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CFD analysis of thermal stress of a tubesheet
Vince, Tomáš ; Babička Fialová, Dominika (referee) ; Rebej, Miroslav (advisor)
This diploma thesis focuses on the phenomena of multiphase flow in a steam generator as a one of probable causes of tubes and tubesheet weld cracking. In the first part of the work, a research was carried out focusing on the boiling and the phenomenon of two-phase flow in technical applications, its characteristics and properties. The thesis continuous with an overview of available numerical multiphase models in the ANSYS Fluent 2021 R1 and a research of previously published works focused on two-phase flow with the presence of boiling. The research is followed by a description of the particular boiler, which is part of the nitric acid production plant in the chemical company DUSLO, a.s., its operating conditions and a more detailed description of the issue that is being addressed in this thesis. The second part of the work continuous with a description of the computational model, including a description of the geometry of the model and used simplifications, the computational mesh and the description of boundary conditions. Important part is the description of calculation setting of steady-state and transient CFD simulations in ANSYS Fluent. Finally, the results of the two-phase flow calculation are presented and then discussed in the conclusions.
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Prediction and experimental evaluation of the performance of a Z-type distribution system
Polcsák, Jakub ; Rebej, Miroslav (referee) ; Babička Fialová, Dominika (advisor)
The purpose of this work was to find a suitable calculation method for predicting the function of distribution systems in the design calculations of process and energy equipment. In particular, it aimed at describing the distribution of the working fluid flow in a dividing distribution system and a combined Z-type distribution system (with nozzles located parallel to opposite sides of the system). Analytical and CFD calculation tools validated by data from the performed physical experiments were used in this work. In the CFD method, the prediction of the dividing flow was performed for full 3D and simplified 2D geometry of Z-type distribution systems. The carried-out analyzes show that the prediction of the distribution system function obtained by both analytical and numerical approaches is accurate enough. The relative difference between the experimental and computational relative standard deviations did not exceed 9 %. The main disadvantage of 3D CFD analysis, especially concerning the purpose of the intended application, i.e., the inclusion of a distribution model in a complex modeling system for the initial design of heat transfer equipment, was the extremely long computational time. Analytical models appear to be a reasonable compromise between the accuracy of the flow distribution prediction and the computational times.
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CO2 reduction with algae
Naider, Jakub ; Rebej, Miroslav (referee) ; Vondál, Jiří (advisor)
The aim of this final thesis is the process of algae cultivation their use for carbon dioxid reduction. The main objective of this work is the mass and heat balance of the photobioreactor and the design of a temperature control system. Within the research work, an overview of certain types of bioreactors and photobioreactors, the current situation around the climate and the impact of the cultivation of algae on carbon dioxide emissions. The model for temperature control and mass transfer of a plate photobioreactor is created in this work.
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Simplified flow distribution modelling
Rebej, Miroslav ; Vondál, Jiří (referee) ; Turek, Vojtěch (advisor)
Tato diplomová práce se zaměřuje na modelování proudění tekutiny v paralelních distribučních systémech, kde hraje důležitou roli rovnoměrnost distribuce tekutin. Pro tento účel je vytvořen vlastní CFD kód. Kód je napsán v programovacím jazyce Java a používá ke zlepšení výkonu knihovny třetích stran, které se vyznačují přímým přístupem ke hardwarovým a systémovým prostředkům. Kód se také vyznačuje určitými zjednodušeními, u nichž se očekává, že sníží výpočetní časy. Vliv použitých zjednodušujících opatření je vyhodnocen porovnáním výsledků simulací proudění na několika geometriích s údaji získanými z podrobných modelů CFD. Geometrie použitých svazků trubek se odlišují různými uspořádáními toku a trubek a také různým počtem trubek.
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