Surface radiators for water cooled engines

"Ron Natalie" wrote in message om...
"Jay" wrote in message om...

I'd put forth the idea that the worst
case environment for an aircraft is always better than the worst case
for an automobile. Does anyone disagree on this point?

Yeah, I do. Many cars typically don't operate at 80% of rated power for long
periods.

Depends on how you define "long period". For the puposes of this
discussion, any amount of time over the amount of time it takes to
heat the water volume and block I would call "long" Thats probably on
the order of a several minutes. Driving up a long grade on a hot day
(which is where I see all the blown radiators) seems like it would
meet the high output for "long" time case.

Therefor, a cooling surface directly exposed to the prop wash does not
have to be as large in area as that of the radiator orginally designed
for that automobile.

Cars have fans too.

I'm not sure its fair to compare a 10" 1/4 HP electric fan to a 150HP
propeller.

"Jay" wrote in message om...

I'm not sure its fair to compare a 10" 1/4 HP electric fan to a 150HP
propeller.

That 150HP propeller is developing some useful thrust as well. For efficiency
the last thing you want is a large amount of it impinging on some flat plate.
That 1/4HP fan is shrouded and delivers almost all of it's flow directly to the cooling fins
of the radiator.

Its true that the larger proportion of the air from the propeller
never goes onto the cowl, but it's still a lot.

A surface radiator isn't necessarily a flat plane, what shape is the
cowl on the airplane you fly? And the air stream is directed onto the
cowl at an angle as is necessary to flair around the engine/cowling.
The cowl would look similar to the current cowls except it would be
more stream lined and have no large holes to duct in air. And of
course in big red letters "HOT SURFACE- DO NOT TOUCH"

"Ron Natalie" wrote in message om...
"Jay" wrote in message om...

I'm not sure its fair to compare a 10" 1/4 HP electric fan to a 150HP
propeller.

That 150HP propeller is developing some useful thrust as well. For efficiency
the last thing you want is a large amount of it impinging on some flat plate.
That 1/4HP fan is shrouded and delivers almost all of it's flow directly to the cooling fins
of the radiator.

In article ,
(Jay) writes:


I'm not sure its fair to compare a 10" 1/4 HP electric fan to a 150HP
propeller.



Depends on how much of the output from each actually has contact with the
cooling surface. That 10" 1/4 hp fan is placed directly next to the radiator
and the output is forced through and past the cooling surfaces at a constant
and predictable velocity. The vast majority of the output from that 150 hp
propeller will not even be close to the cooling surface and its velocity will
varry considerably.

Bob Reed
www.kisbuild.r-a-reed-assoc.com (KIS Builders Site)
KIS Cruiser in progress...Slow but steady progress....

"Ladies and Gentlemen, take my advice,
pull down your pants and Slide on the Ice!"
(M.A.S.H. Sidney Freedman)