Damit Tracy, don't get me started thinking about this :-) Has
anyone tried using one of these for oil yet? Certainly the
pressure should be OK. Arrrrrgh...
Rusty (not flying again soon, but certainly before Tracy's
RV-8 <g>)
I am using one for an oil cooler, mounted up in the nose cowl. I
have not yet flown, but cooled great on ground run ups. Never went over
180 in the pan even when water temp went to 230.
Lonnie
Sorry to stir the pot Rusty! But, Glad to hear the evap
core is working well on the ground for oil cooling Lonnie. The
main reason I want to use one is for the more efficient use of
the dynamic pressure available at flight speeds. The
stock coolers work well but I think they require more CFM to do the
job. Minimizing cooling drag (as many of you are tired
of hearing me preach : ) is largely a mater of minimizing CFM used to do
the job.
When I get the time, I want to correlate the excellent data
that Ed has been sharing with how I think cooling drag
works. Some of it is counterintuitive.
For example, minimizing aircraft cooling drag can often
mean increasing the turbulence (drag) through the
heat exchanger.
Tracy Crook
I'll be
interested to hear your theories, Tracy. For one thing it appears
that once you trip the boundary layer into turbulent flow, you have
encountered 75-80% of the drag you are going to encounter. Adding
more inches after that point does little to increase drag further.
Drag is proportional to frontal area as we all know, so that would also
support the thicker (rather than larger) is better for cooling (in our
application where we do have higher dynamic pressure to work for
us).
Also my
calculations indicates that the evaporator core has much less drag than
one might think based on its thickness. Most heat exchangers of the type
used as radiators have a openness ratio of around .70 - 75 while my
measures and calculations shows the GM cores has an openness ratio of
around 0.81 further indicating less air resistance.
If you think
about it, it makes sense there would not be much resistance to air flow in
the core as it has a puny electric motor in the car to force air
through it, so it is undoubtedly designed not to have much air
resistance.
So I wanna'
hear your story
Ed
Anderson