Is Infrared Scattering Considered When Using Carbon Fiber Heating Tubes to Dry Wet Materials in Industrial Production?

In industrial production, electrical heating is commonly used to heat and dry wet materials. The main drying principles include the following: the first involves heating materials through a high ambient temperature to achieve drying; the second uses microwaves to heat and dry materials; the third employs infrared radiation heating; and the fourth involves low-temperature dehydration drying. These processes vary in technique but share the same goal: to expel moisture from wet materials, resulting in a dry product to reduce storage and transportation costs and storage duration.

Today, let’s briefly discuss whether we need to consider the microscopic structure of materials and their effect on the reflection and scattering of infrared radiation when using carbon fiber heating tubes for drying.

The scattering intensity of radiation by liquids and solids is directly proportional to their thermodynamic temperature and is affected by the material’s density, typically increasing with greater density. Additionally, it is related to the liquid’s surface tension, increasing as surface tension decreases. Water has the highest surface tension coefficient, thus exhibiting lower radiation scattering compared to other liquids.

When mid to long-wave infrared radiation interacts with starch granules or plant cells, it excites complex vibrations. Therefore, the vibrations of a particle are not constant, and the particle’s scattering of radiation includes the combined effects of reflection, refraction, and secondary radiation.

Scattering phenomena at the molecular level generally occur where the material is heterogeneous, such as areas with density gradients, moisture gradients, temperature gradients, anisotropy, and structural inhomogeneities. Irregular pores and capillaries within the material, along with the edges of capillary liquid surfaces, can cause radiation scattering and changes in the direction of radiation. Thus, when studying the heating effects of carbon fiber heating tubes’ infrared radiation, it is necessary to consider whether these scattering effects could impact the radiation.

The pore walls and cell membranes of plant materials consist of colloidal particles, which serve as scattering centers in the material, leading to multiple scatterings. Even in materials less than 1μm thick, more than two instances of multiple scatterings can occur, absorbing radiation energy. Consequently, the characteristics of the material and radiative heat transfer are closely linked.

Substances like wood, tea, and fruits have porous colloidal structures that exhibit high absorption bands for infrared radiation around a wavelength of 20μm. This high absorption is due to all components of the porous colloidal structure absorbing the infrared radiation. Therefore, when using carbon fiber heating tubes to heat or dry these materials, it is essential to match the peak absorption wavelengths of the materials.

Materials containing moisture, especially within specific spectral bands, exhibit low reflectivity to infrared radiation. This is particularly noticeable in the surface layers of wood containing moisture, leading to reduced reflectivity. As moisture content increases within these spectral bands, the absorption rate of infrared radiation energy also increases.