Mixing by agitation of miscible liquids Part II

Abstract

Abstract The performance of several types of agitators has been studied for the mixing of miscible liquids in batch operation. The time was measured necessary to homogenize two super-imposed layers of miscible liquids. An optical technique, known as the “Schlieren” method, was used to determine the moment at which uniformity is reached. In addition, the power consumption of the stirrers was measured. The influence of liquid properties and of the conditions of agitation was ascertained and could be explained. The results enabled relations containing dimensionless groups to be derived for both mixing time and power consumption. An important result of this study is the discovery that in the region of turbulent flow the mixing time is related to the pumping capacity of the stirrer. The mixing time appears to be approximately proportional to the time required to circulate the liquid once, this time being equal to the ratio of the liquid volume to the pumping capacity of the stirrer. General rules for the optimum shape and dimensions of the stirrers were established from the relations derived for mixing time and power consumption. A few experiments were carried out on steady-state mixing (continuous mixing) of liquids, the results of which were in agreement with those of the batch experiments.