Agitation of non‐Newtonian fluids

TLDR

Shear rate governs the rheological behavior of non‑Newtonian fluids, making it a key parameter in their characterization. The study aims to derive a general relationship between impeller speed and fluid shear rate. Using this relationship, the authors correlated power‑consumption data for three non‑Newtonian fluids with a generalized power‑number–Reynolds‑number plot, employing flat‑bladed turbines (2–8 in), tanks (6–22 in), and power inputs of 0.5–176 hp/1,000 gal across a 130‑fold Reynolds range. They found that rapid mixing of non‑Newtonian fluids requires substantially more power than mixing comparable Newtonian fluids.

Abstract

Abstract Since the shear rate of a non‐Newtonian fluid is of importance in fixing the rheological or viscometric behavior of such a material, the present study has been concerned with the development of a general relationship between impeller speed and the shear rate of the fluid. The resulting relationship was then used to interpret and correlate power‐consumption data on three non‐Newtonian fluids by use of a generalized form of the conventional power‐number–Reynolds‐number plot for Newtonians. Flat‐bladed turbines from 2 to 8 in. in diameter were used exclusively. Tank diameters ranged from 6 to 22 in. and power inputs from 0.5 to 176 hp./1,000 gal. The study encompassed a 130‐fold range of Reynolds numbers in the laminar and transition regions. The results to date indicate that power requirements for the rapid mixing of non‐Newtonian fluids are much greater than for comparable Newtonian materials.