Hydrodynamic characterization and flocculation process in helically coiled tube flocculators: an evaluation through streamlines

This paper presents a hydrodynamic characterization of helically coiled tube flocculators (HCTFs) through streamline analysis and an efficiency evaluation of the flocculation process in these units. Physical experiment and CFD modeling allowed to relate flocculation process (estimated indirectly by analyzing turbidity removal efficiency for low turbidity values and low Reynolds numbers) and hydrodynamic characteristics observed along the unit (represented in this study by streamlines). This work analyzes streamline features and proposes the use of a new global hydrodynamic parameter $$\overline{{E_{\text{k}} }}$$Ek¯, concerning the average specific kinetic energy in a representative streamline of the unit, aiming to compare hydrodynamic characteristics in units with distinct hydraulic and geometric characteristics. Results show that this parameter has a strong adherence with the maximum turbidity removal efficiency observed in HCTFs. Moreover, it was possible to define an optimum range of velocity variation cycles in the representative streamline to achieve the maximum turbidity removal efficiency. This result indicates that knowledge of HCTFs streamlines’ characteristics can support the rational design of this type of unit.

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