This is interesting but it flies in the face of what is happening in
the auto industry in some regards. We shall find out shortly about
the flow through thicker rads. It is also not intuitive as aero drag
in a pipe is proportional to the length of the pipe.


Paul Lamar

I agree that there is something odd about the info on the Stewart site.
It's an odd mix of facts,  questionable information and especially, lack of
useful conclusions.

Can there be any logical explanation for their statement that there is very
little difference in airflow resistance between thick and thin rads?  None
is given so I'm not convinced that they really understand the subject.

The statement about thicker rads making less cooling than thin rads  was at
least explained by their explaination (due to less turbulent coolant flow).
They also explained that making the thick rad a double pass restored the
velocity and turbulance but did not say what the net result was.  That would
be the only useful bit of info we could use.  It's missing.

Then they talk about thicker rads with smaller cross section tubes that
restore the turbulance needed for effecient heat transfer.  Again, no bottom
line conclusion is given.  So what's the story, do those thick rads work or
not?

To me this gives the impression that they are trying to impress the reader
with their vast knowledge of the subject but not give out any useful
information.

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

I also wonder about the methodology of their test. For example: I don't
know of a car in the world where the rad is not placed directly in
front of the engine block. Everything I have learned from K & M,
Kayes & London and my own rad test box indicate that this will
reduce the flow through the rad.

(also see oblique rads on www.thecarricos.com/ACRE/)

Did they test thick verses thin rads with this configuration?

Their results could be explained by:

A secondary effect (if it exist) is that something too close to a thin
rad is worse than something too close to a thick rad. This is because the
exit velocity is probably(?) higher on a thin rad and therefore the
dynamic pressure build up on the face of the obstruction  and behind the
rad is higher for a thin rad consequently obstructing the flow more.

Paul Lamar

Can't speak for other mfg's, but GM vehicles that use a single or double
pass rad on a particular engine will use a 4 pass on the heavy duty
cooling opton on the same vehicle , with the same frontal area.
Royce

 
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