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Re: CO2 systems, supersonic flow...
- To: Aquatic-Plants at actwin_com
- Subject: Re: CO2 systems, supersonic flow...
- From: Paul Sears <psears at nrn1_NRCan.gc.ca>
- Date: Fri, 26 Jan 2001 10:30:45 -0500 (EST)
- In-Reply-To: <200101252043.PAA10680 at actwin_com> from "Aquatic Plants Digest" at Jan 25, 2001 03:43:40 PM
> From: Steve Pushak <teban at powersonic_bc.ca>
> Subject: CO2 valve characteristics at near empty tank
> I do hope this is new information since I have not been
> monitoring the APD closely in recent months. We've had a recent addition
> to the family; young Dylan joined us three weeks ago.
> The first point is relatively minor: fluid flow is never supersonic
> except in the vicinity of aircraft or objects like bullets which are
> travelling through a fluid faster than the speed of sound in that fluid.
I've just been reading Rogers and Mayhew (Engineering Thermodynamics
Work and Heat Transfer) about venturi devices. The reason I have been
reading it had nothing to do the list, but the stuff I found is relevant. Gas
flow can indeed be supersonic in convergent-divergent nozzles. It's
described beginning at the bottom of p 380 in the ancient edition (1967)
I borrowed. I can't say I worry about it overmuch, but it is interesting
stuff (and vital in some instances).
> The second point refers to the so called "empty tank dumping" syndrome.
This _is_ a consequence of regulator design, and was described
here weeks ago.
> Here's my proposed theory:
The point is that dumping was occuring when there was no needle
valve, so it isn't a consequence of valve characteristics.
> Pressure regulators control pressure. Needle valves
> control flow rates at a constant pressure. Both devices are required to
> - -accurately- control flow rates.
Paul Sears Ottawa, Canada