An improved apparatus for measuring the spectral directional emissivity in the wavelength range between 1 µm and 20 µm at temperatures up to 2400 K is presented in this paper. As a heating unit an inductor is used to warm up the specimen, as well as the blackbody reference to the specified temperatures. The heating unit is placed in a double-walled vacuum vessel. A defined temperature, as well as a homogenous temperature distribution of the whole surrounding is ensured by a heat transfer fluid flowing through the gap of the double-walled vessel. Additionally, the surrounding is coated with a high-emitting paint and serves as blackbody-like surrounding to ensure defined boundary conditions. For measuring the spectral directional emissivity at different emission angles, a movable mirror is installed in front of the specimen, which can be adjusted by a rotatable arrangement guiding the emitted radiation into the attached FTIR-spectrometer. The setup of the emissivity measurement apparatus (EMMA) and the measurement procedure are introduced, and the derived measurement results are presented. For evaluating the apparatus, measurements were performed on different materials. The determined emissivities agree well with values published in literature within the derived relative uncertainties below 4% for most wavelengths.
The thermal conductivity of low density organic fiber boards has been measured using various guarded hot plate and heat flow meter apparatus. The data are analyzed with a three-flux representation for the radiative heat transfer and compared with extinction results from infrared optical measurements and scattering theory calculations.
The addition of opacifiers in foams considerably reduces the radiative thermal conductivity and consequently enhances the insulation performance of the foams. In this work two different methods were developed to calculate the spectral specific extinction coefficient of opacified extruded polystyrene (XPS) foam material. Cell morphology and thermal conductivity of two identical XPS-foams, one opacified with 3 wt% carbon black as opacifier and one without opacifier, were thoroughly characterized. The experimental results were in a good agreement with the theoretical results obtained from two different computing techniques. These methods allow a good prediction of the specific extinction coefficient of arbitrary opacified foam material.
Abstract. The TIR100-2 emissometer (manufactured by Inglas GmbH & Co.KG) is an emissivity measurement device used by several producers of thermal insulation products for buildings and by some organizations certifying performance of insulation products. A comparison of emissivity measurements on low-emissivity foils involving different measurement techniques, including the TIR100-2 emissometer, gave widely dispersed results; the discrepancies were not explained. The metrological performance of the TIR100-2 emissometer and the uncertainties for measurement on reflective foils was not known, which could be detrimental to users. In order to quantify the performance of TIR100-2 devices for measurement of total near-normal emissivity of low-emissivity foils, the Laboratoire National de Métrologie et d'Essais (LNE) analyzed in detail the measuring principle and listed the associated assumptions and uncertainty sources. A TIR100-2 emissometer actually measures the reflectance and, for opaque materials, the emissivity is calculated from the measured reflectance. The parameters analyzed experimentally are the temperature stability and uniformity of the thermal radiation source, the emissivity of the radiation source, the response function linearity and the spectral sensitivity of the radiometric detection system measuring the reflected radiation, the size of the measurement area, and the measurement repeatability and reproducibility. A detailed uncertainty budget was established. The uncertainty sources taken into account are the uncertainties of the emissivities of the two calibrated standards used for calibration, the stability and uniformity of the radiation source temperature, the non-linearity and the spectral sensitivity of the radiometric detection system, the specific measurement condition related to the radiation source temperature, the uncertainties related to the temperatures of the standards and the sample, the noises on results, and the non-homogeneity in emissivity of the tested material. The combined measurement uncertainty was calculated for different types of reflective foils; the expanded uncertainty is around 0.03 for total near-normal emissivity measurements on smooth low-emissivity foils. A measurement campaign on five types of low-emissivity foils, involving four TIR100-2 emissometers, and a comparison to a primary reference setup at the Physikalisch-Technische Bundesanstalt (PTB) confirmed the uncertainties assessed.
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