The core technical principle of the microwave dryer is to use high-frequency electromagnetic waves to excite polar molecules (mainly water molecules) in the material to oscillate at high speed, and achieve rapid drying from the inside to the outside through intermolecular friction and heat generation without relying on external heat conduction.  1. Core principle: "Frictional heat generation" of polar molecules Microwave is an electromagnetic wave with a frequency of 300MHz-300GHz. Industrial drying commonly uses two frequency bands of 2450MHz (oscillations 2.45 billion times per second) and 915MHz (oscillations 915 million times per second). The drying process is divided into three steps: Energy penetration and absorption: Microwave energy directly penetrates the surface of the material (the penetration depth is usually a few centimeters to more than ten centimeters), is not blocked by the surface of the material, and is directly absorbed by internal polar molecules (such as water, protein, etc.).  High-frequency oscillation of molecules: In high-frequency electromagnetic fields, polar molecules will rapidly change their arrangement direction with the direction of the magnetic field, resulting in billions of rotations, collisions and friction movements per second.  Movement is converted into thermal energy: Severe friction and collision between molecules will convert kinetic energy into thermal energy, causing the internal temperature of the material to rise rapidly. After the water is heated, it vaporizes from liquid to water vapor, and is finally discharged through the dehumidification system to complete drying.  2. Key features: The core advantage that is different from traditional drying is based on the principle of "internal heat generation". Compared with traditional drying methods such as hot air and infrared, microwave dryers have three significant features: No heat conduction loss: heat is generated directly inside the material without the process of "external heating → heat conduction to the inside". The thermal efficiency can reach more than 80%, which saves 30%-50% of energy than traditional drying.  High drying uniformity: Microwaves can penetrate the entire material, avoiding the problems of traditional drying of "dry outside, moist inside, crusting on the surface", and is especially suitable for thick, porous materials (such as Chinese medicinal materials, wood).  Fast heating speed: The material can usually reach the target temperature within tens of seconds to minutes, and the drying cycle is shortened by 1/3-2/3 compared with traditional methods (for example, the drying time of vegetables can be shortened from hours to dozens of minutes).  3. Auxiliary systems: key components that support the implementation of the principle. The realization of the principle requires the coordination of supporting systems. The core components include: Microwave generator: The core is the magnetron, which is responsible for converting electrical energy into microwave energy and is the source of high-frequency electromagnetic fields.  Microwave cavity: a closed space made of metal to ensure that microwaves act concentratedly on materials while preventing microwave leakage (the amount of leakage must comply with the national standard ≤5mW/cm²).  Dehumidification system: timely discharge the vaporized water vapor through fans and air ducts (or vacuum pumps, vacuum microwave models) to maintain drying efficiency.  Temperature control system: Real-time monitoring of material temperature, avoiding local overheating by adjusting microwave power, and adapting to the heat sensitivity requirements of different materials (such as food and medicine drying that require low temperature control).