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Description unsteady operating conditions of siphon swirl turbine
Krejčiřík, Stanislav ; Habán, Vladimír (referee) ; Hudec, Martin (advisor)
The master´s thesis focuses on the behavior of the siphon turbine during unsteady flow. There are two possible conditions. The first condition involves commissioning the turbine. In this situation turbine works like a pump. In the second case, it includes shutting down the turbine by aerating the siphon and thereby breaking the water column. This thesis deals with the second case, where the results of the experiment and the mathematical model are compared.
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Influenc of Instability to Critical Heat Flux
Khůlová, Jitka ; Vojáčková, Jitka (referee) ; Suk, Ladislav (advisor)
This bachelor's thesis is elaborating about two-phase flow in the heated channel. It describes flow instabilities and their influence to critical heat flux. The calculation methods of two-phase flow are introduced. The homogeneous equilibrium method is selected for the practical part. The results are evaluated and possible solution to prevent flow instabilities is suggested.
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Vizualization and optical measurements of two-phase flows for pressure-swirl atomizer
Janáčková, Lada ; Lízal, František (referee) ; Jedelský, Jan (advisor)
Tato práce se zabývá studií Simplex a SR verze původní trysky používané ve spalovací komoře malého proudového motoru. Pro lepší porozumění procesu rozprašování byl vyroben transparentní model obou trysek v měřítku 10:1. Tvorba spreje u tlakové vířivé trysky je komplexní proces dvoufázového proudění. Vnitřní a vnější proudění bylo zkoumáno pomocí Laserového Dopplerovského Anemometru a vysokorychlostní kamery při vstupních tlacích p = 0.5, 1.0 a 1.5 MPa s použitím kerosinu a p-Cymenu. Z hlediska vnitřního proudění byla provedena charakteristika vzdušného jádra a zkoumán vliv různých SFR hodnot na délku a průměr jádra. Dále byly objasněny rychlostní profily společně s jejich fluktuačními složkami vzhledem k Reynoldsovu číslu a použité kapalině. Také jednoduchý numerický model byl vyvinut k odhadu vnitřního proudění pomocí trackování částic. V případě vnějšího proudění byl zkoumán vliv vstupního tlaku na rozpadovou vzdálenost spreje a úhel kužele spreje.
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Modeling of cavitating flow
Frölich, Kamil ; Klas, Roman (referee) ; Rudolf, Pavel (advisor)
his thesis deals with the problems of cavitation flow in a Venturi tube. It is made for a multi-phase (water-vapour) flow calculation of two geometry tubes. Results of numerical calculations for the flow geometry (dimensions) are compared with performed experiment. Numerical flow calculation was performed in the Fluent 2.3.26.
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Experiments critical heat flux
Štaffa, Petr ; Martinec, Jiří (referee) ; Suk, Ladislav (advisor)
The Bachelor’s thesis deals with phenomenon of critical heat flux in a core of nuclear reactor. The first part is dedicated to describe physical nature of critical heat flux and basic thermo mechanical and hydrodynamics terms. The second part is dedicated to summarize experimental investigations on critical heat flux and their process.
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Large Eddy Simulation of Turbulent Two-Phase Flow
Volavý, Jaroslav ; Fürst, Jiří (referee) ; Vimmr, Jan (referee) ; Jícha, Miroslav (advisor)
Doctoral thesis deals with the numerical simulations of two-phase flows, especially with prediction of movement of dispersed phase (particles) carried by fluid. The Euler-Lagrange approach was applied for description of the system fluid-particles. It means that the fluid is considered to be continuum and its movement is described using Euler approach. Particles are regarded as mass points and their movement is solved using Lagrangian approach. The Large Eddy Simulation method was adopted for solution of the fluid flow. The series of simulations of the backward-facing step flow laden with particles were performed. The concentration of the particles in the flow was high enough for consideration of the influence of particles on the turbulence of the carrier phase. The developed scheme for generation of turbulence on the inlet is applied. The influence of anisotropic decomposition of subgrid energy on movement of particles was studied in the frame of this work.
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Critical Heat Flux on Smooth and Modified Surfaces
Suk, Ladislav ; Kolat, Pavel (referee) ; Katovský, Karel (referee) ; Fiedler, Jan (advisor)
This thesis deals with the problem of critical heat flux (CHF) on technically smooth and treated surfaces at low pressures. The theoretical part presents the basic concepts of two-phase flow and an analysis of existing work on the influence of the surface on CHF. The main part of the work describes the built experimental apparatus for CHF research at low pressures of 100 -1500 kPa (1-15 bar) with a vertical internally heated annular test section. The internal annuli consists of an outer glass tube with an inner diameter of 14.8 mm and an inner tube made of Inconel ™ 625 / Optimized ZIRLO ™ with an outer diameter of 9.14 mm and a heated length of 380/365 mm. CHF experiments on technically smooth surface were performed at outlet pressures 120 kPa, 200 kPa and 300 kPa, at an inlet temperature of 64, 78 and 91 °C and at mass flux of 400, 500, 600 and 800 kg / m2s. The Inconel tubes were tested in two different surface modifications - abraded and bead blasted. Experiments were performed at mass flows of 400, 500 and 600 kg / m2s. The total number of 122 experimental runs were conducted and the results were compared with other literature experimental data. The maximum increase of CHF on abraded / bead blasted tube was 18.12% / 16.17%. The surface structure was analysed by laser microscopy. The wetting behaviour of the surface structures was measured by the sessile drop method. The elemental analysis of the surface was evaluated using the EDS method.
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Modeling two-phase bubble flow in microfluidics
Stehlík, Martin ; Kozák, Jiří (referee) ; Rudolf, Pavel (advisor)
The goal of submitted thesis is to perform a computer simulation of bubble creation in T-channel. In the first section of the paper, the theoretical applications of microfluidic bubble, micromachines and droplet formation are described. In the second part of the text, author uses cross flowing method for simulation od bubble creation. Furthermore, several settings in computer simulation software Fluent are mentioned. In addition, the influence of velocity at the T-channel inlet on surface tension and on bubble length is presented.
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Critical Heat Flux on Smooth and Modified Surfaces
Suk, Ladislav ; Kolat, Pavel (referee) ; Katovský, Karel (referee) ; Fiedler, Jan (advisor)
This thesis deals with the problem of critical heat flux (CHF) on technically smooth and treated surfaces at low pressures. The theoretical part presents the basic concepts of two-phase flow and an analysis of existing work on the influence of the surface on CHF. The main part of the work describes the built experimental apparatus for CHF research at low pressures of 100 -1500 kPa (1-15 bar) with a vertical internally heated annular test section. The internal annuli consists of an outer glass tube with an inner diameter of 14.8 mm and an inner tube made of Inconel ™ 625 / Optimized ZIRLO ™ with an outer diameter of 9.14 mm and a heated length of 380/365 mm. CHF experiments on technically smooth surface were performed at outlet pressures 120 kPa, 200 kPa and 300 kPa, at an inlet temperature of 64, 78 and 91 °C and at mass flux of 400, 500, 600 and 800 kg / m2s. The Inconel tubes were tested in two different surface modifications - abraded and bead blasted. Experiments were performed at mass flows of 400, 500 and 600 kg / m2s. The total number of 122 experimental runs were conducted and the results were compared with other literature experimental data. The maximum increase of CHF on abraded / bead blasted tube was 18.12% / 16.17%. The surface structure was analysed by laser microscopy. The wetting behaviour of the surface structures was measured by the sessile drop method. The elemental analysis of the surface was evaluated using the EDS method.
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