[Vwdiesel] PV=nRT and Hydraulics

[H.Hagar]

----- Original Message -----
From: "Val Christian" <val at swamps.roc.ny.us>
To: <vwdiesel at vwfans.com>
Sent: Wednesday, July 21, 2004 10:24 AM
Subject: PV=nRT and Hydraulics


> You'll recall the ideal gas law, PV=nRT.
>
> You'll also recall that release of gas pressure will cause cooling.  Works
> with a rapidly decompressing gas cylinder, such as an O2 cylinder on a
cutting
> torch.  Or a CO2 fire extinquisher.
>
> n stands for the moles of gas in the system,
>
> R is a constant, which is emphirically derived.  It can be thought of as
> the compressibility of the gas.
>
> I believe the gas law applies to fluids, such as water, hydraulic fluid
> and diesel fuel.  R is just real small.
>
> This would suggest that in theory, the release of pressure on a hydraulic
> line would cause a decrease in temperature.  A quick consult with my
> physical chemistry experts confirms this.  [Liquid exceptions exist, and
> include water (4C to 0C), ATF in some pressure and temperature domains,
> etc.]  The compressibility of simple compounds is found in references such
> as CRC.
>
> Soooo, Lee, in theory, that leakage past the pump should cause COOLING,
> rather than heating.  I rest on my earlier assertion that the heat in
> the pump is primarily from losses due to turbulent flow, fluid friction
> and the like.
>
> Val
>