Liquid Controls SP4000 - Manual (Page 67)

64
SP4000 Flow Computer
FLOW INPUT
6.8
FLOW INPUT
(Continued)
The flow computer will then compute the gas expansion factor
(
ε
1
), (Y
1
) using one of the following equation:
Orifice Case:
V-Cone, Venturi, Flow Nozzle, Wedge Case:
Y
1
=
Annubar, Pitot, Target Case;
Y
1
=
ε
1
Gas expansion factor
β
BETA (geometric ratio)
∆
p Differential pressure
κ
Isentropic exponent
p
1
Inlet pressure (absolute)
DP FACTOR
(Continued)
∆
p
27.7 • p
1
R = 1 –
κ − 1
1 −β 4 ) • (
κ
• R
2/
κ
• (1 - R
(κ−1)/κ
)
[(1 −(β
•
4
R )) • (1 - R)]
2/
κ
ε
1
=
ε
1
= 1.0
NOTE: 27.7 is a units conversion constant from the absolute inlet
pressure units to the differential pressure units. (27.7 is for
psia to "H2O, use other units conversions as required.).
∆
p
κ
• p
1
• 27.7
ε
1
= 1 – (0.41 + 0.35
β 4 ) •
[ ]
Y =
1