Thanks for the comments and encouragement, Bill. I had considered
plumbing
my two radiators in parallel for the better efficiency, but after
doing a
little research I decided that the odds of ensuring even coolant flow
through both were uncertain. Several others who tried (including one
individual who tried a "gate" at the "Y" to balance the flow but found
that
what worked well at one rpm (coolant flow rate) did not work well at a
different rpm) did not find a satisfactory solution. The only person
I am
aware of successful using the parallel approach is Tracy Crook, but,
there
may be others. Besides the series approach was simpler to plumb in my
case.
I agree with Paul, that my new duct does not meet the K&M criteria
(too
short - for one thing), however, perhaps not too surprising, the
smoothing
of the inlet does seem to have improved the airflow into the radiator.
So
while not perfection, it provided encouraging results. The new duct
is
undoubtedly a bit on the small size at 9 square inches, but it did
reduce
total radiator inlet area from 48 sq in to 33 sq in. So perhaps one
upsized
to 15-18 sq in for both might be the right combination.
With the smoothed ducts apparently providing better cooling, I then
have
the
option of leaving them the original size inlet and having a "cooling
capacity reserve" perhaps for the hottest days (or "grin" perhaps more
power - turbocharger!) or reducing their inlet size in hopes of
lowering
some cooling drag.
Whether K&M, the "Wedge duct", or the latest of hanging it under the
fuselage and having the radiator act as duct, what is important is
that
your
installation provide adequate cooling - first and foremost.
The research that Paul has done over the years on cooling has from
time
to
time caused him to modify his view on the best approach. But then
that
is
what you would hope additional knowledge would cause one to do -
otherwise
why do any research at all. I understand Paul's "enthusiasm" with new
knowledge/understanding. However, at some point in working a project
you
have to commit to one approach with hopefully the best knowledge you
have
available at the time. If something better turns up then you have the
option
of sticking with what you started with (hopefully-good enough) or
making
the
necessary effort/changes to adapt to a perhaps better approach. No
one is
forced to adopted any particular approach and while I may not always
agree
with Paul, I (for one) certainly appreciate the research, findings
and
viewpoints that he shares with the group.
Keep it coming, Paul!
Ed Anderson
Thanks Ed.
Speaking of research Ed I think you and we would learn a lot if you set up
five pito
tubes equally spaced behind your rad measuring the air flow distribution
exiting the rad. After all that is what the curved ducts are all about.
Some static
pressure taps on the face of the rad would also help. Noting the
cooling ability is useful but measuring the pressures and velocities
is a far more direct way of developing duct shapes. This will also be a
reflection of any pressure build up on objects behind the rads.
Perry is currently using my water manometer but you can borrow it
when he is done with it.
BTW Bill, notice the pressure recovery of the K&M duct. Although it is
up from 20% of dynamic pressure to 45% of dynamic pressure it is still
a far cry from full dynamic pressure. Right side lower chart. This is
because you are feeding a porous surface. With the simple wedge system
by definition you have full dynamic pressure across the opening at the
start of the core as there is no duct.
Paul Lamar
Paul, I agree with the value of your suggestion on instrumenting for
airflow/pressure. However, since I have the PSRU with a mounting plate that
blocks or greatly interferes with (it extends over my rear fins about 3"
from top to bottom of each radiator and is a close as 2" to the fins)
approx 36 square inches of radiator area ( ouf of 180 in^2) or approx 20 %
of my cooling area, I'm not certain how much it would tell us about cores
for cooling.
A better choice would be someone with the cores mounted without the
interference behind them. One of the projects for the far future is a new
cowl design to overcome some of the constraints of where I could mount the
radiators under the stock RV cowling (and reduce some of the drag from my
hugh bottom cowl opening (28x4.5"). I have not yet come to love fiberglass
work, but after all the practice I think I can not do an adequate job with a
cowl.
Best Regards
Ed Anderson
Ed
I think you have a rather typical installation other than the plugs up.
You would also know the velocity of the air going through the
rad and could then get a good estimate of the over all mass flow
through the rad. I would still be interested in those numbers.
I guess what this illustrates is it possible to
build an adequate cooling system if you have enough volume in the rads
regardless of the aerodynamic efficiency of the system.
Paul Lamar
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