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Design of modular tubular heat exchanger
Marx, Sven ; Turek, Vojtěch (referee) ; Jegla, Zdeněk (advisor)
Hlavním cílem této práce je seznámit se s požadavky specifické procesní aplikace a návrhem výměníku tepla s křížovým tokem pracovních látek a zhodnotit návrh předmětného výměníku pomocí simulačního softwaru. Nejprve jsou v práci prozkoumány provozní podmínky rekuperace odpadního tepla a obecné možnosti návrhu a jsou uvedeny základní rovnice pro tepelný a hydraulický výpočet. Hlavní část práce se zaměřuje na modulární trubkový výměník tepla s křížovým tokem pracovních látek navržený pro experimentální výzkum rekuperace tepla a zanášení ze znečištěných spalin produkovaných spalováním alternativních paliv na VUT v Brně (VUT) na Ústavu procesního inženýrství (UPI). Nejprve je stručně představena situace v testovací laboratoři. Poté je popsán postup návrhu předmětného tepelného výměníku pomocí softwaru HTRI a výsledky jsou shrnuty a porovnány s cílovými požadavky. Následně je analyzována distribuce toku vody v trubkovém prostoru uvnitř jednoho ze čtyř identických modulů výměníku tepla užitím softwaru CDF pomocí tří různých simulačních přístupů. Jsou popsány dva přístupy využívající model turbulence k--SST a jeden přístup využívající model turbulence k--Realizable turbulence. Nakonec jsou diskutovány rozdíly mezi přístupy a výsledky simulací distribuce toku.
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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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Analysis of Flow Distribution in Systems with Dense Tube Bundles
Babička Fialová, Dominika ; Dohnal, Miloslav (referee) ; Turek, Vojtěch (advisor)
Considering heat transfer equipment with dense tube bundles, it is essential to ensure as uniform a fluid distribution into the tubes as possible in order to prevent various operating problems. This bachelor’s thesis therefore focuses on tube-side flow analysis in such equipment. CFD simulations were carried out using a diverse set of flow systems with outflow into a constant-pressure environment. The respective tube bundle geometries differed in densities and sizes, arrangements of the tubes, and tube diameters. Air was used as the working fluid in the majority of the cases, however, some of the simulations were also carried out with water. Data obtained from evaluations in the fluid flow modelling software ANSYS Fluent were further analysed and the influence of the mentioned differentiating parameters on flow distribution non-uniformity and pressure drop was investigated. According to the regression model, the dependence of flow distribution non-uniformity on density and size of the bundle and on mass flow rate per unit outflow area cannot be rejected with the standard significance level. As for pressure drop, the only parameter that was not rejected was mass flow rate per unit outflow area.
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New Elements of Heat Transfer Efficiency Improvement in Systems and Units
Turek, Vojtěch ; Klemeš,, Jiří (referee) ; Odstrčil, Miloslav (referee) ; Jegla, Zdeněk (advisor)
Zvýšení efektivity výměny tepla vede k poklesu spotřeby energie, což se následně projeví sníženými provozními náklady, poklesem produkce emisí a potažmo také snížením dopadu na životní prostředí. Běžné způsoby zefektivňování přenosu tepla jako např. přidání žeber či vestaveb do trubek ovšem nemusí být vždy vhodné nebo proveditelné -- zvláště při rekuperaci tepla z proudů s vysokou zanášivostí. Jelikož intenzita přestupu tepla závisí i na charakteru proudění, distribuci toku a zanášení, které lze všechny výrazně ovlivnit tvarem jednotlivých součástí distribučního systému, bylo sestaveno několik zjednodušených modelů pro rychlou a dostatečně přesnou predikci distribuce a také aplikace pro tvarovou optimalizaci distribučních systémů využívající právě tyto modely. Přesnost jednoho z modelů byla dále zvýšena pomocí dat získaných analýzou 282 distribučních systémů v softwaru ANSYS FLUENT. Vytvořené aplikace pak lze využít během návrhu zařízení na výměnu tepla ke zvýšení jejich výkonu a spolehlivosti.
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Fluid Flow in Nonstandard Process and Power Equipment
Chýlek, Martin ; Babička Fialová, Dominika (referee) ; Turek, Vojtěch (advisor)
Flow distribution has big importance in equipment with limited tube rows because it provides correct operation and sometimes specific flow distribution for technology purposes is needed. This thesis is focusing on flow analysis in these units using computational fluid dynamics (CFD). For analysis of such systems models with varying tube rows and varying perforated segment lengths were created. Analysis showed significant impact of flow manifold layout along with tube layout and number of tubes. Simplified 1D model using static pressure regain coefficient was created which provides much shorter computational times. Comparison of 1D and CFD models was made to determine field of their usage.
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Design of an experimental manifold suitable for a 3D print manufacturing
Zeman, Stanislav ; Křivohlavý, Petr (referee) ; Vaverka, Ondřej (advisor)
The target of this thesis was to design a method of mounting pressure sensors on an already designed shape of a flow distribution header. Furthermore, it was necessary to design a method of mounting the header on a laboratory stand and then find a method of surface treatment. This thesis was solved in these three structural nodes. Gradually, three variants were designed for the threaded connection of the distributor and the pressure sensor and then three variants of installation were designed for the selected threaded connection. The possibilities of mounting a header on a laboratory stand were designed in two variants. Finally, possible methods of surface treatment have been proposed to improve the impermeability through the wall of the header. The individual variants in each design node were compared with each other by their strength and the result was the final design of the flow distribution header. It was manufactured according to the given technological procedure and then its functionality was tested.
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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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Flow Distribution in Equipment with Dense Tube Bundles
Babička Fialová, Dominika ; Jegla, Zdeněk (referee) ; Turek, Vojtěch (advisor)
Significant maldistribution negatively influences performance of equipment containing dense tube bundles and, moreover, it can cause a wide range of operating issues. This thesis therefore focuses on analysis of fluid flow in complete distribution systems via computational fluid dynamics (CFD). Data obtained from simulations carried out using the software ANSYS Fluent were also statistically analysed. Influence of system arrangement, tube bundle parameters and operating parameters on flow distribution non-uniformity and pressure drop was investigated. According to the results, system arrangement is the crucial differentiating parameter in terms of flow distribution as well as pressure drop. Additionally, data obtained via the classical CFD approach were compared with those yielded by a simplified CFD model for three selected distribution systems. Simplified CFD approach can - given its low computational demand - be utilised in optimization algorithms as well as in the course of the initial stage of equipment design process. Furthermore, this thesis discusses a simulation tool which is based on the simplified CFD approach. Although this tool is still being developed, the results it yields are very promising.
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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 an experimental manifold suitable for a 3D print manufacturing
Zeman, Stanislav ; Křivohlavý, Petr (referee) ; Vaverka, Ondřej (advisor)
The target of this thesis was to design a method of mounting pressure sensors on an already designed shape of a flow distribution header. Furthermore, it was necessary to design a method of mounting the header on a laboratory stand and then find a method of surface treatment. This thesis was solved in these three structural nodes. Gradually, three variants were designed for the threaded connection of the distributor and the pressure sensor and then three variants of installation were designed for the selected threaded connection. The possibilities of mounting a header on a laboratory stand were designed in two variants. Finally, possible methods of surface treatment have been proposed to improve the impermeability through the wall of the header. The individual variants in each design node were compared with each other by their strength and the result was the final design of the flow distribution header. It was manufactured according to the given technological procedure and then its functionality was tested.
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