Flow through 3/4 open valve from High pressure steam line

[vester99]

If a 3/4" valve on a large high pressure steam header were opened. What would be the maximum amount of steam flow through this valve? Can anyone tell me what equation I could you use to calculate this.

Thanks

 

[Latexman]

First pass estimate:

1. Calculate sonic velocity of your steam.

2. Multiply this velocity times the flow area of your 3/4" valve to get the maximum volumtric flow rate.

Good luck,
Latexman

 

[sailoday28]

Latexman (Chemical)For choked flow your estimate should be for mass flow.

Regards

 

[sailoday28]

Sorry Latexman. Your are correct for the volumetric flow. Area*velocity.

Regards

 

[JimCasey]

It's probably worth knowing whether the valve is a globe valve (Cv around 5) or a ball valve ( Cv around 12 ) or whatever other type it might be. If the valve is on a high pressure steam header it WILL have choked flow thru the vena contracta at any valve position, and the downstream velocity will be sonic before you get the valve much more than cracked. In the Downstream piping will be a series of shock waves and the flow will be at some pressure less than the inlet to the valve and greater than the discharge pressure of the system, unless you get so much flow thru the valve that the downstream piping completely chokes. Choked mass flow at 20 psi is a lot less than choked mass flow at 200 psi. Both happen.