Flow Coefficient Value (Cv) Formula

[WheyProtein]

Would anybody happen to know the formula to calculate the flow coefficient (Cv) of a valve in metric units? I stumbled onto an online calculator but am unsure the formula which it uses. If anyone could help me out I would appreciate it greatly. Cheers!

https://www.swagelok.com/en/toolbox/cv-calculator

 

[katmar]

Here are some notes from my files for the basic definition. If you need extensions for compressible flow you can use the same method.

Definition of Cv is
Cv = Q x √ (ρ / ( ΔP x 62.4 ))

where
Q is in USgpm
ρ is in lb/ft³
ΔP is in psi

Now define
Q’ is in m³/s
ρ’ is in kg/m³
ΔP’ is in kPa

Cv = Q’ x 15850 x √ ((ρ’ x 0.0624) / ( ΔP’ x 0.145 x 62.4 ))
Cv = Q’ x 15850 x √ ( 0.00690 x ρ’ / ΔP’ )
Cv = 1316 x Q’ x √ ( ρ’ / ΔP’ )


Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[LittleInch]

I find engineering toolbox very useful. And scroll down a bit.

https://www.engineeringtoolbox.com/flow-coefficients-d_277.html

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

 

[jari001]

Below is the bulletin from Swagelok that I believe is the basis of their online calculator:

https://www.swagelok.com/downloads/webcatalogs/EN/MS-06-84.PDF

On page 5 is the table of constants in their equation and what combination of units are meant for which constant.