High temperature measurements of thermal conductivity for insulation materials

D. Gaal1, R. Fedore1 and M. Thermitus2

1Anter Laboratories, Inc., Pittsburgh PA, USA
2Anter Corporation, Pittsburgh PA, USA

Keywords: insulation, thermal conductivity, slug calorimeter, high temperatures
property: thermal conductivity
material: insulation

Measuring the thermal conductivity of thermal insulations at high temperatures is not an easy task. Instruments following the well known guarded hot plate method are readily available for ambient measurements, less available for temperature ranges up to 500 oC and nonexistent for the operating range up to 1000 oC. Another well known method, the hot - wire, is usable up to 1400 oC, although such instruments are not easy to find, but the specimen needed for such measurements is in most cases very different in size and shape than what is normally found in the insulation industry.

The presently described method is an innovative way of performing thermal conductivity measurements on insulators up to 1000 oC. It involves the use of a large mass of 99 % pure nickel, whose thermophysical properties are known, working as a flux-integrating device. This piece of nickel, also called slug calorimeter, is coming in direct contact with the insulation specimen, which is 150 cm square and 5 - 6 mm thick. The specimen is very slowly heated and the temperatures are monitored continuously on the specimen faces and inside the slug, allowing the heat flux calculations.

Data obtained on an in - house reference material is presented, showing excellent agreement between the guarded hot plate, high temperature hot - wire and slug calorimeter results.

Additionally, thermal conductivity results up to 1000 oC are shown for several insulating materials.

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