ABSTRACT
Impinging stream contactors provide a novel efficient configuration for drying and/or chemical reactions involving particulates, pastes or suspensions which can be dispersed in a flowing stream. Essentially they consist of one or more highly turbulent " impingement " zones formed by collision of two opposing jets in a confied channel or duct. The objective of this study is to present computational fluid dynamic predictions for drying of particles entrained in two-dimensional "opposing jet" contactors using superheated steam as the drying medium. A single phase flow study was performed first in which a number of different turbulence models were tested ( e.g. high Reynolds, LamBremhorst, Launder and Sharma models etc.). Then the numerical simulation for drying of a single particle in superheated steam is presented. Finally a two phase simulation model presented to investigate the steam drying characteristics of a two dimensional opposing jet contactor. The effect of particles on the flow is considered via additional 538momentum, energy and mass source terms in the momentum equations. To simulate particle dispersion by turbulent motions in the carrier fluid a random-walk model was deployed. Wall-particle collisions were modeled stochastically assuming a Gaussian distribution of the wall roughness angle. A power law, finite volume method based on the "SIMPLEC" algorithm was used to solve the governing equations and the RungeKutta fourth-order scheme was employed to solve the particle motion, energy and mass transfer equations. The two-phase turbulent flow model was found to give satisfactory agreement with published results for flow in a two dimensional channel.
