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Mike That was counterintuitive, but I think I actually learned something today. I had incorrectly surmised that at depth the increased pressure on the downstream side would slow the flow of gas. I will take a guess that at some point where the tank pressure and the ambient pressure are not so hugely different that it would slow the flow. However, the point I learned is that the velocity of gas flow through a restriction is relatively constant (speed of sound) and that gas loss, in practical terms, is proportional to density on the downstream side. So my experiment did not prove anything valid for diving. I will repeat it underwater some day and take samples at a few depths. Cheers David Pearson Ottawa, Ontario djpearson@sy*.ca* > -----Original Message----- > From: Rodriguez [mailto:mikey@ma*.co*] > Sent: June 22, 2001 4:44 PM > To: FlTechDiver@mikey.net; techdiver@aquanaut.com > Subject: Blown Hose > > > > >>day and turned on the tank to see what would happen. At a > starting pressure > >of 3000PSI on an AL63 I left the valve full open for 1 minute. When I > >checked the pressure after, it had only dropped 400PSI. > > >At 330 feet (10 AtA more than at the surface), that same test would > >drain ~4000 PSI in one minute. The small fixed orifice of the high > >pressure port helps mitigate the severity of the problem, but at > >300+ feet, any blown hose is a *very* big deal. > > It seems things are never as simple as they seem. It turns out that: > > "When gas flows from a vessel through an orifice to another vessel, it is > well known that as the downstream pressure is reduced, the mass > flowrate steadily increases until the velocity at the orifice > reaches sonic > velocity. If the downstream pressure is further reduced, the mass flow is > unaffected and the excess pressure is dissipated in shock waves downstream > of the orifice." > > Take a look at: > > http://www.optimal-systems.demon.co.uk/appendix-e.htm > > and > > http://www.optimal-systems.demon.co.uk/sonic-velocity.htm > > > -Mike Rodriguez > <mikey@mi*.ne*> > http://www.mikey.net/scuba > Pn(x) = (1/(2^n)n!)[d/dx]^n(x^2 - 1)^n > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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