Thermal roller and producing process

A thermal roller comprising:

• a cylindrical body extending along a longitudinal direction, said cylindrical body comprising at least one inner tubular element and at least one outer tubular element that is concentrically arranged around said inner tubular element, said inner tubular element comprises an outer diameter d and said outer tubular element comprises an inner diameter D, where D>d, the inner tubular element comprising two plug elements at ends thereof;
• two hubs that are each arranged at one end of the cylindrical body;
• at least one heat-exchange chamber between said inner tubular element and said outer tubular element;
• a coating layer coating said inner tubular element made of a plastic material, the coating layer comprising two portions extending in the longitudinal direction beyond the inner tubular element such that the two portions extending beyond the inner tubular element are closed in abutment between a respective one of the two hubs and a respective one of the two plug elements;
• at least one rib made of the plastic material of the coating layer and integrated with and extending from the coating layer thereby forming a unitary piece of the plastic material, the at least one rib being arranged along a helical path around the longitudinal direction;
• and
• at least one helical channel between said coating layer and said outer tubular element;
• wherein said helical path being made at least partially in said coating layer so that said at least one rib forms the side walls of said helical path.