how to estimate gas flow rate thru a needle valve?
how to estimate gas flow rate thru a needle valve?
(OP)
Hi,
I wonder whether there is a good equation to estimate gas (say, air) flow rate through a needle valve?
Right now I know the pipe diameter (1/4") and the outflow pressure (20 psi).
Thanks.
I wonder whether there is a good equation to estimate gas (say, air) flow rate through a needle valve?
Right now I know the pipe diameter (1/4") and the outflow pressure (20 psi).
Thanks.





RE: how to estimate gas flow rate thru a needle valve?
- VOGT has one for their manual valves
- Fisher and other control valve manufacturers would have flow equations for their valves (For Fisher, you'd have to assume a C1 factor to convert Cv to Cg but Cg is 'likely' about 30*Cv). The flow rates won't be exactly the same but they'll be in the same ball park.
Your needle valve vendor might even have an equation for you. Now, if you want the flow with the valve only partially open, your vendor is going to have to give you some indication of the needle valve's characteristic curve (linear, quick opening, equal percentage, etc).
If the 1/4" piping connected to the valve has a significant pressure drop, you'll need to include its effect as well to estimate the flow rate.
RE: how to estimate gas flow rate thru a needle valve?
you can always estimate an upper bound