Study the effect of a new design of a twisted impeller blade on the vortexes formation and power consumption using a centric and eccentric stirred tank experimentally and numerically

Abstract

Vortex formation in stirred tanks is one of the problems facing many stirred tank designers. The current study depicts experimentally and numerically the effect of changing the impeller structure and its location in a twisted shape on the shape of the vortex, energy consumption, flow patterns, and turbulent kinetic energy. Numerically, the finite volume method was used, the mathematical model used the Volume of Fluid to simulate the free surface between air and water, and the mathematical model (k- ε ) was used to simulate turbulent flow. Rotational speeds of the impeller of different values ​​between (150-450 RPM) were applied, noting the effect of changing the location of the impeller experimentally and numerically on the flow parameters and other parameters. The current study showed that the rate of deviation in the values ​​of torque and energy consumption between the numerical and practical studies is relatively acceptable in addition to the convergence in the shape of the vortex. The results obtained showed that the shape and location of the impeller affect the shape of the vortex, and changing the rotation speed affects the growth and depth of the vortex. The study also showed that the amount of torque for the un-baffled stirred tank is less than that for the eccentric stirred tank, depending on the rotation speed. For example, at the rotation speed (350RPM) it was (0.034 N.m) and at the same speed, it was (0.093 N.m) for the eccentric location. The study also showed a comparison of flow patterns between the central and eccentric locations of the impeller.