Novel inner-cooling stop tube of PVC polymeric kettle

The utility model provides an inner-cooling stop tube of a PVC (polyvinyl chloride) polymeric kettle. The inner-cooling stop tube comprises an outer tube 7, a middle sleeve 6 and an inner tube 4 which are coaxial and arranged from the outside in; the upper and lower ends of the middle sleeve 6 are connected with the outer wall of the inner tube 4 to form an enclosed hollow cavity body; one end of the inner tube 4 is connected with a cooling water inlet 1, and the other end is communicated with the upper end of the outer tube 7 through a flow guide cylinder 8; and the lower end of the outer tube 7 is connected with one end of a connecting pup joint 2 which is communicated with a cooling water outlet 14. Cooling water enters the inner tube 4 from the cooling water inlet, passes through the top part of the inner tube 4, returns through the flow guide cylinder 8, then flows downwards along the annular space between the middle sleeve 6 and the outer tube 7, and then is discharged from the cooling water outlet 14 formed on the side wall of the connecting pup joint 2, therefore, the outer tube 7 is cooled. The inner-cooling stop tube of the PVC polymeric kettle has higher coefficient of heat transfer and can effectively improve the heat exchanging capacity of the inner-cooling stop tube.