"Bill Daniels" wrote

Seems counter to say that a skin radiator won't cool an engine but won't
de-ice either. Last I checked, ice melted at 32F and coolant is usually
180-200F. If the skin radiator won't transfer heat to the airstream,
it'll
get damn hot. If the heat won't melt ice, it's going somewhere.

It takes a lot of energy to melt ice. What is it, specific heat? I can
never remember if it is that, or latent heat, from my high school chemestry.

Ever notice how small the radiators are, in a auto engine homebuilt? Lots
of the 4.3 Liter V-6's are using 2 Chevy air conditioner evaporators. How
much surface area, if it were all spread out? 3 or 4 square feet would be
my guess. Now take the wing of of a RV. What are they, 100, 120 sf? That
makes it 200 or 240 square feet, top and bottom. Oh, let's take off 20% for
ailerons and flaps... 190 or so. 47 times more surface on the wing, than
the radiator. How hot do you think that will get, with all of that air
zooming by at 150 + MPH. Yes, if you made the whole wing a radiator, the
coolant will get cooled. How much will all of it weigh?

Some time ago, someone in the group did some calculations, that pretty much
proved the case. They used the efficiency of an IC engine, then assumed
that all the rest of the BTU's produced by burning, say 10 gal/hr, that were
not used for HP went into the wing. They started with a thin layer of ice
over a given surface area, and calculated how much heat it wuld take to melt
that ice. The waste BTU's in that gas were far short of melting all of it.

I'd bet a 180F wing would melt ice pretty damn well with an OAT of 28F.

If you put the heat in a small surface area, say the first 6" of the leading
edge, yes. What happens after it runs back and re-freezes? Seems to me, a
commuter plane model had a problem with that type of thing, and a couple
crashed, a few years back.

If the wing was 180 without the ice, how well would the engine be cooling.
(or overheating)

Actually, the golden air age racers with skin radiators worked pretty
well.

Cites?

BTW, if heat won't transfer through a wing boundary layer, why should it
transfer through the boundary layer on a cooling fin?

Bill Daniels

I am not an aerodynamoisist, but I think there is something you are not
understanding, here.

I do not believe boundry layers apply, when the air is being forced past the
surface, with nowhere else to go, with a pressure differential.

Ever notice the lip on the cooling intake of a P-51? It is away from the
surface of the belly by a few inches, away from the boundry layer, to get to
where the air is flowing fast, and energetic, and pressure can be developed,
due to ram effect. The other big part of the equation is the negative
pressure behind the lip of the outlet.

How does your cite of boundry layer apply to a radiator?

For my final argument, why are wing radiators not commonplace? If you could
get the engine cooled, for no drag penalty, why is it not being done?
Surely Dick Rutan would have used it in Voyager, to eliminate the cooling
drag. What is cooling drag in a piston airplane? I seem to recall around
20% on most designs. 20% on Voyager would have been HUGE!
--
Jim in NC