A brief introduction to the mixing mechanism of planetary stirring woklet

Planet stir fry pan is a food processing plants for food hot working often used in a frying pan, widely used in all kinds of fillings, sauces, jams, and hot pot bed charge, donkey-hide gelatin made use of stirring, etc and all kinds of food, its pot in vitro model for hemispherical stainless steel pot body, stir means USES special tilting transmission, using a planetary mixer and the pot body full access, we all know that mixing operation is to realize the mixing between the materials. The mixing mechanism of the planetary stirring pan is mainly composed of three aspects, that is, convection mixing, molecular diffusion mixing and shear mixing. Here is a detailed analysis of the introduction.

Convective mixing of planetary stir-fry - pan mixing mechanism

In a planetary stirring pan, mechanical energy is transferred to the liquid material through the rotation of the agitator, resulting in forced convection of the liquid.

There are two types of forced convection, main convection and eddy current convection. Mixing process is realized under this function. The agitator transfers kinetic energy to the surrounding liquid, creating a high speed flow, which in turn pushes the surrounding liquid, gradually moving the whole liquid through the container. This large range of circulating flows is called "macroscopic flow", resulting in the whole container

The diffusion mixing of the range is called main convective diffusion. When the high-speed liquid flow produced by the agitator passes through the stationary or moving liquid with low speed, the fluid at the interface of the high-speed and low-speed fluid is subjected to strong shear action, so a large number of vortices are generated here. These vortices rapidly spread around, on the one hand, entrapment more liquid into the macroscopic flow, on the other hand, form a rapid and chaotic convective movement of materials in a local range. This swirling convective movement is called eddy flow, and the resultant mixing of convective diffusion in a local area is called eddy diffusion. The direct shear action of the agitator blade on the fluid will of course also cause strong eddy flow. The above two mixtures can be considered as "convective mixing".

In the actual mixing process, the main body convection diffusion can only mix different materials into larger "lumps", and through the eddy current diffusion between the interfaces of these "lumps", the degree of ununiformity is rapidly reduced to the size of the vortex itself. But small vortices are also much larger than the molecules, so convective diffusion cannot achieve a completely uniform mixing at the molecular level. This homogeneous mixing can only be achieved by molecular diffusion. Molecular diffusion is the result of relative motion between molecules. Although convection diffusion is only "macromixing", it greatly increases the surface area of the molecules breaking apart and reduces the diffusion distance, so it increases the rate of molecular diffusion, or "micromixing".

Molecular diffusion mixing in planetary stir-fry - pan mixing mechanism

Most mixing operations in food processing do not require a degree of micromixing. For the mixing of immiscible materials, there is no molecular diffusion phenomenon; The molecular diffusion is affected by convection mixing, which has a small effect on the mixing of miscible materials.

The mixing mechanism of low viscosity liquid is mainly convection mixing and molecular diffusion mixing. But for high viscosity materials, its density and viscosity are very large, in the mixing process of Zibo and eddy current almost do not exist, therefore, the effect of diffusion on mixing is very small.

The shear mixing of the mixing mechanism of the planetary stirring wok

The mixing mechanism of high viscosity materials is mainly "shearing". Shearing is the tearing of the mixed material into thinner and thinner layers, reducing the size of the area occupied by one component. For example, the mixing process of two kinds of viscous materials is as follows: at the beginning, a small number of components are randomly distributed in the mixture in a discrete form. Under the shear action caused by the movement of its boundary surface, these discrete materials are elongated, so that the system changes into a layer structure with alternate shades of color. If enough shearing is applied, each pair of thin layers becomes so thick that it is indistinguishable to the naked eye and appears as a uniform sheet of color.

In high viscosity fluids, the shear of the fluid can only be caused by the moving surface of the solid. The shear rate depends on the relative speed of the solid surface and the distance between the surfaces, so the ratio of the diameter of the agitator to the inner diameter of the container for use in a mixer of high viscosity materials is close to "1".

The above for the planet stir frying pan mixing mechanism for a detailed analysis, we can see that the planet stir frying pan mixing mechanism is determined according to the characteristics of the product, we in the selection, also need to pay attention to this point, through the food characteristics to choose to match the model.