Compared with the continuous type, the periodic type has great flexibility, wide adaptability, easy adjustment of temperature and moderate temperature, and can perform humidity control treatment, while the forced circulation is more uniform than the natural circulation, and the loading quantity is large, the drying time is short, and the drying efficiency is high. . Therefore, periodic circulation drying chambers are often used in production. There are many structural forms of this type of drying chamber, and their performance characteristics are not nearly the same. Periodic forced circulation drying is divided into four types according to the arrangement of fans in the drying room: indoor top fan type, indoor side fan type, indoor end fan type and jet type.