Measurement of Infrared Spectral Directional Hemispherical Reflectance and Emissivity at BNM-LNE

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.

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“…After a few steps, both iterations converge. This static method is realized in different setups, as reported in the literature [7][8][9][10].…”

Section: Conventional Methods To Measure the Spectral Emissivitymentioning

confidence: 99%

“…Several methods have been proposed and applied to measure the emissivity, mostly based on a static measurement principle [5][6][7][8][9][10][11]. These techniques comprise a reference radiation source with a known emissivity and known temperature, which is usually a blackbody with an emissivity close to unity.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2010

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“…The normal spectral emissivities of two samples, made of the same metals as the cavity and the diaphragm and oxidized by heating in air, were measured using the emissometer described in [14]. The quasi-normal spectral emissivities of the surfaces of a heat flux meter were measured using the reflectometer described in [15]. The total hemispherical emissivities of the surfaces were calculated using the results of normal or quasi-normal spectral emissivity measurements.…”

Section: Calculation Of the Irradiancementioning

confidence: 99%

New Vacuum Blackbody Cavity for Heat Flux Meter Calibration

et al. 2008

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In the field of thermal radiation measurements, blackbody cavities are commonly used as reference standards for the calibration of heat flux meters. Applying the energy balance equation to the closed system including the cavity and the sensor, it is possible to predict the heat flux density absorbed by the heat flux meter. Calibration procedures developed at Laboratoire National de Métrologie et d'Essais (LNE) in recent years have allowed us to propose practical solutions for heat flux meters working below 100 kW · m −2 . The best relative uncertainties (k = 2) over the range of (10-100) kW · m −2 vary from 1.7 % to 3 %. During previous studies, three major facilities were constructed, each one with the objective to respond to different technical problems considering the measuring principle of these heat flux sensors. Following this approach, the sensitivity of these meters to radiation, the sensitivity to radiation and convection, and also the influence of the size of the source or of the positioning of the sensor (horizontally, vertically, etc.) have been investigated. As an outcome of this recent experience, a new vacuum blackbody cavity has been set up. As well as the possibility to calibrate at very low irradiance, there are also some substantive improvements in heating, thermal performance, and calibration methodology. After a summary of the state of the art of calibration methods and their limits, the article presents the preliminary results of the characterization obtained with this new facility for which the objective is to reduce the uncertainties by at least a factor of two for heat flux densities lower than 20 kW · m −2 .

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“…The copper alloy cavity was coated with a specific black paint to ensure a high emissivity in the 3-15 µm spectral range. The spectral emissivity of this paint was measured at LNE [5].…”

Section: Short-term Stabilitymentioning

confidence: 99%

Development of a Multiband near-to-far Infrared Radiance COmparator (MIRCO)

et al. 2008

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In recent years, there has been a growing demand to calibrate industrial blackbodies both at short wavelengths for lower temperatures and at long wavelengths for higher temperatures. User requests cover a very wide temperature range, from −20 • C to 1,500 • C in the infrared bands used by thermal cameras or as defined by specific applications (especially the 1-3 µm, 3-5 µm, and 8-12 µm bands). Therefore, LNE (Laboratoire National de Métrologie et d'Essais) has developed a radiance comparator with a mirror-based optical system, an associated set of interference filter wheels, a modular holder for several infrared detectors, and a lock-in amplifier. This setup is designed to be very versatile in terms of wavelength and temperature. Targeted performances have a thermal resolution better than 0.05 • C, and a known and controlled size-of-source effect (SSE). A silicon detector and a visible-to-near infrared integrating sphere were used to assess the stray light inside the housing, and supplementary baffles and stops were used to reduce it to an acceptable level. The investigation included measurement of the SSE for this comparator layout. Then, the performance in the 3-5 µm and 8-12 µm bands, using, respectively, indium antimonide (InSb) and mercury cadmium telluride (MCT) detectors, was evaluated using a water heat-pipe blackbody. This paper describes the modeling and the technical solutions implemented to optimize the optical system. Preliminary results are presented for the short-term stability, the thermal resolution between −20 • C and 960 • C, and also the SSE up to 60 mm in these bands.

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Measurement of Infrared Spectral Directional Hemispherical Reflectance and Emissivity at BNM-LNE

Cited by 30 publications

References 0 publications

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

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

New Vacuum Blackbody Cavity for Heat Flux Meter Calibration

Development of a Multiband near-to-far Infrared Radiance COmparator (MIRCO)

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