Residence time distributions of in-line high shear mixers with ultrafine teeth

Abstract

The large eddy simulation and combined species transport method was validated for the residence time distribution (RTD) predictions of the pilot-scale in-line high shear mixers (HSMs) with ultrafine teeth. RTD characteristics were experimentally and numerically investigated under different rotor speeds and flowrates for the in-line HSM with double rows of inclined stator teeth. The exponential decays of the RTD curves indicate that the in-line HSM generally behaves like a mixed flow reactor, where the mixedness increases under higher rotor speeds and flowrates. It is indicated that the RTDs are greatly dependent on the HSM configurations, such as the shear gap widths, tip-to-base clearances, rows of the rotor and stator teeth, as well as patterns of the stator teeth. Defects of channeling, short circuiting and fluid re-entrainment are resulted from inefficient in-line HSM designs, such as those with large shear gap widths, large tip-to-base clearances, single rows of rotor and stator teeth, or improper angles of stator teeth. It is suggested that the in-line HSM with double rows of inclined stator teeth, narrow shear gap width and tip-to-base clearance has the advantage to provide intensified mass transport efficiency in the view of exploring novel chemical reactors.