Re: Surface radiators for water cooled engines

[Harry Burns]

Intercoolers of the same config. were used on early model P-38's. They ducted
pressurized air along the insides of the leading edges, then into the carb.
They all had problems with cooling efficency and leaks.

Several famous Thompson Trophy (sea/float planes) winners used surface
radiators to some degree. Most notably the Supermarines. Don't know what kind
of problems they had, but its worth a look, and a grain of salt.

Harry

[Jay]

I'm not sure who was saying that it had been tried and it didn't work
as several people of given examples of successful racing aircraft
using surface radiators.

> Several famous Thompson Trophy (sea/float planes) winners used surface
> radiators to some degree. Most notably the Supermarines. Don't know what kind
> of problems they had, but its worth a look, and a grain of salt.

The guy that was saying an airplane waiting in line is the same as a
car idling in traffic is off base because even with zero airspeed that
prop is blowing turbulent air across the cowl.

The wing radiators aren't going to be as efficient per unit area as
the cowl or other parts of the aircraft in turbulent flow.

I was under the impression that Voyager used fuel efficient versions
of the traditional aircooled engines commonly used today, so I'd like
to hear more about the pickup truck stories.

And just because something has been tried before and failed, doesn't
mean the concept should be abandoned. Haven't you ever seen anyone
flub an attempt or do an experiment with an agenda? Why should their
oversight stop others from doing better. And those old times were
lacking many of the tools available today, mainly the cheap
availability of computing power. You have part time hacks doing
analysis orders of magnitude more accurate than they were doing back
the 20-30's.

[Barnyard BOb --]

(Jay) wrote:

>
>And just because something has been tried before and failed, doesn't
>mean the concept should be abandoned. Haven't you ever seen anyone
>flub an attempt or do an experiment with an agenda? Why should their
>oversight stop others from doing better. And those old times were
>lacking many of the tools available today, mainly the cheap
>availability of computing power. You have part time hacks doing
>analysis orders of magnitude more accurate than they were doing back
>the 20-30's.
++++++++++++++++++++++++++++++++++

Yeah, yeah, yeah.
Commentary like yours won't buy a cup of coffee.

If you're so smart, lead the way or be pegged as....
a typical newbie making silly little motor boat noises
in a very large sea of knowledge.


Barnyard BOb - 50 years of flight

[Model Flyer]

"Barnyard BOb --" > wrote in message
...
>
> (Jay) wrote:
> >analysis orders of magnitude more accurate than they were doing
back
> >the 20-30's.
> ++++++++++++++++++++++++++++++++++
>
> Yeah, yeah, yeah.
> Commentary like yours won't buy a cup of coffee.
>
> If you're so smart, lead the way or be pegged as....
> a typical newbie making silly little motor boat noises
> in a very large sea of knowledge.
>

Priceless putdown.
Lol
--

..
--
Cheers,
Jonathan Lowe
modelflyer at antispam dot net

Antispam trap in place


>
> Barnyard BOb - 50 years of flight
>
>
>
>

[Russell Kent]

Jay wrote:

> I was under the impression that Voyager used fuel efficient versions
> of the traditional aircooled engines commonly used today, so I'd like
> to hear more about the pickup truck stories.

Do your homework. 60 seconds of Google and you would have learned that Voyager used
a pair of Teledyne Continental IOL-200 engines. In case you don't know it, that "L"
in the engine type means "liquid cooled".

Russell Kent

[Barnyard BOb --]

Russell Kent wrote:

>Jay wrote:
>
>> I was under the impression that Voyager used fuel efficient versions
>> of the traditional aircooled engines commonly used today, so I'd like
>> to hear more about the pickup truck stories.
>
>Do your homework. 60 seconds of Google and you would have learned that Voyager used
>a pair of Teledyne Continental IOL-200 engines. In case you don't know it, that "L"
>in the engine type means "liquid cooled".
>
>Russell Kent
++++++++++++++++++++++++

Tsk, tsk....

Teledyne Continental 0-240 piston engine (forward)

http://www.nasm.si.edu/galleries/gal108/gal108.html
http://www.aerospaceweb.org/aircraft/research/voyager/
http://www.va-works.com/projects/voyager.html


Barnyard BOb --

[Russell Kent]

Barnyard BOb -- wrote:

> Russell Kent wrote:
>
> >Jay wrote:
> >
> >> I was under the impression that Voyager used fuel efficient versions
> >> of the traditional aircooled engines commonly used today, so I'd like
> >> to hear more about the pickup truck stories.
> >
> >Do your homework. 60 seconds of Google and you would have learned that Voyager used
> >a pair of Teledyne Continental IOL-200 engines. In case you don't know it, that "L"
> >in the engine type means "liquid cooled".
> >
> >Russell Kent
> ++++++++++++++++++++++++
>
> Tsk, tsk....
>
> Teledyne Continental 0-240 piston engine (forward)
>
> http://www.nasm.si.edu/galleries/gal108/gal108.html
> http://www.aerospaceweb.org/aircraft/research/voyager/
> http://www.va-works.com/projects/voyager.html
>

Arrggg.. Hoisted by my own petard. In my rush to prove how quickly the information was
available ("60 seconds of Google") I failed to read the article for content.

http://www.nasm.si.edu/nasm/aero/aircraft/rutanvoy.htm

I'll take my crow grilled with a little bit of Mesquite spices please.

Russell Kent

[RobertR237]

In article >, Russell Kent > writes:

>
>Arrggg.. Hoisted by my own petard. In my rush to prove how quickly the
>information was
>available ("60 seconds of Google") I failed to read the article for content.
>
>http://www.nasm.si.edu/nasm/aero/aircraft/rutanvoy.htm
>
>I'll take my crow grilled with a little bit of Mesquite spices please.
>
>Russell Kent
>
>

Russell, you are a class act.


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)

[Wooduuuward]

There is an engine in the U.S. patent offices (so nobody can use it)
developed by 'Smokey' who wrote a self help column in Popular
Science magazine for years, that doesn't use a radiator. It takes the
heat from the engine and uses it to preheat the fuel to pre detonation
temperature and thus allows 55% of fuel energy to be used rather
than the 12% now used in conventional engines.
You should look into this. I became aware of it a few months ago.
It can be found in the 1980 or 1984 issues.


Jay wrote:
>
> I'd like to see some discussion on surface radiators instead of how to
> build plenums directing air through auto radiators. Seems like you
> could braze aluminum tubing onto the inner surface of the lower cowl,
> add a sheet of insulation on top of that on the inside and you'd have
> a particularly low drag radiator. The cowling is going to get blasted
> with turbulant air anyway, might as well heat that air up a little as
> it swirls by the surface.
>
> The holes in the front of the cowling make some sense for an air
> cooled engine where the temperature differential is high and you can
> direct some air (with lots of drag) directly onto the heads. But if
> you have a water cooled engine, you can do things differently and it
> would seem with lower drag. Drag is the primary predictor of top
> speed, beyond horsepower even.

[Barnyard BOb --]

Wooduuuward praised:

>There is an engine in the U.S. patent offices (so nobody can use it)
>developed by 'Smokey' who wrote a self help column in Popular
>Science magazine for years, that doesn't use a radiator. It takes the
>heat from the engine and uses it to preheat the fuel to pre detonation
>temperature and thus allows 55% of fuel energy to be used rather
>than the 12% now used in conventional engines.
>You should look into this. I became aware of it a few months ago.
>It can be found in the 1980 or 1984 issues.
++++++++++++++++++++++++++++++++++++++++++++++

The fellow of which you speak is Henry "Smokey" Yunick.
He was my hero back in the 50's, when I was the average
impressionable teeny bopper subject to spouting stuff like you.

FWIW....
Imply what you will, but there is NOTHING to look into
application-wise, where surface radiators are concerned or
anything else that a backyard builder can readily put to use.
http://www.bankspower.com/tech_coolair.cfm


Barnyard BOb -- 50 years of flight

[Wooduuuward]

Thanks Boob,
nice of you to be so polite.
What I've spoken of is fact, if you would like to check it
out you will find the U.S. Military has the technology currently.
Fact: Henry "Smokey" Yunick was alive and kicking in the 1980's
and the three big auto makers offered him $200 g's for the rights
to it. Fact.
As for the backyard mechanic, that's exactly what Smokey was,
and well paid for it.


Barnyard BOb -- mumbled:
>
> The fellow of which you speak is Henry "Smokey" Yunick.
> He was my hero back in the 50's, when I was the average
> impressionable teeny bopper subject to spouting stuff like you.
>
> FWIW....
> Imply what you will, but there is NOTHING to look into
> application-wise, where surface radiators are concerned or
> anything else that a backyard builder can readily put to use.
> http://www.bankspower.com/tech_coolair.cfm
>
> Barnyard BOb -- 50 years of flight


>
> Wooduuuward commented:
>
> >There is an engine in the U.S. patent offices (so nobody can use it)
> >developed by 'Smokey' who wrote a self help column in Popular
> >Science magazine for years, that doesn't use a radiator. It takes the
> >heat from the engine and uses it to preheat the fuel to pre detonation
> >temperature and thus allows 55% of fuel energy to be used rather
> >than the 12% now used in conventional engines.
> >You should look into this. I became aware of it a few months ago.
> >It can be found in the 1980 or 1984 issues.
> ++++++++++++++++++++++++++++++++++++++++++++++

[Wooduuuward]

Henry "Smokey" Yunick already did.

