Air-to-Water

This heat recovery variant is more complex but often more practical.

In a channel kiln, the outgoing air passes through a smooth tube coil made of stainless steel with copper fins. The incoming air passes through a coil of stainless steel with aluminium fins, but only when both airflows move in the same direction, as in channel kilns.

In a chamber kiln, both incoming and outgoing airflows must use copper fins, since airflow direction changes. Both ducts must be able to recover heat, which aluminium cannot handle in this case. The coils are connected by a pipe system and a controllable pump. Heat is transferred from one coil to the other as water is heated in one and cooled in the other.