Physical Insight into the Meso-Structures and Multiscale Modeling of Multiphase Reactors

Physical insight into the meso-structures and multiscale modeling of multiphase reactors

Ning Yang and Jinghai Li

State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, P.O.Box 353, Beijing, 100190, P.R.China

Email: nyang@home.ipe.ac.cn

            Meso-structure receives much attention in the multiscale modeling of multiphase reactors in recent decades. It is ubiquitous yet elusive, and critical to momentum, mass and heat transfer yet hard to describe and quantify. Physical understanding of meso-structures is still challenging for many multiphase systems. This talk presents the Energy-Minimization Multi-Scale (EMMS) approach in understanding and modeling the meso-structures in gas-solid fluidization and gas-liquid bubbly flow systems. The averaged mass and momentum conservative equations are inadequate to acquire a complete description of the multi-scale structures. The so-called stability condition might be indispensable for each specific complex system. It is formulated as the minimization of micro-scale energy dissipation and meanwhile the maximization of meso-scale energy dissipation, and supplies another constraint to averaged mass and momentum conservative equations. The approach itself can predict and interpret the regime transition of gas-solid and gas-liquid systems, that is, the macro-scale structure evolution. When integrated into the framework of two-fluid CFD models in some seamless or simplified ways, it can offer some constitutive laws like the averaged drag coefficient to dramatically improve the coarse grid simulation of multi-phase systems.

 

References 1.                  Li, J. et al. (2013) From Multiscale Modeling to Meso-Science, Springer.

2.                  Yang, N., Wang, W., Ge, W., Li, J., (2003), "CFD simulation of concurrent-up gas-solid flow in circulating fluidized beds with structure-dependent drag coefficient," Chemical Engineering Journal, 71-80.

3.                  Yang, N., Wang, W., Ge, W., Li, J., (2004), "Simulation of heterogeneous structure in a circulating fluidized-bed riser by combining the two-fluid model with the EMMS approach," Industrial and Engineering Chemistry Research, July, pp. 5548-5561. 4.                  Chen, J., Yang, N., Ge, W., Li, J., (2009), "Modeling of regime transition in bubble columns with stability condition," Industrial and Engineering Chemistry Research, 48, pp. 290-30l. 5.                  Yang, N., Wu, Z., Chen, J., Wang, Y., Li, J., (2011), "Multi-scale analysis of gas¨Cliquid interaction and CFD simulation of gas¨Cliquid flow in bubble columns," Chemical Engineering Science, July, pp. 3212-3222. 6.                  Yang, N., Chen, J., Ge, W., Li, J., (2010), "A conceptual model for analyzing the stability condition and regime transition in bubble columns," Chemical Engineering Science, 517-526. 7.                  Yang, N., Chen, J., Zhao, H., Ge, W., Li, J., (2007), "Explorations on the multi-scale flow structure and stability condition in bubble columns," Chemical Engineering Science, December, pp. 6978-6991. 8.                  Xiao, Q., Yang, N., Li, J., (2013), "Stability-constrained multi-fluid CFD models for gas-liquid flow in bubble columns," Chemical Engineering Science, 279-292 9.                  Yang, N., (2012), "A multi-scale framework for CFD modelling of multi-phase complex systems based on the EMMS approach, " Progress in Computational Fluid Dynamics, June, pp. 220-229.