431979 An Adhesive CFDDEM Model for Simulating Nanoparticle Fluidization

Tuesday, November 10, 2015: 4:50 PM
254A (Salt Palace Convention Center)
Daoyin Liu1, Berend G.M. van Wachem2, Robert F. Mudde3, Xiaoping Chen4 and J. Ruud van Ommen3, (1)Delft University of Technology, Delft, Netherlands, (2)Mechanical Engineering, Imperial College London, London SW7 2AZ, England, (3)Chemical Engineering, Delft University of Technology, Delft, Netherlands, (4)Southeast University, Nanjing, China

 


Nanoparticle fluidization is an efficient technique to disperse and process nanoparticles [1]. Previous studies show that it works, because we do not fluidize individual nanoparticles, but nanoparticle agglomerates as hierarchical fractal structures [2]. In this study, an adhesive CFDDEM (Computational Fluid Dynamics Discrete Element Modelling) model is developed, in which we use as the discrete element the simple agglomerate, which roughly represent the smallest clusters that are not broken during fluidization. We show that both the particle contact model and drag force interaction in the conventional CFDDEM model need modification for properly simulating fluidization of nanoparticle agglomerates. The adhesive contact model includes energy dissipation from the elastic/plastic, cohesive and viscoelastic forces, and the drag force is corrected by a scale factor resulting from particle agglomeration. The model is tested for different cases, including the normal impact, response of angle, agglomerate formation, and fluidization. The simulation results are promising. Figure 1 shows examples of solid particle flow patterns in a fluidized bed under different adhesive forces. With increasing particle adhesive force, the fluidized bed goes from a uniform fluid-like regime, to an agglomerate bubbling regime, and finally to defluidization. The current study provides a tool for gaining insights into characteristics of nanoparticle fluidization.

Figure 1. Snapshots of solid particle flow patterns. The ratio of the particle adhesive force over the particle weight is 0, 20, 50, and 100, respectively.

References

[1] van Ommen, J.R., Valverde, J.M. and Pfeffer, R. (2012) J. Nanopart. Res. 14, 737

[2] de Martin, L. and van Ommen, J.R. (2013) J. Nanopart. Res. 15, 2055


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