Embedded vs Extruded Fin Tube for Air Cooled Heat Exchangers

How the bond is made

A G type tube has a helical groove machined into the base tube wall. The fin foot sits in the groove and the displaced parent metal is rolled back over it, so the fin is anchored rather than clamped.

An extruded tube starts with an aluminium sleeve over the base tube. Rolling discs push metal out of the sleeve to form the fin, and the same operation shrinks what remains of the sleeve onto the tube.

What each protects

The extruded sleeve covers the base tube along the whole finned length, so the atmosphere never touches the parent metal. In coastal plants and chemical plant atmospheres, that is usually the deciding factor.

A G type tube leaves the base tube surface between fins exposed. It compensates with a bond that holds at higher metal temperature than a wound fin.

Size and geometry

G type covers base tubes from 16 mm to 80 mm with walls from 1.65 mm to 4.0 mm - the larger range.

Extruded covers 10 mm to 51 mm with walls from 1.65 mm to 3.0 mm, and opens fin pitch as wide as 15.0 mm against the 5.0 mm maximum of the G type process.

Both reach 16 mm fin height; extruded starts lower, at 5 mm, for compact bundles.

Choosing between them

Corrosive atmosphere outside the bundle: extruded.

Base tube larger than 51 mm: embedded, because extrusion does not reach that size.

Dusty air that needs a wide pitch: extruded.

High metal temperature with a clean atmosphere: embedded.