Surface radiators for water cooled engines

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)

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

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)

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

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

Earlier, (Jay) wrote:

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

Oh, gosh, can I quote you on that?

;}

Bob K.

Sure, be my guest.

(Bob Kuykendall) wrote in message om...
Earlier, (Jay) wrote:

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

Oh, gosh, can I quote you on that?

;}

Bob K.