This type of heating device is a closed type heating, suitable for external heating of various reaction kettles, enamel kettles, distillation kettles, rectification kettles, polymerization kettles and other non-standard containers. It has a large heating area, easy installation, operation and maintenance, and long service life. , The heat loss is small, the energy saving effect is significant, safe and reliable. It can be designed and processed according to the specific requirements of the container's external dimensions, material process requirements, material characteristics, and environment. It can also be designed and manufactured in sections according to the change of material liquid level. With air cooling function.