Shear rate and mass transfer coefficient in internal loop airlift reactors involving non-Newtonian fluids

Abstract The shear rate and mass transfer coefficient play a key role in the chemical/biochemical processes and are considered as the most important parameters for the design of airlift reactors. Experimental investigations on the average shear rate and mass transfer coefficient have been made in internal loop airlift reactor. Tap water and glycerol–water solutions were taken as Newtonian fluids whereas non-Newtonian fluids include carboxymethyl cellulose and Xanthan in water. The average shear rate for the non-Newtonian fluids was estimated in terms of power due to aeration and rheological parameters. It is observed that average shear rate increased with increase in superficial gas velocity and decreased with increase in concentration. The apparent viscosity of the non-Newtonian fluids decreased with increase in superficial gas velocity due to increase in average shear rate. Overall volumetric mass transfer coefficient was evaluated by using dissolved oxygen concentration vs. time data. Volumetric mass transfer coefficient for Newtonian and non-Newtonian fluids is affected by superficial gas velocity and viscosity/apparent viscosity of the liquid phase. The overall volumetric mass transfer coefficients have been increased, with the increase in superficial gas velocity and decrease in viscosity/apparent viscosity of the Newtonian and non-Newtonian fluids and have been empirically correlated.