REFLECTOR: updraft cooling

[Al Gietzen]

Subject: REFLECTOR: updraft cooling

 

I can understand why Burt Rutan and Nat Puffer are proponents of updraft
cooling. From an engineering point of view, it has a lot going for it. You
need more cooling when the airplane is climbing. If the cooling intake is
below the wing, the pressure is higher during a climb so you automatically
get more cooling during a climb. Similarly, it would be nice if cooling was
minimized during descent. The pressure is reduced under the wing during
descent, and so there is less cooling to the engine. Also, you've got
convection working with you instead of against you with an updraft system.

Doug;

 

I'd think that both climbing and descending are high AOA, and would have
similar air pressure under the wing; and given the strake configuration, it
is not clear that there is increased pressure during climb.  I also think
that the main reason for difficulties with the stock armpit scoops and
updraft is they are poorly designed scoops.  Need to have ever increasing
x-section after the entrance, and possilby placing them a bit further
outboard from the strake/fuselage intersection would be helpful. 

 

I have an 'armpit' scoop for my radiator which is very effective.

 

But the down draft is a lot simpler to implement, and that's probably going
to be the deciding factor for me.

 

And since it seems to work well, why not?  The amount of natural convection
driving force is likely overcome by a few knots of forward speed.

Al 

 

 

Doug Holub

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