Orifice Area

• Geometric orifice area (GOA) is the orifice opening
• Effective orifice area (EOA) is the minimal cross-section area of the downstream jet.
• Contraction coefficient (\(C_c\)) is 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 (\(C_d\)) is 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:

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