Flow-X─ Function Reference
4-65
Flow-X General functions - fxAGA5_C
fxAGA5_C
The AGA 5 standard defines methods to calculate the mass and volume based calorific values at 60°F
and 14.73 psia for a natural gas based on known molar fractions of the non-hydrocarbon gas
components.
Compliance
A.G.A. Transmission Measurement Committee Report No. 5 (Fuel gas Energy Metering) 1981
A.G.A. Transmission Measurement Committee Report No. 5 (Fuel gas Energy Metering) 1996
(Reprinted 1999)
Function inputs
Remark
EU
SW tag
Range
Default
Name
Optional tag name, tag
description and tag group
Composition
Standard composition as
defined in section 'Standard
gas composition.
Only the following components
are considered by the
calculation:
N2
Nitrogen
CO2
Carbon dioxide
H2O
Water
H2S
Hydrogen sulfide
H2
Hydrogen
CO
Carbon monoxide
O2
Oxygen
He
Helium
Sum of these fractions may not
exceed 1
molar
fraction
COMP
0..1
0
Specific Gravity
Molar Mass Ratio, i.e. ratio of
the molar mass of the gas and
of the molar mass of air
(specified in AGA-5 as 28.9644
kg/kmol (lbm/lbmol))
-
SG
0..1
0
Function outputs
Remark
EU
SW tag
Alarm
Fallback
Status
0: Normal
1: Input argument out of
range
2: Calculation error
STS
FIOOR
CALCERR
Calorific value
mass
Mass based calorific value
Btu/lbm
CV_MASS
0
Calorific value
volume
Volume calorific value at
60°F and 14.73 psia
Btu/scf
CV_VOL
0
Calculations
The Energy to Mass ratio is calculated according to Section III of the standard, which contains the
calculation procedure for the gas mass to energy conversion. The equations based on the 'by volume'
fractional values are used (and not the equations based on the 'by weight' values).
The Energy to Volume ratio is calculated according to Section II of the standard, which contains the
calculation procedure for the gas volume to energy conversion.
Summary of Contents for flow-x
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