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Electrodynamic forces acting on moving contact of electrical apparatus
Šic, Pavel ; Valenta, Jiří (referee) ; Bušov, Bohuslav (advisor)
This master’s thesis is focused on calculation, simulation and experimental verification of electrodynamic forces acting upon movable contact piece of MCCB and experimental current carrying path. A short description of low voltage circuit breakers is briefly discussed in first chapter. Second chapter is focused upon contact system analysis of particular MCCB with thermomagnetic trigger. A hardness of contact materials is briefly described. A detailed analytical calculations were used to determine electrodynamic forces in MCCB. A FEM simulation in ANSYS Maxwell was carried out for comparison with analytical results. An experimental apparatus was designed and built for verification of constriction repulsion force, so called Holm’s force. A series of measurements is subsequently performed on proposed apparatus and results are compared with results from previous chapters.
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Analysis of material properties of composite boards based on cement and organic fibers in relation to its use in the design of interior staircases
Nespěšný, Ondřej ; Schmid, Pavel (referee) ; Pěnčík, Jan (advisor)
Cement-based composite boards reinforced by organic fiber, commonly known as cement fiber boards are universal and environmental material. Nowadays they are commonly used in construction industry in the form of facade facing for ventilated facades, interior and exterior ceilings or as a lost formwork for the bridge constructions. In these ways of using the cement fiber boards are strained mainly perpendicularly to their median plane. Material characteristics for this kind of strain are declared by the manufacturers. This diploma thesis is focused on ways of using the cement fiber boards reinforced by organic fiber as prefabricated, constructional material for interior staircases. In this case, every segment is strained even in its median plane. This way of strain is atypical and is not declared by the manufacturers in the manufacturer's technical sheets. The main goal of the diploma thesis was to experimentally determine the material characteristics in relation to the possibility of using the cement fiber boards reinforced by organic fiber for the construction of interior stairways. Material characteristics were determined by using Czech technical standards and information from professional literature. Testing tools made by 3D printing were used in the measurements. The possibilities of connecting cement fiber boards by mechanical and glued joint were checked out. The trial “stand” from CLT boards was designed for the real testing of single-arm and double-arm staircases. The outcomes of the experimental measurements confirmed the possibility to use the cement fiber boards for interior stairways. It is necessary to support the design of the staircase by static calculations and to respect the design of the dimensions of the individual segments in the implementation.
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Complex analysis of the performance of a U-type distribution system
Sýs, Tomáš ; Strouhal, Jiří (referee) ; Babička Fialová, Dominika (advisor)
Fluid flow maldistribution plays a key role in equipment used in process and energy industries, although its evaluation is often underestimated or fully neglected. Uneven flow distribution may cause thermal or mechanical load on the tube bundle, and in extreme scenarios, it can also have an adverse effect on the process efficiency. This thesis aims to find the optimal computational tools for flow distribution prediction suitable for the initial stage of the equipment design process and to identify suitable settings of these tools for their subsequent industrial deployment. The results of simplified analytical models, detailed numerical simulations, and experimental measurements were compared for the dividing header and the U-type distribution system. It was found that the results provided by simplified mathematical models, the solution of which is also significantly less time-consuming compared to detailed CFD simulations, best correspond to the measured experimental values in all modeled configurations. For arrangements with higher lateral resistance coefficient, both computational approaches provide approximately equally accurate results. However, for arrangements with lower lateral resistance coefficient, the deviation of the results obtained by CFD calculations from the experimental data is significantly larger.
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Design of the magnetically sensitive hydrodynamic bearing for the experimental rotor rig
Ferfecki, P. ; Zapoměl, Jaroslav ; Molčan, M.
In a hydrodynamic bearing, the relative motion between the rotating shaft and stationary housing is separated by a thin film of a lubricant. The magnetically sensitive lubricants with the promise of a semiactive control are able to improve the vibration response of the rotor system supported by the hydrodynamic bearings. A design of the magnetically sensitive hydrodynamic bearing is briefly introduced in this paper. The presented experimental rotor rig is proposed to analyse the large range of load conditions and rotational speeds of the bearing. The designed hydrodynamic bearing is intended to test the ferrofluids, magnetorheological oils, and nano-micro composite magnetic fluids. The apparent viscosity of the magnetically sensitive lubricant is altered by the magnetic field generated by the electric coil and thus the position of the bearing journal is shifted. The experimental measurement results show that the rheological behaviour of the lubrication layer with a magnetorheological fluid is significantly influenced by a magnetic field. The raising magnitude of the current in the electric coil leads to an increase in the bearing's load performance.
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Condensation heat transfer of water steam on cylindrical wall
Horká, Lucie ; Bašta,, Jiří (referee) ; Kabele,, Karel (referee) ; Hirš, Jiří (advisor)
The doctoral thesis is aimed at condensation heat transfer of water steam on a cylindric wall. This physical phenomenon of water steam condensation is examined and published in leading scientific journals for more than 100 years. The main aim of the doctoral thesis is study of the water steam condensation on a cylindrical wall. The result of the doctoral thesis is the theoretical and experimental determination of the heat transfer coefficient during the water steam condensation on the cylindrical wall. This coefficient is a basic parameter of design of all the thermal devices, which use the condensation heat of water steam in technical practice.
