Relationship between hydrodinamic parameters and phase segregation in helically coiled tube flocculators

Name: Bruno Peterle Vaneli
Type: PhD thesis
Publication date: 22/03/2022

Namesort descending Role
Edmilson Costa Teixeira Advisor *

Examining board:

Namesort descending Role
Davidson Martins Moreira Internal Examiner *
Edmilson Costa Teixeira Advisor *
Eduardo Cleto Pires External Examiner *
Edumar Ramos Cabral Coelho Internal Examiner *
José Antônio Tosta dos Reis Co advisor *
Marcelo Libânio External Examiner *

Summary: Models for estimation of Efficiency of Turbidity Removal (ETR) in Helically Coiled Tube
Flocculators (Portuguese acronym: FTHs) have been developed to support the
understanding of the relationship between hydrodynamics and flocculation efficiency
in FTHs. Nevertheless, in the context of developing such models there were no
biphasic flow modelling, and, therefore, it was not possible visualizing and analyzing
the solid-liquid flow behavior and phase segregation in the FTHs, generating scarcity
of information about what is occurring inside of these units in terms of fluid-particle and
particle-particle interaction. This scarcity leaves ETR estimation models with “black
box” aspects regarding flocculation. In this context, this study sought to clarify the
relationship between hydrodynamic parameters and phase segregation in FTHs,
aiming to advance the understanding of flocculation in these units. For this, several
configurations of FTHs were evaluated through computational fluid dynamics (CFD)
modelling. In total, there were modeled 84 configurations considering single-phase
flow and 54 configurations considering biphasic flow (solid-liquid). The hydrodynamic
parameters studied were the Mean Velocity Gradient, the Mean Pressure Gradient and
the Mean Specific Kinetic Energy. The solid phase was evaluated through the
distribution of its volumetric concentration in the FTHs. Among the results, existing
relationships between the hydrodynamic parameters, the volumetric concentration
distribution of the solid phase and the ETR in the studied flocculators were identified
and evaluated; it was verified a tendency that the greater the intensity of the secondary
flow in the FTH, the greater the magnitude of the maximum volumetric concentration
of the solid phase (CMax), which is close to the internal side of the curvature. Regarding
the hydrodynamic parameters, there was a positive relationship between them and
CMax; for the FTHs studied, it was verified that lower values of ETR were associated
with higher values of the CMax. As a result of the acquired knowledge, it was proposed
a new model for ETR estimative in FTHs. This model, in addition to producing fit
statistics similar to the best performance available models, it is more parsimonious and
all its parameters can be obtained through physical modeling, among other

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