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Flow-X─ Function Reference
Flow-X General functions - fxGasViscosity_2004
fxGasViscosity_2004
The dynamic viscosity of natural gas is calculated in accordance with a method developed at the
Rostock University in Germany and published in 2004 in the ‘International Journal of the
Thermophysics’. The estimated uncertainty of the calculated viscosity is 0.5% for natural gas (0.3% for
pure methane).
Reference

Viscosity Measurements and Predictions for Natural Gas, P. Schley, M. Jaeschke, C.
Kuchenmeister and E. Vogel, International Journal of Thermophysics, Vol. 25, No. 6,
November 2004 (© 2004)
Boundaries
The limits of the tables are 250 K to 450 K (-24 .. +177 °C) for pressures up to 30 MPa (300 bar).
Function inputs and outputs
Function inputs Remark EU Range Default
Name Optional tag name, tag description and
tag group
Density Density value kg/m3 0..2000 0
Temperature Temperature value °C -200..+400 0
Composition Standard composition as defined in
section 'Standard gas composition’. mol/mol 0..1 0
Function outputs Remark EU Fallback
Status 0: Normal
1: Input argument out of range
2: Calculation error
3: No convergence
4: Mole fractions do not add up to 1.0 +- 0.0001
6: Hardware not supported
Dynamic viscosity Pa.s 0
Range With respect to the combination of temperature and
pressure is:
0: In Range
1: Out of Range 0
Calculations
The calculations are in accordance with the publication, which is based on the following 12
components: methane (+ hydrogen), nitrogen (+ helium + oxygen/argon), carbon dioxide, ethane,
propane, n-butane, ibutane, n-pentane (+ benzene), isentane (+ neopentane), n-hexane (hexanes +
toluene), n-heptane (heptanes), and n-octane (o C10 plus xylenes).
The function uses the ‘Standard gas composition’ as used by most gas property functions. The 22
components of input Composition are lumped to these 12 components as defined in the following
table:
Input component Added to / neglected
Methane Methane
Nitrogen Nitrogen
Carbon Dioxide Carbon Dioxide
Ethane Ethane