ESEL Paper Review_201201102
By Hong Guo
Mail: hongguo@gist.ac.kr
Phone: (+82) (0)10 82276568
1, Title and Author
Title: The development and application of CFD models for water treatment flocculators
Journal: Chemical Engineering Journal
Authors:
J.Bridgemana,* , B. Jefferson b, S.A Parsons b
a School of Engineering (Civil Engineering), University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
b Centre for Water Science, School of Applied Science, Cranfield University, Cranfield, Bedfordshire, MK43 0AL, UK
2. Summary of Paper
This paper focused on development and application of simulation techniques and the analysis of computational models to increase understanding of floc formation and breakage mechanisms. It considers a range of modeling strategies and simulation techniques including, inter alia, steady and unsteady flow, two-equation and Reynolds stress turbulence modeling, sliding mesh and multiple reference frames approaches to rotational flow simulations, and mesh density optimization.
2.1 Results
The Fluent software was used to analyze in this paper. In addition, the following results would discuss about the simulation of realistic water treatment flocculation processes at both laboratory scale suing raw water samples.
2.2.1 Lab jar test
Under the condition of 100rpm, the authors found that ? (Energy dissipation rate) values of different zone for the various shapes of vessels are different. For the cylindrical vessel, the average ? value in the paddle tip zone was 3.5 times greater than that found in the vessel overall. On the other side, it would be the 5.0 times in the square vessel. The results showed that degree of turbulence generated in the paddle tip zone in the square vessel is significantly greater than the cylindrical vessel. However, the interesting thing is that both vessel, ? continuum./ ? vessel =0.5 and the higher ? values are generated in the square vessel; they are less well dissipated than in the cylindrical vessel.
2.2.2 Full scale flocculators
2.2.2.1 Velocity
The highest velocities are located towards the tips of the paddles. With a proportion of the flow returning, at low sped along the top or bottom of the vessel, the recirculation zone was set up and the recirculation flow pattern is observed in all flocculation cells of the channel. In addition, the dead areas are also found on the upper and lower corners of each cell.
2.2.2.3 Turbulence dissipation rate
For the mechanical flocculator, local turbulence dissipation rate values above the vessel average occurred around the paddle edges and in the wake of the paddle whereas for hydraulic flocculator local velocity gradient values greater than the average was found at the baffle wall tips and on the facing walls.
3. Contribution:
The CFD simulation of laboratory and full scale unit processes commonly found in water treatment works have done in this paper. Currently, there are many studies for the CFD application for the water treatments for research and industrial area could be found. Normally the researchers set the simple model for simulation and then run the real system. The realistic simulation faced many barriers. Combination of proper computer power and model application is the key points for the successful simulation. However, complex parameters for the realistic analysis would increase the computing cost. In the study, the author applied the both of high performance computing and laptop to do the successful simulation for the realistic. I think it would be the guideline for the future study and many research points could suggest valuable ideas.
4. Author information:
Email: j.brdgeman@bham.ac.uk