Int J Thermophys (2008) 2λμ445–456 DOI 10.1007/s10765-007-0333-5 ___________________________________________________________________________________ An Improved Application of the Transient Hot-Wire Technique for the Absolute Accurate Measurement of the Thermal Conductivity of Pyroceram 9606 up to 420 K M. J. Assael 1 , K. D. Antoniadis, K. E. Kakosimos, and I. N. Metaxa Thermophysical Properties Laboratory, Chemical Engineering Department, Aristotle University, Thessaloniki 54124, Greece ABSTRACT: This paper describes the final refinements of a novel application of the transient hot-wire technique developed for the absolute, accurate measurements of the thermal conductivity of solids. Although the technique was originally developed five years ago, these new refinements allow a full understanding of the method and hence the performance of measurements with an absolute uncertainty of less than 1%. New measurements of Pyroceram λ606 up to 420 K are reported. The maximum deviation of the present measurements is 0.54%, while their standard deviation at the λ5% confidence level is 0.25%. Since May 2007, Pyroceram λ606 is a European Commission certified thermal conductivity reference material, designated as BCR-724, with an uncertainty of ±6.5% at the λ5% confidence level. Keywordsμ BCR-724; ceramic; pyroceram λ606; solid; thermal conductivity; transient hot- wire. 1. INTRODUCTION Over the last five years in a series of papers [1-4], a novel application of the transient hot-wire technique for the measurement of the thermal conductivity of solids was described. The advantages of the proposed application areμ (a) Contact resistance between wire sensor and solid was minimized, as the wire sensor was placed in a soft silicone paste between two blocks of the solid. At very short times, the generated heat wave is confined to the paste; hence, the properties of the paste can be obtained. Knowing those, at larger times the properties of the solid can be obtained. (b) The method is based on a full theoretical model with equations describing the heat generated in the wire, and the heat transferred in the intermediate layer and the solid. The equations are solved by a finite-element method applied to the exact geometry, over the entire temporal rise of the temperature. ____________________________________________ 1 To whom correspondence should be addressed. E-mailμ assael@auth.gr