# Orifice Area

on . Posted in Flow Instrument

Orifice area refers to the area cross-section of an orifice, which is a small opening or hole through which fluid flows.  The orifice area is an important parameter in fluid dynamics and flow calculations, particularly in applications such as pipes, nozzles, and valves.

• Geometric 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 $$C_c = EOA \;/\; GOA$$
• Discharge Coefficient ($$C_d$$)  -  The ratio of actual flow to ideal flow or $$C_d = Q_a \;/\; Q_i$$

### Orifice Area formula

$$A_0 \;=\; Q \;/\; C_d \; \sqrt{ 2 \; G \; h_c }$$     (Orifice Area)

$$Q \;=\; A_o \; C_d \; \sqrt{ 2 \; G \; h_c }$$

$$C_d \;=\; Q \;/\; A_o \; \sqrt{ 2 \; G \; h_c }$$

$$G \;=\; ( Q \;/\; C_d \; A_o )^2 \;/\; 2 \; h_c$$

$$h_c \;=\; ( Q \;/\; A_o \; C_d )^2 \;/\; 2 \; G$$

Symbol English Metric
$$A_o$$ = orifice area  $$in^2$$ $$mm^2$$
$$Q$$ = orifice flow rate $$ft^3 \;/\; sec$$ $$m^3 \;/\; s$$
$$C_d$$ = orifice discharge coefficient $$dimensionless$$
$$G$$ = orifice gravitational constant $$lbf-ft^2 \;/\; lbm^2$$  $$N - m^2 \;/\; kg^2$$
$$h_c$$ = orifice center of head $$in$$ $$mm$$