×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

how to estimate gas flow rate thru a needle valve?

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.

RE: how to estimate gas flow rate thru a needle valve?

I'd talk to the vendor and see if they have a Cv value for the needle valve because you need that.  Once you have that, you can use a variety of methods:

- 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 needle valve catalog as a flow equation and a list of valve coefficient data that will solve your problem.

you can always estimate an upper bound

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources