Turbo Bypass
goflo at pacbell.net
goflo at pacbell.net
Sun Aug 23 06:14:42 GMT 1998
Zack wrote:
Cartech, for example, makes
> intercoolers for GN's with the following specs:
>
> "The intercooler has less than 0.6 psi
> pressure drop across the core at 17 psi with an efficiency rating of
> 90%"
> Now, even the most spectacularly efficient turbocharger is going to
> have an outlet temperature somewhere in the vicinity of 300 degrees F
> when running 17 psi of boost if the ambient air temp is 80 degrees.
> This 90% efficient intercooler will reduce that temperature back to
> 102 F at it's outlet. In absolute temperature, the inlet is at 792
> degrees Rankine and the outlet is at 594... the absolute outlet temp
> is ~75% of the inlet temp. Blindly apply PV=nRT to this situation,
> given that the inlet pressure (absolute) is 31.7 PSI, and you'll come
> to the conclusion that the minimum pressure drop across the
> intercooler must be 7.9 PSI.
> That is not just a little wrong, that's -totally- wrong. Off by a
> more than factor of ten. QED.
I'm under the impression that the figure of .6 psi represents the static
restriction of the device. i.e. (17-.6)/17 ~ 96% volumetric efficiency.
Regards, Jack
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