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Spray Cooling at High Temperatures
Chabičovský, Martin ; Čarnogurská, Mária (referee) ; Hajduk, Daniel (referee) ; Raudenský, Miroslav (advisor)
Spray cooling of hot surfaces is used in the metallurgical industry during continuous casting, hot rolling or heat treatment. The water is sprayed on the cooled surface by the nozzle which transforms the water stream to droplets. The spray cooling of hot surfaces can be characterized as forced convection with the presence of the boiling. This physically complicated process is influenced by many factors, such as impurities and contaminants in the water, water temperature, water flow rate, droplet size, droplet impact velocity, surface temperature, surface roughness or the presence of oxides (scales) on the cooled surface. The dominant factor that affects the heat transfer during the spray cooling is the water impingement density. Other factors have a smaller but also significant effect. This doctoral thesis deals with the influence of the water temperature, surface roughness and the presence of oxides on the intensity of the spray cooling. These factors are investigated by laboratory experiments in which the hot steel surface is spray cooled. Effect of the oxide layer is also investigated by the numerical simulation. The experimental results are theoretically explained and generalized using mathematical methods.
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Customer satisfaction analysis
Matějka, Michal ; Plánková, Lucie (referee) ; Chalupský, Vladimír (advisor)
This Master's thesis deals with analyses of customer satisfaction and loyalty to the GiTy, a.s. company. The theoretical part of the thesis explains problems of customer satisfaction and loyalty and their measurement. Furthermore, it deals with marketing research, with a focus on questionnaire-based data acquisition. The practical part of the thesis includes the company presentation, survey design and methodology of the data analysis. This part also describes the continuous customer satisfaction measuring system of the company. The implementation of this measuring system was the aim of this thesis.
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Determination of thermophysical properties of scale layer on steel at high temperatures
Ondruch, Tomáš ; Votavová, Helena (referee) ; Pohanka, Michal (advisor)
The thesis deals with thermophysical properties of scale layer on steel and their determination at high temperatures. The first part summarizes fundamental characteristics of scales, it is also devoted to principles of heat transfer with emphasis on heat conduction. The following text presents current state of research on scales’ thermophysical properties. Subsequently, the thesis aims to experimental measurement of thermophysical properties by use of laser flash method and conducted measurement is described, as well. The following chapters present a finite-element numerical model of the measurement aparatus and computation technique for determination of scales’ thermophysical properties is explained. The obtained results are compared with available data and sensitivity analysis of selected model parameters is carried out.
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Development of New Approaches in Descaling in the Continuous Production of Steel using High-Pressure Water Jet
Votavová, Helena ; Hloch,, Sergej (referee) ; Čecho, Ladislav (referee) ; Pohanka, Michal (advisor)
The thesis summarizes general and up-to-date knowledge of descaling during the continuous production of the hot-rolled steel and proposes further streamlining of this process in industrial production. The first chapter of the thesis deals with the origin, structure and physical properties of the scales. The second chapter describes the principles of descaling by using a high pressure flat water jet. The third chapter introduces the principles of the experimental methods and describes the used laboratory equipment. The fourth chapter summarizes the description of the particular experiments and their evaluation, and thus represents the focus of the dissertation. It is divided into six sections which independently solve predefined objectives of the dissertation. The first section focuses on the height and structure development of the scales on 54SiCr6 and HDT580X steels. It has been proven that the height of the formed scales increases with the time and temperature of the oxidation. The layered nature of the scales was verified at the same time. The second section examines the effect of the nozzle stabilizer on the focussing and distribution of the impact pressure of the nozzle. Experiments have shown that increase of 11 % of an average maximum nozzle pressure can be achieved, depending on the type of nozzle and the length of the stabilizer. The third section deals with the analysis of shadowgraphy images of water jet structures of the nozzles. A script was developed for analysis of these shadowgraphy photos by an adaptive thresholding. The findings are correlated using a regression analysis with an average heat transfer coefficient. It has been reported that most of the standard nozzle configurations produced disintegrated stream of little droplets at the height of the rolled surface. The fourth section focuses on the area of water jet overlap, especially the area of the so-called washout, where the impact pressure of one nozzle is reduced by the nozzle stream of the other. The influence of the pressure change and the mutual displacement of the nozzles is investigated. The analysis showed that the change of pressure did not have any effect on the percentage of reduction of the impact pressure in the area of the washout. It has been shown that if the area of the washout is wide the descaling efficiency in this area may be reduced. The fifth section builds on the previous section and focuses directly on the areas of waterjet overlaps. The influence of the change of rotation and pitch of the nozzles is studied. Experiments have shown that small changes in nozzle pitch do not have a significant impact on impact pressure and heat transfer coefficient. The effect of nozzle rotation, on the other hand, was a significant factor for the efficiency and homogeneity of the descaling of the surface. The last section deals with the effect of the rolling speed on the heat transfer coefficient in the descaling process. The regression model has shown that with a higher rolling speed there is a reduction in the average heat transfer coefficient. Conclusion summarizes the results of the dissertation and proposes which findings can be used in the industry to make the descaling process more effective.
