Application of convective heat transfer method in material decompression drying process

Abstract

The invention relates to application of a convective heat transfer mode to the material pressure-reduced drying process. The method is mainly characterized in that in the traditional pressure-reduced drying process, when liquid water (or other solvents) starts to vaporize, a proper amount of steam is led in for heat exchange in the convective heat transfer mode, and the liquid water can obtain enough sensible heat to accelerate vaporization; and meanwhile, water vapor quickly gets rid of the constraint of material surface tension to escape by means of kinetic energy released by instant expansion of the steam and is discharged out of a drying cavity, and therefore full drying and drying time shortening are achieved.

Description

technical field [0001] The invention relates to the drying technology and its application field, in particular to the application of a convective heat transfer method in the decompression drying process of materials. Background technique [0002] Drying methods for materials generally include normal pressure drying, spray drying and reduced-pressure drying, and the present invention relates to the reduced-pressure drying method among them. [0003] The decompression drying method is currently a popular drying method. By reducing the pressure (atmospheric pressure is based on 101325Pa), the latent heat required for water molecules to change from liquid to vapor is also greatly reduced. For heat-sensitive substances or samples that are not easy to dry , such as flow paste or other bulk samples, the use of reduced pressure drying method can effectively shorten the drying time, while ensuring the quality of the material after drying. [0004] Therefore, for materials that requi...

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Problems solved by technology

The invention patent also discloses a drying method, indirectly suggesting that the starting point of the invention of the device is to use a method of partially breaking the vacuum, that is, to fill a small amount of air into the box to overcome the phenomenon of "inhomogeneous heat transfer in thin gas under vacuum." , so that the temperature of the item to be dried rises discontinuously, and the phenomenon of uneven heating occurs”

[0007] Experimental small box-type decompression drying equipment mostly uses heat radiation to complete heat transfer. The heating process of materials is from the surface to the inside. Because the air is thin under reduced pressure, it is difficult to form convective heat conduction, and the heat transfer efficiency is not high; production The box-type decompression drying equipment is usually equipped with a coil or a plate heating device. The material is heated mainly by heat conduction, and the heating process is from the bottom to the top; both methods can intensify the movement of water molecules, but they cannot solve the movement well. The problem of continuous, timely and rapid supply of latent heat required for water molecules in the liquid to gaseous state; decompression microwave drying method is to use the characteristics of the large dielectric loss coefficient of water molecules in the material to preferentially absorb microwave energy, so that the water dipole molecules produce high Frequent reciprocating motion produces "internal friction heat" so that the inside and outside of the material are heated at the same time, and the temperature rises at the same time, so the water molecules are quickly vaporized, and the energy efficiency is high. This is undoubtedly a solution, but so far it has not been successfully applied in industry. example, so the promotion and popularization are temporarily limited