Aftercooler Gains

[BamaInstrument]

Yep, now I see where you got the number.  I have converted from BTU to watts
to horsepower below.

Hey, a factor of 60 is not too good, thanks for the help.

To continue the number crunching,  57,542 BTU per hour is  between 22 and 23
horsepower.  (See below) To follow that line of reasoning then a 5,000 BTU
AC would cool enough air for a 39 horse engine if the cooling were 80
degrees F.  (or 78 degrees F in a 78 hp engine...etc.)

Calculation:

Given : 1,000 BTU/hr = .293KW  http://www.energyadvocate.com/fw34.htm

Given : 0.746KW = 1Hp  from memory

Given : 57.5KBTU cooling needed as calculated below

(57.5KBTU)  *  (0.293) /  (.746)


The guys that store the heat only have to store heat for, say, a 10 second
run.  That is a total of 360 BTU of heat (cool) storage for a 450 horse
engine, for 10 seconds.  Do you get the same result?  If so then the 5000
BTU Air Conditioner can cool for 4.32 minutes to give a 10 second run.
(Assuming that the cooler isn't used at low speed or idle)  Are we talking
red light to red light?  I think that this is probably adequate for street
racers.  For folks such as me that are looking for a continuous load, I
think that the device is not that useful.

dh

----- Original Message -----
From: "Greg Hermann" <bearbvd at cmn.net>
To: <diy_efi at diy-efi.org>; <gmecm at diy-efi.org>
Sent: Tuesday, April 17, 2001 7:07 PM
Subject: Re: Aftercooler Gains


> 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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