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Design optimization of packed bed for thermal energy storage
Krist, Thomas ; Charvát, Pavel (referee) ; Klimeš, Lubomír (advisor)
Tato diplomová práce se zabývá tématem výměny tepla v zásobníku tepla typu ”packed bed”. Cílem je popsat přenos tepla v zásobníku tepla obsahující kamínky malých průměrů, skrz který proudí horký vzduch. Toto je modelováno v prostředí MATLAB. Na začátku je krátký úvod do problematiky zahrnující ukládání tepla a jeho možné využití. Dále je uveden krátký přehled o základech přenosu tepla, typech přenosu tepla a termofyzikální vlastnosti systému vzduch-kámen. Ve třetí kapitole je představen zásobník tepla typu ”packed bed” a rozličné modely a dané podmínky jsou vysvětleny. Další kapitola se zabývá s numerickými metodami, převážně s metodou konečných diferencí použitou v této práci. Pátá kapitola se zaměřuje na obecnou optimalizaci daného problému přenosu tepla. Populačně založený metaheuristický optimalizační algoritmus zvaný Genetický algoritmus je popsán. Sestavení modelu je ukázáno v šesté kapitole, stejně jako prezentace výsledků získaných z programu MATLAB. V poslední kapitole je pak diskutován závěr a doporučení.
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Temperature Profiles Measurement of SMD Packages
Strapko, Jaroslav ; Szendiuch, Ivan (referee) ; Starý, Jiří (advisor)
Diploma thesis mainly deals with temperature management and calculation of temperature profile in oven by using SMD packages (PLCC, 1206) of different thermal capacitance on testing PCB. Above all shows theoretical consecution of temperature profile calculation in oven by using known mathematical method like the lumped capacitance method or finite difference method. Theoretical solution and measured values are compared. Diploma thesis also deals with fixation methods of thermocouples K type on assembly, comparison methods based on known and subexperiment, determines the deficiencies of methods. This thesis can perform as theoretical as well as experimental resource to prediction of temperature profiles of PCB´s with different assembly density.
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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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Modification of Navier_Stokes equations asuming the quasi-potential flow
Navrátil, Dušan ; Pochylý, František (referee) ; Fialová, Simona (advisor)
The master's thesis deals with Navier-Stokes equations in curvilinear coordinates and their solution for quasi-potential flow. The emphasis is on detailed description of curvilinear space and its expression using Bézier curves, Bézier surfaces and Bézier bodies. Further, fundamental concepts of hydromechanics are defined, including potential and quasi-potential flow. Cauchy equations are derived as a result of the law of momentum conservation and continuity equation is derived as a result of principle of mass conservation. Navier-Stokes equations are then derived as a special case of Cauchy equations using Cauchy stress tensor of Newtonian compressible fluid. Further transformation into curvilinear coordinates is accomplished through differential operators in curvilinear coordinates and by using curvature vector of space curve. In the last section we use results from previous chapters to solve boundary value problem of quasi-potential flow, which was solved by finite difference method using Matlab environment.
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Computational modeling of radial hydrodynamic bearings for water machines
Pokorný, Jan ; Šimek,, Jiří (referee) ; Návrat, Tomáš (advisor)
The aim of this thesis is to calculate the stiffness and damping coefficients for radial hydrodynamic bearings. Cylindrical and lemon hydrodynamic bearings are considered. The solution to this problem mainly depends on the hydrodynamic pressure in the bearing. The numerical solution of the Reynolds equation is used to calculate the pressure. The effect of variable viscosity and density of the lubricant due to temperature changes is considered. The static equilibrium position of the journal centre is also solved. The stiffness and damping coefficients are determined using small amplitude journal motions about the equilibrium position. Three methods for determining these coefficients are presented. The outcome of this thesis is an algorithm for the calculation of stiffness and damping coefficients for cylindrical and lemon bearings. Results for lemon bearings are presented and comparison with the commercial software DynRot BR is made. The benefit of this thesis is the creation of an algorithm for the calculation of journal centre equilibrium position, a new way of incorporating the temperature changes in the viscosity and the density of the lubricant, and the modification of a method for calculating stiffness and damping coefficients based on experimental analogy.
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Optimization in engineering problems
Klepáč, Jaromír ; Popela, Pavel (referee) ; Mrázková, Eva (advisor)
This bachelor thesis deals with optimization in engineering problems. In particular, it focuses on a task of optimal dimensions design of continuously loaded beam with specic requirements on nal beam weight and rigidity. For the purpose of well understanding of all the terms used during solving of an illustrative task, the thesis contains a brief introduction into the optimization problems, ordinary dierential equations, and theory of elasticity as well. Results obtained through optimization in the GAMS software will be checked by analytic solution and compared with an alternative calculation in the ANSYS software.
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Techniques of time-domain analysis of interconnects.
Lábsky, Balázs ; Petržela, Jiří (referee) ; Brančík, Lubomír (advisor)
This work deals with techniques of time-domain analysis of interconnects. After a studying crucial issue of time-domain analysis of interconnects methods of modeling and simulation simple interconnects in electrotechnics are described. For transient effect analysis two elementary methods can be used: the state variable method and the FDTD (Finite - Difference Time - Domain) method. The FDTD method can be used to solve partial differential equations in time domain, for instance equations of transmission lines. The method is very effective and delivers satisfactory results in case of linear and non-linear lines with a single “live” conductor. The method can be easily programmed in Matlab.
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The Selected Stochastic Programs in Engineering Design
Čajánek, Michal ; Mrázková, Eva (referee) ; Popela, Pavel (advisor)
Two-stage stochastic programming problem with PDE constraint, specially elliptic equation is formulated. The computational scheme is proposed, whereas the emphasis is put on approximation techniques. We introduce method of approximation of random variables of stochastic problem and utilize suitable numerical methods, finite difference method first, then finite element method. There is also formulated a mathematical programming problem describing a membrane deflection with random load. It is followed by determination of the acceptableness of using stochastic optimization rather than deterministic problem and assess the quality of approximations based on Monte Carlo simulation method and the theory of interval estimates. The resulting mathematical models are implemented and solved in the general algebraic modeling system GAMS. Graphical and numerical results are presented.
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