Experimental and CFD investigation on mixing by a jet in a semi-industrial stirred tank

This paper reports the results of a study on the flow generated and mixing time in a semi-industrial tank equipped with a side entry jet mixer. For this purpose, a three dimensional modeling is carried out using an in-house Computational Fluid Dynamics (CFD) code. In this study, the theoretical mixing curves predicted by the CFD were validated by experiments. The experimental mixing curves were obtained by monitoring of the homogenization progress of the dark blue Nigrosine solution inside the tank. A photometer equipped with an online detector was used for this purpose. The experiments were carried out for 0 degrees, 22.5 degrees and 45 degrees jet angle setups. The results showed that the mixing time in the 45 degrees jet layout is lower than other setups. The CFD code with the ability of simultaneous solving of the continuity, the Reynolds-averaged Navier-Stokes (RANS) equations and employing various types of turbulence models was used. The effect of the mesh size on the predicted results was investigated and the theoretical results obtained from various mesh sizes configuration were compared with the experiments. The results showed that the number of meshes is quite effective on the obtained theoretical results in a way that the predicted results for the largest mesh size were far away from the experiments. In addition, the two equation k-epsilon family models including: standard, RNG and realizable models were introduced to the code and the effect of these models on the predicted results was investigated. The results show that there are considerable differences between the predicted mixing progress using the three versions of the k-epsilon family models. The RNG k-epsilon model shows more convincing results in comparison with the other models. (c) 2005 Elsevier B.V. All rights reserved.