Corky Scott wrote:>
> I don't think anyone has any experience actually building the type of
> cooling system you suggest. I further postulate that the reason is
> because it doesn't work very well, is extremely difficult to fabricate
> and co$t$ too much for the supposed (and as yet undetermined)
> benefits.
>
> But if you feel you can build this type of system, perhaps you should.
> Then you can tell the world about your success.
>
> Corky Scott

[Corky Scott]

On Wed, 02 Jul 2003 10:07:12 -0400, Wooduuuward >
wrote:

>Henry "Smokey" Yunick already did.
>
>Corky Scott wrote:>
>> I don't think anyone has any experience actually building the type of
>> cooling system you suggest. I further postulate that the reason is
>> because it doesn't work very well, is extremely difficult to fabricate
>> and co$t$ too much for the supposed (and as yet undetermined)
>> benefits.
>>
>> But if you feel you can build this type of system, perhaps you should.
>> Then you can tell the world about your success.
>>
>> Corky Scott

Right, Smokey was nearly a God. He could pull more power out of an
engine than just about anyone else who called him a peer.

But for some reason, this cooling system he invented/fabricated did
not become widely known. Wonder why not? Could it be that it was too
expensive, too hard to fabricate and too vulnerable?

Corky Scott

[Barnyard BOb --]

Wooduuuward driveled:

>Thanks Boob,
>nice of you to be so polite.
>What I've spoken of is fact, if you would like to check it
>out you will find the U.S. Military has the technology currently.
>Fact: Henry "Smokey" Yunick was alive and kicking in the 1980's
>and the three big auto makers offered him $200 g's for the rights
>to it. Fact.
>As for the backyard mechanic, that's exactly what Smokey was,
>and well paid for it.
+++++++++++++++++++++++++++++++++++++

Here's a fact for ya, dipstick....
You're the ****ing boob and a very gullible one at that.

This is a PATENTED invention, right?
Nobody can LEGALLY build this engine without paying...
assuming one even had the talent and money to do so.

Assuming the 'military' does have this technology,
it must be not be too damn hot if they have not made
use of it in the last 20 years.

You're continuing to waste everyone's time with your
impractical nonsense and visions of grandeur, bonehead.


Barnyard BOb -- resident curmudgeon

[Orval Fairbairn]

In article >,
(Corky Scott) wrote:

> On Wed, 02 Jul 2003 10:07:12 -0400, Wooduuuward >
> wrote:
>
> >Henry "Smokey" Yunick already did.
> >
> >Corky Scott wrote:>
> >> I don't think anyone has any experience actually building the type of
> >> cooling system you suggest. I further postulate that the reason is
> >> because it doesn't work very well, is extremely difficult to fabricate
> >> and co$t$ too much for the supposed (and as yet undetermined)
> >> benefits.
> >>
> >> But if you feel you can build this type of system, perhaps you should.
> >> Then you can tell the world about your success.
> >>
> >> Corky Scott
>
> Right, Smokey was nearly a God. He could pull more power out of an
> engine than just about anyone else who called him a peer.
>
> But for some reason, this cooling system he invented/fabricated did
> not become widely known. Wonder why not? Could it be that it was too
> expensive, too hard to fabricate and too vulnerable?
>
> Corky Scott

I believe that the thermodynamics involved don't fit the problem.
Evaproating the fuel as it goes into the engin won't provide sufficient
cooling to do the job.

Regarding surface radiators, they are too prone to crack development,
being exposed to constant vibration and airframe flexing to be practical.

The Scneider Cup racers of the 20s/30s flew only a few hours total, so
there was no long-term exposure to these conditions. I would certainly
hate to have one start spewing coolant over the middle of Alligator
Swamp.

--
To get random signatures put text files into a folder called ³Random Signatures² into your Preferences folder.

[Wooduuuward]

the adiabatic engine in Popular Science, used almost no water to cool the
engine because it was designed to run red hot. It was designed and tested in small
car by Smokey.

Corky Scott wrote:
>
> On Wed, 02 Jul 2003 10:07:12 -0400, Wooduuuward >
> wrote:
>
> >Henry "Smokey" Yunick already did.
> >
> >Corky Scott wrote:>
> >> I don't think anyone has any experience actually building the type of
> >> cooling system you suggest. I further postulate that the reason is
> >> because it doesn't work very well, is extremely difficult to fabricate
> >> and co$t$ too much for the supposed (and as yet undetermined)
> >> benefits.
> >>
> >> But if you feel you can build this type of system, perhaps you should.
> >> Then you can tell the world about your success.
> >>
> >> Corky Scott
>
> Right, Smokey was nearly a God. He could pull more power out of an
> engine than just about anyone else who called him a peer.
>
> But for some reason, this cooling system he invented/fabricated did
> not become widely known. Wonder why not? Could it be that it was too
> expensive, too hard to fabricate and too vulnerable?
>
> Corky Scott

[Russell Kent]

Ernest Christley wrote:

> The military is exempt from patent restrictions,

I doubt that statement is true, but I have no facts to either prove or
disprove the statement. In any case, the U.S. military does not (as a rule)
manufacture much of its own equipment. That is done by subcontractors who
are very much bound by U.S. patent law.

Russell Kent

[Wooduuuward]

Thanks Barnyard, we all appreciate your comments.

Barnyard BOb -- wrote:
>
> Wooduuuward driveled:
>
> >Thanks Boob,
> >nice of you to be so polite.
> >What I've spoken of is fact, if you would like to check it
> >out you will find the U.S. Military has the technology currently.
> >Fact: Henry "Smokey" Yunick was alive and kicking in the 1980's
> >and the three big auto makers offered him $200 g's for the rights
> >to it. Fact.
> >As for the backyard mechanic, that's exactly what Smokey was,
> >and well paid for it.
> +++++++++++++++++++++++++++++++++++++
>
> Here's a fact for ya, dipstick....
> You're the ****ing boob and a very gullible one at that.
>
> This is a PATENTED invention, right?
> Nobody can LEGALLY build this engine without paying...
> assuming one even had the talent and money to do so.
>
> Assuming the 'military' does have this technology,
> it must be not be too damn hot if they have not made
> use of it in the last 20 years.
>
> You're continuing to waste everyone's time with your
> impractical nonsense and visions of grandeur, bonehead.
>
> Barnyard BOb -- resident curmudgeon

[Michael McNulty]

"Russell Kent" > wrote in message
...
> Ernest Christley wrote:
>
> > The military is exempt from patent restrictions,
>
> I doubt that statement is true, but I have no facts to either prove or
> disprove the statement. In any case, the U.S. military does not (as a
rule)
> manufacture much of its own equipment. That is done by subcontractors who
> are very much bound by U.S. patent law.
>
> Russell Kent
>
Actually, the normal U.S. military development contract has a clause called
"authorization and consent" that specifically authorizes the contractor to
infringe on any patents that it sees fit too, and whereby the U.S.
government consents to accept any liability associated with this
infringement (i.e. they agree to allow themselves to be sued by the patent
holder).

Believe it or not.

[RobertR237]

In article >, Barnyard BOb --
> writes:

>
>The fellow of which you speak is Henry "Smokey" Yunick.
>He was my hero back in the 50's, when I was the average
>impressionable teeny bopper subject to spouting stuff like you.
>
>

Oh my God! Here I thought that the only hero you ever had was that old coot
that stares back at you from the mirror every morning. <BFG>


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)

[RobertR237]

In article >, Wooduuuward >
writes:

>
>Thanks Boob,
>nice of you to be so polite.
>What I've spoken of is fact, if you would like to check it
>out you will find the U.S. Military has the technology currently.
>Fact: Henry "Smokey" Yunick was alive and kicking in the 1980's
>and the three big auto makers offered him $200 g's for the rights
>to it. Fact.
>As for the backyard mechanic, that's exactly what Smokey was,
>and well paid for it.
>
>

You mean the three big auto makers tried to SCREW him out of it for $200 g's
knowing full well that if it worked it would be worth ten thousand times that.



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)

[Bob]

AND, patents are issued by the US Government AND they retain certain
rights in return for the protection they afford.

Just like trying to sue the Government, it's their party.



