Gas dispersion through porous nozzles into down-flowing liquids

In this study the flow characteristics of a down-flowing gas-liquid column incorporating a submerged entry porous nozzle system are considered. A mode l based on one-dimensional drift flux analysis and critical Weber number fo r stable bubble size is presented. The model is used to predict the bubble size and gas void fraction as a function of the gas and liquid flow velocit ies within the bubbly flow regime, and can also be used to predict the gas and liquid flow conditions at which a transition from bubbly to churn-turbu lent flow occurs. Reasonable agreement was found between the model predicti ons and experimental measurements carried out in the column using an optica l fibre probe. The implications of these results for operation of submerged entry nozzle systems in the continuous casting of steel are also discussed . (C) 1999 Elsevier Science Ltd. All rights reserved.