HTHP EA HomeIssue Contents

A new setup for the determination of emissivity by a dynamic method
Rudolph Heß, Siegfried Prayer, Peter A Hahn, Ernst Semerad

An apparatus is described which enables the measurement of total emissivity with a dynamic technique at temperatures from 500 °C to 1800 °C and at incident angles from 0° (perpendicular to the sample surface) to 60°. The total emissivity is determined by a comparative method, where the radiation emitted from the surface of the sample is compared to the radiation emitted from a reference blackbody of defined emittance (ε approx 1). The cylindrical samples with a diameter of 15 mm and a thickness of 4 mm to 6 mm are heated by radiation at the bottom of an inductively heated cylindrical graphite cavity, which additionally serves as the reference. Subsequently the samples are lifted to the measurement position, where a thermopile detector and a photodiode sensor are applied to measure the emitted radiation. Specimen temperature is measured via sapphire light-pipe sensors and a blackbody hole in the specimen. The actual surface temperature of the samples is calculated by a one-dimensional time-dependent numerical approach. The measuring process and the data acquisition are fully automated.

Full Text (IP)