Contents - Index



Natural_Gas is an ideal gas mixture.  By default, the mixture consists of the following gases.


Gas Mole Fraction

CH4 0.9512332

C2H6 0.01835537

C3H8 0.00237727

C4H10 0.000561767

C5H12 0.0002500951

C6H14 0.0007896907

N2 0.00088950245

CO2 0.025543105


However, the composition of the mixture can be changed by editing the NaturalGasInfo.txt file contained in the EES\USERLIB\EES_System folder.


Natural_Gas can be used just like any of the built-in ideal gas substances.  All of the functions that are available for ideal gases, e.g., CH4, are available for Natural_Gas as well, including Viscosity and Conductivity.  The viscosity of the gas mixture determined using the Wilke Approximation as described in Eq. 9-5.2 of Reid, Prausnitz, and Sherwood.  The thermal conductivity is determined using the Mason and Saxena modification, as described in Eq. 10-6.2. of Reid, Prausnitz, and Sherwood.  The heating values are determined as a mole-fraction average of the gases in the mixture.


Natural_Gas can be used with the Combustor functions in the Component Library.


Air and Natural_Gas are the only substances in the EES database that do not follow the ideal gas name convention.  All other substances are modeled as a real substance if the fluid name is spelled out, (e.g., Nitrogen) and as an ideal gas if the fluid name is chemical formula (e.g., N2).  Air and Natural_Gase are modeled as an ideal gas mixture.



Fluid Property Information