Measurement of integral emission coefficients of materials heated to temperatures from 100 to 250 °C

This paper studies the spatial distribution of the integral radiation coefficient (${\epsilon }_T$) of materials heated to temperatures from 100 to 250 °C. The main attention is paid to the variation of this coefficient depending on the angle of incidence of radiation ($\phi$). A special bench was developed for the measurements, which allows to fix ${\epsilon }_{T\phi }$ with high accuracy.

Polished copper surface, ground copper surface, and black ABRO and MOTIP aerosol paints were used as the investigated materials.

The measurement results show that for the polished copper surface, the maximum values of ${\epsilon }_{T\phi }$ are observed at angles of ±10°, after which the coefficient smoothly decreases to a value of 0.3 at angles of ±70°. For polished copper surface ${\epsilon }_{T\phi }$ remains equal to 1 up to angles of ±40^° , then decreases to 0.47 at angles ±70^° . For ABRO and MOTIP aerosol paints, the distribution of ${\epsilon }_{T\phi }$ is similar: at angles up to ±20° the coefficient is 1, then decreases to 0.2 (ABRO) and 0.1 (MOTIP) at angles of ±80^°.