IIntercomparison of Insulation Thermal Conductivities Measured by Various Methods

In the present contribution, systematic effective thermal-conductivity measurements with different methods are reported for various materials. One of the materials studied, calcium silicate, is isotropic; the other two, alumino-silicate and alumina fiber mats, are non-isotropic. The measurements were carried out with two different steady-state panel test apparatus (according to ASTM C201, designed and constructed by authors), two guarded hot-plate apparatus (ISO 8302, with either one or two samples), one steady-state radial heat flow apparatus (designed by authors), and one transient hot-wire instrument (DIN EN 993-14). These apparatus are operated at ambient pressure and atmosphere (air) between 20 and 1,650◦C, and are briefly described in the article. The results show the well-known increase of effective conductivity with temperature, mainly due to radiation heat transfer. For the case of the isotropic calcium silicate material (bulk density of 220 kgm−3), no significant differences between the various methods have been found and the results can easily be correlated within ±10%. The fiber-mat results, however, show additional effects of the density (between 103 and 170 kgm−3) and the fiber orientation. Large differences exceeding 30% are found between plate and hot-wire results.