Russell Kent wrote:

Paul,
Could you explain the text in the second image? (Hoerner on
ring-type radiators.)  I don't get the letter references, the last
type (d) is never mentioned and has 2 Cda's.

Russell Kent

Like a lot of stuff in Hoerner he does not fully explain it as most
data is from other references. In this case (5)
b) DB wind tunnel report #21 1941 and Zeppelin reports 600/185 1941
and 600/237 1941

The d) type is called a drum radiator. Kind of hard to make I would
guess. You will need to get the report references to learn more. Perhaps
the Library of Congress have them.

Paul Lamar

I think I'll disagree on that last one Paul.  All of the ring radiators have
axial air flow with radial tubes.  This requires the tubes to be splayed out
in the fin stack, and the fins themselves to be different lengths (varying
radii).  These really look difficult to make.

The drum rad on the other hand.... now that one has tubes running axially,
so they are all the same length.  The air flows radially from the ID of the
rad to the OD.  This kind of makes sense since the air will expand slightly
as it warms, requiring a larger flow area as it traverses the coil if you
want to keep the velocity low for good heat transfer.  The drum does this
naturally while the rings do not.  But the real beauty is that all the tubes
are the same length, and all of the fins in the stack can be punched with
the same die (all are circular segments of the same size and all of the
holes line up)!  So for a real radiator manufacturer with the tooling, a
drum is a piece of cake:  Stack up the fin stock, cut/punch the stack, space
'em all on combs, then drive all the tubes with the press (mandrels all
pre-positioned) in a single stroke.  All that is left is to sil-braze the
u-bends and fittings.

That part is all irrelevant for this list, except for the intrepid soul that
might want to take on arranging several flat coils into a segmented "drum"
of sorts.  That would probably be physically feasible, but as Barney pointed
out earlier, a lot of time/troubleshooting/effort.

Just bein' ornery.

Tom

 
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