----- Original Message -----
Sent: Sunday, November 02, 2003 10:03
AM
Subject: [FlyRotary] Re: radiator at cowl
outlet?
I would
think baffling that channels some air over the pipes and turbo and out the
cowling around the radiators would be another solution.
Hi Marko. I've been
thinking about that option as well. Since the turbo will account
for most of the unwanted heating, it certainly makes sense to try to
duct as much of that heat out of the cowl as possible. Another
thing that I'll add to the new cowl is a small hatch directly above the
turbo. This will be something that can be opened after shutdown, to
allow the heat to escape.
Rusty
HI Rusty,
Been think (always a bad idea in
my case) about your concern of heating the air before the radiator (if
installed in the outflow area). While there is no question there would
be some heating by such things as the turbo, etc. I am not certain that
it would significantly effect the air temperature, particularly in
flight.
Heres what my rational is based on. A single GM
evaporator core that we use calculates out to having approx 7000 square inches
(actually a bit more) of surface area (fins and tubes) thats approx
48 square feet of surface area for one core. From whats been reported
the air temp rise through a core is approx 20-30F getting rid of
all the coolant heat the engine needs to have
rejected
Now you wouldn't want air 30F higher than ambient
going into your rear mounted radiator, but I'll bet if you estimated the
surface area of your turbo and other significant heat generators that you
won't come up with anywhere near 48 square feet. Furthermore if you
shield the worst heat producer (your turbo and exhaust), I would imagine you
might find your air temp not increasing that much before it reaches your
radiator.
I intitially was concerned about the same type of
thing. I felt that if I ducted the rear of my radiators to my side
louvers that would keep the hot air from "reheating" the engine. Well,
it seemd to actually make matters worst (I suspect the ducts were restricting
the expanding hot air coming out of the radiators). Tracy Crook
convinced me that the additional heat content (as opposed to temperature)
blowing over the engine was insignificant in adding to the heat load.
Removed the outlet ducts and overall cooling
improved.
So if you do add ducts to get the air from your inlet
to the rear, just try to make certain that the ducts help rather than
hurt.
No calculations, just a gut feeling which of course
could be incorrect.
Ed
Anderson