International Journal of Technology (May 2019)
Numerical Study of the Hydrodynamic Characteristics in an Agitated Tank with Side-entry Mixer: The Effect of Stirrer Entry Angle
Abstract
The main objective of this work was to study the effect of stirrer entry angle on the hydrodynamic characteristic in an agitated tank with side-entry mixer (side-entry mixing tank) using CFD simulation method. For validation purposes, the simulation results were compared with the experimental results. It was found that similar fluid flow between simulation and experiment results qualitatively. The agitated tank system consists of 40 cm diameter cylindrical tank and a three-blades marine propeller having 4 cm diameter. The working fluid was water with a liquid height of 40 cm. Rotational speed varied between 100-400 rpm and stirrer entry angle () 0o, 10o, and 15o (right side). The modeling configurations used in this simulation are RNG Standard k-? model as a turbulence model coupled with Multiple Reference Frame (MRF) for the propeller motion approaching method in a transient condition. The results showed that simulation configuration MRF-RNG k-? gave realistic results to describe the hydrodynamic characteristics in the side-entry stirred tank. This is supported by simulation results that produced similar flow patterns between simulation and experiment qualitatively. In quantitative analysis, at higher rotational speeds the circulation flow that is formed tends to be pushed further from the impeller discharge and this statement is supported by average velocity data experimentally. Average velocity in the tank has a tendency to increase as the ? increases. The predicted average velocity (in m/s) are 0.0175, 0.0185, and 0.0197 at ? 0o, 10o, and 15o respectively in constant rotational speed (400 rpm). Larger ? produced high tangential velocity lead to a strong circulation flow. Further application of this side-entry mixing tank is for large scale reactors and storage tank to maintain the homogeneity of material inside.
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