A NEW GUARDED HOT-PLATE APPARATUS FOR THERMAL CONDUCTIVITY MEASUREMENTS: VALIDATION RESULTS

This paper presents the work that has been performed for setting up a new apparatus for thermal conductivity measurements. The instrument is based on the guarded hot-plate method and has been designed and realised at the Fisica Tecnica Department of Rome University La Sapienza, with the aim of using it for calibration of commercial heat flow meters. This new apparatus has been realised in accordance with the standard ISO8302:1991 “Thermal insulation – Determination of steady-state thermal resistance and related properties - Guarded hot plate apparatus” and is an asymmetric single-specimen apparatus. The performed tests allowed the verification that the employed technical choices have led to repeatable and reliable measurement results. This new apparatus is characterised by a much lower realisation cost than comparable commercial or research instruments and this has been permitted by the implementation of technical solutions whose effectiveness has been verified in this work. The measurements realised with known-conductivity specimens are quite encouraging: a satisfactory isothermal condition, both for cold and hot plates, has been found and measured conductivity values are in accordance with tested materials certifications.