Sent: Wednesday, December 24, 2003 1:20
PM
Subject: [FlyRotary] Re: Streamline Vs
Parabolic Ducts/Diffusers
Not sure I follow this correctly. It sounds like you are saying the
the performance of the parabolic is infearior to the streamlined. From
my perspective, the one that results in the maximum pressure at the face of
the heat exchanger, wins.
Isn't Pd more on the parabolic? Who cares if it is a linear
increase or not? Or I may have missed something........
Tracy
Sorry, my fault, Tracy. The scale for the dynamic
pressure is on the right hand side of the charts and I used two unequal scales
for dynamic pressure which made it appear that the parabolic was a bit on the
better side. The values for dynamic pressure were correct on both
charts, its just that the different Y axis scales on the two different charts
gave an erroneous impression. I have made the scale the same on this set
of charts and the difference is readily apparently - in favor of the
streamline duct.
However, I am finding that there are other factors that
apparently are even more significant than the type of
duct. Ignoring the wall curves for the moment, it
appears that the ratio between inlet and core areas can be
extremely crucial. Also if the exit area is smaller than the core
then that also has an important impact. But, assuming the exit
area is at least as large as the core, then there is a critical area ratio
which if your intake/core area ratio is above that limit, losses are
minimized, but if they go below this critical ratio then losses go up very
quick and dramatically. Unfortunately, that critical ratio is dependent
on the pressure drop coefficient of the core, so it is not as easy to
come by as you would like. I am trying to figure it out for the GM
cores.
What also becomes clearer is that given sufficient air
mass flow and surface area, just about any configuration will cool your
engine. The problem is that it will be larger and heavier than an
optimum system design - perhaps much larger {:>).
Going to have to be more cautious when I protray
something as the context makes all the difference in
interpretation.
Ed