• Categories:IR Lamp Technologies & News
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• Time of issue:2024-02-23
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(Summary description)Infrared heating is a drying method that uses radiation to transfer heat. Emitting radiant energy is an inherent characteristic of various materials. When electrons inside the atoms of a material are excited and probed, alternating electric and magnetic fields will be generated, emitting electromagnetic waves. And propagates into space, which is radiation. Different excitation methods have different wavelengths of electromagnetic waves. The electromagnetic waves generated due to their own temperature or thermal movement are thermal radiation.

 



 

The electromagnetic radiation with a wavelength of 0.75 ~1000μm generated by the infrared or far-infrared emitter propagates straight to the dried leather at the speed of light. When the frequency of the emitted infrared  is related to the molecular motion in the leather, and matched the natural frequency of the leather, and the wavelength of the infrared radiation is equal to the wavelength absorbed by the leather, the molecules in the leather will intensify their movement, the absorbed infrared radiation energy is converted into heat energy, the temperature of the leather rises, and the water in it vaporizes, thereby drying the leather.

 

Every object has at least one absorption band in the electromagnetic spectrum. The fewer the absorption bands of an object, the weaker the absorption, and the smaller the ability of the material to absorb infrared radiation. For example, air has very little ability to absorb infrared radiation. Liquid water is one of the most active absorbers of infrared radiation. Dry substances generally easily transmit short-wave infrared radiation, but the presence of water in these substances significantly enhances their ability to absorb infrared radiation. Therefore, materials such as cellulose, sheepskin, felt and leather semi-finished products are particularly suitable for drying by radiation. Since leather absorbs infrared radiation, infrared radiation with a wavelength of 2.0μm ~ 6.0μm has a particularly significant drying effect on leather.

 

Leather is a thin, porous polymer material. During infrared drying, part of the energy will penetrate the leather, so that both the surface and the interior of the leather can obtain heat energy. As the water on the surface of wet leather continues to evaporate and absorb heat, the surface temperature of the leather will decrease, which will cause the internal temperature of the leather to be higher than the surface temperature, forming a temperature gradient, making the heat diffusion direction of the leather from the inside to the outside. At the same time, due to the temperature inside the leather Moisture movement caused by gradient always diffuses from the interior with more moisture content to the exterior with less moisture content. The wet diffusion of moisture inside the leather is in the same direction as the thermal diffusion, which will also accelerate the diffusion process of moisture, thereby improving Drying efficiency.

 

                                                     

 

Since the depth of radiation penetrating an object (the penetration depth) is roughly equal to the wavelength, medium or far infrared radiation with a longer wavelength has a better drying effect than near-infrared radiation. In particular, the emission frequency of medium-infrared radiation matches the natural frequency of molecules of polymer plastics, water, etc., which will cause the molecules of these materials to resonate violently, and these materials have strong absorption peaks for medium-infrared radiation. After medium or far-infrared radiation penetrates into the interior of these substances, it is also easily absorbed by these substances. Therefore, using medium or far-infrared radiation to dry leather is more effective than using infrared or near-infrared radiation.