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Constant Area Pneumatic Orifice
Constant Area Pneumatic Orifice
Sharp-edged orifice in pneumatic systems
Library
Pneumatic Elements
Description
The Constant Area Pneumatic Orifice block models the flow rate of an ideal gas through
a sharp-edged orifice.
The flow rate through the orifice is proportional to the orifice area and the pressure
differential across the orifice.
G = C i Ai
p
d
i
È
2g
1 ÍÊ
p
i ÍÁ
g - 1 RTi
ÍË
p
Î
o
i
2 g+
1
g
ˆg
po
˜ - Ê
¯ Ë Á ˆ
˜
pi
¯
˘
˙
˙
˙
˚
where
G
C d
A
p i , p o
γ
R
Mass flow rate
Discharge coefficient, to account for effective loss of area due to orifice shape
Orifice cross-sectional area
Absolute pressures at the orifice inlet and outlet, respectively. The inlet and
outlet change depending on flow direction. For positive flow (G > 0), p i = p A ,
otherwise p i = p B .
The ratio of specific heats at constant pressure and constant volume, c p / c v
Specific gas constant
1-33