The mixer is determined by multiple parameters, and it is impossible to describe a mixer with any single parameter. Shaft power (P), blade discharge (Q), pressure head (H), blade diameter (D) and stirring speed (N) are five basic parameters to describe a blender. The discharge amount of the blade is proportional to the flow criterion of the blade itself, the first power of the blade speed and the cubic power of the blade diameter. The shaft power consumed by stirring is proportional to the specific gravity of the fluid, the power criterion of the blade itself, the cubic power of the speed and the fifth power of the blade diameter. Under the condition of a certain power and blade form, the liquid discharge amount (Q) and the pressure head (H) of the blade can be adjusted by changing the matching of the diameter (D) and speed (N) of the blade. In other words, the mixer with a large diameter blade and a low speed (to ensure the same shaft power) will produce higher flow effect and lower pressure head. The small diameter blade with high rotational speed produces higher head pressure and lower flow. The only way to cause the particles to collide with each other in a stirred tank is to provide a sufficient shear rate. From the perspective of stirring mechanism, it is the existence of fluid velocity difference that makes each layer of fluid mix with each other. Therefore, every stirring process always involves fluid shear rate. Shear stress is a force that is the real cause of bubble dispersion and droplet breakage in agitation applications.
