Paul,
I enjoyed your book.
My current radiator, welded into a broad "v" shape, has about 330 cu in of
core volume, a little over 2 cu in per hp for my single rotor engine.

Most of the charts in your book suggest a number more like 3.6 in per hp.
I bought a nice radiator for a Volkswagen Golf.  Slightly bigger than the
Dodge Neon, but has a dual pass core, so both inlet and outlet are on the
same end. A little over 600 cu in.

I planned to mount this radiator under the wing, as illustrated in the
photos you provided of the Dragonfly.  Unfortunately, that position is
quite close in trail behind the cowl exit, including the muffler and
exhaust stacks.  The best I figure, the leading edge of the radiator would
sit about 5 inches below the fuselage, and 18 to 20 inches aft of the
exhaust.  I suppose the air at that point would be quite warm, even though
it would be mixed with the slipstream.  How far downstream would be okay to
place the radiator?  Would it be best to avoid the belly all together?

I could, with large modifications to the fuselage, mount the radiator in
the floor of the baggage area, and build intakes on either side of the
fuselage (or both) directing air in and down, to exit out the bottom.  This
is a big job, and would reduce the baggage volume by half.  Is it best to
commit to one intake, or make a dual intake leading to a single diffuser
over the radiator?  Any suggestions on the best way to mix two intake flows
into one?  Probably get a good look at a fighter plane, like a Harrier.

I am a little at a loss here.  There is no way to fit the larger radiator
in the cowling. (it is longer than distance firewall to spinner)  The belly
seems ill advised due to heat flowing back from the engine exhaust and
cooling exits.

I'm curious how much effect the warmed engine air would have on radiator
effectiveness on the belly.  How would this compare with using a marginally
sized radiator in the cowling with a heat augmented exit?  A cowl mounted
radiator would surely absorb some radiant heat from the engine anyway, so
is this sixes compared to a radiator downstream on the belly?

Lewis.

Normally the heat exchanger goes on the cool side of the engine vertically
mounted. The plugs up oil sump precludes that. The motor mount we sell is non symmetrical
for mounting the HE on the side.

The rule of thumb is one degree F increase in ambient temp is a 1% reduction in
cooling effectiveness. That is why it is best to put the diffuser between the
hot engine and the heat exchanger. It is best then to dump the hot air out
the bottom or the side of the cowl.

Radiation from the glowing red hot exhaust pipe must be shielded from the HE.

Paul Lamar

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