# 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, a dimensionless number, uses imperial units.  The number of $$\frac{gal}{min}$$ of water at 60°F that will flow through a valve in one minute when the pressure differential across the valve is 1 $$\frac{lbf}{in^2}$$ (psi).

Valve flow factor, abbreviared as $$K_v$$, a dimensionless number, uses imperial units.  The number of $$\frac{L}{min}$$ of water between 5°C - 30°C that will flow through a valve in $$\frac{m^3}{hr}$$ with a pressure drop of 1 bar.

## Valve Flow Coefficient CV / flow Factor KV Formulas

$$\large{ C_v = Q \sqrt{ \frac{SG}{\Delta P} } }$$

$$\large{ K_v = Q \sqrt{ \frac{SG}{\Delta P} } }$$

Symbol English Metric
$$\large{ C_v }$$ = valve flow coefficient $$\large{ dimensionless }$$
$$\large{ K_v }$$ = valve flow factor $$\large{ dimensionless }$$
$$\large{ Q }$$ = valve flow rate $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$
$$\large{ \Delta P }$$ = valve pressure differential $$\large{\frac{lbf}{in^2}}$$ $$\large{\frac{N}{m^2}}$$
$$\large{ SG }$$ = specific gravity of fluid $$\large{ dimensionless }$$