Flow Characteristics of Discharge Flow Region in a Stirred Vessel with Aeration

Abstract

The effects of liquid kinematic viscosity and operational conditions on the discharge flow field, which is the most important area in a stirred vessel with aeration, are investigated experimentally. The test liquids are 0.5 wt% polyacrylamide aqueous solution, 40 wt% and 60 wt% glycerol aqueous solution and water. The test gas is air.
The local liquid velocity in the discharge flow field in a stirred vessel with four baffles and a ring sparger is measured by an electrodereaction velocimeter consisting of four small spherical platinum electrodes. The effects of the liquid kinematic viscosity, the impeller rotational speed and the gas flow rate on significant factors such as velocity distribution which characterize the discharge flow field are discussed quantitatively. The way of estimation of the velocity distribution in the discharge flow field under given conditions is made clear. Additionally, new information is obtained about important factors for the discharge flow field : e.g., the shear rate based on the mean velocity takes larger values than that based on the fluctuating velocity.