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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