Data on the hydrodynamics and power consumption induced by modiﬁed anchor impellers in cylindrical tanks

In the present paper, the data assembled concerning the stir- ring of a viscous Newtonian ﬂuid in cylindrical and unbaﬄed tanks is disclosed. The stirring is ensured by close-clearance impellers rotating at low speeds. This is a comparative study between three modiﬁed geometries of anchor impellers aim- ing to enhance the ﬂuid circulation in the whole vessel volume, and especially at the lower part of the vessel. The suggested geometrical conﬁgurations aim also to keep the energy consumption at its minimum. The data summarized here provides an additional knowledge for the best selection of stirrers for a speciﬁed industrial application.

Description of data collection Data were collected by means of numerical simulations, the RRF (Rotating reference frame) method was used. This last is very common in CFD applied to agitated tanks, it gives very accurate results and consists in fixing the impeller and considering the fluid domain as rotating around the impeller (considered as a relative reference frame). Data source location Faculty of Technology, University Hassiba Ben Bouali of Chlef, Algeria. Data accessibility Data is given in this paper. In addition, the CSV files of Fig. 5 are

Value of the Data
• The data reveal the efficiency of newly designed anchor impellers in agitated tanks.
• The reported research is valuable for industrial processes involving homogenization of highly viscous liquids in mixing systems. • The data provide information on the hydrodynamic and power consumption within vessels agitated by various designed impellers.

Data Description
The agitation in vessels is a widespread operation across different industries, technically easy to realize but difficult to characterize [ 1 , 2 ].
The data obtained regarding the agitation of viscous Newtonian fluids in cylindrical tanks is analyzed in this paper. A comparison is performed here between various geometrical configurations of anchor impellers. This geometrical design is generally employed for the agitation of highly viscous fluids at low Reynolds numbers (i.e., at low rotational speed), the so-called laminar flow regime [3][4][5] .
Three Tables and seven Figures are included and which summarize useful information on the flow patterns and power input for such devices. Table 1 resumes the required geometrical parameters of the stirred system. The geometry of the classical anchor impeller, as well as those of the newly designed impellers, are highlighted in Figs. 1 and 2 , respectively. Before beginning Table 1 Dimensions of the agitator.    the investigations, mesh tests and validation with experimental data were performed ( Table 2 and Fig. 3 , respectively). The results of power consumption are given Table 3 and Fig. 7 , while Figs. 5 and 6 illustrate the variation of axial velocity and shear rates, respectively. The same results of Fig. 7 are given in a tabulated form in Table 4 .

Materials
The performance of anchor-agitated tank is investigated in this paper. The standard setup consists of a flat-bottomed cylindrical tank with a diameter D and height H ( Fig. 1 ). The tank is completely filled with (Glycerol) with a density ( ρ = 1.26 kg/m 3 ) and a viscosity ( μ = 1.49 kg/m s à 20 °C). The agitator presented in Fig. 1 is a standard anchor with two vertical blades of height ( h ) and width ( a ) fixed on the extremities to a horizontal arm to favor the vertical motion of the flow. Some modifications in the geometry of vessel and impellers are introduced. The dimensions of the agitator, as well as the different cases studied are presented in Figs. 1 , 2 and Table 1 .

Method of investigation
The CFD (Computational Fluid Dynamics) tool has been used to achieve the investigations. The software employed (CFX) is based on the finite volume method. The geometry and mesh of the computational domain were generated with the computer tool Ansys ICEM CFD. The computations were conducted under the following considerations: steady-state, incompressible fluid, three-dimensional, and laminar flows conditions. The Rotating Reference Frame (RRF) approach was employed in modeling of the rotating elements. This technique has been selected due to the absence of baffles [6][7][8] . To achieve the velocity-pressure coupling, a pressure-correction method of the type Semi-Implicit Method for Pressure-Linked Equations-Consistent (SIMPLEC) was used [ 9 , 10 ]. The grids were refined near the impeller and vessel walls to capture the flow boundary details. To determine the optimal grid size for the computational domain, the mesh density was increased by about 2. Mesh tests were carried out by checking that the additional grids did not change the velocity magnitude in regions with high gradients by more than 2.5% ( Table 2 ). From these results, the mesh M2 with a global number of cells of about 835,159 was selected as optimal.

Validation
To verify the appropriate setting of boundary conditions and computational grid elements, some predicted results were compared against the available experimental data. Fig. 3 summarizes a comparison between our results of power number and the experimental data of Prajapati and Ein-Mozaffari [8] .

Data Obtained
After analysis of the velocity fields generated inside the tanks for both the flat-and curvedbottomed tanks ( Fig. 4 ), it is clear that the well-stirred region is the largest for Case No. 1 compared to the standard geometry with an energy consumption reduced by 1.65% ( Table 3 ).
A series of numerical simulations allowed us to deduce useful insights into the geometrical modifications that can enhance the flow circulation ( Figs. 4 and 5 ) and shear rates ( Fig. 6 ), especially in the area between the bottom of the tank and the inferior part of the agitator.
Case No. 3 gives satisfactory flow characteristics and a moderate energy consumption, as observed in Fig. 7 .

Data Analysis
The data assembled regarding the method of investigation, validation with experimental studies, as well as the main findings are analyzed and discussed in Figs. 3-7 and Table 4 . From  these results, it seems that the newly modifications in the classical anchor impellers are interesting. Among the suggested geometrical modification, Case No. 3 seems to be the most efficient, since it provides satisfactory flow characteristics and moderate power consumption.

Transparency document. Supplementary Material
Transparency data associated with this article (the CSV file of Fig. 5 , i.e. the tabulated form of the figure) can be found in the online version at … The model used in simulation (CFX file, the source file) is also available online.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships which have or could be perceived to have influenced the work reported in this article.

Supplementary materials
Supplementary material associated with this article can be found in the online version at doi: 10.1016/j.dib.2021.107669 .