Hi Bill,

Thanks for joining the fray.

At first I was also thinking the wing location for the radiator made a
lot of sense, but then thinking about the complexity of installation
caused me to reconsider. And along the way I found that the turbulent
characteristic of air adds greatly to its heat transfer
characteristics. Since turbulence drops exponentally with distance,
putting the heat transfer surface on the cowl near to the propeller
made more and more sense. That location allows people to go with the
"firewall forward" type of thinking and keep radiator hoses short.

As far as the aerodynamic effects, I hadn't figured there would be too
much effect because of the amount of heat added to this huge volume of
air. I guess it would make the air slightly less dense around the
fusalage and back dispating as the boundary air mixes with more of the
air mass.

p.s. What you were refering to a "flat plate" is really the
traditional blow through type radiator see on autos and other low
speed vehicles. Right?


"Bill Daniels" wrote in message ...
OK, Bob and Jay, chill out. You're both cool engineers and have a lot to
contribute. Lets just rattle the idea around a bit and see what comes out.

The skin radiator was been tried on the Schneider Cup seaplane racers in the
1930's and it worked, at least for that purpose. It probably worked much
better than the flat plate alternative seen on other aircraft from that era.
It might not have as much advantage over a highly efficient ducted radiator
like the P-51 used.

Skin radiators weren't really tried on military aircraft in WWII, at least
as far as I know, probably out of concern they would be very vulnerable to
enemy fire. After the war, people interested in performance were into jets
and not too interested in some weird pre-war radiator design even though it
might work fine.

Then there is a question of the effect of heating the boundary layer. Some
say that it will thicken and separate if the wing skin is heated. On the
other hand, some say it will have a turbulator effect and energize the
boundary layer. The Schneider Cup racers did not have laminar flow airfoils
so any effects, good or bad, might not have been noticed.

I have read a bit of work on "Hot Wing" aerodynamics and the results were
inconclusive as far as effects on the extent of laminar flow on the wing but
seemed to suggest a reduction in L/D which would be expected if the heating
disturbed the boundary layer.

It's possible, even likely, that a skin radiator would work best for cooling
and have the least negative effects on laminar flow if the surface chosen
were already subject to turbulent flow. The wing leading edge behind the
prop comes to mind.

Bill Daniels