Flow-X─ Function Reference
4-227
Flow-X General functions - fxISO5167_Orifice
Density correction
When input 'Density exponent' = 0, then the following isentropic corrections are applied
(depending on the type of Density Correction)
1
2
1
2
1
p
p
1
3
1
3
1
p
p
Else the value of input 'Density Exponent' is used
DE
K
p
p
2
1
2
1
DE
K
p
p
3
1
3
1
Where:
1
Upstream density
[kg/m3]
2
Density at the downstream tapping
[kg/m3]
3
Density at the fully recovered downstream pressure
[kg/m3]
p
1
Upstream pressure
[bar(a)]
p
2
Pressure at the downstream tapping
[bar(a)]
p
3
Fully recovered downstream pressure
[bar(a)]
Isentropic exponent
[-]
K
DE
Density exponent
[-]
Note: In March 2007 the British DTI (Department of Trade and Industry) has recommended that the
density correction method should not be based on isentropic expansion but on isenthalpic expansion
instead.
The correction assumes that the density is measured at p
2
(downstream pressure tapping pressure) and
t
3
(downstream recovered temperature). For this situation the following density correction is defined:
)
,
(
)
,
(
1
1
1
2
3
2
3
1
1
t
p
Z
t
p
t
p
Z
t
p
M
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