"Michael McNulty" > wrote in message >...
> "Russell Kent" > wrote in message
> ...
> > Ernest Christley wrote:
> >
> > > The military is exempt from patent restrictions,
> >
> > I doubt that statement is true, but I have no facts to either prove or
> > disprove the statement. In any case, the U.S. military does not (as a
> rule)
> > manufacture much of its own equipment. That is done by subcontractors who
> > are very much bound by U.S. patent law.
> >
> > Russell Kent
> >
> Actually, the normal U.S. military development contract has a clause called
> "authorization and consent" that specifically authorizes the contractor to
> infringe on any patents that it sees fit too, and whereby the U.S.
> government consents to accept any liability associated with this
> infringement (i.e. they agree to allow themselves to be sued by the patent
> holder).
>
> Believe it or not.

[Wooduuuward]

Did you have a look at Smokey's drawings and facts on his working
engine in a car, before you posted this?

Richard Isakson wrote:
>
> "Orval Fairbairn" wrote ...
> > I believe that the thermodynamics involved don't fit the problem.
> > Evaproating the fuel as it goes into the engin won't provide sufficient
> > cooling to do the job.
>
> Snicker. You got that right! Gasoline has a specifc heat of 0.50
> BTU/lb/deg F and a vaporization point of about 350 deg F. Heating the gas
> from 70 deg to 350 deg could absorb 140 BTU/lb from the exhaust out of a
> total of 18,000 BTU/lb that will be burned.
>
> Darn it, I missed another free lunch.
>
> Rich

[Paul Millner]

>> Gasoline has a specifc heat of 0.50
BTU/lb/deg F and a vaporization point of about 350 deg F

Gasoline's endpoint is 350 F... half of it is vaporized by about 180F... and
it starts vaporizing just under 100F... remember, it's a mixture of
hydrocarbons. Of course, you get more bang for the buck than just the
specific heat... you get the heat of vaporization as well, eh?

Paul

[Jay]

Sorry it took so long to get back but I'm in Hawaii right now so
access to the internet is limited (laptop+digital cell phone).

The vast majority of GA engines don't use radiators so none of the
large manufacturers are interested in pursuing a project with only a
niche market (and budget concious one at that), so this may be another
reason.

And you bring up a good point, who can build one and the rest of an
entire airplane. Most people are so busy doing all the other things
the have to do (work) to be able to spend time/money doing experiments
but thats part of the reason for bring it up here- so we can get lots
of eyes and brains on the problem. Some people that have done work in
this area can bring up points, and maybe somebody will say "I work in
a brazing shop, we make something like that for XYZ application."
I've seen some stuff real close done by the guys that do forced air
cooled cabnets for avionics. No doubt, construction will have to be
done by a specialist or someone that will become a specialist. I'm
writing in this newgroup more for the expermintal part and less for
the home made part.

Mechanical stresses- I can definitly see this would be a problem if
the radiator is a structural element or ridgedly attached to one at
multiple points, but what I'd imagined was some part (or whole) of the
lower cowl. That cowl region being critical because it has access to
that nice cooling turbulent air right behind the propeller. 3 blades
might do better than 2 for this style cooling. The only weight it has
to support is itself. These things are often times fiberglass so they
aren't all that strong.

From what I've read of the radiator imperical studies from the "golden
age", producing a turbulent flow was key cooling efficiency per unit
area.

For a low speed aircraft (<100MPH) an auto radiator makes more sense
than something custom like we're talking about here.


Regards

[RobertR237]

In article >,
(Jay) writes:

>
>Mechanical stresses- I can definitly see this would be a problem if
>the radiator is a structural element or ridgedly attached to one at
>multiple points, but what I'd imagined was some part (or whole) of the
>lower cowl. That cowl region being critical because it has access to
>that nice cooling turbulent air right behind the propeller. 3 blades
>might do better than 2 for this style cooling. The only weight it has
>to support is itself. These things are often times fiberglass so they
>aren't all that strong.
>

Surface Area? A standard auto styled radiator has a tremendous serface area
packed into a very small and light package. The air is forced through that
surface area with contact normally on two surfaces as it passes. To obtain the
same surface area on a single sided flat plain would take much more area than
is available on the underside of the cowling. You might be able to get enough
area by using the whole underside of the fuselage but you still don't have the
same type of contact.

>From what I've read of the radiator imperical studies from the "golden
>age", producing a turbulent flow was key cooling efficiency per unit
>area.
>
>For a low speed aircraft (<100MPH) an auto radiator makes more sense
>than something custom like we're talking about here.
>
>
>Regards
>
>


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)

[Barnyard BOb --]

>
>Surface Area? A standard auto styled radiator has a tremendous serface area
>packed into a very small and light package. The air is forced through that
>surface area with contact normally on two surfaces as it passes. To obtain the
>same surface area on a single sided flat plain would take much more area than
>is available on the underside of the cowling. You might be able to get enough
>area by using the whole underside of the fuselage but you still don't have the
>same type of contact.
>
>Bob Reed
+++++++++++++++++++++++++++++++++++++++

Bravo Bob, but no matter how you say it...
there are dreamers and wannabees that just can't let go
no matter what. Evidently, living without the Easter Bunny,
Santa Claus and the Surface Radiator Fairy is unthinkable.

Barnyard BOb -- stranger than fiction

[Jay]

Bob had mentioned the surface area thing as well, and this is a linear
relationship, but what I'm refering to is turbulence which has an
exponential relationship to the effective heat transfer capability of
that air mass. As you may know, in clean air, a film of heated air
clings to the interface between the metal surface and the air mass as
it passes by, this impedes heat transfer. A car radiator, while being
small and available, is also exceedingly draggy, which is why its not
an optimal choice choice for a fast airplane. The auto radiator is
designed for different conditions mainly:
1) High disipation at low air flow speeds
2) Clean air entering front surface (Reynolds number less than 10,000)
2) Drag not an issue

An aircraft/cowl-surface scenario doesn't have the condition of high
power output and low airflow and thustly should not besigned for this
condition. Even on the climb out, while the IAS may be low, the prop
wash is turbulent and higher in velocity than the speed of the vehicle
itself.

Regards

[RobertR237]

In article >, Barnyard BOb --
> writes:

>
>>
>>Surface Area? A standard auto styled radiator has a tremendous serface area
>>packed into a very small and light package. The air is forced through that
>>surface area with contact normally on two surfaces as it passes. To obtain
>the
>>same surface area on a single sided flat plain would take much more area
>than
>>is available on the underside of the cowling. You might be able to get
>enough
>>area by using the whole underside of the fuselage but you still don't have
>the
>>same type of contact.
>>
>>Bob Reed
>+++++++++++++++++++++++++++++++++++++++
>
>Bravo Bob, but no matter how you say it...
>there are dreamers and wannabees that just can't let go
>no matter what. Evidently, living without the Easter Bunny,
>Santa Claus and the Surface Radiator Fairy is unthinkable.
>
>Barnyard BOb -- stranger than fiction
>

I understand the dreamers and wannabees but don't understand wanting to
reinvent the wheel. The idea of surface cooling is not a bad idea until you
get to looking at the details of what has already been tried and why is was not
a success. Many of the current advances in all areas is being achieved by
using old ideas with some of the modern materials and methods. If there was
some new materials available which could make this a plausable concept then
more power to them, it might work.


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)

[Barnyard BOb --]

>>The auto radiator is
>>designed for different conditions mainly:
>>1) High disipation at low air flow speeds
>>2) Clean air entering front surface (Reynolds number less than 10,000)
>>2) Drag not an issue
>>
>>An aircraft/cowl-surface scenario doesn't have the condition of high
>>power output and low airflow and thustly should not besigned for this
>>condition. Even on the climb out, while the IAS may be low, the prop
>>wash is turbulent and higher in velocity than the speed of the vehicle
>>itself.
>>
>>Regards
>>
>>
>
>Well, since you already have it all figured out and know all the answers what
>are you waiting for, do it. We are obviously unknowing of the solutions which
>you have worked out and are waiting to be proved wrong.
>
>Bob Reed
+++++++++++++++++++++++++++++++++++++++++++

This is the same class of dreamer and wannabee that
was discussed earlier. This ilk will not only reinvent the
wheel with Unobtainium, but is also famous for wasting
perfectly good restaurant paper napkins at lunch time.


Barnyard BOb -- Have sharp stick. Will travel.

[Corky Scott]

On 7 Jul 2003 12:43:45 -0700, (Jay) wrote:

A car radiator, while being
>small and available, is also exceedingly draggy, which is why its not
>an optimal choice choice for a fast airplane. The auto radiator is
>designed for different conditions mainly:
>1) High disipation at low air flow speeds
>2) Clean air entering front surface (Reynolds number less than 10,000)
>2) Drag not an issue
>
>An aircraft/cowl-surface scenario doesn't have the condition of high
>power output and low airflow and thustly should not besigned for this
>condition. Even on the climb out, while the IAS may be low, the prop
>wash is turbulent and higher in velocity than the speed of the vehicle
>itself.
>
>Regards

Right, auto radiators don't work that well in airplanes for a number
of reasons. That's why you don't see many of them in airplanes. But
if you have the room to install them and can slow the air that passes
through them enough, they do work.

