CFD modelling of helically coiled tube flocculators for velocity gradient assessment

Sartori, Mariana Penha De Nadai; Oliveira, Danieli Soares de; Teixeira, Edmilson Costa; Rauen, William Bonino; Reis, Neyval Costa

doi:10.1007/s40430-014-0141-3

Cited by 19 publications

(11 citation statements)

References 22 publications

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“…Among several flocculation units with low retention time, the helically coiled tube flocculators (HCTFs) have been gaining prominence in scientific research (Gregory, 1981;Grohmann et al, 1981;Vigneswaran and Setiadi, 1986;Al-Hashimi and Ashjyan, 1989;Elmaleh and Jabbouri, 1991;Thiruvenkatachari et al, 2002;Carissimi and Rubio, 2005;Silveira et al, 2009;Vaezi et al, 2011;Sartori et al, 2015;Oliveira and Teixeira, 2017a, b). Retention times verified in HCTFs are considerably lower than retention times verified in conventional flocculation units (such as baffled flocculation units).…”

Section: Literature Reviewmentioning

confidence: 99%

Mathematical modelling and analysis of the flocculation process in low retention time hydraulic flocculators

Oliveira

Donadel²

2019

WSA

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This article aims to advance the understanding of particle interactions in low retention time flocculators and proposes a new flocculation model that appropriately considers the influence of retention time in flocculation processes. This consideration is important for units with flocculation time lower than 1 min, as seen in helically coiled tube flocculators (HCTFs), whose retention time is significantly lower than conventional flocculation units (about 30 min). With this, it was possible to obtain a more adherent model, reducing deviations between results obtained by physical modelling (using HCTFs, 48 tests) and those obtained with the proposed model, when compared with results obtained using the flocculation models commonly used for this purpose. The decreasing-rising behaviour presented by experimental data for process efficiency versus retention time, not verified in the benchmark models, was satisfactorily addressed by the proposed model. Furthermore, maximum and average absolute percentage deviations obtained using the model proposed in this study were less than or equal to the results obtained with the benchmark models and less for experimental uncertainty (10%). The results obtained indicate that this model can be a useful tool to support the rational design of low retention time units, including applications for the water industry and water recycling systems.

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Section: Literature Reviewmentioning

confidence: 99%

Mathematical modelling and analysis of the flocculation process in low retention time hydraulic flocculators

Oliveira

Donadel²

2019

WSA

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“…These parameters influence the hydrodynamic behaviour of the unit, which strongly affects the interaction between particles present in a liquid mass. This interaction is favoured in helically coiled tubes, whereas the presence of a secondary flow in cross section promotes a major interaction between particles previously destabilised, favouring the formation of flocs (Sartori et al, 2015). However, the flow's behaviour can promote destabilisation in flocs previously formed due to the shear stresses verified in helical flows, reducing the efficiency of the process over time.…”

Section: Mean Velocity Gradientmentioning

confidence: 99%

“…Furthermore, some studies evaluate the hydrodynamic behaviour in flocculators, aiming to better understand the process (Haarhoff and Van Der Walt, 2001;Sartori et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Experimental evaluation of helically coiled tube flocculators for turbidity removal in drinking water treatment units

Oliveira

Teixeira

2017

WSA

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The constant need to improve water treatment techniques allows for the emergence of new technologies for obtaining adequate water, both in terms of quality and quantity. In order to obtain an efficient, rapid and low-cost clarification system, this study proposes the use of helically coiled tubes (HCTs) as a coagulationflocculation reactor coupled with a conventional decanter system. Eighty-four (84) turbidity removal tests were performed to evaluate the proposed clarification system, while varying hydraulic and geometrical parameters in HCTs. Removal efficiency values higher than 80% were obtained (with a maximum removal efficiency of 86.2%), presenting better results than systems using baffled tanks, which are traditionally applied for water treatment purposes in developing countries. In addition, significantly lower processing times (lower than 2 min, about 10% of baffled tank processing times) were observed for high efficiency process values, indicating that this clarification system can be useful in rational design of coagulationflocculation units. It should be noted that the turbidity removal efficiency results obtained (with a risingthen-decreasing behaviour over time) differ significantly from those obtained by the commonly used models for flocculation evaluation (with asymptotic behaviour over time), presenting a maximum absolute percentage deviation of 48.9%, and indicating caution in the use of such models for alternative flocculation unit evaluation.

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“…A number of studies have shown this phenomenon, theoretically and numerically, for various types of flow and ducts (Cioncolini and Santini, 2006;Liu and Masliyah, 1993;Mondal et al, 2013;Sartori et al, 2015;Torres et al, 1991;Tse et al, 2011;Tuttle, 1990;Webster and Humphrey, 1997;Yamamoto et al, 1994Yamamoto et al, , 1998Yamamoto et al, , 2002Yanase et al, 1989Yanase et al, , 1994. However, there are only a few experimental investigations on flow patterns in the coiled units, especially regarding the evaluation of these units as flocculation units.…”

Section: Introductionmentioning

confidence: 99%

Revisiting Coiled Flocculator Performance for Particle Aggregation

Carissimi

Sanagiotto²,

Schettini³

et al. 2018

Water Environment Research

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This work summarizes recent studies evaluating the torsion and curvature parameters in flocculation efficiency using a hydraulic plug flow flocculator known as a Flocs Generator Reactor (FGR). Colloidal Fe(OH)3 and coal particles were used as suspension models and a cationic polyacrylamide was used for the flocculation. The effectiveness of the aggregation process (in the distinct curvature and torsion parameters, and hydrodynamic conditions) was evaluated by the settling rate of the Fe(OH)3 flocs, and flocs size by photographic analysis. As a result of curvature, a secondary flow is induced and the profiles of the flow quantities differ from those for a straight pipe. Results showed that the differences in the flocculator design influences the Fe(OH)3 flocs size and settling rates, reaching values of about 13 and 4 m/h, for the coiled and straight pipes respectively. Coal flocs generation was also shown to be dependent on the flocculator design and shear rate. Results showed that turbulent kinetic energy increases because of curvature when the torsion parameter is kept constant (pitch close to zero), enhancing the flocs formation.

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CFD modelling of helically coiled tube flocculators for velocity gradient assessment

Cited by 19 publications

References 22 publications

Mathematical modelling and analysis of the flocculation process in low retention time hydraulic flocculators

Mathematical modelling and analysis of the flocculation process in low retention time hydraulic flocculators

Experimental evaluation of helically coiled tube flocculators for turbidity removal in drinking water treatment units

Revisiting Coiled Flocculator Performance for Particle Aggregation

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