A Study on the Feasibility of Measuring the Emissivity with the Laser-Flash Method

Abstract

The laser-flash method is a fast, widely used and well established technique to measure the thermal diffusivity. Since its introduction in the 1960s, it was proposed to expand this technique to the measurement of heat capacity and emissivity. Currently, the measurement of spectral emissivity at high temperatures is connected with relatively large uncertainties, although the spectral emissivity is an essential parameter for applications, e.g., in the lamp industry and fusion research. In this work, a theoretical study is presented on the possibility of emissivity measurements using the laser-flash method. Two mathematical approaches are discussed which solve the problem, that a measured temperature rise-necessary to calculate the emissivity-itself depends on the emissivity. It is shown that both methods have a negligible arithmetic error, making them applicable to be used in future work.

Survey of emissivity measurement by radiometric methods

“…The following sensors are applied: bichromate pyroreflectometers [7,47], monochromate and multichromate pyrometers [3,7,15,40,48], and infrared cameras [5,14]. None these sensors affect the measured temperature of the sample, because they are not in contact with the surface.…”

“…This can be resolved by imitation of the laboratory blackbody in the volume of the sample [3,48] [ Fig. 7(a)], or by measurement of the emissivity of the sample surface using a monochromate pyrometer combined with an integrating sphere reflectometer [ Fig.…”

HiTeMS: A Pan-European Project to Solve High Temperature Measurement Problems in Industry

“…The stability of the radiation thermometer, transmission of the optical path (window on the pyrometer) and the surface emissivity are all currently problems in this process. These issues will be tackled by: The establishment of a database of spectral emissivity of materials undergoing laser hardening, at wavelengths between 400 nm to 1100 nm, above 1000°C [16]. Currently there is little information of the effect of laser hardening on the emissivity of these materials and a dataset of such values will facilitate rapid correction of temperature data.…”

Metrology for New Generation Nuclear Power Plants–MetroFission

“…4 presents a scheme of the lamp image furnace designed to heat the specimens up to 1500 in the new high temperature emissometer of LNE. More information about the equipment developed in the framework of this project by PTB and LNE can be found in [18] and [19]. These apparatuses have been validated in their operating temperature ranges by measuring emissivity and thermal diffusivity of two homogeneous materials (tungsten and graphite) [20].…”