(480d) Retreat Curve Impeller Flow and Heat Transfer Characteristics

Glass-lined vessels and impellers are often encountered in mixing operations, particularly in the pharmaceutical and fine chemicals industries.  Retreat Curve Impellers are designed without sharp edges to make them easy to coat with glass.  Although other more efficient glass-coated impeller designs are currently available, the retreat curve impeller is still in common use.  A number of studies, both experimental and computational, have been conducted to characterize the flow patterns, mixing times, power requirements and just suspended speeds of mixing systems using these impellers.  Very few studies have included the heat transfer characteristics.  This talk will present the procedures and results of a previously unpublished experimental investigation to develop tables and correlations for the Power Number, Flow Number, and Nusselt Number associated with a dished bottom vessel fitted with a retreat curve impeller of various diameters and off-bottom clearances, as well as different baffle arrangements.  The heat transfer data was obtained using a novel wall heat flux system with data for the vessel sides and bottom treated separately.  These correlations have been used to design and optimize numerous stirred tank vessels and processes.