Hot spot analysis of heating materials in microwave drying oven

- May 06, 2019 -

Microwave drying box is a kind of cabinet microwave heating drying equipment for drying materials. It is mainly used for rapid heating and drying of chemical, electronic, ceramics, wood, food, paper products and other industries. Generally divided into galvanized steel plate and stainless steel inner liner, microwave drying box is microwave heating equipment, can only be used to dry materials that can absorb microwave heat, and materials that do not absorb microwave heat can not be heated and dried by microwave drying box. The heating characteristics of microwave drying chamber:

(1) penetration. Microwave can directly penetrate into the interior of the material and heat the interior and exterior equally, thus greatly shortening the heating room.

(2) selective heating. The microwave absorption of different materials is different. Generally speaking, the stronger the polarity of material molecules, the easier it is to absorb microwave. Water is a highly polar substance, which is very easy to absorb microwave and heat. The higher the moisture content of the material, the stronger its ability to absorb microwave, and the lower the moisture content, the smaller the microwave absorption. When the moisture content of materials in drying equipment is different, the part with higher moisture content will absorb more microwave, so it plays an automatic energy balance role in the chamber. Because of these characteristics, microwave is very suitable for drying.

(3) The heating response is fast and easy to control. The drying time lag of microwave heating is very short, and heating and heating are almost the same. Practice shows that the rate of microwave heating dryer is very high. This is mainly due to the following factors: first, when microwave heating drying, because of the evaporation of external water, the external temperature will be slightly lower than the internal temperature, heat transfer from inside to outside, water transfer from inside to outside, mass transfer and heat transfer are in the same direction, greatly improving the drying rate. In the traditional drying process, the temperature gradient of material is high outside and low inside, heat transfers from outside to inside, water transfers from inside to outside, mass transfer and heat transfer are reversed, and drying rate is greatly reduced. Secondly, microwave reduces the affinity of water molecules, especially between water and material molecules, which makes water molecules easily separate from material molecules and disperse outside.

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