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Solar Technology Laboratory
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Description
Radiation properties are used in heat transfer and energy economizing calculations,
temperature measurements and process control. Because of these reasons they are important
parameters in characterisation and development of heat technical facilities and chemical
reactors. In the case of solar reactors, they play a decisive role in the choice of its
design, its modelling and in the final performance of the entire process. In spite of
this importance, however, radiation properties of the materials currently used in high
temperature applications are known only at moderate temperatures or, at high
temperatures, only for some discrete wavelengths. At PSI a new method has been recently
developed for measuring the spectral reflectivity of condensed samples in the visible and
near infrared range for temperatures up to 3000 K. In the set-up presented, the
directional hemispherical spectral reflectivity is obtained by comparing the optical
response of the sample to a white light, with the response of a reference. The reflected
light, collected by an integrating sphere, is dispersed in a spectrograph and detected by
a CCD camera. Limited by the current detection equipment only the spectral reflectivity
between 510 nm and 860 nm can be measured simultaneously. An electrical resistance heater
is used to heat the samples up to about 1200 K, for higher temperatures a flash-lamp
pumped dye laser is used. To avoid laser induced plasma generation, the integrating
sphere is placed inside a vacuum chamber, which also allows measurements under controlled
atmosphere. The apparatus is calibrated to an absolute scale, which allows the
determination of the sample temperature by fitting the thermal emitted spectrum with
Planck's formula.
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related publications
- S. Eckhoff, I. Alxneit, M. Musella, and H.R. Tschudi, "Determination of
the spectral emittance in the visible spectral range at high temperatures supported by
laser heating", 10th IUPAC Conference on High Temperature Materials
Chemistry,April 10-14 2000, Jülich, Germany
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- S. Eckhoff, I. Alxneit, M. Musella, and H.R. Tschudi, "Development of a
Reflectometer for the Determination of Spectral Emittance in the Visible Range at High
Temperatures", PSI Scientific Report, 5 (2000)
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