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GB/T 47991-2026Thermal insulation - Heat transfer conditions and properties of materials - Vocabulary (English PDF)

绝热传热条件及材料特性术语

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Issued by

State Administration for Market Regulation

Level / Type

National · Recommended

Issue date

July 30, 2026

Implementation date

February 1, 2027

Scope

GB/T 47991-2026 is the English-translated version of 绝热传热条件及材料特性术语.

GB/T 47991-2026 is a Chinese national standard vocabulary for thermal insulation. It adopts ISO 9251:1987, adds a chapter of normative references and also adds an index.

The standard defines the terms used in the field of thermal insulation materials to describe heat transfer conditions and material properties. Its terminology is organised in two main clauses.

The clause on heat transfer conditions includes terms such as steady state, non-steady state, transient state and heat transfer. The clause on material properties includes terms such as porosity.

As a vocabulary, it sets out definitions rather than test methods or product requirements. Issued on 30 July 2026 and applicable from 1 February 2027.

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Document preview — GB/T 47991-2026

National Standard of the People's Republic of China

ICS: 91.120.10
Classification: Q 25

Issued by: State Administration for Market Regulation

Foreword
1 Scope
2 Normative references
3 Heat transfer conditions
4 Material properties

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents".

This document adopts ISO 9251:1987 "Adiabatic heat transfer conditions and material properties - Terminology". This document adds a chapter on "Normative References".

The following minimal editorial changes have been made to this document.

--- An index has been added.

1 Scope

This document defines the terminology used in the field of thermal insulation materials to describe heat transfer conditions and material properties.

2 Normative references

This document has no normative references.

3 Heat transfer conditions

3.1 Steady state

A state in which all parameters remain unchanged over time.

3.2 Non-steadystate

The state of relevant parameters as they change over time.

3.4 Transient state

The relevant parameters gradually evolve from the initial state to a steady state or a periodic unsteady state.

3.5 Heat transfer

Energy transfer is achieved through heat conduction, heat convection, heat radiation, or a combination of the above methods.

4 Material properties

4.1 Porosity

The ratio of the total pore volume to the total volume of the medium in a porous medium.

Note: Porosity can be defined by formula (1). xi=1-[(rho-rho g)/(rho s-rho g)] (1) In the formula. rho --- Apparent density of the medium; rho s --- density of the solid skeleton;

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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 6 pages — is available in the English PDF.

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