National Repository of Grey Literature 252 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Spectroelectrochemistry of 1,10-phenantrolines Substituted by Pyrrolidine and Phenothiazine Redox-active Units
Sokolová, Romana ; Wantulok, J. ; Fiedler, Jan ; Nycz, J. ; Degano, I.
Compounds based on 1,10-phenanthroline (Phen) and their complexes are used in many fields, such as a stabilizing agent in the synthesis of nanoparticles, catalysts in homogeneous catalysis and as a semiconductor in organic light-emitting diodes (OLED) due to their coordination abilities. In this work, 1,10-phenanthrolines functionalized by pyrrolidine and phenothiazine units were studied by electrochemical methods. Cyclic voltammetry resulted in several oxidation and reduction voltammetric peaks. Structure-activity relationship was investigated using in situ spectroeletrochemistry, spectrophotometry, infrared spectroscopy and chromatography.
Changes in biological monitoring of running waters using benthos with respect to diatoms
Fiedler, Jan ; Kulichová, Jana (advisor) ; Tichá, Anna (referee)
This work focuses on the development of a methodological approach to biomonitoring of running waters using benthic organisms. It discusses the development from methods focused on determining organisms by their external appearance to modern biomonitoring based on the determination of organisms by eDNA metabarcoding. Modern metagenomic methods (genomics, transcriptomics, metabolomics and proteomics) are also mentioned. This thesis compares the development of ecological status assessment of freshwater ecosystems using diatoms and invertebrates. It also describes the common points of their methodological development. Another outcome of the comparison is information on which hydrochemical and geochemical environmental factors can be easily monitored by diatoms and which by macroscopic invertebrates. Furthermore, a prognosis for the further development of biomonitoring is mentioned in the conclusion. It is formulated as a synthesis of traditional methods based on morphological species determination, biomonitoring 2.0 (using eDNA metabarcoding) and metagenomic methods. Key words: autecology, morphospecies, sequencing, biotic index, pollution
Retrofit steam turbine 210 MW
Sedláček, Tomáš ; Fiedler, Jan (referee) ; Kracík, Petr (advisor)
This master‘s thesis deals with the retrofit of a three-body condensing steam turbine with an output of 210 MW. The first part deals with the thermal diagram, which is designed with seven unregulated steam extractions and one extraction for degassing. The mass flow is determined here on the basis of the required power and three thermal diagrams are made for different outputs. In the next part, the regulation stage in the A-wheel design was designed, including the strength control. The main subject is the design of the stage part, which is divided into preliminary and a detailed calculation relating only to the high pressure section of the steam turbine. During the optimization phase, a detailed calculation is linked to the thermal diagram and the regulation stage. The resulting blading of the HP section is optimized based on the selected properties, including strength control. An orientation design of the compensating piston together with the sealing system is also included, for selected diameters, due to the unknown action of the axial force from the MP and LP section. Furthermore, a strength check of the inner nodes of the existing body of the high-pressure section is performed, where the need to use the inner body arises. The designed HP section, including the regulation stage, achieves an internal power of 69,5 MW, an internal thermodynamic efficiency of 92 % and a reheat factor of 1,0168.
Steam turbine for steam-gas block
Kober, Ondřej ; Fiedler, Jan (referee) ; Kracík, Petr (advisor)
This master’s thesis deals with the design of two variants of a condensing steam turbine for a steam-gas unit. In the first variant, steam bleeding from the turbine for low-pressure regeneration is considered, in the second variant heat regeneration would be provided by a heat recovery steam generator, which is not the subject of the master’s thesis. Three unregulated steam extractions for the deaerator and two low-pressure heaters are considered for the turbine with steam bleeding. Both turbines were designed with an impulse governing stage and a reaction blading. The result of the design of bleeding variant is a turbine with a speed of 7000 min-1 with 7 cones, 33 stages with power output of 13,69 MW and an efficiency of 81,83%. The turbine without bleeding has a speed of 6500 min-1, 7 cones, 38 degrees, power output of 14,13 MW and an efficiency of 81,97%. The consumption characteristics are given for both turbines at the end. For the steam bleeding turbine, a drawing of the turbine section is attached to the thesis.
