It is necessary to apply the indispensable dryer with heat exchange function in papermaking, textile, chemical fiber and other industries. Multiple drying cylinders are contacted in sequence according to the process requirements, so that the coating (or paper) close to the surface of the drying cylinder can exchange heat between the drying cylinders. Under normal circumstances, the heat exchange medium (such as steam) is introduced through the rotary joint installed at the end of the shaft neck of the drying cylinder. After heat conduction, it condenses on the inner wall of the drying cylinder, and the condensate is discharged through the siphon inner pipe (or the joint at the other end) of the same rotary joint.