Natural_Gas and Natural_Gas2
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
There are two substances that allow you to adjust the composition of natural gas. The composition of the substance Natural_Gas can be changed by editing the NaturalGasInfo.txt file contained in the EES\USERLIB\EES_System folder. The composition of the substance Natural_Gas2 can be set using the $Natural_Gas2 directive, as shown below:
$Natural_Gas2 CH4 0.9512332 C2H6 0.01835537 C3H8 0.00237727 C4H10 0.000561767 C5H12 0.0002500951 C6H14 0.0007896907 N2 0.00088950245 CO2 0.025543105
Natural_Gas and Natural_Gas2 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 and Natural_Gas2 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 and Natural_Gas2 can be used with the Combustor functions in the Component Library.
Air, Natural_Gas, Natural_Gas2, the CombustionGas substances and the custom ideal gas mixtures IGMixture1 through IGMixture6 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).
See also: $IGMixture