# Flow Rate of Water Through a Valve

Written by Jerry Ratzlaff. Posted in Fluid Mechanics

## formula

$$p_1 - p_2 < FL^2 \cdot \left( p_1 - FF \cdot p_{av} \right) \rightarrow$$

$$Q_w = 0.0865 \cdot Cv \cdot \sqrt { \frac { p_1 - p_2 } { SG } }$$

$$p_1 - p_2 \ge FL^2 \cdot \left( p_1 - FF \cdot p_{av} \right) \rightarrow$$

$$Q_w = 0.0865 \cdot Cv \cdot FL \cdot \sqrt { \frac { p_1 - FF \cdot p_{av} } { SG } }$$

Where:

$$Q_w$$ = flow rate of water

$$p_1$$ = primary pressure

$$p_2$$ = secondary pressure

$$FL$$ = pressure recovery factor (=0.9)

$$FF$$ = critical pressure ratio factor

$$p_{av}$$ = absolute vapor pressure of the water at inlet temperature

$$SG$$ = specific gravity of water

$$Cv$$ = valve flow coefficient