Numerical and experimental investigation towards a mechanistic approach for prediction of two-phase gas-liquid flow with and without heat and mass transfer

Vahaji, S 2016, Numerical and experimental investigation towards a mechanistic approach for prediction of two-phase gas-liquid flow with and without heat and mass transfer, Doctor of Philosophy (PhD), Aerospace, Mechanical and Manufacturing Engineering, RMIT University.


Document type: Thesis
Collection: Theses

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Title Numerical and experimental investigation towards a mechanistic approach for prediction of two-phase gas-liquid flow with and without heat and mass transfer
Author(s) Vahaji, S
Year 2016
Abstract Two-phase gas-liquid flows are prevalent in various industrial applications. In this study, flows both with and without heat and mass transfer are being considered. For the former, the application of subcooled boiling flow in vertical channels in low and elevated pressures are investigated numerically. Also, the application of power generation through the expansion of single phase water to two-phase gas-liquid inside the nozzle is investigated experimentally. For the latter, the application of bubbly flow around an underwater vehicle is numerically studied.
Modelling subcooled flow boiling in vertical channels requires not only the consideration of the dynamic behaviours of two-phase flow and bubbles undergoing coalescence, breakup and condensation in the bulk subcooled liquid but also the characterisation of the single-phase and local boiling heat transfer phenomena in the near-wall region. In numerical modellings of heat partitioning in the subcooled boiling flow, mostly empirical correlations have been adopted in the literature. A thorough investigation on these correlations reveals that they are mainly bound to very limited range of flow conditions in which the experiments had been carried out. Therefore, in this study, first principal models of the underlying physical phenomena are being considered to enlighten the path for having a potential generic modelling algorithm for prediction of wider range of flow conditions. The influence of pressure on the proposed method for predicting subcooled boiling flows in elevated pressures has also been investigated.
Also, the evolution of the bubble size distribution caused by the coalescence and break-up processes in the bulk subcooled liquid is of main interest to numerically investigate its impact on local hydrodynamics. Subsequently, in this study, the performance of six kernels on bubble size distribution is compared to achieve a better insight of the prediction mechanisms.
Then, the possibility of utilizing low temperature energy sources as a means of power generation in conversion of single phase flow to two phase flow through nozzles is investigated experimentally. The experimental data provide essential information towards understanding the complex flashing process in the nozzle. The results complement the available data on two phase nozzles for medium to high temperature applications.
Finally, an Eulerian-Eulerian two-fluid model coupled with the MUSIG population balance model is adopted to predict the bubble size distribution around a DARPA SUBOFF submarine to investigate the capability of the model in this emerging application.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Aerospace, Mechanical and Manufacturing Engineering
Subjects Computational Fluid Dynamics
Keyword(s) Computational Fluid Dynamics
Heat and Mass Transfer
Multiphase Flow
Population Balance Modeling
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Created: Thu, 02 Mar 2017, 12:28:05 EST by Denise Paciocco
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