OPTIMAL IMPELLER CLEARANCE FOR A DUAL STIRRED UNBAFFLED TANK WITH A CONCAVE BLADE IMPELLER

An experimental investigation of unbaffl ed stirred tanks is carried out with the use of a dual concave blade impeller to evaluate the mass transfer coeffi cient, power number, and vortex depth. The effect of the impeller clearance on mass transfer is analyzed to estimate the optimal impeller clearance for lower and upper impellers. It is found that the lower impeller positioned at 0.25 of the tank diameter with the clearance between the lower and upper impellers equal to 0.38 of the tank diameter gives the maximum mass transfer coeffi cient. A comparison with the results for dual Rushton and Rushton-concave impellers at the optimal clearance shows that the concave-concave impellers are most effi cient. The scale-up criteria for optimal, geometrically similar systems of unbaffl ed stirred tanks with a dual concave impeller are proposed.
An experimental investigation of unbaffl ed stirred tanks is carried out with the use of a dual concave blade impeller to evaluate the mass transfer coeffi cient, power number, and vortex depth. The effect of the impeller clearance on mass transfer is analyzed to estimate the optimal impeller clearance for lower and upper impellers. It is found that the lower impeller positioned at 0.25 of the tank diameter with the clearance between the lower and upper impellers equal to 0.38 of the tank diameter gives the maximum mass transfer coeffi cient. A comparison with the results for dual Rushton and Rushton-concave impellers at the optimal clearance shows that the concave-concave impellers are most effi cient. The scale-up criteria for optimal, geometrically similar systems of unbaffl ed stirred tanks with a dual concave impeller are proposed.
Author:  T. T. Devi and B. Kumar
Keywords:  concave blade, clearance, mass transfer, power number, Rushton impeller, unbaffl ed tank, vortex
Page:  950