Abstract
This paper presents an numerical analysis influence of bottom shape on the hydrodynamic structure for cylindrical stirred vessel with bump. The turbulent flow generated in stirred tanks is numerically predicted by the resolution of the Navier-Stokes equation using standard k-ε turbulent model. Several parameters on the mixture efficiency has been investigated. Particularly, we have studied the bottom shape of the tank, which is the distance between the bump-turbine with down pumping direction and impeller diameter. The numerical obtained results of the CFD (computational fluid dynamics) code CFX V13.0 with the MRF (Multi Reference Frame) are presented in order to understand the flow structure. The three components velocity profiles and the turbulent kinetic energy dimensionless distributions obtained at bottom tanks with three different heights are analyzed and discussed. From these results, we can confirm that including a bump at the bottom center of the tank closer to the turbine improves significantly the operating conditions of stirring and mixing. Predictions have been compared with literature data and a satisfactory agreement has been found.
Highlights
The agitation-mixing is a very common operation in the industry process used to obtain close contact between two phases, to get a reaction or promote mass or heat transfer
Numerical simulations are conducted by Hao et al [1] to investigate the effect of bottom shape on the hydrodynamics and particle suspension in a DTB crystallizer
From instabilities on the dynamic flow Pieralisi et al [4] investigated by Particle Image Velocimetry (PIV) in two cylindrical stirred tanks with different dimensions, named T49 and T23
Summary
The agitation-mixing is a very common operation in the industry process (chemicals, food, pharmaceuticals, etc.) used to obtain close contact between two phases, to get a reaction or promote mass or heat transfer. Using PIV, Rodriguez et al [6] investigated in the flat bottom tank with the objective to evaluate the effects of conical shaped bottoms of different height on the fluid flow, configuration A (cone height, hcone= 5 mm; angle from the horizontal, αcone= 6.3°) and configuration B (hcone= 15 mm; αcone= 18.4°) They found that the flow in cylindrical bioreactors with conical bottoms is characterized by toroidal vortices expanding towards the bottom with increasing Froude number (Fr), as is the case for a standard flat configuration, while for the cone with the highest inclination examined (conical B) the vortices reaching the bottom at a lower Fr. Numerical and experimental studies carried out by Antonija et al [7] simulate the mobile type effect of agitation and its position in a cooling catalyst on increasing kinetic crystal borax decahydrate. The effect of the addition of a cylindrical bump in the center of dished bottom tank and the reduction of the bottom height with the same distance by realizing four geometries are investigated
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