Abstract
The velocity field and concentration distribution of three radial and axial impellers were studied in miscible liquid blending in a stirred tank reactor. To obtain a better insight into the applicability of each impeller system, the influence of velocity profiles on the generated concentration profiles was studied in detail for each impeller. Particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) methods were used as the measurement techniques. In the turbulent regime, the Rushton turbine provided a homogeneous concentration field throughout the reactor by generating high radial and axial velocities in the bottom and upper zones of the tank. Operation comparisons of the up and down-pumping pitched blade turbines illustrated that the up-pumping turbine had a better performance in overall because of producing high turbulence in the upper half of the reactor. In this region, the radial concentration profile approached the final homogenized value in a shorter time. In the laminar regime, all three impellers acted in a similar way and produced a radial flow throughout the reactor.
Funding source: Sahand University of Technology
Nomenclature
- C
Impeller clearance [m]
- D
Impeller diameter [m]
- H
Liquid height [m]
- k, k*
Turbulent kinetic energy, Normalize TKE
- N
Impeller rotational speed [rpm]
- NP
Power number, NP = P/ρN3D5
- P
Power (W)
- R
Tank radius [m]
- Re
Reynolds number, Re = ρND2/ µ
- T
Tank diameter [m]
- u, u’
Radial velocity, radial velocity fluctuations [m/s]
- Utip
Impeller tip speed
- v, v’
Axial velocity, axial velocity fluctuations [m/s]
- x, y
Radial and axial distance [m]
- µ
Viscosity [Pa.s]
- ρ
Density [kg/m3]
Abbreviations
- CCD
Charge-coupled device
- LDV
Laser Doppler velocimetry
- PBTD
Pitched blade turbine down-flow
- PBTU
Pitched blade turbine up-flow
- PIV
Particle image velocimetry
- PLIF
Planar laser-induced fluorescence
- RhB
Rhodamine B
- TKE
Turbulent kinetic energy
Acknowledgment
The authors would like to acknowledge the constructive comments by Prof. Vemuri Balakotaiah of the University of Houston, during the revision of this manuscript.
Research funding: This study is partially supported by the grants provided by the Sahand University of Technology, which is acknowledged.
Author contribution: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Conflict of interest statement: The authors declare no conflicts of interest regarding this article.
Employment or leadership: None declared.
Honorarium: None declared.
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