Abstract
Emissivity is a material property that must be measured before an accurate noncontact temperature measurement can be made. We have developed a novel instrument for measuring apparent emissivity under a controlled atmosphere, providing data for applications in radiation thermometry. Our instrument employs a split furnace, a sample-blackbody component, two custom-designed radiometers, and a controlled atmospheric system. We measure across the temperature range from 973 to 1423 K and the spectral range from 0.85 to 1.1 μm; this range is matched to the majority of high-temperature radiation thermometers. The sample and reference approximate blackbody are heated and maintained in the thermal equilibrium, with a temperature difference of better than 1 K at 1423 K. The combined standard uncertainty of the system is lower than 0.0590 (at k = 2) over the whole temperature range. Apparent emissivity of type 304 stainless steel (SS304) was studied under different oxidizing procedures. Nitrogen and compressed air were input into the system to control the oxidization process. We elucidated the relationship between the apparent emissivity variations and the surface composition changes of SS304 during oxidization. This article aims toward accurate and traceable apparent emissivity data, with well-investigated uncertainty, for use in radiation thermometry.
Highlights
M ATERIALS manufactured or processed within hightemperature environments require precise control of temperature to guarantee their quality and to extend their service life [1]–[3]
Accurate knowledge of the emissivity of materials is essential if accurate noncontact temperature measurements are to be made
We presented a novel instrument for the measurement of apparent normal emissivity of target samples over a temperature range of 973–1423 K under a controlled atmospheric environment
Summary
M ATERIALS manufactured or processed within hightemperature environments require precise control of temperature to guarantee their quality and to extend their service life [1]–[3]. Compared to traditional temperature measuring methods, such as the use of thermocouples, radiation thermometers provide a noncontact technique that has a fast response time and wide dynamic range and do not contaminate target objects [4], [5]. When the temperature is computed from the radiant power received by a radiometer, emissivity must be understood for each material [6]. Emissivity is defined as the Manuscript received April 18, 2019; revised July 9, 2019; accepted September 16, 2019.
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