ISO 20765-2-2015 PDF

Full title and description

Natural gas — Calculation of thermodynamic properties — Part 2: Single-phase properties (gas, liquid, and dense fluid) for extended ranges of application. Specifies calculation methods for volumetric and caloric properties of natural gases, manufactured fuel gases and similar mixtures when the mixture is in a homogeneous single phase (gas, liquid or supercritical/dense-fluid) over extended pressure and temperature ranges.

Abstract

ISO 20765-2:2015 defines a computational procedure and related reference equations for obtaining single‑phase thermodynamic properties of natural gas and similar mixtures across extended ranges of temperature and pressure. It provides the basis to calculate volumetric quantities (compressibility factor, density, specific volume) and caloric quantities (enthalpy, internal energy, entropy, heat capacities and related derived properties) for homogeneous gas, liquid and dense‑fluid states suitable for engineering, custody‑transfer and modelling applications.

General information

• Status: Published (active edition).
• Publication date: 15 January 2015 (Edition 1).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 75.060 — Natural gas.
• Edition / version: Edition 1, 2015.
• Number of pages: 60 (ISO edition).

Scope

This part of ISO 20765 specifies a method for calculating volumetric and caloric properties of natural gases, manufactured fuel gases and similar mixtures when the mixture exists as a homogeneous single phase (gas, homogeneous liquid or supercritical/dense fluid). It is intended for extended ranges of temperature and pressure beyond normal pipeline transmission/distribution conditions and is applicable where accurate single‑phase thermodynamic data are required for design, measurement, modelling and process calculations.

Key topics and requirements

• Definition of input variables and compositional representation required to perform calculations (component specification, mole fractions, reference states).
• Use of an equation of state framework (Helmholtz‑energy based formulation) and associated parameter sets appropriate for natural gas mixtures over extended ranges.
• Calculation procedures for volumetric properties: compressibility factor (z), density and specific volume across gas, liquid and dense‑fluid single phases.
• Calculation procedures for caloric properties: ideal and real‑gas enthalpy, internal energy, entropy, and heat capacities (cp, cv) and derived quantities used in energy and process calculations.
• Guidance on ranges of applicability (temperature and pressure limits) and reporting of uncertainty and expected accuracy for different property types and gas qualities.
• Normative equations, required constants and implementation notes sufficient for software implementation and numerical solution (conversion steps, iteration strategies for density/pressure relationships).

Typical use and users

Engineers and technical staff in the gas industry (pipeline operators, transmission and distribution companies), custody transfer and metering groups, gas measurement and analysis laboratories, software developers implementing thermodynamic property libraries, researchers and consultants involved in process design, LNG and gas liquefaction studies, and organisations needing consistent thermophysical property calculations for contracts, billing and design.

Related standards

ISO 20765-1 (gas phase properties for transmission and distribution applications), ISO 20765-5 (calculation of viscosity, Joule‑Thomson coefficient and isentropic exponent), regional adoptions such as EN ISO 20765-2 / DIN EN ISO 20765-2, and other gas‑industry references and EOS developments (for example GERG/industry equation‑of‑state work and AGA/industry reports on property calculation and speed‑of‑sound). Related vocabulary and data format standards (e.g., ISO 14532, ISO 7504) are often used in conjunction with ISO 20765 series publications.

Keywords

natural gas; thermodynamic properties; single‑phase; dense fluid; equation of state; compressibility factor; density; enthalpy; heat capacity; specific volume; property calculation; custody transfer; gas modelling.

FAQ

Q: What is this standard?

A: ISO 20765-2:2015 is an international standard that specifies methods to calculate single‑phase thermodynamic properties (volumetric and caloric) of natural gas and similar mixtures over extended ranges of temperature and pressure.

Q: What does it cover?

A: It covers the computational framework (equations of state and procedures), required inputs, and the formulas needed to obtain properties such as compressibility factor, density, enthalpy, internal energy, entropy and heat capacities for homogeneous gas, liquid and supercritical (dense‑fluid) single phases.

Q: Who typically uses it?

A: Pipeline and transmission engineers, gas measurement and metering specialists, custody transfer personnel, software vendors implementing thermophysical libraries, researchers and consultants in the gas and LNG sectors.

Q: Is it current or superseded?

A: The edition published in January 2015 is the current ISO edition (Edition 1, 2015). National and regional adoptions (EN/DIN/ÖNORM, etc.) exist; users should check national standards bodies for any later confirmations, adoptions or amendments relevant to their jurisdiction.

Q: Is it part of a series?

A: Yes — ISO 20765 is a multi‑part series addressing thermodynamic property calculations for natural gas. Part 1 addresses gas‑phase pipeline applications, Part 2 addresses single‑phase properties over extended ranges, and other parts (for example Part 5) cover additional derived properties; further parts and work items exist within ISO/TC 193 for related property calculations.

Q: What are the key keywords?

A: natural gas, thermodynamic properties, single‑phase, dense fluid, equation of state, compressibility factor, density, enthalpy, heat capacity, property calculation.