# Liquid Pressure Recovery Factor

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Liquid pressure recovery factor, abbreviated as $$F_l$$, a dimensionless number, is the ratio of pressure drop that occures between the vena contracta and the upstream pressure.  Depending on valve type, the pressure recovery factor can vary and can usually be found in the valve manufacturers' specs.

## Liquid Pressure Recovery Factor formula

$$\large{ F_l = \sqrt{ \frac{p_1 \;-\; p_2}{p_1 \;-\; p_{vc} } } }$$
Symbol English Metric
$$\large{ F_l }$$ = llquid pressure recovery factor $$\large{dimensionless}$$
$$\large{ p_1 }$$  = upstream pressure, valve inlet $$\large{ \frac{lbf}{in^2}}$$ $$\large{Pa}$$
$$\large{ p_2 }$$  = downstream pressure, valve outlet $$\large{ \frac{lbf}{in^2}}$$ $$\large{Pa}$$
$$\large{ p_{vc} }$$ = pressure in vena contracta $$\large{ \frac{lbf}{in^2}}$$ $$\large{Pa}$$