Design and development of emissivity measurement test rig using calorimetric method.

Measurement of emissivity is important in various applications like solar heat collectors, temperature measurements and in several research applications. Certain materials require precise knowledge of their total hemispherical emittance and solar absorptance. The emittance of a surface is frequently calculated using indirect spectral bidirectional or directional hemispherical reflection measurements taken at room temperature, which can significantly underestimate the total hemispherical emittance. There are various instruments and techniques available to determine the emissivity of a given surface. The techniques currently available, involve extrapolation and approximation so they are not that accurate when it comes to measurement of emissivity for high temperature applications. The total hemispherical emittance of surfaces at high temperatures is directly measured in the present article using a straightforward steady-state calorimetric approach with a maximum experimental error (uncertainty) of 5%. For emissivity measurement a test setup using calorimetric method is designed and developed. High temperature emissivity within the temperature range of 200 ℃ to 500 ℃ were determined. The calculated emissivities are found to be accurate and within the range of ±0.04 when compared to the theoretically determined values. [ABSTRACT FROM AUTHOR]