Valve Sizing for Liquid
flow rate Formula
| \(\large{ Q = C_v \;\sqrt {\frac {\Delta p} {SG} } }\) |
Where:
\(\large{ Q}\) = flow rate capacity, gpm
\(\large{ C_v}\) = flow coefficient
\(\large{ \Delta p}\) = pressure differential, psi
\(\large{ SG}\) = specific gravity of fluid (water at 60°F = 1.0000)
flow coefficient Formula
| \(\large{ C_v = Q\; \sqrt {\frac{SG} {\Delta p} } }\) |
Where:
\(\large{ C_v}\) = flow coefficient
\(\large{ Q}\) = flow rate capacity, gpm
\(\large{ SG}\) = specific gravity of fluid (water at 60°F = 1.0000)
\(\large{ \Delta p}\) = pressure differential, psi
actual required cv Formula
| \(\large{ C_{vr} = K_v \;C_{v} }\) |
Where:
\(\large{ C_{vr}}\) = corrected sizing coefficient required for viscous applications
\(\large{ K_v}\) = viscosity correction factor
\(\large{ C_v}\) = flow coefficient
maximum flow rate assuming no viscosity correction Formula
| \(\large{ Q_{m} = C_{vr} \; \sqrt{ \frac {\Delta p}{SG } } }\) |
Where:
\(\large{ Q_{m}}\) = maximum flow rate, assuming no viscosity correction required, gpm
\(\large{ C_{vr}}\) = corrected sizing coefficient required for viscous applications
\(\large{ \Delta p}\) = pressure differential, psi
\(\large{ SG}\) = specific gravity of fluid (water at 60°F = 1.0000)
predict actual flow rate Formula
| \(\large{ Q_{p} = \frac {Q_m}{K_v } }\) |
Where:
\(\large{ Q_{p}}\) = predicted flow rate after incorporating viscosity correction, gpm
\(\large{ Q_{m}}\) = maximum flow rate, assuming no viscosity correction required, gpm
\(\large{ K_{v}}\) = viscosity correction factor
corrected size coefficient Formula
| \(\large{ C_{vc} = \frac {C_{vr}} {K_v} }\) |
Where:
\(\large{ C_{vc}}\) = Cv flow coefficient including correction for viscosity
\(\large{ C_{vr}}\) = corrected sizing coefficient required for viscous applications
\(\large{ K_v}\) = viscosity correction factor
predicted pressure drop Formula
| \(\large{ \Delta p_p = SG \; \left( \frac {Q} {C_{vc} } \right)^2 }\) |
Where:
\(\large{ \Delta p_p }\) = predict pressure differential drop for viscous liquids
\(\large{ SG}\) = specific gravity of fluid (water at 60°F = 1.0000
\(\large{ Q}\) = flow rate capacity, gpm
\(\large{ C_{vc}}\) = Cv flow coefficient including correction for viscosity
maximum allowable pressure drop Formula
| \(\large{ \Delta p_a = K_m \;\left( p_i \;-\; r_c \;p_v \right) }\) |
Where:
\(\large{ \Delta p_a }\) = maximum allowable pressure differential for sizing purposes, psi
\(\large{ K_m}\) = valve recovery coefficient from manufacturer’s literature
\(\large{ p_i}\) = body inlet pressure, psia
\(\large{ r_c}\) = critical pressure ratio
\(\large{ p_v}\) = vapor pressure of liquid at body inlet temperature, psia
pressure drop at which cavitation damage will begin Formula
| \(\large{ \Delta p_c = Ca\; \left( p_i \;-\; p_v \right) }\) |
Where:
\(\large{ \Delta p_c }\) = pressure differential drop at which cavitation damage will begin, psi
\(\large{ Ca }\) = dimensionless Cavitation Number index used in determining \(\;\Delta p_c \)
\(\large{ p_i}\) = body inlet pressure, psia
\(\large{ p_v}\) = vapor pressure of liquid at body inlet temperature, psia
Tags: Liquid Valve Sizing