Total normal emittance measurements of highly conductive, opaque materials using a solar furnace

ABSTRACT:
This report presents a method for measuring the total normal emittance of a conductive opaque material with and without a selective surface coating and at elevated temperatures. The purpose was to develop a method for measuring surface properties of materials subjected to highly

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concentrated solar flux. A horizontal axis solar furnace was used to heat the samples to temperatures ranging from 373 to 973 K (100° to 700°C), with all tests conducted in air. A Kendell MK-VI radiometer consisting of a cavity-type radiometer and a control unit was used to measure the total normal emittance. The emittance measurements for both copper and aluminum at 373 and 473 K (100° and 200°C) were found to be unreliable because of relatively high drift in the cavity-type radiometer system compared to the emitted energy at these temperatures. However, total normal emittance measurements of these materials at 57 3 K (300°C) and above compare favorably with trends of published data. A Kline-Mcclintock uncertainty analysis was performed with experimental uncertainties of ±10% to 15% of the emittance value obtained.

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