A lot of people who need a liquid heat exchanger go to the companies
that build them for the racing scene, or use something more compact,
like an air conditioning evaporator core. Those aren't optimal either
because they tend to have a dense fin spacing which makes passing the
air through them problematic.

But there are several firms in the US that build heat exchangers
designed for the speeds airplanes encounter and can be custom built to
your specifications. This pretty much solves the problem. If you do
your homework correctly and give them the proper specifications, and
plan your ducting properly, your engine will cool properly.

Corky Scott

[Ed Sullivan]

Barnyard BOb -- > wrote in message >...
> >>The auto radiator is
> >>designed for different conditions mainly:
> >>1) High disipation at low air flow speeds
> >>2) Clean air entering front surface (Reynolds number less than 10,000)
> >>2) Drag not an issue
> >>
> >>An aircraft/cowl-surface scenario doesn't have the condition of high
> >>power output and low airflow and thustly should not besigned for this
> >>condition. Even on the climb out, while the IAS may be low, the prop
> >>wash is turbulent and higher in velocity than the speed of the vehicle
> >>itself.
> >>
> >>Regards
> >>
> >>
> >
> >Well, since you already have it all figured out and know all the answers what
> >are you waiting for, do it. We are obviously unknowing of the solutions which
> >you have worked out and are waiting to be proved wrong.
> >
> >Bob Reed
> +++++++++++++++++++++++++++++++++++++++++++
>
> This is the same class of dreamer and wannabee that
> was discussed earlier. This ilk will not only reinvent the
> wheel with Unobtainium, but is also famous for wasting
> perfectly good restaurant paper napkins at lunch time.
>
>
> Barnyard BOb -- Have sharp stick. Will travel.


Watch it there Barnyard, Half the parts on my airplane originated on a paper napkin

Ed Sullivan - the original curmudgeon if you will recall

[Bob Kuykendall]

Earlier, (Jay) wrote:

> ...and thustly should not besigned for this...

Oh, gosh, can I quote you on that?

;}

Bob K.

[Morgans]

"Barnyard BOb --" > wrote in message

>
> Barnyard BOb -- Have sharp stick. Will travel.

Be careful not to poke your eye out! <g>
--
Jim in NC

[Jay]

Sure, be my guest.

(Bob Kuykendall) wrote in message >...
> Earlier, (Jay) wrote:
>
> > ...and thustly should not besigned for this...
>
> Oh, gosh, can I quote you on that?
>
> ;}
>
> Bob K.

[Ron Natalie]

"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.

> 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.

[Dillon Pyron]

On Tue, 08 Jul 2003 13:12:05 -0500, Big John >
wrote:

>Ralph
>
>Please. Smokey may have been 'creative' in his race cars but he didn't
>hold a candle to our A.J. (pride of Houston).

Smokey couldn't rassle like AJ, that's for sure. And cuss, the man
can cuss a blue streak without breaking a sweat. Watch a race, he's
never featured on the pit-to-car radio chatter. For a f*cking good
reason :-)

>
>
>Big John
>Pilot, ROC Air Force
>
>
>On 7 Jul 2003 18:25:41 -0700, (Ralph DuBose) wrote:
>
>----clip----
>
>> By the way, Mr. Yunick was famous for creative cheating in race
>>car construction.
>
>----clip----

--
dillon

The pen may be mightier than the sword,
but a .sig never beat a SIG

[Big John]

Dillon

Heard that until he got caught, he put NOX (is that right) inside the
tubing of his race car frame. On last lap he vented it to the carb and
blew everyone away. That's thinking out of the box <G>

Big John
Point of the sword



On Wed, 09 Jul 2003 19:50:20 GMT, Dillon Pyron >
wrote:

>On Tue, 08 Jul 2003 13:12:05 -0500, Big John >
>wrote:
>
>>Ralph
>>
>>Please. Smokey may have been 'creative' in his race cars but he didn't
>>hold a candle to our A.J. (pride of Houston).
>
>Smokey couldn't rassle like AJ, that's for sure. And cuss, the man
>can cuss a blue streak without breaking a sweat. Watch a race, he's
>never featured on the pit-to-car radio chatter. For a f*cking good
>reason :-)
>
>>
>>
>>Big John
>>Pilot, ROC Air Force
>>
>>
>>On 7 Jul 2003 18:25:41 -0700, (Ralph DuBose) wrote:
>>
>>----clip----
>>
>>> By the way, Mr. Yunick was famous for creative cheating in race
>>>car construction.
>>
>>----clip----

[Jay]

"Ron Natalie" > wrote in message >...
> "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.

[Barnyard BOb --]

>>> 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.
>
>Worst case environment for an automobile is sitting in stop and go traffic
>on hot sunny day for long periods of time.

Nope.
Popular misconception at best.

> Most cars have absolutely no
>trouble staying cool while screaming down the highway at full throttle.

Wrong again....
Most cars screaming down the highway get tickets or crash
long before they sustain 80% for long periods. Lots of variables,
but... speeds at 80% power could readily be exceeding 100 mph.


Barnyard BOb --

[Morgans]

"Barnyard BOb --" > wrote in message
...
>
> >>> 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.
> >
> >Worst case environment for an automobile is sitting in stop and go
traffic
> >on hot sunny day for long periods of time.
>
> Nope.
> Popular misconception at best.
>
> > Most cars have absolutely no
> >trouble staying cool while screaming down the highway at full throttle.
>
> Wrong again....
> Most cars screaming down the highway get tickets or crash
> long before they sustain 80% for long periods. Lots of variables,
> but... speeds at 80% power could readily be exceeding 100 mph.
>
>
> Barnyard BOb --
>

Right. The worst possible overheating, IMHO, is with a vehicle with an
automatic transmission, pulling a trailer up a grade that requires the
driver to keep WOT for an extended period of time. Add to that, a hot summer
day, running the AC.


You have engine load, additional transmission waste heat, lower road speed,
hot air, and even warmer air going across the radiator because of the AC
unit. Most any vehicle will overheat after an extended time, without
additional cooling, such as a transmission cooler.
--
Jim in NC

[Ron Natalie]

"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.

[RobertR237]

>> Wrong again....
>> Most cars screaming down the highway get tickets or crash
>> long before they sustain 80% for long periods. Lots of variables,
>> but... speeds at 80% power could readily be exceeding 100 mph.
>>
>>
>> Barnyard BOb --
>>
>

Yeah, my car screams down the road at 70+ with the engine turning a whole 2800
rpm. Hardly more than about 40% power in most cases.


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)

[RobertR237]

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)

[Jay]

Barnyard BOb -- > wrote in message
> > Most cars have absolutely no
> >trouble staying cool while screaming down the highway at full throttle.
>
> Wrong again....
> Most cars screaming down the highway get tickets or crash
> long before they sustain 80% for long periods. Lots of variables,
> but... speeds at 80% power could readily be exceeding 100 mph.
>
>
> Barnyard BOb --

Driving up a long grade in an automobile or a climb out after takeoff
in an aircraft are doing pretty much the same work with the same range
engine. Difference is the airspeed past the cowl/hood is WAY higher
and more turbulent in the aircraft.

But I'd have to agree with you BOb that 80% rated power in a car is
easily over 100MPH on level ground in many of the sportier cars.

No doubt an aircraft engine lives more of its life at higher power
levels. But this is more a case of reliability, not cooling system
sizing as the worst case cooling scenario is worse in the car
environment.

[Barnyard BOb --]

(Jay) wrote:

>> > Most cars have absolutely no
>> >trouble staying cool while screaming down the highway at full throttle.
>>
>> Wrong again....
>> Most cars screaming down the highway get tickets or crash
>> long before they sustain 80% for long periods. Lots of variables,
>> but... speeds at 80% power could readily be exceeding 100 mph.
>>
>>
>> Barnyard BOb --
>
>Driving up a long grade in an automobile or a climb out after takeoff
>in an aircraft are doing pretty much the same work with the same range
>engine. Difference is the airspeed past the cowl/hood is WAY higher
>and more turbulent in the aircraft.
>
>But I'd have to agree with you BOb that 80% rated power in a car is
>easily over 100MPH on level ground in many of the sportier cars.
>
>No doubt an aircraft engine lives more of its life at higher power
>levels. But this is more a case of reliability, not cooling system
>sizing as the worst case cooling scenario is worse in the car
>environment.
++++++++++++++++++++++++++++++++++

All this talk is going nowhere.... fast.
Are you going to fish or just keep cutting bait?


Barnyard BOb --

[Jay]

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 >...
> "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.

[Jay]

You're going to have drag anyway as the air goes around the cowl,
might as well use it to do something useful. So in this case, the
cooling causes no ADDITIONAL drag, right?

I'm NOT saying to use a blow through radiator like a car has, these
are only efficient (defined as heat transfer per unit drag) at low air
speeds. At the airspeeds a couple feet behind the propeller on climb
out, most of those fins are down at ambient, transfering no heat,
doing nothin' but causing drag.