Condensing steam turbine
Krška, Jan ; Kracík, Petr (referee) ; Fiedler, Jan (advisor)
This master’s thesis deals with the design of a condensing steam turbine for certain parameters. In the initial part of the thesis, a research on steam turbines and types of blading is carried out. The computational part of the thesis is divided into several subchapters which have been made into larger chapters. One of the chapters deals with the thermodynamic calculation of the flow section of a steam turbine for a clamp power of 5 MW, a speed of 11,000 min-1 and a pressure of 0,1 bar (a). The calculation has been optimized for several basic operating parameters that the steam boiler is capable of achieving with respect to the highest possible thermodynamic efficiency of the plant. The work includes the evaluation of the results in the form of a graph. After the calculations for all steam parameters have been performed, the point was selected which with it’s values meets the requirements for the highest thermodynamic efficiency. The optimum operating parameters of this turbine are such that the turbine at a nominal temperature of 490 °C and an operating pressure of 65 bar (a) achieves a clamp power of 5190,220 kW. The thermodynamic efficiency of the steam turbine is 85,07 % and the reheat factor is 1,0634. Subsequently, basic dimensioning calculations were performed. The calculations are followed by a chapter entitled discussion where some important steps are evaluated. The master’s thesis also contains an appendix. It is a conceptual longitudinal section of a steam turbine.
Condensing steam turbine for a sugar factory
Kovaříček, Jakub ; Fiedler, Jan (referee) ; Kracík, Petr (advisor)
The main topic of the thesis Condensing steam turbine for a sugar factory is a comparison of the methodology for the design of twisted blades of the last low-pressure stages of a condensing steam turbine. The work is divided into the five parts. In addition to the Dunham, Pritchard and Trigg methodologies described in detail, the research in the first part also deals with other, briefly described methods. In the second part, a preliminary calculation of the thermal scheme in which the turbine should be operated is performed. An air condenser is selected behind the turbine. The third part is devoted to the preliminary and detailed calculation of the control degree. The next part deals with the preliminary thermodynamic calculation of the turbine, which has an overpressure blade and is divided into seven flow cones. The content of the following fifth part is a detailed design of the geometry of twisted blades of the last stage. The importance of twisting the blades in terms of efficiency is described here and it is possible to look at the issues of the whole process. The profile of the blades is modeled in detail using two methods and then compared on the mean diameter with the third method, which is modeled only in one section. While the Dunham method is the most time-saving, the generated blade shape is not ideal compared to the more time-consuming methods. The appendix contains a simplified drawing designed for stator and rotor blades.
Steam turbine for biomass heating plant
Cmajdálka, Ondřej ; Fiedler, Jan (referee) ; Kracík, Petr (advisor)
This master thesis deals with the design of a condensing steam turbine for a biomass block burning wood chips with one regulated take for a hot water heat exchanger. The temperature gradient for the hot water is 90/110 ° C. The thesis guides through the designing proces of a steam turbine from the thermal scheme proposed according to the specified parameters, through the design of the regulatory stage and the stage part of the turbine, including strength calculation, to the design of the compensating piston, seals system and bearings. Finally, the operating characteristic of the turbine is constructed.
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.
Energy intensity of artificial snow production
Křepela, Radim ; Fiedler, Jan (referee) ; Pospíšil, Jiří (advisor)
The presented diploma thesis informs about the origin, history, and benefits of technical snowmaking. It introduces what snow equipment consists of and what processes artificial snow is produced. It also shows the price of tons of snow produced from individual commercially available equipment. In the experimental part, the work deals with the calculation of droplet freezing for various input parameters of water, environment, and equipment. A sample calculation was performed for a falling water droplet from a snow lances. The droplet of discharged water was 0.3 mm in size and had a temperature of 2 ° C. The temperature of the environment was chosen to be -10 ° C. Furthermore, the trajectory of the droplet from a snow gun was determined. In the design, a specific snow pole was designed for the specified parameters, including the speed of the environment. The results were then compared with snow poles available on the market.

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