Water Flow Rate Through a Valve

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Water Flow Rate Through a Valve formula

 $$\large{ p_1 - p_2 < F_l^2 \left( p_1 - F_f \; p_{av} \right) \rightarrow }$$ (Eq. 1)  $$\large{ Q_w = C_v \; \sqrt { \frac{ p_1 \;-\; p_2 }{ SG } } }$$ $$\large{ p_1 - p_2 \ge F_l^2 \left( p_1 - F_f \; p_{av} \right) \rightarrow }$$ (Eq. 2)  $$\large{ Q_w = C_v \; F_l \; \sqrt { \frac{ p_1 \;-\; F_f \; p_{av} }{ SG } } }$$

Where:

 Units English Metric $$\large{ Q_w }$$ = water flow rate $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$ $$\large{ p_{av} }$$ = absolute vapor pressure of the water at inlet temperature $$\large{\frac{lbf}{in^2}}$$ $$\large{\frac{kg}{m-s^2}}$$ $$\large{ F_f }$$ = liquid critical pressure ratio factor $$\large{dimensionless}$$ $$\large{ p_1 }$$ = primary pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$ $$\large{ p_2 }$$ = secondary pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$ $$\large{ F_l }$$ = id pressure recovery factor (= 0.9) $$\large{dimensionless}$$ $$\large{ C_v }$$ = valve flow coefficient $$\large{dimensionless}$$ $$\large{ SG }$$ = specific gravity of water $$\large{dimensionless}$$