Choked Flow

[engpes]

I have an natural gas application that appeared to be very simple, but am having trouble gathering information from the manufacturer. I have an existing in service adjustable choke that that I know the orifice size for, but cannot find the flow coefficient from the manufacturer.

This would be a very simple problem, but I cannot seem to obtain the flow coefficient. The choke is a 2" adjustable choke with a 1.0" orifice. I want to determine the max flow in the fully open position (1440 psi upstream / atm downstream).

Is it possible to calculate the flow coefficient from the orifice diameter in an adjustable choke? I expect that the choke geometry / makeup would come into play as well?

I always thought the flow coefficient was determined from field studies of a specific instrument, but is there an accurate way to analytically calculate the flow coefficient (ie flow rate) from the orifice diameter?

My initial feelings are no, but was curious to see if anyone has had any success with this before?

 

[LittleInch]

Try this FAQ -

http://www.eng-tips.com/faqs.cfm?fid=1201

There may be some other losses within the choke itself, but probably relatively minor compared to the main orifice.

I'm surprised you can't find out the info or don't have it in the original valve data sheet??

What type of "choke" is this - they come in many shapes and sizes.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[engpes]

Thank you LittleInch. This was an existing choke and I was later able to chase down the manufacturer and acquire the Cv. Thanks for your help.