flow through a control valve

[minty]

When considering flow through a control valve, how does the continuity equation apply?

A control valve is used to regulate or restrict a flowrate. However, according to Q=AV or m=rho AV, a change in area (closing the valve) will produce a change (increase) in velocity to maintain the flowrate. So, one could assume that by partially closing a valve, you can still maintain your flowrate but the fluid would have a faster velocity.

At what point does this principle no longer apply (i.e. when is flow restricted)? Does choked flow have to occur before flow through the valve can be regulated?

Thanks.

 

[gerhardl]

One of the better explanations I have found:

Ref link:

http://books.google.no/books?id=LuU...esult&ct=result&resnum=1#v=onepage&q=&f=false

(Flow of industrial fluids: theory and equations Av Raymond Mulley, ISA--The Instrumentation, Systems, and Automation Society )

 

[minty]

thanks Gerhardl.