Mixing performance of a non-Newtonian fluid in a coaxial agitated impeller reactor

•The inner agitators which produce axial flow were identified to be more efficient.•4-pitched blade turbine/anchor impeller is the optimized combination.•Evaluated for counter rotating mode in the full flow regimes. The power demand and mixing performance of three different coaxial mixers, fitted with either a Cowles turbine, 4-pitched blade turbine or 3-blade propeller impeller as the inner element, and anchor impeller as the outer element, were evaluated in a counter rotating mode in the laminar, transition, and turbulent flow regimes. CMC solution (sodiumcarboxymethyl cellulose) was used as the non-Newtonian fluid. The quantitative correlations for CMC solutions were established to calculate the power draw and the mixing time of the three coaxial mixers. The inner agitators which produce axial flow were identified to be more efficient than those which produce radial flow. Results show that the 4-pitched blade turbine/anchor impeller is the optimized combination among the three coaxial mixers tested, providing the shortest mixing time given the same power consumption. Based on mixing efficiency criteria, this study confirmed that the 4-pitched blade turbine/anchor impeller counter-rotating mode consistently yields the best results in the full flow regimes. Experimental set-up. Effect of mixing time Reynolds number on mixing efficiency in Laminar regime. [Display omitted]