Simultaneous Measurements of Flow Pattern Using Laser Doppler Velocimeter and Mass Transfer Coefficient:Effect of Interfacial Turbulence

摘要

The absorption of CO2 in water and aqueous solutions of monoethanolamine (MEA) and polyethylene glycol (PEG) were studied in the stirred cell assembly.Impeller speed was varied over a wide range of 0 to 70 rpm.While absorption was taking place,liquid phase flow pattern was also measured using laser Doppler velocimetry (LDV).The velocity-time data was analysed by eddy isolation model and eddy characteristics viz.eddy velocity,eddy length scale,eddy residence time/age,and their corresponding distribution were estimated.The age and size distributions were used for the estimation of mass transfer coefficient k_L.During the absorption of CO2 into water,interfacial turbulence was observed even at zero impeller speed,which was verified by the velocity-time data from LDV.A close agreement was observed between the predicted and the experimental values of k_L at all the impeller speeds.The close agreement was also observed at enhanced levels of interfacial turbulence (obtained as Marangoni effect during the absorption of CO2 in aqueous solutions of MEA) and for dampened turbulence (absorption of CO2 in aqueous solutions of PEG).