Oil coolers

Mike, you live in a different universe than I, apparently... Most
everything you say here violates what I know to be engineering fact, and
thermodynamic necessity, after a lifetime of building up and burning down
engines...

Oil absorbs internal heating of engine parts from both combustion and
friction and transfers it to the external metal of the engine (primarily but
not limited to; oil pan, rocker covers the big two, crankcase, and
propellor hub, and a cooler if present) and that metal then transfers the
heat both convectively and conductively to the external world...
Up to 40% of waste heat is transferred out of the engine by the oil
according to this source http://www.uccc.co.uk/when/hycwoil.htm
- actually that looks a bit high and I tend to size my calculations on a 33%
basis...
See also
http://www.usace.army.mil/publicatio...-691/chap9.pdf

http://www.perma-cool.com/Catalog/Cat_page02.html

Engine cooling is a science, not guesswork, and there has been millions of
dollars spent on research since the invention of the internal combustion
engine as a prime mover... In ten minutes I could amass dozens more
authoritative references, but I suspect it will be wasted effort...
Have a good un...

Denny

"mikem" wrote in message

Doug wrote:
: paths for cooling and radiator). Also consider the FAA certification,
: the FAA may require the engine to run without the anti-freeze coolant
: (leaks out), but FAA doesn't require engine to run without oil. So oil

Actually, I believe that a certified aircraft engine has to run
for a certain period of time without oil, and still produce (albeit
decreasing) power.

-Cory

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Doug wrote:

[snip]

I don't know about aircraft engines but
motorcycle engines power to displacement went up dramatically when
they started doing water cooled (oil in Suzuki's case).

[snip]

Liquid cooled (be it water, antifreeze, oil or liquid sodium)
powerplants tend to produce more power per displacement than air cooled
(using the common semantics of "no working fluid to transport heat from
hot spots to something that will reject it") because it's far easier to
control temperatures and thus easier to maintain tighter tolerances.

One of my cars has a normally aspirated 3.4L "air cooled" engine that
generates a bit over 350HP at sea level. Some fairly exotic stuff was
used by the engine builder to try to match the expansion rates of studs,
heads, cylinders and cam towers, but ultimately it was necessary to give
up on head gaskets and run cylinder and head metal-to-metal. It suffers
from morning sickness when cold -- it runs on random combinations of
four, five and six cylinders until things expand into place. I wouldn't
have to deal with this if I could limit the range of operating
temperatures for the cylinders and heads, and could be more aggressive
with leaning the mixture and advancing the timing (which would result in
increased output).

To tie this into the more hair splitting part of this thread, this "air
cooled" engine is oil cooled in the sense that piston coolers help keep
crown temperatures manageable and much of the heat rejected by the
sodium filled exhaust valves and the heads is transported by the oil to
a pair of largish oil coolers that reject to the air. The cylinder
walls, however, have no direct cooling other than forced air. If I ever
get myself in gear and replace the existing heads with liquid cooled
ones I'll probably describe it as "an air cooled engine with liquid
cooled heads", since the only real heat rejection path for the cylinders
will continue to be direct contact with the air stream.


--
Chris Kennedy

http://www.mainecoon.com
PGP fingerprint: 4E99 10B6 7253 B048 6685 6CBC 55E1 20A3 108D AB97

wrote in message ...
Doug wrote:
: paths for cooling and radiator). Also consider the FAA certification,
: the FAA may require the engine to run without the anti-freeze coolant
: (leaks out), but FAA doesn't require engine to run without oil. So oil

Actually, I believe that a certified aircraft engine has to run
for a certain period of time without oil, and still produce (albeit
decreasing) power.

Nope. It has to run all the requirements on 1/2 oil capacity. There are no
"no oil" tests nor any "run to destruction" tests. About the closest thing
is that the engine should not catch fire, burst, or exceed the loads allowed
by the engine mounting in the event of such a situation. This is shown
by analysis rather than a specific test.

Ron Natalie wrote:
: Nope. It has to run all the requirements on 1/2 oil capacity. There are no
: "no oil" tests nor any "run to destruction" tests. About the closest thing
: is that the engine should not catch fire, burst, or exceed the loads allowed
: by the engine mounting in the event of such a situation. This is shown
: by analysis rather than a specific test.

I stand corrected then. Just for grins, ever seen a document
describing this certification procedure? Also, is that 1/2 oil
requirement the reason for the ludicrous (and very messy) maximum oil
capacity of 8 quarts for a 4-banger and 12 for a 6? IIRC, the POH says,
that any level at or above 2 quarts is "acceptable," although certainly
not by me.

-Cory


--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************