The trapezoidal section formed by the calendering of l-type finned tube is consistent with the heat flow density distribution, and the tube plates are closely combined with high thermal efficiency, eliminating the contact thermal resistance of the tandem finned tube due to the gap between the tube plates. Operating temperature: 230℃ features: high production efficiency, even blade spacing, good heat transfer, high fin ratio, the base tube can be protected from air erosion. Application: mainly used in petrochemical, power, paper, tobacco, building heating and other industries air cooler, air heater and food industry plant protein powder, starch and other spray drying system air heater.