Effect of Temperature Change on Geometric Structure of Isolated Mixing Regions in Stirred Vessel

Nor Hanizah Shahirudin,Naoto Ohmura,Alatengtuya Alatengtuya,Takafumi Horie,Norihisa Kumagai

doi:10.1155/2012/287051

Nor Hanizah Shahirudin, Naoto Ohmura + Show 3 more

Open Access

https://doi.org/10.1155/2012/287051

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Abstract

The present work experimentally investigated the effect of temperature change on the geometric structure of isolated mixing regions (IMRs) in a 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°C to a certain fixed value by changing the temperature of the water jacket that the vessel was equipped with. The step temperature change can dramatically reduce the elimination time of IMRs, as compared with a steady temperature operation. During the transient process from an initial state to disappearance of IMR, the IMR showed interesting three-dimensional geometrical changes, that are, simple torus with single filament, simple torus without filaments, a combination of crescent shape and circular tori, and doubly entangled torus.

Highlights

Stirred vessels are frequently used to homogenize different substances, conduct chemical reactions, and enhance mass transfer between different phases
One thermocouple was set in the upper isolated mixing regions (IMRs), and the other one was set in active mixing region (AMR)
Influence of the free liquid surface at the top of the stirred tank makes the volume of the upper torus structure smaller than volume of the lower torus structure resulting in the elimination of the upper IMR first and later the lower IMR

Summary

Introduction

Stirred vessels are frequently used to homogenize different substances, conduct chemical reactions, and enhance mass transfer between different phases. These vessels are versatile and they are available in a wide variety of sizes and impeller configurations for use in industrial processes. Koiranen et al [1] proposed specific principles for effective mixing of highly viscous liquids or shear-sensitive materials in laminar flow mixing regimes. In these regimes, global mixing is inefficient due to the existence of isolated mixing regions (IMRs). Research studies on IMRs in stirred vessels have been conducted extensively, few have paid attention to the effect of temperature change on laminar mixing. This study, investigated transient behaviors of isolated mixing regions undergoing change of temperature in a stirred vessel

Experimental

Results and Discussion

Conclusion