Study on Internal Flow Characteristics of Non-Newtonian Fluids in Mechanical Stirred Tank

Mechanical stirring and mixing, which is widely used in industrial production, are mostly non-Newtonian fluids, which have different rheological properties (elastic effects, shear thinning and shear thickening) from Newtonian fluids. The internal flow characteristics in the lower stirring tank were studied. Based on the test results of the Lin-A315 paddle-type particle image velocimetry (PIV), the flow field characteristics of the non-Newtonian fluid in the stirring tank were simulated by steady/unsteady constant values. The axial velocity distribution, turbulent kinetic energy distribution, radial cross-section flow velocity profile, required stirring and mixing time and stirring energy consumption of xanthan gum solutions with different mass fractions under different stirring speeds were studied. The results show that the numerical simulation can be very effective. The flow field characteristics of the non-Newtonian fluid in the mechanical stirring tank can be simulated and analyzed well; increasing the stirring speed can increase the range and intensity of the main circulating flow in the tank, and the distribution of vortices and turbulent kinetic energy in the stirring tank will also increase accordingly, which is comparable to 100r/r/ Compared with min, the maximum axial velocity under the conditions of 300r/min and 500r/min increased by 3.6 times and 5.9 times, and the required mixing time was shortened by 0.46 times and 0.36 times; increasing the concentration of xanthan gum solution would reduce the flow rate. Therefore, compared with the change of non-Newtonian fluid solution concentration, the required mixing time is more sensitive to the change of rotational speed; in addition, increasing the stirring speed will increase the stirring energy consumption , therefore, medium speed should be selected for low concentration non-Newtonian fluids, and high speed should be selected for high concentration non-Newtonian fluids to facilitate solution mixing and energy saving.