I'm thinking that the bottom surface of the cowl area would be an idea
location:
1) Its out of the way during normal engine service.
2) Doesn't complicate removal of the top of the cowl
3) Periods of high load tend to be coincident with periods of high
AOA, so this puts more air over the surface when you need it.
4) Looks like a lot of common cowls have a relatively flat spot down
there maybe 2'x2'.

You might argue that the heat transfer for that area isn't sufficient,
and I think the analysis needs to be done, but not by a direct
comparison of area from an automobile finned type radiator. The
conditions are just too different to make that meaningful. A bottom
up calculation that includes heat transfer effects of turbulent air,
heat transfer properties of materials (likely Aluminum), waste heat
from engine, etc.


Regards

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

> Every amount of air that you want to use to cool is effectively drag.
> Are you claiming your design is going to work without changing the
> shape of the cowling? I don't think you're going to get anywhere near
> the heat transfer you need. You were talking about car radiators.
> I can tell you that plastering a car radiator horizontal on top of the
> cowl is not going to cool very well.

[Ernest Christley]

Jay wrote:

> You might argue that the heat transfer for that area isn't sufficient,
> and I think the analysis needs to be done, but not by a direct
> comparison of area from an automobile finned type radiator. The
> conditions are just too different to make that meaningful. A bottom
> up calculation that includes heat transfer effects of turbulent air,
> heat transfer properties of materials (likely Aluminum), waste heat
> from engine, etc.

So do it. Take a couple of 2'x2' sheat of .035 aluminum and a few
strips of 3/8" flat aluminum. Lay the flat strips on one piece of sheet
so that it forms sides and an interior maze that the water will have
to flow through. Drill, caulk and rivet it together. Add a spout for
the water to go in and come out with temp probes at each one. Add a
couple of T joints to the plumbing of your wife's car (don't let her
catch you at it) and bolt the thing to the hood in a way that will
shield one side (the one that will be inside the cowl) and also simulate
the AOA of the cowl bottom on climbout.

Drive around a while at 60 to 70mph and then report back here with what
you find out.


--
----Because I can----
http://www.ernest.isa-geek.org/
------------------------

[Bob Kuykendall]

Earlier, (Jay) wrote:

> You're going to have drag anyway as the air goes around the cowl,
> might as well use it to do something useful. So in this case, the
> cooling causes no ADDITIONAL drag, right?...

If you think you have a good idea, then fine, try it. Make a
prototype, test it under representative conditions, and publish your
results. If the results bear out your assertions, you will be hailed
as an insightful genius. If there are competitive advantages to your
idea, you can expect to see swift application of it to a wide variety
of heat exchange situations.

Anyhow, yammering about your idea here on Usenet accomplishes less
than zero, since it takes up time that you could otherwise be using to
implement and test your idea. From the fact that you persist in
arguing about it in this forum, I can only conclude that you are more
interested in the argument that in the idea under discussion.

And that's a shame, since your surface radiator idea would be pretty
easy to prototype. All you need is an old pickup truck, an old car
hood, a bunch of copper tubing, a bunch of cheap plumber's solder, and
a propane torch. Oh, and a driver's license...

I mean, I think it's a dead-end idea, but I'm prepared to be
demonstrated wrong. But if you persist in just telling folks that
they're wrong without a shred of either empirical evidence or
engineering support, you're gonna stay pigeonholed in a lot of folks'
chucklehead files.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com

[Barnyard BOb --]

>I mean, I think it's a dead-end idea, but I'm prepared to be
>demonstrated wrong. But if you persist in just telling folks that
>they're wrong without a shred of either empirical evidence or
>engineering support, you're gonna stay pigeonholed in a lot of folks'
>chucklehead files.
>
>Thanks, and best regards to all
>
>Bob K.
++++++++++++++++++++++++++++++++++++++

WoW.
Definitely time to fish or cut bait. <g>

P.S.
This sure is out of character for you, Bob.


Barnyard BOb --

[Jay]

(Bob Kuykendall) wrote in message
> If you think you have a good idea, then fine, try it. Make a
> prototype, test it under representative conditions, and publish your
> results. If the results bear out your assertions, you will be hailed
> as an insightful genius. If there are competitive advantages to your
> idea, you can expect to see swift application of it to a wide variety
> of heat exchange situations.

I think its too soon make that step, I'm not sure what the proportions
need to be.

> Anyhow, yammering about your idea here on Usenet accomplishes less
> than zero, since it takes up time that you could otherwise be using to
> implement and test your idea. From the fact that you persist in
> arguing about it in this forum, I can only conclude that you are more
> interested in the argument that in the idea under discussion.

"Listen, I'm not here for an argument..." (Python)
I didn't come to the newsgroup to as advice. The idea was to have a 2
way discussion, I guess you could call that yammering. Sometimes in
the early stages of a development you just brain storm and bounce
ideas off different people's heads. Its a fun excercise for people
who like to think and interact. Its true, the CNC isn't chewing
aluminum and there aren't any flames yet, so it isn't quiet as
exciting, but until you think you've got the theory understood, you're
wasting time and material trying to construct something that will
likely take an inordinate amount of experimentation to optimize.
Thats the difference between an engineer and a tech I guess.

> And that's a shame, since your surface radiator idea would be pretty
> easy to prototype. All you need is an old pickup truck, an old car
> hood, a bunch of copper tubing, a bunch of cheap plumber's solder, and
> a propane torch. Oh, and a driver's license...

You need a propeller and cowl as well. The success of the idea may
hinge on the turbulence in the prop wash which decays very quickly as
you get further from the prop blade.

> I mean, I think it's a dead-end idea, but I'm prepared to be
> demonstrated wrong. But if you persist in just telling folks that
> they're wrong without a shred of either empirical evidence or
> engineering support, you're gonna stay pigeonholed in a lot of folks'
> chucklehead files.

In a discussion its okay to disagree with someone as long as you can
supply a reason. The other person, can then attempt to address that
issue. This goes on and on until you've either come to the same
conclusion or some fundamental point on which there is a disagreement
which must be settled by experimental data or a more detailed off-line
analysis.

> Thanks, and best regards to all
>
> Bob K.
> http://www.hpaircraft.com

[Bill Daniels]

OK, Bob and Jay, chill out. You're both cool engineers and have a lot to
contribute. Lets just rattle the idea around a bit and see what comes out.

The skin radiator was been tried on the Schneider Cup seaplane racers in the
1930's and it worked, at least for that purpose. It probably worked much
better than the flat plate alternative seen on other aircraft from that era.
It might not have as much advantage over a highly efficient ducted radiator
like the P-51 used.

Skin radiators weren't really tried on military aircraft in WWII, at least
as far as I know, probably out of concern they would be very vulnerable to
enemy fire. After the war, people interested in performance were into jets
and not too interested in some weird pre-war radiator design even though it
might work fine.

Then there is a question of the effect of heating the boundary layer. Some
say that it will thicken and separate if the wing skin is heated. On the
other hand, some say it will have a turbulator effect and energize the
boundary layer. The Schneider Cup racers did not have laminar flow airfoils
so any effects, good or bad, might not have been noticed.

I have read a bit of work on "Hot Wing" aerodynamics and the results were
inconclusive as far as effects on the extent of laminar flow on the wing but
seemed to suggest a reduction in L/D which would be expected if the heating
disturbed the boundary layer.

It's possible, even likely, that a skin radiator would work best for cooling
and have the least negative effects on laminar flow if the surface chosen
were already subject to turbulent flow. The wing leading edge behind the
prop comes to mind.

