REFLECTOR: cooling requirements

Dave Bertram v350tx at comcast.net
Tue Oct 25 17:37:30 CDT 2005


I will have to check my fuel flow as I only have horsepower and torque at
RPM figures.  No temp factor.  Dave Bertram 
 
-------Original Message-------
 
From: Velocity Aircraft Owners and Builders list
Date: 10/20/05 00:37:08
To: reflector
Subject: REFLECTOR: cooling requirements
 
I am running a 383ci v-8 making up to 425hp.  I cool it with a belly scoop
the inlet of which is 45sq.in..  My radiator is approximately 21x16x3.5 in..
 My max temp (water)  on take-off and climb is about 220 on a 95 degree day.
 After power reduction at cruise it drops to around 180 degrees.  
Dave Bertram
V350TX 
 
Interesting data point, Dave.  The relatively high expansion ratio you have
from inlet to radiator makes good use of the 3.5” thick core.  The 45 sq. in
 inlet area at 100% effective gives 3600 cfm at 120 kts, and the specific
heat (heat capacity, if you prefer) of air gives 72 BTU/degree F of air temp
rise through the rad.  If we are optimistic and assume a 100 F air temp rise
 then that is good for about 250 hp engine output (steady sate, extended
time).
 
One of the unknowns is the effect of the heat capacity of the engine block
and the coolant as its temperature rises under climb conditions.  If you
start your roll at, say 180 F, or less; that big block absorbs quite a bit
of heat as the coolant heats up to 220 F, so allows higher power for a short
period of time.  And, generally, as you climb the air temp drops, which
helps.  Do you have a measure of actual hp output typical of climb
conditions?  Or if you have the fuel burn, we can compute an estimate from
that.
 
Al
 
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