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Title
CPFD simulation in Barracuda VR of a novel dual fluidized bed cold flow model / von Andreas Lunzer
AuthorLunzer, Andreas
CensorHofbauer, Hermann ; Kraft, Stephan
PublishedWien, 2018
Description141 Blätter : Illustrationen, Diagramme
Institutional NoteTechnische Universität Wien, Diplomarbeit, 2018
LanguageEnglish
Document typeThesis (Diplom)
Keywords (EN)Fluidized Bed / Cold Flow Model / Simulation / Barracuda
URNurn:nbn:at:at-ubtuw:1-115953 Persistent Identifier (URN)
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 The work is publicly available
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CPFD simulation in Barracuda VR of a novel dual fluidized bed cold flow model [23.52 mb]
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Abstract (English)

The target of this master's thesis is to simulate a cold flow model of a novel biomass gasification plant. The fluid dynamical behavior depends heavily on the fluid's and particle's properties and in real reactors a particle size distribution (PSD) is present. An Eulerian-Eulerian approach is only capable to simulate large applications at the expense of high computational costs if the actual PSD is considered. An Eulerian-Lagrangian approach is capable of simulating a PSD and in particular the multi-phase particle in cell (MP-PIC) method is designed for simulations with a high number of particles. Therefore, Barracuda VR, a software-tool with an implemented MP-PIC method specifically designed for CPFD (computational particle fluid dynamics) simulations, was the software of choice. The discussed cold flow model in this thesis is located at TU Wien and several experiments have already been conducted. Those experiments were used to verify the simulation results. The solid used is composed of bronze particles with a Sauter diameter of 81.7m and a given PSD. The simulations and adjustments were rated on the one hand qualitatively by visual observation of the particle volume fraction and distribution of the particles in the reactor and on the other hand quantified by comparing the measured and simulated data of the particle circulation rate and the pressure at designated locations. The simulations were conducted using different drag laws since they have a great influence on the simulation results. An energy-minimization multi-scale (EMMS) approach, a blended Wen-Yu and Ergun (WYE) drag law, and a drag law of Ganser were used. Furthermore, a focus was set onto the normal particle stress, which plays a significant role in close-packed regions. The constant PS to calculate the particle stress was modified, leading to a higher normal stress near close-pack and subsequently reducing the particle volume fraction. Another aspect was raising the fluidization rate in the loop seals to increase the particle circulation rate, since it was underestimated depending on the settings (e.g. PS constant). By optimizing the settings, the simulation became stable and flooding behavior, experienced at the start, did not occur anymore. The Ganser drag law was found to be the best suited drag law for the simulation. The WYE drag law overpredicted the mass flow leading to an unstable system and the EMMS's predicted particle flow rate was unrealistically small while calculating partly good fits for the pressure profile in the fuel reactor's column. The Ganser drag law combined with an adjusted PS value with (PS = 30Pa) or without (PS=50Pa) increased loop seal fluidization rates was providing the best performance.

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