# Valve Flow Coefficient Cv / Kv

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Valve flow coefficient, abbreviared as $$C_v$$, also called valve sizing coefficient, is the number of US gallons of water at 60°F that will flow throuhg a valve in one minute when the pressure differential across the valve is one pound per square inch (psi).

### Valve Flow Coefficient Cv / Kv Formula

(Eq. 1)  $$\large{ C_v = Q \sqrt{ \frac{SG}{\Delta P} } }$$

(Eq. 2)  $$\large{ Q = C_v \sqrt{ \frac{\Delta P}{SG} } }$$

(Eq. 3)  $$\large{ \Delta P = SG \left( \frac{Q}{C_v} \right) }$$

(Eq. 4)  $$\large{ K_v = Q \sqrt{ \frac{SG}{\Delta P} } }$$

(Eq. 5)  $$\large{ Q = K_v \sqrt{ \frac{\Delta P}{SG} } }$$

(Eq. 6)  $$\large{ \Delta P = SG \left( \frac{Q}{K_v} \right) }$$

Where:

$$\large{ C_v }$$ = valve flow coefficient (US units)

$$\large{ K_v }$$ = valve flow coefficient (SI units)

$$\large{ Q }$$ = valve flow rate

$$\large{ \Delta P }$$ = valve pressure differential

$$\large{ SG }$$ = fluid specific gravity