ISSN Online: 2377-424X
ISBN Print: 978-1-56700-474-8
ISBN Online: 978-1-56700-473-1
International Heat Transfer Conference 16
EXPERIMENTAL METHOD FOR MEASURING THE SPECTRAL TRANSMITTANCE OF ALUMINA FOAM AT HIGH TEMPERATURES
摘要
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.