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Design of a supermarket food scale
Švancarová, Jana ; Řezníček, Svatopluk (referee) ; Křenek, Ladislav (advisor)
The subject of this bachelor thesis is to propose new modern design of a food scale, which are used in supermarkets. The final proposal should meet all functional, technological and aesthetic requirements for this type of device. The aim of the thesis is to adapt the overall shape and arrangement of individual components to suit different needs of users, particularly by appropriate ergonomics.
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Forming lines molding hot weighing up to 100 kg
Smyček, Ondřej ; Humlíček, Jaroslav (referee) ; Omes, Jiří (advisor)
This project was made within the engineering studies and its aim was to design an assembly line to product assigned components of appropriate quality and quantity, using the technology of hot extrusion, both backward and forward. A series of technology steps was suggested, parameters necessary for individual operations were set and on this basis, adequate machines were chosen. The conclusion of this work contains technical-economical evaluation for the chosen options which expects the ten-year return with average production of 40 000 pieces.
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Evaluation of the Performance in the Firm
Zycháčková, Lenka ; Michalec, Martin (referee) ; Žižlavský, Ondřej (advisor)
This master‘s thesis deals with the business performace assesment of the company using the Balanced Scorecard method. Based on the acquired theoretical knowledge about this method analyse the financial and non-financial customer perspective, perspective of internal processes, perspective of learning and growth. The strategic goals and scales are designed based on the findings obtained during the analysis, which should help the company to improve its overall performace in the upcoming years.
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The reconstruction design of timber structures of the existing building
Bartlová, Jana ; Šmak, Milan (referee) ; Straka, Bohumil (advisor)
The content of this work was to carry out construction-technical survey of timber structures of the existing building in order to design an appropriate procedure for their reconstruction. The survey showed construction in an unsatisfactory to disrepair, so further work also includes the static calculation of new structures proposed instead of the current. Timber structure in the building has form of staircase, roof and ceiling construction. Newly designed the following types of stairs and roof trusses from which the lower belts are used as ceiling beams. The new proposal also includes possible roofing, roofing options, developed one of them. The work also includes drawings, bill of materials and cost estimate staircase structure and truss. Specialization in the field of civil engineering is represented by drawings of the new truss and passport (view of current state) whole object on parcel ST.74 / 1, land Tišnov (okr.Brno-venkov), the content of which was the basis for this work.
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Influence of the oxide layer on the cooling of steel surfaces
Resl, Ondřej ; Pohanka, Michal (referee) ; Chabičovský, Martin (advisor)
This thesis deals with the influence of the oxide layer on the spray cooling of steel surfaces. As part of the work steel samples with oxide layer are made and the thickness, porosity and surface roughness of this layer are characterized. The average thermal conductivity of porous oxide layer is determined for different regimes of oxidation. Further, the influence of the oxide layer on the heat transfer coefficient during the spray cooling is experimentally investigated on created samples and the basic numerical simulation of the cooling is done for selected experiment with oxide layer. The thesis also contains theoretical introduction to given issue.
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Comparative development of scales and surfaces of fishes
Uherková, Michaela ; Černý, Robert (advisor) ; Vaškaninová, Valéria (referee)
1 Abstract The body surfaces of cartilaginous fishes (Chondrichthyes) and bony fishes (Osteichthyes) are composed of scales, with individual scale types differing in their morphological description, stratification, morphogenetic development and representation in each group. In fossil species, we encounter hard bony shells or plates, which gradually change during evolution to flexible scales of the elasmoid type, these are found in contemporaneous representatives of the bony fish group (Teleostei). Recent scale types found on the surface of present-day fish-like vertebrates include modified cosmoid scales, ganoid scales, placoid scales and elasmoid scales. Odontodes, which include placoid scales, ganoid scales, vertebrate oral teeth and pharyngeal teeth, are a key component in the evolutionary development of all these body surfaces. Odontodes form the basic structural unit of all dermo-skeletal structures and, from an evolutionary point of view, have evolved into the scales and oral teeth of vertebrates. Because of the interesting correlation between teeth and scales, a separate chapter of the literature review will be devoted to theories of the origin of oral teeth. The present bachelor's thesis discusses the evolutionary development of scales of cartilaginous fishes and bony fishes with respect to the...
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