Internal circulation in carrier phase slugs and its influence on the local hydrodynamics in reactive liquid–liquid segmented flow: Visualisation and PIV studies

Abstract

Local velocity profiles and fluid circulation in liquid–liquid segmented flow significantly influence interphase mass transfer and associated chemical reactions in reduced dimensions. The present study considers a mass transfer-controlled pseudo first order reaction between iodine dissolved in toluene plugs (dispersed phase) and aqueous sodium hydroxide solution (carrier phase). The circulation patterns in the aqueous slugs observed during PIV experiments are correlated with the overall reaction rate. The extent of reaction is identified by decolourisation of the toluene plugs which is a result of iodine depletion. The experiments reveal that an increase in dispersed phase flow rate increases the circulation rate and local velocity within the carrier phase slugs. This is accompanied by propagation of reactant depletion zone from top to bottom within the organic plug and flattening of plug bottom. Nevertheless, the circulation remains axisymmetric with the stagnation region unchanged at r0 ∼ 0.74R.