MIXING OF STRATIFIED LIQUIDS.

The batch mixing of initially stratified layers of hot water and cold salt solution has been studied. The experiments were carried out in baffled tanks of diameters 28. 8 and 90 cm employing centrally-mounted marine propellers. The mixing times were measured from thermocouple records taken at different positions in the tanks. It was observed that mixing takes place mainly by a mechanism of scouring or erosion of interfaces between liquids of unlike density. The mixing times depend on propeller size and rotational speed, initial density difference and vessel geometry. These effects are combined in a single dimensionless correlation of the mixing time data. A simple correlation for the energy efficiency of mixing (at low propeller speeds) is also given.