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Cv for your micro-metering valve

At 03:48 PM 5/9/99 -0400, Steve Pushak wrote:
>The less expensive valves such as the ARO NO1 (part # 104104-NO1) have a
>full open valve coefficient Cv of about 0.04 whereas the Nupro S series
>has a Cv of about 0.004

Here is the sad part.   If your input pressure is 5psi (go below this and
you risk serious instability problems) and your output is 1.5 psi (36" of
water) and your temperature is 70F, then the Cv you need is .000007 for one
liter per day.   If you want one 2mm bubble of CO2 per second, that is
about 4mm3/sec or 15cm3/hour or .4L/day or a Cv of about .000003

That is a long way from .004, or the Hoke value of .0008 which still
doesn't hack it.

This is why I advocate high pressure systems, they work.

Dave Gomberg, San Francisco            mailto:gomberg at wcf_com