Power Correlations and Mixing Patterns of Several Large Paddle Impellers with Dished Bottoms

Abstract

Power numbers of several large two-blade paddle impellers in stirred vessels with dished bottoms were measured for a wide range of Reynolds numbers. Mixing patterns of these impellers with dished bottoms were observed for a wide range of Reynolds numbers by using a decolorization method based on the reaction between sodium thiosulfate and iodine. The power numbers of these impellers can be correlated with the modified correlation of Kamei et al. A relationship was established between the power number diagram (Np–Re diagram) and the shape of the isolated zone. At low Reynolds numbers, complicated isolated zones were observed, while a cylindrically rotating isolated zone was not observed.