An assessment of mechanistic breakage and coalescence kernels in poly-dispersed multiphase flow

Gas-liquid bubbly flows (i.e. swarm of discrete gas bubbles suspended in continuous liquid) have a wide range of applications; including mining, pharmaceutical and petroleum industries. Many researches have been carried out to develop an effective design tool for these industries and enhance the efficiency of their systems. Population balance (PB) approach in conjunction with Computational Fluid Dynamics (CFD) technique has been widely recognized as a robust methodology in solving such complex bubbly flows and providing a better understanding of the local flow behaviour. Nonetheless, to model the microscopic bubble interactions, an accurate coalescence and breakup kernel is crucial. Several models have been proposed within literatures for modelling breakup frequency and the daughter size distribution in the breakup mechanism; as well as coalescence frequency and efficiency in coalescence (Liao and Lucas 2009; Liao and Lucas 2010). A thorough assessment of the performance of a number of gas-liquid coalescence and breakage kernels has been carried out to find its effect in modelling the evolution of bubble size distribution in large scale vertical bubble column. A total of four different models were considered (one for breakage and three for coalescence) (Coulaloglou and Tavlarides 1977; Prince and Blanch 1990; Luo and Svendsen 1996; Lehr et al. 2002). To assess the performances under complex flow conditions, validation has been carried out against experimental data of Prasser et al. (2007) measured in the Helmholtz-Zentrum Dresden-Rossendorf (HZRD) facility.