Axial Flow Path Circuit A
Spiral Flow Path Circuit B
A dimpled sheet with a non-aligning dimple pattern is folded with a flow baffle between. The flow baffle extends part way from the circuit connections to the far edge of the sheet. The dimples are the spacers which form circuits A and B.
The Folded Sheet is then wound in a self-enclosing spiral. All edges are then welded, and this spiral bundle is finally contained in a jacket which forms the shell and contains circuit A.