Abstract
This experimental study describes the effect of the oscillating grid on hydrodynamics and mass transfer in an aquarium. The contribution of the two driving elements CO2 and oscillating grid is identified. Depending on the operating conditions, either these two effects add up and promote the circulation and transport of the liquid, or these effects are opposite, the liquid velocity is then reduced. On the other hand, with regard to gas-liquid mass transfer, the use of the grid is beneficial since, under certain operating conditions; the mass transfer coefficient is increased compared to that obtained without the grid. Analysis of the various energy contributions in the unit shows that the presence of the grid is justified only in cases where the CO2 flow rate must remain low. Flow characterization was performed using Particle Image Velocimetry (PIV) technique. The results were compared with previous studies. In order to perform the concentration field measurements by planar laser induced fluorescence (PLIF) technique and simultaneous PIV and PLIF measurements, the test bench was modified. The observations of velocity and concentration fields are in adequacy with the previous studies and allow to validate the bench. The necessary tools have been put in place, the study of mass transfer can continue.
Highlights
The optimal design of two-phase aquariums requires a great deal of knowledge in chemistry, mass or heat transfer, or in terms of the flow of circulating phases
Liquid circulation and CO2-water mass transfer are essentially dependent on the gas flow rate in the aquarium
The tracers used for the Particle Image Velocimetry (PIV) are hollow glass beads with a diameter of 10 μm
Summary
The optimal design of two-phase aquariums requires a great deal of knowledge in chemistry, mass or heat transfer, or in terms of the flow of circulating phases. The circulation is ensured with an ascending gas-liquid flow in the column These devices allow to work in important speed ranges ensuring a very satisfactory exchange between phases (gas-liquid) and improving productivity performances. They can be used in a wide range of industrial applications such as the continuous production of citric acid or the culture of different types of yeast or bacteria [1] or the growth of microalgae [2]. The objective of the study is to identify the hydrodynamic and mass transfer characteristics and the determination of velocity fields by the PIV method and CO2 concentration fields by PLIF
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