Subject: Dynamics at high temperature & pressure

From: "Wilson, Bruce" <[email-masked]>
Date: Mon, 19 Aug 1996 17:14:08 -0400

A customer of mine is interested in an understanding of diffusion
(leaking)
of gasses through materials (such as graphite and NBR/Asbestos) at
high pressure (ca 300-1000 psig gas pressure and 1000-10,000 psig 
material pressure).  The application is flange seals.  The problem is
that the experimental results don't agree with chemical intuition 
(what do you mean that helium has a lower leak rate than propane!!!!).
A substantial amount of work has been done that strongly suggests that
the experimental work has been done correctly and can be trusted.
So, we turn to modelling to help understand what's happening.

What leads can folks provide towards how to model things like the
diffusion of He, CH4, propane, and SF6 through something like
graphite, as functions of temperature, compression, and gas pressure,
particularly conditions like the 1000 psi listed above and 200-400 C?

Much of this work is for some standards bodies, so I can discuss the 
matter at more depth (off-line), if anyone is interested.  Thanks.

			Bruce E. Wilson
			Eastman Chemical Company
			[email-masked]