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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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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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Model predictive Control for continuous casting of steel
Zemanová, Hana ; Mauder, Tomáš (referee) ; Štětina, Josef (advisor)
In this thesis an equation of heat conduction including phase and structural changes is derived, involving various boundary conditions. It seems to be the most suitable to calculate the equation by enthalpy method. In this equation not only enthalpy occurs, but also the temperature, and in consequence the relationship between these variables is quite complicated. In this paper I use the values measured or calculated using solidifcation models. The calculation is implemented in Matlab Simulink, which is a very popular blocks scheme in common practice of regulation. The calculation is based on steady state set up with help of experts and as a result, the program could be put into practice. The program calculates the intensity of cooling according to the initial casting speed, casting inlet temperature and the desired temperature curves. The rate of inuence of cooling can be changed according to the given criteria. The thesis compares the surface temperatures and cooling in the case of a predictive controller is or is not applied in the program.
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Heuristic Algorithms in Optimization
Komínek, Jan ; Šeda, Miloš (referee) ; Roupec, Jan (advisor)
This diploma thesis deals with genetic algorithms and their properties. Particular emphasis is placed on finding the influence of mutation and population size. Genetic algorithms are applied on inverse heat conduction problems (IHCP) in the second part of the thesis. Several different approaches and coding methods were tested. Properties of genetic algorithms were improved by definition of two new genetic operators – manipulation and sorting. Reported theoretical findings were tested on the real data of inverse heat conduction problem. The library for easy implementation of GA for solving general optimization problems in C ++ was created and is described in the last chapter.
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Selection of suitable fluid flow directions in laminar flow tubular cooler
Krobot, David ; Kohoutek, Josef (referee) ; Jegla, Zdeněk (advisor)
This master’s thesis is devoted to problematic of selection of suitable flow directions in double pipe heat exchanger. First chapter is oriented to the construction of tube heat exchangers. It is also discussed impact of construction solution to the flow character and changing of his process parameters. The difference between parallel and countercurrent flow is also occurred in this parts. The next chapter is focused to the basics of heat-hydraulic calculations of heat exchanger. This also means explanation of ways of heat transfer and heat exchanger function. There are told about specific access to the solving problem of fluid laminar flow. The third chapter is detailed focused to the calculating of heat exchanger. At first is discussed factors, which have impact to the flow character. Next are detailed descriptions of design and controlling calculations, including more alternative ways to solve it. Next chapter exploit those results for deciding, which flow arrangement will be better for given case. Last chapter contain realization and reformulating of process heat exchanger calculating to the program code in Maple. There is also description of used algorithms and operating with them, so any user could be able to work with it. In this master’s thesis are used many examples from attached programs on different parts.
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Flow sensor
Symerský, Tomáš ; Psota, Boleslav (referee) ; Kosina, Petr (advisor)
This diploma thesis is divided into two parts - theoretical and practical. In its first, theoretical part, deals with the theory of fluid and gas flow, heat transfer and diversification of sensors for flow measurement working on the electrical principle. It also deals with thermodynamic principle, which can be used for measuring very small flow and low-temperature ceramics that is used to implement microcanals for sensing very low flows. The practical part of the thesis deals with the very simulation of the entire structure in the program “COMSOL Multiphysics” - both in 2D and 3D views. Then there is shown the implementation and measurement of the flow sensor in a low-temperature ceramics, working on a thermodynamic principle.
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The finite element method for problems of heat transfer
Čupr, Pavel ; Chabičovský, Martin (referee) ; Štětina, Josef (advisor)
The study is focused on the research of heat transfer problems when assessing building constructions. It contains an overview of heat transfer theory, basic principles of method of advanced composites (MAC) and an outline of currently available MAC programmes based on open code. It researches the building constructions in terms of the heat transfer. The assignment uses analytical and numerical modelling of Ansys programme. Finally, acquired results have been compared and building constructions have been studied with regard to acceptability of different sets of temperatures.
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