X-Mozilla-Keys:                                                                                 

Paul wrote:
This is kind of trivial but if you don't ask for
it when you order your rad you probably won't get
it. The core I intend to use is a late model
Mustang core about 27 inches by about 19 or 20
mounted under the engine.

The header will be about 1.7 inches wide but the tubes
are only one inch. If it proves inadequate I have room
for doubling the thickness and running the hot water
in the back side and taking the cool water out the
front. This should result in roughly a 20% improvement
in core efficiency over a simple two row core..

See the drawing on the ACRE NL web site for this rational.

The water pressure drop will double over
the simple two row which is the down side of this arrangement.
Jeff is coming up with a better pump anyway.. hopefully. :-)

The air pressure drop should double which of course
is also the down side of a thicker core. There is
nothing I can do about that as there is only so much dynamic
pressure to work with. You can open up the duct intake
opening untill you are blue in the face but only so
much air will go through the rad. The rest will go around
the outside of the opening in an external diffusion manner.
The bottom line is it will have more drag.

So hopefully I can get by with a one inch core.

I also intend to use big cowl flaps to suck a lot of
air through during climb and close them down at cruise.

Paul Lamar

Al Gietzen wrote:

Paul;

I would think that this kind of baffling is un-necessary as long as
the pressure drop in the plenum, going sideways from the inlet, is
very small compared to the pressure drop in the tubes (which I'm sure
it is) all the tubes see essentially the same pressure and will flow
equally.

Al Gietzen

Perhaps you are right about this Al. I had a heavy duty truck rad guy
tell me that this was a problem. He said if you calculate the area of
all the tubes in a rad it comes out to way more area than the neck
pipes feeding in hot water and removeing (hopefully) cooler water.

I made a couple of calculations based on a real rad and sure enough
what he said about the areas was true. So what the heck. Better safe
than sorry. It does not add that much to the cost of the header tanks
as I will have to have them made anyway. I am not willing to use
plastic tanks crimped to the core with bent over aluminum tabs in 
my airplane such as is standard practice in automotive rads these days.

Paul Lamar
 
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