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.