The type, size and rotational speed of agitator have influence on the distribution of agitator power between total flow and turbulent fluctuation. Generally speaking, the power distribution of turbine agitator is beneficial to turbulent fluctuation, while that of propeller agitator is beneficial to overall flow. For the same type of agitator, under the same power consumption condition, the power of large diameter and low speed agitator is mainly consumed in the overall flow, which is conducive to macro mixing. For small diameter and high speed agitators, the power is mainly consumed by turbulent pulsation, which is beneficial to micro mixing. There are three methods of stirring: manual stirring, magnetic stirring and mechanical stirring. Artificial stirring can generally be carried out by means of glass rods. Magnetic stirring uses magnetic force, while mechanical stirring uses mechanical stirrer.

Mechanical agitator mainly consists of three parts: motor, stirring rod and stirring sealing device. The motor is the power part, fixed on the bracket, and its rotation speed is regulated by the governor. 搅拌棒与电动机相连，当接通电源后，电动机就带动搅拌棒转动而进行搅拌，搅拌密封装置是搅拌棒与反应器连接的装置，它可以使反应在密封体系中进行。 The stirring efficiency depends largely on the structure of the stirring rod. The old stirring rod introduced here is made of coarse glass rod. According to the size and shape of the reactor, the size of the bottle mouth and the requirements of reaction conditions, a more suitable stirring rod was selected.

The magnetic stirrer uses the principle of homogeneous repulsion and heterogeneous attraction of magnetic field to drive the magnetic stirrer placed in the container to operate in a circle, so as to achieve the purpose of stirring liquid, especially when the equivalent reaction is relatively small or the reaction is carried out under closed conditions. The use of magnetic stirrer is more convenient. According to the specific experimental requirements, the sample temperature can be heated and controlled, and the temperature conditions required for the experimental conditions can be maintained to ensure that the liquid mixing meets the experimental requirements. But the disadvantage is that for some viscous liquids or a large number of solid reactions, the magnetic stirrer can not be used smoothly, so the mechanical stirrer should be chosen as the stirring power.

Magnetic stirrers are usually used in food, biopharmaceutical and other fields. With the higher requirements of biopharmaceutical for the sterility and risk control of the shaft seals of agitators, industrial magnetic agitators came into being in Sweden in the 1980s. Lower magnetic stirrer has become the mainstream of the market, and continues to develop in the direction of simplicity, large torque, large shear force or very low shear force, bearing material safety, easy online cleaning, online sterilization. For example, the lower magnetic stirrer for bioreactor, the lower magnetic stirrer for high shear homogenization, etc. Whether it can prove that the agitator can be cleaned online and sterilized online, and the material safety of bearings has become the gold standard before the selection of biopharmaceutical agitators.

In addition, the desktop magnetic stirrer uses the same and exclusive characteristics of magnetic materials to drive the magnetic stirring rod to rotate by constantly changing the polarity of both ends of the base. The disadvantage is that the energy conversion efficiency is low and it is only suitable for small volume liquid stirring. Despite the wide application of desktop magnetic stirrers and magnetic rods, they are only limited to research and development and small-scale level. With the rapid improvement of domestic scientific research level, the application of magnetic stirrers will gradually expand in the future and become the leading instrument in the industry.