Overview
ISO/TR 29922:2017 is a technical report that provides supporting information for the calculation of physical properties of natural gas as specified in ISO 6976:2016. Rather than adding new normative requirements, this TR acts as a repository of technical detail, justification, worked examples and uncertainty discussion for the calculational methods used to determine calorific values, enthalpy and related physical properties of natural gas. Clauses are largely self-contained and intended to support implementers, metrologists and developers of calculation software.
Key topics
The report covers a wide set of technical topics that expand on ISO 6976 methodology, including:
- Enthalpy of combustion (ideal gas) and its temperature dependence, plus illustrative examples and uncertainty analysis.
- Real-gas (non-ideality) effects: pressure dependence of enthalpy, enthalpic corrections and compression factor effects on volume-basis calorific values.
- Virial equation of state and methods for estimating second virial coefficients, summation factors and mixture compression factors.
- Quantification of volumetric non-ideality for major natural gas components (including hydrogen, helium and water).
- Effects of water vapour on calorific value (excluded volume, latent heat and compression factor effects).
- Selection and evaluation of methane calorific value data and derived component calorific values (mass- and volume-basis).
- Conversion between reference conditions and metric reference conditions for reporting.
- Uncertainty estimation: principles, sensitivity coefficients, Monte Carlo and finite-difference approaches, and detailed derivation of uncertainty equations corresponding to ISO 6976.
- Miscellaneous data such as atomic weights and composition of dry air relevant to calculations.
Applications and users
ISO/TR 29922:2017 is intended for professionals who implement, verify or extend ISO 6976 calculations, including:
- Natural gas measurement and custody transfer engineers
- Laboratory analysts and calorimetry specialists
- Pipeline operators and gas trading organisations performing energy accounting
- Software developers creating property calculation and billing tools
- Metrologists and uncertainty analysts validating measurement systems
The TR is especially useful when high-accuracy energy determinations, uncertainty analysis or software validation are required.
Related standards
- ISO 6976:2016 - Primary standard for calculation of calorific values, density, relative density and Wobbe index from composition. ISO/TR 29922:2017 provides supporting documentation and technical justification for ISO 6976 methods.
Keywords: natural gas, ISO/TR 29922, ISO 6976, calorific value, enthalpy, compression factor, virial equation, uncertainty, gas measurement.
Open preview (PDF)Natural gas — Supporting information on the calculation of physical properties according to ISO 6976
