosphere during the storm development.
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Adaptive methods for singularly perturbed partial differential equations
Lamač, Jan ; Knobloch, Petr (advisor)
This thesis deals with solving singularly perturbed convection- diffusion equations. Firstly, we construct a matched asymptotic expansion of the solution of the singularly perturbed convection-diffusion equation in 1D and derive a formula for the zeroth-order asymptotic expansion in several two- dimensional polygonal domains. Further, we present a set of stabilization meth- ods for solving singularly perturbed problems and prove the uniform convergence of the Il'in-Allen-Southwell scheme in 1D. Finally, we introduce a modification of the streamline upwind Petrov/Galerkin (SUPG) method on convection-oriented meshes. This new method enjoys several profitable properties such as the ful- filment of the discrete maximum principle. Besides the analysis of the method and derivation of a priori error estimates in respective energy norms we also carry out several numerical experiments verifying the theoretical results.
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Adaptive methods for singularly perturbed partial differential equations
Lamač, Jan ; Knobloch, Petr (advisor) ; Franz, Sebastian (referee) ; Vejchodský, Tomáš (referee)
This thesis deals with solving singularly perturbed convection- diffusion equations. Firstly, we construct a matched asymptotic expansion of the solution of the singularly perturbed convection-diffusion equation in 1D and derive a formula for the zeroth-order asymptotic expansion in several two- dimensional polygonal domains. Further, we present a set of stabilization meth- ods for solving singularly perturbed problems and prove the uniform convergence of the Il'in-Allen-Southwell scheme in 1D. Finally, we introduce a modification of the streamline upwind Petrov/Galerkin (SUPG) method on convection-oriented meshes. This new method enjoys several profitable properties such as the ful- filment of the discrete maximum principle. Besides the analysis of the method and derivation of a priori error estimates in respective energy norms we also carry out several numerical experiments verifying the theoretical results.
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Ventilation of the building envelope
Šagát, Erik ; Chybík,, Josef (referee) ; Bura,, Roman (referee) ; Matějka, Libor (advisor)
The dissertation thesis is focused on non-transparent ventilated façade constructions, airflow in the ventilated cavity and the building envelope temperatures in relation with the different parameters of the construction and the ventilated cavity. The aim of this work is to optimize the temperature behavior of the building envelope during the summer season when the overheating is the most distinctive. The numerical and experimental methods with many different variants of façade constructions were used to investigation. The variants were compared and evaluated by the measured values of airflow speed in the ventilated cavity, temperature in the ventilated cavity and on the surfaces of constructions around the cavity. The result of the investigation is the evaluation of the influence of the airflow resistances or the reflectance of the surfaces around the ventilated cavity. Part of the thesis was formulated in relation with the project of MPPF - Multifunctional Plug & Play Facade during the internship at TU Graz. The efficiency of some parts of the energy active façade in this project depends on the temperature. The part of the results is the patented passive system for ventilation of building envelope and the patented cavity panel for ventilated facades.
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Tornadoes in the Czech Republic
Šáfrová, Martina ; Zacharov, Petr (advisor) ; Bližňák, Vojtěch (referee)
The Bachelor work is devoted to the task of occurance the tornado over our territory. The goal of the work is on the basis of available czech and foreing literature to make acquaintance with the pesent physique knowledge of organised convection rise and tornado formation. The second goal was to show overview of tornado rise during the last ten years and introduct several tornado rise studyings. There were calculated precursors of strong convection for these rise studyings and there values were discussed in the work. Key words: tornado, convection, precursors of convection, vorticity
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Factors determining bad thermal conditions in the Czech Republic
Venclová, Markéta ; Chládová, Zuzana (advisor) ; Pešice, Petr (referee)
This presented work deals with a weak thermal convection over the Czech Republic. The main objective is to identify areas and meteorological conditions which determined weak thermal convection in the atmosphere. Another objective is to describe surfaces and situations that are characterized with occurrence of decreasing air currents. This work may be useful for non-motorized aircraft pilots for which the occurrence of weak thermal convection and decreasing air currents will be very dangerous during the flight. In the first part there are described different ways of spreading heat through the atmosphere, this is followed by a general description of thermal convection, its distribution, origin and course. The second part deals with weak thermal convection, describes the decreasing thermal current, meteorological conditions and factors causing weak thermal convection. The third part contains the results of a questionnaire, which was sent among aeroclubs in the Czech Republic. The results of the questionnaire were compared with the information reported in the literature and in most cases they coincide. The cases which differed from the literature are more detailed in the discussion.
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Design of air heating system
Nagorskyi, Bogdan ; Baláš, Marek (referee) ; Kracík, Petr (advisor)
This bachelor thesis describes potential possibilities to substitute hot-water radiators with hot-air units with controlled air supply. Introduction part of the thesis describes basic thermal comfort factors. Subsequently, their application in traditional heating systems was performed. After that the issue of conditional heating efficiency of the original heating systems with the simultaneous application of ventilation was discussed, the analysis of which was the reason for the suitability of designing a new system of warm air heating with controlled air supply. The design of the hot-air heating system was performed for the living room of a typical panel apartment unit. During designing a new installation, the emphasis was put primarily on eliminating the main drawbacks of the hot-air heating system, namely the height distribution of the temperature layers. The system was designed in accordance with hygiene standards and its components include other air treatment elements. In the economic evaluation of the project, calculations of the possible implementation of the hot-air system and comparison with similar products commonly available on the market were made.
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Convective environment indicies and their comparison
Marek, Lukáš ; Müller, Miloslav (advisor) ; Kašpar, Marek (referee)
In this work I created the overwiew of instability indices and other characteristics of convective environment which can be found in the literature. On the basis of variables, which the instability indices are calculated from, I suggested their categorization. It was created five groups of instability indices: (i) indices of isobaric levels differences, (ii) indices of rising air parcel, (iii) indices of potential temperatures, (iv) indices of the energy potential of convection and (v) indices of wind shear. In addition to these five categories it was created the sixth category consists of other thermodynamic characteristics. In the last chapter I used the upper air soundings data and values of instability indices of the University of Wyoming for one storm in Prague and I compared instability indices to each other. The group of the indices of potential temperatures was the most successful in the storm forecast, except the Rackliff index. The bulk Richardson number from the group of indices of wind shear forecasted a supercell storm correctly. The work could be used for creation of instability climatology of the Czech Republic on the basis of the selected instability indices. Keywords: instability index, convection, convective storm
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