Analysis of the characteristics and working principle of laboratory Stirrer

Agitator design includes process design and mechanical design. The process design puts forward the original conditions of the mechanical design, that is, the processing capacity, operation mode, maximum working pressure (or vacuum degree), maximum working temperature (or minimum working temperature), physical properties and corrosion conditions of the stirred materials, etc. The type and area of ​​heat transfer surface, the type of agitator, the stirring speed and power etc. are put forward. The mechanical design should carry out reasonable selection, strength (or stiffness) calculation and structural design of the mixing vessel, transmission device, shaft seal and internal components.

(1) The use, medium characteristics, operating conditions, production capacity and installation methods of each stirring device belonging to non-standard equipment vary widely, and are often individually designed according to different functions, structures, materials and use requirements, so there are many varieties and specifications of stirring devices It is a typical non-standard equipment.

(2) It is the integration of mechanical and process technology expertise

On the surface, the stirring device is a mechanical product, which is made through mechanical design, material selection and mechanical processing; however, fluid engineering issues such as the selection of the stirrer, calculation of stirring power, flow field, and process amplification all belong to the category of technology . Therefore, the design of the mixing device needs to comprehensively use the knowledge of machinery, materials, technology, control and other aspects.

(3) Relying on experience and experiments, it is difficult to enlarge

　Two stirring devices with different scales but similar geometry, assuming that the fluids in the two tanks are the same, it is difficult to obtain the same flow velocity distribution in large equipment as in small equipment. Moreover, for many stirring operations, to achieve the same stirring effect, the energy input per unit mass of fluid in large equipment may be very different from that of small equipment. This makes it difficult to reproduce the process results in small plants, ie the scale-up of stirred tanks, in large stirred plants. So far, for the amplification of complex processes, it is still impossible to predict theoretically, and a large number of experimental studies are required. Sometimes, in order to increase the size of the stirring device, the test has to be carried out in large-scale experimental equipment, and the volume of the large-scale test tank even reaches more than 2000m3. Therefore, it can be said that stirring technology is still an engineering technology that relies heavily on experience and experiments.