Modelling and Simulation of Gas–liquid Hydrodynamics in a Rectangular Air-lift Reactor
-
Francesca Scargiali
,
Antonio Busciglio
Abstract
Computational Fluid Dynamics is a quite well established tool for carrying out realistic simulations of process apparatuses. However, as a difference from single phase systems, for multiphase systems the development of CFD models is still in progress. Among the two-phase systems, gas–liquid systems are characterised by an additional complexity level, related to the fact that bubble sizes are not known in advance, being rather the result of formation and breakage-coalescence dynamics and therefore of complex phenomena related to flow dynamics and interfacial effects. In the present work, Euler–Euler Reynolds-averaged flow simulations of an air-lift reactor are reported. All bubbles are assumed to share the same size, and a simplified approach is adopted for modelling inter-phase momentum exchange, that involves bubble terminal velocity as the sole parameter needed. Good agreement between simulation results and literature experimental data is found for all the gas flow rates simulated. This result implies that, despite the many simplifications that have to be adopted in order to make them viable, fully predictive CFD simulations of gas–liquid systems can give rise to reasonably accurate predictions of reactor fluid dynamics.
Nomenclature
| Ap | Particle surface, m2 |
| B | Vector body force N m–3 |
| CD | Drag coefficient, dimensionless |
| C1ε | Constant in k –ε model, dimensionless |
| C2ε | Constant in k – ε model, dimensionless |
| C3ε | Constant in k – ε model, dimensionless |
| Cµ | Constant in k – ε model (eq. [8]), dimensionless |
| Fβα | Interphase force term, N m–3 |
| FD | Drag force term, N m−3 |
| Fvm | Virtual mass force term, N m−3 |
| Flift | Lift force term, N m−3 |
| Gα | Term in turbulent kinetic energy transport equation due to body forces |
| N | Agitation speed, rpm |
| NP | Power number, dimensionless |
| Pα | Term in turbulent kinetic energy transport equation due to shear |
| Qg | Gas flow rate, m3 s–1 |
| Re | Reynolds number, dimensionless |
| Sk | Source or sink term in turbulent kinetic energy transport equation |
| Sε | Source or sink term in turbulent energy dissipation transport equation |
| U | Vector of velocity field, m s–1 |
| db | Equivalent bubble diameter, mm |
| g | Gravity acceleration, m s–2 |
| k | turbulent kinetic energy, m2 s–2 |
| r | volume fraction, dimensionless |
| uT | Bubble terminal rise velocity, m s–1 |
| Vp | Particle volume, m3 |
| Greek symbols | |
| α | Subscript for continuous phase |
| β | Subscript for dispersed phase |
| ρα | Density of the liquid phase, kg m–3 |
| ρβ | Density of the gas phase, kg m–3 |
| µ | Viscosity, Pa s |
| µτ | Turbulent viscosity, Pa s |
| ε | Dissipation of turbulent kinetic energy, m2 s–3 |
| σ | Surface tension, N m–1 |
| σK, σε | k – ε model parameters, dimensionless |
References
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Artikel in diesem Heft
- Masthead
- Masthead
- Editorial
- In Honor of Alberto E. Cassano: Researcher, Engineer, and Academic
- Articles
- From Ideal Reactor Concepts to Reality: The Novel Drum Reactor for Photocatalytic Wastewater Treatment
- Synthesis, Characterization, and Comparison of Sol–Gel TiO2 Immobilized Photocatalysts
- Determination of Kinetic Parameter in a Unified Kinetic Model for the Photodegradation of Phenol by Using Nonlinear Regression and the Genetic Algorithm
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- Modelling and Simulation of Gas–liquid Hydrodynamics in a Rectangular Air-lift Reactor
- Two-Dimensional Modeling of an Externally Irradiated Slurry Photoreactor
- Role of Aspect Ratio and Joule Heating within the Fluid Region Near a Cylindrical Electrode in Electrokinetic Remediation: A Numerical Solution based on the Boundary Layer Model
- Solar Water Disinfection Using NF-codoped TiO2 Photocatalysis: Estimation of Scaling-up Parameters
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- Microalgae Technology: A Patent Survey
- Influence of Physical and Optical Parameters on 2,4-Dichlorophenol Degradation
- Factors Capable of Modifying the Response of Pseudomonas aeruginosa to the Inactivation Induced by Heterogeneous Photocatalysis
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