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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