Doctor of Philosophy (PhD)
The application of the Euler-Euler framework based Computational Fluid Dynamics (CFD) models for simulating the two-phase gas-liquid bubbly flow in down-flow bubble columns is discussed in detail. Emphasis is given towards the modelling and design optimization of a novel down-flow bubble column. The design features of this novel down-flow bubble column and its advantages over a conventional Plunging Jet down-flow bubble column are discussed briefly. Then, some of the present challenges in simulating a conventional Plunging Jet down-flow bubble column in the Euler-Euler framework is highlighted, and a sigmoid function based drag modification function is implemented to overcome those challenges. The validated CFD results are further utilized for performing a linear stability analysis.
We then discuss the applicability of a coupled CFD-PBM (Population Balance Model) to simulate the micro-bubble generation process in the novel down-flow bubble column of small cross-section of 10 cm diameter. For a much larger column of 30 cm diameter, due to high computational requirements and lack of accurate breakage kernels in the PBM, we model the micro-bubble generation process using the Euler-Euler model with appropriate source and sink terms to represent the region where micro-bubbles are generated. Further, a force-balance based method is used to determine the appropriate drag correlation and the associated local gas hold-up based drag modification functions. The developed CFD modelling approach, is then used to perform design explorations and optimization to improve the performance of the novel down-flow bubble column design. Finally, a one dimensional performance model is derived for the down-flow bubble column. This simple model could be used for scale-up analysis, to provide rough estimates of the performance of a down-flow column of arbitrary length.
Lalitha Chockalingam, Mutharasu, "Multiphase Flow Modeling for Design and Optimization of a Novel Down-flow Bubble Column" (2017). LSU Doctoral Dissertations. 4181.