Tom Kendall wrote:
<Snip!>
Bill's posting of the various ring type radiators got me thinking
(and out
of lurking!). I've been involved in the specification &
installation of
some large industrial cooling radiators over the last few years,
and part of
that involved going to inspect the fabrication facilities, tooling,
process,
etc. The techniques are Interesting, but definitely out of the
range of
what most homebuilders (even those on this list) would want to
tackle. Not
particularly complicated, just capital intensive.
All of the ring rads shown below are impractical for one-offs...
except
maybe the drum type. In that case, it looks to me like a
"pseudo"-drum
could be made by placing several small rectangular coolers
(automotive a/c
evaporator coils?) in a circle around the PSRU. The airflow could
be radial
from the "inside" of the drum made to the "outside" of the drum
(but inside
of the cowl). For optimum drag reduction and effectiveness, it
looks like
the spinner should be a bulbous one that actually starts slowing
the
incoming air before it gets to the cowl inlet.
The small individual rad segments certainly couldn't handle the
full cooling
flow, but ring supply & distribution headers shouldn't be too hard
to
braze/silver solder together. AN fittings at each segment... could
be very
inexpensive for materials, and quite effective for cooling. One or
two
segments might serve as very effective oil coolers with the rest
being the
water radiators. This should give a very stream-lined cowl, and
permit the
use of thin rads while still getting a pretty large heat transfer
area.
I don't have any figures for the sizes involved, but for Tracy's
PSRU,
there's probably about 8"-10" of stand-off to fit rads. Assuming
an 18"
diameter ring/drum, that makes for a face area of ~3 to ~4 square
feet.
Seems like it's in the ball park.
Problems could be things like difficulty in installation/removal
for
servicing the engine and/or PSRU (probably have to remove the prop
and take
the rad assembly off the front), attachment of the forward cowl to
the main
cowl body, mounting of the rad drum (to the PSRU adapter plate?),
and any
air requirements for ventilation of the engine comparment itself.
But
perhaps all surmountable.
Whaddya think all? Is this one worth kicking around any further?
Tom Kendall
The Do-335 was one of the fastest aircraft of WW2, which tends to
indicate that it had a very good cooling system, drag-wise. The
Germans
used the ring cowl on a number of different designs and these guys
were nobody's fools. My guess is that the ring cowl is the lowest
drag for a front radiator, but (as usual) the devil is in the details.
A segmented radiator should work, you'd need shock mounts and
you'd want cowl flaps. The ring-type cowl flaps looks like a lot of
work, but they are obviously do-able since all radial engined fighters
had them.
Have at it.
Bill Freeman
Here is a picture of a segmented radiator on a Orenda V8 powered
King Air.
Paul Lamar
Ops the picture did not go out. In fact I thought I had a picture
scanned but apparently not. I do have a picture around here somewhere.
Forget the picture :-)>
Paul Lamar
Tom,
Was thinking about a ring radiator for the super rebel about a year ago.
What I was considering was having the radiators for the oil and air coolers,
seperate. Having two blast tubes , one going to the turbo on the 20b and one
on the other side of the engine to keep coils, accessories, etc, cool. The
blast tubes would be set in the areas of the gaps of the radiators.
Definetely a cowl flap.
It would have a radial look. The cowl would be built to avoid the problems
of keeping an eye on the prsu and engine components. Reminded me of an old
timer who put a mirror under the cowl to keep an eye on a component that was
giving him problems.
The down side was not going over 26- 28 inches diameter for the frontal
area. Did the basic math, not even close for cooling of a 300 hp turboed
engine. Also cg would be moved way forward. Visibility for looking over
the nose of my tail dragger would be worse than that of a radiator under
the engine. Extra heat going over engine. Will be going with Tracys psru,
problems with mounting radiators around the psru. More length of heating
lines to cabin area. Trying to visualize running air over square/rectangular
radiators in a round cowl.....
This was as far as it got as a feasibility study.
Any ideas for what size cowl would be neccessary for a 200 and 300 hp ring
radiator install? Left my slide rule at work.....
Barny
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