Ambitious undertaking
for certain, George.
I think the rule of
thumb you are looking for is 3 cubic inches of core volume for each HP.
So 180 HP rotary would require 180 * 3 = 540 cubic inches of core. My
two GM cores are 10x9 x 3.5 *2 = 630 cubic inches and they are designed for
Freon rather than water. So a “real” water radiator would undoubtedly do
better and 540 does not seem unreasonable.
Regarding the
incident angle, I would say it’s the angle relative to the incoming
airflow. So if you stood the core vertically, then 55 deg would be the
most you would want from the vertical – but, I must say that unless you are
also designing and understand the effects of “angle of attack” on the small
air channels and can shape them to give you the characteristic you want, I
would hesitate to vary much from 70 - 90 deg.
Some folks have
quoted studies where cooling improved by inclining the radiator, but when I
read the report, it was clear the reason the cooling improved is that with a
slanted radiator orientation – you could place a larger core which resulted in
better cooling until around 22 deg from vertical – after than it seems the air
had a harder timing making the turn to flow into the air channels and no
further improvement even with increased size was found. At least that was my
interpretation of the data.
This is an area I
admit to only a very limited understanding – and certainly not enough feel
comfortable designing a radiator – however, if you have an acquaintance who
has some experience in that field, go for it!!!!
Good
luck.
Ed
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of George Lendich
Sent: Tuesday, June 30, 2009 6:48
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Round
Radiators
Bernie's comments on weird have
prompted me to start my investigation on a round radiator, PWR locally has an
engineer who is interested in my ideas and we may move to develop a
prototype.
It seems the easiest way to
manufacture this type of radiator is along the lines of the stacker
radiator, used mostly for water to oil and are very efficient for this
purpose. I've seen where people are using them for radiators in racing. To
optimize the suitability for my application the air flow channels would be
modified for reasons of maximum surface area, turbulence
etc.
Naturally a round radiator need to
be thinner rather than thicker ( unlike the round intercoolers). In my design
the air flows from the centre outwardly and taken back toward a butterfly to
control the exit air flow.
The inlet would need to be
shaped to maximize pressure as would the internals. I can't easily
explain everything but I would appreciate some help with sizing fore hp etc. I
do have notes on the subject and will have to find them again but I think a
rule of thumb is either 3 sq" per hp or 3 cu" per hp and radiator incidence in
excess of 55 deg and if the angle is taken from the vertical or
horizontal.
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