Weekly topic: What is the impact of the diameter, installation position of the agitator impeller in the slurry tank, as well as the baffles, on the mixing efficiency?

(1) Diameter ratio of the impeller to the mixing tank: If the impeller diameter is too small, the mixing action may not reach the periphery of the tank, resulting in insufficient mixing of the fluid in the outer layers. If the stirring diameter is too large, the space between the impeller and the tank wall becomes narrow, which weakens the axial circulation flow, is detrimental to stirring, and increases the impact losses between the fluid and the tank wall. Typically, the diameter ratio d/D of the impeller to the mixing tank is set between 0.35 and 0.5. (2) Impeller installation height: The ratio of the height C of the impeller above the bottom of the tank to the depth H of the liquid level in the tank affects the distribution of the circulating flow within the tank. When C/H > 1/5, two circulating flows are formed above and below the impeller, but material accumulation tends to occur at the bottom of the tank. When C/H < 1/7, the circulating flow at the bottom of the impeller can sweep across the bottom of the tank, preventing accumulation there. Typically, C/H = 1/7 is chosen. However, studies have shown that to achieve the same mixing effect, power consumption is minimized when C/H = 1/3. (3) baffles in the mixing tank: In a mixing tank, in order to improve the flow pattern of the fluid and enhance the mixing efficiency, baffles are often added; commonly, vertical baffles are installed on the inner wall of the tank. The function of the baffle is to suppress tangential flow; it is an effective method for eliminating vortices. It can convert tangential flow into radial and axial flow, increasing turbulence and the intensity of convective circulation, thereby enhancing the mixing effect.

The intensities of axial and radial flows generated by different types of impellers vary; therefore, the ratio between the impeller and the mixing tank must be determined based on the chosen impeller type!

I’m very interested in this topic, but I don’t have much experience yet.