(100b) Correlation of Power Numbers to a Full Spectrum of Reynolds Numbers for Agitation of Several Types of Fluids

The correlation between impeller power consumption and fluid viscosity are well studied based on dimensionless analysis - Power number (N_p) and Reynolds number (Re). But a generalized form to account for both Newtonian and non-Newtonian fluids has not yet established. In this paper, by combining experimental and numerical studies through three cases, we confirmed a universal correlation exists irrespective to the fluid types. We first examined 6 Newtonian fluids in a baffled vessel with pitched blades, dimensionless numbers generated show a strong correlation. Investigation then expanded to 10 various non-Newtonian fluids through rheology data measured using Anton Paar Rheometer. The resultant curve shows a generalized profile with a good mathematical fit. Theoretical analysis of the curves had given more insight on this correlation and helped understand the fundamentals of viscosity measurement by these devices. We expanded our study to characterize flow in a stirred tank vessel with Rushton turbine using computational fluid dynamics (CFD) method. With a total of 53 simulations of unsteady flow of both Newtonian and non-Newtonian fluids, Power number curves were generated for the full Reynolds number range, demonstrating a generalized curve. At lower Reynolds number, under laminar conditions, and are inversely correlated (irrespective of fluid type), which aligns with theory. And as expected, at higher Reynolds number, correlation is complicated, majorly because of turbulent eddies, and this is not the case for cone-plate Rheometer, where the flow is more controlled. Thecorrelation generated from this study provides guidance for process scale up/down and establishes the importance of operation condition for various fluids in different vessel configurations.