Bill Daniels

"Jay" > wrote in message
om...
> (Bob Kuykendall) wrote in message
> > If you think you have a good idea, then fine, try it. Make a
> > prototype, test it under representative conditions, and publish your
> > results. If the results bear out your assertions, you will be hailed
> > as an insightful genius. If there are competitive advantages to your
> > idea, you can expect to see swift application of it to a wide variety
> > of heat exchange situations.
>
> I think its too soon make that step, I'm not sure what the proportions
> need to be.
>
> > Anyhow, yammering about your idea here on Usenet accomplishes less
> > than zero, since it takes up time that you could otherwise be using to
> > implement and test your idea. From the fact that you persist in
> > arguing about it in this forum, I can only conclude that you are more
> > interested in the argument that in the idea under discussion.
>
> "Listen, I'm not here for an argument..." (Python)
> I didn't come to the newsgroup to as advice. The idea was to have a 2
> way discussion, I guess you could call that yammering. Sometimes in
> the early stages of a development you just brain storm and bounce
> ideas off different people's heads. Its a fun excercise for people
> who like to think and interact. Its true, the CNC isn't chewing
> aluminum and there aren't any flames yet, so it isn't quiet as
> exciting, but until you think you've got the theory understood, you're
> wasting time and material trying to construct something that will
> likely take an inordinate amount of experimentation to optimize.
> Thats the difference between an engineer and a tech I guess.
>
> > And that's a shame, since your surface radiator idea would be pretty
> > easy to prototype. All you need is an old pickup truck, an old car
> > hood, a bunch of copper tubing, a bunch of cheap plumber's solder, and
> > a propane torch. Oh, and a driver's license...
>
> You need a propeller and cowl as well. The success of the idea may
> hinge on the turbulence in the prop wash which decays very quickly as
> you get further from the prop blade.
>
> > I mean, I think it's a dead-end idea, but I'm prepared to be
> > demonstrated wrong. But if you persist in just telling folks that
> > they're wrong without a shred of either empirical evidence or
> > engineering support, you're gonna stay pigeonholed in a lot of folks'
> > chucklehead files.
>
> In a discussion its okay to disagree with someone as long as you can
> supply a reason. The other person, can then attempt to address that
> issue. This goes on and on until you've either come to the same
> conclusion or some fundamental point on which there is a disagreement
> which must be settled by experimental data or a more detailed off-line
> analysis.
>
> > Thanks, and best regards to all
> >
> > Bob K.
> > http://www.hpaircraft.com

[Jean-Paul Roy]

This gets very boring. How about going back flying.
Cheers
"Morgans" <jisumorgan@charterdotjunkdotnet> a écrit dans le message news:
...
>
> "Barnyard BOb --" > wrote in message
>
> >
> > Barnyard BOb -- Have sharp stick. Will travel.
>
> Be careful not to poke your eye out! <g>
> --
> Jim in NC
>
>

[Barnyard BOb --]

"Jean-Paul Roy" wrote:

>This gets very boring. How about going back flying.
>Cheers
++++++++++++++++++++++++++++++++

How about you just crawl back in
your net cop hole and **** off?

May I suggest...
If you don't like what you read, don't read it.
Not my job to step aside to satisfy your whims.

I place no restrictions upon your speech. Therefore, please
do not **** with my rights in this unmoderated group.

Cheers to you, poor misguided soul.


Barnyard BOb

[ower]

B-yard S.O.B a (man?) with a kind soul and of good manners
has spoken. Maybe Jean-Paul was just exercising his right
to put forward his opinion (a god one at that).

ower


"Barnyard BOb --" > skrev i meddelandet
...
>
>
> "Jean-Paul Roy" wrote:
>
> >This gets very boring. How about going back flying.
> >Cheers
> ++++++++++++++++++++++++++++++++
>
> How about you just crawl back in
> your net cop hole and **** off?
>
> May I suggest...
> If you don't like what you read, don't read it.
> Not my job to step aside to satisfy your whims.
>
> I place no restrictions upon your speech. Therefore, please
> do not **** with my rights in this unmoderated group.
>
> Cheers to you, poor misguided soul.
>
>
> Barnyard BOb

[Jay]

At zero airspeed doesn't really matter what the heat transfer
capabilities are. During operation you'd like it to be the exact same
temperature as the coolant, this will ensure maximum transfer.

(Bob Kuykendall) wrote in message >...
> Earlier, (Jay) wrote:
>
> > ...And of course in big red letters
> > "HOT SURFACE- DO NOT TOUCH"...
>
> Well, if it stays hot, it isn't a very good heat exchanger, is it?
>
> Bob K.

[Jay]

Thats a great idea and I think the construction you've described is
close to what I'd imagined too. I'm not sure the test is equivalent
to the operating environment its intended for though. On climb out,
while the IAS may be 60-70MPH, the prop wash is a much higher speed.
Also, the prop wash is much more turbulent than the clean air on the
front of your wifes car, and that has a dramtic effect on the cooling
capability of that air. As I'd mentioned before, a smooth air flow
tends to build up a layer of warm air along the boundary that impeds
heat flow. Where in the turbulent case "new" cool air keeps coming in
contact with the hot aluminum.

Regards

On climb out Ernest Christley > wrote in message >...
> Jay wrote:
>
> > You might argue that the heat transfer for that area isn't sufficient,
> > and I think the analysis needs to be done, but not by a direct
> > comparison of area from an automobile finned type radiator. The
> > conditions are just too different to make that meaningful. A bottom
> > up calculation that includes heat transfer effects of turbulent air,
> > heat transfer properties of materials (likely Aluminum), waste heat
> > from engine, etc.
>
> So do it. Take a couple of 2'x2' sheat of .035 aluminum and a few
> strips of 3/8" flat aluminum. Lay the flat strips on one piece of sheet
> so that it forms sides and an interior maze that the water will have
> to flow through. Drill, caulk and rivet it together. Add a spout for
> the water to go in and come out with temp probes at each one. Add a
> couple of T joints to the plumbing of your wife's car (don't let her
> catch you at it) and bolt the thing to the hood in a way that will
> shield one side (the one that will be inside the cowl) and also simulate
> the AOA of the cowl bottom on climbout.
>
> Drive around a while at 60 to 70mph and then report back here with what
> you find out.

[Jay]

Hi Bill,

Thanks for joining the fray.

At first I was also thinking the wing location for the radiator made a
lot of sense, but then thinking about the complexity of installation
caused me to reconsider. And along the way I found that the turbulent
characteristic of air adds greatly to its heat transfer
characteristics. Since turbulence drops exponentally with distance,
putting the heat transfer surface on the cowl near to the propeller
made more and more sense. That location allows people to go with the
"firewall forward" type of thinking and keep radiator hoses short.

As far as the aerodynamic effects, I hadn't figured there would be too
much effect because of the amount of heat added to this huge volume of
air. I guess it would make the air slightly less dense around the
fusalage and back dispating as the boundary air mixes with more of the
air mass.

p.s. What you were refering to a "flat plate" is really the
traditional blow through type radiator see on autos and other low
speed vehicles. Right?


"Bill Daniels" > wrote in message >...
> OK, Bob and Jay, chill out. You're both cool engineers and have a lot to
> contribute. Lets just rattle the idea around a bit and see what comes out.
>
> The skin radiator was been tried on the Schneider Cup seaplane racers in the
> 1930's and it worked, at least for that purpose. It probably worked much
> better than the flat plate alternative seen on other aircraft from that era.
> It might not have as much advantage over a highly efficient ducted radiator
> like the P-51 used.
>
> Skin radiators weren't really tried on military aircraft in WWII, at least
> as far as I know, probably out of concern they would be very vulnerable to
> enemy fire. After the war, people interested in performance were into jets
> and not too interested in some weird pre-war radiator design even though it
> might work fine.
>
> Then there is a question of the effect of heating the boundary layer. Some
> say that it will thicken and separate if the wing skin is heated. On the
> other hand, some say it will have a turbulator effect and energize the
> boundary layer. The Schneider Cup racers did not have laminar flow airfoils
> so any effects, good or bad, might not have been noticed.
>
> I have read a bit of work on "Hot Wing" aerodynamics and the results were
> inconclusive as far as effects on the extent of laminar flow on the wing but
> seemed to suggest a reduction in L/D which would be expected if the heating
> disturbed the boundary layer.
>
> It's possible, even likely, that a skin radiator would work best for cooling
> and have the least negative effects on laminar flow if the surface chosen
> were already subject to turbulent flow. The wing leading edge behind the
> prop comes to mind.
>
> Bill Daniels

[Bill Daniels]

Hi Jay,

Yes, the "flat plate" refers to an automotive-like placement of the
radiator.

I suspect that the skin radiator might need a much larger area than a
honeycomb type heat exchanger in a duct since the stagnant boundary layer on
a cowling would limit heat transfer to the free-stream flow. The area
available on a cowling might not be enough either.

I would be very suspicious of calculations comparing the heat transfer
efficiency of skin vs. honeycomb radiators. This is an area were
experimental data is needed.

Another area where I would like to see some experimental data is the
"Radiator Ramjet" (just to pick a controversial term) where the radiator is
in a tube and the heated air exits the rear of the tube at a higher velocity
than the cool air entering the front of the tube, theoretically producing a
small amount of thrust that offsets the drag of the radiator.

