Flow-X─ Function Reference
4-279
Flow-X General functions - fxSGERG_M
fxSGERG_M
Description
This function performs the SGERG calculation in metric units.
The Standard (or Simplified) GERG TM5 1991 Virial Equation (SGERG or SGERG-88) has defines a
method to calculate the Compressibility Factor (Z) for Natural Gases. The SGERG calculation is
equivalent to the AGA8 Gross Characterisation Method, however .the results are slightly different
Instead of the full compositional analysis (as used by the AGA 8 Detailed Characterization method), the
Gross Characterisation Method (SGERG) uses a restricted set of input variables for its equation,
comprising Relative Density, Superior Calorific Value, Carbon Dioxide and Nitrogen together with
pressure and temperature.
Compliance
GERG Technical Monograph 5, Standard GERG Virial Equation, 1991
Boundaries
The standard specifies a maximum uncertainty of the compressibility factor of 0.1% provided the inputs
lie in the following range.
Pressure
0 .. 120
bar(a)
Temperature
265..335
K
Gross heating value
19 .. 48
MJ/m3
Relative density
0.55 .. 0.90
-
Carbon dioxide
0.00 .. 0.30
mol/mol
Nitrogen
0.00 .. 0.50
mol/mol
Hydrogen
0.00 .. 0.10
mol/mol
Function inputs and outputs
Function inputs
Remark
EU
Range
Default
Name
Optional tag name, tag description and
tag group
Pressure
Observed pressure
bar(a)
0..2000
1.01325
Temperature
Observed temperature
°C
-200..300
0
Relative density
At the reference conditions according
to input 'Reference conditions'
-
0..2
0
Gross heating value
At the combustion and reference
conditions according to input
'Reference conditions'
MJ/m3
0..100
0
Nitrogen
mol/mol
0..1
0
Carbon dioxide
mol/mol
0..1
0
Hydrogen
mol/mol
0..1
0
Method
Calculation method:
1: All inputs are known
2: Unknown Nitrogen mole fraction
3: Unknown Carbon Dioxide mole
fraction
4: Unknown Gross Heating Value
5: Unknown Relative Density
-
0
Reference
conditions
Reference conditions that correspond
with the values of inputs 'Relative
density' and 'Gross heating value'.
Combustion temp. / metering temp. /
pressure
1: 25°C / 0°C / 1.01325 bar(a)
1
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