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From: "Al Gietzen" <ALVentures@cox.net>
To: "'Rotary motors in aircraft'" <flyrotary@lancaironline.net>
Subject: RE: [FlyRotary] Re: Belt rumnations; 
Date: Sun, 27 Feb 2005 10:19:37 -0800
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> PL may have been considerably off; but at .1hp with the EWP you will =
be
> getting only a fraction of the flow of the belt driven pump; even if =
it
were
> 100% efficient. =20

   But, Al, that's the whole point.  The stock pump is designed=20
to provide adequate cooling in stop-and-go traffic; it wastes=20
a lot of energy at cruise RPM.  If the losses due to conversion=20
are 25%, that still a *net* 7.4 HP gain - nothing to sneeze at. =20
---------------

Dale;

Stop and go driving has less of a cooling load than does continuous 75%
power.  More likely the pump has been designed to come close to handling =
the
cooling for WOT operation at any rpm.
=20
One of my concerns in the overall design of the cooling system was =
whether
or not the pump would provide adequate flow rate for a near optimum =
cooling
system design.   It turned out that it "just" does.  Yes, there will be =
some
excess flow at cruise because we have to design for full power climb, =
and
I'd estimate that excess about a hp; probably about equal to the power
conversion losses.

There isn't time or reason to go over all the factors again, I guess it =
is
all in the archives.  My conclusion is that there probably are reasons =
for
going to EWP, but in an airplane application; performance improvement =
isn't
one of them.  The lower flow rates can be offset by larger radiator =
volume
(and weight), but we don't really know whether the higher delta T is a =
good
thing for the engine.  You're free to draw a different conclusion.

Al