A CALORIMETRIC DEVICE FOR THE MEASUREMENT OF TOTAL HEMISPHERICAL EMITTANCE.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OHIO
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Of the many different methods available for measuring total hemispherical emittance, the steady-state calorimetric method is the simplest and, potentially, the most accurate. A steady-state calorimetric device, designed for the measurement of total hemispherical emittance of thin flat disc specimens which are heated by thermal radiation from a hot wall, was evaluated over the emittance range of approximately 0.06 to 0.98. Equations were developed for the calculation of specimen emittance for which only temperatures need to be measured. Also, equations for determining the total heat loss radiation plus conduction through the disc thermocouple wires were developed. Thirteen specimens were evaluated, at temperatures ranging between 0F and 180F, to determine the accuracy of the apparatus. Experimental results, compared to theoretical and reported emittance data, prove the apparatus to be reliable for extremely accurate emittance measurements over the entire emittance range of 0.06 to 0.98. Author