Working principle of Haomai drying equipment and how to select equipment

In order to select a suitable dryer and design the dryer size, it is necessary to know the drying characteristics of the material to the drying method used, the equilibrium moisture content of the material, the sensitivity of the material to temperature, and the temperature limit that can be obtained by a specific heat source. Our company has stock and prototype all year round, which can provide free sample recommendation for customers.

Working principle of Haomai drying equipment and how to select equipment

Drying process controlled by external conditions

In the drying process, the basic external variables are temperature, humidity, air flow rate and direction, physical form of materials, stirring conditions, and the method of holding materials in the dryer during drying operation. The external drying conditions are particularly important in the initial stage of drying, that is, when removing moisture from the non bonded surface. Because the moisture on the material surface diffuses around in the form of steam through the gas film on the material surface, this mass transfer process is accompanied by heat transfer, so strengthening heat transfer can accelerate drying. However, in some cases, the drying rate should be controlled. The air with higher relative humidity can not only keep the drying rate high but also prevent quality defects. In addition, if the drying speed of rhizome vegetables and fruit slices is too fast, it will lead to the increase of critical water content, which is not conducive to the increase of the whole drying process rate

Drying process controlled by internal conditions

When there is not enough free moisture on the surface of the material, the material begins to heat up and forms a temperature gradient inside the material after the heat is transferred to the wet material. The heat transfer is transferred from the outside to the inside, and the moisture content migrates from the inside to the surface. The mechanism of this process varies with the structural characteristics of the material. It is mainly diffusion, capillary flow and internal pressure due to shrinkage of drying process. When the critical moisture content appears until the material is dried to a very low final moisture content, the internal moisture transfer becomes the controlling factor. It is very important to understand the internal migration of moisture content. Some external variables, such as the amount of air used, usually increase the surface evaporation rate and at this point reduce the importance. If the material is allowed to stay at a higher temperature for a longer time, it is conducive to the process. This can make the internal temperature of the material higher, resulting in the vapor pressure gradient, so that the moisture content diffuses to the surface and makes the liquid moisture transfer at the same time. For the drying process controlled by internal conditions, the strengthening means of the process is limited. If allowed, it is very effective to reduce the material size to reduce the diffusion resistance of moisture. Vibration and pulse are beneficial to the diffusion of internal moisture.

Drying characteristics of materials

As mentioned above, the wet powder in the material may be unbound water or bound water. There are two ways to drain unbound water: evaporation and vaporization. It can be solved in rotary drum dryer.

If the material to be dried is heat sensitive, the evaporation temperature can be reduced by reducing the pressure, that is, vacuum drying.

During vaporization, drying is carried out by convection, and the heat is transferred to the material, and the air is cooled by the material, and the moisture is transferred from the material to the air and taken away.

How to choose a suitable dryer

In order to select a suitable dryer and design the dryer size, it is necessary to know the drying characteristics of the material to the drying method used, the equilibrium moisture content of the material, the sensitivity of the material to temperature, and the temperature limit that can be obtained by a specific heat source.

Our company has stock and prototype all year round, which can provide free sample recommendation for customers