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Prediction and experimental evaluation of the performance of a Z-type distribution system
Polcsák, Jakub ; Rebej, Miroslav (oponent) ; Babička Fialová, Dominika (vedoucí práce)
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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Užití vizualizační metody pro rekonstrukci výměníkové sítě
Witos, Anton ; Rebej, Miroslav (oponent) ; Jegla, Zdeněk (vedoucí práce)
Metódy pre zobrazovanie sietí výmenníkov tepla sú dôležitým nástrojom pri ich rekonštrukcii. Pomocou týchto metód sa možno lepšie orientovať v sieťach výmenníkov tepla a taktiež s ich pomocou možno ľahko určiť oblasť siete, ktorá bude vhodná pre rekonštrukciu. Jednou z takýchto zobrazovacích metód je Shifted Retrofit Thermodynamic Grid Diagram. Cieľom tejto diplomovej práce je na základe odporúčanej literatúry a v kombinácii s výpočtovým postupom aplikovať túto metódu na priemyslové príklady a preskúmať tak možnosti jej použitia v praxi. Súčasťou riešenia priemyselných príkladov je taktiež porovnanie tejto zobrazovacej metódy s niektorou z konkurenčných metód zobrazovania sietí výmenníkov tepla, ako je napríklad metóda Grid Diagram. Cieľom porovnania metódy Shifted Retrofit Thermodynamic Grid Diagram s niektorou z konkurenčných metód je preskúmanie výhod a nevýhod tejto metódy.
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Simplified flow distribution modelling
Rebej, Miroslav ; Vondál, Jiří (oponent) ; Turek, Vojtěch (vedoucí práce)
The focus of this master’s thesis is modelling of fluid flow in parallel distribution systems where the uniformity of fluid distribution plays an important role. For this purpose, a custom CFD code is presented. The code is written in Java programming language and uses third-party low-level libraries for improved performance. The code is also characterised by certain simplifications that are expected to reduce computational times. The effect of employed simplification measures is evaluated by comparing the results of flow simulations on several geometries with the data yielded by detailed CFD models. The geometries of tube bundles are distinguished by different flow and tube arrangements and also by a different number of tubes.
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Snižování CO2 pomocí řas
Naider, Jakub ; Rebej, Miroslav (oponent) ; Vondál, Jiří (vedoucí práce)
Práce je zaměřena na proces kultivace řas a jejich využití pro snižování emisí oxidu uhličitého. Hlavním cílem práce je hmotnostní a tepelná bilance fotobioreaktoru a návrh řešení regulace teploty. V rámci práce byla vypracována rešerše, která se zabývá jednotlivými typy bioreaktorů a fotobioreaktorů, aktuální situací kolem klimatu a vlivu kultivace mikrořas na emise oxidu uhličitého. V práci je popsán model pro regulaci teploty a přenosu hmoty deskového fotobioreaktoru.
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CFD analysis of thermal stress of a tubesheet
Vince, Tomáš ; Babička Fialová, Dominika (oponent) ; Rebej, Miroslav (vedoucí práce)
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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Optimalizace vnitřní geometrie deskového fotobioreaktoru
Hlaváč, Ivan ; Babička Fialová, Dominika (oponent) ; Rebej, Miroslav (vedoucí práce)
Tato diplomová práce se zaměřuje na optimalizaci deskového fotobioreaktoru. Optimalizace byla provedena s využitím CFD výpočtů a plánovaného experimentu. CFD model použitý k optimalizaci byl před provedením experimentu validován s reálnými experimentálními daty. Během CFD výpočtů byly sledovány hydrodynamické parametry ovlivňující výtěžnost mikrořas. Konkrétně se jednalo o parametry: zvednutí plynu, rychlost plynu, turbulentní kinetická energie, poměr mrtvých zón, koeficient přestupu hmoty, mezifázové rozhraní a smykové napětí. Porovnán byl fotobioreaktor s míchadlem a s kolmými přepážkami. Při použití míchadla hydrodynamické parametry dosahovaly vyšších hodnot. Přepážky byly vyhodnoceny jako vhodnější pro mikrořasy citlivější na smykové napětí.
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Simulations of Photobioreactors from Hydrodynamics and Mass Transfer Point of View
Rebej, Miroslav ; Turek, Vojtěch (oponent) ; Jördening, Alexandra (oponent) ; Jegla, Zdeněk (vedoucí práce)
Simulations of photobioreactors with microalgae-specific cultures is a field that connects microbiology with the multiphase fluid dynamics. With microalgae cultivation, it is necessary to account various phenomena, e.g., multiphase hydrodynamics with water, CO2 bubbles and microalgae, multiphase species mass transfer, radiation transport, light attenuation, growth and culmination of microalgae and their effect on fluid properties. Computational model presented in this doctoral dissertation thesis links multiphase hydrodynamic model and the species mass transfer model. In the thesis, there is an overview of applicable computational models for the given types of photobioreactors. The multiphase hydrodynamic model and the species mass transfer model then draw from this overview. Next, the accuracy of these sub-models was compared with laboratory experiments. As a result, the developed computational model of the photobioreactor can be further extended with other sub-models, i.e., the irradiation model and the biomass growth model.
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Užití vizualizační metody pro rekonstrukci výměníkové sítě
Witos, Anton ; Rebej, Miroslav (oponent) ; Jegla, Zdeněk (vedoucí práce)
Metódy pre zobrazovanie sietí výmenníkov tepla sú dôležitým nástrojom pri ich rekonštrukcii. Pomocou týchto metód sa možno lepšie orientovať v sieťach výmenníkov tepla a taktiež s ich pomocou možno ľahko určiť oblasť siete, ktorá bude vhodná pre rekonštrukciu. Jednou z takýchto zobrazovacích metód je Shifted Retrofit Thermodynamic Grid Diagram. Cieľom tejto diplomovej práce je na základe odporúčanej literatúry a v kombinácii s výpočtovým postupom aplikovať túto metódu na priemyslové príklady a preskúmať tak možnosti jej použitia v praxi. Súčasťou riešenia priemyselných príkladov je taktiež porovnanie tejto zobrazovacej metódy s niektorou z konkurenčných metód zobrazovania sietí výmenníkov tepla, ako je napríklad metóda Grid Diagram. Cieľom porovnania metódy Shifted Retrofit Thermodynamic Grid Diagram s niektorou z konkurenčných metód je preskúmanie výhod a nevýhod tejto metódy.
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CFD analysis of thermal stress of a tubesheet
Vince, Tomáš ; Babička Fialová, Dominika (oponent) ; Rebej, Miroslav (vedoucí práce)
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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