Joe,

    I think you have to define your operating conditions before you could
begin to determine an optimum volume.  High Power and low airspeeds would
perhaps imply need for large, thin radiators due to the lower dynamic
pressure at those speeds.  High power and high airspeeds might indicate
small, thick radiators would work fine due to the higher dynamic pressure.
The lower the power setting in any operating regime the less the cooling
required. More Power = More Waste Heat = More Cooling required.

  Cruise power settings are normally a bit lower than take off, so at cruise
the cooling problem becomes a bit easier.  But, like most things in the
flying game, its a matter of compromise and trying to find the best
compromise for your selected operating regime.

  In other words, there is no best single answer - it all depends.  I think
we have enough folks flying RV aircraft with two evaporator cores to
indicate that somewhere around 650 in^3 of core does the job adequately for
their typical operating regime.  However, we still encounter operating
regimes such has high power climbout on a hot day that will  temporarily
exceed even our cores cooling capabilities until power is reduced or greater
airspeed is attained.


Ed


Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
----- Original Message -----
From: "Joseph Berki" <joseph.berki@grc.nasa.gov>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, November 19, 2003 12:16 PM
Subject: [FlyRotary] Re: radiator size


> I would like to know what the optimum volume is.  It is interesting to
note
> that Tracy is using two cores and had a duct problem with one and had
> sufficient cooling.  See cooling test at his web site. I think he changed
> the inlet and improved the cooling.  The type of AC fast vs slow is
> important (high power at low speed)  like climb out .  If we optimize the
> inlet how small could the rad be?  I think a pusher would be a perfect bed
> for a long duct.  Worse case would be ground cooling.
>
>
> At 11:01 AM 11/19/2003 -0600, David Carter wrote:
> >408 cubic inches is short of the 600 to 750 that are being used
> >successfully.  I posted my a/c core sizes yesterday - 336.65 cubic inches
of
> >fin area X 2 = 673 cub inches - that will be enough.
> >
> >David Carter
> >
> >----- Original Message -----
> >From: "sqpilot@earthlink" <sqpilot@earthlink.net>
> >To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> >Sent: Wednesday, November 19, 2003 10:55 AM
> >Subject: [FlyRotary] radiator
> >
> >
> >Hi, fellow rotary enthusiasts.....I'm getting ready to order a radiator
for
> >my 13b powered SQ2000 canard pusher.  I talked to Al Wick, and he has a
160
> >hp Subaru powered Cozy and is cooling it very well with a radiator that
is
> >17" x 7.25" x 3" deep.  Any idea if that size might also cool a rotary?
How
> >does that seem to compare with two GM evaporator cores?  I was told that
if
> >I can increase the height to 8 inches instead of 7.25, they can put two
fans
> >on it, as well as the built-in Meziere EWP. I can work with the
additional
> >height of 8 inches.  Just don't want to spend $1100.00 for too small a
> >radiator. If 17x8x3 equates to approximately the same size as two
evaporator
> >cores like Ed Anderson is using, I should be OK. If anyone can compare
the
> >square inches of the two, I would sure appreciate it.  Thanks in advance
for
> >any and all efforts and recommendations.  Paul Conner
> >
> >
> >
> > >>  Homepage:  http://www.flyrotary.com/
> > >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>
>
>
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