Abstract

This paper complements the existing measurement standards and literature for High-Temperature Guarded Hot-Plates (HTGHPs) by addressing specific issues relating to thermal conductivity measurements of technical insulation at high temperatures, with examples focusing on the designs for measuring thin insulation. The sensitivity studies include the effect of temperature measurements, plate flatness and centre-guard gap design and imbalance. A new configuration of centre-guard gap with triangular shape cross-section has been optimised to obtain the same thermal resistance across the gap as the 2-mm wide gap with rectangular shape cross-section that has been used in the HTGPHs at NPL and LNE. Recommendations haven been made on the selections of heater plate materials, high-temperature high-emissivity coatings and miniature temperature sensors. For the first time, thermal stress analysis method has been applied to the field of HTGHPs, in order to estimate the effect of differential thermal expansion on the flatness of thin rigid specimens.

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