Bill Daniels
"Jay" > wrote in message
om...
> Hi Bill,
>
> Thanks for joining the fray.
>
> At first I was also thinking the wing location for the radiator made a
> lot of sense, but then thinking about the complexity of installation
> caused me to reconsider. And along the way I found that the turbulent
> characteristic of air adds greatly to its heat transfer
> characteristics. Since turbulence drops exponentally with distance,
> putting the heat transfer surface on the cowl near to the propeller
> made more and more sense. That location allows people to go with the
> "firewall forward" type of thinking and keep radiator hoses short.
>
> As far as the aerodynamic effects, I hadn't figured there would be too
> much effect because of the amount of heat added to this huge volume of
> air. I guess it would make the air slightly less dense around the
> fusalage and back dispating as the boundary air mixes with more of the
> air mass.
>
> p.s. What you were refering to a "flat plate" is really the
> traditional blow through type radiator see on autos and other low
> speed vehicles. Right?
>
>
> "Bill Daniels" > wrote in message
>...
> > The skin radiator was been tried on the Schneider Cup seaplane racers in
the
> > 1930's and it worked, at least for that purpose. It probably worked
much
> > better than the flat plate alternative seen on other aircraft from that
era.
> > It might not have as much advantage over a highly efficient ducted
radiator
> > like the P-51 used.
> >
> > Skin radiators weren't really tried on military aircraft in WWII, at
least
> > as far as I know, probably out of concern they would be very vulnerable
to
> > enemy fire. After the war, people interested in performance were into
jets
> > and not too interested in some weird pre-war radiator design even though
it
> > might work fine.
> >
> > Then there is a question of the effect of heating the boundary layer.
Some
> > say that it will thicken and separate if the wing skin is heated. On
the
> > other hand, some say it will have a turbulator effect and energize the
> > boundary layer. The Schneider Cup racers did not have laminar flow
airfoils
> > so any effects, good or bad, might not have been noticed.
> >
> > I have read a bit of work on "Hot Wing" aerodynamics and the results
were
> > inconclusive as far as effects on the extent of laminar flow on the wing
but
> > seemed to suggest a reduction in L/D which would be expected if the
heating
> > disturbed the boundary layer.
> >
> > It's possible, even likely, that a skin radiator would work best for
cooling
> > and have the least negative effects on laminar flow if the surface
chosen
> > were already subject to turbulent flow. The wing leading edge behind
the
> > prop comes to mind.
> >
> > Bill Daniels

[Corky Scott]

On Tue, 15 Jul 2003 11:54:37 -0600, "Bill Daniels"
> wrote:


>
>Another area where I would like to see some experimental data is the
>"Radiator Ramjet" (just to pick a controversial term) where the radiator is
>in a tube and the heated air exits the rear of the tube at a higher velocity
>than the cool air entering the front of the tube, theoretically producing a
>small amount of thrust that offsets the drag of the radiator.
>
>Bill Daniels
>"Jay" > wrote in message
om...
>> Hi Bill,

You don't need experiental data for this Bill, you just described the
P-51 Mustang cooling system.

However, even with three heat exchangers putting out heat into the
exhaust air and a 1400 horsepower engine producing the heat, the
Mustang never actually managed to get a net thrust out of the system.
In addition, the point where the cooling system was ***ALMOST***
equalling drag was a very specific speed and altitude. I forget the
exact height but it was above 20,000 feet and the speed was over 300
mph. Only under those circumstances did the power being generated and
the speed being flown produce the necessary heat to accelerate the
exhaust air flow to nearly cancel out cooling drag. By the way, most
of the cooling systems did this to some fashion, but the Mustang was
the first to actually design the cooling system to really benefit from
it. This concept was researched and written up by a British
aerodynamicist by the name of Meridith, and the produced thrust became
known as the "Meridith Effect".

North American designed the Mustang's system using the best
aerodynamicists available at the time and with virtually unlimited
resources to manufacture the kind of heat exchangers that would work
in this environment.

By the end of WWII, almost all research into liquid cooled systems
came to a halt as jet powered aircraft became the future for military
aircraft.

I'm not an aerodynamics engineer, just a home builder. But my
impression is that most relatively slow homebuilt or GA airplanes do
not produce the heat needed to really accelerate the exhaust flow to
make much out of the Meridith Effect. After all, we're always leaning
out and cruising at reduced power settings. We have big wings, for
the most part, and a lot of drag. Something really slippery like a
Long EZ or Vari EZ or Glassair or Lancair might be fast enough to
benefit, but getting the cooling system designed and fitted within the
tiny wetted area of the fuselage might be nearly impossible.

From my personal point of view, it's far more important to make sure
the cooling system does the job all day and every day and on the
ground too than to agonize over a few mph, real or imaginary.

Corky Scott

[Bill Daniels]

"Corky Scott" > wrote in message
...
> On Tue, 15 Jul 2003 11:54:37 -0600, "Bill Daniels"
> > wrote:
>
>
> >
> >Another area where I would like to see some experimental data is the
> >"Radiator Ramjet" (just to pick a controversial term) where the radiator
is
> >in a tube and the heated air exits the rear of the tube at a higher
velocity
> >than the cool air entering the front of the tube, theoretically producing
a
> >small amount of thrust that offsets the drag of the radiator.
> >
> >Bill Daniels
> >"Jay" > wrote in message
> om...
> >> Hi Bill,
>
> You don't need experiental data for this Bill, you just described the
> P-51 Mustang cooling system.
>
> However, even with three heat exchangers putting out heat into the
> exhaust air and a 1400 horsepower engine producing the heat, the
> Mustang never actually managed to get a net thrust out of the system.
> In addition, the point where the cooling system was ***ALMOST***
> equalling drag was a very specific speed and altitude. I forget the
> exact height but it was above 20,000 feet and the speed was over 300
> mph. Only under those circumstances did the power being generated and
> the speed being flown produce the necessary heat to accelerate the
> exhaust air flow to nearly cancel out cooling drag. By the way, most
> of the cooling systems did this to some fashion, but the Mustang was
> the first to actually design the cooling system to really benefit from
> it. This concept was researched and written up by a British
> aerodynamicist by the name of Meridith, and the produced thrust became
> known as the "Meridith Effect".
>
> North American designed the Mustang's system using the best
> aerodynamicists available at the time and with virtually unlimited
> resources to manufacture the kind of heat exchangers that would work
> in this environment.
>
Yeah, North American did well with the Mustang given that it was just old
"slide rule" engineers one generation ahead of me working on it. I imagine
the kids these days using Computational Fluid Dynamics programs and modern
materials could improve on the Meridith Effect - maybe a lot.

I don't want to get too far form the original posters idea on skin
radiators. That idea is worth some experiments too.

Bill Daniels

[RJ Cook]

The Mustang's cooling system (an external combustion ramjet) is probably
about as good as it is going to get utilizing radiators for heat exchangers,
because the thrust produced by a ramjet is very dependent on internal
efficiencies (drag). A radiator is a very high drag ramjet heat source
(combustor) because of its large surface area, and relatively poor
aerodynamics. The net thrust of a ramjet type cooling system could be
increased if a more efficient (lower drag) method is found to transfer the
heat to the internal airflow.

I agree with Corky's statement that effective cooling is more important (the
Mustang's was inadequate for prolonged ground operation) than a few miles
per hour in cruise for slower aircraft. However, for aircraft cruising
above 150-175 MPH, I believe cooling drag is certainly high enough to be of
interest to any designer.

RJ

"Corky Scott" > wrote in message
...
> On Tue, 15 Jul 2003 11:54:37 -0600, "Bill Daniels"
> > wrote:
>
>
> >
> >Another area where I would like to see some experimental data is the
> >"Radiator Ramjet" (just to pick a controversial term) where the radiator
is
> >in a tube and the heated air exits the rear of the tube at a higher
velocity
> >than the cool air entering the front of the tube, theoretically producing
a
> >small amount of thrust that offsets the drag of the radiator.
> >
> >Bill Daniels
> >"Jay" > wrote in message
> om...
> >> Hi Bill,
>
> You don't need experiental data for this Bill, you just described the
> P-51 Mustang cooling system.
>
> However, even with three heat exchangers putting out heat into the
> exhaust air and a 1400 horsepower engine producing the heat, the
> Mustang never actually managed to get a net thrust out of the system.
> In addition, the point where the cooling system was ***ALMOST***
> equalling drag was a very specific speed and altitude. I forget the
> exact height but it was above 20,000 feet and the speed was over 300
> mph. Only under those circumstances did the power being generated and
> the speed being flown produce the necessary heat to accelerate the
> exhaust air flow to nearly cancel out cooling drag. By the way, most
> of the cooling systems did this to some fashion, but the Mustang was
> the first to actually design the cooling system to really benefit from
> it. This concept was researched and written up by a British
> aerodynamicist by the name of Meridith, and the produced thrust became
> known as the "Meridith Effect".
>
> North American designed the Mustang's system using the best
> aerodynamicists available at the time and with virtually unlimited
> resources to manufacture the kind of heat exchangers that would work
> in this environment.
>
> By the end of WWII, almost all research into liquid cooled systems
> came to a halt as jet powered aircraft became the future for military
> aircraft.
>
> I'm not an aerodynamics engineer, just a home builder. But my
> impression is that most relatively slow homebuilt or GA airplanes do
> not produce the heat needed to really accelerate the exhaust flow to
> make much out of the Meridith Effect. After all, we're always leaning
> out and cruising at reduced power settings. We have big wings, for
> the most part, and a lot of drag. Something really slippery like a
> Long EZ or Vari EZ or Glassair or Lancair might be fast enough to
> benefit, but getting the cooling system designed and fitted within the
> tiny wetted area of the fuselage might be nearly impossible.
>
> From my personal point of view, it's far more important to make sure
> the cooling system does the job all day and every day and on the
> ground too than to agonize over a few mph, real or imaginary.
>
> Corky Scott

[Corky Scott]

On 17 Jul 2003 09:34:54 -0700, (Jay) wrote:

>On the Meredith Effect. Intuitively I don't see how its supposed to
>work. You take air in the front of the scoop, you heat it up, and it
>expands (ideal gas law). How does the air know thats only supposed to
>go out the rear?

