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Appendix F Calculations and theory
Page F.2
Also for both methods, the velocity of sound of the calibration gas is calculated by the 795x using the following
equation:
Equation F.1#2: V.O.S. of the calibration gas
Using:
()
3
1
2
1
1
***
ρρρ
DCBAC
KKKKC +
¸
¹
·
¨
©
§
++=
Where:
C
C = V.O.S. of the calibration gas (in m/s)
1
ρ
= line density (un-corrected or temperature corrected)
And:
A
K ,
B
K ,
C
K and
D
K are coefficients from the appropriate ‘K’ column of Table F.1.
The gas flow computer automatically selects the appropriate value for each ‘K’ coefficient by using
this table.
Equation F.1#3a
: V.O.S. of the measured gas (pure or composition) for pressure method
Using:
3
1
6
2
1
5
1
5
0
**
10**
ρρ
ρ
γ
KK
P
C
G
++=
Where:
G
C = V.O.S. of the measured gas (in m/s)
1
ρ
= Line density (un-corrected or temperature corrected)
P
= Line pressure (in barA)
And:
5
K,
5
K and
0
γ are constants that must be SET into the 795x.
For a pure gas, values can be taken from the appropriate columns of table Table F.2
For gas compositions these (pure gas) constants should be modified in proportion to the volumetric
fraction (percentage) of each gas component.