I recall an article on
some experiments done on inclined radiators in race cars.
Basically the figures
that George mentioned were quoted in the source. However (big however)
what may not have been clearly pointed out was that the major part of the reason
cooling effectiveness (not efficiency) increased was that inclining the heat
exchanger permitted you to install ever larger area cores in the same size
duct. So the increase in cooling effectiveness by inclination was in large
part due to the larger size radiator permitted by inclined placement in the
duct.
For example take a duct
that is 24” wide (X) and 12” high (Y) at zero degree inclination. If you
incline the radiator by 30 deg and then increase its height to again fill the
duct,. you can get an approx 15% increase in the frontal size of the radiator
(in the same 24x12 duct). At 60 deg you could gain approx 100% increase in
frontal size by again increasing the height of the core to fill the duct.
. Naturally that aids in getting rid of the heat. They also point out the
larger core adds weight until you reach a point where the adverse effect of the
heavier radiator core offset its benefit (this was all addressing their use in
race cars).
The source indicated
that up to 30Deg the drag increases and heat transfer goes down due to uneven
air flow distribution and disturbances – apparently above that angle this
adverse effect decreases and of course you have the much larger frontal
area..
At least that is what I
recall. If anyone is interested I’ll see if I can find the article in my
files
Ed
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Al Gietzen
Sent: Friday, January 15, 2010 1:13
AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re:
Scoops
Thomas,
Nice research.
I
found my notes on inclined radiators, they state
1.
0-20/30* will decrease cooling and increase drag.
2.
Over 30* things improve.
3.
At approx 55* cooling effectiveness is 30% greater than non-inclined rads
and
drag is less by 20%.
George; do you have
the source for that info? It may be a good idea to verify this information.
I don’t recall the specifics; but what I do recall is that the conclusion
was configuration dependant, and should not be taken as generally
applicable. Sorry, but I don’t remember what the factors were; maybe
something about the configuration of the core.
Or maybe my memory
just isn’t right. Worth checking.
All
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