Effect of temperature change on transient organized structure of isolated mixing regions in stirred vessel

The present work experimentally investigated the effect of temperature change on geometric structure of isolated mixing regions (IMRs) in stirred vessel by the decolorization of fluorescent green dye by acid-base neutralization. A four-bladed Rushton turbine was installed in an unbaffled stirred vessel filled with glycerin as a working fluid. The temperature of working fluid was changed in a stepwise manner from 30 to 50 o C by changing the temperature of water jacket with which the vessel was equipped. The step temperature-change can dramatically reduce the elimination time of IMRs, as compared with a steady temperature operation. The characteristics of the twodimensional island structure of IMR were almost the same as in a steady temperature operation. It can be, therefore, considered that the transition of the IMR structure results from the dynamic change of flow structure due to increase of the Reynolds number with decrease of viscosity when temperature increases.