Ernest,
looking at your duct (looks very good as it is.... mind you), it seems it would have been no more work (than to plot coordinates) to make it a near perfect Streamline.
Why did you not go for it?
Thomas
On 6/1/07, Ernest Christley <echristley@nc.rr.com> wrote:
Bobby J. Hughes wrote:
>
> I can't find the post but maybe someone else has it or remembers who
> posted it. Could have been on PL's listed also.
>
> If I remember correctly a one inch square grid was mapped and measured
> on the backside of a radiator. The top side was a wedge of some sort. I
> do not remember if the measurements were pressure or airspeed. The data
> indicated that more air was flowing through the core at the narrow end
> of the wedge and less air as the wedge opened up toward the source.
>
>
>
For a naive wedge, this would be the case. A barn door won't make an
easily controllable wing, either. However, it is not difficult to build
a duct that will flow air evenly through a radiator core place at an
acute angle. It is no more difficult than building a naive wedge, but
it does require some preparation to map out the correct coordinates.
I attached a 3ft 'tube' constructed of cardboard to the front of my oil
cooler, added a large box to the end, then inserted a leaf blower into
the side. I was trying to assure a even flow down the length of the
tube. I measured the exit air with a borrowed sensitive digital
barometer. I attached a 2" diameter spray-can cap to the end of the
static probe to capture the dynamic pressure exiting the cooler core.
Higher velocity would have to translate directly to higher static
pressure. I had less than a 10% differential across the face of the core.
This "I tried one thing and it didn't work, therefore it must be
impossible" line of thinking belongs on MythBusters or the Discovery
Channel, not in real development environments. This experiment provided
a single data point. The conclusion should not have been that wedges
don't work. It should be that this configuration didn't work, which
should lead to questioning what is the root cause of the failure found
in simple laws of physics (Ooops! I'm starting to sound like Bob
Knuckolls here.)
The root cause is the air's velocity is converted to pressure almost
exclusively at the rear of the duct. Can that be modified? Sure. Add
some diverting vanes that block the air at multiple points. There will
be multiple high pressure areas in front of the core, which translates
directly to multiple high flow areas. Are there other methods? How
about designing the duct so that the air is slowed in such a way that
it's velocity will be converted to pressure evenly across the face of
the core. K&W, chapter 12, has a diagram of how to shape it. I've
verified to my satisfaction that it works (I could have made some
modifications to make the distribution more even, but <10% was plenty
good enough). It is simpler and lighter than any other method you can
come up with, because it is just a duct that you will have to have anyway.
http://www.ernest.isa-geek.org/Delta/Pictures/OilCoolerDuctIntake.jpg
http://www.ernest.isa-geek.org/Delta/Pictures/OilCoolerDuctTop.jpg
http://www.ernest.isa-geek.org/Delta/Pictures/OilCoolerInletDuctTest1.jpg
--
Homepage: http://www.flyrotary.com/
Archive and UnSub:
http://mail.lancaironline.net:81/lists/flyrotary/List.html
|