# Water Flow Rate Through a Valve

on . Posted in Fluid Dynamics

### Water Flow Rate Through a Valve formula

$$Q_w = C_v \; \sqrt { p_1 - p_2 \;/\; SG }$$
Symbol English Metric
$$Q_w$$ = water flow rate $$ft^3\;/\;sec$$ $$m^3\;/\;s$$
$$p_1$$ = primary pressure $$lbf\;/\;in^2$$ $$Pa$$
$$p_2$$ = secondary pressure $$lbf\;/\;in^2$$ $$Pa$$
$$C_v$$ = valve flow coefficient $$dimensionless$$
$$SG$$ = specific gravity of water $$dimensionless$$

### Water Flow Rate Through a Valve formula

$$Q_w = C_v \; F_l \; \sqrt { p_1 \;-\; F_f \; p_{av} \;/\; SG }$$
Symbol English Metric
$$Q_w$$ = water flow rate $$ft^3\;/\;sec$$ $$m^3\;/\;s$$
$$p_{av}$$ = absolute vapor pressure of the water at inlet temperature $$lbf\;/\;in^2$$ $$Pa$$
$$F_f$$ = liquid critical pressure ratio factor $$dimensionless$$
$$p_1$$ = primary pressure $$lbf\;/\;in^2$$ $$Pa$$
$$F_l$$ = id pressure recovery factor (= 0.9) $$dimensionless$$
$$C_v$$ = valve flow coefficient $$dimensionless$$
$$SG$$ = specific gravity of water $$dimensionless$$