Jay, let's review the path the air takes through a radiator type
aviation cooling system and what happens to it.

Before I begin, you should understand that the air from the cooling
system MUST BE EXHAUSTED INTO A LOW PRESSURE AREA. If you do not
understand this first point, you will have huge problems with any
system you attempt to develop.

So let's presume we have situated the exhaust opening such that it
empties into the afore mentioned low pressure zone somewhere on the
fuselage, and we're moving through the air at cruising speed.

The air is directed into the intake opening because we designed it
such that it scoops in air and is pointed at the airflow. It flows
into the intake duct and the duct expands at anywhere from 7 to 15
degrees or so until it gets to the radiator, which is necessarily
larger than the intake opening. While the duct is expanding to the
size of the radiator, the air has lost some velocity but it's gained
pressure. We have selected a fin density compatible with the speed we
have slowed the air down to, so as to allow the air time to absorb
heat from the fins.

It flows through the radiator and removes heat from the fins. The air
is now heated much more than it was when it entered the duct. We've
sealed the space surrounding the radiator because air is lazy, it
doesn't want to go where you want it to go, it will seek easier
passages if you let it. If it can bypass the radiator, it will, thus
robbing you of it's ability to remove heat from the radiator.

Now the air is behind the radiator and it's greatly heated and
expanded. Why doesn't it want to blow forward? Because it's lazy,
remember? It wants to take the easiest path and that path is toward
the low pressure area we first stipulated was necessary (high pressure
at the inlet, low pressure at the outlet). But the duct is now
narrowing. This compresses the air and accelerates it. It cannot do
anything but head to the rear at ever increasing velocity, blowing out
the exit outlet parallel to the slipstream.

It's the exit parallel to the slipstream in it's accelerated state
that recovers the drag imposed while it entered the inlet and pushed
through the radiator face.

In effect, it's a low grade pulsejet engine with the radiator and the
rearward velocity of the air through the system acting as the vanes
that normally slam shut against the combustion of a real pulsejet,
forcing the products of the combustion out the tailpipe.

Does this clear things up?

Corky Scott

PS, the system described above is optimal. The reality is that the
confines of the engine compartment, protrusions and the usual
narrowness of the fuselage contribute to making almost all cooling
systems less than optimal. That's why I emphasized that in the real
world, the most important thing is that the system cool properly
first, and worry about the drag it produces later.

[RJ Cook]

Excellent answer A, in cruise flight, there is little difference between a
propeller's slipstream and freestream velocity.

Today's props are very efficient (near 90% max) and create little
turbulence, with the exception of the tip's vortex . I have opened the
window on a c-150 and put my arm out to feel the propwash, and other than a
slight pulsing the only substantial disturbance is where my hand penetrates
the prop's tip vortex ring. Try it some time. This is not to say the flow
across a fuselage behind a prop is laminar, I'm nearly certain it isn't as
laminar boundary layers needs very little disturbance to become turbulent,
but total chaos does not exist within the slipstream behind a prop.

The stagnation point can also be defined as the point on the leading edge of
a surface/component that the velocity normal (perpendicular) to the skin is
0.

The Meredith effect, and ramjets in general, create stream flow by
maintaining a negative pressure gradient (high to low pressure) streamwise
within the duct/engine. This gradient is created by area differentials,
fixed or variable, between the inlet and exhaust. The inlet area is smaller
than the exhaust area, and thrust is a product of the duct's massflow times
the inlet's and exhaust's differential velocities. In the case of a cooling
system, if the internal aero losses are to high, due to friction across
radiators, etc., then the net thrust may be negative.

RJ



> wrote in message ...
> You'd be surprised how *little* a prop accellerates the air. The thrust
is a
> product of how much air is accellerated and the change in velocity. A
prop
> going 150 mph is working on a lot of cubic feet of air per second - a cyl
of air
> the diameter of the prop and the distance the airplane goes in a second.
> Changing the velocity of that amount of air just 10 mph gives oodles of
thrust.
> The back prop on a 337 is seeing air that's moving backward at about 15
mph.
>
> The slower the airplane is going, the more it has to accellerate the air
to get
> the same thrust, because it's accellerating less air.
>
> The stagnation point is the point on the leading edge of the wing where
the air
> is splitting - some goes over the wing, some goes under the wing. Above
the
> stagnation point the air goes over, below, under. AT the stagnation point
> (which is very, very small) it piles up then falls off one way or the
other.
>
>
> In article >,
> says...
> >
> >I'm not clear on what the stagnation point is. Maybe you can expand
> >you explanation more?
> >
> >My line of thinking was basically this:
> >Airplane flies in clean air, propeller bites into clean air at high
> >sub sonic speeds, creates column of high velocity air, but at the same
> >time, wastes bunches of energy also churning it up. As air moves back
> >past fuselage and wing roots, churning energy disipates (decaying
> >exponentially with distance from prop). Now I'm sure that the
> >airframe itself introduces some turbulence of its own, but this is
> >distributed all over and is less concentrated at its source(s)
> >
> >I think a lot of people are thinking about airplanes minus the
> >propeller or thinking of pusher configurations. This may be one of
> >the reasons why pusher power plants seem often have over-heating
> >issues. Taking the 337 for example: On the surface you'd say, the
> >back of the airplane must be traveling at the same speed as the front
> >of the aiplane so what's the deal? But going to the second order
> >effects, the front engine lives in an air flow with speeds much higher
> >than IAS and the turbulence of the cooling stream for the front engine
> >is MUCH higher than it is the intake scoop for the rear engine because
> >of the aformentioned exponential decay of the turbulence in the prop
> >wash.
> >
> >On the Meredith Effect. Intuitively I don't see how its supposed to
> >work. You take air in the front of the scoop, you heat it up, and it
> >expands (ideal gas law). How does the air know thats only supposed to
> >go out the rear?
> >
> >Regards
> >
> >"RJ Cook" > wrote in message
> >...
> >> Jay,
> >>
> >> The turbulence within a boundary layer over an aerodynamic surface
INCREASES
> >> with distance DOWNSTREAM of the stagnation point. The cowl of an
aircraft
> >> would have less turbulence within the boundary layer than nearly
anywhere
> >> else on the fuselage.
> >>
> >> RJ
>

[Jay]

Thanks for contributing to the fray...

I wasn't really talking about cruise so much as I was talking about
climb-out: high engine output, low vehicle speed, high AOA. Arm test-
If you can feel pulsing 5 feet back from the prop, then you know that
there is air of varying velocities washing over your arm. And since
you also know that the distubance decays very quickly at first and
then more gradually as time (and airplane) goes by, the disturbance is
much higher a one foot behind the propeller. I'm sure its not total
chaos, and it isn't laminar either, something between the two.
Question is, does the amount of turbulence produced, boost the heat
transfer capability of that air enough for a surface radiator on the
front/under surface of the cowl to work for a 100-200HP engine?

And yes, the first step is to make sure that you've got reliable
cooling. Okay, check, you've done that. Now what can be done to
eliminate one of the largest sources of drag? If this actually
worked, it would be a huge incentive for more water cooled (AKA auto
conversion) power plants in aircraft.



"RJ Cook" > wrote in message >...
> Excellent answer A, in cruise flight, there is little difference between a
> propeller's slipstream and freestream velocity.
>
> Today's props are very efficient (near 90% max) and create little
> turbulence, with the exception of the tip's vortex . I have opened the
> window on a c-150 and put my arm out to feel the propwash, and other than a
> slight pulsing the only substantial disturbance is where my hand penetrates
> the prop's tip vortex ring. Try it some time. This is not to say the flow
> across a fuselage behind a prop is laminar, I'm nearly certain it isn't as
> laminar boundary layers needs very little disturbance to become turbulent,
> but total chaos does not exist within the slipstream behind a prop.
>
> The stagnation point can also be defined as the point on the leading edge of
> a surface/component that the velocity normal (perpendicular) to the skin is
> 0.
>
> The Meredith effect, and ramjets in general, create stream flow by
> maintaining a negative pressure gradient (high to low pressure) streamwise
> within the duct/engine. This gradient is created by area differentials,
> fixed or variable, between the inlet and exhaust. The inlet area is smaller
> than the exhaust area, and thrust is a product of the duct's massflow times
> the inlet's and exhaust's differential velocities. In the case of a cooling
> system, if the internal aero losses are to high, due to friction across
> radiators, etc., then the net thrust may be negative.
>
> RJ
>