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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

EXPERIMENTAL METHOD FOR MEASURING THE SPECTRAL TRANSMITTANCE OF ALUMINA FOAM AT HIGH TEMPERATURES

Get access (open in a dialog) DOI: 10.1615/IHTC16.rti.022518
pages 8253-8261

Résumé

Alumina open-cell foam has been received growing attention in high-temperature and high heat flux applications. Transmittance or reflectance measurements of flat samples are very necessary for various predicting models to determine the thermal volumetric properties. However, the measurement at high-temperature may encounter a series of experimental difficulties. The directional-hemispherical measurements based on an integrating sphere are hardly to be carried out. The highly scattering feature of porous materials makes the directionally optical signal usually very weak. When the sample is heated in an enclosed chamber, the contaminating radiation from high-temperature background makes the detected optical signal even noisy. In this study, an experimental method for measuring the spectral transmittance of the porous alumina foam at high-temperature was proposed. A developed FTIR system coupling with a rigorously designed heating cell was built for the normal-normal transmittance measurements of highly-scattering materials at high-temperature. The systemic instrument function for correcting the systematic error was calibrated and discussed. And thus an improved model for the high-temperature transmittance measurement was deduced in which the stray radiation was carefully considered. Based on the calibrated system, measurements on porous alumina were performed throughout 0.85-6.0 microns from room temperature to 1200 K. In addition, the extinction coefficient was approximately estimated based on the Lambert-Beer's law.