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Determination of measurement uncertainty of a coordinate measuring machine in nanometrology
Potanko, Andrej ; Jankových, Róbert (referee) ; Šrámek, Jan (advisor)
The diploma thesis deals with the determination of measurement uncertainty on coordinate measuring machines in the field of nanometrology. These are SIOS NMM 1 and Zeiss UPMC 850 Carat machines, which are used at the CMI workplace in Brno. In the theoretical part, the work is devoted to basic terminology in the field of measurement and general characteristics of coordinate measuring machines. The theoretical part concludes with a description of the devices used for measurement. In the practical part, experimental measurements are performed on both devices with subsequent identification and quantification of individual components of uncertainties affecting the measurement. The last part of the thesis is devoted to the overall evaluation of measurements on Zeiss and SIOS devices and their metrological comparison.
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Complex analysis of the performance of a U-type distribution system
Sýs, Tomáš ; Strouhal, Jiří (referee) ; Babička Fialová, Dominika (advisor)
Fluid flow maldistribution plays a key role in equipment used in process and energy industries, although its evaluation is often underestimated or fully neglected. Uneven flow distribution may cause thermal or mechanical load on the tube bundle, and in extreme scenarios, it can also have an adverse effect on the process efficiency. This thesis aims to find the optimal computational tools for flow distribution prediction suitable for the initial stage of the equipment design process and to identify suitable settings of these tools for their subsequent industrial deployment. The results of simplified analytical models, detailed numerical simulations, and experimental measurements were compared for the dividing header and the U-type distribution system. It was found that the results provided by simplified mathematical models, the solution of which is also significantly less time-consuming compared to detailed CFD simulations, best correspond to the measured experimental values in all modeled configurations. For arrangements with higher lateral resistance coefficient, both computational approaches provide approximately equally accurate results. However, for arrangements with lower lateral resistance coefficient, the deviation of the results obtained by CFD calculations from the experimental data is significantly larger.
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Analysis of material properties of composite boards based on cement and organic fibers in relation to its use in the design of interior staircases
Nespěšný, Ondřej ; Schmid, Pavel (referee) ; Pěnčík, Jan (advisor)
Cement-based composite boards reinforced by organic fiber, commonly known as cement fiber boards are universal and environmental material. Nowadays they are commonly used in construction industry in the form of facade facing for ventilated facades, interior and exterior ceilings or as a lost formwork for the bridge constructions. In these ways of using the cement fiber boards are strained mainly perpendicularly to their median plane. Material characteristics for this kind of strain are declared by the manufacturers. This diploma thesis is focused on ways of using the cement fiber boards reinforced by organic fiber as prefabricated, constructional material for interior staircases. In this case, every segment is strained even in its median plane. This way of strain is atypical and is not declared by the manufacturers in the manufacturer's technical sheets. The main goal of the diploma thesis was to experimentally determine the material characteristics in relation to the possibility of using the cement fiber boards reinforced by organic fiber for the construction of interior stairways. Material characteristics were determined by using Czech technical standards and information from professional literature. Testing tools made by 3D printing were used in the measurements. The possibilities of connecting cement fiber boards by mechanical and glued joint were checked out. The trial “stand” from CLT boards was designed for the real testing of single-arm and double-arm staircases. The outcomes of the experimental measurements confirmed the possibility to use the cement fiber boards for interior stairways. It is necessary to support the design of the staircase by static calculations and to respect the design of the dimensions of the individual segments in the implementation.
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The influence of moisture on the thermal properties of the gloves
Janíčková, Žaneta ; Toma, Róbert (referee) ; Fišer, Jan (advisor)
This diploma thesis is focused on the assessment of the influence of moisture on the thermal properties of the gloves. The first part of the thesis deals with the research of topics related to the given issue as well as with the derivation of the computational relations needed for evaluation of experimental measurements. The main focus of the work lies on defining the hypotheses and experiments that are used to verify the influence of moisture on the thermal resistance of gloves. As for the experimental part, it describes the individual methods of moistening the gloves from which the moistening through the air humidity and the moistening by the immersion were analysed. To verify the suitability of selected moistening methods, the tested glove samples were measured on the thermal manikin both in a dry and a moistened state under the conditions defined by ČSN EN 511 and ČSN EN ISO 15831 standards. Individual states were repeatedly measured and afterwards the progresses of thermal resistance depending on time were graphically displayed. The thesis also includes analysis of measurement uncertainties as well as evaluation of measurement repeatability. From the obtained results, both the defined hypotheses and theoretical assumptions about the decrease of the thermal resistance of a textile material due to the influence of moisture were confirmed in the conclusion of the diploma thesis.
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