Morgans wrote:

"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?

I don't know the area of a typical car radiator either, but I'm betting
it is much more than 3-4 square feet. Also, keep in mind that you only
need to de-ice the leading edge of the wing (look at how much boots
cover). So the area is probably closer to 2' times the wingspan which
means 50-80 sq. ft. one a typical light airplane.

And you don't need to coolant at 180F+ to deice a wing, so you can push
the coolant through a lot more area than a radiator and still keep
sufficient temperature to melt or prevent ice.


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.

Preventing it is easier than melting an accumulation to be sure. This
holds with other systems such as TKS as well.


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!

I'd guess cost and complexity would be two big reasons.


Matt