Effect of rheological parameters on non-ideal flows in the continuous-flow mixing of biopolymer solutions

Abstract

A novel study on exploring the effect of the rheological parameters of the yield-pseudoplastic fluids on the non-ideal flows in a continuous-flow mixer was performed. The rheological behavior of the xanthan gum solution, a yield-pseudoplastic fluid, was modeled by the Herschel–Bulkley model. In fact, varying the xanthan gum concentration changes the values of all rheological parameters (i.e. consistency index (K), power law index (n) and fluid yield stress (τy)) simultaneously. Thus, merely studying the effect of the xanthan gum concentration on the flow nonideality represents the combined effect of all Herschel–Bulkley model parameters. The core objective of this research was to investigate the effects of K (3–33Pasn), n (0.11–0.99), τy (1.7–20.6Pa), xanthan gum mass concentration (0.5–1.5w/v%), and feed flow rate (Q) (03.20–14.17Lmin−1) on the percentage of channeling (f) and fully mixed volume (Vfully mixed/Vtotal) in the continuous-flow reactor through computational fluid dynamics (CFD). The validated CFD model predicted that the percentage of the parameter f increased and Vfully mixed/Vtotal decreased as n was increased from 0.11 to 0.99. This result revealed that the mixing was improved when the extent of the shear thinning was increased. Moreover, the mixing effectiveness of the continuous-flow mixer was enhanced by decreasing the consistency index, decreasing the fluid yield stress, enhancing the residence time of the fluid in the tank (TR), and the reducing the solution mass concentration.