Star-shape comparisons of high temperature thermal conductivity measurement standards for insulation from 150 °C up to 650 °C

Thermal insulation materials are essential for protecting plant or processes from high temperatures which is important in industries from steel, glass and petrochemical production to air transport. For example, in the petrochemicals sector, European refineries could increase turnover by €3.5 billion/year through using improved insulation.
Advanced thermal insulators are thinner, stronger and lighter than more conventional products, but these require rigorous characterisation before plant designers can use them. Accurate measurements with robust links to SI units are required for testing at higher temperatures than is currently possible in order to produce reliable the reliable and comparable thermal performance specifications that underpin the use of industrial thermal insulation.

This project investigated the commonly used “guarded hot plate” method for determining thermal conductivity, extending its traceability to 650 ˚C.

The Project:

Investigated the performance of materials and sensors used in high-temperature guarded hot plates in order to gain an understanding of usage requirements for use to 850 ˚C
Investigated and reduced significant measurement errors due to sample distortion caused by sample bowing during testing, by modelling hot plate-sample interactions
Characterised high-density calcium silicate for use as the first reliable high temperature insulation reference material
Demonstrated improved measurement agreement between the project partners and a major industrial test lab with greater accuracy than was previously possible. This established robust links between the SI units and industrial testing labs for the first time.

This project has successfully enabled European National Measurement Institutes (NMIs) to improve the accuracy and SI traceability of thermal conductivity measurements, and to extend their testing capabilities to higher temperatures. By proposing changes to measurement procedures, the project has been able to reduce the effects of common sources of measurement result variation leading to greater uniformity in the insulation test data that is produced in different laboratories. Rolling out improved measurement accuracy to industrial testing labs via accreditation schemes supports user confidence in the performance certificates required to underpin the insulation product data sheets and the awarding of the CE quality mark.
The optimal use of thermal insulation in industrial engineering will provide benefits such as improved structural integrity, greater safety, and greater energy efficiency coupled with reduced CO2 emission. As a result of this project, more accurate characterisation of thermal insulations will give designers and engineers increased confidence when choosing appropriate insulation materials in order to meet product or plant design specifications.

Subjects
Thermometry (T)
Coordinator
Jiyu Wu (NPL)
Coordinating Institute
NPL (United Kingdom)
Further Partners
Forschungsinstitut für Wärmeschutz e.V. München (Germany)