Hi Ira
"Just like cooling inside the cowl, cooling of the
instrument panelcan be non-or counter intuitive.In some engine
cowls, the air pressure gradients and consequent flow can be
stagnant or even flowing backward."
First off bottom line is
figures don't lie, but liars sure do figure. When I am able to testI
will post results of how my fans influence cooling.
I don't think it
is a fair comparison to compare dynamics of a Europa cowl with instrument
module cooling. In cowl you are trying to force rarefied air down, it does
not want to do that. As far as stalled or reversing air, you are taking
accelerated air and trying to force it through a less than ideal duct in
addition to forcing hot air down. The only means of propulsion is by
pushing it.
In my instrument module, dynamics are much more likely to
be that of a base board radiator. If there is no heat and if it becomes
stalled, not too much a problem. If it is hot inside, then through natural
convection hot will go to top. I have a nice gap along bottom of module to
allow cabin air to enter. Thus doing nothing natural convection
"should" create a flow. Fans at top only enhance the natural
convection.
Comforting that not too many folks have had too much
problems with overheating instruments or radios which I based my decision
to help only a little with cooling and get a bit of demisting as well.
FWIW I measured the pressure at the top of a hot air balloon with ambien
60F and top of balloon inside 200F at sealevel, pressure was
.008psi, at mouth of balloon .000psi, not too much pressure but amazing
how much flow can be had.
Ron Parigoris
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