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Solidification of castings by pouring into shell moulds in vakuum furnaces
Odložil, Jan ; Ňuksa, Petr (referee) ; Roučka, Jaromír (advisor)
Heat transfer during metal pouring and its solidification in the vacuum furnace have been investigated by experiments using model set of castings of different diameters and insulations. The pouring metal was Inconel 713LC alloy based on nickel. The found data have been used for optimization of the numerical simulation of the thermal regime during the both pouring and solidification phases of the process in vacuum. Numerical simulation of the alloy structure in individual castings has been made by the CAFE module of the ProCast software and obtained results compared with the real structure. The optimized boundary conditions can be used for simulation of real castings.
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Heat transfer on sprinkled tube bundle
Copek, Tomáš ; Pospíšil, Jiří (referee) ; Kracík, Petr (advisor)
This bachelor thesis named Heat transfer on sprinkled tube bundle deals with experimental assesment of heat transfer coefficient on sprikled tube bundle. Its goal is to measure, compare and evaluate values and trends of heat transfer coefficient on external surface according to flow rate of cooling water. Evaluation will be focused on size of pitch between tubes, type of tubes surface and influence of temperature gradient. Measurement was ongoing at atmospheric pressure. Warm water flowing in tube bundle is cooled by cold sprinkling water. Tube bundle consists of ten tubes located horizontaly beneath each other with smooth, grooved or sanblasted surface. Distance between tubes vary from 15 to 35 milimetres. Measurement of two temperature gradients 15-40 and 15-45 (15°C is temperature of sprinkling water in distribution tube; 40°C or 45°C is temperature of water entering the tube bundle) is carried out for each pitch and tube surface.
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Thermal Mass Flowmeter
Mlčoch, Albert ; Kunz, Jan (referee) ; Beneš, Petr (advisor)
The thesis deals with verification of the mathematical model of a thermoanemometric sensor of water flow according to the King's equation. The model and measuring apparatus are briefly described. The paper deals mainly with measurement and its evaluation. The model is gradually modified depending on the measured data. The measurement evaluation summarizes the current knowledge and measurement accuracy of a modified sensor model. Another part of this paper deals with the simulation of observed processes in COMSOL Multiphysics simulation software, how this software works and its outcomes. In the final part of this paper, the electronic circuit of the sensor is designed.
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Optimization of Cooling Synchronous Machine
Makki, Zbyněk ; Rafajdus,, Pavol (referee) ; Kačor,, Pavol (referee) ; Janda, Marcel (advisor)
The main goal of doctoral thesis is optimization cooling of the synchronous machine. Problem is solved based on the finite element method with use of ANSYS software. Work is built up from theoretical part where is comparison of base equations for heat transfer and simulations for several models. Next part shows us two methods how simulate free and force convection. Depends on the better method from the previous two methods is used for next calculations with several algorithm which are used for find of best parameters for synchronous machine. Our control parameter is mass flow rate.
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Stirling engine 3kW combustion chamber
Matuška, Petr ; Zháňal, Lubor (referee) ; Kaplan, Zdeněk (advisor)
This thesis deals with the construction proposal of the combustion chamber of Stirling engine. The introduction briefly describes the history and practical application of Stirlinova engine today. The following section explains the differences between theoretical and real cycle and the principle of beta Stirling engine modifications. The next section is devoted to the calculation of fuel and air consumption and fuel compared to each other. The proposed design is based not only on the calculation of fuel and air, but also heat transfer between flue gas and preheated air. The last part is devoted to calculating the flow of LPG and flow model of the combustion chamber.
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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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The heat dissipation efficiency of the steam generator Dukovany at low water levels
Veselý, Jakub ; Šnajdárek, Ladislav (referee) ; Pospíšil, Jiří (advisor)
The goal of this thesis is to simulate the course of events during Dukovany Nuclear Power Plant blackout and to determine the optimal process of cooling down the cold branches of the primary circuit loops to secure the maximum amount of the primary fuel needed for the residual heat outlet so that the operating staff has as much time as possible for renewing the electric power supply. The first part of the thesis describes nuclear power plants built in the Czech Republic and in the world as well as reactor blocks whose construction is being considered. The detailed description of Dukovany’s steam generator is shared in chapter three. Following chapter summarizes blackouts that occurred at power plants around the world, events that might have led to blackouts in the Czech Republic, and it also describes current approach to blackout problematics at Dukovany Nuclear Power Plant. Chapters six and seven contain the core of the thesis. That includes detailed description of a mathematical model explaining the behaviour of a reactor block during blackout as well as the analysis of the results found.
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Thermal calculation of direct fired heater
Sénáši, Martin ; Kilkovský, Bohuslav (referee) ; Jegla, Zdeněk (advisor)
The main aim of the thesis is to evaluete properties of a simplified thermal calculation of the direct fired heater published in the journal Applied Energy at 2010 and its application to specific industrial cases. At first, general issues of process heaters are talk over. Second, calculation model in cited article is briefly introduced. After that, custom computational model at program Maple is created in accordance with published article. Subsequently, the model is applied to the existing process furnaces in the form of a check calculation. An integral part of the work is also a detailed discussion of the results obtained.
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Indirect air heating
Beneš, Josef ; Adam, Pavel (referee) ; Počinková, Marcela (advisor)
The master Thesis deals with indirect air heating in air handling units. In the theoretical part of the thesis the categories of heat exchangers are defined according to their positioning in ventilation system, used material and type of heat transfer fluid. To the issue of calculating heat exchanges through heat exchangers and description of different kinds of regulation of primary heat transfer fluid is dedicated a separate chapter. The experimental part of the thesis deals with determining performance of current air heat exchanger at set thermal gradient with various heat transfer fluids. In the calculating part of the Thesis, based on measured values, are suggested two possible solutions for use of technological waste heat. Final evaluation of particular solutions was based on the criterion of efficiency usage and implementation investment costs.
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Tubular minichannel heat transfer coefficient measurement
Snášel, Jan ; Kamenský, Petr (referee) ; Hejčík, Jiří (advisor)
The master’s thesis is describing measurement of heat transfer coefficient for heat exchanger with tubular minichannels. For understanding of the process, basic theory of heat transfer has its part in this work. The advanteges of minichannels and their clasiffication are also stated here. Another part describes the calculation for determination of heat transfer coefficient using the Wilson plot method and the method of direct determination of heat transfer coefficient. Measurement data are evaluated and comparison is made for results of both methods. This results are used for formulation of correlation equation for given flow regime.
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