Enhancement of Macromixing Performance of a Stirred Tank with a Novel V-Shaped Punched Baffle

A V-shaped punched baffle (VSPB) is developed to enhance fluid mixing in a stirred tank by producing impinging jet streams from face-to-face holes. Macromixing experiments and computational fluid dynamics (CFD) simulations are conducted with water and 0.5 wt % hydroxyethyl cellulose (HEC) solution as fluid to compare the performance of a standard baffle (SB), standard punched baffle (SPB) and VSPB. The experimental results show that the mixing time of VSPB is reduced by a maximum of 23 and 14.7% compared with those of SB and SPB at low speeds, respectively. With increasing stirring speed, the mixing time of all three baffles tends to be the same, but the power consumption of VSPB is less than that of SB and SPB with a Rushton turbine (RT). The simulation results show that the punched baffle can significantly increase the tangential velocity and turbulent kinetic energy of the fluid in the baffle region. Moreover, tiny vortices are at the back side of the punched baffles when the fluid is water. However, for a HEC solution, the flow field near the tank wall becomes disordered due to shear action caused by baffles and forms irregular vortices.