Radiation dryers encompass several types, including far-infrared dryers, high-frequency dryers, and ultrasonic dryers. These technologies utilize different forms of electromagnetic radiation to accelerate the drying process by directly interacting with the material’s molecular structure.
The electromagnetic spectrum spans from sunlight to microwaves, and while sunlight can only penetrate the surface of materials, it is not always efficiently absorbed. In contrast, infrared radiation is widely used for drying powders, sheets, and films, as it can be more effectively absorbed by the material. Most wet materials are poor conductors at standard frequencies (50–60 Hz), but their impedance decreases significantly at higher frequencies, allowing for better internal heating. This method enhances energy efficiency by targeting water molecules directly, reducing resistance and improving heat transfer. However, due to the high operational costs, this technique is typically reserved for high-value materials.
Radiative heat transfer drying involves the use of a heating plate that emits thermal energy directly onto the material. The effectiveness of this method depends on the type of radiation emitted and the material’s ability to absorb it. Traditionally, near-infrared wavelengths below 3 micrometers were used, but recent advancements have seen the adoption of far-infrared ceramic plates (over 4 micrometers), which offer better absorption of organic compounds. These plates provide superior surface absorption, making them ideal for coating applications. Studies show that most far-infrared energy is absorbed within the top millimeter of the material, and thicker materials may experience uneven heating.
Microwave drying has gained popularity in recent years due to its ability to penetrate materials deeply. It works by causing polar molecules and groups within the material to vibrate and generate heat through internal friction. This method converts electrical energy into heat with an efficiency of 60% to 70%, making it highly effective. Although pure microwave drying is costly, it can be used as an auxiliary tool during slower drying phases when traditional methods struggle. It is also useful in freeze-drying to remove residual ice.
Far-infrared dryers operate by emitting infrared rays that penetrate from the surface inward, leading to faster drying and improved thermal efficiency. Unlike light, these rays do not create shadows, ensuring even exposure.
High-frequency dryers work by placing materials in a high-voltage electric field, where water molecules move and generate uniform internal heat through friction. This method is particularly suitable for thick or poorly conductive materials, commonly used in wood processing.
Ultrasonic dryers use sound waves at specific frequencies to induce cavitation and intense molecular movement, accelerating the drying process. This technique is especially beneficial for heat-sensitive materials, as it minimizes thermal damage.
The conical twin screw is different from the parallel twin screw in appearance. Its two ends have different diameters. The diameter of the feeding section is large, while the diameter of the homogenization section is small, and the middle is gradually transitioned. The conical twin-screw is a meshing type, and most of them are counter-rotating.
Conical Twin Screw Barrel,Barrel Screw Extruder,Extruder Screws And Barrels,Injection Screw And Barrel
Zhejiang Jinteng Machinery Manufacture Co., Ltd. , https://www.jintengmachine.com