GPA 2145 / GPA 2172 / ISO 6976
Total: 99.00 mol%
When enabled, composition is proportionally adjusted to sum to exactly 100 mol%.
Understand combustion chemistry, GPA standards, gas quality specifications, and Wobbe Index significance
The heating value of natural gas is the amount of energy released when the gas is burned completely. Gross heating value (HHV) includes the latent heat of water vapor condensation, while net heating value (LHV) excludes it. Typical pipeline-quality natural gas has an HHV of 950-1150 Btu/scf depending on composition.
The Wobbe Index equals the gross heating value divided by the square root of the specific gravity (WI = HHV / sqrt(SG)). It is the key indicator of gas interchangeability for burner applications. Gases with similar Wobbe Indices produce similar heat release rates when burned at the same supply pressure, regardless of their individual compositions.
Heating value is calculated as the mole-fraction-weighted sum of individual component heating values: HHV_mix = sum(yi x HHVi). Component heating values are published in GPA 2145 (Table of Physical Constants of Paraffin Hydrocarbons and Other Components of Natural Gas) at standard conditions of 60 deg F and 14.696 psia.
HHV (Higher Heating Value) assumes all water produced by combustion condenses to liquid, recovering latent heat. LHV (Lower Heating Value) assumes water remains as vapor. For methane, HHV is 1010.0 Btu/scf vs LHV of 909.4 Btu/scf, a difference of about 10%. US gas industry uses HHV for custody transfer; European practice often uses LHV.