Proposição de modelo de previsão de desempenho de unidades de floculação tubulares helicoidais

• Autor(a) principal: Oliveira, Danieli Soares de
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/10320
• topic: Computational fluid dynamics.; Turbidity removal efficiency; Helically Coiled Tube Flocculators; Hydrodynamics; Flocculation; Mean Velocity Gradient; Floculadores tubulares helicoidais; Eficiência de remoção de turbidez; Gradiente Médio de Velocidade; Engenharia Sanitária; Fluidodinâmica computacional.; Floculação.; Água - Purificação.; Hidrodinâmica.; 628

The use of Helically Coiled Tube Flocculators (Portuguese acronym: FTHs) in water clarification systems has shown high efficiency in removing turbidity, and short process times, compared to units commonly used for this purpose. Oliveira (2008) shows an estimation model for removing turbidity based on geometrical and hydraulic characteristics of 84 FTHs. However, the author does not take the hydrodynamic characteristics of the unit into account, which are highly important for the interaction between the particles present in water and, consequently, for the formation and destructuring of flocs. Therefore, this thesis presents an improved model for efficiency estimation of turbidity removal based on Oliveira’s (2008), focusing on hydrodynamic aspects of flocculation. For this purpose, hydrodynamic characterization of FTHs was enhanced using computational fluid dynamic modelling (CFD), which allowed us to employ alternative methodology to determine the mean velocity gradient parameter ( ) through hydrodynamics. This parameter is highly significant for designing flocculators. This methodology has strong physical basis, high determination coefficient when correlated to values obtained hydraulically (R²=0.96), and low mean deviations compared to results obtained through commonly used empirical models (15.8%). This means that it is a good tool for determining . The search for improving the reactor hydrodynamic characterization took four other hydrodynamic parameters into account: swirl number ( ); mean specific kinetic energy ( ), vorticity ( ) and helicity ( ). Inserting these parameters allowed achieving an efficiency estimation model for turbidity removal more adherent to the physical process, compared to Oliveira’s (2008). This higher adherence is measured by the ability to satisfactory foresee the ascending-descending behavior of turbidity removal efficiency throughout the process, verified by physical modelling. This is not allowed by any other analytical model available in the literature about continuous flow flocculators. Also, both the determination coefficient and the mean absolute deviation percentage showed significant improvement, going from 0.83 to 0.92, and from 2.4% to 1.7%, respectively. These results show that the model proposed in this study is very promising to assist in designing rational FHTs.