Large-Scale Three-Dimensional Simulation of Fluidized Beds

In this project we perform large-scale 3-dimensional simulations of fluidized beds and spouted beds. The following simulation approach is adopted: For gas motion, the local averaged Navier-Stokes equations are integrated by the SIMPLE method employing the staggered grid system. For particle motion, the Newtonian equations of motion of individual particles are integrated. The collisions between particles and between a particle and a wall are simulated by Hooke’s linear springs and dashpots. The proposed simulations require large memory spaces (over 1500 MB for each simulation) and CPU time (up to 10 weeks for 1-sec real-time simulation). The results obtained in this study enable better understanding of fluid dynamics and heat transfer in fluidized beds.

Principal Investigator

Martin Rhodes
Chemical Engineering
Monash University

Project

e44

Co-Investigators

Manaswita Bose
Shan Wang
Jai Kant Pandit
Shintaro Takeuchi
Chrestella Wardjiman
Chemical Engineering
Monash University

RFCD Codes

290600

Significant Achievements, Anticipated Outcomes and Future Work

Our major achievements in 2005 are highlighted below:
1. Detailed study of particle motion near the walls of a gas fluidized bed (published in Powder Technology, vol. 160, 2005, 15-19).
2. Study of the effect of gas-phase pulsation on fluidization characteristics (published in Powder Technology, vol. 159, 2005, 142-149).
3. Application of gas-phase pulsation to overcome defluidization (published in Chemical Engineering Science, vol. 60, 2005, 5177-5181).
4. Further study of Group A fluidization behaviour (published in Powder Technology, vol. 160, 2005, 7-14).
5. Detailed study of particle motion in spouted beds (published in Chemical Engineering Science, vol. 60, 2005, 1267-1276).
6. Study of gas-particle interaction by direct numerical simulation (presented at the 8th International Conference on CFB, Hangzhou, China).

In 2006, we will continue to simulate fluidized beds and spouted beds by using the APAC facilities. Our simulation experiments will be focused on the following areas: (1) Further study, by discrete element method simulation, of the role of interparticle force on fluidization characteristics; (2) Study of bubble formation in gas fluidized beds; (3) Application of DEM simulation for studying other gas-particle systems, such as curtain heat exchangers. In addition, we will look at extending our study to some new topics, such as optimisation of fish shape and swim mode.

 

Computational Techniques Used

(1) Gas fluidization
The SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) scheme of Patanker ("Numerical Heat Transfer and Fluid Flow", New York: Hemisphere, 1980) is used for solving the continuity and momentum equations for the fluid phase. To prevent numerical instability, the convection term is discretized by first order upwind method. Iterative calculations are performed to obtain convergency of velocity and pressure.
(2) Spouted beds
A novel technique on gas-particle coupling in the cylindrical coordinate system is developed. The coupling equation incorporates the effect of void fraction on the continuity of the fluid phase.
(3) Direct numerical simulation of gas-particle interaction
A new surface digitiser is used to identify the interface between the fluid and solid phases. The computation efficiency is significantly improved by using this new digitiser.
(4) Optimisation of fish shape and swim mode
The optimisation is achieved through a generic algorithm utilizing the MPI library. Efficiency of the generic algorithm is enhanced by coupling a least square prediction (LSP) method for fitness values.

 

Publications, Awards and External Funding

External Funding and Awards

Our DEM study of large-scale fluidized beds is supported by ARC Discovery grant - Fluidized bed nanoparticle reactors (2004 to 2006).

Publications

S. Takeuchi, X.S. Wang, M.J. Rhodes, Discrete element study of particle circulation in a 3-D spouted bed. CHEMICAL ENGINEERING SCIENCE, 60, 2005,1267-1276.
X. S. Wang, M. J. Rhodes, A DEM study of particle motion near the walls of gas fluidized beds. POWDER TECHNOLOGY vol. 160, iss. 1, 15 – 19 (2005).
J. K. Pandit, X. S. Wang, M. J. Rhodes, Study of Geldart’s Group A behaviour using the discrete element method simulation. POWDER TECHNOLOGY vol. 160, iss. 1, 7 – 14 (2005).
X. S. Wang, M. J. Rhodes, Using pulsed flow to overcome defluidization. CHEMICAL ENGINEERING SCIENCE vol. 60, 5177 – 5181 (2005).
X. S. Wang, M. J. Rhodes, Pulsed fluidization – a DEM study of a fascinating phenomenon. POWDER TECHNOLOGY vol. 159, 142 – 149 (2005).
X. S. Wang, M. J. Rhodes, Investigation of flow modulation in gas fluidized beds. Proc. of 7th World Congress of Chemical Engineering, Glasgow (2005).
S. Takeuchi, T. Kajishima, X.S. Wang, M.J. Rhodes, Gas-particle interaction in dilute suspensions. Proc. 8th international conference on Circulating Fluidized Beds, May 10 - 13, Hangzhou, China, Paper No. DCS-11 (2005).