Finned Coils

Finned coils are commonly used in lumber kilns. They typically consist of many aluminium plates (fins) spaced closely together across the coil surface. Copper tubes are pressed perpendicularly through these fins. The fins are perforated, and the metal around the holes is pressed downward to ensure tight contact with the copper tubes, creating a watertight seal.

This is the intended result—but not always achieved—which is the main issue with this model. If moisture enters between the aluminium and copper, the less noble metal (aluminium) dissolves. This can lead to large holes in the fins, breaking contact with the copper tubes.

Stainless steel fins can be used, but copper fins are much more effective. However, copper is expensive and usually not viable for heating applications. A fully copper finned coil is heavy and highly theft-prone.