# Orifice Flow Rate

Written by Jerry Ratzlaff on . Posted in Flow Instrument

Orifice flow rate is the amount of fluid that flows in a given time.

## Formulas that use Orifice Flow Rate

 $$\large{ Q = C_d \; A_o \; \sqrt { 2 \; G \; h } }$$ $$\large{ Q = C_d \; A_o \; Y \;\sqrt { \frac{ 2 \; \Delta p }{ \rho \; \left( 1 \;-\; \beta^4 \right) } } }$$ (horizontal orifice and nozzle) $$\large{ Q = C_d \; A_o \; Y \;\sqrt { \frac{ 2 \; g \; \Delta h }{ \left( 1 \;-\; \beta^4 \right) } } }$$ (horizontal orifice and nozzle) $$\large{ Q = C_d \; A_o \; Y \;\sqrt { \frac{ 2 \; \left( \Delta p \;+\; \rho \; g \; \Delta y \right) }{ \rho \; \left( 1 \;-\; \beta^4 \right) } } }$$ (vertical orifice and nozzle) $$\large{ Q = C_d \; A_o \; Y \;\sqrt { \frac{ 2 \; g \; \left( \Delta h \;+\; \Delta y \right) }{ \left( 1 \;-\; \beta^4 \right) } } }$$ (vertical orifice and nozzle)

### Where:

$$\large{ Q }$$ = flow rate

$$\large{ h }$$ = center of head

$$\large{ \rho }$$  (Greek symbol rho) = density

$$\large{ C_d }$$ = discharge coefficient

$$\large{ \Delta y }$$ = elevation change ( $$\Delta y = y_1 - y_2$$ )

$$\large{ Y }$$ = expansion coefficient (Y = 1 for incompressible flow)

$$\large{ g }$$ = gravitational acceleration

$$\large{ G }$$ = gravitational constant

$$\large{ \Delta h }$$ = head loss

$$\large{ A_o }$$ = orifice area (GOA)

$$\large{ p }$$ = pressure

$$\large{ \Delta p }$$ = pressure differential ( $$\Delta p = p_2 - p_1$$ )

$$\large{ \beta }$$  (Greek symbol beta) = ratio of pipe inside diameter to orifice diameter

### Solve for:

$$\large{ Y = \frac{ C_{d,c} }{ C_{d,i} } }$$

$$\large{ C_{d,c} }$$ = discharge coefficient compressible fluid

$$\large{ C_{d,i} }$$ = discharge coefficient incompressible fluid

$$\large{ \beta }$$  (Greek symbol beta) = $$\frac{d_0}{d_u}$$

$$\large{ d_o }$$ = orifice or nozzle diameter

$$\large{ d_u }$$ = upstream pipe inside diameter from orifice or nozzle