Orifice Area

Written by Jerry Ratzlaff on . Posted in Flow Instrument

  • orifice liquid 1Geometric Orifice Area (GOA)  -  The orifice opening
  • Effective Orifice Area (EOA)  -  The minimal cross-section area of the downstream jet.
  • Contraction Coefficient (\(C_c\))  -  The ratio of the area measured at the vena contracta (EOA), to the area of the orifice (GOA) or \(C_c = \frac{EOA}{GOA}\)
  • Discharge Coefficient (\(C_d\))  -  The ratio of actual flow to ideal flow or \(C_d = \frac{Q_a}{Q_i}\)

 

Orifice Area formula

\(\large{ A_0 =  \frac{ Q  }{ C_d \; \sqrt{ 2 \; g \; H }  }   }\)   

Where:

 Units English Metric
\(\large{ A_o }\) = orifice area \(\large{ in^2 }\) \(\large{ mm^2 }\)
\(\large{ h }\) = orifice center of head \(\large{ in }\) \(\large{ mm }\)
\(\large{ C_d }\) = orifice discharge coefficient \(\large{ dimensionless }\)
\(\large{ Q }\) = orifice flow rate \(\large{\frac{ft^3}{sec}}\) \(\large{\frac{m^3}{s}}\)
\(\large{ G }\) = orifice gravitational constant \(\large{\frac{lbf-ft^2}{lbm^2}}\)  \(\large{\frac{N - m^2}{kg^2}}\) 

Solve for:

\(\large{ C_d =   \frac { Q }  { A_o \; \sqrt { 2 \; G \; h }     }   }\)  

 

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Tags: Area Equations Orifice and Nozzle Equations