A New Blended Acceleration Model for the Particle Contact Forces Induced by an Interstitial Fluid in Dense Particle/Fluid Flows

Authors: M. K. PATEL ^a, K. PERICLEOUS ^a, and M. CROSS ^a
a Centre for Numerical Modeling and Process Analysis, The University of Greenwich , London, SE18 6PF

Source: This paper was published in 2007, Volume 1, Issue 2 in the International Journal of Computational Fluid Dynamics.

Abstract: The development of the multi-phase flow algorithm MIPSA (Multi-InterPhase Slip-Algorithm) within a two-dimensional Computational Fluid Dynamics (CFD) code called CASCADE is summarized with its application to the modeling of lean phase circulating fluidized beds. The well-known interPhase Slip Algorithm (IPSA) technique for handling the presence of particles in an air stream is modified and extended, to handle explicitly a range of particle sizes simultaneously. The salient features of IPSA are retained; hence each size family is treated as a separate “phase” and its motion governed by its own momentum equations. The MIPSA algorithm is embedded within CASCADE, in a framework which ensures overall conservation of mass, momentum and energy. In this paper, the MIPSA algorithm is used to model the hydrodynamic behavior of Circulating Fluidized Beds (CFB). CFB’s are increasingly being employed by a wide range of process industries and their design for a specific application can be problematic. The objective of this paper is to show how CFB’s can be analyzed to identify their mixing behavior and factors affecting their efficiency of operation. The present study considers hydrodynamic behavior in relation to single and multiple mixing cells in a columnar arrangement, with a range of recirculation rates together with the effect of different riser configurations. The results of the calculations are presented in the form of velocity vectors, pressure contours, temperature contours and solid particle distributions for mono-and multi-sized particle simulations. The relative efficiency of single and multiple units is compared, together with the effects of re-entry.