Numerical Simulation of Bubble Column Flows in Churn-Turbulent Regime: Comparison of Bubble Size Models
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- 作者：Lijia Xu ; Boruo Yuan ; Haoyin Ni ; Caixia Chen
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2013
- 出版时间：May 22, 2013
- 年：2013
- 卷：52
- 期：20
- 页码：6794-6802
- 全文大小：465K
- 年卷期：v.52,no.20(May 22, 2013)
- ISSN：1520-5045
文摘
Numerical simulations of cylindrical bubble column operating in the churn-turbulent regime have been simulated using Euler鈥揈uler approach incorporated with the RNG k鈥撐?model for liquid turbulence. Single-size bubble model, double-size bubble model, and the multiple size group model (MUSIG), including the homogeneous and inhomogeneous discrete methods, are employed in the simulations. Mass conserved formulations of breakup and coalescence rates were used in the computation of bubble size distributions. The Schiller鈥揘aumann drag force was used in the single-size model, and the Ishii鈥揨uber drag force was used for the MUSIG simulations. For the double-size bubble model, an empirical drag formulation was adapted. The simulation results of time-averaged axial velocity and gas holdup obtained with the three models were compared with reported experimental data in the literature. The results showed that only MUSIG models with lift force can reproduce the measured radial distribution of gas holdup in the fully developed flow regime and that the inhomogeneous MUSIG model performs a little better than other models in the prediction of axial liquid velocity. The RNG k鈥撐?model was used in all simulations, and the results confirmed that this version of k鈥撐?model did yield relatively high turbulence dissipation rates and high bubble breakup rates and, thus, resulted in a rational bubble size distribution. The ad hoc manipulation of the breakup rates was avoided. The simulation results indicated profound mutual effects of drag force, mean bubble sizes, and turbulence characteristics. An increase in drag force yielded a decrease in the relative velocity between phases, the later could result in decreases in k and 蔚. A large Sauter diameter results from a low bubble breakup rate which was directly connected to the dissipation rates of turbulence. The change of Sauter diameter, in turn, influenced the drag force.