Correlation of Power Consumption for Several Kinds of Mixing Impellers

The authors reviewed the correlations of power consumption in unbaffled and baffled agitated vessels with several kinds of impellers, which were developed in a wide range of Reynolds numbers from laminar to turbulent flow regions. The power correlations were based on Kamei and Hiraoka's expressions for paddle and pitched paddle impellers. The calculated correlation values agreed well with experimental ones, and the correlations will be developed the other types of impellers. 1. Introduction Mixing vessels is widely used in chemical, biochemical, food, and other industries. Recently scientific approaches were developed by Inoue and Hashimoto [1, 2]. On the other hand, the power consumption is the most important factor to estimate mixing performance and to design and operate mixing vessels. To estimate the power consumption, the correlation of Nagata et al. [3] has traditionally been used. However, this correlation was developed for two-blade paddle impellers, which do not always have the same numerical values of power consumption as those of multiblade impellers. Kamei et al. [4, 5] and Hiraoka et al. [6] developed the new correlation of the power consumption of paddle impellers, which is more accurate than Nagata’s. However, the new correlation also cannot reproduce the power consumption for other types of impellers. The propeller- and Pfaudler-type impellers are used for low-viscosity liquid and solid-liquid suspensions, and the propeller type has been widely used in vessels ranging from portable type to large tanks. Kato et al. [7] developed a new correlation of power consumption for propeller- and Pfaudler-type impellers based on the correlations of Kamei and Hiraoka. The power consumption for an anchor impeller was measured by Kato et al. [8, 9] in a wide range of Reynolds numbers from laminar to turbulent flow regions. In the laminar region, the power number of the anchor was reproduced by the correlations of Nagata and Kamei et al. by considering the anchor as a wide paddle impeller. In the turbulent region, it was reproduced by the correlation of Kamei et al. without the correction of the parameters. In this paper, the authors reviewed the power correlations developed by authors in unbaffled and baffled mixing vessels with several kinds of impellers. 2. Experimental Figure 1 shows a photograph of mixing impellers used in this work. Figure 2 shows the geometry of impellers with symbols. The mixing vessel used is shown in Figure 3. The vessels for the measurement of power consumption are flat-bottom cylindrical ones of inner diameter and 200？mm.