Fast Measuring Device for the Normal Spectral Emissivity in a Broad Temperature Range

Ruirui Tong, Kaihua Zhang, Longfei Li, Bo Zhang, Qin Liu, Yufang Liu, Kun Yu

Abstract: The spectral emissivity, affected by temperature, performs a pivotal role in optimizing the heat treatment process of high-temperature materials and improving energy utilization efficiency. Nevertheless, conducting comprehensive research of the spectral emissivity at elevated temperatures is greatly hindered because of the typical limitation of temperature with relatively low values or narrow ranges and measurement at steady temperatures in most current studies, causing difficulties in meeting the needs of various fields such as aviation and industry. Here, an experimental device is proposed for fast measuring the normal spectral emissivity across a broad temperature range. The device utilizes a custom-built ultrahigh-frequency electromagnetic induction heater to heat the sample. In addition, an optical system with an adjustable detection area is used to modulate the radiation signal, allowing the fiber optic spectrometer with fast response characteristics to swiftly measure the radiation signal covering the desired temperatures. To validate the reliability of the device, the normal spectral emissivity of high-temperature conductive materials, silicon carbide, graphite, and tungsten, is fast measured under dynamic heating conditions, within the temperatures from 873 to 2473 K and the wavelengths from 1000 to 1600 nm. The results exhibit excellent consistency with the data in the literature, and the measurement uncertainty of graphite sample is less than 4%. This work advances the study of normal spectral emissivity over a wide temperature range. Moreover, we provide novel measurement method and technological support for the investigation of normal spectral emissivity of high-temperature conductive materials.