Aftercooler Gains

[Greg Hermann]

At 4:57 PM 4/17/01, BamaInstrument wrote:
>I'm not so much interested in high performance in a drag race as having
>consistent high power for years.  I look at the intercooler as a device
>which allows me to run universally available gasoline with a turbo engine.
>So I'm interested.
>
>Q.  Where do you get the 20HP loss?  1 BTU is one pound of water 1 degree F
>in one Hour

NO.
1 BTU is the amount of heat required to warm (or cool) 1 lb of water 1
degree F. Period, no time involved.

and the small auto Air Conditioners produce 5,000 BTU.

An auto AC unit produces a cooling effect of about 5000 BTU PER HOUR. (Note
that this is a RATE.)

 That is
>83 Lbs of water or about 10 CuFt of water per minute 1 degree F.

Per HOUR, not per MINUTE!!!! You just threw yourself off by a factor of SIXTY!!

 I'm having
>trouble converting that into CFM/degree F/min. But I believe that we have
>about 18,000 CuFt of air at 1 degree C/min or 500 CFM at 36 Degrees F.  So
>if the air is intercooled to, say, 120 degrees F then the AC cooler would
>take it down to 94 degrees F.

Nope!

You need about 1.5 CFM (Cubic Feet per Minute) of air flow (AT STANDARD
ATMOSPHERIC CONDITONS) through an engine in order to make 1 HP of output.

A cubic foot of air weighs .074 lbs. at std. atm. conditions--so this means
you need .111 lbs. of air per minute , or 6.66 lbs. per hour, of air
rflowing through the engine per HP of output--

The specific heat of air is .24 BTU/lb.-degree F. (meaning it takes a fuzz
less than 1/4 as much heat to warm (or cool) a pound of air 1 degree F as
it does for water.

OK--now say you have a 450 HP engine, and want to cool the compressed air
coming out of the supercharger (or turbocharger) from 200 F to 120 F. 450
HP times 6.66 lbs of air per hour per HP means you must cool  2997 lbs of
air per hour, and must cool it 80 degrees. So, 2997 times 80 times .24 (the
specific heat of air) is equal to
57,542 BTU's of cooling effect needed, per hour. This is about ELEVEN TIMES
the amount of chilling effect that little automotive AC unit is able to
make!!!

No do you see where I got the 20 HP number??

Greg
>
>There is a good chance that my math is wrong, please help!
>
>dh



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