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Heat transfer solution of solidifying steel system with phase change with moving edge conditions
Fedorko, Tomáš ; Mauder, Tomáš (referee) ; Štětina, Josef (advisor)
Cílem diplomové práce je vytvoření 2D numerického modelu pohybujícího se řezu s proměnnými okrajovými podmínkami skutečné geometrie plynulého odlévání a chlazení předlitku v prostředí MATLAB. Model se zabývá vysoce nelineárními termofyzikálními podmínkami oceli během tuhnutí a chlazení. V práci je simulovaná nejen nelinearita termofyzikálních podmínek, ale také nelinearita při fázové změně. Fázová změna je modelovaná pomocí metody entalpie, metody zdánlivé kapacity a metody teplotního zotavení. Všechny výsledky práce jsou porovnány z více hledisek, jako např. z hlediska přesnosti, rychlosti výpočtu, nebo vhodnosti časového diskretizačního kroku pro nelineární problémy, a paralelizace.
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Investigation of Functional Properties of Thin NiTi Filaments for Applications in Smart Structures and Hybrid Textiles
Pilch, Jan ; Dlouhý, Antonín (referee) ; Heczko,, Oleg (referee) ; Pokluda, Jaroslav (advisor)
PhD thesis focuses the field of textile application of modern functional materials, namely metallic shape memory alloys with unique thermomechanical properties deriving from martensitic transformation in solid state. Particularly, it deals with the development of a nonconventional thermomechanical treatment of thin NiTi filaments via Joule heating by electric current and related basic research involving thermomechanical testing and modeling of functional properties of the filaments, investigation of martensitic transformations and deformation processes in NiTi and investigation of the fast recovery and recrystallization processes in metals heated by short pulses of controlled electric power. The method was developed and called FTMT-EC. In contrast to conventional heat treatment of metallic filaments in environmental furnaces, this method allows for precise control of the raise of the filament temperature and filament stress during the fast heating (rate ~50 000 °C/s). As a consequence, it is possible to precisely control the progress of the fast recovery and recrystallization processes in heat treated filaments. In this way it is possible to prepare filaments with desired nanostructured microstructure and related functional properties. A prototype equipment for application of the method for heat treatment of continuous SMA filaments during respooling in textile processing was designed and built. Comparing to the conventional heat treatment of SMA filaments in tubular environmental furnaces, this approach is faster, saves energy and allows for preparation of filaments with special functional properties. International patent application was filed on the method. It is currently utilized in the research and development of smart textiles for medical applications.
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Investment casting waxes and measurements of their properties with regard to simulation software
Bochníček, Štěpán ; Mikulka, Vít (referee) ; Kosour, Vojtěch (advisor)
Today, the use of simulations is increasing in order to reduce cost and complexity of production and also to prevent product defects. For this purpose, we use simulation programs, such as ProCAST. This program is designed for simulation of casting parts. In my bachelor thesis I focused on the methods of casting lost wax, where the model is made of wax mixture. In each simulation we have to obtain and specify the properties of the material to casting. I described these properties and methods of measurement in this bachelor thesis.
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Calculation of the heat balance of latent heat utilization of flue gases by means of a condenser
Toman, Filip ; Baláš, Marek (referee) ; Pospíšil, Jiří (advisor)
Thesis is focused on calculation of the condenser of flue gas, which is created by burning of natural gas. In the first part is theoretical overview of equations describing film condensation and physical properties of the flue gas. The second part deals with practical thermal calculation of the specified condenser. In third part parametric study is done in which a tempature of cooling water at inlet and the coefficient of excess air are changed. The last part of the thesis is dedicated to geometric design of the flue gas condenser whose required power is 8 MW.
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Creation of laboratory tasks for Selected topics from renewable energy sources and energy storage
Vaněček, Lukáš ; Vaněk, Jiří (referee) ; Bača, Petr (advisor)
This master‘s thesis contains a comprehensive laboratory task about saving a heat energy with a use of changing a state of matter. The thesis is written for the object Chosen passages of renewable resources and saving a heat energy. Part one presents a theoretical part of the topic, terminology and relations needed to make this laboratory work. It also contains a created procedure of partial tasks necessary to take laboratory measurements. The second part of the thesis is about measuring and evaluation of acquired values according to procedure described in the theoretical part of the thesis. Different variations considered during the creation of measuring procedure are also named here. The final part of the thesis describes a laboratory equipment necessary to complete the task and an example of filled protocol is attached.
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Design and optimization of temperature fluctuation dumper with latent heat thermal energy storage
Kozubík, Lukáš ; Charvát, Pavel (referee) ; Klimeš, Lubomír (advisor)
The goal of this master’s thesis is creating a model of the attenuation of the fluid temperature fluctuations using methods described in the thesis. PCM is used to attenuation of fluctuations. This thesis is example of utilization PCM in technical practice. Numerical calculation of PCM phase change uses the method of effective heat capacity and enthalpy method. A part of this thesis also forms a theoretical basis for heat transfer described by differential equations. The final part of the thesis is dedicated to the optimization of the model and the description of the optimization methods.
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Comparison of various approaches to evaluation of tree energetic balance
Tomková, Alžběta ; Pokorný, Jan (advisor) ; Lhotáková, Zuzana (referee)
The thesis deals with the tree energetic balance closely related to the phenomenon of plant transpiration. Living systems have a unique ability to equilibrate gradients in the nature. Storing energy of the incoming solar radiation into a latent heat of water evaporation is an example of such tree feature. It dissipates energy and simultaneously recycles nutrients and water in the ecosystem. There are few possible ways of energy balance detection shown in this work. The thermal imagining can be used as a method for an indirect indication of transpiration - transpiring plants have lower leaf surface temperature. An alternative method for determining the rate of transpiration is a direct measurement of transpiration on leaves or transpiration flow in a tree trunk. However, extrapolation of the above mentioned methods to entire stands can encounter some difficulties. The first part of the thesis presents a description of a physical background of energetic processes and the ways in which plants operate with water, the biotic pump theory is being discussed. The practical part begins with experiments on single leaves. These experiments are carried out to test the usability of the methods for the following experiments, which are performed on the entire living trees. They are focused on the relationship of the...
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Latent heat effect on slab deformation in the Earth mantle
Pilař, Štěpán ; Čížková, Hana (advisor) ; Běhounková, Marie (referee)
Lithospheric plates move relative to each other with velocities of several cm/year. In subduction zone, one plate slides (subducts) under the other. Slabs are being deformed while subducting to the Earth's mantle. The subduction is influenced by phase tran- sitions of the mantle material at the depths of 410 km and 660 km. Here, we used a two-dimensional numerical model of subduction to evaluate the influence of latent heat released or absorbed during these phase transitions on the subduction process. We ex- amined the influence of latent heat alongside the influence of other parameters - age of the slab (50 - 150 million years), yield stress inside the slab (2 · 108 − 5 · 108 Pa) and viscosity of the crust (1020 −1021 Pa s). Latent heat released during an exothermic phase transition at the depth of 410 km heats up the slab by 50 - 90 K, reduces the density anomaly with respect to the surrounding mantle and slows down the slab. At the same time, the viscosity of the slab is lowered and the slab deforms more easily in the transi- tion zone due to the endothermic phase transition at the depth of 660 km and a viscosity resistance of a stiffer lower mantle. The stress inside a slab is therefore lowered, which may influence deep earthquakes. When it comes to the other parameters, age of the slab changes the...
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